US2076
Note 1 : Low duty cycle pulse testing with Kelvin con-
nections are required in order to maintain accurate data.
Note 2 : Drop-out voltage is defined as the minimum
differential voltage between Vin and Vout required to main-
tain regulation at Vout. It is measured when the output
voltage drops 1% below its nominal value.
Note 3 : Minimum load current is defined as the mini-
mum current required at the output in order for the out-
put voltage to maintain regulation. Typically the resistor
dividers are selected such that it automatically main-
tains this current.
PIN DESCRIPTIONS
PIN # PIN SYMBOL PIN DESCRIPTION
3
6
7
Vfb1
Vout
Vin
A resistor divider from this pin to the output of the switching regulator and
ground sets the Core supply voltage.
The output of the linear regulator. A minimum of a 100uF low ESR capacitor must be
connected from this pin to ground to insure stability.
The input pin of the linear regulator. Typically a large storage capacitor is connected
from this pin to ground to insure that the input voltage does not sag below the minimum
drop out voltage during the load transient response. This pin must always be higher than
Vout plus the maximum dropout voltage in order for the device to regulate properly.
This pin is connected to the IC substrate and must be connected to the lowest
potential in the system. It is also connected to the Tab of the package.
The PWM output of the switching controller. This pin is a totem pole drive that is
connected to the gate of the power MOSFET. A resistor may be placed in series from
this pin to the gate in order to reduce switching noise.
4
1
Gnd
Drv
5
2
Vfb2
V12
A resistor divider from this pin to the output of the linear regulator and
ground sets the I/O supply voltage.
This pin is connected to the 12V supply voltage. A high frequency cap must be
connected from this pin to the GND pin of the IC.
BLOCK DIAGRAM
V12
2
Vfb 1
3
Vin
7
Vout
6
UVLO
5V Reg
Drv
1
Vref
PWM Control
1.25V
Gnd
4
2076blk1-1.1
Vfb2
5
Figure 1 - Simplified block diagram of the US2076
Rev. 1.3
4/26/98
4-3
UNISEM [ UNISEM ]
