LM5164-Q1: What will happen if Vin goes below or equal to the target Vout?

PYTsai

Genius 11635 points

Part Number: LM5164-Q1
Other Parts Discussed in Thread: LM5164

What will happen if Vin goes below or equal to the target Vout?

for example: below is our design. if Vin goes down to 15V or lower than 15V, what will LM5164 behave ?

over 5 years ago

0 Gavin Wang (Zejing) over 5 years ago

TI__Expert 3480 points

Hi ,

A controllable on-time as low as 50 ns permits high step-down ratios and a minimum forced off-time of 50 ns provides extremely high duty cycles allowing VIN to drop close to VOUT before frequency foldback occurs.

Tonmax=10000ns.

Dmax= Tonmax/(Tonmax+Toffmin)

When VOUT will keep regulated until VIN is equal to VOUT/Dmax.

Then VOUT will decrease with VIN.

Gavin

0 LIN YU MING over 5 years ago in reply to Gavin Wang (Zejing)

Prodigy 220 points

Hi Gavin:

How can we get the Toffmin?

YUMING

0 Gavin Wang (Zejing) over 5 years ago in reply to LIN YU MING

TI__Expert 3480 points

Hi YUMING,

Toffmin=50ns which is in datasheet.

Gavin

0 LIN YU MING over 5 years ago in reply to Gavin Wang (Zejing)

Prodigy 220 points

Hi Gavin:

Thank you.

YUMING

0 LIN YU MING over 5 years ago in reply to LIN YU MING

Prodigy 220 points

Hi Gavin:

What will happen if Vin goes below to the target Vout? Could we design in that situation?

YUMING

0 Gavin Wang (Zejing) over 5 years ago in reply to LIN YU MING

TI__Expert 3480 points

Hi YUMING,

Yes, you can.

Tonmax=10000ns.

Dmax= Tonmax/(Tonmax+Toffmin)

If Vin goes below to the target Vout, Vout=Vin*Dmax.

Gavin

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LM5164-Q1: What will happen if Vin goes below or equal to the target Vout?