ML4835

6

FUNCTIONAL DESCRIPTION

The ML4835 consists of peak or average current

controlled continuous boost power factor front end section

with a flexible ballast control section. Start-up and lamp-

out retry timing are controlled by the selection of external

timing components, allowing for control of a wide variety

of different lamp types. The ballast section controls the

lamp power using frequency modulation (FM) with

additional programmability provided to adjust the VCO

frequency range. This allows for the IC to be used with a

variety of different output networks. Figure 1 depicts a

detailed block diagram of ML4835.

The ML4835 provides several safety features. See the

corresponding sections for more details:

• End-of-lamp life detection to detect EOL and shut-off

lamps; See End Of Life Section.

• Thermal shutdown for temperature sensing extremes;

See IC Bias, Under-Voltage Lockout and Thermal

Shutdown Section.

• Relamping starting with anti-flash for programmable

restart for lamp out conditions while minimizing

“flashing” when powering from full power to dimming

levels; See Starting, Re-Start, Preheat and Interrupt

Section

Figure 1. Detailed Block Diagram

VCC

19

REF

20

AGND

14

CRAMP

13

PVFB/OVP

1

PEAO

2

PIFB

PIFBO

4

PFC OUT

18

RSET

7

LAMP FB

5

LEAO

6

RT2

8

INTERRUPT

10

PWDET

12

PGND

15

OUT B

16

OUT A

17

REF

–

+

14V

+

–

6.75V

Q

Q

R

S

Q

Q

T

+

–

TEMP

130ºC/100ºC

+

–

1.25V/1V

RX/CX

6.75V/1.25V

2.5V

+

–

1.0V

Q

Q

S

R

–

+

–

+

+

–

4.75V/

1.75V

+

–

PVFB

2.75V

+

–

–1V

+

–

3

R

S

Q

Q

R

S

Q

Q

–

+

2.5V

V

TO

I

÷2

CLK1

CLK

RX/CX

11

PFC CONTROLLER

OVP

ILIM

UVLO

REF_OK

PREHEAT

THERMAL SHUTDOWN

RT/CT

9

OSCILLATOR

COMP