LM49370 Datasheet, PDF (1/100 Pages) National Semiconductor (TI) – Audio Sub-System with an Ultra Low EMI, Spread Spectrum, Class D Loudspeaker Amplifier

February 2007
LM49370
Audio Sub-System with an Ultra Low EMI, Spread
Spectrum, Class D Loudspeaker Amplifier, a Dual-Mode
Stereo Headphone Amplifier, and a Dedicated PCM
Interface for Bluetooth Transceivers
1.0 General Description
The LM49370 is an integrated audio subsystem that supports
both analog and digital audio functions. The LM49370 in-
cludes a high quality stereo DAC, a mono ADC, a stereo
headphone amplifier, which supports output cap-less (OCL)
or AC-coupled (SE) modes of operation, a mono earpiece
amplifier, and an ultra-low EMI spread spectrum Class D
loudspeaker amplifier. It is designed for demanding applica-
tions in mobile phones and other portable devices.
The LM49370 features a bi-directional I²S interface and a bi-
directional PCM interface for full range audio on either inter-
face. The LM49370 utilizes an I²C or SPI compatible interface
for control. The stereo DAC path features an SNR of 85 dB
with an 18-bit 48 kHz input. In SE mode the headphone am-
plifier delivers at least 33 mW_RMS to a 32Ω single-ended
stereo load with less than 1% distortion (THD+N) when
A_V_DD = 3.3V. The mono earpiece amplifier delivers at least
115mW_RMS to a 32Ω bridged-tied load with less than 1% dis-
tortion (THD+N) when A_V_DD = 3.3V. The mono speaker
amplifier delivers up to 490mW into an 8Ω load with less than
1% distortion when LS_V_DD = 3.3V and up to 1.2W when
LS_V_DD = 5.0V.
The LM49370 employs advanced techniques to reduce pow-
er consumption, to reduce controller overhead, to speed de-
velopment 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.
2.0 Applications
■ ^{Smart phones}
■ ^{Mobile Phones and Multimedia Terminals}
■ ^{PDAs, Internet Appliances and Portable Gaming}
■ ^{Portable DVD/CD/AAC/MP3 Players}
■ ^{Digital Cameras/Camcorders}
3.0 Key Specifications
■ ^P_{HP (AC-COUP)} ^(A_V_DD ^{= 3.3V, 32Ω, 1% THD)}
■ ^P_{HP (OCL)} ^(A_V_DD ^{= 3.3V, 32Ω, 1% THD)}
■ ^P_LS ^{( LS_V}_DD ^{= 5V, 8Ω, 1% THD)}
■ ^P_LS ^(LS_V_DD ^{= 4.2V, 8Ω, 1% THD)}
■ ^P_LS ^(LS_V_DD ^{= 3.3V, 8Ω, 1% THD)}
■ ^{Shutdown Current}
■ ^PSRR_LS ^{(217 Hz, LS_V}_DD ^{= 3.3V)}
33 mW
31 mW
1.2 W
900 mW
490 mW
0.8 µA
70 dB
■ ^SNR_LS ^{(AUX IN to Loudspeaker)}
■ ^SNR_DAC ^{(Stereo DAC to AUXOUT)}
■ ^SNR_ADC ^{(Mono ADC from Cell Phone In)}
■ ^SNR_HP ^{(Aux In to Headphones)}
90 dB (typ)
85 dB (typ)
90 dB (typ)
98 dB (typ)
4.0 Features
■ ^{Spread Spectrum Class D architecture reduces EMI}
■ ^{Mono Class D 8Ω amplifier, 490 mW at 3.3V}
■ ^{OCL or AC-coupled headphone operation}
■ ^{33mW stereo headphone amplifier at 3.3V}
■ ^{115 mW earpiece amplifier at 3.3V}
■ ^{18-bit stereo DAC}
■ ^{16-bit mono ADC}
■ ^{8 kHz to 192 kHz stereo audio playback}
■ ^{8 kHz to 48 kHz mono recording}
■ ^{Bidirectional I2S compatible audio interface}
■ ^{Bidirectional PCM compatible audio interface for}
Bluetooth transceivers
■ ^{I2S-PCM Bridge with sample rate conversion}
■ ^{Sigma-Delta PLL for operation from any clock at any}
sample rate
■ ^{Digital 3D Stereo Enhancement}
■ ^{FIR filter programmability for simple tone control}
■ ^{Low power clock network operation if a 12 MHz or 13 MHz}
system clock is available
■ ^{Read/write I2C or SPI compatible control interface}
■ ^{Automatic headphone & microphone detection}
■ ^{Support for internal and external microphones}
■ ^{Automatic gain control for microphone input}
■ ^{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 in 1.5 dB steps}
■ ^{16 Step volume control for microphone in 2 dB steps}
■ ^{Programmable sidetone attenuation in 3 dB steps}
■ ^{Two configurable GPIO ports}
■ ^{Multi-function IRQ output}
■ ^{Micro-power shutdown mode}
■ ^{Available in the 4 x 4 mm 49 bump micro SMDxt package}
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation 201917
www.national.com