Calculate resistor values for Figure 3 as follows:

1) Choose a value for R1. Typical values are in

the 10k

Ωto 10MΩrange.

2) Calculate R2 for the desired upper trip point

3) Calculate R3 for the desired amount of

Figure 5 shows an alternate circuit, suitable only when the

voltage being detected is also the power-supply voltage

for the MAX8211 or MAX8212.

Calculate resistor values for Figure 5 as follows:

1) Choose a value for R1. Typical values are in

the 10k

Ωto 10MΩrange.

2) Calculate R2:

3) Calculate R3:

Low-Voltage Detector for Logic Supply

The circuit of Figure 5 will detect when a 5.0V (nominal)

specified in logic systems. The selected resistor values

ensure that false undervoltage alarms will not be gener-

ated, even with worst-case threshold trip values and

resistor tolerances. R3 provides approximately 75mV of

hysteresis.

R3

R1

(VU VL)

1.15V

=×

−

R2

R1

(VL VTH)

VTH

R1

(VL 1.15V)

1.15V

=×

−

=×

−

R3

R2

(VL VTH)

(VU VL)

R2

(VL 1.15V)

(VU VL)

=×

−

−

=×

−

−

R3

R2

(V

VTH)

(VU VL)

R2

(V +

1.15V)

(VU VL)

=×

+−

−

=×

−

−

R2 = R1

(VU VTH)

VTH

R1

(VU 1.15V)

1.15V

×

−

=×

−

Microprocessor Voltage Monitors

with Programmable Voltage Detection

________________________________________________________________________________________

5

-55

°C)

1.250

1.230

1.210

1.190

1.170

1.150

1.130

1.110

1.090

1.070

1.050

-25

25

75

125

V+ = 16.5V

V+ = 2V

Figure 4. MAX8211/MAX8212 Threshold Trip Voltage vs.

Ambient Temperature

HYST

MAX8211

OUT

GND

V+

R3

48.7k

Ω

1%

R2

2.2M

Ω

1%

R1

750k

Ω

1%

(LOW FOR

THRESH

Figure 5. MAX8211 Logic-Supply Low-Voltage Detector