AD1856 データシートの表示（PDF） - Analog Devices

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AD1856

16-Bit PCM Audio DAC

Analog Devices 

AD1856

The automatic test equipment digitizes 4096 samples of the

output test waveform, incorporating 23 complete cycles of the

sine wave. A 4096-point FFT is performed on the results of the

test. Based on the first nine harmonics of the fundamental

990.5 Hz output wave, the total harmonic distortion of the

device is calculated. Neither a deglitcher nor an MSB trim is

used during the THD test.

The circuit design, layout, and manufacturing techniques used

in the production of the AD1856 result in excellent THD perfor-

mance. Figure 5 shows the typical unadjusted THD performance

of the AD1856 for various amplitudes of a 1 kHz output signal.

As shown in Figure 5, the AD1856 offers excellent performance,

even at amplitudes as low as −60 dB. Figure 6 shows the typical

THD vs. frequency performance.

10.0

1.0

0.1

16 BITS

0.01

0.001

–60

–50

–40

–30

–20

–10

0

10

AMPLITUDE (dB)

Figure 5. Typical Unadjusted THD vs. Amplitude

Data Sheet

0.100

0.050

0.020

0.010

–20dB

0.005

0.002

FULL SCALE

0.001

1

100

1k

10k

FREQUENCY (Hz)

Figure 6. Typical THD vs. Frequency

OPTIONAL MSB ADJUSTMENT

Use of an optional adjustment circuit allows residual differential

linearity errors around midscale to be eliminated. These errors

are especially important when low amplitude signals are being

reproduced. In these cases, as the signal amplitude decreases,

the ratio of the midscale differential linearity error to the signal

amplitude increases and THD increases.

Therefore, for best performance at low output levels, the optional

MSB adjustment circuitry shown in Figure 7 can be used. This

circuit allows the differential linearity error at midscale to be

zeroed out. However, no adjustments are required to meet data

sheet specifications.

TRIM 15

470kΩ

100kΩ 200kΩ

1 –VS

MSB ADJ 14

Figure 7. Optional MSB Adjustment Circuit

Rev. C | Page 10 of 16

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