UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 Advanced PWM Controller for Bus Converters FEATURES 1 * * * * * * * * * * * * * Programmable, Load Depended Off Time Control Frequency Controlled Start Up Allows Small Output Inductor, Low Ripple and Constant Current Start with Large Output Capacitor Two 0.2-A Push-Pull Outputs Provide Matched Control Signals D to External Drivers Two Additional 1- D Outputs for Optimal Use of Self-Driven or Control Driven Synchronous Rectifiers Unregulated, Fixed Volt-Second or Fixed Frequency Modes set by User Two, 1.5% Overall Accuracy Reference Voltage Options: 5-V for UCC28230 and 3.3-V for UCC28231 Resistor Programmable Switching Frequency up to 1 MHz Cycle-by-Cycle Current Limit Allows Parallel Operation with Droop Based Current Sharing Single External Capacitor sets Soft-Start and Over Current Hiccup Mode Parameters with Restart Severe Short Circuit Hiccup with Restart or Latch Off Protection Option by External Resistor Input Under Voltage Lock Out Thermal Shutdown Thermally Enhanced 3 mm x 2 mm SON-12 and TSSOP-14 Package Options APPLICATIONS * * Intermediate Bus Isolated Converters DC-to-DC Transformers DESCRIPTION The UCC28230, UCC28231 PWM bus controllers are optimized for use in high efficiency, high power density, unregulated intermediate bus converters. Topologies include push-pull, half-bridge and full-bridge. External drivers, such as the UCC27200 120-V high-side/low-side drivers, can be used with this controller. Low cost, small size and highly efficient solutions are provided by innovations such as: * Start-up frequency control circuit allowing small output inductor and the ability to start with large intermediate bus capacitor. * Load depended off-time control set by user. Additional 1-D control outputs can be used for primary winding clamping in self-driven output synchronous rectifier applications or as drive signals for the control-driven synchronous rectifier. Cycle-by-cycle current limit prevents overstresses of converter. If the over current condition causes less than 80% duty cycle at the output, then after a programmed time the controller proceeds into periodical shutdown and restart hiccup mode. The UCC28230 provides 5 V, and the UCC28231 provides 3.3-V precision reference voltages with 1.5% overall accuracy and 10-mA output current. This reference voltage can be used to supply housekeeping circuit and/or microcontroller. The precision reference voltage can also be used for accurate setting of system parameters. Other features include under-voltage lockout, thermal shut down, programmable soft start, over-current hiccup mode and short circuit protection with internal restart by default that can be set into latch-off mode by an external resistor. 1 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright (c) 2008, Texas Instruments Incorporated UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com TYPICAL APPLICATION DIAGRAMS + Vbias UCC 27200 Vbias UCC 27200 VDD VDD HB HB Vin 36 V to60V HI CT HO LI HI HO HS HS LO LO LI VSS VSS _ + Vout 7 V to12 V 400W _ Bias Power Supply Vbias VDD VDD UVLO Comp. VDD Thermal Shutdown 12 Interface with System OS Off Time Control Circuit 3 R3 R2 2 OST CS O1_ DIN 10 Short Circuit Shutdown O2_ DIN 8 6 Is 4 11 O2_D Oscillator & Start Up Frequency Control RT O1_D Logic Block Cycle by - Cycle Current Limit Vin Reference Generator 5V/3.3V LDO 1 R1 Housekeeping Micro Controller VDD 6.3 V rise 5.7 V fall VREF Vcc =5 V or 3.3V EN 9 CLK Soft Start & Hiccup Current Limit Circuit GND 7 5 SS Figure 1. Full-Bridge Bus Converter + UCC 27200 Vbias VDD HB Vin 36V to 60V CT HO HI HS LI LO VSS + _ Vout 7V to 12V 200W Bias Power Supply _ Vbias UCC28230/1 VDD V DD UVLO Comp. 12 Vcc =5V or 3.3V Interface with System EN 6.3 V rise 5.7 V fall VREF OS Off Time Control Circuit 3 R3 Houskeeping MicroController R2 2 OST CS VDD VDD 6 Short Circuit Shutdown O2_ DIN Is 4 2 7 4 5 OUTB INB 3 Logic Block Cycle by - Cycle Current Limit RT OUTA INA 10 8 6 Vin Reference Generator O1_ DIN 5V/3.3V LDO 1 R1 Vbias VDD Thermal Shutdown Oscillator & Start Up Frequency Control O1_D GND 11 UCC27324 O2_D 9 CLK Soft Start & Hiccup Current Limit Circuit GND 7 5 SS Figure 2. Half-Bridge Bus Converter with Control-Driven Synchronous Rectifier 2 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 PINOUT CONFIGURATION ORDERING INFORMATION (1) TEMPERATURE RANGE, TA = TJ REFERENCE VOLTAGE TAPE and REEL QTY .250 UCC28230DRNT 5V 3000 UCC28230DRNR Plastic 12-pin SON (DRN) 250 UCC28231DRNT 3.3 V 3000 UCC28231DRNR 5V 250 UCC28230PW 2000 UCC28230PWR 5V 3.3 V Plastic 14-pin TSSOP (PW) 3.3 V (1) (2) PART NUMBER 5V 3.3 V -55C to +125C PACKAGE (2) 250 UCC28231PW 2000 UCC28231PWR The 12-pin SON (DRN) and 14-pin TSSOP packages use Pb-Free lead finish of Pd-Ni-Au which is compatible with MSL level 1 at 255-260C peak reflow temperature to be compatible with either lead free or Sn/Pb soldering operations. The pad underneath the center of the IC is a thermal substrate. The PCB "thermal land" design for this exposed die pad should include thermal vias that drop down and connect to one or more buried copper plane(s). This combination of vias for vertical heat escape and buried planes for heat spreading allows the DRN to achieve its full thermal potential. This pad is also internally connected to GND pin. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 3 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range (1) (2) (unless otherwise noted) PARAMETER VDD (3) VALUE Input supply voltage range O1_D, O2_D, O1_DIN, O2_DIN HBM CDM UNIT -0.3 to 20.0 -0.3 to VDD +0.3 Inputs voltages on OS, CS, SS, RT, OST -0.3 to 6.3 Output voltage on VREF -0.3 to 5.6 V 2k ESD rating 500 Continuous total power dissipation See Dissipation Rating Table TJ Operating virtual junction temperature range -55 to +150 TA Operating ambient temperature range -55 to +125 Tstg Storage Temperature -65 to +150 Lead Temperature (Soldering, 10 sec.) PW Package (1) (2) (3) C +300 Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. These devices are sensitive to electrostatic discharge; follow proper device handling procedures. All voltages are with respect to GND unless otherwise noted. Currents are positive into, negative out of the specified terminal. See Packaging Section of the datasheet for thermal limitations and considerations of packages. DISSIPATION RATINGS (1) BOARD PACKAGE High-K (2) DRN JC (C/W) JUNCTION TO CASE PW (1) (2) 2.71 JA (C/W) JUNCTION TO AMBIENT JP (C/W) JUNCTION TO PAD JB (C/W) JUNCTION TO BOARD 70.66 15 37.66 97.65 2.07 These thermal data are taken at standard JEDEC test conditions and are useful for the thermal performance comparison of different packages. The cooling condition and thermal impedance RJA of practical design is specific. The JEDEC test board JESD51-5 with direct thermal pad attach, 3-inch x 3-inch, 4-layer with 1-oz internal power and ground planes and 2-oz top and bottom trace layers (preliminary data based on modeling) RECOMMENDED OPERATING CONDITIONS MIN VDD Supply voltage range Operating junction temperature range 4 NOM 7 Submit Documentation Feedback -55 12 MAX UNIT 17 V 125 C Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ELECTRICAL CHARACTERISTICS (1) VDD = 12V, 1-F capacitor from VDD and VREF to GND, TA = TJ = -55C to 125C, RT = 49.9 k connected to 4.4V supply to set Fsw = 100 kHz (unless otherwise noted). PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Supply Currents IDDD(off) Startup current IDD Operating supply current VDD = 5.2 V 150 200 A 1.5 2.5 mA 6.9 Under Voltage Lockout Start threshold 5.9 6.3 Minimum operating voltage after start 5.3 5.7 6.2 0.55 0.6 0.75 Hysteresis V Soft Start (SS PIN, Figure 41, Figure 44) ISS