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POWER THERMOSTAT. ELM341 Datasheet

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POWER THERMOSTAT. ELM341 Datasheet






ELM341 THERMOSTAT. Datasheet pdf. Equivalent




ELM341 THERMOSTAT. Datasheet pdf. Equivalent





Part

ELM341

Description

LOW POWER THERMOSTAT

Manufacture

ELM Electronics

Datasheet
Download ELM341 Datasheet


ELM Electronics ELM341

ELM341; ELM341 Low Power Thermostat Description The ELM341 is a complete temperature me asurement and control system in an 8 pi n package. It automatically reverts to a very low power sleep mode between mea surements, making it suitable for batte ry operation. This integrated circuit i s designed to compare two resistances a nd drive an output pin depending on the relative value of.


ELM Electronics ELM341

each. Typically, one of the resistors w ill be an NTC thermistor, and the other one will be a temperature independent resistor (whether fixed or variable). W hen the magnitude of the resistance con nected to pin 2 exceeds the value www.D ataSheet4U.com of the resistance connec ted to pin 3, the output pin will be dr iven to a high state. Hysteresis mainta ins the output in .


ELM Electronics ELM341

that state until the relative values dif fer by approximately 8% (or typically 2 °C for a 10KΩ thermistor). To reduce the possibility of sporadic outputs, a condition must exist for three success ive cycles, or 6 seconds, before the ou tput pin can change state. Features • • • • • • • Low power CMOS design Wide supply range - 3.0 to 5.5 volt operation Built-in proporti.



