TPS7A05: overshoot on start up waveform

Given Ding

Part Number: TPS7A05
Other Parts Discussed in Thread: TPS7A03,

Hi Team,

during test on TPS7A0528, we found below

Green= Vin, Yellow= Vout. Vin and EN pin are connected together.

1. there is a stage before Vout ramping up to Vset @ no load ( red circle). what's the reason for this? I see our datasheet, there is also such stage.

2. There is over shoot on Vout when Vout is ramping up to Vset @ 20mA, 40mA.

Iout=40mA

Iout= 20mA

Please kindly help check the reason. Thanks.

BRs

Given

over 3 years ago

0 John Schneider over 3 years ago

TI__Genius 12511 points

Hi Given,

1) Yes, This initial period does not have official naming convention across the industry, but is expected for the device. This delay is present as the device powers on its internals before driving the pass device signaling the start of full operation.

2) This is not in the datasheet, but is a known issue with the part, this is one of the primary concerns with the 7A05 device. If this overshoot is unacceptable for your design, our marketing team members would recommend considering the TPS7A03 as it is very similar device, with better performance and does not have the same concerns that the TPS7A05 brings.

Regards,

John

0 Given Ding over 3 years ago in reply to John Schneider

TI__Genius 10305 points

Hi John,

Thanks.

regarding #2, is there any method to decrease the overshoot? Or can we estimate the max overshoot for customer to do evaluation on the effect to their system? Thanks.

BRs

Given

0 John Schneider over 3 years ago in reply to Given Ding

TI__Genius 12511 points

Hi Given,

In order to reduce overshoot you can:

reduce output capacitance

Sequence En pin so it only goes high once Vin has sufficient headroom

Additionally section 8.1.5.1 on the datasheet discusses what is happening on the device that is causing the overshoot to occur.

Linked here is an app note detailing more robustly the solutions and explanations of how to reduce overshoot on LDO's

Regards,

John

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TPS7A05: overshoot on start up waveform