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AM4372: GP EVM schematics

Timothy Barr
Genius 3370 points
Part Number: AM4372
Other Parts Discussed in Thread: TPS65218,

1) Looking at the EVM schematic I notice that there is a LDO connected to pin 24 of the TPS65218 that is supplying V1_8BAT. There is also an option to use the DCDC6 output for V1_8BAT, but the 0 ohm is DNI. Also, the data sheet for the TPS65218 states that "Connecting any external load to this pin is not recommended." Can you explain why this is being done on the EVM design? Is there some issue with the DCDC6 supply?

2) On the AC_DET pin (9) of the TPS615218 there is a 10k pull-up and a 0 ohm pull down. Both seem to be installed according to the schematic and BOM. Is this an error?

3) On the EVM schematics page 25 You have the signal LCD_AC_BIAS_EN pin also marked as SYSBOOT18. The TRM has references to SYSBOOT18 but the latest data sheet has no mention of SYSBOOT18.

  • 0
    Genius 3370 points

    Another question on the AM437x EVM. Page 20 of the V1.5 schematics shows an additional 32kHz crystal and some other connections to reserved pins. And page 23 shows some reserved pins connected to a  header. Are these needed for anything specific?

  • 0
    TI__Mastermind 42545 points

    Hi Timothy,

    The GP EVM for the AM4372 is an older design and it will require some research to track down all the answers. 

    1) The connections for pin 24 and the V1_8BAT were changed over a couple of the earlier revisions of the GP EVM schematic. I suspect that the changes were added to accommodate earlier revisions of the TPS65218 and were not removed after that component was updated. I suggest that you follow the recommendations in Powering the AM335x, AM437x, and AM438x With TPS65218 User's Guide (SLVUAA9A).  Other designs such as the AM437x starter kit follow that document.

    2) The AC_DET pin is used in different ways depending on whether it is pulled to IN_BIAS or it is grounded. The EVM was designed to allow the TPS65218 to operate with both configurations. The default mode has the zero ohm resistor connecting AC_DET to ground. This removes AC_DET from control of power up and power down. The 10K resistor could have been removed but we choose to leave it in the design. If AC_DET is needed, only the zero ohm resistor needs to be removed.

    3) SYSBOOT18 is used to enable the CLKOUT2 for Ethernet boot. This is only available on the PG1.2 version of the silicon. The SYSBOOT pins are only referenced in the footnotes to Table 4-10 in the data shee while the function of the sysboot pins is described in the TRM as you referenced. SYSBOOT[18] should have been added to the footnotes in the data manual but it was missed. I will post a bug against the data sheet for the missing mention. 

    Regards, Bill