WM8918 datasheet(16/176 Pages) CIRRUS

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WM8918

Production Data

PD, Rev 4.1, January 2012

POWER CONSUMPTION

The WM8918 power consumption is dependent on many parameters. Most significantly, it depends

on supply voltages, sample rates, mode of operation, and output loading.

The power consumption on each supply rail varies approximately with the square of the voltage.

Power consumption is greater at fast sample rates than at slower ones. When the digital audio

interface is operating in Master mode, the DBVDD current is significantly greater than in Slave mode.

(Note also that power savings can be made by using MCLK as the BCLK source in Slave mode.) The

output load conditions (impedance, capacitance and inductance) can also impact significantly on the

device power consumption.

COMMON TEST CONDITIONS

Unless otherwise stated, the following test conditions apply throughout the following sections:



Ambient temperature = +25°C



Audio signal = quiescent (zero amplitude)



Sample rate = 48kHz



MCLK = 12.288MHz



Audio interface mode = Slave (LRCLK_DIR=0, BCLK_DIR=0)



SYSCLK_SRC = 0 (system clock comes direct from MCLK, not from FLL)

Additional, variant test conditions are quoted within the relevant sections below. Where applicable,

power dissipated in the headphone or line loads is included.

POWER CONSUMPTION MEASUREMENTS

Stereo Playback to Headphones

- DAC input to HPOUTL+HPOUTR pins with 30Ω load.

Test conditions:

VMID_RES = 01 (for normal operation)

CP_DYN_PWR = 1 (Class-W, Charge pump controlled by real-time audio level)

Variant test conditions

AVDD

DCVDD

DBVDD

CPVDD

MICVDD

TOTAL

48kHz sample rate

1.80

1.69

1.00

0.76

1.80

0.00

1.80

0.31

2.50

0.01

4.38

8kHz sample rate

1.80

1.69

1.00

0.18

1.80

0.00

1.80

0.31

2.50

0.01

3.80

48kHz, Po = 0.1mW/channel

1kHz sine wave 0dBFS

HPOUT_VOL= -25dB

DAC_VOL= 0dB

1.80

1.71

1.00

0.77

1.80

0.00

1.80

1.99

2.50

0.01

7.45

48kHz, Po = 1mW/channel

1kHz sine wave 0dBFS

HPOUT_VOL= -15dB

DAC_VOL= 0dB

1.80

1.73

1.00

0.77

1.80

0.00

1.80

5.61

2.50

0.01

13.99

48kHz sample rate, Master mode,

FLL enabled, MCLK input frequency =

13MHz

1.80

1.82

1.00

1.05

1.80

0.73

1.80

0.30

2.50

0.01

6.18

48kHz sample rate, Master mode,

FLL enabled, MCLK input frequency =

32.768kHz

1.80

1.83

1.00

0.94

1.80

0.76

1.80

0.29

2.50

0.01

6.14

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