US3004,US3005
PIN DESCRIPTIONS
PIN# PIN SYMBOL
19
D0
18
17
16
15
D1
D2
D3
D4
Pin Description
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 10kΩ 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.When in the LOW state the range
is 1.3V to 2.05V.
For VID codes of all "1" the US3004 keeps all the outputs on.
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 PWRGD pin switches LO the
sat voltage is less than 0.4V at 3mA.
This pin is connected directly to the output of the Core supply to provide feedback to the
Error comparator.
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.
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 provides the soft start for the switching regulator. An internal current source
charges an external capacitor that is conected from this pin to the GND which ramps up
the outputs of the switching regulator, preventing the outputs from overshooting as wellas
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.
This pin programs the oscillator frequency in the range of 50 kHZ to 500kHZ with an
external capacitor connected from this pin to the GND.
This pin controls the gate of an external transistor for either the GTL+ linear regulator or
Clock supply.
This pin provides the feedback for the linear regulator that its output drive is Lin1 pin.
For
US3005, this pin is connected to the 2.5V regulator, eliminating the external di-
viders.
This pin controls the gate of an external transistor for either the GTL+ linear regulator or
Clock supply.
This pin provides the feedback for the linear regulator that its output drive is Lin2 pin.
This pin serves as the ground pin and must be conected directly to the ground plane. A
high frequency capacitor (0.1 to 1 uF) must be connected from V5 and V12 pins to this
pin for noise free operation.
Output driver for the synchronous power MOSFET.
Output driver for the high side 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 1 uF) must be connected directly from this pin
to GND pin in order to supply the peak current to the power MOSFET during the transi-
tions.
5V supply voltage.
6
PGd
14
8
Vfb3
CS+
7
13
CS-
SS
1
2
3
Ct
Lin1
Vfb1
20
4
10
Lin2
Vfb2
Gnd
11
9
12
LDrv
HDrv
V12
5
V5
4-4
Rev. 1.2
12/8/00
UNISEM [ UNISEM ]
