audio/videoZONE Products for the week of July 19, 2010
Cirrus Logic Says…
CS4354: Audio DAC Focuses on Lowering System Costs, Reducing Components
On-Chip 2 Vrms Line Driver from 5-V Power Supply Improves Audio Quality
Cirrus Logic Inc., has introduced the CS4354, its lowest-cost 24-bit digital-to-analog converter (DAC) with integrated stereo line drivers. Targeting consumer home audio applications, such as video game consoles, Blu-ray Disc and DVD systems, TVs, set-top boxes and digital media players, the CS4354 is Cirrus Logic’s fourth-generation audio DAC with ground-centered 2VRMS line drivers. The CS4354 marks significant progress in simplifying the design of analog output circuitry by reducing the need for multiple system components, which saves system cost and board space.
The CS4354 utilizes an on-chip charge pump to generate a negative supply and outputs a ground-centered, 2VRMS filtered line level signal from a single 5 V supply. This architecture provides improved low-frequency response and audio quality and offers significant savings in external component costs by eliminating DC blocking capacitors, mute and pop suppression circuits and the need for an expensive high voltage power supply.
“The CS4354 has 40 percent fewer pins and requires six fewer external capacitors than our third generation DAC in this product category,” said Carl Alberty, director of Marketing, Cirrus Logic’s Mixed Signal Audio Division. “We are excited to be delivering smaller and more cost effective DAC solutions to our customers without sacrificing the performance they have come to expect from Cirrus audio products.”
The CS4354 is a stereo DAC with ground-centered line level audio outputs. The architecture includes the level shifting from an I2C serial audio input, the digital interpolation filters, a multibit delta-sigma modulator, and the DAC itself. Digital de-emphasis is included as well as analog filtering and the audio line drivers. Conversion is up to 24 bits and at audio sampling rates up to 192 kHz.
The supply for the analog sections of the part is 5 V and an on-chip regulator produces 1.8 V for the digital sections. A separate 1.8 V to 5 V is required for the digital interface. Total power dissipation is a typical 50 mW for normal operation and 2.5 mW in power-down mode.
The typical dynamic range of the converter is 101 dB (24 bit, A-weighted) and 96 dB at 16 bits. THD N is typically -86 dB at 0 dB (24 bit) falling to -38 dB at -60 dB. There is about 100 dB of separation between the two channels.
The interchannel gain mismatch of the CS4354 is 0.1 dB with a gain drift of 100ppm/ºC. The load impedance is a minimum of 3 kΩ paralleled with a maximum of 100 pF. The combined digital and analog filtering shows a ±0.05 dB frequency response over 20 Hz to 20 kHz while the stopband attenuation is a minimum of 80 dB at 48 kHz sampling, 82 dB at 96 kHz, and 85 dB at 192 kHz.
It is really good to see Cirrus pulling ahead in this sort of line level application. The use of an inverting charge pump to provide a negative rail for minimal audio gain distortion is hardly novel but this seems to be a good implementation – allowing for the avoidance of dc blocking capacitors that also compromise low frequency audio performance – and for the provision of full-scale 2 Vrms outputs with a 5 V rail. The part produces differential linearity with low distortion and a minimal external component count. Pricing is extremely competitive and the Pb-free package is one that just about every OEM will find easy to accommodate in production. The CS4354 will be extremely successful.
The CS4354 is in production in SOIC-14 priced at $0.81 in 10-k piece lots.