US3033 查看數據表（PDF） - Unisem
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US3033 Datasheet PDF : 9 Pages
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US3033
PIN DESCRIPTIONS
PIN #
3
6
7
5
1
4
2
8
PIN SYMBOL
VFB1
VFB2
Drv2
Gnd
Drv1
VHYST
V12SW
V12
PIN DESCRIPTION
A resistor divider from this pin to the output of the switching regulator and ground sets the
Core supply voltage.
The feedback pin of the linear regulator. A resistor divider from this pin to the output of the
linear regulator and ground sets the I/O supply voltage.
The drive pin of the linear regulator. This pin controls the base of a transistor or the gate
of a MOSFET acting as the series pass element for the linear regulator.
This pin is connected to the IC substrate and must be connected to the lowest potential
in the system.
The PWM output of the switching controller. This pin is a totem pole drive that is con-
nected to the gate of the power MOSFET. A resistor may be placed from this pin to the
gate in order to reduce switching noise.
A resistor and a 10pF capacitor is connected from this pin to the VFB1 pin to set the
output ripple voltage for the switching regulator.
This pin supplies the voltage to the PWM drive and hysterises circuitry and it is con-
nected to the 12V supply. A 1 uF, high frequency capacitor must be connected from this
pin to ground to provide the peak current for charging and discharging of the MOSFET.
This pin provides the biasing for the chip and drive for the linear regulator controller. It
isconnected to 12V supply. A 10 ohm resistor in series from this pin to the 12V supply
and a 1uF, high frequency capacitor connected from this pin to Gnd is required to filter
the switching noise of the switching regulator.
BLOCK DIAGRAM
V12sw Vhyst
2
4
Drv 1
1
Gnd
5
Vfb 1
V12
3
8
UVLO
Vref
PWM Control
1.25V
3033blk1-1.0
5V Reg
Drv 2
7
Vfb2
6
Rev. 1.5
1/14/99
Figure 1 - Simplified block diagram of the US3033
4-3
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