How do I select a PTC thermistor to use with Thermoflagger™?
The PTC thermistor used with Thermoflagger™ should be selected considering the IC detect voltage/constant current and PTC thermistor characteristic.
The TCTH0 series is provided with a constant current of IPTCO10μA/1μA (Typ.) at the PTCO terminal.
A FLAG signal is output when the voltage at the PTCO voltage (PTC thermistor combined resistance×IPTCO) exceeds the detect voltage VDET 0.5V (Typ.).
The PTC thermistor combined resistance×IPTCO > VDET
For the TCTH01 Series. When the PTC thermistor combined resistance exceeds 500kΩ (Typ.), the IC outputs a FLAG signal.
For the TCTH02 series. When the PTC thermistor combined resistance exceeds 50kΩ (Typ.), the IC outputs a FLAG signal.
The temperature at which the combined resistance of the PTC thermistor becomes 500kΩ/50kΩ is the reference for the detection temperature.
| Characteristics | Symbol | Test condition | Tj = 25°C | Tj = -40 to 125°C | Unit | |||
|---|---|---|---|---|---|---|---|---|
| Min | Typ. | Max | Min | Max | ||||
| PTCO output current | IPTCO | TCTH01xxE, VDD = 1.7V to 5.5V | 0.8 | 1.00 | 1.22 | 0.72 | 1.32 | μA |
| TCTH02xxE, VDD = 1.7V to 5.5V | 8.0 | 10.0 | 12.2 | 7.2 | 13.2 | |||
| Detect Voltage | VDET | VDD = 3.3V | 0.42 | 0.50 | 0.58 | 0.36 | 0.64 | V |
The following table shows the selection table for Thermoflagger™ and Murata Manufacturing PTC thermistors (POSISTOR).
The detection temperature depends on the board conditions, so please verify thoroughly before use.
| Thermoflagger™ Product name |
Murata Manufacturing POSISTOR product name |
Overheat detection temperature (Reference) |
|---|---|---|
TCTH021AE |
PRF18AR471QB5RB | 150ºC |
| PRF18BA471QB5RB | 140ºC | |
| PRF18BB471QB5RB | 130ºC | |
| PRF18BC471QB5RB | 120ºC | |
| PRF18BD471QB5RB | 110ºC | |
| PRF18BE471QB5RB | 100ºC | |
| PRF18BF471QB5RB | 90ºC | |
| PRF18BG471QB5RB | 80ºC | |
| PRF15BA102RB6RC | 136ºC | |
| PRF15BB102RB6RC | 126ºC | |
| PRF15BC102RB6RC | 116ºC | |
| PRF15BD102RB6RC | 106ºC | |
| PRF03BB541NB7RL | 135ºC | |
TCTH011AE |
PRF15BB103RB6RC | 122ºC |
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