TPS61289: boost mode application

Tommy Tzeng

Genius 5290 points

Part Number: TPS61289
Other Parts Discussed in Thread: TPS55289, , TPS61287

Tool/software:

Hi Sir,

we would like to confirm a few question:

1. Input 20 V, output 21.5V, maximum current 7A, Boost mode, Does VFB use 0.7V or 0.8V?

2. How to calculate the output voltage of VHIGH in Boost mode?

3. PIN3_COMP, can not connect the external compensation circuit?

+1 Fergus He 6 months ago

Hi Tommy,

The device can be used as a pure boost device.

You can regard it as a normal boost device and set the MODE pin to be low.

The FB is regulated with 1V typically and please set the Rup/Rdown=20.5.

The device works in FPWM mode at 250k at all time.

And please connect the comp pin with Rcomp and Comp.

There are two points to be checked.

the device starts switching when Comp ramp to 0.6V and this may cause spike at start.

another is the minimum off time could be reached when Vin is very close to Vout, this also causes oscillation.

I will double check the two points and reply to you later.

Here are another device for your reference.

TPS55289, it is boost-buck converters.

Best Regards,

Fergus

0 Tommy Tzeng 6 months ago in reply to Fergus He

Genius 5290 points

Hi Fergus,

got it, thanks.

may we know this schematic is ok? thanks for your support and learn,

0 Fergus He 6 months ago in reply to Tommy Tzeng

Hi Tommy,

I think you are asking the same project like Chen.

Here is the summary:

1. the device can be used as pure boost.

2. the FB is regulated with 1V typically

3. Comp pin must connect with Rcomp and Ccomp

4. the minimum on time is enough for the transform.(it is tested and ok)

TPS61287 can be regarded as the pure boost version of TPS61289 and it will be RTMed this year.

Please tell me if you have more questions.

Best Regards,

Fergus