深圳市中立信电子科技有限公司

FEATURES

Programmable Slope Compensation

Internal Soft-Start on the UCC38083/4

Cycle-by-Cycle Current Limiting

Low Start-Up Current of 120 μA and 1.5 mA

Typical Run Current

Single External Component Oscillator

Programmable from 50 kHz to 1 MHz

High-Current Totem-Pole Dual Output Stage

Drives Push-Pull Configuration with 1-A Sink

and 0.5-A Source Capability

Current Sense Discharge Transistor to

Improve Dynamic Response

Internally Trimmed Bandgap Reference

Undervoltage Lockout with Hysteresis

APPLICATIONS

High-Efficiency Switch-Mode Power Supplies

Telecom dc-to-dc Converters

Point-of-Load or Point-of-Use Power Modules

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

compensation function. This device also includes an

internal discharge transistor from the CS pin to ground,

which is activated at each clock cycle after the pulse is

terminated. This discharges any filter capacitance on

the CS pin during each cycle and helps minimize filter

capacitor values and current sense delay.

The UCC38083 and the UCC38084 devices have a

typical soft-start interval time of 3.5 ms while the

UCC38085 and the UCC38086 has less than 100 μs for

applications where internal soft-start is not desired.

The UCC38083 and the UCC38085 devices have the

turn-on/off thresholds of 12.5 V / 8.3 V, while the

UCC38084 and the UCC38086 has the turn-on/off

thresholds of 4.3 V / 4.1 V. Each device is offered in 8-pin

TSSOP (PW), 8-pin SOIC (D) and 8-pin PDIP (P)

packages.