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FA7622CP(E) FA7622CP(E)
s Description
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.
Bipolar IC For Switching Power Supply Control
s Dimensions, mm SSOP-20
20 11
* 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)
0.10.1
7.2
+0.1 0.2 -0.05
1
10
5.3
s Features
7.90.3
0~10
0.6
0.3
0.65
DIP-20
20 11
s Applications
* Battery power supply for portable equipment
1 0.77
24.4
10 1.52
2.54min 5.1max 3.6
0.51min
6.4
2.1max
0.25
+0.1 5 -0.0
7.62
5 0~1
2.540.25
0.460.1
0~15
s Block diagram
REF 20 DT1 16 CT 1 RT VCC1 2 14 SW 13 SW ON/OFF 19 BIAS OSC UVLO 12 VCC2 Pin No. 1 2 3 4 5 FB1 17 IN1+ 18 VB CP IN2+ IN2FB2 3 ER, AMP2 + + ER, AMP1 Duty limit + OCP 15 OCL1 6 7 11 PWM1 OUT1 8 9 10 11 12 + 10 PWM2 OCP 9 GND 8 OCL2 OUT2 13 14 15 16 17 18 19 20 Pin symbol Description Oscillator timing capacitor Oscillator timing resistor Timer and latch circuit Non-inverting input to error amplifier Inverting input to error amplifier Error amplifier output Dead time adjustment Overcurrent limiting circuit 2 Ground CH.2 output CH.1 output Power supply 2 Switch for boost circuit Power supply 1 Overcurrent limiting circuit 1 Dead time adjustment Error amplifier output Non-inverting input to error amplifier Output ON/OFF control Reference voltage output
CT RT CP IN2+ IN2FB2 DT2 OCL2 GND OUT2 OUT1 VCC2 SW VCC1 OCL1 DT1 FB1 IN1+ ON/OFF REF
Timer & latch
4 5 6
Duty limit 7 DT2
1
FA7622CP(E)
s Absolute maximum ratings
Item Supply voltage Voltage boost circuit not used Voltage boost circuit used Supply voltage ON/OFF pin voltage Out pin output current Total power dissipation Junction temperature Operating temperature Storage temperature Symbol Rating 28 20 28 -0.3 to +7 600 650 125 -30 to +85 -40 to +150 Unit V V V V mA mW C C C
s Recommended operating conditions
Item Supply voltage Voltage boost circuit not used Voltage boost circuit used Feedback resistance Timing capacitance Timing resistance Oscillation frequency Symbol Min. 3.6 3.6 100 50 24 50 2200 100 1000 Max. 26 18 Unit V V k pF k kHz
VCC1 VCC1 VCC2 VON/OFF IOUT Pd Tj Topr Tstg
VCC1 VCC1 RNF CT RT fOSC
s Electrical characteristics (Ta = 25C, VCC = 6V, RT = 36k, CT = 180pF) Reference voltage section
Item Output voltage Line regulation Load regulation Output voltage variation due to temperature change Symbol Test condition Min. 2.400 Typ. 2.475 5 2 -1 -1 1 1 Max. 2.550 15 Unit V mV mV % %
VREF LINE LOAD VTC1 VTC2
IOR = 1mA VCC = 3.6 to 26V, IOR = 1mA IOR = 0.1 to 1mA Ta = -30 to +25C Ta = +25 to +85C
Oscillator section
Item Oscillation frequency Frequency variation 1 (due to supply voltage change) Frequency variation 2 (due to temperature change) Symbol Test condition Min. 100 Typ. 110 1 5 Max. 120 Unit kHz % %
fOSC fdV fdT
CT = 180pF, RT = 36k VCC = 3.6 to 26V Ta = -30 to +25C
Error amplifier section (ch. 1)
Item Reference voltage Input bias current Open-loop voltage gain Unity-gain bandwidth Maximum output voltage Output source current Symbol Test condition Min. 0.832 Typ. 0.858 5 40 1.0 No load No load 1.8 300 30 60 90 Max. 0.884 100 Unit V nA dB MHz V mV
VB IB AVO fT VOH VOL IOH
VOH = 0V
A
Error amplifier section (ch. 2)
Item Input offset voltage Input bias current Common-mode input voltage Open-loop voltage gain Unity-gain bandwidth Maximum output voltage Output source current Symbol Test condition Min. Typ. 2 5 0 70 1.0 No load No load VOH = 0V 40 80 1.8 300 120 Max. 10 100 1.0 Unit mV nA V dB MHz V mV
VIO IB VCOM AVO fT VOH VOL IOH
A
2
FA7622CP(E)
Pulse width modulation circuit section ( FB1, FB2 pin )
Item Input threshold voltage Input threshold voltage Symbol Test condition Duty cycle = 0% Duty cycle = 100% 0.8 Min. Typ. 1.6 1.0 Max. 1.8 Unit V V
VTHO VTHI
Dead time adjustment circuit section ( DT1, DT2 pin )
Item Input threshold voltage Input threshold voltage Standby voltage Symbol Test condition Duty cycle = 0% Duty cycle = 100% DT1, DT2 pin open 0.8 1.8 Min. Typ. 1.6 1.0 Max. 1.8 Unit V V V
VTH0 VTH1 VSTR
Overcurrent limiting circuit section
Item Input threshold voltage Hysteresis voltage Input bias current Delay in OCL Symbol Test condition Min. 180 Typ. 210 40 50 Overdriving: 50mV 120 100 Max. 240 Unit mV mV
VTHOC VHYOC IOC tdoc
A
ns
Timer and latch circuit section