Charge current VSS_STD Shutdown/restart/reset threshold VSS_FP Soft-start first pulse threshold VSS_PU Pull up threshold VSS_CL Clamp voltage VSS = 0 V -30 -25 -20 0.3 0.55 0.68 0.68 0.85 1.1 3.3 3.5 3.8 4.3 4.5 4.8 A V Off-Time Programming (Figure 33) TOFF5 Off time between O1_D and O2_D UCC28230 32 40 50 TOFF3 Off time between O1_D and O2_D UCC28231 30 40 53 TDT Dead time between O1_D, O1_DIN and O2_D, O2_DIN 10 16 TOFF Off time matching TOFFR5 Off time between O1_D and O2_D UCC28230 32 40 50 TOFFR3 Off time between O1_D and O2_D UCC28231 30 40 53 TDTREF Dead time between O1_D, O1_DIN and O2_D, O2_DIN 10 16 TOFFR Off time matching IHYST Hysteresis current source TOFFMAX Maximum off time at low CS OS = 8.45 k, CS = 0.3 V, OST = 1 V 2 OS = 8.45 k, CS = 0 V, OST = VREF ns 2 A 10 OS = 8.45 k, OST = 1 V, CS = CSTH- 0.03 V 165 235 ns Switching Frequency at O1_D and O2_D Outputs FSWNOM Nominal frequency VSS = 4 V FSWMAX Maximum frequency VSS = 1.8 V 92 100 108 425 550 675 4.925 5 5.075 3.25 3.3 3.35 -35 -25 -12 kHz VREF Output Voltage VREF5 VREF3 ISCC (1) VREF total output range Short circuit current UCC28230 UCC28231 0 IR 10 mA; VDD = from 7 V to 17 V, -55C TJ 125C VREF = 0 V V mA Typical values for TA = 25C Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 5 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com ELECTRICAL CHARACTERISTICS (continued) VDD = 12V, 1-F capacitor from VDD and VREF to GND, TA = TJ = -55C to 125C, RT = 49.9 k connected to 4.4V supply to set Fsw = 100 kHz (unless otherwise noted). PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 0.515 V Current Sense, Cycle-by-Cycle Current Limit With Hiccup, Short Circuit Protection With Latch Off VCS_LIM CS pin cycle-by-cycle threshold 0.48 0.5 TCS CS to O1_D and O2_D propagation delay Input pulse at CS from 0.3 V to 0.6 V with 0.03 V/ns slew rate TBL Leading edge blanking time by internal filter Input pulse at CS from 0.3 V to 0.6 V with 0.03 V/ns slew rate IDS Discharge current to set cycle-by-cycle current limit duration CS = 0.6 V, VSS = 4 V (Figure 41) 15 20 25 A Hiccup OFF time threshold 3.1 3.4 3.7 V IHCC Discharge current to set Hiccup Mode OFF Time (Figure 41, Figure 44) 1.9 2.5 3.1 A VCS_SC CS pin short circuit protection threshold (Figure 44) 0.65 0.7 0.75 V 100 50 ns Outputs O1_D, O2_D, O1_DIN, O2_DIN Sink/Source peak current (2) 0.2 A Rise time CLOAD = 100 pF 12 25 Fall time CLOAD = 100 pF 10 25 RSRC Output source resistance IOUT = 20 mA 10 20 35 RSINK Output sink resistance IOUT = 20 mA 5 15 30 Duty cycle matching Pins 7 and 9 pulses matching at FSW = 100 kHz 35 ns ns Thermal Shutdown Rising threshold (3) 150 160 170 Falling threshold (3) 130 140 150 Hysteresis (2) (3) 6 C 20 Output sink/source peak current value, defined by equation IP = 100 pF x dV/dt where dV/dt is taken from the output rise and fall switching waveforms. It is not tested in production. Characterization is available upon request. Thermal shutdown is not tested in production. Characterization is available upon request Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 FUNCTIONAL BLOCK DIAGRAMS VDD Thermal Shutdown UVLO Comp. VDD VDD 12 EN VDD 6.3V rise 5.7V fall VREF 5V/3.3V LDO 1 OS R1 Off Time Control Circuit 3 R3 2 R2 Reference Generator OST CS O1_DIN 10 Short Circuit Shutdown O2_DIN 8 Is 6 CT Oscillator & Start Up Frequency Control Vin RT 4 O1_D Logic Block Cycle-byCycle Current Limit 11 O2_D 9 CLK Soft Start & Hiccup Current Limit Circuit GND 7 5 SS Figure 3. SON-12 Package VDD VDD VDD Thermal Shutdown UVLO Comp. 14 EN VDD 6.3V rise 5.7V fall VREF 5V/3.3V LDO 1 R1 OS R3 R2 Off Time Control Circuit 3 2 OST CS Reference Generator O1_DIN 12 Short Circuit Shutdown O2_DIN 10 7 CT Is Logic Block Cycle-byCycle Current Limit NC O2_D 4 Vin RT 5 AGND Oscillator & Start Up Frequency Control O1_D 13 11 CLK Soft Start & Hiccup Current Limit Circuit GND 9 8 6 SS Figure 4. TSSOP-14 Package Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 7 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com TERMINAL FUNCTIONS TERMINAL DFN-12 TSSOP-14 PIN# PIN# 8 NAME I/O FUNCTION 1 1 VREF O 1.5% accurate 5 V for UCC28230 and 3.3 V for UCC28231, 10-mA output reference voltage with short circuit protection that can be used for fixed switching frequency setting and/or for housekeeping microcontroller. Place decoupling capacitor in 1 F to 2.2 F range from this pin to GND. 2 2 OST I Off time control threshold pin uses a resistor divider to set current level as percentage of current limit threshold. 3 3 OS I Nominal off time TOFF and dead time TDT set pin. An external resistor connected between this pin and GND sets the dead time and nominal off time. 4 NC 4 5 RT 5 6 SS 6 7 CS 8 AGND Not connected pin, TSSOP-14 only. I Oscillator timing input pin. The external resistor which is connected between this pin and VIN sets the oscillator frequency which varies with VIN. Tying the external resistor to VREF sets fixed frequency operation independent of VIN. Input to adjustable soft-start,and hiccup mode circuit. Place soft-start capacitor from this pin to I/O GND. The internal charge/discharge current ISS and an external capacitor value set the soft-start timing, duration of cycle-by-cycle current limit and controller turn-off time for hiccup mode operation. I Current sensing pin used for cycle-by-cycle current limit, short circuit protection and off time control. Analog ground, TSSOP-14 only. 7 9 GND 8 10 O2_DIN O Ground pin connected to thermal pad. All signals are referenced to this node. 0.2-A sink/source switching output pin to an external driver providing 1-D pulse. 9 11 O2_D O 0.2-A sink/source switching output pin to an external driver providing D pulse. 10 12 O1_DIN O 0.2-A sink/source switching output pin to an external driver providing 1-D pulse. 11 13 O1_D O 0.2-A sink/source switching output pin to an external driver providing D pulse. 12 14 VDD I Connect this pin to a 7-V to 17-V bias supply. Place a high quality at least 1-F ceramic bypass capacitor from this pin to GND. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 TYPICAL CHARACTERISTICS Start-up Current IDDoff Operating Supply Current IDD over Temperature at VDD=5.2V over Temperature at FSW=100kHz 1.60 165 160 1.55 I DD, mA IDDoff,, A 155 150 1.50 145 1.45 140 135 -55 -35 -15 5 25 45 65 85 105 1.40 -55 125 -35 -15 5 25 45 65 85 105 125 85 105 125 TJ-temperature, C TJ-temperature, C Figure 5. Figure 6. Under Voltage Lockout Hysteresis over Temperature Under Voltage Lockout Thresholds over Temperature 0.70 6.7 0.68 6.3 UVLO Hysteresis, V UVLO Thresholds, V 6.5 6.1 5.9 5.7 5.5 5.3 -55 -35 -15 5 25 45 65 85 105 125 0.64 0.62 -55 TJ-temperature, C Rising threshold 0.66 -35 -15 5 25 45 65 TJ-temperature, C Falling threshold Figure 7. Figure 8. Soft Start Shutdown VSS_STD and First Pulse VSS_FP Thresholds over Temperature Soft Start Pull-up VSS_PU and Clamp Voltage VSS_CL Thresholds over Temperature 1.00 5.00 V SS_PU , V SS_CL , V V SS_STD , V SS_FP , V 0.90 0.80 0.70 0.60 0.50 4.50 4.00 3.50 0.40 0.30 -55 -35 -15 5 25 45 65 85 105 125 3.00 -55 -35 5 25 45 65 85 105 125 TJ-temperature, C TJ-temperature, C Soft Start Shutdown -15 First Pulse Threshold Figure 9. Pull-up Threshold Clamp Voltage Figure 10. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 9 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com TYPICAL CHARACTERISTICS (continued) Off Time Matching TOFF Soft-Start Charge Current ISS over Temperature over Temperature 25.20 4.00 25.15 25.10 3.50 25.00 3.00 TOFF , ns Iss, A 25.05 24.95 24.90 24.85 24.80 -55 -35 -15 5 25 45 65 85 105 2.50 2.00 125 TJ-temperature, C 1.50 1.00 -55 -35 -15 5 25 45 65 85 105 125 TJ - temperature, C Figure 11. Figure 12. UCC28231 Off Time T OFF and Dead Time T DT over Temperature UCC28230 Off Time TOFF and Dead Time TDT over Temperature 50 50 40 TOFF , TDT , ns TOFF , T DT , ns 40 30 30 20 20 10 -55 -35 -15 5 25 45 65 85 105 10 -55 125 -35 -15 Off Time 5 25 45 65 85 105 125 105 125 TJ - temperature, C TJ - temperature, C Dead Time Off Time Figure 13. Dead Time Figure 14. Maximum Off Time TOFFMAX at Low VCS over Temperature Nominal Switching Frequency FSWNOM over Temperature 220.00 101.00 210.00 F SWNOM , kHz TOFFMAX , ns 100.50 200.00 190.00 99.50 180.00 170.00 -55 10 100.00 -35 -15 5 25 45 65 85 105 125 99.00 -55 -35 -15 5 25 45 65 TJ - temperature, C TJ - temperature, C Figure 15. Figure 16. Submit Documentation Feedback 85 Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 TYPICAL CHARACTERISTICS (continued) Cycle-by-Cycle Current Limit Threshold over Temperature Maximum Switching Frequency FSWMAX over Temperature 0.55 550.00 0.53 V CS_LIM , V F SWMAX , kHz 540.00 530.00 520.00 0.51 0.49 0.47 510.00 500.00 -55 -35 -15 5 25 45 65 85 105 0.45 -55 125 -35 -15 5 25 TJ - temperature, C 45 65 85 105 125 TJ-temperature, C Figure 17. Figure 18. UCC28231 Reference Voltage at V DD=12V over Tem perature and Load Current UCC28230 Reference Voltage at V DD=12V over Tem perature and Load Current 5. 015 3. 305 VREF, V VREF, V 5. 005 4. 995 3. 295 3. 285 4. 985 3. 275 4. 975 -55 -35 -15 5 25 45 65 85 105 -55 125 -35 -15 Iload=1mA Iload=10mA Iload=10uA 45 65 85 Iload=1mA Figure 19. 105 125 Iload=10mA Figure 20. UCC28230 Reference Voltage at ILOAD=1m A over Tem perature and Supply Voltage V DD UCC28231 Reference Voltage at ILOAD=1m A over Tem perature and Supply Voltage V DD 3. 306 5.006 3. 302 VREF, V 5.002 VREF, V 25 TJ - tem perature, C TJ - tem perature, C Iload=10uA 5 4.998 3. 298 3. 294 4.994 4.990 3. 290 -55 -35 -15 5 25 45 65 85 105 125 -55 -35 -15 Vdd=7V Vdd=12V 5 25 45 65 85 105 125 TJ - tem perature, C TJ - tem perature, C Vdd=17V Vdd=7V Figure 21. Vdd=12V Vdd=17V Figure 22. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 11 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com TYPICAL CHARACTERISTICS (continued) Output Source Resistance RSRC and Sink Resistance Current Sense Propogation Delay TCS RSINK over Temperature over Temperature 30.0 115.00 25.0 R SCR , R SINK , O TCS , ns 110.00 105.00 100.00 20.0 15.0 95.00 90.00 -55 10.0 -55 -35 -15 5 25 45 65 85 105 TJ - temperature, C 12 -35 -15 125 5 25 45 65 85 105 125 TJ - temperature, C Source Resistance Sink Resistance Figure 23. Figure 24. Figure 25. O1_D and O2_D Duty Cycle Matching at VCS = 0.14 V and VOST = 1 V Figure 26. O1_D and O2_D Duty cycle Matching at VCS = 0.0 V and VOST = 1 V Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 TYPICAL CHARACTERISTICS (continued) Figure 27. Output Waveforms During First Half Switching Cycle at VCS = 0.14 V and VOST = 1 V Figure 28. Output Waveforms During Second Half Switching Cycle at VCS = 0.14 V and VOST = 1 V Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 13 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com TYPICAL CHARACTERISTICS (continued) Figure 29. Output Waveforms During First Half Switching Cycle at VCS = 0 V and VOST = 1 V Figure 30. Output Waveforms During Second Half Switching Cycle at VCS = 0 V and VOST = 1 V 14 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 DETAILED DESCRIPTION Start-Up Protection Logic Before the controller allows the start up, the following conditions must be met: * VDD voltage exceeds rising UVLO threshold 6.3 V typical * The reference voltage 5 V for UCC28230 or 3.3 V for UCC28231 is available * Junction temperature is below the thermal shutdown threshold 130C min * The voltage at soft-start capacitor is not below 0.55 V typical If all those conditions are met, an internal enable signal EN is generated that initiates the soft start process. The duty cycle during the soft start is defined by the voltage at the SS pin or by cycle-by-cycle current limit circuit depending on load conditions. Internal Oscillator and Converter Switching Frequency The oscillator frequency is set by an external resistor at RT pin (see Figure 3 and Figure 4). The oscillator frequency FOSC is twice that of converter switching frequency FSW. The oscillator performs the following main functions: * Generates clock signal CLK to synchronize internal functional blocks * By changing the switching frequency during the start up and cycle-by-cycle current limit, the oscillator limits the current ripple at the output inductor allowing the use of small output inductor and start with large output capacitor Oscillator can operate in the following modes: * Fixed volt-second mode of operation when the resistor RT is connected between VIN and RT pin. In this mode the switching frequency increases in accordance to an input voltage rise * Fixed switching frequency mode when the resistor RT is connected between VREF and RT pins. The switching frequency of converter is defined as FSW(nom) = 1/TSW(nom) (see Figure 33). Equation 1 is used to calculate the nominal switching frequency of the converter and its transformer. FSW ( nom ) = 1 RT + 1.2 TOFF 2500 (VIN - 2.4 ) (1) Where RT is in k, VIN is in volts, TOFF is in ms and FSW(nom) is in kHz. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 15 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com In most applications, TOFF is set at about 40~50 ns, which can be neglected compared to the total oscillator period. Therefore Equation 1 can be simplified as: FSW ( nom ) = 2500 (VIN - 2.4 ) RT (2) In this equation RT is in k, VIN is in volts and FSW(nom) is in kHz. Figure 31 shows how the nominal switching frequency of converter depends on value of resistor RT, and Figure 32 shows how the switching frequency changes over the input voltage range in case of fixed volt-second mode of operation. The TOFF is set to 40 ns for both figures. 800 1,000 900 700 (kHz) 700 Switching Frequency Switching Frequency (kHz) 800 600 500 400 300 600 500 400 300 200 200 100 100 0 100 0 300 500 700 900 1100 36 40 44 Vin=36V Vin=48V 48 52 56 60 Vin Voltage (V) RT Resistance (kO) Vin=60V Figure 31. Nominal Switching Frequency of Converter vs Resistor RT RT=200kohm RT=400kohm RT=1,100kohm Figure 32. Switching Frequency Variation Over the Input Voltage for Fixed Volt-Second Mode of Operation Fixed frequency mode of operation can be achieved by connecting the resistor RT between VREF and RT pins. In such case the switching frequency is defined by the following Equation 3, where the impact of TOFF is neglected as well. FSW ( nom ) = 2500 (VREF - 2.4 ) RT (3) In this equation the RT is in k, VREF is in volts and FSW(nom) is in kHz. 16 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 Output Signals The UCC28230/1 has two push-pull outputs O1_D and O2_D that provide D pulse signals to external drivers. The additional two outputs O1_DIN and O2_DIN provide 1-D output pulses with dead time between D and 1-D pulses to avoid shoot-through currents. Such combination of outputs allows use of UCC28230/1 either with self-driven synchronous rectifier, or with the control-driven synchronous rectifier in push-pull, half-bridge or full-bridge configuration. For the full-bridge self-driven rectifier configuration, outputs O1_D and O2_D control high-side MOSFETs while outputs O1_DIN and O2_DIN control low-side MOSFETs thus shorting the primary winding during (1-D) switching cycle. This avoids number of issues related to self-driven rectification such as start up disabling, reverse current during parallel operation, tendency to oscillate during low duty cycles. The applications circuit for this configuration is shown on Figure 1 and the output signal timing diagrams are shown in Figure 33. TOFF O1_D O2_D TOFF TOFF TOFF TOUT_D