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REF02

15 V

5 V

1.6 mA

SCL

SDA

Interface

DAC7574

DAC7574

SLAS375 – JUNE 2003

APPLICATION INFORMATION (continued)

POWER SUPPLY REJECTION

The positive reference voltage input of DAC7574 is internally tied to the power supply pin of the device. This

eliminate the supply noise appearing at the DAC output, the user must pay close attention to how DAC7574 is

powered. The supply to DAC7574 must be clean and well regulated. For best performance, use of a precision

voltage reference is recommended to supply power to DAC7574. This is equivalent to providing a precision

external reference to the device. Due to low power consumption of DAC7574, load regulation errors are

negligible. In order to avoid excess power consumption at the Schmitt-triggered inputs of DAC7574, the precision

REF2930, REF2933 and REF02 precision voltage references are recommended respectively. These precision

voltage references can be used to supply power for multiple devices on a system.

USING REF02 AS A POWER SUPPLY FOR DAC7574

Due to the extremely low supply current required by the DAC7574, a possible configuration is to use a REF02

+5 V precision voltage reference to supply the required voltage to the DAC7574’s supply input as well as the

reference input, as shown in Figure 42. This is especially useful if the power supply is quite noisy or if the system

supply voltages are at some value other than 5 V. The REF02 outputs a steady supply voltage for the DAC7574.

If the REF02 is used, the current it needs to supply to the DAC7574 is 600 µA typical and 900 µA max for

typical current required (with a 5-k

Ω load on a single DAC output) is:

600 µA + (5 V / 5 k

Ω) = 1.6 mA

The load regulation of the REF02 is typically 0.005%/mA, which results in an error of 400µV for 1.6-mA of current

drawn from it. This corresponds to a 0.33 LSB error for a 0 V to 5 V output range.

Figure 42. REF02 Power Supply

LAYOUT

A precision analog component requires careful layout, adequate bypassing, and clean, well-regulated power

supplies.

converters often have high-frequency glitches or spikes riding on the output voltage. In addition, digital

components can create similar high-frequency spikes as their internal logic switches states. This noise can easily

couple into the DAC output voltage through various paths between the power connections and analog output.

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