XR76203/5/8 40V PowerBloxTM 3A/5A/8A Synchronous Step Down COT Regulator FEATURES General Description Controller, drivers, bootstrap diode and MOSFETs integrated in one package 3A, 5A and 8A Step Down Regulators Wide 5V to 40V Input Voltage Range >0.6V Adjustable Output Voltage Proprietary Constant On-Time Control No Loop Compensation Required Stable Ceramic Output Capacitor Operation Programmable 200ns to 2s On-Time Constant 100kHz to 800kHz Frequency Selectable CCM or CCM/DCM CCM/DCM for high efficiency at light-load CCM for constant frequency at light-load Programmable Hiccup Current Limit with Thermal Compensation Precision Enable and Power Good flag Programmable Soft-start 30-pin 5x5mm QFN package The XR76203, XR76205 and XR76208 are synchronous step-down regulators combining the controller, drivers, bootstrap diode and MOSFETs in a single package for point-of-load supplies. The XR76203, XR76205 and XR76208 have load current ratings of 3A, 5A and 8A respectively. A wide 5V to 40V input voltage range allows for single supply operation from industry standard 24V 10%, 18V-36V, and rectified 18VAC and 24VAC rails. With a proprietary emulated current mode Constant On-Time (COT) control scheme, the XR76203, XR76205 and XR76208 provide extremely fast line and load transient response using ceramic output capacitors. They require no loop compensation, simplifying circuit implementation and reducing overall component count. The control loop also provides 0.07% load and 0.15% line regulation and maintains constant operating frequency. A selectable power saving mode allows the user to operate in discontinuous conduction mode (DCM) at light current loads thereby significantly increasing the converter efficiency. A host of protection features, including over-current, over-temperature, short-circuit and UVLO, helps achieve safe operation under abnormal operating conditions. APPLICATIONS The XR76203/5/8 are available in a RoHS-compliant, green/halogen-free space-saving QFN 5x5mm package. Distributed Power Architecture Point-of-Load Converters Power Supply Modules FPGA, DSP, and Processor Supplies Base Stations, Switches/Routers, and Servers Ordering Information - back page Typical Application Line Regulation 3.340 VIN VIN PVIN 3.330 CBST EN/MODE BST PGOOD CIN SW XR76208 VCC R SS TON CVCC CSS RON AGND XR76205 XR76203 RLIM CFF ILIM R1 COUT FB R2 PGND 3.320 VOUT L1 Power Good VOUT (V) Enable/Mode 3.310 3.300 3.290 3.280 3.270 3.260 5 10 15 20 25 30 35 40 VIN (V) (c) 2015 Exar Corporation 1 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Absolute Maximum Ratings Operating Conditions Stresses beyond the limits listed below may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. PVIN...............................................................................5V to 40V SW, ILIM.....................................................................-1V to 40V1 PVIN, VIN...................................................................-0.3V to 43V PGOOD, VCC, TON, SS, EN, FB...............................-0.3V to 5.5V VCC...........................................................................-0.3V to 6.0V Switching Frequency......................................100kHz to 800kHz3 BST..........................................................................