TDT TDT TSWNOM O1_DIN TDT TDT O2_DIN TCLAMP TCLAMP TCLAMP TCLAMP Figure 33. D and (1-D) Output Pulses Providing Dead Time TDT in Each Leg and the Off Time TOFF Between Upper FETs That Includes Some Overlapping Time TCLAMP. In the steady state condition an unregulated bus converter operates at maximum duty cycle thus having minimum overlapping TCLAMP of (1-D) outputs. During start up or cycle-by-cycle current limit, the duty cycle can be very low, so (1-D) output pulses occupy most of the switching cycle time. This provides zero voltage clamping of the transformer's primary winding. The UCC28230/1 also includes an off-time control feature. This feature allows user to increase off time TOFF when the converter output current is below a programmable current threshold. This feature reduces switching losses of the synchronous rectifier at light load and it is described in detail in Offtime Control Circuit section. For the control driven half-bridge topology, the outputs O1_D and O2_D provide control pulses for the high-side and low-side MOSFETs, while the outputs O1_DIN and O2_DIN can be used to drive the pulse transformers providing control signals to the secondary-side MOSFET rectifiers as shown in Figure 2. In case of full-bridge topology with the control-driven rectifier, the outputs O1_DIN and O2_DIN are used to control primary low-side MOSFETs as well as the secondary-side rectifier MOSFETs. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 17 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com Start-Up Frequency Control Circuit The start-up frequency control circuit addresses the need for bus converter to start at heavy load with a large output capacitance. In the steady state condition bus converters operate with the minimum off time and as the result, the output inductor current ripple is low. Therefore the output inductor value is able to be selected very low to save the size and cost. During over current or soft start condition the duty cycle is controlled by the cycle-by-cycle current limit circuit or by the voltage at soft-start capacitor. In this condition, the duty cycle D for the output inductor can be anywhere between 0 and 1 causing significant output inductor current ripple that reaches its maximum at duty cycle D = 0.5. The current limit circuit on primary side limits the peak current, not the average current. The limiting of peak current with a large ripple causes the fold back characteristic of converter output, which prevents the converter from ever reaching its nominal steady state output voltage. The output inductor duty cycle is a ratio of output pulses TOUT_D at pins O1_D and O2_D to the half of switching cycle TSW(nom), i.e. TOUT_D +TOFF (see Figure 33): D= TOUT _ D TOUT _ D + TOFF (4) The start-up frequency control circuit changes the switching frequency during the start up or during the cycle-by-cycle current limit to maintain the output inductor current ripple almost constant at any duty cycle D. This allows an additional cost and size saving because the output inductor can be selected based on steady state condition rather than the transient condition, which dictates significantly larger inductance value and size. Examples of switching frequency changes over duty cycle variation for the selected nominal frequencies 100 kHz and 450 kHz are shown in Figure 34. The plots are given for the nominal off time at 53 ns and 77 ns (right column) and for no load off time at 196 ns, 209 ns accordingly. It is shown that the impact of nominal off time on switching frequency is minimal. However the no load off time causes visible frequency reduction especially at maximum frequency when the duty cycle D is around 0.5. Switching Frequency Plots vs Duty Cycle for FSW(nom) Set at 100 kHz and 450 kHz at Different No Load and Nominal TOFF Time Sets. Fsw vs Duty Cycle, RT=1M tied to Vin, Vost=1V, R3(OS)=15k, Toff=196ns, Vcs=0V 900 800 800 700 Fsw, kHz 900 700 Fsw, Fsw vs Duty Cycle, RT=1M tied to Vin, Vost=1V, R3(OS)=15k, Toff=53ns, Vcs=0.4V 600 500 600 500 400 300 200 400 100 300 0 200 0 10 20 30 100 40 50 60 70 80 90 100 Duty Cycle, % 0 Vin=48V 0 10 20 30 40 50 60 70 80 90 Vin=36V Vin=72V Vin=48V, RT=287K 100 Duty Cycle, % Vin=48V Vin=36V Vin=72V Vin=48V, RT=287K Figure 34. 18 Figure 35. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 Fsw vs Duty Cycle at Lout, RT=1M tied to Vin, Vost=1V, R3(OS)=30k, Toff=209ns, Vcs=0V 900 900 800 800 700 700 600 600 Fsw, kHz Fsw, kHz Fsw vs Duty Cycle, RT=1M tied to Vin, Vost=1V, R3(OS)=30k, Toff=77ns, Vcs=0.4V 500 400 300 500 400 300 200 200 100 100 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 Duty Cycle, % Vin=48V Vin=36V Vin=72V 40 50 60 70 80 90 100 Duty Cycle, % Vin=48V, RT=287K Vin=48V Vin=36V Figure 36. Vin=72V Vin=48V, RT=287K Figure 37. To avoid jittering during the fast duty cycle change and reduce sensitivity to noise, the transfer function of switching frequency of the converter to the duty cycle has 20-kHz bandwidth well below the switching frequency. The maximum switching frequency FSW(max) of converter is given by: FSW ( m ax) @ FSW ( nom ) + 375 kHz (5) Where TOFF affect is neglected as well and the frequency is in kHz. TOFF has more affect on switching frequency FSW at very high frequency. One can see how TOFF affects FSW(max) in Figure 34. The relation between switching frequency FSW and duty cycle D in Figure 34 can be best described by: FSW i FSW ( nom ) D < 0.1 or D > 0.9 i 0 .4 D 0 .6 i FSW (max) iF i SW (max) D ( 1 - D ) 0.1 D < 0.4 or 0.6 < D 0.9 (6) Knowing the maximum switching frequency FSW(max) at D = 0.5 and the ratio of peak output inductor current to the nominal load current KL = IL(max)/IO, allows calculate the output inductor value by using the following Equation 7. LO = VIN D ( 1 - D ) NTR 4 FSW (max) ( KL - 1) IO (7) In this equation NTR is transformer turns ratio from primary winding to the secondary. The selection of KL depends on the average output inductor current IL(ch) that needs to be provided during the start up to charge the output capacitor and supply the load. To ensure that the converter starts the following condition needs to be met. I L (m ax) 2 I L ( ch ) (8) How IL(ch) needs to be defined is described in the following section. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 19 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com Soft Start The soft-start pin SS is multi-function pin used for the following operations: * Soft start with the duty cycle graduate increase from zero to its maximum value of almost 100% * Setting cycle-by-cycle over current hiccup mode conditions * On/off control for the converter * Indicator of severe short circuit condition The soft-start duration is defined by an external capacitor connected between SS pin and ground and the internal charge current that has typical value of 25 A. During soft start, the duty cycle of controller is determined by the voltage at SS pin. Below the 0.85-V threshold, there are no switching pulses at the outputs. Pulling the soft-start pin externally below or above 0.55-V typical threshold can be used for the on/off control. When the soft-start voltage is rising from 0.85 V up to 2.85 V and there is no current limit condition, the duty cycle applied to the output inductor is increasing accordingly from 0 to 1. The external capacitor CSS value can be defined by the Equation 9: CSS = TSS 25 m A ( 2.85V - 0.85V ) (9) For example, if the soft-start time TSS is selected 10 ms, then the soft-start capacitor CSS is equal to 125 nF and the closest available standard value100 nF can be selected. Notice, that the output pulses do not appear until the voltage at soft start capacitor reaches 0.85 V. An additional typical soft