WM8778EDS(2004) 查看數據表（PDF） - Wolfson Microelectronics plc
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WM8778EDS Datasheet PDF : 50 Pages
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WM8778
Test Conditions
AVDD = 5V, DVDD = 3.3V, AGND = 0V, DGND = 0V, TA = +25oC, fs = 48kHz, MCLK = 256fs unless otherwise stated.
Programmable Gain Step Size
0.25
0.5
0.75
dB
Programmable Gain Range
1kHz Input
-21
+24
dB
(Analogue)
Programmable Gain Range
1kHz Input
-103
-21.5
dB
(Digital)
Mute Attenuation (Note 6)
1kHz Input, 0dB gain
76
Power Supply Rejection Ratio
PSRR
1kHz 100mVpp
50
20Hz to 20kHz
45
100mVpp
Analogue input (AIN) to Analogue output (VOUT) (Load=10k Ω, 50pF, gain = 0dB) Bypass Mode
0dB Full scale output voltage
1.0 x
AVDD/5
SNR (Note 1)
90
100
THD
1kHz, 0dB
-90
dB
dB
dB
Vrms
dB
dB
1kHz, -3dB
-95
dB
Power Supply Rejection Ratio
PSRR
1kHz 100mVpp
50
dB
20Hz to 20kHz
45
dB
100mVpp
Mute Attenuation
1kHz, 0dB
100
dB
Supply Current
Analogue supply current
AVDD = 5V
48
mA
Digital supply current
DVDD = 3.3V
8
mA
Notes:
1. Ratio of output level with 1kHz full scale input, to the output level with all zeros into the digital input, measured ‘A’
weighted.
2. All performance measurements done with 20kHz low pass filter, and where noted an A-weight filter. Failure to use
such a filter will result in higher THD+N and lower SNR and Dynamic Range readings than are found in the Electrical
Characteristics. The low pass filter removes out of band noise; although it is not audible it may affect dynamic
specification values.
3. VMID decoupled with 10uF and 0.1uF capacitors (smaller values may result in reduced performance).
4. Harmonic distortion on the headphone output decreases with output power.
5. All performance measurement done using certain timings conditions (Please refer to section ‘Digital Audio Interface’).
6. A better MUTE Attenuation can be achieved if the ADC gain is set to minimum.
TERMINOLOGY
1. Signal-to-noise ratio (dB) - SNR is a measure of the difference in level between the full scale output and the output
with no signal applied. (No Auto-zero or Automute function is employed in achieving these results).
2. Dynamic range (dB) - DNR is a measure of the difference between the highest and lowest portions of a signal.
Normally a THD+N measurement at 60dB below full scale. The measured signal is then corrected by adding the 60dB
to it. (e.g. THD+N @ -60dB= -32dB, DR= 92dB).
3. THD+N (dB) - THD+N is a ratio, of the rms values, of (Noise + Distortion)/Signal.
4. Stop band attenuation (dB) - Is the degree to which the frequency spectrum is attenuated (outside audio band).
5. Channel Separation (dB) - Also known as Cross-Talk. This is a measure of the amount one channel is isolated from
the other. Normally measured by sending a full scale signal down one channel and measuring the other.
6. Pass-Band Ripple - Any variation of the frequency response in the pass-band region.
w
PP Rev 1.7 June 2004
7
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