 Data Sheet

Resistor values from the calculation are nonindustry standard,
using industry standard resistor values resulted in a new R

DIV

value of 99.8 kΩ. Due to the discrepancy of the calculated resistor
value to the industry standard value, the threshold of each
comparator also changed. Calculate the new threshold values
by using a simple voltage divider formula:

V1 = V

REF

R1/R

DIV

(37)

where V1 =

(

)

99.8

26.7

V

1

= 267.54 mV.

Therefore, V2 = 463.93 mV, V3 = 607.21 mV, and V4 = 712.42 mV.
Because the threshold of each comparator has changed, the time
when each comparator changes its output has also changed.
Calculate the new delay values for each comparator by using the
following equation:

(

)

+

=

REF

MIRROR

PULLUP

L

1

V

V1

R

R

C

t

1

ln

(38)

where t

1

= −1 µF(10 kΩ + 150 kΩ)ln

 −

1

mV

54

.

267

1

= 49.81 ms.

Therefore, t

2

= 99.78 ms, t

3

= 149.52 ms, and t

4

= 199.4 ms.

To calculate t

5

through t

8

, use Equation 32 to Equation 35:

=

REF

L

MIRROR

5

V

V4

C

R

t

ln

where t

5

= −150 kΩ × 1 µF × ln

1

mV

712.42

= 50.86 ms.

Therefore, t

6

= 74.83 ms, t

7

= 115.2 ms, and t

8

= 197.78 ms.

THRESHOLD AND TIMEOUT PROGRAMMABLE

VOLTAGE SUPERVISOR

Figure 31 shows a circuit configuration for a programmable
threshold and timeout circuit. The timeout, t

RESET

, defines the

duration that the input voltage (V

IN

) must be kept above the

threshold voltage to toggle the RESET signal, preventing the
device from operating when V

IN

is not stable. If V

IN

falls below

the threshold voltage, the RESET signal toggles quickly.

Figure 31. Programmable Threshold and Timeout Circuit

Figure 32. Threshold and Timeout Programmable Voltage Supervisor

Timing Diagram

During startup, the

guarantees a low output state

when V

CC

is still below the UVLO threshold, preventing the

voltage supervisor from toggling.
When V

IN

reaches the threshold set by the resistor divider (R1

and R2) and V

REF

, OUTA changes from low to high and starts to

charge the timeout capacitor (C

T

). If V

IN

is kept above the threshold

voltage and the voltage in C

T

reaches V

REF

, OUTB toggles. If V

IN

falls below the threshold voltage while C

T

is charging, the timeout

capacitor quickly discharges, preventing OUTB from toggling
while V

IN

is not stable.

In the condition that V

IN

is tied to V

CC

, the circuit operates

when V

CC

is more than the minimum operating voltage.

The threshold voltage (V

TH

) is configured by changing the

resistor divider or V

REF

. Calculate the threshold voltage by

 +

=

R2

R1

V

V

REF

TH

1

(39)

Timeout is adjusted by changing the values of the pull-up
resistor or the timeout capacitor. To set the timeout value,
determine the allowable current flowing through R

PULLUP

and

I

PULLUP

. When I

PULLUP

is known, calculate R

PULLUP

and C

T

by the

following formulas:

R

PULLUP

= V

CC

/I

PULLUP

(40)





=

CC

REF

PULLUP

RESET

T

V

V

ln

R

t

C

1

(41)

RESET

OUTB

OUTA

R

PULLUP

R1

R2

V

CC

C

T

V

IN

V

REF

12207-

129

RESET

V

TH

V

IN

t

RESET

t

RESET

12207-

130

Rev. 0 | Page 14 of 15

Part No.

Description 