EXTERNAL TRANSISTOR TYPE CMOS VOLTAGE REGULATOR

S-816 Series

8

Seiko Instruments Inc.

Operation

1. Basic Operation

Figure 7 shows a block diagram of the S-816 Series.

sink driver. By regulating the base current of the external PNP transistor, the IC maintains a constant

output voltage that is not susceptible to an input voltage variation or temperature variation.

OUT

IN

EXT

VOUT

VSS

OFF

ON/

VIN

Current Source

Overcurrent

Protection

Circuit

Error

Amplifier

Sink

Driver

+

−

+

−

Figure 7

2. Internal Circuits

2.1. Shutdown Pin (

OFF

ON/

Pin)

This pin activates and deactivates the regulating operation.

PNP transistor to off. All the internal circuits stop working, and substantial savings in current consumption

(approx. 0.5 M

Ω) inside the IC in order to ensure you power cut off of the external PNP transistor.

The shutdown pin is configured as shown in Figure 8. Since neither pull-up or pull-down is performed

internally, please avoid using the pin in a floating state. Also, be sure to refrain from applying a voltage of

0.3 V to 2.4 V to this pin lest the current consumption increase. When this shutdown pin is not used,

leave it coupled to the VIN pin.

Table 5

Shutdown Pin

Internal Circuit

EXT Pin Voltage

VOUT Pin Voltage

"H"

Activated

Set value

"L"

Deactivated

Hi-Z

VIN

VSS

OFF

ON/

Figure 8