How to practically use a Silicon Bandgap Temperature Sensor (CMOS-based)?  - Page 1
Forum section: electronics / beginners

author: mike buba
author_rank: Contributor
timestamp: September 01, 2025, 08:07:08 am
content: Hi all,While looking through some TI designs (e.g.,https://www.ti.com/tool/TIDA-01606) I found out they are using the TMP235A2DBZRhttps://www.ti.com/product/TMP235/part-details/TMP235A2DBZRand ISOTMP35BEDFQRQ1https://www.ti.com/product/ISOTMP35-Q1/part-details/ISOTMP35BEDFQRQ1. I read they are a Silicon Bandgap Temperature Sensors (CMOS-based) and are different from NTCs and RTDs, which I have used in the past.How would I practically use a Silicon Bandgap Temperature Sensors in an application? Let's say I need to measure inductor winding temperature or MOSFET heatsink temperature. Using NTC/RTC, I would route the sensor wire to the desired location. Do I need to route the wire to Tsense (for ISOTMP35BEDFQRQ1) or Vout (for TMP235A2DBZR)? The heatsink and inductor are further away from the PCB. Is this wire terminated?Kind regars, MBEdit.In the datasheet, the typical application is given as:Does it mean the IC device has to be near the heat source?... So basically, I can use it for ambient or enclosure temperature, but if I want to measure various points on the heat sinks or inductor windings, I need to use RTD or a thermocouple. Is this correct?

author: voltsandjolts
author_rank: Unknown
timestamp: September 01, 2025, 09:47:45 am
content: Erm, the sensor is embedded in those chips. The chip itself needs to be thermally coupled to the part you want to measure the temperature of.

author: mike buba
author_rank: Contributor
timestamp: September 01, 2025, 01:25:06 pm
content: Quote from: voltsandjolts on September 01, 2025, 09:47:45 amSo I assume I am better off using NTC or RTD if I want to measure something further away from the PCB.I can use a silicon bandgap temperature sensor to measure, e.g., ambient temp on the PCB.

author: voltsandjolts
author_rank: Unknown
timestamp: September 01, 2025, 03:08:56 pm
content: Yes, that's correct.The ISOTEMP35 is quite neat, offers good thermal coupling to, say, a SMD power fet on the high side of a h-bridge, with electrical isolation.For RTD and NTC there is a myriad of adc's available, then do the temperature calculation in an mcu...assuming you will have an mcu.

author: Terry Bites
author_rank: Super Contributor
timestamp: September 04, 2025, 12:14:44 pm
content: The Tsense is mechanically bonded to the thing you want to sense. Its not an electrical connection you can run a wire from(?)There are many low cost sensors and mostly they are in plastic packages and inherently isolated, well, up to a point. eg LM335 or MCP9700You can wrap them in a bit of Kapton tape for more isolation or mount them on a flex pcb daughter boards to suit your needs.(Kapton is not a bad conductor of heat)One great way to get up close and personal with your innards is to use a diodes or transistors as incredibly cheap probes.This method is used in micros, fpga's etc to monitor the core temperature.Microchip is your man here.www.microchip.com/en-us/products/sensors-and-motor-drive/temperature-sensors/digital-temperature-sensorsThe EMC1438 datasheet has made my chair quite damp.You can also get a mini IR camera, check out the AMG8833.

author: TimFox
author_rank: Super Contributor
timestamp: September 04, 2025, 02:22:22 pm
content: Basic point: a thermometer measures its own temperature. Therefore, it must be in thermal equilibrium with the object in question to get a usable result.(This does not apply to remote infrared sensing, but to old-style liquid and modern solid-state thermometers.)