Bipolar IC For Switching Power Supply Control FA7622CP(E) FA7622CP(E) ■ Description ■ Dimensions, mm The FA7622CP(E) is a DC-DC converter IC that can directly drive a power MOSFET. This IC has all the necessary protection functions for a power MOSFET. It is optimum for a portable equipment power supply which uses low-voltage input to output comparably large power. Á SSOP-20 0.1±0.1 7.2 +0.1 0.2 –0.05 10 1 0.3 0~10˚ • Drive circuit for connecting a power MOSFET (Io = ±600mA) • Built-in voltage step-up circuit to drive a power MOSFET gate: A converter circuit requires only an N-channel power MOSFET. • Dual control circuit • Overcurrent limiting circuit • Overload cutoff circuit with timer and latch circuit • ON/OFF control pin • Wide operating range: 3.6 to 28V • High-frequency operation: up to 1MHz • 20-pin package (DIP/SSOP) 2.1max 5.3 ■ Features 7.9±0.3 11 20 0.65 0.6 Á DIP-20 11 20 ■ Applications 6.4 • Battery power supply for portable equipment 10 24.4 1.52 0.51min 3.6 0.77 0.46±0.1 2.54±0.25 2.54min 5.1max 1 +0.1 5 –0.0 0.25 7.62 0~15 ˚ 5˚ 0~1 ■ Block diagram DT1 CT RT VCC1 SW Pin No. Pin symbol Description REF 20 16 1 2 13 1 CT Oscillator timing capacitor 2 RT Oscillator timing resistor 3 CP IN2+ Timer and latch circuit 4 5 IN2- Inverting input to error amplifier 6 FB2 Error amplifier output 7 DT2 Dead time adjustment 8 Overcurrent limiting circuit 2 9 OCL2 GND 10 OUT2 CH.2 output 11 OUT1 CH.1 output 12 VCC2 Power supply 2 13 SW VCC1 Switch for boost circuit 14 15 OCL1 Overcurrent limiting circuit 1 16 DT1 Dead time adjustment 9 17 FB1 Error amplifier output GND 18 IN1+ Non-inverting input to error amplifier 19 ON/OFF Output ON/OFF control 20 REF Reference voltage output 14 SW OSC BIAS ON/OFF 19 Duty limit FB1 17 IN1+ 18 VB CP IN2+ + - + ER, AMP1 IN2- 5 FB2 6 ER, AMP2 + + - - 15 11 OCL1 OUT1 PWM1 10 OUT2 PWM2 Duty limit 7 DT2 1 OCP VCC2 Timer & latch 3 4 12 UVLO 8 OCP OCL2 Non-inverting input to error amplifier Ground Power supply 1 FA7622CP(E) ■ Absolute maximum ratings Item Supply voltage ■ Recommended operating conditions Symbol Rating Unit Voltage boost circuit not used VCC1 28 V Voltage boost circuit used VCC1 20 V VCC2 VON/OFF 28 V Feedback resistance –0.3 to +7 V Timing capacitance IOUT Pd Tj Topr Tstg ±600 mA Timing resistance 650 mW Oscillation frequency 125 °C –30 to +85 °C –40 to +150 °C Supply voltage ON/OFF pin voltage Out pin output current Total power dissipation Junction temperature Operating temperature Storage temperature Item Symbol Min. Max. Unit Supply voltage Voltage boost circuit not used VCC1 3.6 26 V Voltage boost circuit used VCC1 3.6 18 V RNF CT 100 50 2200 pF RT fOSC 24 100 kΩ 50 1000 kHz kΩ ■ Electrical characteristics (Ta = 25°C, VCC = 6V, RT = 36kΩ, CT = 180pF) Reference voltage section Item Symbol Test condition Min. Typ. Max. Unit Output voltage VREF IOR = 1mA 2.400 2.475 2.550 V Line regulation LINE LOAD VTC1 VTC2 VCC = 3.6 to 26V, IOR = 1mA IOR = 0.1 to 1mA Ta = –30 to +25°C Ta = +25 to +85°C 5 15 Item Symbol Test condition Min. Oscillation frequency fOSC fdV fdT CT = 180pF, RT = 36kΩ VCC = 3.6 to 26V Ta = –30 to +25°C 100 Item Symbol Test condition Reference voltage VB IB AVO fT Load regulation Output voltage variation due to temperature change 2 mV mV –1 1 % –1 1 % Typ. Max. Unit 110 120 Oscillator section Frequency variation 1 (due to supply voltage change) Frequency variation 2 (due to temperature change) kHz 1 % 5 % Error amplifier section (ch. 1) Input bias current Open-loop voltage gain Unity-gain bandwidth Min. Typ. Max. Unit 0.832 0.858 0.884 V 5 100 VOH VOL IOH No load VOH = 0V 30 Item Symbol Test condition Min. Input offset voltage VIO IB VCOM AVO fT Maximum output voltage Output source current nA 40 dB 1.0 MHz 1.8 V No load 300 mV 60 90 µA Typ. Max. Unit 2 10 