HT8320

Audio Amplifier Integrated with Charge Pump

The HT8320 is a highly efficient 2*4.5W stereo Class-D audio power amplifier with anti-clipping function

(ACF) for applications of battery-powered portable devices. It integrates a filter-less Class-D audio amplifier

with an adaptive dual charge pump regulator. It operates from 2.7V to 5.5V supply. When operating with a

4.2V supply voltage, the HT8320 can deliver into two

4Ω load a maximum output power up to 2*4.5W with

10% THD+N.

In HT8320, the power supply rail of the Class-D amplifier output stage is internally boosted and regulated at

6.4V by an adaptive dual charge pump regulator, allowing for a much louder audio output than a

stand-alone one directly connected to the battery. It makes HT8320 an ideal audio solution for portable

devices, which are powered by a single-cell lithium battery while requiring higher audio loudness.

The HT8320 features ACF to constantly monitor and safeguard the audio outputs against the boosted

supply voltage, preventing output clipping distortion, excessive power dissipation, or hazardous speaker

over-load. Once an over-level condition is detected, the ACF lowers the voltage gain of the audio amplifier

proportionally to eliminate output clipping distortion while maintaining a maximum dynamic range of the

audio outputs allowed by the boosted supply voltage. It provides 4 different ACF modes and ACF OFF

mode to adjust different applications.

Class AB amplifier mode is also available for HT8320. Once the EMI Interference from class D and Boost

Converter becomes an annoying problem, HT8320 can be changed into Class AB mode.

As specifically designed for portable device applications, the HT8320 incorporates a shutdown mode to

minimize the power consumption by holding the CTRL pin to ground. It also includes comprehensive

protection features against various operating faults such as over-current, over-temperature, and

under-voltage for a safe and reliable operation.

1. Dual Charge Pump Regulator

To allow for a much louder audio output, an integrated adaptive dual charge pump regulator is employed to

boost PVDD, the power rail for the Class-D amplifier output stage. Whenever the audio outputs are higher

than a prescribed level, the charge pump regulator will be activated to boost and regulate CPOUT at 6.4V.

In this case, the charge pump regulator operates in the regulation mode. For a proper operation, the

boosted voltage CPOUT generated by the charge pump regulator must be externally shorted to PVDD pins

via a sufficiently wide metal trace on the system board.

On the other hand, when the audio outputs are less than a prescribed level for an extended period of time,

the charge pump regulator will be de-biased and forced into the standby mode. In the standby mode, the

amplifier output stage is powered directly by VBAT, the battery voltage, through an internal power switch.

This adaptive nature of the charge pump regulator can greatly improve the power efficiency of HT8320

when playing audio and thus extends battery life.

1.1.

A nominal value of 4.7

μF is recommended for the flying capacitors (between CxP and CxN) of the charge

pump regulator. A low equivalent-series-resistance (ESR) ceramic capacitor, such as X7R or X5R, is

recommended.

1.2.

For best perfor

mance, a 10μF low ESR ceramic capacitor in parallel with a tantalum or electrolytic capacitor

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