8-Pin Current Mode Push-Pull PWM Controllers - Texas Instruments
Description
UCC28083, UCC28084, UCC28085, UCC28086 UCC38083, UCC38084, UCC38085, UCC38086
SLUS488E − SEPTEMBER 2002 − REVISED JULY 2009
8ĆPIN CURRENT MODE PUSHĆPULL PWM CONTROLLERS WITH PROGRAMMABLE SLOPE COMPENSATION
FEATURES
D Programmable Slope Compensation D Internal Soft-Start on the UCC38083/4 D Cycle-by-Cycle Current Limiting D Low Start-Up Current of 120 µA and 1.
5 mA
Typical Run Current
D Single External Component Oscillator
Programmable from 50 kHz to 1 MHz
D High-Current Totem-Pole Dual Output Stage
Drives Push-Pull Configuration with 1-A Sink and 0.
5-A Source Capability
D Current Sense Discharge Transistor to
Improve Dynamic Response
D Internally Trimmed Bandgap Reference D Undervoltage Lockout with Hysteresis
BASIC APPLICATION
V IN
VDD UCC3808x
CTRL OUTA
RT OUTB
ISET
CS
RT R SET
GND
POWER TRANSFORMER
RF CF RS
FEEDBACK
APPLICATIONS
D High-Efficiency Switch-Mode Power Supplies D Telecom dc-to-dc Converters D Point-of-Load or Point-of-Use Power Modules D Low-Cost Push-Pull and Half-Bridge
Applications
DESCRIPTION
The UCC38083/4/5/6 is a family of BiCMOS pulse width modulation (PWM) controllers for dc-to-dc or off-line fixed-frequency current-mode switching power supplies.
The dual output stages are configured for the push-pull topology.
Both outputs switch at half the oscillator frequency using a toggle flip-flop.
The dead time between the two outputs is typically 110 ns, limiting each output’s duty cycle to less than 50%.
The new UCC3808x family is based on the UCC3808A
architecture.
The major differences include the addition
of a programmable slope compensation ramp to the CS
signal and the removal of the error amplifier.
The current
flowing out of the ISET pin through an external resistor
is monitored internally to set the magnitude of the slope
VOUT
compensation function.
This device internal discharge transistor from the
also includes an CS pin to ground,
which is activated at each clock cycle after the pulse is
terminated.
This discharges...
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