AN2504 - Application note

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sometimes necessary to make adjustments during prototyping. This can be achieved by

connecting of external divider (see Figure 8). This hook up can be used if the required

threshold of voltage detector is lower than the desired monitored voltage.

To maintain detector accuracy, the current flow through the divider should be significantly

higher than the 0.9µA operating current required by the STM1061. A 90µA bleeder current is

sufficient in most applications.

Figure 8.

Example:

The voltage on the divider is:

That is why:

The value of R2 resistor is then:

We will choose the nearest values of the resistors (e.g. from E24):

R1 = 18k

Ω, R2 = 2.2kΩ.

AI12910

VSUPPLY

R2

VCC

STM1061N

OUT

VSS

R1

Threshold of STM1061 detector:

Desired threshold:

Recommended bleeder current:

I = 90µA

R1+R2 is then:

V

CC

R

1

R

2

+

--------------------V

SUPPLY

V

==

R

1

V

V

SUPPLY

-------------------------R

1

R

2

+

()

1.6V

1.8V

------------20k

Ω

17.7k

Ω

==

=

R

2

20k

Ω 17.7kΩ 2.2kΩ

=

–

=