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LM4935 Audio Sub-System with Dual-Mode Stereo Headphone & Mono High Efficiency

Loudspeaker Amplifiers and Multi-Purpose ADC

October 2005

LM4935

Audio Sub-System with Dual-Mode Stereo Headphone &

Mono High Efficiency Loudspeaker Amplifiers and

Multi-Purpose ADC

1.0 General Description

The LM4935 is an integrated audio subsystem that supports

both analog and digital audio functions. The LM4935 in-

cludes a high quality stereo DAC, a mono ADC, a multi-

purpose SAR ADC, a stereo headphone amplifier, which

supports output cap-less (OCL) or AC-coupled (SE)modes of

operation, a mono earpiece amplifier and a mono high effi-

ciency loudspeaker amplifier. It is designed for demanding

applications in mobile phones and other portable devices.

The LM4935 features a bi-directional I

2

S serial interface for

full range audio and an I

2

C or SPI compatible interface for

control. The stereo DAC path features an SNR of 88 dB with

an 18-bit 48 kHz input. In SE mode the headphone amplifier

delivers at least 33 mW

RMS

to a 32鈩?single-ended stereo

load with less than 1% distortion (THD+N) when A_V

DD

=

3.3V. The mono earpiece amplifier delivers at least 115

mW

RMS

to a 32鈩?bridged-tied load with less than 1% distor-

tion (THD+N) when A_V

DD

= 3.3V. The mono speaker am-

plifier delivers up to 600 mW into an 8鈩?load with less than

1% distortion when LS_V

DD

= 3.3V and up to 1.3W when

LS_V

DD

= 5.0V. The LM4935 also contains a general pur-

pose SAR ADC for housekeeping duties such as battery and

temperature monitoring. This can also be used for analog

volume control of the output stages and can trigger interrupt

events.

The LM4935 employs advanced techniques to reduce power

consumption, to reduce controller overhead to speed devel-

opment time and to eliminate click and pop. Boomer audio

power amplifiers were designed specifically to provide high

quality output power with a minimal amount of external com-

ponents. It is therefore ideally suited for mobile phone and

other low voltage applications where minimal power con-

sumption, PCB area and cost are primary requirements.

j

Supply Voltage Range

BB_V

DD

= 1.8V to 4.5V,

D_V

DD

& PLL_V

DD

= 2.7V to 4.5V

LS_V

DD

& A_V

DD

= 2.7V to 5.5V

n

n

n

n

n

Shutdown Current

PSRR

@

217 Hz, A_V

DD

= 3.3V, (Headphone)

SNR (Stereo DAC to AUXOUT)

88

SNR (Mono ADC from Cell Phone In)

90

SNR (Aux In to Headphones)

98

1.1 碌A

60 dB

dB (typ)

dB (typ)

dB (typ)

4.0 Features

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

n

18-bit stereo DAC

16-bit mono ADC

12-bit 4 input multipurpose SAR ADC

8 kHz to 48 kHz stereo audio playback

8 kHz to 48 kHz mono recording

1 Hz to 13.888 kHz sample rate on all 4 SAR channels

Bidirectional PCM/I

2

S compatible audio interface

Sigma-Delta PLL for operation from any clock at any

sample rate

Low power clock network operation if 12 MHz system

clock is available

Read/write I

2

C or SPI compatible control interface

33mW stereo headphone amplifier at 3.3V

OCL or AC-coupled headphone operation

Automatic headphone & microphone detection

Support for internal and external microphones

Automatic gain control for microphone input

High efficiency BTL 8鈩?amplifier, 600 mW

@

3.3V

115 mW earpiece amplifier at 3.3V

Differential audio I/O for external cellphone module

Mono differential auxiliary output

Stereo auxiliary inputs

Differential microphone input for internal microphone

Flexible audio routing from input to output

32 Step volume control for mixers with 1.5 dB steps

16 Step volume control for microphone in 2 dB steps

Programmable sidetone attenuation in 3 dB steps

DC Volume Control

Two configurable GPIO ports

Programmable voltage triggers on SAR channels

Multi-function IRQ output

Micro-power shutdown mode

Available in the 4 x 4 mm 49 bump microfil package

2.0 Applications

n

n

n

n

n

Smartphones

Mobile Phones and Multimedia Terminals

PDAs, Internet Appliances and Portable Gaming

Portable DVD/CD/AAC/MP3 Players

Digital Cameras/Camcorders

3.0 Key Specifications

n

n

n

n

n

P

HP (AC-COUP)

@

A_V

DD

= 3.3V, 32鈩? 1% THD

33 mW

@

A_V

DD

= 3.3V, 32鈩? 1% THD

P

HP (OCL)

31 mW

P

LS

@

LS_V

DD

= 5V, 8鈩? 1% THD

1.3 W

P

LS

@

LS_V

DD

= 4.2V, 8鈩? 1% THD

900 mW

P

LS

@

LS_V

DD

= 3.3V, 8鈩? 1% THD

600 mW

Boomer

廬

is a registered trademark of National Semiconductor Corporation.

漏 2005 National Semiconductor Corporation

DS201341

www.national.com

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