start delay caused by this can be calculated by the Equation 10: TDEL = CSS 0.85V 25 m A (10) For the CSS = 100 nF the calculated delay is 3.4 ms. 20 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 The Equation 9 and Equation 10 use typical values for calculations. If the output capacitor of the bus converter is large and the soft-start time is selected relatively short, then the converter should deliver large charge current to the output capacitor to provide the required soft start time. This current might hit the current limit threshold and the soft-start time can be longer than expected. Figure 38 provides an estimation of the required average charge current from the converter to charge the output capacitor within predetermined soft-start time. To avoid tripping of the current limit comparator, the current limit threshold should be set above the required average charge current with the additional current required by the load, half of the output inductor current ripple and the magnetizing current of the transformer. The average output inductor charge current IOUT during the cycle-by-cycle current limit can be described by the following equation: IOUT = IO(lim) - NTR VIN D VIN D ( 1 - D ) 4 Lm FSW 4 NTR LO FSW (11) Here IO(lim) is the output current limit and Lm is magnetizing inductance. The IO(lim) is always less or equal to IL(max) to avoid saturation of the output inductor. The output voltage VO over output current IOUT is as follows VO = (VIN - IOUT RPR / NTR ) D - IOUT RSEC NTR (12) Where RPR is the equivalent resistance on primary side and RSEC is the equivalent resistance on secondary side. 3 Required primary current, A 1 .10 100 10 1 0.1 0.01 0.1 1 Soft start time, ms 10 Cout=100uF Cout=1000uF Cout=10000uF Figure 38. Estimated Average Primary-Side Charge Current From the Converter Required to Charge the Output Capacitor of Specified Value Within Required Soft-Start Time Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 21 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com Figure 39 shows the output voltage as function of the average load current limited by the cycle-by-cycle current limit threshold after substituting (9) into (10). These plots are generated for the following conditions: VIN = 48 V, NTR = 5, LO= 0.1 H, Lm = 75 H, IO(lim) = 73 A, Rpr = 25 m and RSEC = 4 m at FSW= 100 kHz, 200 kHz and 400 kHz. This fold back type of behavior limits the start-up capability of unregulated IBC. One can see that at 100-kHz switching frequency and 0.5 duty cycle (i.e., VO 5 V), only about 11.5 A average current is available to charge the output capacitor while at 400 kHz, the charge current can be as high as 60 A. The plots in Figure 39 show the required average charge current reflected to the primary side of the converter with NTR = 5:1 for different output capacitor values depending on the selected soft-start time, which do not count extra current drawn by the load itself. Therefore the significant output inductor current ripple not only can trip the peak current mode control current limit circuit to reduce the average output inductor current available to charge the output capacitor, but also can cause the hiccup or latch off of the converter to prevent it from starting at all. Increasing the current limit threshold to allow the normal start up of the converter can cause potential overstress if for some reason the load exceeds its nominal current during the steady state operation. Without frequency control circuit, the module operates only at 100 kHz. At 100 kHz the secondary charge current available is only 11.5 A, which is only 2.3 A if reflected to the primary side (NTR = 5). The 2.3-A current is able to charge the 10000-F output capacitor within 10 ms provided that there is no additional load current applied. Cycle-by-cycle current limit 12 10 Vout, V 8 6 4 2 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 Iout, A 100kHz 200kHz 400kHz Vout Steady State (top) Figure 39. Output Voltage at Cycle-by-Cycle Current Limit 22 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 With the frequency control circuit, the start up switching frequency is 400 kHz. At 400-kHz, 60-A charge current is available, which is 12 A if reflected to the primary side. Assuming as in previous case 2.3 A portion of this current is used to charge the 10000-F output capacitor within 10 ms, the remaining 9.7 A on primary side allows extra 48.5-A current to supply the load itself on the secondary side. Figure 40 shows a design example using the startup frequency control of UCC28230 to start up with 30-A constant load current and 10900-F output capacitor. Using SS pin and soft-start capacitor to set cycle-by-cycle over-current hiccup mode is described further in Cycle-by-Cycle Current Limit section and Short Circuit Protection section. Figure 40. Start up at 30-A Constant Current Load With CO = 10900 F Current Sensing The current sensing pin CS is used for the following functional blocks: * Cycle-by-cycle current limit * Adjustable off-time control * Short circuit protection Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 23 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com Cycle-by-Cycle Current Limit and Short Circuit Protection The cycle-by-cycle current limit provides peak current limit on primary side when the load current exceeds its predetermined threshold. For peak current mode control, certain leading edge blanking time is needed to prevent the controller from false tripping due to switching noise. In order to save external RC filter for the blanking time, an internal 50-ns filter at CS input is provided. With the 50-ns delay from the input of the current sense comparator to the outputs, the total propagation delay TCS from CS pin to outputs is about 100 ns. An external RC filter is still needed if the power stage requires more blanking time. The 0.5-V 3% cycle-by-cycle current limit threshold is optimized for efficient current transformer based sensing. The duration when a converter operates at cycle-by-cycle current limit depends on the value of soft-start capacitor and how severe is the over current condition. The soft-start capacitor value also determines the so called hiccup mode off-time duration. These are achieved by the internal discharge current IDS (Equation 13) and IHCC (see Figure 41) at SS pin. I DS = (- 25 (1 - D ) + 5 )m A (13) When the output inductor duty cycle D at cycle-by-cycle current limit is above 80%, the converter operates as the current source and does not enter into hiccup mode at all. This allows parallel operation of converters using droop current sharing technique. At more severe over current condition, the duty cycle D becomes lower and Ids becomes large enough to initiate hiccup mode with periodical restart. The behaviour of the converter at different modes and related soft-start capacitor charge/discharge currents are shown in Figure 41. SS pin, Volts SS Clamp Voltage Soft-Start 4.5 Normal Operation Cycle-byCycle I lim. Off Time before restart SoftRestart 25A Pull Up Thresh. 3.5 Dmax Thresh. 2.85 (for reference) Iss=25A Fast Pull Up Ids=(-25x(1-D)+5)A by 1k Switch Ihcc=-2.5A Outp. Enbl. Thresh. 0.85 SS ShDn. Thresh. 