CAT4004_08 Datasheet, PDF (3/11 Pages) Catalyst Semiconductor – 4-Channel Constant Current LED Driver with EZDim™

CAT4004
RECOMMENDED EN/DIM TIMING
For 2.4 ≤ V_IN ≤ 5.5V, over full ambient temperature range -40ºC to +85ºC.
Symbol
T_SETUP
T_LO
T_HI
T_PWRDWN
T_LED
Name
EN/DIM setup from shutdown
EN/DIM program low time
EN/DIM program high time
EN/DIM low time to shutdown
LED current settling time
Conditions
Min
10
0.2
0.2
1.5
T_SETUP
T_HI
Typ
40
T_PWRDWN
Max Units
μs
100
μs
μs
ms
μs
EN/DIM
T_LED
LED
Current
Shutdown
T_LO
100%
100%
50%
25% _{12.5% 6.25% 3.12%}
Figure 1. EN/DIM Dimming Timing Diagram
Shutdown
EN/DIM
number of pulses *
LOW
Transitions HIGH
1^st
2^nd
3^rd
4^th
5^th
6^th
x^th
R_SET Gain
Shutdown mode
132
66
33
16.5
8.25
4.125
132
Device will keep cycling through gain selection
* The gain is changed on the rising edges of the EN/DIM input.
LED Current
Zero
132 x 0.6V/R_SET
66 x 0.6V/R_SET
33 x 0.6V/R_SET
16.5 x 0.6V/R_SET
8.25 x 0.6V/R_SET
4.125 x 0.6V/R_SET
132 x 0.6V/R_SET
GAIN x 0.6V/R_SET
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 = 132 × ^0.6V
R _SET
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-
mum T_LO may be ignored and filtered by the device.
Pulses longer than the maximum T_LO may shutdown the
device.
The LED driver enters a “zero current” shutdown mode
if EN/DIM is held low for 1.5ms or more.
© Catalyst Semiconductor, Inc.
3
Characteristics subject to change without notice
Doc. No. MD-5024 Rev. B