TPS53679: Compensation parameters

Hi,

If you can provide an email id, I can provide the configuration file. I have attached it here though.

Regards,

Rasif0v8_voltage_droop_setting_updated.zip

TPS53679_1.pdf

I have uploaded the schematics here. Please see.

Hi Rasif, 

Just a brief overview on the compensation parameters. 

Lowering ACLL will help with a faster transient response and less phase margin, but lowering it too much may lead to loop instability. Increasing it will have the opposite effect. 

With respect to AC Gain, lowering it helps with increased transient stability but at the cost of transient speed. Increasing it accelerates transient response. 

Integration time constant helps with settle time during transient response. Decreasing it will give you a faster settle time. 

Ramp voltage helps with jitter and ripple performance. Lowering it will lower your transient response but will help with jitter and ripple. 

Enabling USR1 and USR2 are for undershoot reduction mechanisms. USR1/2 are just thresholds will help add phases to reduce undershoot during load insertion. 

Regards, 

Dhanya Prem 

Hi,

Can you please see the configuration file and suggest the changes for this requirement?

And does Vout Transition Rate, which I understand is slew rate have any effect on this issue I have mentioned?

Regards,

Rasif

Hi Rasif,

Can you elaborate your issue. What is meant by glitches in output and can you attach the supporting waveforms.

Best Regards,

Chanakya.

Hi Chanakya,

I am generating 0.8V. It is going down after 1 minute.

Then I increased the voltage to 0.81V and then its stable. But again as load current increases from 10A to 30A, the voltage was going down because we have a power monitor device where we set the enable to go off if the voltage goes below 0.776V.

Now I put a glitch filter for 4 milli seconds in the power monitor device. And then the voltage is not going down. So I suppose the issue is with the transient response parameters.

I have shared the configuration file and schematics above.

Regards,

Rasif

Hi, 

The CSD95490 devices are placed one below the other in the phase order of 1,3,2,4. And the TPS53679 device is at the top.

Regards,

Rasif

Hi Rasif,

We are working on this will get back to you in a day.

Best Regards,

Chanakya.

Hi,

Thank you.

Regards,

Rasif

HI Rasif,

Vout transition rate comes into picture during Vout command changes. From your config file I see that  ACLL value is too high compared to Vout_Droop. Try these values

ACLL = 0.3mohm

INT_Time = 6us

Can you capture the Vout waveform during the load transient. It will help in determining the compensation parameter values.

Best Regards,

Chanakya.

Hi Chanakya,

The ACLL minimum value possible is 0.5mohm in the tool. Should I try with this? 

And my acceptable drop from 0.8V allowed is +/- 24mV. Should I increase Vdroop?

And right now 0.8V is stable for sometime only if I increase Vout to 0.81V. And only then I can go to the stage of increasing load current. Do you want the waveform with Vout set to 0.81V? 

Regards,

Rasif

Hi Rasif,

As your spec is 0.8 +/- 24mV keep Vout=0.8V and Vout_Droop= 0mohm. Set the parameters as shown in below image

Please send the Vout waveform during load transients after making these changes.

Best Regards,

Chanakya.

Hi,

I have attached the image of output 0.8V here. When I disable the UVF response for turn off the voltage is stable at 0.799V.

Or even when I put a glitch filter of 4 milli seconds for UVF also, it is stable.

But when the UVF response for shutdown is enabled, the voltage is getting turned off.

Regards,

Rasif

Hi Rasif,

Increase ACLL to 1mohm and INT_Time to 4us. Try to capture Iout along with Vout. Capture waveform with Offset of 0.75 for Vout and 10mV/div scale, so that we can get better understanding on what is happening during the transient portion.

Best regards,

Chanakya.

Hi Chanakya,

I have attached the Vout waveforms with 0.75V offset and also 0.8V offset. The load current was around 8-9A for this observation.

The compensation parameters used for this observation and the Vout parameters are also attached.

The voltage is still getting turned off due to the transients going below 0.774V.

Regards,

Rasif

Hi Chanakya,

I have uploaded another waveform capture with time division changed at offset of 0.75V.

Regards,

Rasif

Hi Rasif,

Decrease AC gain value to 1 so that overshoot will reduce and might help the Vout waveform.

Best Regards,

Chanakya.

Hi Chanakya,

I reduced the AC gain value to 1 and it was not stable. Still the UV fault used to come.

Then I reduced the gain to 0.5 and I found it stable for a longer period than it was, for AC gain value of 1. 

Is there any other parameter I can try to change? 

Regards,

Rasif

Hi,

Even at AC gain value of 0.5, even though it was stable for a longer period, the UV fault is coming.

What are the other parameters, we can try to change?

Regards,

Rasif

Hi Rasif,

Is the Vout waveform not stable during constant load?

If it is not stable during the transients only, then try decreasing INT_gain to 1 and increasing ACLL to 1.125.

Best Regards,

Chanakya.

Hi Chanakya,

No, the Vout waveform is not stable during constant load that varies between 8-9A.

Regards,

Rasif

Hi,

Does this have anything to do with the Ramp voltage?

Regards,

Rasif

Hi Rasif,

As the Vout is not stable even during constant load, it seems that there is frequency jitter. The possible options to solve this is increasing ramp voltage and increasing ACLL value. You can try these.

Best Regards,

Chanakya.