Weird sound from particle photon

I am using 3.7v lipo battery with particle photon. also added a 3.7v lipo charging circuit based on tp4056. the supply connections to the photon are parallel,from battery and charging circuit. sound occurs when the photon is working using the charging circuit supply alone(battery in disconnected condition).i am getting 4.2v in the vin terminal of photon.

That verbal description doesn’t really paint a clear picture of your setup.
A neat schema and some pictures do usually help a lot more.

Also what is a weird sound? humming, hissing, singing, high pitch, low pitch, constant, pulsed, …

How do you power the charger?
How clean is that voltage? (pulsed vs. filtered DC, ripple, …)

it is a humming sound. i am powering the charger from 5v 2amps supply.
there was a problem with the voltage, the tp4056 ic current is regulated using a programming resistor, where the circuit came with a 68k resistor, at that time the photon was not even turning on i guess it was because of the low current. after replacing the programing resistor with a 12k. it is working. but with the sound and it seems unstable with the voltage i think it is because of the low current .

Should be easy to remove photon and add a “dummy” load to determine if the sound is coming from the external power circuit ?

Based on the datasheet, the value of Rprog you chose is too low.

You should be choosing a value of 2K to 3K ohms at least to get a curret of 400-580ma. The photon needs at least 350ma when connecting to WiFi, though only for a short time. The charger is not designed to be used without a battery.

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sorry. the resistor i used is not 12k. it is 1.2k
according to data sheet 1.2k resistor should give current of about 1A.

@shafeekashraf44, are you test with or without a battery? As I indicated, this regulator is not designed to work without a battery. It will shut down when the charge current drops below 1/10th the programmed 1A current. Typically, the Photon takes less than 100ma when operating. The humming may be the Photon’s onboard switching regulator struggling with not enough current being supplied without the battery.

If you want to use a charger without a battery, you need a different charger. You need one with power path management which will switch to sourcing power from a USB (or other supply) source or from a battery, while charging the battery if it present.