0.55 0 Output Pulses, D t Figure 41. Timing Diagram of Soft-Start Voltage VSS at Different Modes of Operation Defined by Voltage Thresholds and Related Soft-Start Capacitor Charge/Discharge Currents The largest discharge current is at the duty cycle close to zero as 20 A. This current sets the shortest operation time during the cycle-by-cycle current limit which is defined as: TCL( on ) = CSS (4.5V - 3.5V ) 20 m A (14) Thus, if the soft-start capacitor CSS = 100 nF is selected, then the TCL(on) time will be 5 ms. To calculate the hiccup off time TCL(off) before the restart, Equation 15 needs to be used: TCL( off ) = 24 CSS (3.5V - 0.55V ) 2 .5 m A (15) Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 With the same soft-start capacitor value 100 nF, the off time before the restart is going to be 118 ms. Notice, that if the over current condition happens before the soft-start capacitor voltage reaches the 3.5-V threshold during start up, the controller limits the current but the soft-start capacitor continues to be charged. As soon as the 3.5-V threshold is reached, the soft-start voltage is quickly pulled up to the 4.5-V threshold by an internal 1-k RDS(on) switch and the cycle-by-cycle current limit duration timing starts by discharging the soft-start capacitor. Depending on specific design requirements, the user can override default parameters by applying external charge or discharge currents to the soft-start capacitor. Figure 42 shows the operation of a full-bridge system at cycle-by-cycle current limit. The waveforms include drain-source voltages of synchronous rectifiers and voltage at CS pin. The whole cycle-by-cycle current limit and hiccup operation is shown in Figure 43. In this example the cycle-by-cycle current limit lasts about 25 ms followed by 150 ms of off time. Figure 42. Cycle-by-Cycle Current Limit Figure 43. Hiccup Mode with Cycle-by-Cycle Current Limit at IOUT = 60 A Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 25 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com In the event of a severe short circuit condition, the current sense voltage will exceed the short circuit threshold set at 0.7 V min. At this point the controller shuts down the converter with propagation time 100 ns and pulls the soft start pin up to the 4.5-V threshold. (see Figure 44). SS pin, Volts SoftStart SS Clamp Voltage 4.5 SoftRestart Off Time before restart Fast Pull Up by 1k Switch The second current limit threshold0.7V is hit at CS pin indicating short circuit Iss=25A Outp. Enbl. Thresh. 0.85 SS ShDn. Thresh. 0.55 0 Ihcc= -2.5A Output Pulses, D Figure 44. Timing Diagram for the Soft-Start Capacitor Voltage VSS During Short Circuit Protection At this condition the soft-start voltage is forcibly pulled up even if the soft-start charge is not completed. After that, the soft-start capacitor is discharged by 2.5-A current until its voltage reaches the 0.55 V in order to resume the soft-start cycle again. The duration of off time before the restart is defined by Equation 16: TCL( off ) = CSS (4.5V - 0.55V ) 2 .5 m A (16) With the same soft-start capacitor value 100 nF, the off time before the restart is going to be about 158 ms. Similar to the over current condition, the hiccup mode with the restart can be override by user if a pull-up resistor is connected between the SS and VREF pins. If the pull-up current provided by the resistor exceeds 2.5 A, then the controller remains in the latch-off mode. In this case, an external soft-start capacitor value should be calculated with the additional pull-up current taken into account. The latch-off mode can be reset externally if the soft-start capacitor forcibly discharged below 0.55 V or the VDD voltage is lowered below the UVLO threshold. 26 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 Off-Time Control Circuit The off time control circuit provides optimal off time between O1_D and O2_D outputs depending on the load current condition. The UCC28230/1 implements the off time control approach based on step function with hysteresis (see Figure 45). Off-time control is an important feature to address an optimal operation of self-driven synchronous rectifier over the whole load current range. In self-driven rectifier applications, the turn-on and off time of the synchronous FETs is defined by the current of output inductor and its polarity. Some additional energy is also provided from the magnetizing inductance of a power transformer but it may not be sufficient for the fast switching. Therefore, at light load the off-time should be longer than at full load to allow previously conducting rectifier MOSFET to be completely turned off before the next switching half-cycle. This ensures the rectifier MOSFET having enough time to turn off before the primary-side MOSFET forces it to turn off. The turn off of the rectifier MOSFET, while still conducting, results in a current surge followed by a significant voltage spike which lowers the efficiency and reliability of converter. TOFFMAX at light load = 5x TOFF with Off Time Control Threshold set to 20% of IMAX TOFF TDT T CLAMP Hysteresis = IHYST x R1 x R2/(R1+R2) Off Time Control Threshold (Set by resister divider R1/R2 from Pin VREF to pin OST and to GND) TDT TCLAMP TDT 0 TOFF2.5xTDT at heavy load (set by resister R3 from pin OS to GND) Iout Ensures no cross conduction at light load Provides minimum diode conduction over wide range of load conditions Figure 45. The Off Time Change as Function of Load Current Usually there is no direct access to the load current of bus converters, so the primary current sensing is used to replicate load current changes (see Figure 45). The largest part of the primary current is the load current on secondary side of power transformer reflected into the primary side in accordance to transformer's turn ratio. The primary current includes not only the reflected load current, but also magnetizing current. However, for the most practical applications the accuracy of solution with magnetizing current included is sufficient because in this application the magnetizing current is only small percentage of overall current. With this assumption, the voltage at pin CS can be defined as: VCS = IOUT RCS WCT ( pr ) W PT (sec) W PT ( pr ) WCT (sec) (17) Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 27 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com Where IOUT is the output inductor current, RCS is the current sense resistor, WPT(pr) and WPT(sec) are the primary and secondary number of turns of power transformer windings and the WCT(pr) and WCT(sec) are the primary and secondary number of turns of current transformer windings. UCC28230/1 uses OS pin and OST pin to program the nominal off time TOFF and the output current threshold where the off time steps up to the new value TOFF(max). The dead time Td and nominal off time TOFF are set by resistor R3 between OS pin and GND (Figure 3, Figure 4 and Figure 50). Figure 46 shows how to choose R3 resistance to achieve the dead time Td and nominal off time TOFF for both UCC28230 and UCC28231. For example, if a 40ns nominal TOFF is needed, the resistor value should be 8.45k, and Td is about 17ns for UCC28230 and 15ns for UCC28231. 15 k R3 at OS pin sets TOFF to 50 ns and Td to 23 ns for UCC28230, with TOFF as 47 ns and Td as 19 ns for UCC28231. Based on Figure 46, one can tell that TOFF is about 2.2 to 2.64 times of Td for UCC28230, and 2.25 to 2.75 times of Td for UCC28231. Figure 25 through Figure 30 from Typical Waveforms show the output switching waveforms including rise and fall time and off time TOFF1, TOFF2 for each half switching cycle and dead time Td1, Td2, Td3 and Td4 for each half switching cycle. Off time and dead time selection based on the resistor R3 value. UCC28230 Off Time TOFF and Dead Time TD vs ROS UCC28230 Off Time TOFF and Dead Time TD vs ROS 100 350 90 80 250 TOFF and T D (ns) TOFF and T D (ns) 300 200 150 100 70 60 50 40 30 20 50 10 0 0 0 15 30 45 60 75 90 105 120 135 0 150 5 10 15 Off Time 20 25 30 35 ROS (k) ROS (k) Off Time Dead Time Figure 46. Dead Time Figure 47. UCC28231 Off Time TOFF and Dead Time TD vs ROS UCC28231 Off Time TOFF and Dead Time TD vs ROS 300 100 90 80 TOFF and T D (ns) TOFF and T D (ns) 250 200 150 100 70 60 50 40 30 20 50 10 0 0 0 20 40 60 80 100 120 140 160 180 200 0 5 10 ROS (k) Off Time 20 25 30 35 40 45 50 55 60 ROS (k) Dead Time Figure 48. 