S-5843AC0DC-M5T1Y Datasheet, PDF (9/21 Pages) Seiko Instruments Inc – TEMPERATURE SWITCH IC

Rev.2.2_01
TEMPERATURE SWITCH IC (THERMOSTAT IC)
S-5843A Series
 Operation
1. Basic operation
The S-5843A Series is a temperature switch IC (thermostat IC) which detects temperature and sends a signal to an
external device. The users can select various combinations of the parameters such as the detection temperature, the
output form and logic, and hysteresis temperature.
Following is about the operation when the DET pin output logic is active "H".
After applying the power supply, the S-5843A Series starts to detect the temperature. If the temperature is lower than
the detection temperature (+TD), the DET pin output keeps "L". The temperature rises and exceeds the detection
temperature, the DET pin output is set to "H".
After the detection, the temperature drops and reaches the release temperature (+TD − THYS), the DET pin output
returns to "L".
Figure 7 is the timing chart.
Hysteresis temperature
(THYS)
Ambient temperature (Ta)
Detection temperature (TD)
H
DET pin output
L
Figure 7 Operation when DET Pin Output Logic is Active "H"
2. Prevention functions for false detection operation and false release operation
The S-5843A Series sets the start-up control sequence and the noise suppression time (tdelay) via the delay circuit. By
this, the S-5843A Series prevents false detection and false release operations which are caused by start-up and power
supply fluctuation.
Following is about the operation when the DET pin output logic is active "H".
2. 1 Operation at start-up
By the start-up control sequence, the S-5843A Series fixes the DET pin output "L" until the internal circuits become
stable immediately after start-up. After that, the S-5843A Series starts the operation for temperature detection.
The DET pin output keeps "L" if ambient temperature (Ta) is the detection temperature (+TD) or less. After that, if the
temperature rises and exceeds the detection temperature, and this status is held for the noise suppression time or
longer, the DET pin output is set to "H".
2. 2 Operation at power supply fluctuation
The DET pin output is set to "L", if ambient temperature is the detection temperature or less. If any power supply
fluctuation makes the internal circuit unstable, this status lasts shorter than the noise suppression time, the DET pin
output is not set to "H". Thus, false detection operation by power supply fluctuation can be prevented. This is as well
for the release operation.
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