[FAQ] AM625 / AM623 / AM620-Q1 / AM62L / AM62A / AM62P / AM62D-Q1 / AM64x / AM243x Design Recommendations / Custom board hardware design - Queries related to passive components values, tolerance, voltage rating

Hi Board designers, 

Refer below 

1. In the SK/EVM i see 49.9K resistor used. Can i use a  standard value instead

Ok to use a standard 47K resistor 

2. In the SK/EVM i see a number of resistors used with 1% tolerance for pullups and series resistors. Can i use standard tolerance resistors?

There are specific resistors that have 1% tolerance requirements. 

All other resistors used can be standard tolerance resistors.

3. Is there a recommendation on the capacitor voltage rating 

This is customer design and requirements dependent

Generic suggestion (derating) is to use capacitors with voltage rating > 2 time the worst-case voltage applied for non-polarized capacitors.

For polarized capacitors review relevant data sheet for derating. 

4. Sections that have 1% resistor recommendations

Refer below:

The Below excel provides additional details

List of 1% resistors used in AM62x, AM62Ax, AM62Px, AM625SIP, AM62Dx, AM243x AM64x_EVM_SKs_31122024.xlsx

5.. Is there a recommendation on the capacitor voltage rating

CAP_VDDSx, CAP_VDDS_CANUART, CAP_VDDS_MCU, CAP_VDDSHV_MMC1 have capacitor value recommendations.

Note: USB interface when configured as host has capacitor value requirements to be connected near to the connector.

Refer USB standards or SK schematics.

Regards,

Sreenivasa

Hi Board designers, 

Additional inputs regarding USB RCALIB resistor implementation:

The IP specification TI received from the USB PHY design team defined a 500 ohm +/-1% calibration resistor. A few weeks ago another customer reminded us 500 ohms is not a standard value for 1% resistors. They were having problems sourcing a 500 ohm +/-1%, so asked if the could use a 499 ohm +/-1% resistor.

I ask the USB PHY team if we could change the recommendation from 500 ohm +/-1% to 499 ohm +/-1% to make resistor selection easier for our customers. They confirmed this would be okay, so we changed the recommendation in the datasheet.

I assume your board has two 1 kohm +/-1% resistors connected in parallel, and you are asking if this will be okay. This should be okay since the USB PHY was initially designed for a 500 ohm +/-1% resistor.

Regards,

Sreenivasa

Hi Board designers, 

Additional inputs regarding calib resistor tolerance

Feedback from the IP owner is that the RCALIB resistor should not exceed 1% at any operating condition for the lifetime of the product. This applies to both USB and CSI.

What is the lifetime requirement for resistor tolerance on DDR0_CAL0 (pin H6)? 

Yes, it has a similar lifetime requirement that the DDR0_CAL0 resistor has to stay within 1% tolerance

You mentioned we should use alternate resistor for our evaluation - Does this means we have to use a resistor whose tolerance is with in 1% throught out temperature , throughout lifetime. If yes then I don't have any further questions :-)

Regards,

Sreenivasa

Hi Board designers, 

Refer below additional inputs:

Expert input:

As with any other requirement, if the violate it, they’re just adding more risk in their design.  In this case, IO calibration on the processor, which runs periodically in the background, will be compromised.  I wouldn’t recommend it.

Regards,

Sreenivasa

Hi Board designers, 

Refer below additional inputs: