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# TPS7A25: TPS7A25

Part Number: TPS7A25

Hi

I want to use TPS7A25 for one of my design.

My application requirement is for adjustable voltage output.( Vout = 4V).

I am refering datasheet : SBVS372A –DECEMBER 2018–REVISED MARCH 2019

My question is :

While refering Section 6.5 Electrical Characteristics, which mentions :

specified at TJ = –40°C to + 125°C, VIN = VOUT(nom) + 0.5 V or VIN = 2.4 V (whichever is greater), FB tied to OUT

>> As per my understanding [ VIN = VOUT(nom) + 0.5 V ] this will be applicable to only FIXED OUTPUT type design.

am I correct?

>> As per the formula for adjustable Vout,

VOUT = VFB × (1 + R1 / R2)

In this formula Vout is not at all dependent on Vin.

So do I have to bother about [ VIN = VOUT(nom) + 0.5 V ] condition.

>> For Vout = 4V using adjustable output type configuration, is it possible to provide any VIN within specified VIN range i.e. 2.4V (min) to 18V (max)?

• Hi ,

The general test condition which you mention is to ensure that the TPS7A25 is regulating the output during testing.  Please note that our maximum dropout specification for TPS7A25 at the full 300 mA rated load is 340 mV.  As such, in order to achieve a regulated output at 300 mA, you would require a minimum input voltage of your 340 mV above your output voltage.  Therefore for a 4 V output, your minimum Vin for a regulated output is 4.34 V.

Very Respectfully,

Ryan

• In reply to Ryan Eslinger:

Hi Ryan,

Thank you for the reply. I got clarified my query on this topic.

I have one more question regarding Cout.

As per Recommended Operating Conditions, Cout can be from 1uF to 100uF with 2.2uF typ. value.

How to decide the exact capacitance required?

I have idea about Cout capacitance requirement varies with load transients and effect of bias voltage on capacitance.

Thanks.