audio/videoZONE Products for the week of March 8, 2004
Analog Devices Says . . .
ADG849: Low-Resistance Analog Switch Optimized For
Audio In Handsets
Analog Devices guarantees <1 Ohm resistance at 5 V in SC-70
About the ADG849
Analog Devices' new high-performance analog switch is optimized to provide
best-of class audio switch quality in today's popular handset and multimedia
portable designs that require higher voltage supplies to support media-rich
features, such as musical ringing tones and color screens. The new part--the
ADG849BKS--joins ADI's ADG8XX family of <1 Ohm Ron (on-resistance) switches
and multiplexers.
The ADG849 is the industry's first SPDT (single-pole, double-throw) switch in an SC70 package to feature <1 Ohm resistance at 5.5 V-supply. The ADG849 minimizes distortion on audio signals up to 5.5 V, making it an ideal solution for new handset designs that require higher voltage supplies to support polyphonic (musical) ringing tones, and other multimedia features, such as color screens and graphics. The switch reduces Ron (on-resistance) to <1 ohm, with total harmonic distortion of 0.02 percent at 25 degrees C. It has a wide operating range of +1.8 V to 5.5 V, providing significant performance advantages over other switching solutions in SC70 packaging.
Applications
The ADG849 is ideally suited for space-constrained applications that require
minimal distortion through the switch, including cell phones, PDAs, battery-powered
systems, audio and video signal routing, modems, PCMCIA cards, hard drives
and relay replacement.
analogZONE Says...
There is one other SPDT switch on the market in a SC-70-6 and it offers a 1.3 Ohm (full temperature range) on-resistance (at 4.5 V) at a budgetary price of less than half what Analog Devices is looking for here with the ADG849. Many users will look at the 0.8 Ohm maximum (at 5 V, full temperature range) of the ADI part and say, "yes" because it still represents a reduction of 62.5% in on-resistance, significant when you are chasing every dB of signal you can get.
The Analog Devices' data sheet is not ready for prime time, but the specification for a rail of between 2.7 V and 3.6 V -- a much more likely range for the applications of the switch -- show a maximum on-resistance of 1.6 Ohm, whereas the competition shows 4.3 Ohm and the difference has now increased to 169%, even more significant than the higher-rail performance.
With the lower rail voltages, where the parts will be used, off-isolation is good at -71 dB and crosstalk (ADI says "channel-to-channel"?) is -72 dB. The THD (no frequency quoted) is 0.02% , probably high because the on- and off-capacitances are very high at 300 pF and 80 pF, respectively and both typical. The 3-dB bandwidth is also a disappointing 17 MHz, rather limiting its use for video signals. It should be noted, however, that the part can handle up to 600 mA and the contacts are break-before-make.
With audio, however, which I think was its targeted design application, the numbers on the ADG849 are all very right for portable switching -- or muxing -- applications and there's nothing to hate in a maximum power consumption of just 1.0 µA.
The ADG849 is sampling in SC-70-6 and will be priced at $0.94 in 1000-piece lots when it is in full production in Spring 2004.