HIGH RIPPLE-REJECTION AND LOW DROPOUT CMOS VOLTAGE REGULATOR

S-L2980 Series

Seiko Instruments Inc.

12

3. ON/OFF Pin

This pin starts and stops the regulator.

When the ON/OFF pin is set to OFF level, the operation of all internal circuits stops, the built-in P-

channel MOS FET output transistor between VIN pin and VOUT pin is turned off to make current

resistance of several hundreds k

Ω between the VOUT pin and VSS pin.

Furthermore, the structure of the ON/OFF pin is as shown in Figure 12. Since the ON/OFF pin is

neither pulled down nor pulled up internally, do not use it in the floating state. In addition, please note

that current consumption increases if a voltage of 0.3 V to VIN–0.3 V is applied to the ON/OFF pin.

When the ON/OFF pin is not used, connect it to the VIN pin in case the product type is “A” and to the

VSS pin in case of “B”.

Table 5

Product Type

ON/OFF Pin

Internal Circuit

VOUT Pin Voltage

Current Consumption

A

“H”: ON

Operate

Set value

A

“L”: OFF

Stop

B

“H”: OFF

Stop

B

“L”: ON

Operate

Set value

VSS

ON/OFF

VIN

Figure 12

The S-L2980 Series needs an output capacitor between VOUT pin and VSS pin for phase compensation.

A ceramic capacitor whose capacitance is 1.0

conductor) capacitor, a tantalum capacitor or an aluminum electrolyte capacitor is used, the capacitance

should be 2.2

μF or more and the ESR should be 10 Ω or less.

The value of the output overshoot or undershoot transient response varies depending on the value of the

output capacitor.

Sufficient evaluation including temperature dependency in the actual environment is needed.

*1. If the product whose output voltage is 1.7 V or less will be used, the capacitance should be 2.2

μF

or more.