28 15 Off Time Dead Time Figure 49. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 The next step is to set the output current threshold below that the off time changes to its maximum value. This threshold is defined as: VOST = VREF R2 R1 + R 2 (18) The increase of off time at light load condition is provided by the increasing of overlapping time TCLAMP of O1_DIN and O2_DIN outputs (see Figure 33). This ensures the faster turning off of the rectifier MOSFETs when the primary winding is clamped. The dead time between the switching of primary MOSFETs in each leg remains the same over the load current, which is still proportional to nominal off time as shown in Figure 46. 5V for UCC28230, 3.3V for UCC28231 VREF 1 OS R1 TOFF set circuit 3 To Logic Block R3 2 R2 OST I HYST = 10 A Iprim CS 6 Is X 10 filtering RCS CT Cycle-by-Cycle Current Limit Figure 50. The Off-Time Control Circuit Using Comparator With Hysteresis Selecting optimal hysteresis is important to avoid oscillation. UCC28230/31 provides the flexibility of programming the hysteresis with internal 10-A current IHYST and the values of external resistors R1 and R2 (see Figure 50). Equation 19 shows how to choose the hysteresis. Vhyst = Ihyst R1 R 2 R1 + R 2 (19) In some cases, the disabling of off-time control circuit is needed, which can be done by simply connecting OST pin to GND or to VREF. Connecting OST pin to the VREF is characterized in the electrical table and is the preferable way to maintain fixed off time set by resistor R3. The load dependent dead time will cause a slight change in output duty cycle at the programmed transition point from light load to heavy load and vice-versa. This slight change in duty cycle corresponds to a slight change in output voltage. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 29 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com APPLICATION INFORMATION DESIGN EXAMPLE 1 V 0 Two design examples are provided to show how to design an intermediate bus converter with UCC28230/1. Design Example 1 provides a concise step-by-step design. Its design specifications, schematics and test results are illustrated on efficiency, power dissipation and output voltage regulation. Design Example 2 is to show an industry standard quarter brick module design with 12-layer boards and embedded magnetic parts. Its design specifications, schematics, and test results are provided. Figure 51. Design Example of IBC Using UCC28230 Controller Device 30 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 Design Goals This example illustrates the design process and component selection for an intermediate bus converter using UCC28230. The target design is a 300-W full bridge converter with narrowed input voltage range in a close to quarter brick form factor with open-loop control for the telecom applications in intermediate bus architecture. Its specifications are shown in Table 1. Table 1. 300W IBC Specifications PARAMETER MIN 43 TYP MAX UNIT 48 53 VDC Input voltage VIN Output voltage VOUT Output power POUT 300 W Output load current IOUT 30 A Load capacitance COUT Switching frequency FSW Over power limit PLIMIT Efficiency at full load (VIN = 48 V) 9.6 10,000 125 150% 96% Isolation Turns-ratio F kHz 1500 NPRI : NSEC V 5:1 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 31 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com Recommended PCB Device Layout The device programming components should be placed as close as possible to the device. The power ground should be separated from the signal ground and connected only at one point at device pin 8 and 9 for TSSOP package. For SON package there is only one ground pin available, pin 7. In this case, pin 7 is used to replace the connection of pin 8 and pin 9 of TSSOP. The following takes TSSOP as the example. For SON, a similar arrangement on the layout should be made. Capacitors for bias decoupling (C5), reference voltage decoupling (C6), and soft start (C9), should be placed right across the signal ground and pins 14, 1 and 6, respectively. All programming resistors, R2, R3, R5, and R7 should be placed next to the device pins they should be connected to minimize their EMI noise reception. See Figure 52 for a recommended component layout and placement. PCB design considerations of other circuit part are discussed later in the relevant part design. Figure 52. Figure 53. 32 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 Programming the UCC28230 Switching frequency: R7 Equation 3 R 7 = RT = K 1 (VREF - K 2 ) ( 5 - 2 .4 ) = 2500 = 52 k W 52.3 k W fSW 125 (20) Soft-start time: C9 Considering power on with maximum 10,000-F load capacitors, soft-start time may need be adjusted and if soft-start time is determined as 25 ms, then based on Equation 9 C9 = CSS = TSS K 3 25 25 m A = = 0.27 m F 0.33 m F ( K 4 - K 5 ) ( 2.85V - 0.85V ) (21) Multilayer ceramic capacitor (X7R or X5R) should be used. Dead time set-up resistor, R5 Assuming Td = 20 ns, based on Figure 46 R 5 = 13 k W 15 k W (22) Off-time adjustment threshold and hysteresis resistors: R2 and R3 TOFF is set up at 10% of rated load, VOST = 0.5V, with hysteresis VHYST = 100 mV. Based on Equation 18 and Equation 19, k VOST R3 = R 2 (VREF - VOST ) R3 = Vhyst Ihyst (23) ae o V OST c1+ / e VREF - VOST o (24) Solution to the above two equations yields R2 = 99.9 k, and R3 = 11.1 k. VDD decoupling capacitor: C5 High quality low ESR and low ESL such as multilayer ceramic capacitor (X7R or X5R) with a value between 0.1 to 1.0 F should be used. VREF decoupling and stability capacitor: C6 High quality low ESR and low ESL such as multilayer ceramic capacitor (X7R or X5R) with a value between 1.0 to 2.2 F should be used . Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 33 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com Current Sensing Power stage design shows primary DC current maximum value is determined IP ( rms ) = PLIMIT 450 = = 10 .5 (with 20 % m arg in ) 12 .6 A VIN (min) 43 (25) If pick up a current transformer with turns ratio of 100:1, R4 is determined as 5.11 with current sense threshold at 150% of rated power. Current sensing plays a critical role to achieve several features of UCC28230 including over current protection and off time adjustment. Usually the sensing element cannot be placed next to the device. In such a case, it is strongly recommended to route the PCB with Kelvin connection from the current sensing output device (R4) to the IC (Pin 7) as shown in Figure 54. A small RC filter (R8 and C10) is required to attenuate possible high frequency noise. A small capacitor, C8, can also be added to get further filtering effect while usually it is not needed. Figure 54. 34 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 Power Stage Transformer: The design goal shows a 300-W transformer with turns ratio 5:1. To make the design close to the telecom typical applications, planar magnetic core is used with windings using PCB traces. Primary MOSFETs In steady state, the primary MOSFET's duty cycle is about 50%. At minimum input voltage 43 V, maximum 450-W power, and 96% efficiency, their current rating can be determined as ID( rms ) = PLIMIT 450 0 .5 a = = 7 .7 A h 43 0 .96 VIN (min) (26) = duty cycle of MOSFETS Their voltage rating is determined as 53 V. After considering 20% margin, current and voltage rating should be 9 A and 80 V, respectively. Primary MOSFET drivers The UCC28230 of 0.2-A MOSFET driving capability requires external MOSFET drivers. One good option is to use UCC27200 for U1 and U3. Gate resistors (1.0 ) of R16-19 are suggested to add in and attenuate possible parasitic ringing. UCC27200 is designed for half bridge application with 2-A driving capability. Each UCC27200 should have its own VDD high quality decoupling and driving energy capacitor (typical value 1.0 F) of low ESR and low ESL. Its boost strap capacitor value of 0.1F can be selected. Secondary MOSFETs In steady state, the secondary MOSFETs have their duty about 50%. At minimum input voltage 43 V, maximum 450-W power, transformer turns ratio 5:1, their current rating can be determined as: ID( rms ) = PLIMIT 450 a Nt = 0.5 5 = 52.3 A 43 VIN(min) (27) Their voltage rating can be determined as: VDS = VIN (max) Nt 2 = 53 2 = 21 .2 V 5 (28) After considering potential parasitic ringing, 40-V MOSFETs may be used. Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 35 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com Output Inductor The output inductor value is determined by the start-up condition with supposed maximum peak-to-peak ripple current. The ripple current is a function of input voltage, duty cycle, switching frequency and transformer turns ratio. At start, a highest ripple should occur at about 0.5 duty cycle and maximum input voltage when the switching frequency should be designed in accordance with the top flat area shown in Figure 34. A typical ripple current can be initially taken around 90% of the maximum output current from steady state operation. L2 = D ( 1 - D ) VIN 0.5 ( 1 - 0.5 ) 53 = = 106 nH 2 n fsw I pk - pk 2 5 500 103 25 (29) The inductor value is then determined to be 100 nH. Test Results 97.00% 96.00% Efficiency 95.00% 94.00% 43Vin 48Vin 53Vin 93.00% 92.00% 91.00% 90.00% 5 10 15 20 25 30 35 Load Current A Figure 55. Efficiency 36 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 15.000 14.000 13.000 12.000 Power Loss W 11.000 10.000 9.000 43V 8.000 48V 7.000 53V 6.000 5.000 4.000 3.000 2.000 1.000 0.000 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 Load Current A Figure 56. . Power Dissipation 11.000 Output Voltage V 10.500 10.000 43Vin 9.500 48Vin 53Vin 9.000 8.500 8.000 0 5 10 15 20 25 30 35 Load Current A Figure 57. Load regulation Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 37 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com 11V 11V Design Example 2 Figure 58. 38 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 UCC28230 UCC28231 www.ti.com ................................................................................................................................................... SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 This design consists of a 350 watt 6:1 bus converter in an industry standard quarter brick package, utilizing the UCC28230 PWM Bus Controller, UCC27201 High Voltage High-Side Low-Side Drivers and a 12-layer PCB with embedded magnetic parts. This design features low profile construction representative of typical isolated dc-to-dc construction in a quarter brick form factor. Typical efficiency above 97% is achieved with this design. By using the UCC28230 PWM Bus Controller allows optimum duty cycle control for both light load and full load. The unique feature of sampling the primary transformer current and controlling the dead time provides reduced no load/ light load power dissipation by increasing the dead time to minimize output synchronous rectifier cross conduction, yet reducing the dead time at higher output loads to achieve maximum power transfer to the load. As with all self driven synchronous rectifiers, transformer design is critical. Minimal leakage inductance to reduce ringing on the MOSFETs and minimize or eliminate snubbers along with optimum coupling of the output secondary winding with the gate drive winding for precise timing of the turn on and off of the synchronous rectifiers. This is required to reduce the amount of conduction of the internal intrinsic diode of the MOSFETs. 350-W IBC Specifications PARAMETER MIN TYP MAX UNIT 48 60 VDC Input voltage VIN Output voltage VOUT 36 Output power POUT 350 W Output load current IOUT 45 A Load capacitance COUT Switching frequency FSW Over power limit PLIMIT Efficiency at full load (VIN = 48V) 8.0 10,000 165 150% 96% Isolation Turns-ratio F kHz 1500 V NPRI : NSEC 6:1 Test Results UCC28230 IBC Efficiency 99 97 Efficiency % 95 36.0V 93 48.0V 91 60.0V 89 87 85 4.5 9 13.5 18 22.5 27 31.5 36 40.5 45 Load Current A Figure 59. Efficiency Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 39 UCC28230 UCC28231 SLUS814A - FEBRUARY 2008 - REVISED JUNE 2008 ................................................................................................................................................... www.ti.com UCC28230 REFERENCE Power Dissipation 20.0 18.0 16.0 Pd - Watts 14.0 12.0 36.0V 10.0 48.0V 8.0 60.0V 6.0 4.0 2.0 0.0 0 5 10 15 20 25 30 35 40 45 Iout()-Amps Figure 60. Power Dissipation UCC28230 REFERENCE Load Regulation 12.000 10.000 Vout - V 8.000 36.0V 48.0V 6.000 60.0V 4.000 2.000 0.000 0 5 10 15 20 25 30 35 40 45 Iout()-Amps Figure 61. Load Regulation 40 Submit Documentation Feedback Copyright (c) 2008, Texas Instruments Incorporated Product Folder Link(s): UCC28230 UCC28231 PACKAGE OPTION ADDENDUM www.ti.com 8-Dec-2009 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty UCC28230DRNR ACTIVE USON DRN 12 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28230DRNRG4 ACTIVE USON DRN 12 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28230DRNT ACTIVE USON DRN 12 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28230DRNTG4 ACTIVE USON DRN 12 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28230PW ACTIVE TSSOP PW 14 90 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28230PWG4 ACTIVE TSSOP PW 14 90 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28230PWR ACTIVE TSSOP PW 14 2000 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28230PWRG4 ACTIVE TSSOP PW 14 2000 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28231DRNR ACTIVE USON DRN 12 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28231DRNRG4 ACTIVE USON DRN 12 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28231DRNT ACTIVE USON DRN 12 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28231DRNTG4 ACTIVE USON DRN 12 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28231PW ACTIVE TSSOP PW 14 90 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28231PWG4 ACTIVE TSSOP PW 14 90 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28231PWR ACTIVE TSSOP PW 14 2000 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM UCC28231PWRG4 ACTIVE TSSOP PW 14 2000 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM Lead/Ball Finish MSL Peak Temp (3) (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) Addendum-Page 1 PACKAGE OPTION ADDENDUM www.ti.com 8-Dec-2009 (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. 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Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 8-Dec-2009 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing UCC28230DRNR USON DRN 12 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 3000 330.0 12.4 2.3 3.3 0.85 4.0 12.0 Q1 UCC28230DRNT USON DRN 12 250 330.0 12.4 2.3 3.3 0.85 4.0 12.0 Q1 UCC28231DRNR USON DRN 12 3000 330.0 12.4 2.3 3.3 0.85 4.0 12.0 Q1 UCC28231DRNT USON DRN 12 250 330.0 12.4 2.3 3.3 0.85 4.0 12.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 8-Dec-2009 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) UCC28230DRNR USON DRN 12 3000 340.5 338.1 20.6 UCC28230DRNT USON DRN 12 250 340.5 338.1 20.6 UCC28231DRNR USON DRN 12 3000 340.5 338.1 20.6 UCC28231DRNT USON DRN 12 250 340.5 338.1 20.6 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. 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