WM8944BECSSLASHR datasheet(13/165 Pages) CIRRUS

13 / 165 page

WM8944B

Rev 4.3

PARAMETER

SYMBOL

TEST CONDITIONS

MIN

TYP

MAX

UNIT

MICBIAS

Bias voltage (changes

in proportion to

LDOVOUT)

MICBIAS

MICB_LVL = 0

2.55

2.7

2.85

MICB_LVL = 1

1.95

Bias Current source

VMICBIAS within +/-3%

Output noise spectral

density

1kHz to 20kHz

nV/

Hz

PSRR (with respect to

LDOVDD)

217Hz, 100mV pk-pk

1kHz, 100mV pk-pk

Bandgap Reference

Bandgap Voltage

-10%

1.5

+10%

Analogue Reference Levels

Midrail Reference

Voltage (changes in

proportion to

LDOVOUT)

VMID

VMID_REF_SEL = 1

VMID_CTRL=1

1.5

Bandgap Reference

BG_VSEL=01010

-10%

1.5

+10%

Note:

The maximum LDO output current is the total internal and external load capability; internal circuits of the WM8944B will typically

account for 25mA of this capacity.

TERMINOLOGY

Signal-to-Noise Ratio (dB)

– SNR is the difference in level between a full scale output signal and the device output noise with

no signal applied, measured over a bandwidth of 20Hz to 20kHz. This ratio is also called idle channel noise. (No Auto-zero or

Mute function is employed).

Total Harmonic Distortion (dB)

– THD is the difference in level between a 1kHz reference sine wave output signal and the first

seven harmonics of the output signal. The amplitude of the fundamental frequency of the output signal is compared to the

RMS value of the next seven harmonics and expressed as a ratio.

Total Harmonic Distortion plus Noise (dB)

– THD+N is the difference in level between a 1kHz reference sine wave output

signal and all noise and distortion products in the audio band. The amplitude of the fundamental reference frequency of the

output signal is compared to the RMS value of all other noise and distortion products and expressed as a ratio.

Mute Attenuation

– This is a measure of the difference in level between the full scale output signal and the output with mute

applied.

Power Supply Rejection Ratio (dB)

– PSRR is a measure of ripple attenuation between a power supply rail and a signal output

path. With the signal path idle, a small sine wave ripple is applied to power supply rail. The amplitude of the supply ripple is

compared to the amplitude of the output signal generated and is expressed as a ratio.

All performance measurements are carried out with 20kHz AES17 low pass filter for distortion measurements, and an

A-weighted filter for noise measurement. Failure to use such a filter will result in higher THD 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.

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