FA7622CPE [FUJI]
Bipolar IC For Switching Power Supply Control; 双极型集成电路开关电源控制
| 型号： | FA7622CPE |
| 厂家： | 
FUJI ELECTRIC |
| 描述： | Bipolar IC For Switching Power Supply Control |
| 文件： | 总8页 (文件大小：70K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Bipolar IC
For Switching Power Supply Control
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
11
20
■ Features
• 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.
10
1
7.2
• Dual control circuit
• Overcurrent limiting circuit
• Overload cutoff circuit with timer and latch circuit
• ON/OFF control pin
0.6
0.3
0.65
• Wide operating range: 3.6 to 28V
• High-frequency operation: up to 1MHz
• 20-pin package (DIP/SSOP)
Á DIP-20
20
11
■ Applications
• Battery power supply for portable equipment
1
10
1.52
24.4
0.77
7.62
2.54±0.25
0.46±0.1
0~15˚
■ Block diagram
Pin Pin
No. symbol
Description
DT1 CT RT VCC1
SW
13
REF
20
1
2
3
4
CT
Oscillator timing capacitor
Oscillator timing resistor
Timer and latch circuit
16
1
2
14
RT
SW
CP
OSC
BIAS
19
VCC2
ON/OFF
12
UVLO
IN2+
Non-inverting input to error
amplifier
5
IN2-
Inverting input to error amplifier
Error amplifier output
Dead time adjustment
Overcurrent limiting circuit 2
Ground
Duty
limit
6
FB2
FB1 17
OCP
OCL1
OUT1
15
11
7
DT2
+
+
8
OCL2
GND
OUT2
OUT1
VCC2
SW
IN1+
18
-
-
9
-
PWM1
VB
ER, AMP1
10
11
12
13
14
15
16
17
18
CH.2 output
Timer
CP
&
3
CH.1 output
latch
Power supply 2
ER, AMP2
+
IN2+
+
OUT2
OCL2
10
8
4
5
6
Switch for boost circuit
Power supply 1
-
-
VCC1
OCL1
DT1
PWM2
-
IN2-
FB2
Duty
limit
Overcurrent limiting circuit 1
Dead time adjustment
Error amplifier output
OCP
7
9
FB1
DT2
GND
IN1+
Non-inverting input to error
amplifier
19
20
ON/OFF Output ON/OFF control
REF Reference voltage output
1
FA7622CP(E)
■ Absolute maximum ratings
■ Recommended operating conditions
Item
Symbol
Rating
Unit
Item
Symbol Min. Max.
Unit
Supply
voltage
Voltage boost
circuit not used
VCC1
28
V
VCC1
3.6
26
V
Voltage boost
circuit not used
Supply
voltage
Voltage boost
circuit used
Voltage boost
circuit used
VCC1
20
V
VCC1
3.6
18
V
Supply voltage
VCC2
VON/OFF
IOUT
Pd
28
V
RNF
CT
100
50
kΩ
pF
Feedback resistance
Timing capacitance
Timing resistance
ON/OFF pin voltage
Out pin output current
Total power dissipation
Junction temperature
Operating temperature
Storage temperature
–0.3 to +7
±600
V
2200
100
mA
mW
°C
°C
°C
RT
24
kΩ
kHz
650
fOSC
50
1000
Oscillation frequency
Tj
125
Topr
Tstg
–30 to +85
–40 to +150
■ Electrical characteristics (Ta = 25°C, VCC = 6V, RT = 36kΩ, CT = 180pF)
Reference voltage section
Item
Symbol
VREF
LINE
Test condition
Min.
Typ.
Max.
2.550
15
Unit
Output voltage
IOR = 1mA
2.400
2.475
V
Line regulation
VCC = 3.6 to 26V,
I
OR = 1mA
5
2
mV
mV
%
Load regulation
LOAD
VTC1
VTC2
IOR = 0.1 to 1mA
Output voltage variation due to temperature change
Ta = –30 to +25°C
Ta = +25 to +85°C
–1
–1
1
1
%
Oscillator section
Item
Symbol
fOSC
fdV
Test condition
Min.
Typ.
110
1
Max.
Unit
kHz
%
Oscillation frequency
CT = 180pF, RT = 36kΩ
VCC = 3.6 to 26V
100
120
Frequency variation 1 (due to supply voltage change)
Frequency variation 2 (due to temperature change)
fdT
Ta = –30 to +25°C
5
%
Error amplifier section (ch. 1)
Item
Symbol
VB
Test condition
Min.
Typ.
0.858
5
Max.
