Out in Front

DACs, ADCs increase speed and resolution, cut power

Vendors of D/A and A/D converters are introducing devices with the higher speed and resolution and lower power requirements that communications and imaging applications require. The TTL-compatible SPT9712 and ECL-compatible SPT9713 high-speed DACs from Signal Processing Technologies provide conversions at rates as high as 100M words/sec with 12 bit-resolution and consume 600 mW. Applications include direct digital synthesis, high-speed imaging, and spread-spectrum communication systems, as well as test-and-measurement equipment. The multiplying bandwidth of the guaranteed-monotonic devices is 40 MHz, and their outputs settle in 8 nsec. Both are available in 28-lead DIPs and PLCCs and cost $29.50 (1000).

For 8-bit A/D conversion, the single-channel AD9057 and dual-channel AD9059 from Analog Devices convert as fast as 60M samples/sec with 120-MHz analog bandwidth. The single-channel A/D dissipates 250 mW (typical) from a 5V supply, and the corresponding figure for the dual-channel unit is 400 mW. In power-down mode, dissipation drops to less than 10 and 12 mW, respectively. The converters include an internal reference and interface to 5 and 3V logic. The $7.28 (1000) AD9057 comes in a 20-lead SSOP; the $11.88 AD9059 comes in a 28-lead SSOP.

If you need 10-bit resolution, the 80M-sample/sec TDA8762A and 50M-sample/sec TDA8763A A/D converters from Philips Semiconductors may be appropriate. The 80M-sample/sec device is TTL-compatible, and, when sampling a 4.43-MHz signal, it has a 9.3-bit effective number of bits, a 58-dB S/N ratio, and –68-dB THD; the corresponding figures are almost the same for the CMOS-compatible, 50M-sample/sec converter when it samples at 40M samples/sec. The TDA8762A device dissipates 380 mW, and the TDA8763A device dissipates 195 mW from a 5V supply (although the CMOS converter operates as low as 2.75V). The devices come in 28-lead SSOPs and cost $120 and $30 (10,000), respectively.—by Bill Schweber

Signal Processing Technologies Inc, Colorado Springs, CO. (800) 643-3778, http://www.spt.com.

Analog Devices Inc, Norwood, MA. (800) 262-5643, http://www.analog.com.

Philips Semiconductors, Sunnyvale, CA. (800) 447-1500, ext 1318, http://www.semiconductors.philips.com/ps/.