LMX2582: Pins 30, 40 and series SPI resistors

Nandini Muralidharan

Part Number: LMX2582
Other Parts Discussed in Thread: ADC12DL3200EVM,

Tool/software:

Hi,

1) In ADC12DL3200EVM, PLL's pin 30 is connected to GND using 680 ohm PD resistor. In the datasheet, this pin is given as NC.

Can we keep LMX2582's pin 30 as NC?

2) In the same EVM, pin40 is tied to GND. Should the pin be tied to GND or kept as NC?

3) In the same EVM, 100-ohm series resistors are used in PLL's SPI bus. Are they required to be added?

4) Can you please confirm how much current is to be expected on these PLL SPI pins?

Thanks

0 Noel Fung 2 months ago

Hi Nandini,

Pin 30 can be NC, connect to ground directly or via a resistor.

Pin 40 should be GND.

It is always a good practice to add a small series resistor to the digital control pins to limit current and to facilitate debug.

SPI is CMOS, it will not draw current.

0 Nandini Muralidharan 2 months ago in reply to Noel Fung

Hi Noel,

Pin 30 - what is the benefit of adding 680 ohm to GND as given in reference design?

Series resistors - Are 22ohm 63mW resistors sufficient since SPI lines are not going to draw much current?

+1 Noel Fung 2 months ago in reply to Nandini Muralidharan

Hi Nandini,

Pin 30 is not connecting to the die, it does not matter how do we connect pin 30.

Resistor rating is fine.

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