Datasheet

Voltage Reference

www.ti.com

5 Voltage Reference

The DAC8562EVM has a variety of reference voltage options. The 2.5V internal reference can be used;

the onboard REF5025 reference voltage can be used as an external source for the DAC; or the user can

input his own external reference voltage to the J1 header. Note that on the evaluation board, there is no

additional reference filtering or an op amp to drive the reference. This flexibility allows the user to have the

option to drive the reference directly with his own source.

The ability to have the DACx562 use its internal reference allows the V

REFIN

REFOUT

to be configured as

either an input or an output. When the 2.5V internal reference voltage is used, the pin is an output. When

the DACx562 is configured to use an external reference voltage and the internal reference is disabled, the

pin is an input. Enabling and disabling the DACx562 internal reference is controlled internally through the

DAC registers and can be changed through the SPI communication protocol. Jumper JP3 must be set

accordingly, depending on the configuration of the reference voltage.

By default, the ability to have the DACx562 use its internal reference is disabled, and requires an external

reference voltage. Jumper JP3 controls which external reference source is used. When JP3 is in the 2-3

position (default), the REF5025 is used. When JP3 is in the 1-2 position, the user can input his own

reference voltage to analog header pin J1.20; this reference will then be routed to the DAC8562.

To enable the DACx562 internal reference voltage, make sure that jumper JP3 is either floating or

connected in the 1-2 position. This configuration avoids driving the V

REFIN

REFOUT

pin with the onboard

reference voltage when the DACx562 has the V

REFIN

REFOUT

pin configured as an output. That signal is

conditioned through an onboard OPA379 before it is routed to pin J1.15 on the J1 header. This option

allows the user to drive external components without having to be concerned about the internal reference

source/sink capability.

NOTE: Do not place jumper JP3 in the 2-3 position while using the internal reference. If JP3 is in

the 2-3 position when the internal reference is used, the user will be attempting to drive the

REFIN

REFOUT

pin externally while it is configured as the internal reference voltage output. This

condition may cause permanent damage to the DACx562.

Figure 1. Reference Selection Jumper JP3

DAC7562EVM, DAC8562EVM SBAU183A–May 2011–Revised June 2011

Submit Documentation Feedback