BOOSTXL-DRV8301: BoostXL-DRV8301 Motor's Current Sense Circuitry

Zeid

Part Number: BOOSTXL-DRV8301

Hello,

the opamp outputs for the current sense in the BoostXL-DRV8301 (IA_FB, IB_FB, IC_FB) are all connected to 56 Ohm resistors in series, followed by 2200 pF caps in parallel before reaching ADC pins on the LAUNCHXL-F28069M.

Is that a low pass filter? Or some kind of impedance matching for the ADC input? Or what exacty?

Also could you please explain about the usage of the "Net-Ties" (example J7-J10) in the differential pair paths?

Thanks.

over 6 years ago

0 Adam Sidelsky over 6 years ago

TI__Guru 65320 points

Zeid,

The resistor/cap is simply a filter.

The net tie is there because Altium won't let us connect two nodes of different names to the same electrical node. It's purely symbolic so we can have differentiated names for different areas of the circuit.

Regards,

-Adam

0 Zeid over 6 years ago in reply to Adam Sidelsky

Prodigy 105 points

Thanks Adam for the reply.

It got clear with the net-tie.

On the filter: while the filter's pole for the voltage sense feedback is at about 365 Hz, the RC filter's pole for the current sense after the opamp is at about 1.3 MHz.

Too high? Any explanation for that separation?

0 Adam Sidelsky over 6 years ago in reply to Zeid

TI__Guru 65320 points

Let me check and get back to you.

0 Adam Sidelsky over 6 years ago in reply to Adam Sidelsky

TI__Guru 65320 points

Zeid,

The voltage feedback filter network is specific to FOC and is discussed at length in the following:

www.ti.com/.../spruhj1g.pdf section 5.2.3

The current feedback network was just a noise suppression effort, nothing special went into the selection of those.

Regards,

-Adam

0 Zeid over 6 years ago in reply to Adam Sidelsky

Prodigy 105 points

Thanks Adam, I would try to lower the filter's pole for the current feedback network.

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BOOSTXL-DRV8301: BoostXL-DRV8301 Motor's Current Sense Circuitry