mV 5 100 nA 1.0 V Error amplifier section (ch. 2) Input bias current Common-mode input voltage Open-loop voltage gain Unity-gain bandwidth Maximum output voltage Output source current VOH VOL IOH 0 70 dB 1.0 No load 1.8 V No load VOH = 0V MHz 40 80 300 mV 120 µA 2 FA7622CP(E) Pulse width modulation circuit section ( FB1, FB2 pin ) Item Symbol Test condition Input threshold voltage VTHO VTHI Duty cycle = 0% Input threshold voltage Min. Duty cycle = 100% 0.8 Min. Typ. Max. Unit 1.6 1.8 V 1.0 V Dead time adjustment circuit section ( DT1, DT2 pin ) Item Symbol Test condition Input threshold voltage VTH0 VTH1 VSTR Duty cycle = 0% Item Symbol Test condition Input threshold voltage VTHOC VHYOC IOC tdoc Overdriving: 50mV Item Symbol Test condition Latch-mode threshold voltage VTHCP IINCP VSATC VCP = 1.5V, VFB = 0.3V ICP = 20 µA, VFB = 1.0V Item Symbol Test condition OFF-to-ON threshold voltage VTHON VTH OFF IIN VIN = 3V Item Symbol Test condition OFF-to-ON threshold voltage VCCON VCCOF VHYS Input threshold voltage Standby voltage Duty cycle = 100% 0.8 DT1, DT2 pin open 1.8 Typ. Max. Unit 1.6 1.8 V 1.0 V V Overcurrent limiting circuit section Hysteresis voltage Input bias current Delay in OCL Min. Typ. Max. Unit 180 210 240 mV 40 50 mV 100 120 µA ns Timer and latch circuit section Input bias current CP pin voltage / LOW Min. Typ. 1.00 1.25 Max. Unit 1.50 V 1 µA 300 mV Max. Unit Output ON/OFF control circuit section ON-to-OFF threshold voltage Input bias current Min. Typ. 3.0 0.60 V V µA 180 Undervoltage lock-out circuit section ON-to-OFF threshold voltage Voltage hysteresis Min. Typ. Max. Unit 2.80 3.00 3.20 V 2.90 V 0.10 V Output section Item Symbol Test condition Saturation voltage (H level) VSAT+ VSAT– IO = –50mA IO = 50mA Item Symbol Test condition Min. Output voltage VOUP L=330µH, C=1µF, No load 10.5 Item Symbol Test condition Min. Stand-by supply current ICCST Out pin open Operating VCC1 current ICC1 ICC2 Normal operation Normal operation VCC2=12V OUT1, OUT2 open Duty cycle=50% Saturation voltage (L level) Min. Typ. Max. Unit 1.50 2.00 V 1.70 2.20 V Typ. Max. Unit 12.5 14.0 V Typ. Max. Unit 0.1 10 µA 3.8 5.5 mA 1.5 2.2 mA Voltage step-up circuit section Overall device Operating VCC2 current 3 FA7622CP(E) ■ Description of each circuit CT pin voltage waveform 1. Oscillator section This section charges and discharges an external capacitor CT. The charge current is determined by the external resistor RT connected to the IC. By charging and discharging the capacitor, this section provides a 1.0 to 1.6V triangle wave at the CT pin. The oscillation frequency can be set between 50kHz to 1MHz. The frequency can be calculated approximately as follows: fOSC ( kHz ) ⫽ 1.6V 1.0V CT RT CT 2 1 RT OSC V RT =1.0 (V) I CT = 앐 1.0 (V) RT Fig. 1 Oscillator 7.1 • 105 RT ( kΩ ) • CT ( pF ) ...................… (1) REF 20 2. Error amplifier section Error amplifier ➀ As Fig. 3 shows, the inverting input of the error amplifier is connected to the VB reference voltage (0.858V typ.). The noninverting input IN1+ and output FB1 connect to external terminals. During ordinary operation, the IN1+ terminal voltage is almost equal to VB. The power-supply output VOUTA can be determined as follows: VOUTA ⫽ R1 + R2 I CT V CT : 1.0 → 1.6V CT 1 CT I CT V CT : 1.6 → 1.0V 9 •VB .................................… (2) R2 GND The DC gain of the error amplifier is 40dB (typ.), regardless of external parts connected to the IC. Correct the phase by connecting capacitor C1 between the VOUTA and FB1 pins. Fig. 2 V OUTA (Controlled by Q1) Error amplifier ➁ • Voltage step-up or step-down chopper circuit As Fig. 4 shows, the non-inverting input IN2+, inverting input IN2–, and output FB2 of the error amplifier are connected to external terminals. The feedback voltage VOUTB to the IN2+ pin can be determined as follows: VOUTB ⫽ ( R3 + R4 ) • R6 R4 • ( R5 + R6 ) FB1 17 36kΩ C1 IN1+ R1 Q1 ⫹ 18 11 R2 ⫺ VB OUT1 ER.AMP1 • VREF ..................