DRV8812: Decay pin Internal pull-up / pull-down circuit

Hi Ishiwata-san,

Thanks for your question.

Shuji Ishiwata said:

but the DRV8802 E2E forum lists both pull-up and pull-down resistors. Is this the same for the DRV8812?

The DECAY pin in the DRV8812 has three functions. See snippets from the datasheet. For DECAY 0 to 0.8 V SLOW decay, > 2 V FAST decay and around 1.4 V MIXED decay. When the pin is left floating, internal pull-up and pull-down would provide the voltage level for MIXED decay. I'd expect the values to be different compared to the DRV8802. Its ratio can be calculated by measuring the DECAY pin voltage when it is floating.  

Shuji Ishiwata said:

I understand from the E2E forum below that there is an internal 10kΩ pull-down resistor.
DRV8812: Internal pull-up / pull-down circuit 

Did you mean 100 kΩ? It applies to all logic level input pins. DECAY pin is a 3-level pin not a logic level input pin. Thank you.

Regards, Murugavel   

Hi Ishiwata-san,

Shuji Ishiwata said:

As you say, the Decay terminal can be configured.

The DRV8812 has the option for 3-decay modes. See below. Our recommendation is to either have the Decay pin LOW, HIGH or OPEN depending on the desired decay mode. For the DRV8812 internal Decay pin resistor values you can use the values referred in this E2E you highlighted. 

For the DRV8802 there are only two options for the Decay pin. See below.

The above are the recommended connections for the Decay pin. Thank you.

Regards, Murugavel