UCC1809-1/-2

UCC2809-1/-2

UCC3809-1/-2

SLUS166B - NOVEMBER 1999 - REVISED NOVEMBER 2004

FEATURES

• User Programmable Soft Start With

Active Low Shutdown

• User Programmable Maximum Duty

Cycle

• Accessible 5V Reference

• Undervoltage Lockout

• Operation to 1MHz

• 0.4A Source/0.8A Sink FET Driver

• Low 100µA Startup Current

Economy Primary Side Controller

1

3

2

7

FB

+

–

+

–

1V

+

–

6µA

+5V

0.5V

OSC

4

R

Q

S

–

+

5V

REF

15/8V

10/8V

VDD

8

REF

5

+

–

SS

RT1

RT2

DISABLE

NOISE

FILTER

SLOPE

COMP

CURRENT

SENSE

FEEDBACK

CLK

PWM

LATCH

UVLO

1V

6

17.5V

OUT

GND

TYPICAL APPLICATION DIAGRAM

UDG-99036

DESCRIPTION

The UCC3809 family of BCDMOS economy low power integrated circuits

contains all the control and drive circuitry required for off-line and isolated

DC-to-DC fixed frequency current mode switching power supplies with

minimal external parts count. Internally implemented circuits include

undervoltage lockout featuring startup current less than 100

µA, a user ac-

cessible voltage reference, logic to ensure latched operation, a PWM com-

parator, and a totem pole output stage to sink or source peak current. The

output stage, suitable for driving N-Channel MOSFETs, is low in the off

state.

Oscillator frequency and maximum duty cycle are programmed with two

resistors and a capacitor. The UCC3809 family also features full cycle soft

start.

The family has UVLO thresholds and hysteresis levels for off-line and

DC-to-DC systems as shown in the table to the left.

The UCC3809 and the UCC2809 are offered in the 8 pin SOIC (D), PDIP

(N), TSSOP (PW), and MSOP (P) packages. The small TSSOP and

MSOP packages make the device ideal for applications where board

space and height are at a premium.

PART

NUMBER

TURN ON

THRESHOLD

TURN OFF

THRESHOLD

UCCX809-1

10V

8V

UCCX809-2

15V

8V

application

INFO

available