UCC2808A 1, UCC2808A 2, UCC3808A 1, UCC3808A 2
LOW POWER CURRENT MODE PUSH PULL PWM
SLUS456D 鈥?APRIL 1999 - REVISED AUGUST 2002
D
Dual Output Drive Stages in Push-Pull
D
D
D
D
D
D
D
D
Configuration
Current Sense Discharge Transistor to
Improve Dynamic Response
130-碌A Typical Starting Current
1-mA Typical Run Current
Operation to 1 MHz
Internal Soft Start
On-Chip Error Amplifier With 2-MHz Gain
Bandwidth Product
On Chip VDD Clamping
Output Drive Stages Capable of 500-mA
Peak-Source Current, 1-A Peak-Sink Current
D OR N PACKAGE
(TOP VIEW)
COMP
FB
CS
RC
1
2
3
4
8
7
6
5
VDD
OUTA
OUTB
GND
PW PACKAGE
(TOP VIEW)
OUTA
VDD
COMP
FB
1
2
3
4
8
7
6
5
OUTB
GND
RC
CS
description
The UCC3808A is a family of BiCMOS push-pull, high-speed, low-power, pulse-width modulators. The UCC3808A
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 UCC3808A 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%.
block diagram
FB
2
COMP
1
CS
3
8
OVERCURRENT
COMPARATOR
0.75 V
2.0 V
2.2 V
7
VDD OK
S
Q
R
1.2R
VDD鈥? V
S
Q
R
0.5 V
SOFT START
VOLTAGE
REFERENCE
VDD
R
6
OUTB
PWM
COMPARATOR
PWM
LATCH
S
Q
R
Q
T
Q
OSCILLATOR
OUTA
0.5 V
22 k
鈩?/div>
PEAK CURRENT
COMPARATOR
14 V
VDD
SLOPE = 1 V/ms
5
GND
4
Note: Pinout shown is for SOIC and PDIP packages. TSSOP pinout is different.
RC
UDG-00097
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.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright
铮?/div>
2002, Texas Instruments Incorporated
www.ti.com
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