-0.3V to 48V1 Junction Temperature Range..............................-40C to +125C BST-SW.......................................................................-0.3V to 6V XR76203 JEDEC51 Package Thermal Resistance, JA...............28C/W SW, ILIM..................................................................-1V to 43V1, 2 XR76205 JEDEC51 Package Thermal Resistance, JA...............26C/W ALL other pins.................................................-0.3V to VCC+0.3V XR76208 JEDEC51 Package Thermal Resistance, JA...............25C/W Storage Temperature...........................................-65C to +150C XR76203 Package Power Dissipation at 25C......................3.6W Junction Temperature..........................................................150C XR76205 Package Power Dissipation at 25C......................3.8W Power Dissipation...............................................Internally Limited XR76208 Package Power Dissipation at 25C......................4.0W VIN.................................................................................5V to 40V Lead Temperature (Soldering, 10 sec)................................300C Note 1: No external voltage applied. ESD Rating (HBM - Human Body Model)...............................2kV Note 2: SW pin's minimum DC range is -1V, transient is -5V for less than 50ns. Note 3: Recommended frequency Electrical Characteristics Unless otherwise noted: TJ= 25C, VIN=24V, BST=VCC, SW=AGND=PGND=0V, CVCC=4.7uF. Limits applying over the full operating temperature range are denoted by a "*" Symbol Parameter Conditions Min Typ Max Units 40 V 2 mA Power Supply Characteristics VIN Input Voltage Range VCC regulating IVIN VIN Input Supply Current Not switching, VIN = 24V, VFB = 0.7V IVIN VIN Input Supply Current (XR76203) f=300kHz, RON=215k, VFB=0.58V 12 mA IVIN VIN Input Supply Current (XR76205) f=300kHz, RON=215k, VFB=0.58V 15 mA IVIN VIN Input Supply Current (XR76208) f=300kHz, RON=215k, VFB=0.58V 19 mA IOFF Shutdown Current Enable = 0V, VIN = 12V 1 A 5.5 0.7 Enable and Under-Voltage Lock-Out UVLO VIH_EN_1 EN Pin Rising Threshold VEN_H_1 EN Pin Hysteresis VIH_EN_2 EN Pin Rising Threshold for DCM/ CCM operation VEN_H_2 EN Pin Hysteresis (c) 2015 Exar Corporation 1.8 1.9 2.0 70 2.8 3.0 100 2 / 20 V mV 3.1 V mV exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Symbol Parameter Conditions VCC UVLO Start Threshold, Rising Edge Min Typ Max Units 4.00 4.25 4.40 V VCC UVLO Hysteresis 230 mV Reference Voltage VIN = 5.5V to 40V, VCC regulating VREF 0.596 0.600 0.604 V 0.594 0.600 0.606 V Reference Voltage VIN = 5.5V to 40V, VCC regulating DC Line Regulation CCM, closed loop, VIN=5.5V-40V, applies to any COUT 0.33 % DC Load Regulation CCM, closed loop, applies to any COUT 0.39 % Programmable Constant On-Time On-Time 1 RON = 237k, VIN = 40V 1570 1840 2120 ns f Corresponding to On-Time 1 VOUT= 24V, VIN = 40V, RON = 237k 283 326 382 kHz TON(MIN) Minimum Programmable On-Time RON = 14k, VIN = 40V TON2 On-Time 2 RON = 14k, VIN = 24V 174 205 236 ns TON3 On-Time 3 RON = 35.7k, VIN = 24V 407 479 550 ns f Corresponding to On-Time 3 VOUT = 3.3V, VIN = 24V, RON = 35.7k 250 287 338 kHz f Corresponding to On-Time 3 VOUT = 5.0V, VIN = 24V, RON = 35.7k 379 435 512 kHz 250 350 ns TON1 120 Minimum Off-Time ns Diode Emulation Mode Zero Crossing