Item Latch-mode threshold voltage Input bias current CP pin voltage / LOW Symbol Test condition Min. 1.00 Typ. 1.25 Max. 1.50 1 300 Unit V
VTHCP IINCP VSATC
VCP = 1.5V, VFB = 0.3V ICP = 20 A, VFB = 1.0V
A
mV
Output ON/OFF control circuit section
Item OFF-to-ON threshold voltage ON-to-OFF threshold voltage Input bias current Symbol Test condition Min. 0.60 Typ. Max. 3.0 Unit V V 180
VTHON VTH OFF IIN
VIN = 3V
A
Undervoltage lock-out circuit section
Item OFF-to-ON threshold voltage ON-to-OFF threshold voltage Voltage hysteresis Symbol Test condition Min. 2.80 Typ. 3.00 2.90 0.10 Max. 3.20 Unit V V V
VCCON VCCOF VHYS
Output section
Item Saturation voltage (H level) Saturation voltage (L level) Symbol Test condition Min. Typ. 1.50 1.70 Max. 2.00 2.20 Unit V V
VSAT+ VSAT-
IO = -50mA IO = 50mA
Voltage step-up circuit section
Item Output voltage Symbol Test condition L=330H, C=1F, No load Min. 10.5 Typ. 12.5 Max. 14.0 Unit V
VOUP
Overall device
Item Stand-by supply current Operating VCC1 current Operating VCC2 current Symbol Test condition Out pin open Normal operation Normal operation VCC2=12V OUT1, OUT2 open Duty cycle=50% Min. Typ. 0.1 3.8 1.5 Max. 10 5.5 2.2 Unit
ICCST ICC1 ICC2
A
mA mA
3
FA7622CP(E)
s Description of each circuit
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: 7.1 * 105 fOSC ( kHz ) RT ( k ) * CT ( pF )
1.6V 1.0V
CT pin voltage waveform
CT CT
1 2
RT
RT
OSC
V RT =1.0 (V) I CT = 1.0 (V) RT
Fig. 1 Oscillator
...................... (1)
REF
20
2. Error amplifier section Error amplifier 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: R1 + R2 VOUTA R2
I CT V CT : 1.0 1.6V CT
1
CT I CT V CT : 1.6 1.0V
9
*VB .................................... (2)
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. Error amplifier * 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: ( R3 + R4 ) * R6 VOUTB R4 * ( R5 + R6 )
Fig. 2 VOUTA (Controlled by Q1) FB1
17
C1 R1 R2 VB IN1+
18
36k
Q1
11
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: R4 AV R3 + R4 * 1+ R7 * (R5 + R6) R5 * R6
VOUTB (Controlled by Q2) REF
20
........... (4)
R3 R4
R5 IN2 + 4 IN2 R6 R7 R8 C2
6
Q2
10
To correct the phase, connect the resistor R8 and capacitor C2 in series between the IN2- and FB2 pins.
5
ER.AMP2
OUT2
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
R10 R9 R11
R12
VCC1 REF
20
Q3 IN2+ IN2 R13 C3
6 4
10
* VREF .............................. (5)
5
OUT2
The AV between the VOUTB and FB2 pins can be determined as follows: -R11 AV R12
ER.AMP2
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) CT
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: F for Cs and k for Rs, Rs1, and Rs2) Fig.7: tS (mS) = 0.54CS * RS ................................. (7) Fig.8: tS (mS) = CS RS1 * RS2 RS1 RS2 RS1 0.417RS1 - 0.583 RS2
PWM output Time
CT DT1(DT2) FB1(FB2)
PWM output PWM1 (PWM2) Fig. 6
REF
20
CT
1
CS DT1(DT2) RS FB1(FB2) PWM output PWM1 (PWM2)
Fig. 7
* ln
......(8)
CS RS1 CT
1
REF
20
Where, RS1 / RS2 > 0.716 DT1(DT2) RS2 FB1(FB2)
PWM output PWM1 (PWM2)
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.
Fig. 8
5
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: tL (mS) = 0.67CP (F) * RCP (k) ................. (9)
REF
20
RCP
FB1 (FB2) 0.3V CP S1
OUT1 (OUT2)
CP 1.25V
Fig. 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) CP PWM output Time CT 1.25V (Threshold voltage of CP pin)
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)
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 10A 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 100H or more and the capacitor (Cup) should be greater than about 0.1F. 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.
ON/OFF
ID
3.0V 0.6V
OUT1 (OUT2)
Fig. 13
Voltage waveforms 3.0V ON/OFF 0V
OUT1 (OUT2) Fig. 14 Control of output
Time
L VCC1
D SW 13 VCC2 CUP
12
14
REGULATOR
Fig. 15
VCC2
OUT1 (OUT2)
GND Fig. 16
7
FA7622CP(E)
s Application circuit
2.2k 10.6k 683 684 ON/OFF
19 20 18 REF ON/OFF IN1+ 17 FB1 16 DT1 15 14 OCL1 VCC1 13 SW 12
VIN + 0.33 100 5.5~9V
683 470k 683
330 472 330 1 + 10 33 5V
11
47k
+
VCC2 OUT1
47
FA7622P(M) CT
1
RT
2
CP
3
IN2+ IN24 5
FB2
6
DT2 OCL2 GND OUT2
7 8 9 10
0.33
180p
36k 100k
1
102
472 330 100 120k 12V
3.3k 360k 510k 683
470k
10 47k
+ 33
3.3K
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

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