PGA970EVM: Unable to generate a sine wave on primary coil

David Ruxton

Part Number: PGA970EVM

Hi, I'm using the PGA970 EVM board through the GUI and it looks like the PC and and PGA are communicating, but I'm having trouble generating a sine wave on my primary LVDT coil. Looking for a 5 kHz sine, and this is what I'm getting scoping TP70 (red) and 71 (blue), this sawtooth form, @ 445 Hz between cursors. I get this regardless of having the LVDT connected or not. TP measurements as follows, GUI settings per screenshot...

T3 = 7.488V

T2 = 4.958V

T4 = 3.295V

TP3 = 1.847V

TP6 = 2.995V

over 5 years ago

0 Scott Cummins over 5 years ago

TI__Mastermind 31655 points

Hi David,

Are you using the power amplifier section of the EVM (J2 and J7 with pins 1 and 2 shorted) or have you bypassed it (J2 and J7 with pins 2 and 3 shorted)?

Can you check what the output is at the PI pin? TP16

Also, have you written the waveform data from the table to the waveform RAM before running the generator?

Regards,

0 David Ruxton over 5 years ago in reply to Scott Cummins

Prodigy 30 points

Hi Scott, I have attached a pic of my setup as is. J2 and J7 are in the state I received the EVM. I believe that's pins 1 and 2 shorted if 1 is the pin with the witness dot by it. TP16 is 14 mV which I'm assuming is essentially zero. If I switch the jumpers on J2 and J7 to pins 2 and 3, that sawtooth drops down to nothing.