DAC8760: DAC8760 Iout 4 ~ 20mA output question

Howdy Chun,

And thanks for the post.  Can you provide a schematic of your application, or if you wish to keep private you can send a friend request so I may send you my email address.

That being said, I'd be curious to know the connection scheme of VOUT, +VSENSE and IOUT.  If both VOUT and IOUT are tied together, with +VSENSE connected, this may be origin of the error, which is described in page 43 of the DS:

"When the VOUT and IOUT pins are tied together, bit 8 of the Configuration Register (DUAL OUTEN) must be set to 0. Bits 2 down to 0 of the Control Register (RANGE) control VOUT and IOUT. Special consideration must be paid to the +VSENSE pin in this case. When VOUT is disabled, the +VSENSE pin is connected to the internal amplifier input through an internal 60-kΩ resistor as shown in Figure 83. This internal node has diode clamps to REFIN and GND. Setting bit 6 of the Configuration Register (APD) forces this internal node to be tied to GND through a 10-kΩ resistor, in effect, the +VSENSE pin is tied to GND through a 70-kΩ power-down resistor."

There are ways around this issue, which I can follow up with, but first would like to see if this is indeed the case.

Best Regards,

Matt

Hi Chun,

It looks like you're employing the BOOST Configuration for IOUT. As indicated in page 36 of the DS, "there is some gain error introduced by this configuration as seen in Figure 47 for the 0mA to 24mA range." The error is shown in Figure 49 for the 4mA to 20mA Range, page 20. Figure 49 displays a full-scale TUE error of ~0.19%FSR for 4-20mA w/External RSET (BOOST Config). This % error correlates to what you've been measuring, as (0.0019*.016 = 0.0304mA).

If you have any other question please let me know.

Best Regards,
Matt