US3007
Pin Description
PIN# PIN SYMBOL
This pin is internally connected to the undervoltage and overvoltage comparators sensing
the Vcore status. It must be connected directly to the Vcore supply.
22
10
VSEN1
FB2
This pin provides the feedback for the non-synchronous switching regulator. A resistor
divider is connected from this pin to vout2 and GND that sets the output voltage. The
value of the resistor connected from Vout2 to FB2 must be less than 100W.
This pin is connected to the output of the I/O switching regulator. It is an input that
provides sensing for the Under/Over voltage circuitry for the I/O supply as well as the
power for the internal LDO regulator.
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 C.S 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.
15
23
VSEN2
OCSET1
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.
This pin is connected to the Drain of the power MOSFET of the I/O supply and it provides
the positive sensing for the internal current sensing circuitry. An external resistor pro-
grams the C.S 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.
26
9
PHASE1
OCSET2
This pin is connected to the Source of the power MOSFET for the I/O supply and it
provides the negative sensing for the internal current sensing circuitry.
This pin provides the soft start for the 2 switching regulators. An internal resistor charges
an external capacitor that is connected from 5V supply to this pin which ramps up the
outputs of the switching regulators, 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 (HICCUP) for the synchronous MOSFET during current limiting.
2
PHASE2
SS
12
This pin has dual function. It acts as an output of the OVP circuitry or it can be used to
program the frequency using an external resistor . When used as a fault detector, if any
of the switcher outputs exceed the OVP trip point, the FAULT pin switches to 12V and
the soft start cap is discharged. If the FAULT pin is to be connected to any external
circuitry, it needs to be buffered as shown in the application circuit.
13
FAULT/Rt
This pin controls the gate of an external transistor for the 1.5V GTL+ linear regulator.
This pin provides the feedback for the linear regulator that its output drive is GATE3.
This pin is the output of the internal LDO regulator.
This pin provides the feedback for the internal LDO regulator that its output is Vout4.
This pin serves as the ground pin and must be connected directly to the ground plane.
This pin serves as the Power ground pin and must be connected directly to the GND
plane close to the source of the synchronous MOSFET. A high frequency capacitor
(typically 1 uF) must be connected from V12 pin to this pin for noise free operation.
Output driver for the synchronous power MOSFET for the Core supply.
Output driver for the high side power MOSFET for the Core supply.
18
19
16
14
17
24
GATE3
FB3
VOUT4
FB4
GND
PGND
25
27
1
LGATE1
UGATE1
UGATE2
V12
Output driver for the high side power MOSFET for the I/O supply.
This pin is connected to the 12 V supply and serves as the power Vcc pin for the output
drivers. A high frequency capacitor (typically 1 uF) must be placed close to this pin and
PGND pin and be connected directly from this pin to the GND plane for the noise free
operation.
28
5V supply voltage. A high frequency capacitor (0.1 to 1 uF) must be placed close to this
pin and connected from this pin to the GND plane for noise free operation.
No connect
11
20
V5
N.C
Rev. 1.8
12/8/00
4-5
UNISEM [ UNISEM ]
