S1011 datasheet(21/43 Pages) SII

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HIGH-WITHSTAND VOLTAGE BUILT-IN DELAY CIRCUIT (EXTERNAL DELAY TIME SETTING) VOLTAGE DETECTOR

Rev.1.2_00

S-1011 Series

Seiko Instruments Inc.

2. SENSE pin

2. 1 Error when detection voltage is set externally

The detection voltage for the S-1011 Series is 10.0 V max., however, in the SENSE detection product with

−VDET =

10.0 V, the detection voltage can be set externally by connecting a node that was resistance-divided by the resistor

(RA) and the resistor (RB) to the SENSE pin as shown in Figure 31.

For conventional products without the SENSE pin, external resistor cannot be too large since the resistance-divided

node must be connected to the VDD pin. This is because a feed-through current will flow through the VDD pin

when it goes from detection to release, and if external resistor is large, problems such as oscillation or larger error

in the hysteresis width may occur.

In the S-1011 Series, RA and RB in Figure 31 are easily made larger since the resistance-divided node can be

connected to the SENSE pin through which no feed-through current flows. However, be careful of error in the

current flowing through the internal resistance (RSENSE) that will occur.

Although RSENSE in the S-1011 Series is large (the S-1011 Series E / G type: 26 M

Ω min., the S-1011 Series N / Q

type: 6.8 M

Ω min.) to make the error small, RA and RB should be selected such that the error is within the allowable

limits.

2. 2 Selection of RA and RB

In Figure 31, the relation between the external setting detection voltage (VDX) and the actual detection voltage

(

−VDET) is ideally calculated by the equation below.

VDX =

−VDET ×

()

··· (1)

However, in reality there is an error in the current flowing through RSENSE.

When considering this error, the relation between VDX and

−VDET is calculated as follows.

VDX =

−VDET ×

()

RB || RSENSE

−VDET ×













× RSENSE

+ RSENSE

−VDET ×

()

RSENSE × −VDET

··· (2)

By using equations (1) and (2), the error is calculated as

−VDET ×

RSENSE .

The error rate is calculated as follows by dividing the error by the right-hand side of equation (1).

× RB

RSENSE

× (RA + RB) ×

100 [%] =

RA || RB

RSENSE × 100 [%]

··· (3)

As seen in equation (3), the smaller the resistance values of RA and RB compared to RSENSE, the smaller the error

rate becomes.

S1011 Datasheet(PDF) 21 Page - Seiko Instruments Inc

S1011 Datasheet(HTML) 21 Page - Seiko Instruments Inc

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