Can nRF52 Differential ADC Measure voltage higher than VDD?

RE: Can nRF52 Differential ADC Measure voltage higher than VDD?

Howard — Tue, 11 Apr 2017 07:14:54 GMT

@Vala, and Jcormier, thank you very much for your information!

RE: Can nRF52 Differential ADC Measure voltage higher than VDD?

jcormier — Mon, 10 Apr 2017 13:53:36 GMT

Howard, Note the Laird devkit uses a current shunt IC. No idea if its power efficient but its a start. They don't actually hook it up to the BLE chip but you could.. cdn.lairdtech.com/.../BL652 Dev Kit User Guide.pdf (See 9.1 Current Consumption Measurement) INA216

RE: Can nRF52 Differential ADC Measure voltage higher than VDD?

Vala — Mon, 10 Apr 2017 11:34:54 GMT

Hi Howard,

You can measure the current using a resistor in the path of power supply and sensing the voltage difference between the two pins of the resistor. Also, I wouldn't personally go with placing the resistor at the ground side of the device. It would introduce grounding error in the system. You can either power the other device with 3V, if it is possible or use an external component like an op-amp to produce the difference and then read it by the ADC. I didn't find any specific number in the datasheet regarding the maximum allowable input of ADC pins. But I found (1) the allowable input for I/O doesn't let you do this, (2) the value of the ADC reference can either be internal or VDD, which in any case doesn't let you use the internal ADC for this purpose. Hope this helps.

RE: Can nRF52 Differential ADC Measure voltage higher than VDD?

Howard — Mon, 10 Apr 2017 06:40:37 GMT

Is that because of over-voltage? I can put the resistor to ground side. Whatever, Could you recommend one kind of C/V convert IC? Thanks a lot!

RE: Can nRF52 Differential ADC Measure voltage higher than VDD?

Songplus — Mon, 10 Apr 2017 06:28:48 GMT

U can't measure current using ADC Directly，U should use a IC to C/V convert