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

CAT3612
LED Current Setting
Figure 2 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 10 ms or longer to ensure the
initialization of the driver at power−up. Each subsequent
pulse on the EN/DIM (300 ns to 200 ms pulse duration) steps
down the LED current from full scale of 150 mA to zero with
nearly 5 mA resolution. The selection of the LED current per
channel is shown in Table 6. Consecutive pulses should be
separated by 300 ns or longer. Pulsing beyond the 0 mA level
restores the current level back to full scale and the cycle
repeats. Pulsing frequencies from 5 kHz up to 1 MHz can be
supported during dimming operations. When the EN/DIM
is held low for 1.5 ms or more, the CAT3612 enters the
shutdown mode and draws “zero” current.
For applications with 2 LEDs, each LED connected to one
LED pin, refer to Figure 28.
1 mF 1 mF
V_IN
3 V to
5.5 V
C1+ C1− C2+ C2−
C_IN ^VIN
VOUT
2.2 mF
CAT3612
ENABLE/
DIMMING
LED1
EN/DIM
LED2
GND
C_OUT
2.2 mF
Flash
LED
150 mA
Figure 28. Application with 2 LEDs
Table 6. SELECTION OF LED CURRENT
PER CHANNEL
Number of Pulses on EN/DIM
LED Current (mA)
1
150
2
145
3
140
4
135.5
5
131
6
126
7
121
8
116
9
111
10
106.5
11
101.5
12
97
13
92
14
87
15
82
16
77.5
17
72.5
18
68
19
63
20
58
21
53
22
48.5
23
43.5
24
39
25
34
26
29
27
24
28
19
29
14.5
30
10
31
5
32
0
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