TEMPERATURE SWITCH IC (THERMOSTAT IC) WITH LATCH

S-5840B Series

Seiko Instruments Inc.

8

Operation

1.

Basic operation

The S-5840B Series is a temperature switch IC (thermostat IC) which detects the temperature and sends a signal to an

external device. The users can select a combination of the parameters such as detection temperature and release

voltage.

Following is about the operation when the DET pin output logic is active "H".

When the power supply voltage is turned on, the DET pin voltage goes to "L" since the flip-flop circuit in the detection

circuit is cleared by the voltage detection circuit. Temperature detection then starts and the DET pin is held "L" as long

as the temperature is lower than the detection temperature. When the temperature rises and when the temperature

exceeds the detection temperature; longer than the time defined by the capacitor connected to the CD pin, the DET pin

goes to "H". Once the over-temperature is detected and the DET pin goes to "H", the state is held by the flip-flop circuit.

in voltage detector circuit to reset the internal circuit.

Using the internal reference voltage and built-in temperature sensor, a detection temperature accuracy of

±2.5°C is

achieved in the S-5840B Series.

2.

Noise suppression circuit

The noise suppression circuit prevents malfunction of the temperature switch caused by noise.

The noise suppression circuit starts charging the capacitor connected to the CD pin when the output of the internal

comparator enters the active state due to an external noise or a rapid change in the power supply voltage. In the normal

operation, the flip-flop circuit is set when the capacitor is charged to a certain voltage. But in the noise triggered

operation, the comparator output goes back to the inactive state and the CD pin voltage is held "L" since the charging of

Noise suppression time coefficient (Ta =

+25°C): 6.4 typ.

occurs in delay time if the capacitor has a leak current.