MCF8316AEVM: MCF8316A

Chuck Moon

Part Number: MCF8316AEVM
Other Parts Discussed in Thread: MCF8316A

I removed R9 (22 ohm) from the component side and populated L1 on the backside with a 47 uH inductor (with 2.5 ohms series resistance). What is the recommended nominal value of series resistance for best operation?

Powering the EVM by connecting between VBAT and PGND, with Vm=12.0, the measured supply current was reduced from 35 ma (R9 populated) to 24 ma (L1 populated). This includes about 3ma when D1 and D4 are lit. Do these values seem reasonable (datasheet shows lower values)?

Using the GUI, by selecting BUCK power sequencing is disabled (BUCK_PS_SEQ_DIS), I was able to set the BUCK output (FB_BK) to 3.3, 4.0, 5.0, or 5.7 volts. It looks like the Datasheet functional block diagram below, shows FB_BK is the input voltage to DVDD LDO which regulates the power for the microcontroller?

over 1 year ago

0 Vishnu Balaraj over 1 year ago

TI__Mastermind 24405 points

Chuck,

Please populate the inductor only. We don't need a series resistor.

Yes, the current consumption seems reasonable.

Unfortunately, we cannot share the internal power architecture of the IC as this is considered proprietary information.

Regards,

Vishnu

0 Chuck Moon over 1 year ago in reply to Vishnu Balaraj

Prodigy 100 points

I tried something a little unconventional that gave me some additional insight.

I removed R9 (22 ohm) and connected a 3.3v power supply to VBK (BUCK is open loop).

After powering up the system and connecting via the GUI, I restored all the parameters to default and set the BUCK_SEL via the GUI to 3.3v. Everything seems to work as if I had the BUCK connected. Is there a way to turn off the BUCK switching and reduce power?

The current from the 3.3v supply was 16 ma with the motor speed at zero. At any other motor speed or load, the current was 17 ma.

The current from Vm was reduced by 9-10ma at a speed of 3000 RPM and loads from 10-75%.

I tried Discontinous Space Vector Modulation. No reduction in power.

0 Vishnu Balaraj over 1 year ago in reply to Chuck Moon

TI__Mastermind 24405 points

Chuck,

I'll get back to you on Tuesday (5/31).

Regards,

Vishnu

0 Chuck Moon over 1 year ago in reply to Vishnu Balaraj

Prodigy 100 points

If I don't populate L1, L2, or R9 and supply 3.3v to VBK, is there a way to completely disable the switching of the BUCK (and save power)?

0 Vishnu Balaraj over 1 year ago in reply to Chuck Moon

TI__Mastermind 24405 points

Chuck,

Unfortunately, it is not possible to disable Buck in MCF8316A.

Regards,

Vishnu

0 Vishnu Balaraj over 1 year ago in reply to Chuck Moon

TI__Mastermind 24405 points

Chuck,

To minimize current consumption from VM, you can remove the buck inductor/resistor, configure BUCK_SEL to 3.3V, apply 3.3V at FB_BK and enable power sequencing. This will bye-pass the internal VBK and give lowest VM current.

Regards,

Vishnu

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MCF8316AEVM: MCF8316A