…… (3) Fig. 3 The DC gain AV from the VOUTB to FB2 pin is 70dB (min), when R7 is not connected. When R7 is connected, the AV can be determined as follows: V OUTB (Controlled by Q2) REF 20 AV ⫽ R7 • (R5 + R6) R4 R3 + R4 • 1+ R5 • R6 ........... (4) To correct the phase, connect the resistor R8 and capacitor C2 in series between the IN2– and FB2 pins. R5 R3 IN2 + 4 IN2 - R4 5 R6 R7 R8 C2 Q2 ⫹ 10 ⫺ ER.AMP2 OUT2 6 FB2 Fig. 4 4 FA7622CP(E) • Inverting chopper circuit According to the circuit shown in Fig. 5, the power output voltage VOUTB can be determined as follows: R11 VOUTB = – R10 V CC1 REF 20 • VREF .............................. (5) AV ⫹ R12 IN2+ IN2 - R9 R11 The AV between the VOUTB and FB2 pins can be determined as follows: –R11 Q3 R10 4 ⫹ 5 ⫺ R13 R12 10 OUT2 ER.AMP2 C3 6 FB2 V OUTB (Controlled by Q3) ................................................. (6) Fig. 5 To correct the phase, connect the resistor R13 and capacitor C3 in series between the IN2– and FB2 pins. By using this circuit, invert the output polarity of OUT2 with an external transistor to drive a P-channel MOSFET (or PNP transistor). DT1(DT2) FB1(FB2) 3. PWM comparator section As Fig. 6 shows, a PWM comparator has three input terminals. PWM comparator 1 determines the duty cycle of the output from the OUT1 pin. This comparator compares the CT oscillator Voltage (Pin 1) with the FB1 voltage (Pin 17) or the DT1 voltage (Pin 16), whichever is greater. When the highest of these voltages is lower than the CT voltage, the PWM output is high. When it is higher than CT, the PWM output is low. PWM comparator 2 determines the duty cycle of the output from the OUT2 pin. To determine the PWM output, this comparator compares the CT oscillator voltage (Pin 1) with the FB2 voltage (Pin 6) or the DT2 voltage (Pin 7) whichever is higher. During ordinary operation, the OUT1 and OUT2 pin voltages have the same polarity as the output from each comparator. When the power supply is turned on, the pulse width gradually increases. The time constant for soft-start is determined by the external resistor and capacitor across pins 16 and 7. In Figures 7 and 8, the time ts required for the pulse width (duty-cycle) to reach about 30% after start-up can be determined as follows: (Units: µF for Cs and kΩ for Rs, Rs1, and Rs2) CT PWM output Time ⫹ ⫺ ⫺ CT DT1(DT2) FB1(FB2) PWM output PWM1 (PWM2) Fig. 6 REF 20 CT 1 CS ⫹ ⫺ ⫺ DT1(DT2) RS PWM output PWM1 (PWM2) FB1(FB2) Fig. 7 Fig.7: tS (mS) = 0.54CS • RS ................................. (7) Fig.8: tS (mS) = CS RS1 • RS2 RS1 ⫹ RS2 • ln RS1 0.417RS1 – 0.583 RS2 REF ……(8) 20 CS RS1 Please connect enough large capacitance between REF and GND pins in order to prevent irregular output pulse caused by minus voltage at DT1 or DT2 pin when IC is shut down. CT 1 Where, RS1 / RS2 > 0.716 ⫹ ⫺ ⫺ DT1(DT2) RS2 FB1(FB2) Fig. 8 5 PWM output PWM1 (PWM2) FA7622CP(E) 4. Timer and latch circuit for overload protection Figure 9 shows the timer and latch circuit for overload protection and Fig. 10 shows its timing during an overload. If the power supply output decreases due to an overload, the error amplifier output decreases. If the voltage decreases to less than 0.3V, the switch that clamps the CP pin voltage to the ground disconnects. This charges capacitor Cp from the REF pin through the resistor Rcp and the CP pin voltage increases. When the voltage reaches 1.25V, OUT1 (OUT2) voltage is clamped to ground. The N-channel MOSFET (or NPN transistor) connected to the OUT1 (or OUT2) is turned OFF and cuts off the power supply. The time tL from when the circuit is overloaded until