Hi Zack,
Is it possible for LTC4079 to have more wider temperature range from -35C to 80C? For most NTC thermistors from Vishay or TDK, about 0C ~ 40C range following below threshold.
In my application, I'd like to extend temperature range to -35C to 80C.
Regards,
Ma Dawei
Hello,
Yes, you can use a thermistor with a lower beta value for less sensitivity to temperature. This will effectively extend the NTC range based on the fixed threshold ratios that the LTC4079 uses. These ratios are given in the spec table to help assist you in choosing an alternate thermistor beta value:
Regards,
Zack
Hello,
Yes, you can use a thermistor with a lower beta value for less sensitivity to temperature. This will effectively extend the NTC range based on the fixed threshold ratios that the LTC4079 uses. These ratios are given in the spec table to help assist you in choosing an alternate thermistor beta value:
Regards,
Zack
Zack,
I calculated the Beta constant value needed following the threshold specified by spec of LTC4079, take 10K@25C NTC as an example. 1000K+ got. But TDK told me that they don't have NTC with 1000K+ products, all of their NTC products are with 3000K+ ~ 5000K.
So that's my point, although theoretically it can be used in extended temperature range, but maybe no NTC products available now, I'm still waiting for Vishay feedback. Most likely, LTC4079 is designed to support most of battery chargers working in 0C ~ 40C temperature range.
Regards,
Ma Dawei
Hi Ma,
You're right about that. I've double-checked your calculations.
You may be able to get the NTC profile you need by adding series/parallel resistors. We typically add them like this:
The parallel resistance will effectively give you a reduced beta value. To get a lower cold cutoff, you may need to add a series resistor as well.
Regards,
Zack
Zack,
I find it is hard to figure out Rp and Rs in your proposal, do you have quick method to get them?
For easier and quicker calculation of Rp and Rs, I change the resistor network like below and get one NTC from TDK can be used to meet my design goal.
Hope this to help other people, and thank you.
Regards,
Dawei Ma
