Audio Subsystem 36-Pin uSMD T/R

The LM49250 is a fully integrated audio subsystem designed for stereo cell phone applications. The LM49250 combines a 2.4W/Ch stereo class D speaker amplifiers with a 45mW/Ch stereo ground referenced headphone amplifier, a class AB earpiece amplifier, TI 3D enhancement, volume control, and an input mixer into a single device. The filterless class D amplifiers deliver 1.2W/Ch into an 8? load with <1% THD+N from a 5V supply. The LM49250 features a new circuit technology that utilizes a charge pump to generate a negative supply voltage. This allows the headphone outputs to be biased about ground, thereby eliminating the output-coupling capacitors. For improved noise immunity, the LM49250 features fully differential left, right and mono inputs. The three inputs can be mixed/multiplexed to any output combination of the loudspeaker, headphone or earpiece amplifiers. The left and right differential inputs can be used as separate single-ended inputs, mixing multiple stereo audio sources. The mixer, volume control, and device mode select are controlled through an I2C compatible interface. Output short circuit and thermal overload protection prevent the device from being damaged during fault conditions. Superior click and pop suppression eliminates audible transients on power-up/down and during shutdown.

Output Short Circuit Protection

Thermal Overload Protection

Stereo Filterless Class D Operation

Spread Spectrum Modulation

Ground Referenced Headphone Drivers

I²C Control Interface

32-Step Input Volume Control

Output Volume Control

Minimum External Components

Click and Pop Suppression

Micro-Power Shutdown

Available in Space-Saving 36–Bump DSBGA Package

Single Supply Operation

RF Suppression

Power Output at V_DD = 5V Speaker:

• R_L = 4?, THD+N = 1%: 1.97W/Ch
• R_L = 4?, THD+N = 10%: 2.4W/Ch
• R_L =8?, THD+N = 1%: 1.2W/Ch

Headphone:

• R_L = 16?, THD+N = 1%: 41mW/Ch
• R_L = 32?, THD+N = 1%: 45mW/Ch

Earpiece:

• R_L = 16?, THD+N = 1%: 170mW
• R_L = 32?, THD+N = 1%: 90mW

Shutdown Current: 0.1µA

Efficiency at 5V, 1W into 8?: 87%

Efficiency at 3.6V, 500mW into 8?: 85%