DAC8574IPW datasheet(28/45 Pages) TI

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CURRENT CONSUMPTION

DRIVING RESISTIVE AND CAPACITIVE LOADS

CROSSTALK AND AC PERFORMANCE

OUTPUT VOLTAGE STABILITY

SETTLING TIME AND OUTPUT GLITCH PERFORMANCE

APPLICATION INFORMATION

BASIC CONNNECTIONS

DAC8574

SLAS377B – JANUARY 2003 – REVISED DECEMBER 2004

The DAC8574 typically consumes 225 µA at VDD = 5 V and 200 µA at VDD = 3 V for each active channel,

including reference current consumption. Additional current consumption can occur at the digital inputs if VIH <<

VDD. For most efficient power operation, CMOS logic levels are recommended at the digital inputs to the DAC. In

power-down mode, typical current consumption is 200 nA. A delay time of 10 to 20 ms after a power-down

command is issued to the DAC is typically sufficient for the power-down current to drop below 10 µA.

The DAC8574 output stage is capable of driving loads of up to 1000 pF while remaining stable. Within the offset

and gain error margins, the DAC8574 can operate rail-to-rail when driving a capacitive load. Resistive loads of 2

Ω can be driven by the DAC8574 while achieving very good load regulation. Load regulation error increases as

the output voltage approaches each rail. When the outputs of the DAC are driven to the positive rail under

resistive loading, the PMOS transistor of each Class-AB output stage can enter into the linear region. When this

occurs, the added IR voltage drop deteriorates the linearity performance of the DAC. This only occurs within

approximately the top 20 mV of the DAC's digital input-to-voltage output transfer characteristic. The reference

voltage applied to the DAC8574 may be reduced below the supply voltage applied to VDD in order to eliminate

this condition if good linearity is a requirement at full scale (under resistive loading conditions).

The DAC8574 architecture uses separate resistor strings for each DAC channel in order to achieve ultra-low

crosstalk performance. DC crosstalk seen at one channel during a full-scale change on the neighboring channel

is typically less than 0.5 LSBs. The ac crosstalk measured (for a full-scale, 1 kHz sine wave output generated at

one channel, and measured at the remaining output channel) is typically under –100 dB. In addition, the

DAC8574 can achieve typical ac performance of 96 dB signal-to-noise ratio (SNR) and 65 dB total harmonic

distortion (THD), making the DAC8574 a solid choice for applications requiring high SNR at output frequencies at

or below 4 kHz.

The DAC8574 exhibits excellent temperature stability of

±3 ppm/°C typical output voltage drift over the specified

temperature range of the device. This enables the output voltage of each channel to stay within a

±25 µV window

for a

±1°C ambient temperature change. Good power-supply rejection ratio (PSRR) performance reduces supply

noise present on VDD from appearing at the outputs to well below 10 µV-s. Combined with good dc noise

performance and true 16-bit differential linearity, the DAC8574 becomes a perfect choice for closed-loop control

applications.

Settling time to within the 16-bit accurate range of the DAC8574 is achievable within 10 µs for a full-scale code

change at the input. Worst case settling times between consecutive code changes is typically less than 2 µs. The

high-speed serial interface of the DAC8574 is designed in order to support up to 188ksps update rate. For

full-scale output swings, the output stage of each DAC8574 channel typically exhibits less than 100 mV of

overshoot and undershoot when driving a 200 pF capacitive load. Code-to-code change glitches are extremely

low (~10 µV) given that the code-to-code transition does not cross an Nx4096 code boundary. Due to internal

segmentation of the DAC8574, code-to-code glitches occur at each crossing of an Nx4096 code boundary.

These glitches can approach 100mVs for N = 15, but settle out within ~2 µs.

The following sections give example circuits and tips for using the DAC8574 in various applications. For more

information, contact your local TI representative, or visit the Texas Instruments website at http://www.ti.com.

For many applications, connecting the DAC8574 is extremely simple. A basic connection diagram for the

DAC8574 is shown in Figure 56. The 0.1 µF bypass capacitors help provide the momentary bursts of extra

current needed from the supplies.

DAC8574IPW Datasheet(PDF) 28 Page - Texas Instruments

DAC8574IPW Datasheet(HTML) 28 Page - Texas Instruments

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