Threshold DC value measured during test -2 mV Soft-start -14 Fault present 1 VIN = 6V to 40V, ILOAD = 0 to 30mA 4.8 5.0 VIN = 5V, ILOAD = 0 to 20mA 4.51 4.7 -10 -6.9 -5 % 1.6 4 % SS Charge Current SS Discharge Current -10 -6 A mA VCC Linear Regulator 5.2 V VCC Output Voltage V Power Good Output Power Good Threshold Power Good Hysteresis Power Good Sink Current 1 mA Protection: OCP, OTP, Short-Circuit Hiccup Timeout 110 ILIM Pin Source Current 45 ILIM Current Temperature Coefficient 55 0.4 OCP Comparator Offset (c) 2015 Exar Corporation 50 ms 3 / 20 -8 0 A %/C +8 mV exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Symbol Parameter Conditions Min Typ Max Units Current Limit Blanking GL rising>1V 100 ns Thermal Shutdown Threshold1 Rising temperature 150 C 15 C Thermal Hysteresis1 VSCTH Feedback Pin Short-Circuit Threshold Percent of VREF, short circuit is active after PGOOD is asserted 50 60 70 % 115 160 m 40 59 m XRP76203 Output Power Stage High-Side MOSFET RDSON IDS = 1A RDSON Low-Side MOSFET RDSON IOUT Maximum Output Current 3A A XRP76205 Output Power Stage High-Side MOSFET RDSON Low-Side MOSFET RDSON IOUT 42 59 m 40 59 m IDS = 2A RDSON Maximum Output Current 5A A XRP76208 Output Power Stage High-Side MOSFET RDSON RDSON Low-Side MOSFET RDSON IOUT 42 59 m 16.2 21.5 m IDS = 2A Maximum Output Current 8A A Note 1: Guaranteed by design (c) 2015 Exar Corporation 4 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Pin Configuration, Top View BST SW PVIN PVIN PVIN PVIN PVIN PVIN 30 29 28 27 26 25 24 23 PVIN PAD ILIM 1 EN 2 21 PVIN TON 3 20 SW SS 4 19 PGND PGOOD 5 18 PGND PGND 17 PAD PGND 16 PGND 15 PGND FB 6 AGND 7 (c) 2015 Exar Corporation 22 PVIN SW PAD AGND PAD 8 9 10 11 12 13 14 VIN VCC AGND SW SW SW SW 5 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Pin Assignments Pin No. Pin Name Type Description 1 ILIM A Over-current protection programming. Connect with a resistor to SW. 2 EN/MODE I Precision enable pin. Pulling this pin above 1.9V will turn the regulator on and it will operate in CCM. If the voltage is raised above 3.0V then the regulator will operate in DCM/CCM depending on load 3 TON A Constant on-time programming pin. Connect with a resistor to AGND. 4 SS A Soft-Start pin. Connect an external capacitor between SS and AGND to program the soft-start rate based on the 10uA internal source current. 5 PGOOD O, OD Power-good output. This open-drain output is pulled low when VOUT is outside the regulation. 6 FB A Feedback input to feedback comparator. Connect with a set of resistors to VOUT and AGND in order to program VOUT. AGND A Signal ground for control circuitry. Connect AGND Pad with a short trace to pins 7 and 10. 8 VIN A Supply input for the regulator's LDO. Normally it is connected to PVIN. 9 VCC A The output of regulator's LDO. For operation using a 5V rail, VCC should be shorted to VIN. 11-14, 20, 29, SW Pad SW PWR Switch node. Drain of the low-side N-channel MOSFET. Source of the high-side MOSFET is wire-bonded to the SW Pad. Pins 20 and 29 are internally connected to SW pad. 15-19, PGND Pad PGND PWR Ground of the power stage. Should be connected to the system's power ground plane. Source of the low-side MOSFET is wire-bonded to PGND Pad. 21-28, PVIN Pad PVIN PWR Input voltage for power stage. Drain of the high-side N-channel MOSFET. 