TPS61029-Q1: The Operation Mode.. Step-Down Conversion and Step-Up.

Sam-Mo Yeon

Prodigy 80 points

Part Number: TPS61029-Q1

I know that "TPS61029-Q1" have two operation mode, Down regulation and Step-Up regulation.

I designed that Vout is 3.3V, so, R3 = 1Mohm, R4 = 180Kohm.

Test condition by Vin

When Vin <= 2.8V, Vout is 3.28V.

When Vin >= 3V, Vout is 2.526V

I understand by page 12 in datasheet , When Vout be designed 3.3V and Vin is more than 2.8V(by Vfb 500mV), change to the down conversion mode.

but, I don't know that why Vout is 2.526V when down conversion mode.

please check.

over 7 years ago

0 Youhao Xi over 7 years ago

TI__Guru* 76965 points

The engineer supporting this part is currently on vacation. You may need to wait a couple of days to get the answer

0 Jasper Li over 7 years ago

TI__Mastermind 46905 points

the behavior you observed is not correct for TPS61029-Q1. could you share your schematic and layout? also share the waveform of VIN, SW, VOUT when the issue happens

0 Sam-Mo Yeon over 7 years ago in reply to Youhao Xi

Prodigy 80 points

The Vout be probed by multi-meter. and the below is the circuit for TPS61029-Q1.

0 Jasper Li over 7 years ago in reply to Sam-Mo Yeon

TI__Mastermind 46905 points

what is partnumber of the tantalum capacitor?
could you also share the waveform i mentioned and the layout?

0 Sam-Mo Yeon over 7 years ago in reply to Jasper Li

Prodigy 80 points

1. When Vin is 2.7V,

The wave of pin 6(Vbat) : DC 2.7V

The wave of Pin 9(SW): it's working with switching On/Off.

The wave of Pin2(Vout): it's good operation with Vout 3.3V

2. When Vin is 3.5V,

The wave of pin 6(Vbat) : DC 3.5V

The wave of Pin 9(SW): it's not switching

The wave of Pin2(Vout): it's Vout 2.5V

0 Jasper Li over 7 years ago in reply to Sam-Mo Yeon

TI__Mastermind 46905 points

is there any load in the output at VIN=3.5V, VOUT=2.5V

0 Sam-Mo Yeon over 7 years ago in reply to Jasper Li

Prodigy 80 points

Yes, it's same load at Vin=2.7V, Vout = 3.3V.
In 7 page of datasheet, I found the graphic Vi vs Max Out Current.
by the graphic, from the point of Vi=2.8V, Vo=3.3V, Max Current downing to 800mA. I think, the load is below to 800mA. but I guess to need check

0 Jasper Li over 7 years ago in reply to Sam-Mo Yeon

TI__Mastermind 46905 points

before the device finishing startup, the output current should be small. refer to this application note "www.ti.com/.../slva387.pdf"

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TPS61029-Q1: The Operation Mode.. Step-Down Conversion and Step-Up.