cat4004 Catalyst Semiconductor, cat4004 Datasheet - Page 3

• Manufacturer Part Number: cat4004
• Description: 4-channel Constant Current Led Driver With Ezdim?
• Manufacturer: Catalyst Semiconductor

RECOMMENDED EN/DIM TIMING
For 2.4 ≤ V
* 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:
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
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
Symbol
T
T
Transitions HIGH
PWRDWN
number of pulses *
T
SETUP
T
T
LED
LO
HI
LOW
EN/DIM
IN
LED
Current
2
3
4
5
6
LED current =
1
x
EN/DIM
nd
rd
th
st
th
th
th
≤ 5.5V, over full ambient temperature range -40ºC to +85ºC.
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
Shutdown
T
SETUP
T
LED
132 ×
Device will keep cycling through gain selection
100%
R
0
6 .
SET
Figure 1. EN/DIM Dimming Timing Diagram
V
Shutdown mode
T
50%
LO
R
SET
T
4.125
HI
16.5
8.25
132
132
66
33
25%
Gain
Conditions
12.5% 6.25%
3
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
Pulses longer than the maximum T
device.
The LED driver enters a “zero current” shutdown mode
if EN/DIM is held low for 1.5ms or more.
LO
3.12%
may be ignored and filtered by the device.
100%
Min
0.2
0.2
1.5
10
4.125 x 0.6V/R
GAIN x 0.6V/R
T
16.5 x 0.6V/R
8.25 x 0.6V/R
132 x 0.6V/R
132 x 0.6V/R
PWRDWN
66 x 0.6V/R
33 x 0.6V/R
LED Current
Typ
40
Zero
LO
Shutdown
may shutdown the
SET
SET
Max
100
SET
SET
SET
SET
SET
SET
Doc. No. MD-5024 Rev. B
CAT4004
Units
ms
μs
μs
μs
μs