Maximum Clamping Current I/O

[HwDesigner]

Dear reader

I have the following question and associated background:

What is the latch-up/damage free maximum positive and negative input clamping current for the IMXRT digital and analog inputs?

For a design that we are making, we would like to interface analog and digital inputs to the IMXRT1064 GPIO & ADCs. As the voltages applied to the inputs are originating off-board, we need to protect the MCU from overvoltage conditions outside of the normal digital/analog operating range.

The easiest way to realize this is to add series impedance to the line and add clamping diodes to the rail, however preventing any current from going into the parasitic ESD diodes of the MCU pin is often a struggle.

With many controllers, a maximum input injection current (https://www.st.com/resource/en/datasheet/stm32f756bg.pdf) or clamping current (https://ww1.microchip.com/downloads/en/DeviceDoc/PIC18(L)F2X-4XK22-Data-Sheet-40001412H.pdf) is specified in the Absolute Maximum Ratings. With the NXP/Freescale IMX series I cannot find these specifications in the datasheets.

Many thanks in advance for your help!

[felix_cormier9]

This was a great question with no good reply... I'm also looking for the max input clamping current (IMXRT1024) to protect the MCU's clamping diodes during an ESD event. That's not the same as the max input voltage that was shared in the reply.

Without this in the datasheet, we designers are left to guess.

[HwDesigner]

I fully agree with your statement. Without this crucial piece of information in the datasheet I need to assume that only zero current is acceptable. This means that I need to buffer every single input, which complicates my designs and in the end makes the IMX solution less attractive board-space wise and pricing wise.

[vicentegomez]

Would be possible that you give me more information about your projects, such as the operating voltage range and etc.

[ThomasSC]

I have the same question according the maximum clamping current into I/Os.
On my custom board I want to connect 32V with a 33k Ohm series resistor to an input.
Is this permissible?

Kind regards

Thomas

[vicentegomez]

We get some information from RT1064 datasheet.

For ADC,

 

when external inputs connect to the IMX RT1064 ADCs pin, we need consider the internal impedance setting of the ADC and the input voltage should not exceed the Max limit value in the table.

For GPIO,

The add series impedance way should consider carefully and choose suitable parameters for system works normally, in addition, the level shifter may be used in the connection of different voltage.

[ThomasSC]

Could you give the maximum input-current ratings like in the K64 datasheet?