DAC7513 datasheet(15/18 Pages) TI

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DAC7513

SBAS157A

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FIGURE 10. Bipolar Operation with the DAC7513.

DAC7513

REF

OUT

10k

Ω

10k

Ω

3-Wire

Serial

Interface

REF

µF

0.1

µF

–5V

±5V

+5V

OPA703

APPLICATIONS

USING REF02 AS A POWER SUPPLY FOR THE

DAC7513

Due to the extremely low supply current required by the

DAC7513, an alternative option is to use a REF02 +5V

precision voltage reference to supply the required voltage to

the part, as shown in Figure 9. This is especially useful if the

power supply is quite noisy or if the system supply voltages

are at some value other than 5V. The REF02 will output a

steady supply voltage for the DAC7513; if the REF02 is

used, the current it needs to supply to the DAC7513 is

132

µA. This is with no load on the output of the DAC, so

when the DAC output is loaded, the REF02 also needs to

supply the current to the load. The total current required (with

a 5k

Ω load on the DAC output) is:

132

µA + (5V/5kΩ) = 1.13mA

The load regulation of the REF02 is typically 0.005%/mA,

which results in an error of 285

µV for the 1.13mA current

drawn from it; this corresponds to a 0.2LSB error.

BIPOLAR OPERATION USING THE DAC7513

The DAC7513 has been designed for single-supply operation,

but a bipolar output range is also possible using the circuit in

Figure 10 which will give an output voltage range of

±V

REF.

Rail-to-rail operation at the amplifier output is achievable using

an OPA703 as the output amplifier.

The output voltage for any input code can be calculated as

follows:

REF

















−





















••

•

4096

where D represents the input code in decimal (0 to 4095).

With VREF = 5V, R1 = R2 = 10kΩ:

10 •D

4096

– 5V

O =









This is an output voltage range of

±5V with 000

H correspond-

ing to a –5V output and FFFH corresponding to a +5V output.

Similarly, using VREF = 2.5V, ±2.5V output voltage raw can be

achieved.

LAYOUT

A precision analog component requires careful layout, ad-

equate bypassing, and clean, well-regulated power supplies.

As the DAC7513 offers single-supply operation, it will often

be used in close proximity with digital logic, microcontrollers,

microprocessors, and digital signal processors. The more

digital logic present in the design and the higher the switching

speed, the more difficult it will be to achieve good perfor-

mance from the converter.

Due to the single ground pin of the DAC7513, all return

currents, including digital and analog return currents, must

flow through the GND pin, which would, ideally, be connected

directly to an analog ground plane. This plane would be

separate from the ground connection for the digital compo-

nents until they were connected at the power-entry point of

the system.

FIGURE 9. REF02 as Power Supply to the DAC7513.

REF02

DAC7513

3-Wire

Serial

Interface

+5V

132

µA (I

DD + IREF)

OUT = 0V to 5V

SYNC

SCLK

+15

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