TPS61099: Down Mode operation when VIN ramps down

AXM

Part Number: TPS61099

Dear Team,

like described in the Datasheet SLVSD88K –JULY 2016–REVISED MAY 2018, Figure 20. When VIN ramps down from the Passtrough to Down mode, how is VOUT fixed to the nominal output Voltage (red-line) while VIN is lower than Vout without Boost?

thx

over 7 years ago

0 Jasper Li over 7 years ago

TI__Mastermind 46905 points

the device always boost when input voltage is lower than VOUT. it just operates at a special boost mode when the VIN is closed to VOUT.

0 AXM over 7 years ago in reply to Jasper Li

Prodigy 80 points

Thx for your answer,
in Datasheet chapter 8.3.8 the last sentence :
--> It stays in Down Mode until input voltage falls 100mV below the output voltage, returning to Boost operation.
What is happening in between this 100mV ?
If i understand you right, Down Mode is done with the PMOS as well as Boost operation within this 100mV Hysterese?
The Datasheet is not clear to me in this situation...

0 Jasper Li over 7 years ago in reply to AXM

TI__Mastermind 46905 points

please refer to this application note to understand down mode operation "www.ti.com/.../slva199.pdf". the device still switches at down mode, so the VOUT can be higher than VIN.

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TPS61099: Down Mode operation when VIN ramps down