the power supply is cut off can be determined as follows: REF 20 FB1 (FB2) R CP ⫹ ⫺ 0.3V OUT1 (OUT2) CP S1 ⫹ CP ⫺ 1.25V Fig. 9 tL (mS) = 0.67CP (µF) • RCP (kΩ) ................. (9) 5. Overcurrent limiting circuit This is a pulse-by-pulse overcurrent limiting circuit which detects and limits the peak of each drain current pulse from the main switching transistor (MOSFET). Figure 11 shows the overcurrent limiting circuit and Fig. 12 shows its timing. This circuit detects a drain current with a voltage sampling resistor Rs. If a voltage lower than the VCC1 pin voltage by 210mV or more is input to OCL1 (OCL2), the OUT1 (OUT2) is clamped to ground. At the same time, DT1 (DT2) is raised to the reference voltage VREF. (This reduces the duty-cycle to 0%) This circuit has hysteresis to prevent noise from causing malfunction. The RS voltage which is propotional to drain current is limited to 210mV (typ.) and released at 170mV (typ). Voltage waveforms FB1(FB2) DT1(DT2) 1.25V (Threshold voltage of CP pin) CT CP PWM output Time Fig. 10 REF DT1 (DT2) VCC1 OCL1 (OCL2) Rs ID OUT1 (OUT2) ⫺ ⫹ VCC1 -0.21V Fig. 11 Voltage waveforms OCL1 (OCL2) VCC1 VCC1 -0.2V (Similar to ID) OUT1 (OUT2) Time Fig. 12 6 FA7622CP(E) ON/OFF 6. IC ON/OFF control circuit This control circuit turns the entire IC ON or OFF by an external signal using an ON/OFF control pin to limit the IC’s current consumption to 10µA or less. Figure 13 shows the IC ON/OFF control circuit and Fig. 14 shows its timing. To turn the IC OFF, this circuit clamps OUT1 (OUT2) to ground when the ON/OFF pin voltage is controlled to less than 0.60V. The internal bias current is cut off to turn off the switching transistor. To turn the IC ON, raise the ON/OFF pin voltage immediately to 3.0V or more to charge the soft-start capacitor gradually. 7. Voltage boost circuit By using the circuit shown in Fig. 15, this IC generates a voltage 6.5V (typ.) higher than the VCC1 input voltage at the VCC2 pin. This circuit allows the IC to drive MOSFET gates directly. With this circuit, the IC can drive a low-level side N-channel MOSFET at 3.6 to 18V as VCC1 (not possible with conventional ICs). In addition, an N-channel MOSFET can be used on the high-level side of a buck chopper. In Fig. 15, the inductor (L) is about 100µH or more and the capacitor (Cup) should be greater than about 0.1µF. If voltage boost is not necessary, connect the VCC1 and VCC2 pins directly, and SW pin must be opened. 8. Undervoltage lock-out circuit This circuit prevents a malfunction at a low supply voltage. When the supply voltage VCC1 rises and reaches 3.0V, this circuit is activated. When VCC1 drops below 2.9V, this circuit clamps OUT1 (OUT2) to ground. The CP pin voltage is reset to low by means of cutting off a power supply input. 9. Output circuit As Fig. 17 shows, OUT1 and OUT2 with a totempole structure can drive a MOSFET. Since both the maximum output source and sink currents are 600mA, a MOSFET can be switched at high speed. ID ⫺ 3.0V OUT1 (OUT2) ⫹ 0.6V Fig. 13 Voltage waveforms 3.0V ON/OFF 0V OUT1 (OUT2) Time Fig. 14 Control of output L VCC1 14 D SW 13 VCC2 CUP 12 REGULATOR Fig. 15 VCC2 OUT1 (OUT2) GND Fig. 16 7 FA7622CP(E) ■ Application circuit VIN 10.6k 2.2k + 683 684 0.33 5.5~9V 100µ 330 683 470k 472 10 1µ + 330µ 683 ON/OFF 33µ 5V 19 20 18 REF ON/OFF IN1+ 17 FB1 16 DT1 15 14 OCL1 VCC1 13 SW 12 47k 11 + VCC2 OUT1 47µ FA7622P(M) CT RT 2 1 180p IN2+ IN2- CP 3 4 1µ 36k FB2 5 6 DT2 OCL2 GND OUT2 7 8 360k 330 100µ 120k 510k 470k 683 3.3K 0.33 10 472 102 3.3k 100k 9 10 + 12V 33µ 47k 64k Parts tolerances characteristics are not defined in the circuit design sample shown above. When designing an actual circuit for a product, you must determine parts tolerances and characteristics for safe and economical operation. 8