WM8778SEDSSLASHR datasheet(7/50 Pages) WOLFSON

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WM8778

PP Rev 1.7 June 2004

Test Conditions

AVDD = 5V, DVDD = 3.3V, AGND = 0V, DGND = 0V, TA = +25

oC, fs = 48kHz, MCLK = 256fs unless otherwise stated.

Programmable Gain Step Size

0.25

0.5

0.75

Programmable Gain Range

(Analogue)

1kHz Input

-21

+24

Programmable Gain Range

(Digital)

1kHz Input

-103

-21.5

Mute Attenuation (Note 6)

1kHz Input, 0dB gain

1kHz 100mVpp

Power Supply Rejection Ratio

PSRR

20Hz to 20kHz

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

Vrms

SNR (Note 1)

100

1kHz, 0dB

-90

THD

1kHz, -3dB

-95

1kHz 100mVpp

Power Supply Rejection Ratio

PSRR

20Hz to 20kHz

100mVpp

Mute Attenuation

1kHz, 0dB

100

Supply Current

Analogue supply current

AVDD = 5V

Digital supply current

DVDD = 3.3V

Notes:

Ratio of output level with 1kHz full scale input, to the output level with all zeros into the digital input, measured ‘A’

weighted.

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.

VMID decoupled with 10uF and 0.1uF capacitors (smaller values may result in reduced performance).

Harmonic distortion on the headphone output decreases with output power.

All performance measurement done using certain timings conditions (Please refer to section ‘Digital Audio Interface’).

A better MUTE Attenuation can be achieved if the ADC gain is set to minimum.

TERMINOLOGY

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).

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).

THD+N (dB) - THD+N is a ratio, of the rms values, of (Noise + Distortion)/Signal.

Stop band attenuation (dB) - Is the degree to which the frequency spectrum is attenuated (outside audio band).

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.

Pass-Band Ripple - Any variation of the frequency response in the pass-band region.

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