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LMH6521 - Serial Mode Not Responding

Other Parts Discussed in Thread: LMH6521


I am using a LMH6521 to amplify a 125 MHZ signal. I have a custom board I am talking to with the SPIUS2 SPI controller. I have the CLK, CS, SDI, SDO connected between the SPIUS2 and the LMH6521 with a 470 Ohm resistor from the SDO(LMH6521) up to 3.3V to pull it up. I have ensured the +5V is applied to pins 27 and 14. ENA is grounded, while ENB is tied high to 3.3V. MOD0 and MOD1 are at 0 V and 3.3V respectively for SPI mode. However, I am unable to communicate with the unit! When I switch to parallel mode, the amplifier works. In SPI mode I never receive information on the SPI, and the amplifier attenuates all signals - no signals come through.


I have checked, and the SPI signals make it all the way through the board to the chip - I just get no response!


Any thoughts would be appreciated.