OPA858DSGEVM: OPA858DSGEVM || Not working

Shine Jo Tom

Part Number: OPA858DSGEVM
Other Parts Discussed in Thread: OPA858

Hi,

I purchased an OPA858DSGEVM from TI recently. But when I connect the power supply and without using the header for J4, I'm getting the Power supply voltage 3.3V at pin-8 (PD). But in the schematics of the EVM I got from www.ti.com/.../sbou200.pdf I don't see any connection from Vcc to PD. Why is it seen this way? Also, when I tried to test it by giving a sine wave of 1Vp-p, I'm not getting any output from the opamp.

over 3 years ago

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Shine,

you mean there's no connection from VCC to pin 1 of J4?

Kai

0 Shine Jo Tom over 3 years ago in reply to kai klaas69

Prodigy 120 points

There is a connection. I get a voltage of 3.3V at the PD pin but I can't see that on the schematics. The board worked fine when I connected VEE.

0 kai klaas69 over 3 years ago in reply to Shine Jo Tom

Guru 140200 points

Hi Shine,

the connection from VCC to pin 1 of J4 is made in the VCC plane. See figures 4 and 5 of the EVM's user guide:

Kai

0 Shine Jo Tom over 3 years ago in reply to kai klaas69

Prodigy 120 points

That is true but I couldn't see a connection to the pin2 of the J4 and still PD pin shows high. Basically even without the jumper put on, I'm getting the Vcc at PD pin of the opamp which is fine but I'm just curious as to know why it is like that.

0 kai klaas69 over 3 years ago in reply to Shine Jo Tom

Guru 140200 points

Hi Shine,

eventually the OPA858 has a pull-up internally at the /PD pin?

Kai

0 Sima Jalaleddine over 3 years ago

TI__Mastermind 28915 points

Hello Shine,

For normal operation, power down connection must be set to logic high. The power-down pin must be set at or above the threshold specified in the device datasheet:

On the EVM, you should connect a jumper between terminals 1 and 2. Let us know if that fixes the issue.

Thank you,

Sima

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OPA858DSGEVM: OPA858DSGEVM || Not working