LP3359-MSF POWER [Lowpower Semiconductor inc], LP3359-MSF Datasheet - Page 6

• Manufacturer Part Number: LP3359-MSF
• Description: High performance, Current Source For Parallel White-LED Driver
• Manufacturer: POWER [Lowpower Semiconductor inc]

equals 12.5kΩ.
I
I
LED Selection
The LP3359 is designed to drive white-LEDs with a typical
forward voltage of 3.0V to 4.0V. The maximum LED forward
voltage that the LP3359 can accommo -date is highly
dependant upon V
Current Capability for more information on finding maximum
V
matching, care must be taken to select LEDs from the same
chromaticity group. Forward current matching is assured over
V
LED
V
LED
LEDX
ADJ
ADJ
LP3359-datasheet Ver.1.1 Nov.-2005
(mA)
(mA)
(V)
(V)
.) For applications that demand color and brightness
19.7 18.1 16.5 14.9 13.3 11.7 10.1
Figure4. LED current setting example
1.4
8.5
0
which using a DC voltage to Rset
0.2
1.6
6.9
IN
and I
0.4
1.8
5.3
LEDX
(See the section on Output
0.6
3.7
2
2.1
0.8
2.2
2.4
0.5
1
1.2
2.5
0
the LED process variations due to the constant current outputs
of the LP3359.
Parallel LEDx Outputs for Increased Current Driver
Outputs LED1 through LED4 may be connected together in
any combination to drive higher currents through fewer
LEDs. For example in Figure 5, outputs LED1 and LED2 are
connected together to drive one LED while LED3 and LED4
are connected together to drive a second LED.
With this configuration, two parallel current sources of equal
value provide current to each LED. R
chosen so that the current through each output is programmed
to 50% of the desired current through the parallel connected
LEDs. For example, if 30mA is the desired drive current for 2
parallel connected LEDs, R
current through each of the outputs is 15mA. Other
combinations of parallel outputs may be implemented in
similar fashions, such as in Figure 6.
Figure 5. Two Parallel Connected LEDs
6
-
Figure 6. One Parallel Connected LED
6
SET
should be selected so that the
SET
LP3359
should therefore be