Part

ELM341

Description

LOW POWER THERMOSTAT

Manufacture

ELM Electronics

Datasheet
Download ELM341 Datasheet




 ELM341
ELM341
Low Power Thermostat
Description
The ELM341 is a complete temperature
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.
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
www.DataSheetht4eUre.csoismtance 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 10K
thermistor).
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.
Applications
• Backup thermostats
• Under or over temperature alarm circuits
Features
• Low power CMOS design
• 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
Connection Diagram
PDIP and SOIC
(top view)
VDD 1
R1 2
R2 3
reset 4
8 VSS
7 Out
6 MIP
5 Cap
Block Diagram
reset 4
2
R1 3
R2
5
VDD
Control
Sleep
Timer
Measurement in Progress (busy)
6 MIP
Overrange
Analog to
Digital
Converter
R1 > R2
3 Consecutive
Measurements
7 Out
ELM341DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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 ELM341
ELM341
Pin Descriptions
VDD (pin 1)
This pin is the positive supply pin. Internal
circuitry connected to this pin is used to provide
power on reset of the microprocessor, so an
external reset signal is normally not required.
Refer to the Electrical Characteristics section for
further information.
R1 (pin 2)
One of the two resistance input pins. A
temperature dependent resistance is usually
connected to this input for heating or under-
temperature alarm type applications. When the
www.DataSheevt4aUlu.ecoomf this resistor is greater than the value of
the resistance connected to pin 3 (for three
successive measurements) the output will be
driven high.
R2 (pin 3)
The reference resistance is connected to this pin
for heating applications (and the temperature
dependent resistance is connected here for
cooling applications). The other end of this
resistor is connected to the integrating capacitor.
reset (pin 4)
The active low reset input. An internal pullup
resistor is provided for convenience. If unused,
this pin may be connected to VDD or left open.
Cap (pin 5)
Temperature measurements are made by
determining the time to charge and discharge this
integrating capacitor. Pin 5 forces the capacitor to
a known voltage for these measurements though,
resulting in large current flows. To limit these
capacitor currents, and protect the ELM341, a
series resistor must be connected to this pin. The
value of the resistance, and of the capacitance, is
not critical to the measurements.
MIP (pin 6)
This pin provides a logic high level output while
the ELM341 is busy (measurements are in
progress). It is suitable for directly driving an LED
through a current limiting resistor. As a warning,
this output pulses rapidly if either resistor input is
found to be open circuited.
Out (pin 7)
The output pin assumes a logic high state once
the resistance of R1 exceeds that of R2 for three
successive measurement cycles. The output is
maintained until R1 is less than R2 by the
hysteresis amount for an additional three counts.
Note: Consideration must be given to the fact that
this output is in a tri-state (open circuit) mode
each time the circuit wakes from sleep to take a
measurement. This mode lasts for approximately
300µs, which is not generally long enough to
affect a relay output, but certainly long enough to
be seen by high-speed logic circuits.
VSS (pin 8)
Circuit common is connected to this pin. This is
the most negative point in the circuit.
Ordering Information
These integrated circuits are available in either the 300 mil plastic DIP format, or in the 200 mil SOIC surface
mount type of package. To order, add the appropriate suffix to the part number:
300 mil Plastic DIP............................... ELM341P
200 mil SOIC..................................... ELM341SM
All rights reserved. Copyright ©1999 Elm Electronics.
Every effort is made to verify the accuracy of information provided in this document, but no representation or warranty can be
given and no liability assumed by Elm Electronics with respect to the accuracy and/or use of any products or information
described in this document. Elm Electronics will not be responsible for any patent infringements arising from the use of these
products or information, and does not authorize or warrant the use of any Elm Electronics product in life support devices and/or
systems. Elm Electronics reserves the right to make changes to the device(s) described in this document in order to improve
reliability, function, or design.
ELM341DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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 ELM341
ELM341
Absolute Maximum Ratings
Storage Temperature....................... -65°C to +150°C
Ambient Temperature with
Power Applied....................................-40°C to +85°C
Voltage on VDD with respect to VSS............ 0 to +7.5V
Voltage on any other pin with
respect to VSS........................... -0.6V to (VDD + 0.6V)
Note:
Stresses beyond those listed here will likely damage
the device. These values are given as a design
guideline only. The ability to operate to these levels
is neither inferred nor recommended.
Electrical Characteristics
All values are for operation at 25°C and a 5V supply, unless otherwise noted. For further information, refer to note 1 below.
Characteristic
www.DataSheet4U.com
Supply Voltage, VDD
Minimum Typical Maximum Units
3.0 5.0 5.5 V
Conditions
VDD rate of rise
0.05
V/ms see note 2
Average Supply Current, IDD
0.008
0.002
1.0
0.6
2.4 mA VDD = 5V, see note 3
2.4 mA VDD = 3V, see note 3
Frequency of measurements
2.0 sec see note 4
Reset pin internal pullup resistance
300
470
600 Ksee note 5
R1C or R2C time constant
500
500,000
µs see note 6
Input low voltage - reset pin
VSS
0.15 VDD
V
Input high voltage - reset pin
0.85 VDD
VDD
V
Output low voltage
0.6 V Current (sink) = 8.7mA
Output high voltage
VDD - 0.7
V Current (source) = 5.4mA
Notes: 1. This integrated circuit is produced with a Microchip Technology Inc.’s PIC12C5XX as the core embedded
microcontroller. For further device specifications, and possibly clarification of those given, please refer to the
appropriate Microchip documentation.
2. This spec must be met in order to ensure that a correct power on reset occurs. It is quite easily achieved
using most common types of supplies, but may be violated if one uses a slowly varying supply voltage, as
may be obtained through direct connection to solar cells, or some charge pump circuits.
3. Integrated circuit only. Does not include any LED or drive currents. Minimum currents represent those which
are typically found between measurements when in the low power sleep mode.
4. If a measured resistance is determined to be out of limits, the frequency of measurements is increased to
provide visual feedback as well as a faster recovery.
5. The value of the pullup resistance is supply and temperature dependent.
6. One should also maintain R1 and R2 to not less than about 5K. When C is chosen, select the pin 5 current
limiting resistance so that RLIMC is less than 1msec, and RLIM is greater than 1K.
ELM341DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
3 of 4



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