SUPER-SMALL PACKAGE CMOS VOLTAGE REGULATOR
The S-817 Series can be configured as a constant current circuit. Refer to Figure 15 and 16.
Constant amperage (IO) is calculated using the following equation (VOUT(E): Effective output voltage):
IO = (VOUT(E) ÷ RL) +ISS.
Please note that it is impossible to set constant amperage IO in case of circuit (1) of Figure 15 to the
value exceeding the drive ability of the S-817.
However, circuit (2) of Figure 16 is an example to set constant amperage to the value exceeding the
drive ability of the S-817. Circuit (2) incorporates a current boosting circuit. The maximum input voltage
of the constant current circuit is the value obtained by adding 10 V to voltage of the device (VO). It is not
recommended to attach a capacitor between the S-817 power source VIN and VSS pin or between
output VOUT and VSS pin because rush current flows at powering on. An example of input voltage
between VIN and VO in circuit (2) vs. IO current characteristics
VIN, VO pins, Input voltage - IO current
S-817A11ANB, S-817B11AMC, Tr : 2SK1213Y, R1 : 1 kΩ, VO=2 V
0.20 11 Ω
Seiko Instruments Inc.