30 BST A 7, 10, AGND Pad High-side driver supply pin. Connect a bootstrap capacitor between BST and pin 29. Type: A = Analog, I = Input, O = Output, I/O = Input/Output, PWR = Power, OD = Open-Drain (c) 2015 Exar Corporation 6 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Functional Block Diagram VCC TON VCC UVLO Enable LDO VIN 4.25 V LDO BST PVIN Switching Enabled + - VCC VCC OTP TJ 150 C PGOOD 10uA SS + + FB 0.6V - current emulation & DC correction VIN On-Time - Switching Enabled 0.6 V Feedback comparator FB - R Q S Q PGOOD comparator + 0.555 V Dead Time Control Minimum On Time - + - GL R Q S Q Enable Hiccup Hiccup Mode Enable LDO EN/MODE + 1.9 V Enable LDO - If four consecutive OCP CCM or CCM/DCM + 3V SW VCC Switching Enabled Short-circuit detection 0.36 V GH TON + - If 8 consecutive ZCD Then DCM If 1 non-ZCD Then exit DCM OCP comparator 50uA + - Zero Cross Detect SW + -2 mV - AGND (c) 2015 Exar Corporation 7 / 20 ILIM PGND exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Typical Performance Characteristics 3.340 3.340 3.330 3.330 3.320 3.320 3.310 3.310 VOUT (V) VOUT (V) Unless otherwise noted: VIN = 24V, VOUT=3.3V, IOUT=8A, f=400kHz, TA = 25C. Schematic from the application information section. 3.300 3.290 3.300 3.290 3.280 3.280 3.270 3.270 3.260 3.260 0 2 4 6 5 8 10 15 20 25 30 35 40 VIN (V) IOUT (A) Figure 2: Line regulation Figure 1: Load Regulation 1,500 1,000 Calculated Typical 1,300 Calculated Typical TON (ns) TON (ns) 1,100 100 900 700 500 300 100 10 1 10 5 100 10 15 Figure 3: TON versus RON 25 30 35 40 Figure 4: TON versus VIN, RON=27.4k 600 600 500 500 400 400 f (kHz) f (kHz) 20 VIN (V) RON (k) 300 300 200 200 100 100 0 0 0 2 4 6 5 8 15 20 25 30 35 40 Figure 6: frequency versus VIN Figure 5: frequency versus IOUT (c) 2015 Exar Corporation 10 VIN (V) IOUT (A) 8 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Typical Performance Characteristics Unless otherwise noted: VIN = 24V, VOUT=3.3V, IOUT=8A, f=400kHz, TA = 25C. Schematic from the application information section. 8 14 12 IOCP (A) IOCP (A) 6 10 8 4 6 2 4 0 2 2 3 4 5 4 6 5 7 8 Figure 8: XR76205 IOCP versus RLIM Figure 7: XR76208 IOCP versus RLIM 5 70 4 60 3 ILIM (uA) IOCP (A) 6 RLIM (k) RLIM (k) 2 50 40 1 30 0 2.5 3.0 3.5 4.0 -40 -20 0 4.5 RLIM (k) 20 40 60 80 100 120 TJ (C) Figure 9: XR76203 IOCP versus RLIM Figure 10: ILIM versus temperature 530 610 520 510 500 TON (ns) VREF (mV) 605 600 490 480 470 460 595 450 440 430 590 -40 -20 0 -40 -20 0 20 40 60 80 100 120 TJ (C) TJ (C) Figure 12: TON versus temperature, RON=35.7k Figure 11: VREF versus temperature (c) 2015 Exar Corporation 20 40 60 80 100 120 9 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Typical Performance Characteristics Unless otherwise noted: VIN = 24V, VOUT=3.3V, IOUT=8A, f=400kHz, TA = 25C. Schematic from the application information section. Figure 13: Steady state, IOUT=8A Figure 14: Steady state, DCM, IOUT=0A Figure 15: Power up, Forced CCM Figure 16: Power up, DCM/CCM Figure 17: Load step, Forced CCM, 0A-4A-0A Figure 18: Load step, DCM/CCM, 0A-4A-0A (c) 2015 Exar Corporation 10 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Efficiency 100 98 96 94 92 90 88 86 84 82 80 78 76 74 72 70 3.3uH 2.2uH Efficiency % Efficiency % Unless otherwise noted: TAMBIENT = 25C, No Air flow, f=400kHz, Inductor losses are included, Schematic from the application information section. 