TMS320F28335: TMS320F28335 FALSE PULSE ISSUE

Ning Li

Part Number: TMS320F28335
Other Parts Discussed in Thread: C2000WARE, TMDSCNCD28335

Dears,

The customer uses a separate power supply when using 28335

If the 3.3V transistor in the level shift buffer of the I/O PIN is powered on before the 1.9V transistor, it may cause the output buffer to open, causing a false pulse at the moment of power-on.PLs help to check it?

Pls kindly find attach file for the wave form.

CH1:IGBT Driver Wave form
CH2:1.9V Wave form
CH3:PWM Wave form
CH4:3.3V Wave form
Highlight red is the false pulse wave form
Thanks

over 2 years ago

0 Hareesh Janakiraman over 2 years ago

TI__Guru* 95315 points

Ning,

I presume channel 2 (light blue) is 1.9v. From the waveform, it is evident that 3.3v leads 1.9v. This is the opposite of what the datasheet suggests and hence you see the glitch.

0 Ning Li over 2 years ago in reply to Hareesh Janakiraman

Intellectual 750 points

Hareesh,

Yes,you are right.My customer find the reason,they want to know if they don't use the PMIC that have any choice to avoid the PWM out when power on.

Thanks

0 Hareesh Janakiraman over 2 years ago in reply to Ning Li

TI__Guru* 95315 points

Ning,

It is not so much about using a PMIC. It is about following the sequencing mentioned in the datasheet. If that is not followed, it is difficult to avoid the glitch.

0 Ning Li over 2 years ago in reply to Hareesh Janakiraman

Intellectual 750 points

Hareesh,

Noted,so how any idea we can provide to customer so that they can avoid the glitch?Such as Reference design of power supply for 28335？

Thanks

0 Hareesh Janakiraman over 2 years ago in reply to Ning Li

TI__Guru* 95315 points

Ning,

28335 was before the days of Launchpads, but you can take a look at the Controlcard design at C:\ti\c2000\C2000Ware_4_03_00_00\boards\controlCARDs\TMDSCNCD28335\F28335controlCARD_HWDevPkg_ZJZ [R2.2]. The step-down converter used in the Contrlcard allows for precise sequencing.

0 Ning Li over 2 years ago in reply to Hareesh Janakiraman

Intellectual 750 points

Hareesh,

Noted,With many thanks.

Thanks

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TMS320F28335: TMS320F28335 FALSE PULSE ISSUE