sc604a Semtech Corporation, sc604a Datasheet - Page 10

• Manufacturer Part Number: sc604a
• Description: Sc604a Low-noise, High-efficiency Regulated White Led Driver
• Manufacturer: Semtech Corporation

Method 2. The example circuit in Figure 1 uses a 16.5k resistor
and an analog input DC voltage, V
to control LED current from 1mA to 30mA. Table 3 shows the
resulting output. If necessary, the analog V
sourced from a voltage higher than 1.2V, but the source must be
divided down so that the V
current applications and for higher resolution, a larger resistor
may be substituted in this circuit. PWM applications are also
possible with this circuit by application of RC filtering. (Consult
with Semtech for detailed application support).
POWER MANAGEMENT
Methods for Setting LED Current (Cont.)
2005 Semtech Corp.
V
0
0
0
0
0
0
A
0 .
2 .
3 .
4 .
5 .
Figure 1 - Analog Voltage for LED Current Control
1 .
J D
Table 3 - Analog Voltage for LED Current Control
0
0
0
0
0
0
[
] V
0
0
0
0
0
0
I
L
E
2
2
2
D
1
3
2
5
2
0
7
7
0
[
3 .
m
7 .
1 .
5 .
0 .
2 .
ADJ
] A
mode will not exceed 1.2V. For lower
ADJ
, which varies from 1.2V to 0V
V
0
0
0
0
1
1
A
6 .
7 .
8 .
9 .
0 .
1 .
J D
0
0
0
0
0
5
[
] V
0
0
0
0
0
0
ADJ
voltage can be
I
L
E
1
1
D
9
2
1
7
4
2
[
1 .
7 .
1 .
0 .
m
8 .
3 .
] A
10
Method 3. The circuit in Figure 2 uses open drain NMOS transistors
to set an equivalent resistance for R
switched on and off for R1, R2 and R3. R4 is always connected,
so that a minimum value of LED current can be maintained at
1.5mA.
Figure 2 - 3 Bit LED Current Control with Open Drain
SET
. Parallel combinations are
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SC604A