Datasheet

1 3 4 5 6 2 7
EP
LED+ LED+
DIM
GND
VREF
IADJ
LED-
V
IN
High Power LED String
I
LED
I
IN
TPS92551
C
IN
R
VREF
R
IADJ
LED
VREF
1050
I
3k / /R
LED
IADJ
1050
I
3k R 
TPS92551, TPS92551EVM
SNVS805C –MAY 2012–REVISED MAY 2013 www.ti.com
APPLICATION INFORMATION
SETTING THE LED CURRENT
The TPS92551 requires no external current sensing resistor for LED current regulation. The average LED current
of the TPS92551 is adjustable from 300mA to 450mA by varying the resistance of the resistor according to the
following equation and table.
For R
VREF
= open and R
IADJ
<=499Ω
(1)
For R
IADJ
= 0 and R
VREF
>= 10.5kΩ
(2)
Table 1. Example for I
LED
Setting
R
IADJ
(Ω) R
VREF
(Ω) I
LED
(mA)
499 OPEN 300
SHORT OPEN 350
SHORT 10.5k 450
Figure 32. TPS92551 Application Schematic for I
LED
Setting
Minimum Switch On-Time
The on-time of the internal switch should be no shorter than 400ns. The number of LED (typical forward voltage
at 3.2V) to input voltage is constrained by that as shown in the following table.
No. of LED Max. V
IN
(V)
1 10
2 20
3 30
4 40
5 50
6 – 16 60
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