MAX8211 Maxim, MAX8211 Datasheet - Page 5

• Manufacturer Part Number: MAX8211
• Description: Microprocessor Voltage Monitors with Programmable Voltage Detection
• Manufacturer: Maxim

Calculate resistor values for Figure 3 as follows:
Figure 5 shows an alternate circuit, suitable only when the
voltage being detected is also the power-supply voltage
for the MAX8211 or MAX8212.
Figure 4. MAX8211/MAX8212 Threshold Trip Voltage vs.
Ambient Temperature
1) Choose a value for R1. Typical values are in
2) Calculate R2 for the desired upper trip point
3) Calculate R3 for the desired amount of
R2 = R1
R3
R3
the 10k to 10M range.
V
hysteresis, where V
or, if V
U
using the formula:
R2
R2
1.250
1.230
1.210
1.190
1.170
1.150
1.130
1.110
1.090
1.070
1.050
+
= V
-55
(V U
(V
(V L
(V U
________________________________________________________________________________________
(V U
IN
V TH
:
V+ = 16.5V
V TH )
V TH )
V+ = 2V
V L )
-25
V L )
V TH )
with Programmable Voltage Detection
L
is the lower trip point:
T
R1
R2
A
25
(°C)
R2
Microprocessor Voltage Monitors
(V U 1.15V)
(V L 1.15V)
(V U
75
(V +
1.15V
(V U
V L )
1.15V)
125
V L )
Calculate resistor values for Figure 5 as follows:
The circuit of Figure 5 will detect when a 5.0V (nominal)
supply goes below 4.5V, which is the V
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.
Figure 5. MAX8211 Logic-Supply Low-Voltage Detector
1) Choose a value for R1. Typical values are in
2) Calculate R2:
3) Calculate R3:
Low-Voltage Detector for Logic Supply
the 10k to 10M range.
R2
R3
48.7k
20M
750k
1%
1%
R3
R2
1%
R1
R1
R1
HYST
THRESH
(V L
(V U
1.15V
V TH
V TH )
V L )
MAX8211
V
V+
IN
R1
GND
OUT
(V L 1.15V)
V
(LOW FOR
V
1.15V
OUT
IN
MIN
< 4.5V)
normally
5