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

Key Specifications

• Power Output at VDD = 5V Speaker:
  • RL = 4?, THD+N ≤ 1%: 1.97W/Ch
  • RL = 4?, THD+N ≤ 10%: 2.4W/Ch
  • RL =8?, THD+N ≤ 1%: 1.2W/Ch
• Headphone:
  • RL = 16?, THD+N ≤ 1%: 41mW/Ch
  • RL = 32?, THD+N ≤ 1%: 45mW/Ch
• Earpiece:
  • RL = 16?, THD+N ≤ 1%: 170mW
  • RL = 32?, THD+N ≤ 1%: 90mW
• Shutdown Current: 0.1μA
• Efficiency at 5V, 1W into 8?: 87%
• Efficiency at 3.6V, 500mW into 8?: 85%