FA7622CP(E)
1
FA7622CP(E)
s
Dimensions, mm
SSOP-20
1
7.2
10
11
20
5.3
0.6
0~10
0.65
7.9
0.3
0.1
0.1
0.3
0.2
+
0
.1
0
.05
2.1max
DIP-20
1
20
11
10
24.4
6.4
7.62
3.6
5.1max
1.52
0.77
2.54min
0.51min
0~15
0~15
0.46
0.1
2.54
0.25
0.25
+0.1
0.05
Bipolar IC
For Switching Power Supply Control
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.
s
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.
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)
s
Applications
Battery power supply for portable equipment
+
-
+
-
+
-
+
-
FB1
ON/OFF 19
17
IN1+
3
CP
IN2+
4
REF
DT1
CT
RT VCC1
SW
20
16
1
2
14
13
BIAS
OSC
UVLO
Duty
limit
OCP
12
VCC2
15
OCL1
11
OUT1
-
PWM1
ER, AMP1
VB
ER, AMP2
PWM2
Duty
limit
OCP
10
OUT2
OCL2
8
GND
DT2
7
6
5
IN2-
FB2
-
Timer
&
latch
18
9
SW
Pin
Pin
Description
No.
symbol
1
CT
Oscillator timing capacitor
2
RT
Oscillator timing resistor
3
CP
Timer and latch circuit
4
IN2+
Non-inverting input to error
amplifier
5
IN2-
Inverting input to error amplifier
6
FB2
Error amplifier output
7
DT2
Dead time adjustment
8
OCL2
Overcurrent limiting circuit 2
9
GND
Ground
10
OUT2
CH.2 output
11
OUT1
CH.1 output
12
VCC2
Power supply 2
13
SW
Switch for boost circuit
14
VCC1
Power supply 1
15
OCL1
Overcurrent limiting circuit 1
16
DT1
Dead time adjustment
17
FB1
Error amplifier output
18
IN1+
Non-inverting input to error
amplifier
19
ON/OFF
Output ON/OFF control
20
REF
Reference voltage output
s
Block diagram
FA7622CP(E)
2
s
Electrical characteristics (Ta = 25
C, V
CC
= 6V, R
T
= 36k
, C
T
= 180pF)
Reference voltage section
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Output voltage
V
REF
I
OR
= 1mA
2.400
2.475
2.550
V
Line regulation
L
INE
V
CC
= 3.6 to 26V,
I
OR
= 1mA
5
15
mV
Load regulation
L
OAD
I
OR
= 0.1 to 1mA
2
mV
Output voltage variation due to temperature change
V
TC1
T
a = 30 to +25
C
1
1
%
V
TC2
T
a = +25 to +85
C
1
1
%
Oscillator section
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Oscillation frequency
f
OSC
C
T
= 180pF,
R
T
= 36k
100
110
120
kHz
Frequency variation 1 (due to supply voltage change)
f
dV
V
CC
= 3.6 to 26V
1
%
Frequency variation 2 (due to temperature change)
f
dT
T
a
= 30 to +25
C
5
%
Error amplifier section (ch. 1)
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Reference voltage
V
B
0.832
0.858
0.884
V
Input bias current
I
B
5
100
nA
Open-loop voltage gain
A
VO
40
dB
Unity-gain bandwidth
f
T
1.0
MHz
Maximum output voltage
V
OH
No load
1.8
V
V
OL
No load
300
mV
Output source current
I
OH
V
OH
=
0V
30
60
90
A
Error amplifier section (ch. 2)
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Input offset voltage
V
IO
2
10
mV
Input bias current
I
B
5
100
nA
Common-mode input voltage
V
COM
0
1.0
V
Open-loop voltage gain
A
VO
70
dB
Unity-gain bandwidth
f
T
1.0
MHz
Maximum output voltage
V
OH
No load
1.8
V
V
OL
No load
300
mV
Output source current
I
OH
V
OH
= 0V
40
80
120
A
s
Absolute maximum ratings
Item
Symbol
Rating
Unit
Supply
V
CC1
28
V
voltage
V
CC1
20
V
Supply voltage
V
CC2
28
V
ON/OFF pin voltage
V
ON/OFF
0.3 to +7
V
Out pin output current
I
OUT
600
mA
Total power dissipation
P
d
650
mW
Junction temperature
T
j
125
C
Operating temperature
T
opr
30 to +85
C
Storage temperature
T
stg
40 to +150
C
Voltage boost
circuit not used
Voltage boost
circuit used
s
Recommended operating conditions
Item
Symbol
Min.
