LM4857

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An audio power amplifier, connected to the VB power rail (battery terminal voltage) for power.
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The '''LM4857''' is an audio power amplifier and part of the [[Neo1973 audio subsystem]]. It's connected to the VB power rail (battery terminal voltage) for power and thus needs to be powered off separately from the main system.
  
The audio power output may vary as the battery discharges.
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The audio power output may vary as the battery discharges:
  
* 0.5W stereo speaker output, used for the main speakers.
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* 0.5W per-channel stereo speaker output, used for the main speakers (LLS+- and RLS+-)
* 33mW stereo headphone output (32 ohms), for the headphones.
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* 33mW per-channel stereo headphone output (32 ohms), for the headset (LHP and RHP)
* 43mW mono earpiece output, for the earpiece.
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* 43mW mono earpiece output, for the earpiece (EP+-)
 
* Line-out, unused.
 
* Line-out, unused.
  
[http://www.national.com/pf/LM/LM4857.html The National Semiconductor Datasheet provides additional information.]
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There is a stereo (LIN and RIN) and a mono (MIN) input.
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Mixer settings starting "Amp" control it via [[I2C]], including:
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* Amp Mode: Off, Call Speaker, Stereo Speakers, Stereo Speakers + Headphones, Headphones
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* The volume controls Amp Left and Amp Right, and Amp Mono
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* Amp Earpiece 6dB toggle amplifies the call speaker output
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== External links ==
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* [http://www.national.com/pf/LM/LM4857.html The National Semiconductor Datasheet for LM4857]
  
 
[[Category:Neo1973 Hardware]]
 
[[Category:Neo1973 Hardware]]

Revision as of 20:08, 26 November 2007

The LM4857 is an audio power amplifier and part of the Neo1973 audio subsystem. It's connected to the VB power rail (battery terminal voltage) for power and thus needs to be powered off separately from the main system.

The audio power output may vary as the battery discharges:

  • 0.5W per-channel stereo speaker output, used for the main speakers (LLS+- and RLS+-)
  • 33mW per-channel stereo headphone output (32 ohms), for the headset (LHP and RHP)
  • 43mW mono earpiece output, for the earpiece (EP+-)
  • Line-out, unused.

There is a stereo (LIN and RIN) and a mono (MIN) input.

Mixer settings starting "Amp" control it via I2C, including:

  • Amp Mode: Off, Call Speaker, Stereo Speakers, Stereo Speakers + Headphones, Headphones
  • The volume controls Amp Left and Amp Right, and Amp Mono
  • Amp Earpiece 6dB toggle amplifies the call speaker output

External links

Personal tools

An audio power amplifier, connected to the VB power rail (battery terminal voltage) for power.

The audio power output may vary as the battery discharges.

  • 0.5W stereo speaker output, used for the main speakers.
  • 33mW stereo headphone output (32 ohms), for the headphones.
  • 43mW mono earpiece output, for the earpiece.
  • Line-out, unused.

The National Semiconductor Datasheet provides additional information.