S-817 Datasheet, PDF (17/50 Pages) Seiko Instruments Inc – SUPER-SMALL PACKAGE CMOS VOLTAGE REGULATOR

Rev.3.0_00
SUPER-SMALL PACKAGE CMOS VOLTAGE REGULATOR
S-817 Series
The S-817 Series can be configured as a constant current circuit. Refer to Figure 15 and 16.
Constant amperage (I_O) is calculated using the following equation (V_OUT(E): Effective output voltage):
I_O = (V_OUT(E) ÷ R_L) +I_SS.
Please note that it is impossible to set constant amperage I_O 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 (V_O). 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 V_IN and V_O in circuit (2) vs. I_O current characteristics
V_IN, V_O pins, Input voltage - I_O current
S-817A11ANB, S-817B11AMC, Tr : 2SK1213Y, R_{1 :} 1 kΩ, V_O=2 V
0.60
RL=1.83 Ω
0.50
2.2 Ω
0.40
2.75 Ω
0.30
3.67 Ω
5.5 Ω
0.20 _{11 Ω}
0.10
0.00
1.4
1.6
1.8
2
VIN−VO(V)
2.2
2.4
Seiko Instruments Inc.
17