S-8813 Datasheet, PDF (11/29 Pages) Seiko Instruments Inc – 3-CHANNEL WHITE LED DRIVER IC (CHARGE PUMP IC WITH BUILT-IN CONSTANT-CURRENT CIRCUIT)

3-CHANNEL WHITE LED DRIVER IC (CHARGE PUMP IC WITH BUILT-IN CONSTANT-CURRENT CIRCUIT)
Rev.2.1_00
S-8813 Series
3. Constant current output circuit
The S-8813 Series features a three-channel constant current output circuit and enables driving of white
LEDs in the current mode.
In the case of the S-8813 Series, the constant current value can be controlled using one of the two
following methods according to the product.
In the case of the S-881300CPE, the desired constant current can be obtained with an external
resistance value. Since a reference voltage of 1 V ±2% is output to the RISET pin, application of
resistance R1 of 20 kΩ to 5.6 kΩ between the RISET pin and GND results in the flow of a constant current
of 50 μA to 178 μA in the current setting resistance (R₁) due to the I = V/R relationship. Amplifying this
constant current 100 times and outputting it to I_OUT1, I_OUT2, and I_OUT3 can obtain a constant current of
between 5 mA to 17.8 mA/channel.
1 : 100
CPOUT VCPOUT= 5.0 V
C_OUT=10 μF
IOUT1 (I_OUT1=5.0 mA to 17.8 mA)
IOUT2 (I_OUT2=5.0 mA to 17.8 mA)
IOUT3 (I_OUT3=5.0 mA to 17.8 mA)
−
RISET
+
R₁=5.6 kΩ to 20 kΩ
1 V ±2%
reference voltage
Figure 8 Constant Current Circuit (S-881300CPE)
On the other hand, a constant current of the desired value can also be obtained for the S-881300BPE by
supplying the reference voltage to the VISET pin externally. Within the IC, a resistance of 10 kΩ is applied
between the VISET pin and GND. The application of a reference voltage of between 0.5 V and 1.8 V to
the VISET pin results in the flow of a current between 50 μA and 180 μA in the internal resistor (R₂) due to
the I = V/R relationship. Amplifying this constant current 100 times and outputting it to I_OUT1, I_OUT2, and
I_OUT3 can obtain a constant current of between 5 mA to 18 mA/channel.
1 : 100
CPOUT V_CPOUT=5.0 V
C_OUT=10 μF
+
−
R₂=10 kΩ
IOUT1 (I_OUT1=5.0 mA to 17.8 mA)
IOUT1 (I_OUT1=5.0 mA to 17.8 mA)
IOUT1 (I_OUT1=5.0 mA to 17.8 mA)
VISET (V_VISET=0.5 V to 1.8 V)
Figure 9 Constant Current Circuit (S-881300BPE)
Seiko Instruments Inc.
11