WM8753LEBSLASHRV datasheet(20/87 Pages) WOLFSON

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WM8753L

AI Rev 3.1 June 2004

POWER CONTROL

The design of the WM8753L has given much attention to power consumption without compromising

performance. It operates at very low voltages, and includes the ability to power off any unused parts

of the circuitry under software control, and includes standby and power off modes.

OPERATION SCENARIOS

Flexibility in the design of the WM8753L allows for a wide range of operational scenarios, some of

which are proposed below:

Telephony with MP3 playback: The voice codec may be used as standard voice codec, and the

stereo DAC used for MP3 type playback. The user may choose to transmit the mono version of the

MP3 playback to the Tx side of the phone conversation as required. Recording of the phone

conversation would then require to be supported in the digital domain, after the voice codec. (digital

Tx and Rx sides of the conversation would need to be digitally summed as required).

Telephony with recording: In many smart-phone applications the voice codec for voice conversion will

be included in the cellphone base-band chipset. In such cases the analog (often differential) mic input

and speaker outputs from this voice codec will be routed to the WM8753L line or mic inputs, and

mono outputs. The WM8753L will then provide the buffers to connect to the system transducers

(speakers, mics, headphones etc.) and also the stereo hi-fi DAC and mixers to allow MP3 type

playback. The ADC may then be used for recording the phone conversation, both Tx and Rx parts,

and the extra DAC might be used for generation of confirmation tones or ringtones as required.

Bluetooth Hi-Fi stereo headset; In Bluetooth headsets a mono PCM codec is required for the

standard telephony quality voice channel. But for the support of compressed hi-fi quality stereo, a hi-fi

quality stereo DAC is required. In this case WM8753L can supply both these needs. The BTL speaker

driver could be recommitted as either stereo headphone driver, or stereo speaker driver, and perhaps

the other headphone output re-used as stereo line output.

Analog FM tuner support: An analog stereo FM tuner might be connected to the Line inputs of

WM8753, and the stereo signal listened to via headphones, or transmitted over the ‘phone.

INPUT SIGNAL PATH

The WM8753L has a combination of analogue inputs, microphone preamps, mixers and switches

allowing flexibility in the configuration of the input to left and right ADCs and to analogue bypass

paths into the Left, Right and Mono output Mixers. The input to the ADC may be routed through a

PGA whose gain is controlled either by the user or by the on-chip ALC function (see Automatic Level

Control). The ADCs may be powered off independently and a single ADC may be used for left and

right ADC input mono mixing.

SIGNAL INPUTS

The WM8753L has three sets of high impedance, low capacitance AC coupled differential inputs as

well as two high impedance, low capacitance AC coupled mono line inputs. Two of the differential

inputs (MICIN1/MICIN1N and MICIN2/MICIN2N) have a microphone pre-amp and selectable gain of

+12dB to +30dB in 6dB steps. RXN and RXP are a differential line input and can also be configured

as a stereo to mono mix input. In addition there are two mono LINE inputs (LINE1 and LINE2) which

can be used as a single stereo input.

The LINE1 and LINE2 inputs may be configured as a differential input or a stereo to mono mix using

the Line input mixer under the control of register bits LMSEL. The LMSEL bits also allow either one

of the inputs to be enabled and the other disabled. The Line mixer output may then be routed to the

ALC mixer by setting LINEALC and/or to the output Mono mixer via the bypass path. The Line mixer

has -6dB of gain so that a 0dB signal on LINE1 and LINE2 will sum to give a 0dB signal at the mixer

output.

There is an analogue input to analogue output bypass path into the Left, Right and Mono output

mixers. The Left bypass path may be selected to be either the output of the RX mixer or the LINE1

input under the control of LM. The Right bypass path may be selected to be either the output of the

RX mixer or the LINE2 input under the control of RM. The Mono bypass path may be selected to be

either the output of the Line mixer or the RX mixer under the control of MM.

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