DAC1282 Datasheet, PDF (26/43 Pages) Texas Instruments – LOW DISTORTION DIGITAL-TO-ANALOG CONVERTER FOR SEISMIC

DAC1282
SBAS490 – DECEMBER 2011
www.ti.com
At power-on, when the latter of DVDD exceeds approximately 1.3 V, or the difference of AVDD – AVSS exceeds
approximately 1.4 V, an internal power-on reset (POR) occurs. During POR, the device is held in a reset
condition for a period of 2¹⁶ f_CLK periods as shown in Figure 43. During this time, the DAC1282 output is held at 0
V, differential. SPI communications are not possible during this time. After the reset time elapses, the default
settings are loaded: 31.25 Hz, 28 mV_RMS amplitude, and output switch off. SPI communications can then be
started.
AVDD - AVSS
DVDD
1.4 V nom
1.3 V nom
CLK
Status
2¹⁶ t_CLK
Reset
Operational
Figure 43. Power-On Sequence
Power Consumption
The power consumed by the DAC1282 depends on the analog gain. Table 13 shows the DAC power
consumption.
ANALOG GAIN
1/1
1/2
1/4
1/8
1/16
1/32
1/64
Table 13. Power Consumption
POWER (mW)⁽¹⁾
38
28
23
21
20
20
20
(1) Typical power consumption with V_REF = 5 V and V_OUT = 0 V. Excludes pulse mode.
Offset and Gain Error
The DAC1282 features a low offset error ( ±7/Gain + 50 ppm FS typical) and low gain error (0.1 % typical). Offset
and gain drift are also very low for the DAC1282. Drift is calculated using the box calculation method of
Equation 4:
Drift Calculation = (Max – Min)/Temperature Range (ppm/°C)
Where:
Max and Min are, respectively, the maximum and minimum offset and gain errors (in ppm) recorded over the
specified temperature range of –40°C to +85°C.
(4)
Gain match is the gain error of Gain = 1/1 relative to all analog gains.
Signal-to-Noise Ratio (SNR)
The DAC1282 achieves excellent signal-to-noise ratio (SNR) performance. The SNR data are obtained using the
DAC circuit of Figure 50 and data captured by the ADS1282.
SNR is measured with a signal level of –0.5 dBFS and a 31.25-Hz test frequency, then taking the fast fourier
transform (FFT) of 4096 data points from the ADS1282, using complementing gains. The noise power is
calculated over the bandwidth of 413 Hz (1-ms sample period). The dc, fundamental, and harmonic bins are
removed to calculate the SNR. The SNR measurement represents the combination of the ADS1282 SNR and the
SNR of the DAC1282.
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