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Power Supplies
5
Power Supplies
J4 is the power-supply input connector.
lists the configuration details for J4. The voltage inputs to
the DAC can be applied directly to the device. The DAC8728 requires multiple power supplies to operate.
AV
DD
, AV
SS
, DV
DD
, and IOV
DD
are required to properly power the DAC. The power should be applied in this
order: IOV
DD
, DV
DD
, then AV
DD
and AV
SS
, followed by the reference voltage.
CAUTION
This sequence must be followed in order to prevent damage to the device.
Table 9. J4 Configuration: Power-Supply Input
Pin No.
Pin Name
Function
Required
J4.1
+VA
+8V to +36V analog supply
Yes
J4.2
-VA
–18V to –4.5V analog supply
Yes
J4.3
+5VA
+5V analog supply
No
J4.4
-5VA
-5V analog supply
No
J4.5
DGND
Digital ground input
Yes
J4.6
AGND
Analog ground input
Yes
J4.7
+1.8VD
1.8V digital supply
Optional
J4.8
+3.3VD
3.3V digital supply
Optional
J4.9
VD1
Not used
No
J4.10
+5VD
+5V digital supply
Optional
NOTE:
To avoid damage to the DAC8728, DV
DD
must stay greater than or equal to IOV
DD
.
The DAC8728EVM board analog section can be powered from either a single-supply or dual supply. In
unipolar mode, AV
SS
is tied to AGND and AV
DD
is powered from +VA, a +8 to +36V analog supply range.
When the DAC8728 is run in bipolar mode, AV
SS
and AV
DD
are required. AV
SS
can range from –4.5V to
–18V, and AV
DD
can range from +4.5V to +18V. The DAC8728 AV
DD
(+VA) supply can be as low as
+4.5V, but in order to properly power the REF02, +VA must be at least +8V. Jumper JP14 allows the user
to select between bipolar and unipolar modes. AV
SS
is either routed to the –VA (pin J4.2) or is connected
to AGND.
DV
DD
powers the digital core of the DAC8728 and can vary from V
REF
to +5.5V. Care must be taken to
ensure that the EVM is not set up in a state where V
REF
is greater than DV
DD
. Jumper JP15 allows the user
to select b3.3V and +5V for DV
DD
.
The IOV
DD
supply sets the voltage of the digital interface and should be configured to match the I/O
voltage of the host processor. Jumpers JP19 and JP20 allow the user to select b1.8V, +3.3V,
and +5V for IOV
DD
. To avoid damaging the DAC8728, DV
DD
must stay greater than or equal to IOV
DD
.
Alternate power sources can be applied via various test points located on the EVM. Refer to the schematic
at the end of this document for details.
NOTE:
While filters are provided for all power-supply inputs, optimal performance of the EVM
requires a clean, well-regulated power source.
11
SBAU161 – February 2010
DAC8728EVM
Copyright © 2010, Texas Instruments Incorporated