TPS2121: tps2121 output drop??

Hi ,

Please try increasing output cap.

You can also operate device in fast- switchover mode to have less drop.

Regards 

Kunal Goel

HI.

CP2, PR1 => HIGH (divider with 10K pull-up/10K pull-down): Same as FAST SWITCH MODE.

& VOUT 100uF ADD.

The TPS2121 circuit uses an EK board.

Same as the TPS2121 EK board.

How can I reduce the DROP?

For reference, the TPS2113 does not have the above problem.

Regards.

KWON.

Hi Kwon,

I will get back before tomorrow EOD.

Regards

Kunal Goel

Hi Kwon,

Please keep resistor divider as below and then try experiment. 

1. 10K top and 10K bottom on PR1.

2. 10K top and 20K bottom on CP2

Regards

Kunal Goel

Thank you for your reply.

I tested it on the tps21221 ek board.

When 5V is removed, it drops to 3V momentarily and then rises to 3.7V.

The result is the same even when all caps are on.

Is there a way to output 3.7V without any drop?

Regards.

KWON.

Hi Kwon,

1. VIN1 is 5V?

2. VIN2 is 4.2V?

3. What resistor divider values you chose for PR1 and CP2?

Regards

Kunal Goel

Hi Kuna,

The resistance values are the same as in the answer above.

The results of 1 & 2 below are the same.

1. VIN1=4.2V, VIN2=5V 

 1) 10K top and 10K bottom on PR1.

 2)10K top and 20K bottom on CP2

2. VIN1=5V, VIN2=4.2V 

 1) 10K top and 20K bottom on PR1.

 2)10K top and 10K bottom on CP2

Regards.

KWON.

Ok. Let me think more on this. I will get back asap.

Hi Kwon,

1. Is the result same without 800mA load?

2. Please share a waveform showing VIN1,VIN2,VOUT,PR1,CP2,SS .

It will drop to 3V by logic because CP2<PR1 will happen when VIN2 is 3V and then device will switch from channel 2 to channel 1. 

What is the maximum drop you can afford?

Regards

Kunal Goel