RT9202B
Functional Pin Description
BOOT (Pin 1)
This pin provides ground referenced bias voltage to the
upper MOSFET driver. A bootstrap circuit is used to
create a voltage suitable to drive a logic-level N-Channel
MOSFET when operating at a single 5V power supply.
This pin also could be powered from ATX 12V, in this
OCSET (Pin 7)
Connect a resistor from this pin to the drain of the upper
MOSFET. This resistor, an internal 20µA current source,
and the upper MOSFET on-resistance set the converter
over-current trip point. An over-current trip cycles the soft-
start function. The voltage at this pin is monitored for
power-on reset (POR) purpose and pulling this pin low
with an open drain device will shut down the IC.
I
×
R
OCSET
I
PEAK
=
OCSET
R
DS(ON)
situation, an internal 6.0V regulator will supply to VCC
pin for internal voltage bias.
UGATE (Pin 2)
Connect UGATE pin to the PWM converter's upper
MOSFET gate. This pin provides the gate drive for the
upper MOSFET.
GND (Pin 3)
Signal and power ground for the IC. All voltage levels are
measured with respect to this pin.
LGATE (Pin 4)
Connect LGATE to the PWM converter's lower MOSFET
gate. This pin provides the gate drive for the lower
MOSFET.
VCC (Pin 5)
This is the main bias supply for the RT9202B. This pin
also provides the gate bias charge for the lower MOSFET
gate. The voltage at this pin is monitored for power-on
reset (POR) purpose. This pin is also the internal 6.0V
regulator output powered from BOOT pin when BOOT
pin is directly powered from ATX 12V.
FB (Pin 6)
This pin is connected to the PWM converter's output
divider. This pin also connects to internal PWM error
amplifier inverting input and protection monitor.
PHASE (Pin 8)
This pin is used to monitor the voltage drop across the
upper MOSFET for over-current protection.
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DS9202B-03 March 2007
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
