DAC8562TEVM: VREF Voltage Issue

Adarsh Chengot Poonthottathil

Part Number: DAC8562TEVM

Hallo Team,

I am facing difficulty with DAC8562TEVM board. I am using SPI bus to communicate with the DAC. I powered the DAC externally with 3.3V, LDAC is grounded, CLR is pulled high. After powering up the DAC, I provided the required SPI signals and I was able to communicate with the EVM board. I was able to measure 0V and VCC on disabling and enabling the internal reference voltage respectively. VOUTA and VOUTB was outputting results as expected.

Problem started when applying external reference voltage to the VREF pin. After disabling the internal reference and applying 1.8V to the VREF pin, device started outputting a maximum voltage of 1.8V on its output pins. But after a while, the output vanishes and now the VREF pin reads 315mV. Even after enabling the internal reference voltage, the voltage of the VREF pin does not changes. Now the chip does not respond to any SPI commands.

I ordered a second EVM board, and I had the same experience with it too. Power on reset updates does not seems to fix the issue.

What is causing this issue? Can you please help me to find a solution.

Thank you.

over 2 years ago

0 Adarsh Chengot Poonthottathil over 2 years ago

Prodigy 140 points

Update..

The EVM board consumes about 8mA when supplied with 5V at J3A.3

0 Katlynne Jones over 2 years ago

TI__Mastermind 30838 points

Hi Adarsh,

What is the configuration of JP4? Are you supplying the 1.8V external reference with a power supply or reference IC? When you say the VREF pin reads 315mV, are you talking about the external reference you are supplying?

Best,
Katlynne Jones

0 Adarsh Chengot Poonthottathil over 2 years ago in reply to Katlynne Jones

Prodigy 140 points

Hai Katlynne,

Thank you for your reply.

Katlynne Jones said:
What is the configuration of JP4?

There is no jumper on JP4. I was using JP4.2 to apply external reference voltage of 1.8V from from my external power supply unit.

Katlynne Jones said:
Are you supplying the 1.8V external reference with a power supply or reference IC?

I am not using a reference IC. Just an external power supply of 1.8V.

Katlynne Jones said:
When you say the VREF pin reads 315mV, are you talking about the external reference you are supplying?

VREF pin reads about 300mV it is kept unconnected. That means even if I enable the internal reference voltage of 2.5V, the VREF pin is not updating. It is outputting just ~300mV.

Thank you

0 Akhilesh K over 2 years ago in reply to Adarsh Chengot Poonthottathil

TI__Mastermind 18886 points

Hi,

When you say, you applied 1.8V on JP4.2, and got Vout as 1.8V, did you send the full code?

Can you check the power supply used to power Vref for any start up anomaly? what is the current limit? ideally reference should come from a very low impedance reference IC, not from a power supply which is noisy and can be unregulated at times. Please check on these. Most likely the chip might have been damaged.

Regards,

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DAC8562TEVM: VREF Voltage Issue