SM8135A
FUNCTIONAL DESCRIPTION
LED Drive Current Setting
The SM8135A LED drive current can be set using a combination of 2 methods: (1) current setting resistance
connected to ISET, and (2) PWM signal input control on the EN pin.
(1) Setting LED drive current using RSET
The LED drive maximum current value per LED (I
) is determined by the resistor (RSET) connected
LED MAX
to the ISET pin. The relationship between RSET and I
is given by the following equation.
LED MAX
I
[mA] = 2400/RSET [kΩ]
LED MAX
(For example, I
= 20mA when RSET = 120kΩ.)
LED MAX
The RSET resistance has a minimum rating of 60kΩ. At this value of resistance, the I
has a maximum
LED MAX
rating of 40mA/LED. However, note that the total LED drive current for all LEDs must not exceed 80mA.
ꢁ0
ISET
40
30
20
RSET
10
0
0
100
200
300
400
ꢁ00
GND
RSET [kΩ]
RSET vs. I
LED MAX
SEIKO NPC CORPORATION —5
NPC [ NIPPON PRECISION CIRCUITS INC ]
