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Digital BTSC encoder delivers alignment-free encoding

Tokyo, Japan — Asahi Kasei EMD Corp. (AKEMD) has expanded its Audio4home family with the launch of its AK4145, an integrated alignment-free digital BTSC stereo encoder for television markets including the United States, Canada, Mexico, Brazil and Taiwan. The device targets BTSC applications including digital set-top boxes, digital video recorders, and RF modulator converter boxes.

The AK4145, packaged in a 16-pin TSSOP, enables stereo audio transmission over the same RF signal that is used for cable and antenna inputs. AKEMD's new digital BTSC encoding process achieves high audio performance without alignment of external components. Audio characteristics include 0.01% S/(N+D), 82 dB SNR, and 47 dB stereo separation.

The AK4145 outputs digital PCM data as a baseband composite (MPX) audio signal, which includes L+R, L-R, and a Pilot signal by BTSC encoding. It supports video/27-MHz input for synchronization of the Pilot signal and video system signals.

Additional integrated functions such as soft mute, digital volume control and de-emphasis allow for a constant signal level setting corresponding to the audio source, and the composite output level can be adjusted by the baseband composite volume control.

The AK4145 audio data interface supports MSB-first, LSB-first or I2S formats. The master clock supports 256 fs, 384 fs, 512 fs and externally supplied 768 fs, which are typical frequencies for digital audio equipment. The sampling rate can be 32 kHz, 44.1 kHz or 48 kHz, making it possible to use the AK4145 in the same system configuration as existing audio DAC products. The operating voltage range for the digital section is 1.7 V to 1.9 V, and 2.7 V to 3.6 V for the analog and interface sections.

Availability: Evaluation boards and samples are available now.
Product information: AK4145

Asahi Kasei EMD Corp. , www.asahi-kasei.co.jp/asahi/en/emd

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