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My God the LM386 in AT323 Phone is Working ALL the Time!
Apr 20, 2011
The shocking title came from an AT323 user, who found the LM386 inside the device generating slight but consistent water-like noise during the night. He then measured the current, it was 200mA with 11V input, which means the power consumption is about 2W when not in a call.
Fortunately he found another PA168T phone did not generate the noise. After comparing the hardware difference, he found PA168T used PA1688 pin 53 HFPOW_CTL signal, together with extra S9014+S8550 amplifier, to control on/off of LM386. After applying the same circuit to his AT323, problem solved and the working current reduced to 170mA.
Actually he was not the first to find the LM386 problem. Customers pointed the same PA168S design problem back in 2003, and we made the change with PA168T design in 2004. I have almost forgot this typical Palmmicro customer-driven product story until this hardware expert brought out the question and solution during the past a few days.
ATCOM IP PHONE AT323 internal PCB image
LM386 is the 8-pin chip right above the E of ATCOM IP PHONE string. Large View

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