0.884
100
Unit
V
Reference voltage
Input bias current
Open-loop voltage gain
Unity-gain bandwidth
Maximum output voltage
0.832
IB
nA
dB
MHz
V
AVO
fT
40
1.0
VOH
VOL
IOH
No load
No load
VOH = 0V
1.8
30
300
90
mV
µA
Output source current
60
Error amplifier section (ch. 2)
Item
Symbol
VIO
Test condition
Min.
Typ.
Max.
10
Unit
mV
nA
V
Input offset voltage
Input bias current
2
5
IB
100
1.0
Common-mode input voltage
Open-loop voltage gain
Unity-gain bandwidth
Maximum output voltage
VCOM
AVO
fT
0
70
dB
MHz
V
1.0
80
VOH
VOL
IOH
No load
No load
VOH = 0V
1.8
40
300
120
mV
µA
Output source current
2
FA7622CP(E)
Pulse width modulation circuit section ( FB1, FB2 pin )
Item
Symbol
VTHO
Test condition
Duty cycle = 0%
Duty cycle = 100%
Min.
Typ.
1.6
Max.
Unit
V
Input threshold voltage
Input threshold voltage
1.8
VTHI
0.8
1.0
V
Dead time adjustment circuit section ( DT1, DT2 pin )
Item
Symbol
VTH0
Test condition
Duty cycle = 0%
Duty cycle = 100%
DT1, DT2 pin open
Min.
Typ.
1.6
Max.
Unit
V
Input threshold voltage
Input threshold voltage
Standby voltage
1.8
VTH1
0.8
1.8
1.0
V
VSTR
V
Overcurrent limiting circuit section
Item
Symbol
VTHOC
VHYOC
IOC
Test condition
Min.
Typ.
210
40
Max.
Unit
mV
mV
µA
Input threshold voltage
Hysteresis voltage
Input bias current
Delay in OCL
180
240
50
100
tdoc
Overdriving: 50mV
120
ns
Timer and latch circuit section
Item
Symbol
VTHCP
IINCP
Test condition
Min.
Typ.
Max.
1.50
1
Unit
V
Latch-mode threshold voltage
Input bias current
CP pin voltage / LOW
1.00
1.25
VCP = 1.5V, VFB = 0.3V
µA
mV
VSATC
ICP = 20 µA, VFB = 1.0V
300
Output ON/OFF control circuit section
Item
Symbol
VTHON
VTH OFF
IIN
Test condition
Min.
Typ.
Max.
Unit
V
OFF-to-ON threshold voltage
ON-to-OFF threshold voltage
Input bias current
3.0
0.60
V
VIN = 3V
180
µA
Undervoltage lock-out circuit section
Item
Symbol
VCCON
VCCOF
VHYS
Test condition
Min.
Typ.
3.00
2.90
0.10
Max.
Unit
V
OFF-to-ON threshold voltage
ON-to-OFF threshold voltage
Voltage hysteresis
2.80
3.20
V
V
Output section
Item
Symbol
VSAT+
Test condition
Min.
Typ.
1.50
1.70
Max.
2.00
2.20
Unit
V
Saturation voltage (H level)
Saturation voltage (L level)
IO = –50mA
VSAT–
I
O
= 50mA
V
Voltage step-up circuit section
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Output voltage
VOUP
L=330µH, C=1µF, No load
10.5
12.5
14.0
V
Overall device
Item
Symbol
ICCST
ICC1
Test condition
Out pin open
Min.
Typ.
0.1
Max.
10
Unit
µA
Stand-by supply current
Operating VCC1 current
Operating VCC2 current
Normal operation
3.8
5.5
mA
mA
ICC2
Normal operation VCC2=12V
OUT1, OUT2 open
1.5
2.2
Duty cycle=50%
3
FA7622CP(E)
■ Description of each circuit
CT pin voltage waveform
1.6V
1.0V
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
C
T
R
T
CT
RT
2
1
O S C
VRT =1.0 (V)
1.0 (V)
calculated approximately as follows:
I
CT = Ȁ
RT
Fig. 1 Oscillator
7.1 • 105
(1)
...................…
fOSC ( kHz ) ϭ
RT ( kΩ ) • CT ( pF )
REF
20
2. Error amplifier section
I CT
V CT : 1.0
→1.6V
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 non-
inverting input IN1+ and output FB1 connect to external
terminals.
CT
1
During ordinary operation, the IN1+ terminal voltage is almost
equal to VB. The power-supply output VOUTA can be
determined as follows:
CT
I CT
VCT : 1.6
→1.0V
9
R1 + R2
GND
(2)
.................................…
•VB
VOUTA ϭ
R2
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
VOUTA (Controlled by Q1)
FB1
Error amplifier ➁
17
• 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:
36kΩ
C1
+
R1
R2
IN1
Q1
18
ϩ
Ϫ
11
OUT1
VB
ER.AMP1
( R3 + R4 ) • R6
(3)
• VREF ..................……
VOUTB ϭ
R4 • ( R5 + R6 )
Fig. 3
The DC gain AV from the VOUTB to FB2 pin is 70dB (min),
when R7 is not connected.