1.5uH 5.0V DCM 3.3V DCM 1.8V DCM 0.1 5.0V CCM 3.3V CCM 1.8V CCM 1.0 100 98 96 94 92 90 88 86 84 82 80 78 76 74 72 70 10.0 200kHz, 8.2uH 3.3uH 2.2uH 1.5uH 0.1 IOUT (A) 3.3uH Efficiency % Efficiency % 4.7uH 2.2uH 72 70 0.1 5.0V DCM 5.0V CCM 3.3V DCM 3.3V CCM 1.8V DCM 1.8V CCM 1.0 100 98 96 94 92 90 88 86 84 82 80 78 76 74 72 70 10.0 Efficiency % Efficiency % 3.3uH 72 70 0.1 1.0 5.0V CCM 3.3V CCM 1.8V CCM 6.8uH 3.3uH 2.2uH 100 98 96 94 92 90 88 86 84 82 80 78 76 74 72 70 12V DCM 12V CCM 5.0V DCM 5.0V CCM 3.3V DCM 3.3V CCM 1.8V DCM 1.8V CCM 1.0 10.0 200kHz 10uH 6.8uH 4.7uH 3.3uH 12V DCM 5.0V DCM 3.3V DCM 1.8V DCM 0.1 10.0 1.0 12V CCM 5.0V CCM 3.3V CCM 1.8V CCM 10.0 IOUT (A) IOUT (A) Figure 24: XR76203 efficiency, VIN=24V Figure 23: XR76203 efficiency, VIN=12V (c) 2015 Exar Corporation 10.0 IOUT (A) 4.7uH 5.0V DCM 3.3V DCM 1.8V DCM 1.0 Figure 22: XR76205 efficiency, VIN=24V 6.8uH 82 80 78 76 74 1.8V CCM 4.7uH 0.1 Figure 21: XR76205 efficiency, VIN=12V 92 90 88 86 84 3.3V CCM 1.8V DCM 200kHz IOUT (A) 100 98 96 94 5.0V CCM 3.3V DCM Figure 20: XR76208 efficiency, VIN=24V 100 98 96 84 82 80 78 76 74 12V CCM 5.0V DCM IOUT (A) Figure 19: XR76208 efficiency, VIN=12V 94 92 90 88 86 12V DCM 11 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Thermal Derating 130 130 120 120 110 110 TAMBIENT(C) TAMBIENT(C) Unless otherwise noted: No Air flow, f=400kHz, Schematic from the application information section. 100 90 1.8 VOUT 3.3 VOUT 80 100 200kHz 90 1.8 VOUT 80 3.3 VOUT 5.0 VOUT 70 70 60 60 5.0 VOUT 12 VOUT 50 50 1 2 3 4 5 6 7 1 8 2 3 4 130 130 120 120 110 110 TAMBIENT(C) TAMBIENT(C) 7 8 Figure 26: XR76208, VIN=24V Figure 25: XR76208, VIN=12V 100 90 1.8 VOUT 100 200kHz 90 80 1.8 VOUT 3.3 VOUT 3.3 VOUT 70 6 IOUT (A) IOUT (A) 80 5 70 5.0 VOUT 5.0 VOUT 12 VOUT 60 60 50 50 1 2 3 4 5 1 2 IOUT (A) 130 120 120 110 110 TAMBIENT(C) TAMBIENT(C) 5 Figure 28: XR76205, VIN=24V 130 100 90 1.8 VOUT 100 200kHz 90 1.8 VOUT 80 3.3 VOUT 3.3 VOUT 70 4 IOUT (A) Figure 27: XR76205, VIN=12V 80 3 70 5.0 VOUT 5.0 VOUT 12 VOUT 60 60 50 50 1.0 1.5 2.0 2.5 1.0 3.0 2.0 2.5 3.0 IOUT (A) IOUT (A) Figure 30: XR76203, VIN=24V Figure 29: XR76203, VIN=12V (c) 2015 Exar Corporation 1.5 12 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Functional Description XR76203, XR76205 and XR76208 are synchronous stepdown proprietary emulated current-mode Constant OnTime (COT) regulators. The on-time, which is programmed via RON, is inversely proportional to VIN and maintains a nearly constant frequency. The emulated current-mode control is stable with ceramic output capacitors. derived from VIN. If VIN is well regulated, use a resistor divider and set the voltage to 4V. If VIN varies over a wide range, the circuit shown in figure 32 can be used to generate the required voltage. Each switching cycle begins with GH signal turning on the high-side (control) FET for a preprogrammed time. At the end of the on-time, the high-side FET is turned off and the low-side (synchronous) FET is turned on for a preset minimum time (250ns nominal). This parameter is termed Minimum Off-Time. After the minimum off-time, the voltage at the feedback pin FB is compared to an internal voltage ramp at the feedback comparator. When VFB drops below the ramp