S816 datasheet(8/24 Pages) SII

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EXTERNAL TRANSISTOR TYPE CMOS VOLTAGE REGULATOR

S-816 Series

Rev.6.1_00

Seiko Instruments Inc.



Operation

1. Basic Operation

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

The error amplifier compares the reference voltage (Vref) with feedback voltage (Vfb), which is the output

voltage resistance-divided by feedback resistors (RA and RB). It maintains a constant output voltage that

is not susceptible to an input voltage variation or temperature variation to regulate the base current of the

external PNP transistor.

EXT

VOUT

VSS

VIN

Vref

Current Source

Overcurrent

Protection

Circuit

Pull-Up

Reisitance

Error

Amplifier

Sink

Driver

−

ON/OFF

OUT

Vfb

Remark The diode inside the IC is a parasitic diode.

Figure 7

2. Internal Circuits

2.1. ON/OFF Pin

This pin starts and stops the regulator.

When the ON/OFF pin is set to OFF level, the entire internal circuits stop operating, and the VIN voltage

appears through the EXT pin, prodding the external PNP transistor to off, reducing current consumption

significantly. In this condition, the EXT pin is pulled up to VIN by a pull-up resistance (approx. 0.5 M

Ω)

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

The ON/OFF 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 ON/OFF pin is not used, leave

it coupled to the VIN pin.

Table 5

VIN

VSS

ON/OFF

ON/OFF Pin

Internal Circuit

EXT Pin Voltage

VOUT Pin Voltage

"H": ON

Operate

VIN

−VBE

Set value

"L": OFF

Stop

VIN

Hi-Z

Figure 8

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