APR346 SECONDARY SIDE SYNCHRONOUS RECTIFICATION CONTROLLER Description Pin Assignments The APR346 is a secondary side MOSFET driver for synchronous rectification, supports CCM, DCM and Quasi-Resonant Flyback Topologies. (Top View) NEW PRODUCT Pin 1 Mark The synchronous rectification can effectively reduce the secondary side rectifier power dissipation and provide high performance solution. By sensing primary MOSFET gate-to-source voltage, the APR346 can output ideal drive signal with less external components. It can provide high performance solution for 5V to 20V output voltage application. The APR346 is available in SOT26 package. AREF 1 6 DRISR GND 2 5 CCM VDET 3 4 VCC Features SOT26 Synchronous Rectification for CCM, DCM Operation Flyback Eliminate Resonant Ring Interference Fewest External Components Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) Halogen and Antimony Free. "Green" Device (Note 3) Notes: Applications Adapters/Chargers for Cell/Cordless Phones, ADSL Modems, MP3 and Other Portable Apparatus 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS), 2011/65/EU (RoHS 2) & 2015/863/EU (RoHS 3) compliant. 2. See https://www.diodes.com/quality/lead-free/ for more information about Diodes Incorporated's definitions of Halogen- and Antimony-free, "Green" and Lead-free. 3. Halogen- and Antimony-free "Green" products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and <1000ppm antimony compounds. Typical Applications Circuit Q2 Q1 D1 6 CY Primary Control IC DRISR R1 3 C24 4 VCC GND 2 AREF 1 VDET APR346 R2 ZD1 CCCM ZD2 R3 RAREF 5 CCM CAREF APR346 Document number: DS38999 Rev. 6 - 2 1 of 11 www.diodes.com May 2018 (c) Diodes Incorporated APR346 Pin Descriptions Pin Name Function 1 AREF Program a voltage reference with a resistor from AREF to GND, to enable synchronous rectification MOSFET drive signal 2 GND Ground 3 VDET SR MOS drain-to-source voltage sense input, connected to drain pin of SR MOSFET through a resistor 4 VCC Power supply, connected with system output 5 CCM Primary trigger signal sense input 6 DRISR NEW PRODUCT Pin Number Synchronous rectification MOSFET Gate drive Functional Block Diagram VCC 4 IAREF AREF Test Mode Fault Mode Power OK VDD Regulator VREF 1 VCC Integrator (VDETVCC)dt S Q S Q 6 Drive R DRISR R VTHON Gate Monitor VCC LEB Time 3 VDET VTHOFF VTHCCM 5 CCM APR346 Document number: DS38999 Rev. 6 - 2 2 of 11 www.diodes.com 2 GND May 2018 (c) Diodes Incorporated APR346 Absolute Maximum Ratings (Note 4) Symbol Rating Unit VCC Supply Voltage -0.3 to 28 V VDET Voltage at VDET Pin (Note 5) -0.7 to 160 V Voltage at DRISR Pin -0.3 to 20 V VDRISR NEW PRODUCT Parameter PD Power Dissipation at TA = +25C 0.6 W TJ Operating Junction Temperature +150 C -65 to +150 C TSTG Storage Temperature TLEAD Lead Temperature (Soldering, 10s) +300 C JA Thermal Resistance (Junction to Ambient) 197 C/W JC Thermal Resistance (Junction to Case) 76 C/W Notes: 4. Stresses greater than 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 Ratings" for extended periods may affect device reliability. 5. VDET pin ESD sensitive. Recommended Operating Conditions Symbol VCC TA Parameter Supply Voltage Ambient Temperature APR346 Document number: DS38999 Rev. 6 - 2 3 of 11 www.diodes.com Min Max Unit 0 25 V -40 +85 C May 2018 (c) Diodes Incorporated APR346 Electrical Characteristics (@VCC = 5V, TA = -40C <TA<+85C, unless otherwise specified.) Symbol Parameter Condition Min Typ. Max Unit Supply Voltage ( VCC Pin ) Startup Current VCC = VSTARTUP-0.1V - 150 200 A Operating Current VDET Pin Floating VCC = 5V - 150 200 A Startup Voltage - 2.6 3.1 3.4 V UVLO - 2.3 2.8 3.1 V VTHON Gate Turn On Threshold - 0 - 1 V VTHOFF Gate Turn Off Threshold - -9 -6 -3 mV tDON Turn On Delay Time From VTHON to VDRISR = 1V - 70 130 ns tDOFF Turn Off Propagation Delay Time From VTHOFF to VDRISR = 4V - 100 150 ns - 50 100 ns - 20 35 ns 1.2 1.6 2 s ISTARTUP NEW PRODUCT IOP VSTARTUP - Gate Driver tRG Turn On Rising Time tFG Turn Off Falling Time From 1V to 4V, VCC=5V, CL=4.7nF From 4V to 1V, VCC=5V, CL=4.7nF Minimum On Time - VDRI_CLAMP Drive Output Clamp Voltage VCC> VDRI_CLAMP - 15 - Drive Voltage during Minimum On Time VCC< =VDRI_CLAMP - - VCC VDRI_TONMIN VCC>= VDRI_CLAMP - - VDRI_CLAMP VCC<5V - - VCC VCC>=5V - 5 - tON_MIN VDRISR VDRI_HOLD KQS VS_MIN SR Drive Hold Voltage V (Note 6) - 0.325 0.42 0.515 mA*s Synchronous Rectification (SR) Minimum Operating Voltage (Note 7) - - - 4.5 V - 0.53 - V - 20 35 ns Synchronous Rectification Detection Notes: VTH_CCM VDRISR Rising Threshold tDCCM CCM Propagation Delay VDRISR Output Transitions from High to Low From CCM Rising to VDRISR Falling 10% 6. This item is used to specify the value of RAREF. 