LM49250 - Enhanced Emissions Suppression Stereo Class D Audio Sub-System w/ Ground Referenced Headphone Amp

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 8Ω 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.

Products containing the "LM49250" keyword are: LM49250RL , LM49250RL/NOPB , LM49250RL/NOPB , LM49250RLEVAL , LM49250RLX , LM49250RLX/NOPB , LM49250RLX/NOPB

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

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