MAX836EUS+T Maxim Integrated Products, MAX836EUS+T Datasheet - Page 5

• Manufacturer Part Number: MAX836EUS+T
• Description: IC MONITOR VOLT LP SOT143-4
• Manufacturer: Maxim Integrated Products
• Type: Simple Reset/Power-On Resetr

Specifications of MAX836EUS+T

• Number Of Voltages Monitored: 1
• Output: Open Drain or Open Collector
• Reset: Active Low
• Reset Timeout: 80 µs Typical Propagation Delay
• Voltage - Threshold: Adjustable/Selectable
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-143, SOT-143B, TO-253AA
• Manual Reset: Not Resettable
• Watchdog: No Watchdog
• Supply Voltage (max): 11 V
• Supply Voltage (min): 2.5 V
• Supply Current (typ): 6.5 uA
• Maximum Power Dissipation: 320 mW
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: MAX836EUS+T; MAX836EUS+TTR

both parts. For the MAX836, select the ratio of resistors
R1 and R2 so that IN sees 1.204V when the monitor volt-
age falls to or rises above the desired trip point (V
R3 adds hysteresis and is typically an order of magni-
tude larger than R1 or R2. The current through R1 and
R2 should be at least 500nA to ensure that the 12nA
maximum input current does not shift the trip point sig-
nificantly. Capacitor C1 adds additional noise rejection.
The MAX836/MAX837 can monitor voltages other than
V
Programming the Trip Voltage section. The monitored
voltage (V
less than V
Figure 4 shows a basic heater temperature-control cir-
cuit. Upon power-up, OUT is high and the n-channel
MOSFET turns on. Current flows through the heating
element (R4), warming the surrounding area. R2 is a
negative-temperature-coefficient thermistor and as tem-
perature increases, its resistance decreases. As the
thermistor heats up and its resistance decreases, the
MAX837’s voltage at IN decreases until it reaches the
1.204V threshold voltage. At this point, OUT goes low,
turning off the heating element. The thermistor cools
and the voltage at IN rises until it overcomes the
MAX837’s hysteresis (6mV). OUT returns high when this
point is reached, turning on the heating element again.
This cycle repeats as long as power is applied.
Figure 2. Adding Hysteresis to the Comparator
CC
NOTE: C1 ADDS ADDITIONAL NOISE IMMUNITY
(Figure 3). Calculate V
Monitoring Voltages Other than V
V
MON
CC
CC
.
) is independent of V
0.1μF
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Heater Temperature Control
GND
V
CC
MAX837
R1
4-Pin Micropower Voltage Monitors
TRIP
OUT
IN
CC
as shown in the
. V
R2
IN
R3
must be 1V
OUT
C1
TRIP
CC
).
Determine the thermistor’s resistance (R2) at the
desired temperature. Then, using R2’s resistance and
half the resistance of R3, calculate R1’s value with the
following formula:
Figure 3. Monitoring Voltages Other than V
Figure 4. Heater Temperature Control
0.1μF
0.1μF
V
CC
MAX837
V
GND
R1 = (R2 + R3)
CC
OUT
GND
V
IN
CC
R1
MAX837
THERMISTOR
WITH
NEGATIVE
COEFFICIENT
= (
R2 + R3)
OUT
⎛
⎜
⎝
IN
(
R3
1.204
R1
1.204
V
V
CC
CC
V
CC
T
R2
- 1 Ω
CC
V
- 1
MON
)
⎞
⎟
⎠
R1
R2
HEATING
ELEMENT
R4
5