TPS7A91: Tendency of load transient response

Hi Kuramochi san,

The answer is minimal to no effect on load transient.

The LDO can be seen as a voltage controlled current source that supplies current to the load, so it must be able to hold its output voltage constant as the load current demand varies anywhere from zero up to full load, even if the change occurs in a relatively short time( fast di/dt). Now how well the LDO holds its output voltage constant during such load transient is defined as the LDO’s load transient response.

During load transient, Vout will change but how much it changes depends on the size and type of output capacitor, the (di/dt) change of the load and on the response speed of the LDO not on how large is the difference between Vin and Vout.

One thing worth mentioning is that during load transient, the LDO will try to compensate for the change (dipping) in Vout by pulling current from Vin which could cause the input source of the LDO to go into current limit and that could lead to Vin going below the LDO’s UVLO limit thus shutting down the LDO, so having a stable input source with ample current capability to an LDO is essential for good load transient and not how much large is the difference between Vin and Vout.

Hope this helps answering your customer's question!

BR,
Haidar

Hi Kuramochi-san,
I can see a small difference in undershoot of around 8mV and and around 10mV in overshoot but still think of it as minimal, such difference could be caused by the test setup.

BR,
Haidar