WM1811A datasheet(311/328 Pages) WOLFSON

311 / 328 page

Production Data

WM1811A

PD, November 2013, Rev 4.1

311

IN1L_VOL[4:0],

IN2L_VOL[4:0],

IN1R_VOL[4:0],

IN2R_VOL[4:0]

VOLUME

(dB)

INPUT RESISTANCE

(kΩ)

SINGLE-ENDED

MODE

DIFFERENTIAL

MODE

10101

+15.0

11.9

6.5

10110

+16.5

10.3

5.6

10111

+18.0

8.9

4.8

11000

+19.5

7.7

4.1

11001

+21.0

6.6

3.5

11010

+22.5

5.6

2.9

11011

+24.0

4.8

2.5

11100

+25.5

4.1

2.1

11101

+27.0

3.5

1.8

11110

+28.5

2.9

1.5

11111

+30.0

2.5

1.3

Table 135 PGA Input Pin Resistance

The appropriate input capacitor may be selected using the PGA input resistance data provided in

Table 135, depending on the required PGA gain setting(s).

The choice of capacitor for a 20Hz cut-off frequency is shown in Table 136 for a selection of typical

input impedance conditions.

INPUT IMPEDANCE

MINIMUM CAPACITANCE

FOR 20HZ PASS BAND



F

15k



0.5

F

30k



0.27

F

60k



0.13

F

Table 136 Audio InputDC Blocking Capacitors

Using the figures in Table 136, it follows that a 1

F capacitance for all input connections will give good

results in most cases. Tantalum electrolytic capacitors are particularly suitable as they offer high

stability in a small package size.

Ceramic equivalents are a cost effective alternative to the superior tantalum packages, but care must

be taken to ensure the desired capacitance is maintained at the AVDD1 operating voltage. Also,

ceramic capacitors may show microphonic effects, where vibrations and mechanical conditions give

rise to electrical signals. This is particularly problematic for microphone input paths where a large

signal gain is required.

A single capacitor is required for a line input or single-ended microphone connection. In the case of a

differential microphone connection, a DC blocking capacitor is required on both input pins.

HEADPHONE OUTPUT PATH

The headphone output on WM1811A is ground referenced and therefore does not require the large,

expensive capacitors necessary for VMID reference solutions. The headphone load may be

connected directly to the HPOUT1L and HPOUT1R pins, as illustrated in the “Analogue Outputs”

section.

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