W83320S Datasheet, PDF (6/18 Pages) Winbond – N-Channel FET Synchronous Buck Regulator Controller

W83320S/W83320G
5. PIN DESCRIPTION
PIN
NAME
FUNCTION
Low-Side N-Channel MOSFET Gate Drive Pin. This pin is monitored by the
1
LGATE adaptive shoot-through protection circuitry to determine when the low-side
MOSFET turned off.
2
VDD +5V supply rail for the lower gate driver and control logic circuit.
3
VDDA VDDA: +5V supply rail for the chip.
Power OK. Open drain output. This pin will be opened in following conditions:
4
PWROK 1. No over-current detected; 2. V_REF_IN >0.6V; 3. FB > 75% of V_REF_IN; 4. SS
>3V.
5
GNDA 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
6
SS
output clamping. This capacitor, along with an internal 12uA current source,
set the output clamp ramp up speed.
7
COMP
Internal Error Amplifier Output Pin. This pin is available for compensation of
the control loop.
8
FB
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
9
V_REF
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.
10 BG_REF Internal Bandgap Reference Voltage Output.
11
BOOT
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
12
UDRV the adaptive shoot through protection circuitry to determine when the high-side
MOSFET has turned off.
13
GND 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
14
I_SEN
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
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