CAT4004

© 2008 SCILLC. All rights reserved.

3

Doc. No. MD-5024 Rev. C

Characteristics subject to change without notice

SET

R

V

6

.

0

132

×

RECOMMENDED EN/DIM TIMING

For 2.4

Symbol

Name

Conditions

Min

Typ

Max

Units

EN/DIM setup from shutdown

10

μs

EN/DIM program low time

0.2

100

μs

EN/DIM program high time

0.2

μs

EN/DIM low time to shutdown

1.5

ms

LED current settling time

40

μs

Figure 1. EN/DIM Dimming Timing Diagram

EN/DIM

number of pulses *

LED Current

LOW

Shutdown mode

Zero

Transitions HIGH

132

1

st

66

2

nd

33

3

rd

16.5

4

th

8.25

5

th

4.125

6

th

132

x

th

Device will keep cycling through gain selection

* The gain is changed on the rising edges of the EN/DIM input.

LED CURRENT SELECTION

At power-up, the initial LED current is set to full scale

(100% brightness) by the external resistor RSET as

follows:

LED current =

The EN/DIM pin has two primary functions. One

function enables and disables the device. The other

function is LED current dimming with six different

levels by pulsing the input signal, as shown on Figure 3.

On each consecutive pulse rising edge, the LED current

is divided by half to 50%, then 25%, 12.5%, 6.25% and

3.125% dimming levels. Pulses faster than the mini-

device.

The LED driver enters a “zero current” shutdown mode

if EN/DIM is held low for 1.5ms or more.

EN/DIM

LED

Current

Shutdown

Shutdown

100%

50%

25%

12.5% 6.25% 3.12%

100%