DAC904: output current when just power-up

Chi Zhang2

Part Number: DAC904

Hi Expert,

my customer is using DAC904E in fixed network, there is one question needing your help.

when power up the power supply rail, VA to 3.3V, VD to 5V. other pin is floating or not connected. we find the output current will be random between 2mA- 20mA. could you give some comments for the output? if it is random, do you have the distribution map?

Chi

over 2 years ago

0 Chi Zhang2 over 2 years ago

TI__Intellectual 2730 points

sorry, one correction for power, VA and VD are both 3.3V. thanks.

Chi

0 jim s over 2 years ago in reply to Chi Zhang2

TI__Guru* 91947 points

Chi,

Is the clock present at power up? If so, what frequency? Are any of the input data bits toggling? What value is used for Rset?

Regards,

Jim

0 Chi Zhang2 over 2 years ago in reply to jim s

TI__Intellectual 2730 points

Hi, Jim

here is the detailed schematic when power up.

Chi

0 jim s over 2 years ago in reply to Chi Zhang2

TI__Guru* 91947 points

Is clock running at power up? If so, what frequency? Are data bits toggling?

0 jim s over 2 years ago in reply to jim s

TI__Guru* 91947 points

Chi,

On the TI DAC904EVM, VD is drawing 1.4mA and VA is drawing 24.4ma at power up. These power numbers are consistent over many power up cycles.

With a CLK connected, the VD goes up to 8.8mA.

This is a legacy Burr Brown device that was bought out by TI in 2000.Anyone whoever worked on this part is long go. The only data we have available to offer is the data sheet.

Regards,

Jim

0 Chi Zhang2 over 2 years ago in reply to jim s

TI__Intellectual 2730 points

Hi Jim,

Thanks a lot for the DEMO test。

could you also help to check the Iout Pin21 and Pin22 current? thanks

Chi

0 jim s over 2 years ago in reply to Chi Zhang2

TI__Guru* 91947 points

Chi,

No current out of these two pins.

Regards,

Jim

0 Chi Zhang2 over 2 years ago in reply to jim s

TI__Intellectual 2730 points

Hi Jim,

thanks for the test.

this issue is some chips Iout will reach to 18mA when just power-up.

customer has tested more chips. we found that 1-5 chips will have issue through the 1000 chips. these 1-5 chips will always show this issue every time, this large current will damage the next stage MOS.

Have you ever seen this before in other customer side? any advice. thanks.

Chi

0 jim s over 2 years ago in reply to Chi Zhang2

TI__Guru* 91947 points

Chi,

I have not seen this from other customers. Can the customer set PD input high before powering up the DAC? Then once the DAC is ready to be used, set PD input to low.

Regards,

Jim

0 Chi Zhang2 over 2 years ago in reply to jim s

TI__Intellectual 2730 points

ok, thanks. we will try this way.

I just want to confirm we don't have any silicon version with this issue.

Chi

0 jim s over 2 years ago in reply to Chi Zhang2

TI__Guru* 91947 points

Chi,

Not that I am aware of.

Regards,

Jim

0 Chi Zhang2 over 2 years ago in reply to jim s

TI__Intellectual 2730 points

Hi Jim,

do you know the value of pull-down resistor for PD pin? if we don't have the accurate value, just order of magnitudes is okay. thanks.

Chi

0 jim s over 2 years ago in reply to Chi Zhang2

TI__Guru* 91947 points

Chi,

I do not. The data sheet mentions the PD pin will draw around 45uA with 5V present, so I am guessing maybe 100K?

Regards,

Jim

0 Chi Zhang2 over 2 years ago in reply to jim s

TI__Intellectual 2730 points

Jim,

Ok, Thanks.

do we have the G2G upgrade for DAC904, I think we could leverage this opp to promote the new P2P one.

Chi

0 jim s over 2 years ago in reply to Chi Zhang2

TI__Guru* 91947 points

Chi,

What is G2G and P2P? This is a very old device and I am almost sure there has been no upgrades to it.

Jim

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DAC904: output current when just power-up