UCC2974

UCC3974

SLUS485A – JULY 2001 – REVISED NOVEMBER 2001

4

www.ti.com

electrical characteristics over recommended operating virtual junction temperature range,

mode select

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Enable threshold voltage

0.425

0.500

0.575

Output enable threshold voltage

0.85

1.00

1.15

V

Open lamp detect enable voltage threshold

2.75

3

3.25

V

Low-frequency dimming (LFD) voltage threshold

3.8

4.0

4.1

MODE output current

MODE = 0.5 V

3.3

5.0

6.8

µA

MODE clamp voltage

MODE = OPEN

4.0

4.2

4.4

V

low-frequency dimming

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Duty cycle

RC = 400 kΩ,

RD = 20 kΩ,

CLFD = 10 nF,

DIM < 0.5 V

6%

10%

12%

Maximum duty cycle

RC = 400 kΩ,

RD = 20 kΩ,

CLFD = 10 nF,

DIM > 3.1 V

100%

Free-running oscillator frequency

RC = 400 kΩ,

RD = 20 kΩ,

CLFD = 10 nF

200

Synchronized oscillator frequency

RC = 400 kΩ,

RD = 20 kΩ,

CLFD = 10 nF,

FLFDSYNC = 400 Hz at VLFDSYNC = 2.25 V

400

Hz

open lamp

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Open lamp detect threshold voltage

VIN = 12 V,

Measured at VBUCK wrt VIN

–8.5

–7.8

–7.0

Open lamp detect threshold voltage

VIN = 25 V,

Measured at VBUCK wrt VIN

–8.6

–7.8

–6.9

V

Voltage clamp detect threshold voltage

Measured at VBUCK

–9.6

–8.75

–8.0

NOTES:

1: Ensured by design, not production tested.