LPC Microcontrollers中的主题 Re: LPC5516 ADC INPUT

LPC5516 ADC INPUT

liuweiqiang — Mon, 25 Jan 2021 06:53:45 GMT

How many volts can the internal clamping diode of the LPC5516 clamp to? If the ADC input pin voltage is -0.4V, will it affect other MCU pins?

I found the following pictures from the Internet. Is the GPIO architecture of LPC5516 the same? I read that the LPC5516 manual states that the minimum analog input voltage is -0.3V. Will there be any impact if it exceeds it?

Re: LPC5516 ADC INPUT

xiangjun_rong — Mon, 25 Jan 2021 09:00:29 GMT

Hi, WeiQian,

Unfortunately, we do not provide the analog channel internal architecture for the LPC55xx family.

Regarding the analog channel voltage range for LPC55xx family, pls refer to the VIA specs in data sheet of LPC551x.

The limiting analog ADC voltage is from -0.3V to 3.96V, the normal analog ADC voltage is from 0V to VDDA.

If your ADC analog voltage is out of the range from -0.3 to 3.96V, external diodes are required to protect ADC.

Hope it can help you

XiangJun Rong

I copy the notes here from the Data sheet.

[6] An ADC input voltage above 3.6 V can be applied for a short time without leading to immediate, unrecoverable failure. Accumulated
exposure to elevated voltages at 4.6 V must be less than 106 s total over the lifetime of the device. Applying an elevated voltage to the
ADC inputs for a long time affects the reliability of the device and reduces its lifetime.
[7] It is recommended to connect an overvoltage protection diode between the analog input pin and the voltage supply pin.

Re: LPC5516 ADC INPUT

frank_m — Tue, 26 Jan 2021 15:19:23 GMT

Extrapolating from other vendors/MCUs, about 0.6V.

However, not only does exceeding the max ratings reduce the lifetime, transverse currents through the clamping diodes will affect other ADC inputs, and most probably also other peripheral units.

I would suggest to avoid overvoltages, using proper external protection.