The SSM2517 is a PDM digital input Class-D power amplifier
that offers higher performance than existing DAC plus Class-D
solutions. The SSM2517 is ideal for power sensitive applications,
such as mobile phones and portable media players, where system
noise can corrupt the small analog signal sent to the amplifier.
The SSM2517 combines an audio digital-to-analog converter
(DAC), a power amplifier, and a PDM digital interface on a single
chip. The integrated DAC plus analog Σ-Δ modulator architecture
enables extremely low real-world power consumption from
digital audio sources with excellent audio performance. Using
the SSM2517, audio can be transmitted digitally to the audio
amplifier, significantly reducing the effect of noise sources such as
GSM interference or other digital signals on the transmitted audio.
The SSM2517 is capable of delivering 2.4 W of continuous output
power with <1% THD + N driving a 4 Ω load from a 5.0 V supply.
The SSM2517 features a high efficiency, low noise modulation
scheme that requires no external LC output filters. The closed-loop,
three-level modulator design retains the benefits of an all-digital
amplifier, yet enables very good PSRR and audio performance. The
modulation continues to provide high efficiency even at low output
power and has an SNR of 96 dB. Spread-spectrum pulse density
modulation is used to provide lower EMI-radiated emissions
compared with other Class-D architectures.
The SSM2517 has a four-state gain and sample frequency selection
pin that can select two different gain settings, optimized for 3.6 V
and 5 V operation. This same pin also controls the internal digital
filtering and clocking, which can be set for 64 × fS or 128 × fS input
sample rates to support both 3 MHz and 6 MHz PDM clock rates.
The SSM2517 has a micropower shutdown mode with a typical
shutdown current of 1 μA for both power supplies. Shutdown is
enabled automatically by gating input clock and data signals. A
standby mode can be entered by applying a designated PDM stop
condition sequence. The device also includes pop-and-click suppression
circuitry. This suppression circuitry minimizes voltage
glitches at the output when entering or leaving the low power
state, reducing audible noises on activation and deactivation.
The SSM2517 is specified over the industrial temperature range
of −40°C to +85°C. It has built-in thermal shutdown and output
short-circuit protection. It is available in a 9-ball, 1.5 mm × 1.5 mm
wafer level chip scale package (WLCSP).
Applications