7. This item specifies the minimum SR operating voltage of VIN_DC, VIN_DCNPS*VS_MIN. APR346 Document number: DS38999 Rev. 6 - 2 4 of 11 www.diodes.com May 2018 (c) Diodes Incorporated APR346 Synchronous Rectification Principle Description NEW PRODUCT SR MOSFET Turn on The APR346 determines the synchronous rectification MOSFET turning on time by monitoring the MOSFET drain-to-source voltage. For both of DCM and CCM operation, the turning on principle is same. When the drain voltage is lower than the turn-on threshold voltage VTHON, the IC outputs a positive drive voltage after a turn-on delay time (tDON). The MOSFET will turn on and the current will transfer from the body diode into the MOSFET's channel. Since of parasitic parameter, the voltage on MOSFET drain pin has moderate voltage ringing at this moment, which maybe impact on SR controller VDET voltage sense and bring about turning off fault. To avoid fault situation happening, a Minimum On Time (tONMIN) blanking period is used that will maintain the power MOSFET on for a minimum amount of time. In Figure 1, the turn on blanking time tONMIN is to prevent the MOSFET drain-to-source voltage ringing affect. During this time, the VDRISR is pulled up to VCC; after tONMIN, the drive voltage stops be pulled up by the driver, and begins to drop; when VDRISR drops to VDRI_HOLD, it will be held at this voltage until be pulled down. DCM Turn off Operation The DCM operation of the SR is described with timing diagram shown in Figure 1. In the process of drain current decreasing linearly toward zero, the drain-source voltage rises synchronically. When it rises over the turn off threshold voltage VTHOFF, the APR346 pulls the drive signal down after a turn-off delay (tDOFF). I,V VDET IS VTHON 0 t VTHOFF VDRI_HOLD 0.9VDRI_HOLD 0 1V tDON tONMIN tDOFF t Figure 1. Typical Waveforms of APR346 in DCM CCM Turn off Operation The CCM pin is used to sense trigger signal for turning off the SR MOSFET before primary switch turning on in Continuous Conduction Mode (CCM) system. After tONMIN, if the CCM pin voltage rises over the threshold voltage VTHCCM, the drive voltage will be pulled down after a short delay time tDCCM to turn off SR MOSFET. The CCM pin senses trigger signal coming from primary switch turn on signal through a RC networks circuit, a Y-type isolating capacitor CCCM, two resistors R2 and R3. Note variations of these resistors, of CCCM, and of the dV/dt across CCCM require that worst-case tolerances be taken into account when determining the minimum value of CCCM. For example, the value of this resistor will impact the rise time of CCM voltage. The bigger resistor, the slower the CCM voltage rises. The value of CY should be much higher than that of CCCM. If necessary, increase the value of CY to ensure that CY >> CCCM; do not decrease CCCM. CY is the main common-mode capacitance between the primary and the secondary sides of the system. This is usually a discrete component, whose value ranges from 47pF ~ 2200pF. Aside from any EMI-control purposes, it also serves as the return path for the CCM signal charging and discharging current pulses. APR346 Document number: DS38999 Rev. 6 - 2 5 of 11 www.diodes.com May 2018 (c) Diodes Incorporated APR346 Synchronous Rectification Principle Description (Cont.) VGATE_PRIMARY NEW PRODUCT 0 t VCCM VTH_CCM 0 t VDRISR VDRI_HOLD 0.9VDRI_HOLD 0 tDCCM t Figure 2. Typical Turn off Waveforms of APR346 in CCM Minimum On Time When the controlled MOSFET gate is turned on, some ringing noise is generated. The minimum on-time timer blanks the VTHOFF comparator and CCM comparator, keeping the controlled MOSFET on for at least the minimum on time. During the minimum on time, the turn off threshold (DCM and CCM) is totally blanked. The Value and Meaning of AREF Resistor As to DCM operation Flyback converter, after secondary rectifier stops conduction, the primary MOSFET Drain-to-source ringing waveform is resulted from the resonant of primary inductance and equivalent switch device output capacitance. This ringing waveform probably leads to Synchronous Rectifier error conduction. To avoid this fault happening, the APR346 has a special function design by means of volt-second product detecting. From the sensed voltage of VDET pin to see, the volt-second product of voltage above VCC at primary switch on time is much higher than the volt-second product of each cycle ringing voltage above V CC. Therefore, before every time Synchronous Rectifier turning on, the APR346 