S13A1 datasheet(33/75 Pages) SII

33 / 75 page

HIGH RIPPLE-REJECTION LOW DROPOUT HIGH OUTPUT CURRENT CMOS VOLTAGE REGULATOR

Rev.2.0_00

S-13A1 Series

Seiko Instruments Inc.

8. Inrush current limit circuit

The S-13A1 Series has a built-in inrush current limit circuit to limit the inrush current and the overshoot of the output

voltage generated at power-on or at the time when the ON / OFF pin is set to ON. The inrush current is limited to

500 mA typ. The inrush current limit circuit starts to operate from the following times.

• Immediately after power-on

• At the time when the ON / OFF pin is set to ON

Figure 33 shows the relation between the inrush current limit time (tRUSH) and the inrush current limit capacitor (CSS).

Typ.

Max.

Min.

2.0

1.6

1.2

0.8

0.2

0.5

1.5

CSS [nF]

0.4

0.6

1.8

1.4

1.0

Figure 33

Ta =

+25°C

(1) CSS = 0 nF

tRUSH is determined by the internal capacitor (about 20 pF) and the time constant of the built-in constant current

(about 0.04

μA). tRUSH value is 0.28 ms min., 0.40 ms typ., 0.52 ms max.

(2) CSS

≥ 1 nF

tRUSH can be adjusted by the CSS which is connected externally between the SSC pin

*1 and the VSS pin. It is

calculated by the following formula depending on the built-in constant (about 1

μA) and the CSS time constant.

The inrush current limit coefficient is 0.49 min., 0.7 typ., 0.91 max. at Ta =

+25°C.

tRUSH [ms] = the inrush current limit coefficient

× CSS [nF]

(3) 0 nF < CSS < 1 nF

Since the internal capacitor, the built-in constant current and CSS have a variation each, tRUSH is the one of following

(a) and (b) in which the time is longer.

(a) The time determined by the internal capacitor (about 20 pF) and the time constant of the built-in constant

current (about 0.04

μA).

(b) The time determined by CSS connected externally between the SSC pin

*1 and the VSS pin and the built-in

constant current (about 1

μA).

When 0 nF < CSS< 1 nF, tRUSH is the range of the shaded area shown in Figure 33.

*1. Types in which output voltage is internally set of HSOP-8A, HSOP-6, SOT-89-5 only.

S13A1 Datasheet(PDF) 33 Page - Seiko Instruments Inc

S13A1 Datasheet(HTML) 33 Page - Seiko Instruments Inc

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