Max.
Unit
V
CC1
3.6
26
V
V
CC1
3.6
18
V
R
NF
100
k
C
T
50
2200
pF
R
T
24
100
k
f
OSC
50
1000
kHz
Supply
voltage
Feedback resistance
Timing capacitance
Timing resistance
Oscillation frequency
Voltage boost
circuit not used
Voltage boost
circuit used
FA7622CP(E)
3
Pulse width modulation circuit section ( FB1, FB2 pin )
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Input threshold voltage
V
THO
Duty cycle = 0%
1.6
1.8
V
Input threshold voltage
V
THI
Duty cycle = 100%
0.8
1.0
V
Dead time adjustment circuit section ( DT1, DT2 pin )
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Input threshold voltage
V
TH0
Duty cycle = 0%
1.6
1.8
V
Input threshold voltage
V
TH1
Duty cycle = 100%
0.8
1.0
V
Standby voltage
V
STR
DT1, DT2 pin open
1.8
V
Overcurrent limiting circuit section
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Input threshold voltage
V
THOC
180
210
240
mV
Hysteresis voltage
V
HYOC
40
mV
Input bias current
I
OC
50
100
A
Delay in OCL
t
doc
Overdriving: 50mV
120
ns
Timer and latch circuit section
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Latch-mode threshold voltage
V
THCP
1.00
1.25
1.50
V
Input bias current
I
INCP
V
CP
= 1.5V,
V
FB
= 0.3V
1
A
CP pin voltage / LOW
V
SATC
I
CP
= 20
A,
V
FB
= 1.0V
300
mV
Output ON/OFF control circuit section
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
OFF-to-ON threshold voltage
V
THON
3.0
V
ON-to-OFF threshold voltage
V
TH OFF
0.60
V
Input bias current
I
IN
V
IN
= 3V
180
A
Undervoltage lock-out circuit section
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
OFF-to-ON threshold voltage
V
CCON
2.80
3.00
3.20
V
ON-to-OFF threshold voltage
V
CCOF
2.90
V
Voltage hysteresis
V
HYS
0.10
V
Output section
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Saturation voltage (H level)
V
SAT+
I
O
= 50mA
1.50
2.00
V
Saturation voltage (L level)
V
SAT
I
O
= 50mA
1.70
2.20
V
Voltage step-up circuit section
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Output voltage
V
OUP
L=330
H, C=1
F, No load
10.5
12.5
14.0
V
Overall device
Item
Symbol
Test condition
Min.
Typ.
Max.
Unit
Stand-by supply current
I
CCST
Out pin open
0.1
10
A
Operating V
CC1
current
I
CC1
Normal operation
3.8
5.5
mA
Operating V
CC2
current
I
CC2
Normal operation V
CC2
=12V
1.5
2.2
mA
OUT1, OUT2 open
Duty cycle=50%
FA7622CP(E)
4
1. Oscillator section
This section charges and discharges an external capacitor C
T
.
The charge current is determined by the external resistor R
T
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:
f
OSC
( kH
z
)
7.1 10
5
R
T
( k
) C
T
( pF )
(1)
......................
2. Error amplifier section
Error amplifier
As Fig. 3 shows, the inverting input of the error amplifier is
connected to the V
B
reference voltage (0.858V typ.). The non-
inverting input IN1+ and output FB1 connect to external
terminals.
During ordinary operation, the IN1+ terminal voltage is almost
equal to V
B
. The power-supply output V
OUTA
can be
determined as follows:
V
OUTA
R
1
+ R
2
R
2
(2)
....................................
V
B
The DC gain of the error amplifier is 40dB (typ.), regardless of
external parts connected to the IC. Correct the phase by
connecting capacitor C
1
between the V
OUTA
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 V
OUTB
to the IN2+ pin can be
determined as follows:
V
OUTB
( R
3
+ R
4
) R
6
R
4
( R
5
+ R
6
)
(3)
........................
V
REF
The DC gain A
V
from the V
OUTB
to FB2 pin is 70dB (min),
when R
7
is not connected.
When R
7
is connected, the A
V
can be determined as follows:
A
V
R
4
R
3
+ R
4
(4)
...........
1 +
R
7
(R
5
+ R
6
)
R
5
R
6
Fig. 3
To correct the phase, connect the resistor R8 and capacitor C2
in series between the IN2 and FB2 pins.
