By: Steve Bush November 17, 2021
Diodes has introduced a digital stereo audio amplifier with a built-in boost converter that allows 8 8W of power to be provided from a lithium-ion battery and 12 12W from two batteries connected in series.
Called PAM8965, the more detailed figures are:
The comprehensive output noise of the audio channel under 26dB (maximum) gain is 70μVrms (A-weighted), and the THD N is 0.035% when 5W power is provided.
Unusually, in class D amplifiers, audio feedback is provided.
"The main feature of PAM8965 is to provide external audio feedback pins," the company said. "Although the internal feedback connection only deals with the non-linearity in the internal feedback loop, the feedback can be connected to the speaker terminals via the external feedback pin Kelvin. This eliminates the need for bonding wires, PCB traces, ferrite beads, and long speaker leads The parasitic resistance and inductance of the audio signal will not adversely affect the fidelity of the audio signal. In addition, the external feedback pin allows the use of a filter network in the feedback path to customize the sound without relying on DSP."
A pin is provided to set the audio gain in 0.5dB steps. The chip uses 41-step automatic gain control to limit the output power without clipping.
The power supply voltage range is 2.8 to 8.5V, and the boost converter output is regulated to 9.2V. It operates in PWM mode at medium and high power and converts to PFM to improve efficiency at low loads.
"The integrated amplifier can achieve 92% system efficiency at 7.4V," the company said. The shutdown current is usually 700nA (maximum value is 5μA).
The boost converter switches outside the audio frequency band (>75kHz) to avoid audible noise from on-board components. Both the converter and amplifier have spread-spectrum modulation for EMI suppression-allowing the use of ferrite bead filtering Device.
The chopper-enabled integrator in the audio channel usually keeps the DC bias at both ends of the speaker below 1mV.
Other protections include: output thermal foldback when the chip is heated, complete thermal shutdown above this temperature, battery undervoltage, battery overvoltage, boost overvoltage, audio output short circuit, boost output short circuit, and cycle-by-cycle boost output current limit. There is a fault flag output.
PAM8965 product page is here
Marked as: Audio Class D Diode Lithium Ion
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