ELM341
Low Power Thermostat
Description
Features
The ELM341 is
a
complete temperature
• Low power CMOS design
measurement and control system in an 8 pin
package. It automatically reverts to a very low power
sleep mode between measurements, making it
suitable for battery operation.
• Wide supply range - 3.0 to 5.5 volt operation
• Built-in proportional hysteresis
• Measurement in progress output
• Time delay on operate improves noise immunity
• Internal pullup resistor on the reset input
• High current drive outputs - up to 25 mA
• Sleep mode reduces power requirements
This integrated circuit is designed to compare
two resistances and drive an output pin depending
on the relative value of each. Typically, one of the
resistors will be an NTC thermistor, and the other
one will be a temperature independent resistor
(whether fixed or variable). When the magnitude of
the resistance connected to pin 2 exceeds the value
of the resistance connected to pin 3, the output pin
will be driven to a high state. Hysteresis maintains
the output in that state until the relative values differ
by approximately 8% (or typically 2°C for a 10KW
thermistor).
Connection Diagram
PDIP and SOIC
(top view)
To reduce the possibility of sporadic outputs, a
condition must exist for three successive cycles, or 6
seconds, before the output pin can change state.
1
2
3
4
8
7
6
5
VDD
R1
VSS
Out
MIP
Cap
R2
Applications
reset
• Backup thermostats
• Under or over temperature alarm circuits
Block Diagram
VDD
Sleep
Timer
Control
4
reset
Measurement in Progress (busy)
2
6
7
MIP
Out
3
R1
Overrange
R2
Analog to
Digital
Converter
R1 > R2
3 Consecutive
Measurements
5
ELM341DSB
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