HIGH-PRECISION VOLTAGE DETECTOR

S-807 Series

Seiko Instruments Inc.

5

Advantage over the S-805 Series

The S-807 Series, in comparison with conventional reset ICs such as the S-805 Series, offers greater detection voltage precision

(twice that of conventional units) and lower current consumption (half that of conventional units). These characteristics result in

the following advantages over conventional units.

1. Advantages of greater detection voltage precision

1.1 Detecting lithium battery service life

The discharge characteristics of lithium batteries are

shown in Figure 4. When using the S-805 Series,

the service life can be detected over t1. When

using the S-807 Series, it can be detected over t2.

This improvement in detection precision of the S-

807 Series means that batteries can be used over

more of their service life.

1.2 Detecting a power voltage at two points

It is usual for the CPU to detect the power voltage

at two points, one to caution and the other to reset.

The service life of battery may also be detected at

two points, one to caution and the other to request

immediate replacement.

Two voltage values to be detected (No. 1 and No.

2) do not cross and the voltage can be detected

correctly.

1.3 Voltage drop when modifying detection voltage

If no voltage to be detected is suitable, the voltage

can be set higher in Nch open-drain output

products by using a resistor divider. (Example :

when detecting 6V or 9V.)

When 8V is detected using the S-8054HN (a

4V

±5% device), the -Vdet tolerance becomes

2

×4.00×±0.05=0.8V (R1=R2). In constrast, the S-

80740AN (a 4V

±2.4% device) can hold down the

tolerance to 2

×4.00×±0.024=0.384V (R1=R2).

Must be close

V

t

No. 2

No. 1

Figure 5

t1

S-807

S-805

V

t

Figure 4

t2

R2

R1

Figure 6

Nch open-drain

output product

S-807

XXAN/SN