LMX2582: LMX2582 1.8V IO support

Yarn Guo

Part Number: LMX2582

Hi, Experts:

We are trying to interface with LMX2582 with 1.8V IO due to the limited resource of 3.3V IO in FPGA.

For the digital input signal of LMX2582, I think we need to make sure the MIN number of VOH of FPGA >1.4V and MAX number of VOL< 0.4V.

For the digital output signal of LMX2582, I can use a resistor divider like 10K series resistor and 12K shunt resistor to divide the 3.3V IO down to 1.8V, and also check the input spec of FPGA.

Can you please help to double check if you see any issues regarding this?

Thank you so much for your promot help!

Yarn,

over 8 years ago

0 Noel Fung over 8 years ago

TI__Guru** 122380 points

Hi Yarn,

Correct. For the voltage divider, consider using smaller resistor values if the speed is high.

0 Yarn Guo over 8 years ago in reply to Noel Fung

TI__Intellectual 1440 points

Hi, Noel:
Thank you so much for your prompt help. Yes, I will keep the SPI speed in mind to see if I need to reduce the resistor pair values.
Yarn

0 Yarn Guo over 8 years ago in reply to Noel Fung

TI__Intellectual 1440 points

Hi, Noel:

May I have one more question for connecting the digital output from LMX2582 to 1.8V GPIO of FPGA? The datasheet shows us the typical value of Voh of Vcc-0.4V. DO we have a min value for this? Thank you!

0 Noel Fung over 8 years ago in reply to Yarn Guo

TI__Guru** 122380 points

Hi Yarn,

I think the datasheet is not correct, Vcc-0.4V should be the min. Voh voltage, this is how we normally specify Voh.

0 Yarn Guo over 8 years ago in reply to Noel Fung

TI__Intellectual 1440 points

Hi, Noel:

Understand. That make sense. Thank you for your prompt help.

Yarn

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LMX2582: LMX2582 1.8V IO support