DRV2605L: Output voltage is lower than expected

It's come to my attention that the equations for V(erm_clamp) and V(lra_clamp) are swapped in the datasheet, e2e.ti.com/.../655886

so my output voltage should only be dependent on OD_CLAMP. My question remains mostly the same

Hi,

I missed that previous E2E post. I will make the changes ASAP to the datasheet. If you just plug in 0xFF for OD_Clamp, do you get max output strength? What hex valule are you using now?
There will be a little headroom for the amplifier, but you should see ~2.8-3V on the output.

I've tried 0x9B and 0xFF, both produce the same result. Here is all of my initialization code, if that helps

//Exit standby Set to PWM input mode
i2c_data[0] = 0x03;
i2c1_comm(MODE_REG, I2C_WRITE, 1);

//Set ERM_OPEN_LOOP to open loop and N_PWN_ANALOG to PWM
i2c_data[0] = 0x28;
i2c1_comm(CONTROL3_REG, I2C_WRITE, 1);

//Set overdrive voltage
i2c_data[0] = 0xFF;
i2c1_comm(OVERDRIVECLAMP_REG, I2C_WRITE, 1);

Now I'm thinking the issue may be electrical. On my system the DRV2605L is being fed from a .5A rated voltage regulator, which should be plenty. But I added a 100uF cap for good measure and my voltage increased to 1.9V

To add some more data points, I tried using an Arduino 2560 Mega connected to my PC through a high power port on a USB hub. Running the same code as above with the DRV2605L connected to the Arduinos 3.3V pin I get 2.2V output. With it connected to the 5V pin I get 3.2V.

Are there any specs about the required headroom for this device? It appears from my experiments so far that the maximum output voltage is always a fair amount lower than VDD