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SLUS168D – APRIL 1999 – REVISED AUGUST 2002
D OR N PACKAGE
(TOP VIEW)
D
Dual Output Drive Stages in Push-Pull
Configuration
D
D
D
D
D
130-µA Typical Starting Current
1-mA Typical Run Current
Operation to 1-MHz
1
2
3
4
8
7
6
5
VDD
COMP
OUTA
OUTB
GND
FB
CS
RC
Internal Soft Start
On Chip Error Amplifier With 2-MHz Gain
Bandwidth Product
PW PACKAGE
(TOP VIEW)
D
On Chip VDD Clamping
1
2
3
4
8
7
6
5
OUTA
VDD
OUTB
GND
RC
D
Output Drive Stages Capable Of 500-mA
Peak Source Current, 1-A Peak Sink Current
COMP
FB
CS
description
The UCC3808 is a family of BiCMOS push-pull, high-speed, low-power, pulse-width modulators. The UCC3808
contains all of the control and drive circuitry required for off-line or dc-to-dc fixed frequency current-mode switching
power supplies with minimal external parts count.
The UCC3808 dual output drive stages are arranged in a push-pull configuration. Both outputs switch at half the
oscillator frequency using a toggle flip-flop. The dead time between the two outputs is typically 60 ns to 200 ns
depending on the values of the timing capacitor and resistors, thus limiting each output stage duty cycle to less than
50%. (continued)
block diagram
FB
2
COMP
1
CS
3
8
7
VDD
OVERCURRENT
COMPARATOR
22 k Ω
PEAK CURRENT
COMPARATOR
14 V
0.75 V
2.0 V
0.5 V
2.2 V
OUTA
VDD OK
OSCILLATOR
S
R
S
R
Q
Q
PWM
LATCH
1.2R
Q
Q
S
Q
R
VDD–1 V
T
PWM
COMPARATOR
VDD
0.5 V
R
SOFT START
6
5
OUTB
GND
VOLTAGE
REFERENCE
SLOPE = 1 V/ms
4
RC
Note: Pinout shown is for SOIC and PDIP packages. TSSOP pinout is different.
UDG-02116
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
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Copyright 2002, Texas Instruments Incorporated
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