AIC1573
creasing the frequency by the
following figure (Fig.3).
This pin is 1.26V during normal
operation, but it is pulled to VCC
in the event of an over-voltage or
over-current condition.
f
=
f0 1 +
25.2K
RT
,
RT pulled to GND
f
=
f0
1
−
VCC
5
− 1.26V
× RT
,
RT pulled to VCC,
where f0 is free run frequency.
Pin14: VSEN4: Connect this pin to the 1.8V
linear regulator’s output. This pin
is monitored for under-voltage
events.
Pin15: DRIVE4: Connect this pin to the gate of
the external N-MOS to supply
1.8V power for Memorey re-
quirement.
Pin 16: VAUX: The +3.3V input voltage at this
pin is monitored for power-on –
reset (POR) purpose. Connect to
+5V provides boost current for
the linear regulator’s output.
Pin 17: GND: Signal GND for IC. All voltage
levels are measured with respect
to this pin.
Pin 18: DRIVE3: Connect this pin to the Gate of
the external N-MOS for providing
1.5V power to GTL bus.
Pin 19: VSEN3: Connect this pin to the 1.5V
linear regulator’s output. This pin
is monitored for under-voltage
events.
Pin 20: COMP1: External compensation pin of the
synchronous PWM converter.
This pin is connected to error
amplifier output and PWM com-
parator. A RC network is con-
nected to FB1 in to compensate
the voltage control feedback loop
of the converter.
Pin 21: FB1: The error amplifier inverting input
pin of the synchronous PWM
converter. The FB1 pin and
COMP1 pin are used to compen-
sate the voltage-control feedback
loop.
Pin 22: VSEN1: Synchronous PWM converter’s
output voltage sense pin. Con-
nect this pin to the converter out-
put. The PGOOD and OVP com-
parator circuits use this signal to
report output voltage status and
for over-voltage protection func-
tion.
Pin 23: OCSET1: Current limit sense pin. Connect
a resistor ROCSET from this pin to
the drain of the external high-side
N-MOSFET. ROCSET, an internal
200µA current source (IOCSET),
and the upper N-MOSFET on-
resistance (RDS(ON)) set the over-
current trip point according to the
following equation:
IPEAK = IOCSET × ROCSET
RDS(ON)
The voltage at this pin is also
moni tored for power-on reset
(POR) purpose.
Pin 24: PGND: Driver power GND pin. PGND
should be connected to a low im-
pedance ground plane in close to
lower N-MOSFET source.
Pin 25: LGATE1: Lower N-MOSFET gate drive pin
of the synchronous PWM con-
verter.
Pin 26: PHASE1:
Over-current detection pin. Con-
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