4
Rev. 1.6
08/20/02
IRU3011
www.irf.com
PIN DESCRIPTIONS
No connection.
This pin is connected to the Drain of the power MOSFET of the Core supply and it
provides the positive sensing for the internal current sensing circuitry. An external resis-
tor programs the CS threshold depending on the RDS of the power MOSFET. An external
capacitor is placed in parallel with the programming resistor to provide high frequency
noise filtering.
This pin provides the soft-start for the switching regulator. An internal current source
charges an external capacitor that is connected from this pin to the ground which ramps
up the outputs of the switching regulator, preventing the outputs from overshooting as
well as limiting the input current. The second function of the Soft-Start cap is to provide
long off time for the synchronous MOSFET or the Catch diode (HICCUP) during current
limiting.
LSB input to the DAC that programs the output voltage. This pin can be pulled up exter-
nally by a 10K resistor to either 3.3V or 5V supply.
Input to the DAC that programs the output voltage. This pin can be pulled-up externally
by a 10KV resistor to either 3.3V or 5V supply.
Input to the DAC that programs the output voltage. This pin can be pulled-up externally
by a 10K resistor to either 3.3V or 5V supply.
MSB input to the DAC that programs the output voltage. This pin can be pulled-up exter-
nally by a 10K resistor to either 3.3V or 5V supply.
This pin selects a range of output voltages for the DAC.
5V supply voltage.
This pin is connected directly to the output of the Core supply to provide feedback to the
Error comparator.
No connection.
This pin is an open collector output that switches LO when the output of the converter is
not within ±10% (typ) of the nominal output voltage. When PGd pin switches LO the
saturation voltage is less than 0.4V at 3mA.
This pin is connected to the Source of the power MOSFET for the Core supply and it
provides the negative sensing for the internal current sensing circuitry.
Output driver for the high side power MOSFET.
No connection.
This pin serves as the ground pin and must be connected directly to the ground plane. A
high frequency capacitor (0.1 to 1mF) must be connected from V5 and V12 pins to this
pin for noise free operation.
Output driver for the synchronous power MOSFET.
This pin is connected to the 12 V supply and serves as the power Vcc pin for the output
drivers. A high frequency capacitor (0.1 to 1mF) must be connected directly from this pin
to ground pin in order to supply the peak current to the power MOSFET during the
transitions.
Over-voltage comparator output.
This pin programs the oscillator frequency in the range of 50KHz to 500KHz with an
external capacitor connected from this pin to the ground.
PIN# PIN SYMBOL PIN DESCRIPTION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
NC
CS+
SS
D0
D1
D2
D3
D4
V5
VFB
NC
PGd
CS-
HDrv
NC
Gnd
LDrv
V12
OVP
Ct
