Hi all,

I'm using LDO LM39300 in my circuit to get constant 4.2v for my gsm module,my supply for that LDO is from 5V flyback converter.
Once because of some issue smps was giving 28v ,after this instant, both LDO and GSM module both are getting heat.

But both working fine by producing heat.
Please provide some solution.

 

Hello,

Do you have the in and output capacitors as given in the datasheet?

---
Output Capacitor
The LM39300/1/2 requires an output capacitor to maintain stability and improve transient response. Proper capacitor
selection is important to ensure proper operation. The LM39300/1/2 output capacitor selection is dependent upon
the ESR (equivalent series resistance) of the output capacitor to maintain stability. When the output capacitor is 47F
or greater, the output capacitor should have less than 1 of ESR. This will improve transient response as well as
promote stability. Ultralow ESR capacitors, such as ceramic chip capacitors may promote instability. These very low
ESR levels may cause an oscillation and/or underdamped tran-sient response. A low-ESR solid tantalum capacitor
works extremely well and provides good transient response and stability over temperature. Aluminum electrolytics can
also be used, as long as the ESR of the capacitor is < 1.The value of the output capacitor can be increased without
limit. Higher capacitance values help to improve transient response and ripple rejection and reduce output noise.
Input Capacitor
An input capacitor of 1F or greater is recommended when the device is more than 4 inches away from the bulk ac
supply capacitance, or when the supply is a battery. Small, surface-mount, ceramic chip capacitors can be used for
the bypass-ing. Larger values will help to improve ripple rejection by bypassing the input to the regulator, further
improving the integrity of the output voltage.Transient Response and 3.3V.
---

Bertus

 

I'm using LDO LM39300 in my circuit to get constant 4.2v for my gsm module,my supply for that LDO is from 5V flyback converter.
Once because of some issue smps was giving 28v ,after this instant, both LDO and GSM module both are getting heat.

The LM39300 data sheet states very clearly, in the Absolute Maximum Ratings section, that the maximum supply voltage of the part is 20 VDC and that exceeding any of the absolute maximum ratings may damage the device. By applying 28 VDC you very likely destroyed the part, which is why both it and the GSM module are getting hot.

Replace the LM39300 with a new chip.

 

Thanks for all your replies as you people said that When i change LDO ,LDO is working fine but still GSM module is getting heat .
In gsm module both Vcc and ground is getting short.
Is this short indicates that GSM module gone bad???

 

Is this short indicates that GSM module gone bad???

That seems correct. You feed it the 4.2 volts it is designed for and it overheats, therefore it is broken.

 

Hello,

Do you have the in and output capacitors as given in the datasheet?

Note that where it says 47F and 1F it really means 47uF and 1uF

 

Thanks for all your feedbacks ,

I have contacted simcom FAE he as told that ,if you get short between vcc and gnd of gsm module it means it has failed due to over voltage.