VOUTB (Controlled by Q2)
When R7 is connected, the AV can be determined as follows:
REF
20
R7 • (R5 + R6)
R5 • R6
R4
(4)
...........
AV ϭ
•
1 +
R5
R3 + R4
R3
R4
+
-
IN2
IN2
Q2
4
5
ϩ
Ϫ
10
To correct the phase, connect the resistor R8 and capacitor C2
in series between the IN2– and FB2 pins.
R8
C2
OUT2
R6
ER.AMP2
R7
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:
VCC1
REF
20
Q3
R10
R11
R11
+
(5)
• VREF ..............................
VOUTB = –
IN2
4
5
ϩ
R10
-
10
IN2
R13
C3
R9
Ϫ
OUT2
ER.AMP2
R12
The AV between the VOUTB and FB2 pins can be determined
as follows:
6
FB2
VOUTB (Controlled by Q3)
–R11
(6)
.................................................
AV ϩ
R12
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)
CT
PWM output
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.
Time
CT
DT1(DT2)
FB1(FB2)
ϩ
Ϫ
Ϫ
PWM output
PWM1
(PWM2)
Fig. 6
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:
REF
20
CT
1
CS
PWM output
ϩ
Ϫ
Ϫ
DT1(DT2)
RS
PWM1
(PWM2)
FB1(FB2)
(Units: µF for Cs and kΩ for Rs, Rs1, and Rs2)
Fig. 7
Fig.7:
(7)
tS (mS) = 0.54CS • RS .................................
Fig.8:
tS (mS) = CS
RS1 • RS2
RS1
REF
• ln
(8)
……
20
RS1 ϩ RS2
0.417RS1 – 0.583 RS2
RS1
CS
CT
1
Where, RS1 / RS2 > 0.716
ϩ
Ϫ
Ϫ
PWM output
DT1(DT2)
RS2
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.
PWM1
(PWM2)
FB1(FB2)
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.
REF
20
FB1
(FB2)
ϩ
Ϫ
RCP
0.3V
S1
OUT1
(OUT2)
CP
ϩ
Ϫ
CP
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:
1.25V
Fig. 9
tL (mS) = 0.67CP (µF) • RCP (kΩ)
(9)
.................
Voltage waveforms
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).
FB1(FB2)
DT1(DT2)
1.25V
(Threshold voltage
of CP pin)
CT
CP
Figure 11 shows the overcurrent limiting circuit and Fig. 12
shows its timing.
PWM output
Time
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%)
Fig. 10
DT1
REF (DT2) VCC1
This circuit has hysteresis to prevent noise from causing
malfunction.
The RS voltage which is propotional to drain current is limited
OCL1
(OCL2)
ID
Rs
to 210mV (typ.) and released at 170mV (typ).
OUT1
Ϫ
(OUT2)
ϩ
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.
ID
Figure 13 shows the IC ON/OFF control circuit and Fig. 14
shows its timing.
Ϫ
ϩ
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.
OUT1
(OUT2)
3.0V
0.6V
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
Fig. 13
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.
Voltage waveforms
3.0V
0V
ON/OFF
OUT1
(OUT2)
Time
If voltage boost is not necessary, connect the VCC1 and VCC2
pins directly, and SW pin must be opened.
Fig. 14 Control of output
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
L
D
CUP
VCC1
SW
VCC2
12
14
13
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.
R E G U L A T O R
Since both the maximum output source and sink currents are
600mA, a MOSFET can be switched at high speed.
Fig. 15
VCC2
OUT1
(OUT2)
GND
Fig. 16
7
FA7622CP(E)
■ Application circuit
VIN
2.2k
10.6k
5.5~9V
+
683
100µ
0.33
330
472
683
470k
684
10
1µ
330µ
683
+
33µ
ON/OFF
5V
47k
+
47µ
20
19
18
17
16
15
OCL1
13
12
11
OUT1
14
REF ON/OFF
IN1+ FB1
DT1
VCC1 SW VCC2
FA7622P(M)
IN2-
5
OCL2 GND OUT2
CP IN2+
FB2 DT2
CT
RT
0.33
6
2
3
4
7
8
9
10
1
102
472
180p
1µ
36k
330
3.3k
100k
100µ
360k
120k
12V
+
10
47k
470k
510k
33µ
683
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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FUJI
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