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TIDA-01574: Replace 820uF capacitors with smaller electrolytic ones?

Part Number: TIDA-01574

Hello Guys,

According to our customer, the 820uF are quite large for a thermostat, e.g. 16mmx20mm .  He have less than half that volume. Is there any repercussions if he replaced it with smaller electrolytic ones?

Also, his design draws current from a battery every cycle.  He wants to run off of the HVAC power all the time and keep a battery charged.  Is the reference design still suitable for that?  He plan to keep my average current consumption less than 25mA from the HVAC.

In addition, he wants to know if there is a need for the load switches.  Are they necessary?

Thanks to confirm!


  • Hi Art,

    It depends on the load power of thermostat control unit when HVAC load is off. If the load power is higher than the combination of power through the eFuse and holdup capacitors, the load will be powered by the battery through the priority power MUX stage and boost converter. 

    Please refer 3.2.1 Power Stealing Operation and figure 9 in TIDA-01574

    How much power the control unit draws when HVAC load is off ?

    Best Regards, Rakesh