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Power Supplies
There are two static I/O pins, LDAC and CLR, from the DACx562 that are routed to the J2 header. Both of
signals have weak pull-up resistors to the AVDD power-supply voltage. Either of these signals can be
pulled down using hardware jumpers or applying signals to the J2 header. Note that these signals are
edge-triggered.
The CLR pin is routed to pin J2.19. The LDAC pin is routed to either J2.15 or J2.17, selectable using the
JP6 onboard jumper. Updating the DACx562 output can be completed in one of three different ways. The
LDAC pin can be held low, and the output then update immediately following the last SCLK of the data
word. Alternatively, the LDAC can be held high, the DAC input register can be written to, and the output
then updates once the LDAC signal is brought low. A third technique is to overwrite the LDAC pin using
either register settings or DACx562 commands. See the
product data sheet
for more information.
4
Power Supplies
J3 is the power-supply input connector.
Table 3
lists the configuration details for J3. The voltage inputs to
the DAC can be applied directly to the device. The DACx562 requires only one power supply to operate.
Table 3. J3 Configuration: Power-Supply Input
Pin No.
Pin Name
Function
Required
J3.1
+VA
+VA analog supply
Optional
J3.2
–
VA
–
VA analog supply
Optional
J3.3
+5VA
+5V analog supply
Yes
J3.4
–
5VA
-5V analog supply
No
J3.5
DGND
Digital ground input
Yes
J3.6
AGND
Analog ground input
Yes
J3.7
+1.8VD
1.8V digital supply
No
J3.8
+3.3VD
3.3V digital supply
No
J3.9
VD1
Not used
No
J3.10
+5VD
+5V
No
The digital and analog ground inputs are short-circuited internally through a ground plane.
The DAC8562EVM is designed to operate from a 5V power supply (J3.3). This supply powers the
DACx562 itself, and the onboard REF5025 reference voltage source.
The DACx562 can be powered from a wide range of voltages from +2.7V to +5.5V. The onboard REF5025
is powered from the +5VA supply on the J3 header. Jumper JP4 is in place to allow users to choose
between the +5VA voltage to power the DAC or a separate, external power supply applied to TP1. This
flexibility allows the user to be able to properly power the REF5025 while powering the DAC from any
desired voltage within the specified range. The DAC8562EVM is not designed with any filters, so the use
of a clean, well-regulated supply is strongly recommended.
The +VA and
–
VA supplies are only used to power the optional external op amp, U4, and that is only if the
bipolar circuit is installed. Currently, the op amp is uninstalled and the EVM board does not require the
+VA and
–
VA supplies. If the op amp is installed, J3.1 and J3.2 must be powered by
±
15V in order for the
bipolar circuit to be functional.
5
SBAU183A
–
May 2011
–
Revised June 2011
DAC7562EVM, DAC8562EVM
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2011, Texas Instruments Incorporated