Fig. 4
Fig. 1 Oscillator
1
2
RT
CT
C
T
V =1.0 (V)
RT
I =
CT
1.0 (V)
R
T
R
T
1.0V
1.6V
CT pin voltage waveform
O S C
1
REF
CT
C
T
20
9
GND
I
V : 1.0
1.6V
CT
CT
I
V : 1.6
1.0V
CT
CT
Fig. 2
10
20
6
R3
V
OUTB
FB2
ER.AMP2
C2
R4
R6
R5
IN2
IN2
REF
Q2
R8
R7
5
4
+
-
(Controlled by Q2)
OUT2
R1
18
17
11
V
OUTA
R2
FB1
IN1
ER.AMP1
Q1
C1
+
(Controlled by Q1)
V
B
36k
OUT1
s
Description of each circuit
FA7622CP(E)
5
Inverting chopper circuit
According to the circuit shown in Fig. 5, the power output
voltage V
OUTB
can be determined as follows:
V
OUTB =
R
11
R
10
(5)
..............................
V
REF
The A
V
between the V
OUTB
and FB2 pins can be determined
as follows:
A
V
R
11
R
12
(6)
.................................................
To correct the phase, connect the resistor R
13
and capacitor
C
3
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).
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
C
T
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 C
T
voltage, the
PWM output is high. When it is higher than C
T
, 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 C
T
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. 5
Fig. 8
Fig. 6
C3
Q3
FB2
R10
R9
REF
R11
R12
R13
IN2
IN2
ER.AMP2
V
CC1
+
-
V
OUTB
(Controlled by Q3)
10
20
6
5
4
OUT2
PWM output
FB1(FB2)
DT1(DT2)
Time
CT
PWM output
PWM1
(PWM2)
DT1(DT2)
FB1(FB2)
CT
Fig. 7
DT1(DT2)
20
1
FB1(FB2)
C
S
CT
R
S
REF
PWM output
PWM1
(PWM2)
20
1
DT1(DT2)
FB1(FB2)
C
S
CT
R
S2
REF
PWM output
PWM1
(PWM2)
R
S1
Fig.8:
t
S
(m
S
) = CS ln
R
S1
0.417R
S1
0.583 R
S2
(7)
.................................
Fig.7:
t
S
(m
S
) = 0.54C
S
R
S
Where, R
S1
/
R
S2
> 0.716
(8)
......
R
S1
R
S2
R
S1
R
S2
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.
FA7622CP(E)
6
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 t
L
from when the circuit is overloaded until the power
supply is cut off can be determined as follows:
(9)
.................
t
L
(m
S
) = 0.67C
P
(
F) R
CP
(k
)
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 V
CC1
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 V
REF
. (This reduces the duty-cycle to
0%)
This circuit has hysteresis to prevent noise from causing
malfunction.
The R
S
voltage which is propotional to drain current is limited
to 210mV (typ.) and released at 170mV (typ).
Fig. 9
Fig. 10
Fig. 11
Fig. 12
OUT1
(OUT2)
OCL1
(OCL2)
VCC1
-0.21V
REF
DT1
(DT2)
VCC1
D
I
Rs
OUT1
(OUT2)
Time
VCC1
VCC1
-0.2V
OCL1
(OCL2)
(Similar to I
D
)
Voltage waveforms
PWM output
FB1(FB2)
DT1(DT2)
Time
CP
CT
1.25V
(Threshold voltage
of CP pin)
Voltage waveforms
20
1.25V
C
P
S1
REF
OUT1
(OUT2)
R
CP
FB1
(FB2)
0.3V
CP
FA7622CP(E)
7
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 10
A 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 100
H or more and the capacitor (Cup)
should be greater than about 0.1
F.
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.
Fig. 14 Control of output
Fig. 16
ON/OFF
3.0V
0.6V
OUT1
(OUT2)
I
D
Fig. 13
OUT1
(OUT2)
Time
0V
ON/OFF
3.0V
Voltage waveforms
14
13
12
VCC1
VCC2
SW
L
D
C
UP
R E G U L A T O R
Fig. 15
GND
OUT1
(OUT2)
VCC2
FA7622CP(E)
8
s
Application circuit
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.
+
+
+
+
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
REF ON/OFF IN1+
FB1
DT1
OCL1 VCC1
SW
OUT1
VCC2
OUT2
GND
OCL2
DT2
FB2
IN2-
IN2+
CP
RT
CT
F A 7 6 2 2 P ( M )
2.2k
10.6k
470k
683
683
684
330
472
330
683
1
10
0.33
47k
100
33
VIN
5.5~9V
5V
47
12V
100
33
0.33
47k
10
330
472
120k
470k
3.3k
102
360k
510k
683
180p
3.3K
100k
ON/OFF
1
64k
36k
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