CAT3612 Datasheet, PDF (10/13 Pages) Catalyst Semiconductor – Programmable 300mA Camera Flash LED Driver

CAT3612
LED Current Setting
Figure 1 shows the EN/DIM input timing diagram for
setting the LED currents. The EN/DIM set-up time
requires the signal to be held high for 10µs or longer
to ensure the initialization of the driver at power-up.
Each subsequent pulse on the EN/DIM (300ns to
200µs pulse duration) steps down the LED current
from full scale of 150mA to zero with nearly 5mA
resolution. The selection of the LED current per
channel is shown in Table 1. Consecutive pulses
should be separated by 300ns or longer. Pulsing
beyond the 0mA level restores the current level back
to full scale and the cycle repeats. Pulsing frequencies
from 5kHz up to 1MHz can be supported during
dimming operations. When the EN/DIM is held low for
1.5ms or more, the CAT3612 enters the shutdown
mode and draws “zero” current.
For applications with a single LED connected to one
LED pin only, the unused LED pin must be tied to
VOUT, as shown on Figure 3.
Figure 3. Single LED on one LED pin
Table 1. Selection of LED current per Channel
Number of pulses
on EN/DIM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
LED current
(mA)
150
145
140
135.5
131
126
121
116
111
106.5
101.5
97
92
87
82
77.5
72.5
68
63
58
53
48.5
43.5
39
34
29
24
19
14.5
10
5
0
Figure 4. Application with 2 LEDs
Doc. No. 5016 Rev. A
10
© 2006 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice