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Original question:

LMK04208: LMK04208 uWire input signals logic level

LMK04208: LMK04208 uWire input signals logic level

Amishav Ganot
Prodigy 40 points
Part Number: LMK04208
Other Parts Discussed in Thread: USB2ANY,

Hi,

Regarding the 15K series resistors -

1. do they limit the uWire bit rate? if so, to what extent?

2. we have had difficulties communicating with the LMK0xxxx via uWire, until we changed the series resistors to 50R. is this a known issue and a valid solution for maintaining the ESD/OV protection?

Thanks!

  • 0
    TI__Genius 12550 points

    Hi Amishav,

    USB2ANY can provide 3.3V and 5V logic level.  

    To determine which voltage the USB2ANY is outputting, you must look at the device's pinouts. The pinouts for the USB2ANY are provided in the USB2ANY user guide. If you use the 10 pin configuration, the 3.3 V is supplied from cable pin 5 (shown below).

    LMK04208 EVM has given the voltage divider provision using the 15k and 27k resistor, when 5V logic. With 10pin configuration (If a USB2ANY provides 3.3 V to the SPI), these resistors are not required and you can keep series 50ohm (as you have) or 10ohm to protects against high voltage spikes during communication. The series resistor is also used for impedance matching between the source and the load to maximize power transfer.

    Regards,

    Ajeet Pal