Datasheet PAM8965 (Diodes) - 10

PAM8965 Detailed Description
The PAM8965 is a stereo Class-D audio amplifier with integrated synchronous boost converter. The device boasts system efficiency of 92% (VBAT = 7.4V), which implies that the boost converter and stereo Class-D amplifier can reach average efficiency of 96% each, negating any advantage of using separate ICs. The high efficiency also allows PAM8965 to deliver 2  12W (10% THD+N with VBAT = 7.4V) in to 2  4Ω speakers without the need of a heat sink. The two Class-D audio channels, the integrated synchronous boost converter, and the high efficiency makes PAM8965 an extremely cost-effective general-purpose audio amplifier. The integration also results in the reduction of external components. With VBAT (input power supply) range of 2.8V to 8.5V, the PAM8965 is perfectly suited for battery applications. The wide input supply range makes it ideal for 1SxP or 2SxP Li-ion battery configurations. In addition, the PAM8965 consumes just 10mA quiescent current (VBAT = 7.4V), and the shutdown current is only 0.7μA (typ), which helps to extend the battery life. The synchronous boost converter provides a regulated output of 9.2V and operates in pulse width modulation (PWM) mode for medium to high load. For light load condition, the converter transitions to pulse frequency modulation (PFM) mode to improve the efficiency of the converter. In PFM mode, to avoid the switching frequency from dropping in to the audio band, the boost converter features an out-of-audio mode, which keeps the switching frequency above 75kHz (typ). This minimizes the possibility of audible vibrations coming from the components mounted on the PCB. In terms of performance, the integrated output noise of the audio channel at maximum gain setting of 26dB is only 70μVrms (A-weighted). Similarly, THD+N is only 0.035% at PO = 5W. The chopper-enabled integrator in the audio channel ensures that the output offset is typically < 1mV at maximum gain. The headlining feature of PAM8965 is the provision of external audio feedback pins. While internal feedback connection takes care of nonlinearities only in the internal feedback loop, with external feedback pins, the feedback can be Kelvin-connected to the speaker terminals. This eliminates parasitic resistance and inductance from bond wires, PCB trace, ferrite beads and long speaker leads from adversely affecting the fidelity of the audio signal. Furthermore, the external feedback pins allow the use of filter networks in the feedback path to customize sound without relying on DSP. In terms of features, the PAM8965 incorporates a 41-step (0.5dB per step) automatic gain control (AGC) system, which delivers smooth variations in audio channel gain when responding to the following conditions: Junction temperature exceeds +125°C (thermal foldback) Output power exceeds a set threshold based on PLIM pin voltage (non-clip power limit) Volume control based on the GAIN pin voltage The PAM8965 output can be driven in single-ended or in bridge-tied-load (BTL) configuration. Spread spectrum modulation (SSM) allows the use of inexpensive ferrite bead filters and yet meet EMI specification. Although boost switching frequency (768kHz) is twice that of Class-D PWM frequency (384kHz), nevertheless, the spread added on both systems due to SSM is synchronized. This ensures audible beats are not generated due to difference in switching frequencies. The start-up time, defined as the time between EN asserted and audible output from the speakers, is only 15ms. This includes the boost converter start-up and audio channel wake-up along with the pre-charge of the DC-blocking capacitors at audio Inputs. The advantage of this fast start is that the device does not require mute control. The device can be enabled when audio output is required, and disabled when audio output is off, consuming only 0.7μA in the off state. The PAM8965 has a multitude of protection features, which include under-voltage and over-voltage lock out on VBAT, over-voltage lock out on PVDD, short circuit protection on all audio outputs, cycle-by-cycle current limit on the boost converter, thermal shutdown of the entire system, speaker protection against DC audio, and an FLT pin that provides a fault flag. PAM8965 10 of 25 May 2021 Document number: DS42707 Rev. 2 - 2
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