HIGH-WITHSTAND VOLTAGE BUILT-IN DELAY CIRCUIT (EXTERNAL DELAY TIME SETTING) VOLTAGE DETECTOR
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 MΩ min., the S-1011 Series N / Q
type: 6.8 MΩ min.) to make the error small, RA and RB should be selected such that the error is within the allowable
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 ×
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 × 1 +
= −VDET × 1 +
(= −VDET × 1 +
RB || RSENSE
RB × RSENSE
RB + RSENSE
By using equations (1) and (2), the error is calculated as −VDET ×
The error rate is calculated as follows by dividing the error by the right-hand side of equation (1).
RA × RB
RSENSE × (RA + RB)
× 100 [%] =
RA || RB
× 100 [%]
As seen in equation (3), the smaller the resistance values of RA and RB compared to RSENSE, the smaller the error
Seiko Instruments Inc.