voltage, the high-side FET is turned on and the cycle repeats. This voltage ramp constitutes an emulated current ramp and makes possible the use of ceramic capacitors, in addition to other capacitor types, for output filtering. V IN RZ 10k R1 30.1k, 1% Zener MMSZ4685T1G or Equivalent EN/MODE R2 35.7k, 1% Figure 31: Selecting Forced CCM by deriving EN/MODE from VIN Enable/Mode Input (EN/MODE) EN/MODE pin accepts a tri-level signal that is used to control turn on/off. It also selects between two modes of operation: `Forced CCM' and `DCM/CCM'. If EN is pulled below 1.8V, the Regulator shuts down. A voltage between 2.0V and 2.8V selects the Forced CCM mode which will run the Regulator in continuous conduction at all times. A voltage higher than 3.1V selects the DCM/CCM mode which will run the Regulator in discontinuous conduction at light loads. Selecting the Forced CCM Mode V In order to set the Regulator to operate in Forced CCM, a voltage between 2.0V and 2.8V must be applied to EN/ MODE. This can be achieved with an external control signal that meets the above voltage requirement. Where an external control is not available, the EN/MODE can be derived from VIN. If VIN is well regulated, use a resistor divider and set the voltage to 2.5V. If VIN varies over a wide range, the circuit shown in figure 31 can be used to generate the required voltage. Note that at VIN of 5.5V and 40V the nominal Zever voltage is 4.0V and 5.0V respectively. Therefore for VIN in the range of 5.5V to 40V, the circuit shown in figure 31 will generate VEN required for Forced CCM. Selecting the DCM/CCM Mode In order to set the Regulator operation to DCM/CCM, a voltage between 3.1V and 5.5V must be applied to EN/MODE pin. If an external control signal is available, it can be directly connected to EN/MODE. In applications where an external control is not available, EN/MODE input can be (c) 2015 Exar Corporation 13 / 20 IN RZ 10k V EN EN/MODE Zener MMSZ4685T1G or Equivalent Figure 32: Selecting DCM/CCM by deriving EN/MODE from VIN exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Programming the On-Time IOCP is the over-current threshold to be programmed The On-Time TON is programmed via resistor RON according to following equation: RDS is the MOSFET rated On Resistance; XR76208=21.5m, XR76205=59m, XR76203=59m 8mV is the OCP comparator maximum offset -9 V IN T ON - 25 10 R ON = ----------------------------------------------------------- 10 3.05 10 ILIM is the internal current that generates the necessary OCP comparator threshold (use 45A). Note that ILIM has a positive temperature coefficient of 0.4%/C (figure 10). This is meant to roughly match and compensate for positive temperature coefficient of the synchronous FET. Graph of typical IOCP versus RLIM is shown in figure 7-9. Maximum allowable RLIM for XR76205 is 8.06k. where TON is calculated from: V OUT T ON = -----------------------------V IN f Eff Short-Circuit Protection (SCP) f is the desired switching frequency at nominal IOUT If the output voltage drops below 60% of its programmed value, the Module will enter hiccup mode. Hiccup will persist until short-circuit is removed. SCP circuit becomes active after PGOOD asserts high. Eff is the Regulator efficiency corresponding to nominal IOUT shown in figures 19-24 Over-Temperature (OTP) where: OTP triggers at a nominal die temperature of 150C. The gate of switching FET and synchronous FET are turned off. When die temperature cools down to 135C, soft-start is initiated and operation resumes. Substituting for TON in the first equation we get: V OUT- -9 ------------- f Eff - 25 10 V IN R ON = ------------------------------------------------------------------------ 10 3.05 10 Programming the Output Voltage Use an external voltage divider as shown in the Application Circuit to program the output voltage VOUT. V OUT - 1 R1 = R2 ------------ 0.6 Over-Current Protection (OCP) If load current exceeds the programmed over-current, IOCP, for four consecutive switching cycles, the Module enters hiccup mode of operation. In hiccup, the MOSFET gates are turned off for 110ms (hiccup timeout). Following the hiccup timeout, a soft-start is attempted. If OCP persists, hiccup timeout will repeat. The Module will remain in hiccup mode until load current is reduced below the programmed IOCP . In order to program the over-current protection, use the following equation: where R2 has a nominal value of 2k. Programming the Soft-start Place a capacitor CSS between the SS and AGND pins to program the soft-start. In order to program a soft-start time of TSS, calculate the required capacitance CSS from the following equation: I OCP RDS + 8mVRLIM = ----------------------------------------------------ILIM 10A CSS = TSS -------------- 0.6V Where: RLIM is resistor value for programming IOCP (c) 2015 Exar Corporation 14 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Feed-Forward Capacitor (CFF) A feed-forward capacitor (CFF) may be necessary depending on the Equivalent Series Resistance (ESR) of COUT. If only ceramic output capacitors are used for COUT then a CFF is necessary. Calculate CFF from: 1 C FF = ------------------------------------------------2 R1 7 f LC where: R1 is the resistor that CFF is placed in parallel with fLC is the frequency of output filter double-pole fLC frequency must be less than 11kHz when using ceramic COUT. If necessary, increase L and/or COUT in order to meet this constraint. When using capacitors with higher ESR, such as PANASONIC TPE series, a CFF is not required provided following conditions are met: 1. The frequency of output filter LC double-pole fLC should be less than 11kHz. 2. The frequency of ESR Zero fZero,ESR should be at least five times larger than fLC. Note that if fZero,ESR is less than 5xfLC, then it is recommended to set the fLC at less than 2kHz. CFF is still not required. Maximum Allowable Voltage Ripple at FB pin Note that the steady-state voltage ripple at feedback pin FB (VFB,RIPPLE) must not exceed 50mV in order for the Regulator to function correctly. If VFB,RIPPLE is larger than 50mV then COUT should be increased as necessary in order to keep the VFB,RIPPLE below 50mV. Feed-Forward Resistor (RFF) Poor PCB layout can cause FET switching noise at the output and may couple to the FB pin via CFF. Excessive noise at FB will cause poor load regulation. To solve this problem place a resistor RFF in series with CFF. RFF value up to 2% of R1 is acceptable. (c) 2015 Exar Corporation 15 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Application Circuit, XR76208 OPTIONAL CSNB 0.56nF RSNB 1 Ohm CBST 1uF 24VIN 23 