TPS7A4201: Output Voltage drop when a Phone (DECT) is near

Update: Load is 20mA. The Input voltage Looks like Output voltage, only the Drops are much smaller.

Please see additional measurment

Green- Output

yellow- Input

Hi Manuel,

Since this problem occurs when you put a DECT phone in close proximity, it is likely the LDO is susceptible to EMI from the DECT phone. This part has ground current of 25 uA, which is very low. This tells me the part has high impedance nodes, which will make the LDO more susceptible to EMI.

Can you confirm the input voltage? It looks like 18.5V, not 13V.
Can you provide a plot of the input voltage droops?

Best,

Many thanks for your Feedback.

Vin is in this case 16V, The Input does not Show a drop. They checked this again.

They also tested the TPS79801 with the same result.

Any other idea?

Do you have another pin to pin alternative that is more robust?

best regards

Hi Manuel,

You're welcome. Both the TPS7A4201 and TPS79801 have low ground current at no load (25-30 uA), indicating bias currents are low and there are likely high impedance nodes internal to the IC, that may make them susceptible to EMI. For this application, all of the alternate LDOs have low ground current and low internal bias currents, so you may have to test each until you find one that works.

The following LDOs are package compatible that you could try:
TPS7A4001 www.ti.com/.../tps7a4001

TPS7A4101 www.ti.com/.../tps7a4101

TPS7A49 www.ti.com/.../tps7a49
DGN package. Note: Vref = 1.188V, differing from TPS7A4201 Vref = 1.173V. Also, TPS7A49 has a NR/SS pin 6. If this pin is left floating, startup time will be 50 usec (approx) and output noise from the reference will increase the output voltage noise.

TPS7A16 www.ti.com/.../tps7a16
DGN package. Note: Vref = 1.193V, differing from TPS7A4201 Vref. Delay pin and PG pin can be left floating.

Best,