S-817_1 Datasheet, PDF (17/52 Pages) Seiko Instruments Inc – SUPER-SMALL PACKAGE CMOS VOLTAGE REGULATOR

Rev.4.2_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 16 and 17.
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.
Note that by using a circuit in Figure16, it is impossible to set the better driving ability to the constant
amperage (IO) than the S-817 Series basically has.
To gain the driving ability which exceeds the S-817 Series, there’s a way to combine a constant current
circuit and a current boosting circuit, as seen in Figure 17.
The maximum input voltage for a constant current circuit is 10 V + the voltage for device (VO).
It is not recommended to add a capacitor between the VIN (power supply) and VSS pin or the VOUT
(output) and VSS pin because the rush current flows at power-on.
The following is a characteristics example of input voltage between VIN and VO vs. IO current (Typ. Ta
= 25°C) in constant current boosting circuit in Figure 17.
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.
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