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FA3635P
FA3635P
CMOS IC
For Switching Power Supply Control
■ Description
FA3635P is a CMOS IC which includes low on-resistance
power MOSFET for PWM-type switching power supply control.
This IC achieves high efficiency DC-DC converter and it is
suitable for buck converter or inverting converter with high
input voltage of 10V to 50V.
■ Features
• Built-in low on-resistance Pch power MOSFET
50V/1.1Ω(typ.)/1A(peak)
• Wide range of 10V to 50V for input voltage
• 1.2mA low operating current as a Power IC
• Latch-mode short-circuit protection function
• Built-in over-temperature protection
Tj =125°C (min.)
■ Applications
• Power supply for general equipment
■ Block diagram
■ Dimensions, mm
Á DIP-8
8
1
2.54
±0.25
9.4
1.5
0.5
5
4
±0.1
6.5
3.4
4.5max
3.1min
0~15˚
7.6
0.25
0~15˚
+0.1
–0.05
Pin Pin Description
No. symbol
1 VCC Power supply
2 FB Error amplifier output
3 IN Inverting input to error amplifier
4 GND Ground
5 GND Ground
6 REF Reference voltage
7 CS Capacitor for soft-start
8 OUT Output
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FA3635P
■ Absolute maximum ratings
Item Symbol Rating Unit
Supply voltage
Error amplifier input voltage
Total Power dissipation
(Ta = 25°C)
Junction temperature
Operating temperature Top –20 to +85°C °C
Storage temperature Tstg –40 to +150 °C
VCC 50.0 V
VIN 5.5 V
Pd 1.1 W
Tj 125 °C
■ Recommended operating conditions
Item Symbol Min. Max. Unit
Supply voltage VCC 10.0 45.0 V
REF terminal by-pass capacitor
VCC terminal by-pass capacitor
CREF
0.047
0.22 µF
CO 470 µF
■ Electrical characteristics (Ta=25°C, VCC=44V, CREF=0.1µF)
Reference voltage section
Item Symbol Test condition Min. Typ. Max. Unit
terminal Voltage VREG CREF=0.1µF 3.00 3.12 3.24 V
Oscillator section
Item Symbol Test condition Min. Typ. Max. Unit
Oscillation frequency fOSC 70 81 100 kHz
Frequency change with supply voltage fdV VCC=10 to 45V ±1 ±3%
Frequency change with temperature fdT Ta=–20 to +85°C ±3 ±5%
Error amplifier section
Item Symbol Test condition Min. Typ. Max. Unit
Input common mode voltage range VICOM 0.2 2.5 V
Open-loop gain AVOL 55 dB
Unity-gain bandwidth fT 1.0 MHz
Output sink current IFBL Voltage follower 3.0 3.8 mA
VFB=Vref+0.05V
Output source current IFBH Voltage follower –140 –100 µA
VFB=Vref–0.05V
Reference Voltage Vref Voltage follower 0.97 1.00 1.03 V
VCC=10 to 45V
Ta=–20 to +85°C
Input threshold voltage (Pin 2) VFB 0 Duty cycle=0% 0.5 0.6 0.7 V
VFB 100 Duty cycle=100% 2.3 2.5 2.7 V
Soft-start circuit section
Item Symbol Test condition Min. Typ. Max. Unit
Input threshold voltage (Pin 7) VCS 0 Duty cycle=0% 0.5 0.6 0.7 V
VCS 100 Duty cycle=100% 2.3 2.5 2.7 V
Charge current ICS –2.8 –2.2 –1.6 µA
Undervoltage lockout circuit section
Item Symbol Test condition Min. Typ. Max. Unit
Operating voltage VUVLO 5.0 6.1 8.5 V
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FA3635P
Overheat protection section
Item Symbol Test condition Min. Typ. Max. Unit
Operating temperature TOH 125 135 145 °C
Hysteresis width ∆TOH 45 50 55 °C
Output section
Item Symbol Test condition Min. Typ. Max. Unit
Voltage drop VDROP IOUT=1.0A 1.1 1.4 V
IOUT=0.7A 0.7 0.9
IOUT=0.1A 0.1 0.2
Overcurrent limit IOLMT Peak current 1.0 1.75 2.0 A
Overall device
Item Symbol Test condition Min. Typ. Max. Unit
Operating current ICC Out pin open, VCC=44V 0.9 4.0 mA
Duty cycle=100%
■ Characteristic curve
Á Thermal characteristic
1.6
1.4
1.2
1
0.8
LOSS [W]
0.6
0.4
0.2
0
0
Thermal resistance : θj-c(Junction to case) = 30°C/W
θj-a(Junction to air) = 90°C/W
50
Ambient temperature [°C]
100
150
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■ Characteristic curves (Ta=25°C)
Output duty cycle vs. FB terminal voltage (VFB) Output duty cycle vs. CS terminal voltage (VCS)
FA3635P
100
90
80
70
60
50
40
30
Output duty cycle [%]
20
10
0
0 0.5 1 1.5 2 2.5 3
100
90
80
70
60
50
40
30
Output duty cycle [%]
20
10
0
0 0.5 1 1.5 2 2.5 3
VFB [V]
Oscillation frequency (fOSC) vs. ambient temperature (Ta) Reference voltage
100
95
90
85
fosc [kHz]
80
75
VREF [V]
1.05
1.04
1.03
1.02
1.01
1
0.99
0.98
VCS [V]
(VREF)
vs. ambient temperature (Ta)
70
20
20
40
0
60
100
80
Ta [°C]
0.97
40
60
20
20
0
80 100
Ta [°C]
Output voltage (VOUT) vs. output current (IOUT) Supply current (ICC) vs. supply voltage (VCC)
1.8
1.6
1.4
1.2
1
0.8
VCC– VOUT [V]
0.6
0.4
0.2
0
0 0.2 0.4
IOUT [A]
0.6
0.8
1
2
1.5
1
Icc [mA]
0.5
0
0
10
20
30
40
Vcc [V]
50
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FA3635P
Error amplifier voltage gain (AV)/ phase (θ) vs. frequency (f)
Condition: Open loop
180
160
140
120
[deg]
Av [dB]
100
– 20
– 40
80
60
40
20
0
10
100
Voltage gain
1K
10K
ƒ [HZ]
Phase
100K 1M
10M
■ 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.
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