W83320S/W83320G
5. PIN DESCRIPTION
PIN
NAME
FUNCTION
1
2
3
4
5
6
7
8
LGATE
VDD
VDDA
PWROK
GNDA
SS
COMP
FB
Low-Side N-Channel MOSFET Gate Drive Pin. This pin is monitored by the
adaptive shoot-through protection circuitry to determine when the low-side
MOSFET turned off.
+5V supply rail for the lower gate driver and control logic circuit.
VDDA: +5V supply rail for the chip.
Power OK. Open drain output. This pin will be opened in following conditions:
1. No over-current detected; 2. V
REF
_IN >0.6V; 3. FB > 75% of V
REF
_IN; 4. SS
>3V.
Ground for analog circuit. Connect it to system ground.
Soft Start Pin. A capacitor should be attached in this pin to ground for soft start
output clamping. This capacitor, along with an internal 12uA current source,
set the output clamp ramp up speed.
Internal Error Amplifier Output Pin. This pin is available for compensation of
the control loop.
Inverting Input of the Error Amplifier. This pin is available for compensation of
the control loop.
Non-inverting Input of the Error Amplifier. Voltage on this pin provides
reference input to the PWM control loop.
When the V
REF
_IN voltage is less than 0.27V, the PWM is shut-down and the
H_DRV and L_DRV are driven low. Due to its wide input range (0 ~ 3.6V), the
V
REF
_IN voltage can be raised slowly to perform the input clamp function.
Besides, a special function is implemented in this IC to inform the reference
provider of over current alarm. Each time as the OC occurs, V
REF
_IN will be
short to GND (through 170 ohms) for about 5~10uS. The reference provider
can be aware of the OC condition by detecting this pulse.
Internal Bandgap Reference Voltage Output.
Supply rail for the high-side MOSFET driver. A bootstrap circuit may be used
to create a BOOT voltage or a separate 12V supply can be used.
High-Side N-Channel MOSFET Gate Drive Pin. This pin is also monitored by
the adaptive shoot through protection circuitry to determine when the high-side
MOSFET has turned off.
Ground for signal level circuit. Connect it to system ground.
Current limit threshold setting. Connect a resistor (R
OCSET
) between this pin
and the drain of the low-side MOSFET. An internal 72uA current source will
flow through R
ISEN
and cause a fixed voltage drop on it while the low-side
MOSFET is turned on. In the mean while, the W83320S compares the voltage
drop with the voltage across the low-side MOSFET and determines whether
the current limit has been reached. The equation for over-current limit is:
I
LIM
= (72uA * R
ISEN
)/R
DSON
9
V
REF
10
11
12
13
BG_REF
BOOT
UDRV
GND
14
I
SEN
-6-
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