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Número de pieza | FA3641N | |
Descripción | PWM control IC with light load power saving function For Switching Power Supply Control | |
Fabricantes | Fuji Electric | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de FA3641N (archivo pdf) en la parte inferior de esta página. Total 21 Páginas | ||
No Preview Available ! FA3641P(N), FA3647P(N)FA3641P(N), FA3647P(N)
PWM control IC with light load power saving function
For Switching Power Supply Control
s Description
The FA3641P(N) and FA3647P(N) are the PWM type switching
power supply control ICs that can directly drive power MOSFET.
These ICs use a CMOS device with high dielectric strength
(30V) to implement low power consumption. They feature a
number of functions that are equivalent to those of the FA531X
series consisting of bipolar devices. In addition, they have a
function that reduces the oscillation frequency to suppress loss
of the power supply in light load mode and support an
overvoltage protection detecting Vcc voltage. These ICs are
most suitable for high-performance, energy-saving power
supplies that require low input power in standby or no-load
mode.
s Features
• Uses a newly developed CMOS process with high dielectric
strength (30V) for implementing low power consumption
• Standby current of 2µA or less (at Vcc=14V), and operating
current of 1.9mA (typ.)
• Automatically reduces the oscillation frequency to suppress
loss of the power supply in light load mode
• Overvoltage protection function detecting Vcc voltage
• A drive circuit for connecting a power MOSFET directly
• Output peak current: Source current –500mA
Sink current
+1A
• Pulse-by-pulse overcurrent limiting function
• Overload cutoff function (latch or non-latch mode selectable)
• Output ON/OFF control function by external signal
• Latch mode overvoltage shutdown function
• Undervoltage lockout function
(16.5V ON / 9V OFF)
• Reference voltage output (5V)
• 8-pin package (DIP/SOP)
s Dimensions, mm
SOP-8
85
14
4.9
0.4±0.1 1.27±0.2
DIP-8
8
5
1 9.3 4
1.5
2.54±0.25 0.46±0.1
7.62
0~15˚
0.25+–00.1.05
0~15˚
58
1 page FA3641P(N), FA3647P(N)
s Characteristic curves (Ta=25˚C)
Oscillation frequency (fosc) vs.
timing resistor resistance (RT)
1000
100
VCC = 18V
FB = 1.5V
10
1 10 100
Rt [kΩ]
Oscillation frequency (fosc) vs.
junction temperature (Tj)
105
Rt = 47kΩ
104 FB = 2.5V
103
102
101
100
99
98
97
–50
0 50 100
Tj [°C]
Supply current (Icc) vs. supply voltage (Vcc)
Operating mode
2
1000
150
1.95
1.9
1.85
1.8
1.75
10
Rt = 47kΩ
FB = 0V
15
20
Vcc [V]
62
25
30
Oscillation frequency (fosc) vs. supply voltage (Vcc)
105
104
103
102
101
100
99
98
97
96
95
10
OUT = No load
Rt = 47 kΩ
FB = Open, CS = 3V
15 20
Vcc [V]
25
30
L-level output vltage (VOL) vs. supply voltage (Vcc)
1
0.8
0.6
0.4
0.2
Io = 100 mA
0
10 15 20
Vcc [V]
25
30
Supply current (Icc) vs. junction temperature (Tj)
Operating mode
2
1.95
1.9
1.85
1.8
1.75
–50
Rt = 47kΩ
Vcc = 18V
FB = 0V
0
50
Tj [°C]
100
150
5 Page FA3641P(N), FA3647P(N)
5. Overcurrent limiting circuit
The overcurrent limiting circuit detects the peak value of every
drain current pulse (pulse by pulse method) of the main
switching MOSFET to limit the overcurrent. The detection
threshold voltage is +0.235V for FA3641 or –0.168V for FA3647
with respect to the ground as shown in Figure 14.
The drain current of the MOSFET is converted to voltage by
resistor Rs and fed to the IS pin of the IC. If the voltage
exceeds the reference voltage +0.235V (FA3641) or –0.168V
(FA3647) of comparator C4, comparator C4 works to set flip-
flop output Q to high. The output is immediately turned off to
shut off the current. Flip-flop output Q is reset on the next cycle
to turn on the output again. This operation is repeated to limit
the overcurrent.
If the overcurrent limiting circuit malfunctions due to noise,
place an RC filter between the IS pin and MOSFET as shown in
Figure 14. (See item 14 in “Design advice.”)
Figure 15 is a timing chart that illustrates overcurrent-limiting
operations.
6. Vcc overvoltage protection circuit
The IC contains a Vcc overvoltage protection circuit to protect
the IC from damage by overvoltage. Figure 16 shows the
overvoltage protection circuit. Figure 17 is a timing chart that
illustrates overvoltage protection operations.
Overvoltage is detected if the supply voltage Vcc rises to 32V
(Icc = 13mA) or more and current flows in the built-in zener
diode. The output of comparator C5 then goes high and the
constant current source (0.9mA) raises the CS pin voltage.
When the CS pin voltage exceeds 8.5V, the output of
comparator C2 goes high to turn off the 5V REF circuit. The IC
then enters the latched mode and the IC output is put in the off
(low voltage) state. When latched mode, the IC current
consumption is 45µA (typ) (Vcc = 10V). This current must be
supplied through the startup resistor.
The overvoltage shutdown operation can be reset by lowering
the supply voltage to below 9.0V or forcing the CS pin voltage
below 7.9V.
(When you want to enable Vcc overvoltage shutdown at a
desired voltage, see item 7 in “Design advice.”
Fig. 14 Overcurrent limiting circuit
Fig. 15 Overcurrent timing chart
Fig. 16 Overvoltage shutdown circuit
68
Fig. 17 Overvoltage shutdown timing chart
11 Page |
Páginas | Total 21 Páginas | |
PDF Descargar | [ Datasheet FA3641N.PDF ] |
Número de pieza | Descripción | Fabricantes |
FA3641 | PWM control IC with light load power saving function For Switching Power Supply Control | Fuji Electric |
FA3641 | FA3641 | Fuji Electric |
FA3641N | PWM control IC with light load power saving function For Switching Power Supply Control | Fuji Electric |
FA3641P | PWM control IC with light load power saving function For Switching Power Supply Control | Fuji Electric |
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