PVIN 24 PVIN 25 PVIN 26 PVIN 27 PVIN 28 SW PVIN 30 29 BST 31 PGND FB PGND AGND PGND SW 2x 10uF/50V 22 21 20 19 18 17 16 15 SW 14 8 PGND 13 7 PGOOD VIN FB PGND XR76208 SW 6 SS SW 10k PVIN SW U1 12 R5 TON AGND 5 VCC CIN PVIN 11 4 47nF EN VCC 3 9 CSS 28k 10 RON ILIM AGND PAD 2 PGND PAD 5.49k 1 PVIN PAD SW RLIM 32 18.2k SW PAD R3 34 2k 33 R4 IHLP-5050FD-01 2.2uH 400kHz, 3.3V @ 0-8A COUT CIN 0.1uF PVIN CFF 0.27nF R1 9.09k 3x 47uF/10V FB CVCC 4.7uF R2 2k (c) 2015 Exar Corporation 16 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Application Circuit, XR76205 OPTIONAL CSNB 0.33nF RSNB 1 Ohm CBST 24VIN 23 PVIN 24 PVIN 25 PVIN 26 PVIN 27 PVIN 28 SW PVIN 30 29 BST 31 PGND FB PGND AGND PGND SW 1x 10uF/50V 22 21 20 19 18 17 16 15 SW 14 8 PGND 13 7 PGOOD VIN FB PGND XR76205 SW 6 SS SW 10k PVIN SW U1 12 R5 TON AGND 5 VCC CIN PVIN 11 4 47nF EN VCC 3 9 CSS 29.4k 10 RON ILIM AGND PAD 2 PGND PAD 8.06k 1 PVIN PAD SW RLIM 32 18.2k SW PAD R3 34 2k 33 R4 1uF Wurth-74437368033 3.3uH 400kHz, 3.3V @ 0-5A COUT CIN1 0.1uF PVIN CFF 0.27nF R1 9.09k 2x 47uF/10V FB CVCC 4.7uF R2 2k (c) 2015 Exar Corporation 17 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Application Circuit, XR76203 23 PVIN 24 PVIN 25 PVIN 27 26 PVIN PVIN PVIN 28 29 SW 30 BST 31 32 PGOOD PGND FB PGND AGND PGND SW SW 22 10uF/50V 21 20 19 18 17 16 15 SW 14 8 PGND 13 7 PGND XR76203 VIN FB SS 12 6 10k PVIN SW U1 SW R5 TON 11 5 VCC CIN PVIN AGND 4 EN VCC 47nF 3 9 CSS 28k 10 2 RON ILIM AGND PAD 4.02k 1 PVIN PAD SW RLIM 24VIN PGND PAD 18.2k 33 R3 SW PAD 2k 34 R4 1uF SW CBST Wurth-74437368047 4.7uH 400kHz, 3.3V @ 0-3A COUT CIN1 0.1uF PVIN CFF 0.22nF 47uF/10V R1 9.09k FB CVCC 4.7uF R2 2k (c) 2015 Exar Corporation 18 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Mechanical Dimensions (c) 2015 Exar Corporation 19 / 20 exar.com/XR76203/5/8 Rev 1A XR76203/5/8 Ordering Information Part Number Package JEDEC Compliant Operating Temperature Range XR76208EL-F Packaging Marking Tray XR76208ELTR-F 5x5mm QFN Yes -40C to +125C XR76208ELMTR-F Tape and Reel 76208E YYWWF XXXXXX Mini Tape and Reel XR76208EVB XR76208 Evaluation Board XR76205EL-F Tray XR76205ELTR-F 5x5mm QFN Yes -40C to +125C XR76205ELMTR-F Tape and Reel 76205E YYWWF XXXXXX Mini Tape and Reel XR76205EVB XR76205 Evaluation Board XR76203EL-F Tray XR76203ELTR-F 5x5mm QFN Yes -40C to +125C XR76203ELMTR-F Tape and Reel 76203E YYWWF XXXXXX Mini Tape and Reel XR76203EVB XR76203 Evaluation Board "YY" = Year (last two digits)- "WW" = Work Week- "X" = Lot Number; when applicable Revision History Revision Date 1A February 2015 Description ECN: 1509-04 Feb 2015 For Further Assistance: Technical Support: techsupport.exar.com Technical Documentation: www.exar.com/techdoc Exar Corporation Headquarters and Sales Offices 48720 Kato Road Tel.: +1 (510) 668-7000 Fremont, CA 95438 - USA Fax: +1 (510) 668-7001 NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained herein are only for illustration purposes and may vary depending upon a user's specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited. (c) 2015 Exar Corporation 20 / 20 exar.com/XR76203/5/8 Rev 1A Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Exar: XR76208EL-F XR76208ELTR-F XR76208ELMTR-F XR76208EVB XR76205EL-F XR76205ELTR-F XR76205ELMTR-F XR76205EVB XR76203EL-F XR76203ELTR-F XR76203ELMTR-F XR76203EVB