DRV3946-Q1: Why SDO max output logic low voltage is 0.3V, not 0V?

Beida Song

Part Number: DRV3946-Q1

Hi Expert,

Customer test DRV3946 SDO output low voltage is 0.26V. SDO is push pull architecture. Could you help check if there is internal resistor and why SDO Low voltage is 0.3V, not 0V?

In order to express customer's question celarly, I draw simply circuit. Customer test R2 voltage to get the sink current. Also they probe SDO low logic voltage in pin. Based on calculation, they get the internal impedance is 127ohm. Thus, they wants to know if there is a real internal resistor in SDO. If not, why we design 0.3V as max SDO output low voltage.

3 months ago

0 Ibinu Alaudeen Nadeera 2 months ago

TI__Genius 15341 points

Hi Beida,

Thanks for the question. Here are my comments

In the actual system diagram R1 should connect directly to SDO pin and R2 should be connected from SDO to the MCU side. Let me know if that makes sense.

Coming back to the low voltage, i looked at the characterization data to see the actual numbers and looks much lower than 300mV. The histogram shows <30mV across lots, temperature etc.

Thanks,

Ibinu

0 Beida Song 2 months ago in reply to Ibinu Alaudeen Nadeera

TI__Intellectual 950 points

Hi Ibinu,

Yes, you are right. The R2 connect to MCU through level shifter. I know the real test data it lower than 300mV. Actually, customer can't understand why the low logic voltage is not 0V or 0.1V. They think there is a resistor like R1 exit in SDO's internal part. Could you help check that and find the cause of 0.3V exit from internal circuit aspect?

0 Ibinu Alaudeen Nadeera 2 months ago in reply to Beida Song

TI__Genius 15341 points

Hi Beida,

There will be some resistance on the low side FET which will cause this voltage. As i mentioned above the voltage is actually much lower than 300mV in actual silicon.

Thanks,

Ibinu

0 Beida Song 2 months ago in reply to Ibinu Alaudeen Nadeera

TI__Intellectual 950 points

Ibinu,

Thanks for clarify the voltage. Do you have the resistance value? Is it about 100Ω level?

0 Ibinu Alaudeen Nadeera 2 months ago in reply to Beida Song

TI__Genius 15341 points

HI Beida, From the data it looks to be around 60Ohms.

Thanks,

Ibinu

0 Beida Song 2 months ago in reply to Ibinu Alaudeen Nadeera

TI__Intellectual 950 points

Thanks, Ibinu.

Motor drivers

Motor drivers forum

DRV3946-Q1: Why SDO max output logic low voltage is 0.3V, not 0V?