judges if the detected volt-second product of VDET voltage above VCC is higher than a threshold and then turn on synchronous Rectifier. The purpose of AREF resistor is to determine the volt-second product threshold. The APR346 has a parameter, KQS, which converts RAREF value to volt-second product, Area 2 R AREF * KQS In general, Area1 and Area3 value depend on system design and are always fixed after system design frozen. As to Diodes Incorporated's PSR design, the Area1 value changes with primary peak current value and Area3 value generally keeps constant at all of conditions. So the AREF resistor design should consider the worst case, the minimum primary peak current condition. Since of system design parameter distribution, Area1 and Area3 have moderate tolerance. So Area2 should be designed between the middle of Area1 and Area3 to keep enough design margin. Note: To keep the volt-second product threshold stable, a capacitor is suggested to parallel with AREF resistor. And the recommended value of this capacitor is 20nF. Area3 RAREF * KQS Area1 APR346 Document number: DS38999 Rev. 6 - 2 6 of 11 www.diodes.com May 2018 (c) Diodes Incorporated APR346 Synchronous Rectification Principle Description (Cont.) Area1=(VDET-VCC)*tONP Area3 NEW PRODUCT VDET VCC Area2=KQS*RAREF Figure 3. AREF Function SR Minimum Operating Voltage The APR346 sets a minimum SR operating voltage by comparing the difference between V DET and output voltage (VCC). The value of VDET-VCC must be higher than its internal reference, then the APR346 will begin to integrate the area of (VDET-VCC)*tONP. If not, the area integrating will not begin and the SR driver will be disabled. SR Turning Off Timing Impact on PSR CV Sampling As to synchronous rectification on Flyback power system, SR MOSFET need to turn off in advance of secondary side current decreasing to zero to avoid current flowing reversely. When SR turns off in advance, the secondary current will flow through the body diode. The SR turning off time is determined by the VTHOFF at a fixed system. When VTHOFF is more close to zero, the SR turning on time gets longer and body diode conduction time gets shorter. Since of the different voltage drop between SR MOSFET and body diode, the PSR feedback signal VFB appears a voltage jump at the time of SR MOSFET turning off. If the PSR CV sampling time tSAMPLE is close to even behind this voltage jump time, there will be system unstable operation issue or the lower output voltage issue. To ensure stable operating of system, it must be met: tBODYDIODE<tONS- tSAMPLE tSAMPLE SR Turnoff, Bodydiode operating SR Operating tBODYDIODE VFB tONS Figure 4. SR Turning Off Timing Impact on PSR CV Sampling APR346 Document number: DS38999 Rev. 6 - 2 7 of 11 www.diodes.com May 2018 (c) Diodes Incorporated APR346 Synchronous Rectification Principle Description (Cont.) Recommended Application Circuit Parameters CAREF is suggested to parallel with AREF resistor to keep the volt-second product threshold stable. And the recommended value of CAREF is 20nF. The recommended value of C24 is 100nF. NEW PRODUCT Ordering Information APR346 X X - X Product Name Package Packing RoHS/Green K6 : SOT26 TR : Tape & Reel G1 : RoHS Compliant and Green Package Temperature Range Part Number Marking ID Packing SOT26 -40C to +85C APR346K6TR-G1 GUC 3000/Tape & Reel Marking Information (1) SOT26 ( Top View ) 5 4 7 6 GUC Y W X GUC : Marking ID Y : Year 0~9 W : Week : A~Z : 1~26 week; a~z : 27~52 week; z represents 1 APR346 Document number: DS38999 Rev. 6 - 2 2 3 52 and 53 week X : Internal Code 8 of 11 www.diodes.com May 2018 (c) Diodes Incorporated APR346 Package Outline Dimensions (All dimensions in mm(inch).) (1) Package Type: SOT26 0 2.820(0.111) 8 3.100(0.122) 2.650(0.104) 3.000(0.118) 6 0.200(0.008) 5 4 2 3 0.300(0.012) 0.600(0.024) 1.500(0.059) 1.700(0.067) NEW PRODUCT 0.300(0.012) 0.500(0.020) Pin 1 Mark 1 0.700(0.028)REF 0.950(0.037)TYP 0.000(0.000) 0.150(0.006) 1.800(0.071) 2.000(0.079) 0.100(0.004) 0.200(0.008) 0.900(0.035) 1.450(0.057) MAX 1.300(0.051) APR346 Document number: DS38999 Rev. 6 - 2 9 of 11 www.diodes.com May 2018 (c) Diodes Incorporated APR346 Suggested Pad Layout (1) Package Type: SOT26 NEW PRODUCT E E Y G Z X Dimensions Z (mm)/(inch) G (mm)/(inch) X (mm)/(inch) Y (mm)/(inch) E (mm)/(inch) Value 3.600/0.142 1.600/0.063 0.700/0.028 1.000/0.039 0.950/0.037 APR346 Document number: DS38999 Rev. 6 - 2 10 of 11 www.diodes.com May 2018 (c) Diodes Incorporated APR346 IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). 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