Datasheet TCTH011AE, TCTH012AE, TCTH021AE, TCTH022AE, TCTH011BE, TCTH012BE, TCTH021BE, TCTH022BE (Toshiba) - 9

TCTH0xxxE Series 10.3. How to choose PTC thermistor
The resistor value of PTC thermistor is increased when the temperature exceeds threshold. PTCO voltage (VPTCO) generates with PTC thermistor characteristics and PTCO output current. PTCGOOD outputs “Low” when PTC PTCO voltage is higher than the detect voltage (VDET). There are 2 types of products, have different PTCO output current. Select PTC thermistor matches each PTCO output current. Refer to the following.
10.3.1. Usage with single PTC thermistor
Refer to the following to select a PTC thermistor for IC detecting when resistance of PTC thermistor becomes α times the one on normal conditions. VDET (Max.) V < PTC thermistor resistance at normal operation < DET (Min.) IPTCO (Min.) × α IPTCO (Max.) × β α: The rate of changing PTC thermistor resistance (α = resistance at over temperature operation) resistance at normal operation β: VDET margin coefficient, Set with guideline as 10 ≤ β ≤ α/4 Note: Design for PTC thermistor resistance variation and margins. Ex.) Reference PTC thermistor resistance for single pc. PTCO output current PTC thermistor resistance (25 °C) Product name (Typ.) α = 50, β = 10 α = 100, β = 10 TCTH01xxE 1 μA 17.8 kΩ to 27 kΩ 9.1 kΩ to 27 kΩ TCTH02xxE 10 μA 1.78 kΩ to 2.7 kΩ 910 Ω to 2.7 kΩ
10.3.2. Using several (N pcs) PTC thermistors
When using several PTC thermistors, select the thermistors with same resistance value at 25 °C. if using different thermistors in same system, the IC does not correctly detect the setting temperature as blow. Maximum number of PTC thermistors can be connected is around 30 pcs. Ex.) Refer next formula to select the PTC thermistors, to detect with this IC when the resistor value changed to α times when one of the PTC thermistors is overheated, using N pcs of PTC thermistors have same resistor value at 25 °C. VDET (Max.) V < PTC thermistor resistance at normal operation < DET (Min.) IPTCO (Min.) × (α + N - 1) IPTCO (Max.) × β × N N: PTC thermistor quantity α: The rate of changing PTC thermistor resistance (α = resistance at over temperature operation) resistance at normal operation Set α to be at least (4 + N/2) × β or more, as guideline. β: VDET margin coefficient, set β to be N + 10 as guideline. Note: Design for PTC thermistor resistance variation and margins. If in a condition that multiple PTC thermistors are to be overheated at the same time, the combined resistance after overheating should be considered to set the system, to avoid false positive of the IC on the temperature below detecting temperature. Ex.) Reference PTC thermistor resistance using several (N) pcs. PTC thermistor resistance (25 °C) PTCO output current Product name (Typ.) N = 10, α = 300, β = 20 N = 10, α = 180, β = 20 (when α is increased) TCTH01xxE 1 μA 4.7 kΩ to 9.4 kΩ 2.8 kΩ to 9.4 kΩ TCTH02xxE 10 μA 470 Ω to 940 Ω 280 Ω to 940 Ω © 2023 9 2023-04-25 Toshiba Electronic Devices & Storage Corporation Rev. 2.0