RT9229
DS9229-03 July 2001
www.richtek-ic.com.tw
5
Functional Pin Description
UGATE1, UGATE2 (Pins 27 and 1)
Connect UGATE pins to the respective PWM
converter’s upper MOSFET gate. This pin provides
the gate drive for the upper MOSFETs.
PHASE1, PHASE2 (Pins 26 and 2)
Connect the PHASE pins to the PWM converter’s
upper MOSFET source. These pins are used to
monitor the voltage drop across the upper MOSFETs
for over-current protection.
VID0, VID1, VID2, VID3, VID4 (Pin 7, 6, 5, 4, and 3)
VID0~4 are the input pins to the 5-bit DAC. The
states of these five pins program the internal voltage
reference, DACOUT. The level of DACOUT sets the
core converter output voltage (VOUT1). It also sets
the core PGOOD and OVP thresholds. Table 1
specifies the DACOUT voltage of 32 combinations of
VID levels.
PGOOD (Pin 8)
PGOOD is an open collector output used to indicate
the status of the PWM converter output voltage. This
pin is pulled low when the core output is not within
±10% of the DACOUT reference voltage, or when
any of the other outputs are below their under-
voltage thresholds. The PGOOD output is open for
‘11111’VID code. See table 1.
FB1, FB2 (21 and 10)
FB1, 2 are the available external pins of the PWM
error amplifiers. Both the FB pins are the inverting
input of the error amplifiers.
OCSET1, OCSET2 (Pins 23 and 9)
Connect a resistor (ROCSET) from this pin to the drain
of the upper MOSFET. ROCSET, an internal 200
µA
current source (IOCSET), and the upper MOSFET on-
resistance (RDS(ON)) set the converter over-current
(OC) trip point according to the following equation:
IOCSET×ROCSET
IPEAK =
RDS(ON)
An over-current trip cycles the soft-start function.
Sustaining an over-current for 2 soft-start intervals
shuts down the controller.
SS (Pin 12)
Connect a capacitor from this pin to ground. This
capacitor, along with an internal 11
µA (VSS>1V)
current source, sets the soft-start interval of the
converter.
Pulling this pin low with an open drain signal will shut
down the IC.
FAULT (Pin 13)
This pin is low during normal operation, but it is
pulled to about 8V (VCC = 12V) in the event of an
over-voltage or over-current condition.
FB4 (Pin 14)
Connect this pin to a resistor divider to set the linear
regulator output.
VSEN1, VSEN2 (Pins 22 and 15)
These pins are connected to the PWM converters’
output voltage. The PGOOD and OVP comparator
circuits use these signals to report output voltage
status and for over-voltage protection. VSEN2
provides the input power to the integrated linear
regulator.
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