Analog switch focus: cell phone features spur demand for analog switches

This has been a big year for the analog switch market, which has seen demand leap forward as the replacement of discrete components in cell phones accelerated. Such vendors as Analog Devices, Fairchild Semiconductor, Maxim Integrated Products, Siliconix and Texas Instruments have been churning out new switches in response to the feature-hungry demands of the cell phone market.

Analog switch sales will climb from $250 million worldwide this year, to more than $300 million in 2007. Communications, which includes cell phones, will account for roughly 31% of total 2007 switch sales, according to Databeans Inc. (Reno, Nev.)

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Databeans' Analog Switch Forecast

Demand for switches is growing in the cell phone space because it replaces discretes, reduces chip count, and lowers cost in more advanced designs, said Databeans senior analyst Susie Inouye. “It's not so much new cell phone subscribers that will drive growth here, but rather the demand for higher voltage functionality, such as sophisticated ringtones, cameras, MP3 audio, etc.”

“This is a very hot market. The mobile phone market is growing fast, both in emerging markets and in terms of handset turns (upgrades) in mature markets like Europe, U.S. and Japan,” said Liam O'Suilleabhain, product marketing manager for switches and multiplexers, Analog Devices Inc. (Norwood, Mass.)

A key driver in the upgrade cycle is the addition of more features in the handset. OEMs and own design manufacturers (ODMs) are using analog switches in order to integrate features quickly and inexpensively, O'Suilleabhain said. “This allows innovation and experimentation without having to incur costly and time consuming chipset revisions and reduces development risk by allowing handset manufacturers to add or drop unwanted features quickly,” he said.

Another important function of these switches is to keep the cell phone battery from burning out. “Analog switches enable you to switch from one feature to another. If each feature were used simultaneously, the cell phone battery would last for about an hour,” said Jerry Johnston, Fairchild Semiconductor Corp.'s Integrated Circuit Group manager of analog switch products (South Portland, Maine).

The development of very low R(ON) switches on low geometry CMOS processes is being driven by audio switching requirements for very low variation in on resistance R(ON) to minimize distortion effects.

Right now, the generally accepted industry performance for low-ohm switching applications such as stereo audio switching is an R(ON) lower than 0.5 ohms. However, in the next year or so, 0.2-ohm [max.] R(ON) performance will become more prevalent, Johnston said.

“A switch needs to be as transparent as possible to the signal — low insertion loss and wide bandwidth are key. Low R(ON) flatness is essential for excellent total harmonic distortion (THD) so that there is no signal distortion, which is important for audio applications,” Johnston added.

Texas Instruments Inc. (Dallas, Texas) hopes to make audio routing easy with a 1-ohm single pole, double throw (SPDT) analog switch. This high-fidelity switch, dubbed the TS5A3159, is intended for audio routing applications, due to its low THD (0.01%) and very low crosstalk (-65 dB).

The convergence of mobile devices such as handsets, PDA's, and portable music players has increased the demand for high performance analog switches that can route audio signals from a variety of sources — audio codec, FM tuner, MP3 playback from a DSP, or a polyphonic ring tone generator. The low 1-ohm R(ON) of the TS5A3159 SPDT reduces insertion loss when compared to popular 10-ohm “3157” single pole, double throws (SPDT)'s in the market.

Additionally, its 0.15-ohm R(ON) flatness allows it to achieve a low total harmonic distortion of 0.01% under rail-to-rail signal conditions, making it a versatile option for selecting between sources upstream of the audio power amplifier, or for routing between an internal speaker or external headset downstream of the audio power amplifier.

The TS5A3159 is offered in standard 6-pin leadframe packages, SC-70 (DCK) and SOT-23 (DBV) for space-constrained portable applications such as cell phones, and other portable products. The TS5A3159DBVR and TS5A3159DCKR are currently available to sample. Budgetary pricing for the devices is set at 68 cents in quantities of 1,000. Production quantities are planned for December/January.

Click here for more technical information on TI’s TS5A3159 analog switch.

Fairchild Semiconductor is addressing low distortion requirements with its normally closed (NC), SPDT FSA2257 switch, which offers low THD (0.002%) and exceptional ESD protection (8.0 kV), according to the company. Other features include a broad operating voltage range (1.65 to 5.5 V), low leakage current (2 nA) and low charge injection (20 picocoulomb) max. This low R(ON) (0.95-ohm typical) analog switch supports strong growth in cell phones, digital still cameras, PDAs, medical electronics, industrial instrumentation, and other portable products. Fairchild's FSA2257 provides bi-directional operation, allowing configuration either as a multiplexer or demultiplexer by select pins.

“The dual SPDT configuration of this device allows ultra-portable designers flexibility in routing the audio signals, such as speaker sharing or hands-free function implementation,” Johnston said.

Fairchild's FSA2257 comes in ten-terminal leadless MicroPak (L10X suffix) packaging on 5000-piece tape-and-reels. Pricing is 75 cents each in 1,000-piece quantities with delivery in four weeks ARO.

Click here for technical information on the FSA2257, including a data sheet.

Reducing R(ON) while driving smaller package sizes requires some advanced switch design techniques. Parts like Analog Devices Inc.'s ADG849 offer new levels of performance in a tiny package that was not deemed possible a few years ago, O'Suilleabhain said. This innovation maintains the drive towards better audio performance in a tighter printed-circuit board space for those manufacturers who wish to keep using the more reliable standard plastic packages. Smaller geometry CMOS processes will help maintain the lowest R(ON) in the smallest packages, albeit at a lower supply voltage rail.

The ADG849 is the industry's first SPDT 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 a practical 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 R(ON) to <1 ohm, with THD of 0.02% at 25°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.

The ADG849 is intended for use in 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.

The ADG849 is housed in a 6-lead SC70 package. Pricing per unit in 1,000-piece quantities is 94 cents.

Click here for the ADG849 data sheet.

In March, Siliconix Inc., (Santa Clara, Calif.), an 80.4%-owned subsidiary of Vishay Intertechnology Inc. (Malvern, Pa.), launched an analog switch and multiplexer packaged in the 3-mm by 3-mm QFN-12 package aimed at 1.8 to 5.5-V handheld battery-operated portable applications.

The new DG2032 dual SPDT analog switch and DG2034 4:1 multiplexer are the first products in the QFN-12 to combine low 3-ohm R(ON), low power consumption, and superior switch performance while operating over a wide power supply and analog signal range.

These parts cater to the needs of both audio and higher-speed analog signal switching for port sharing/extension, data acquisition, PCMCIA, audio/video signal routing, speaker/headset switching, and similar applications in end products such as cell phones, digital cameras, PDAs, MP3 players, and handheld test and health care equipment.

The DG2032 dual SPDT analog switch features a low R(ON) specification of 3 ohms at 2.7 V, with wide dynamic performance better than -80 dB for both crosstalk and off-isolation at 1 MHz. With its fast switching speeds (25-ns turn-on, 13-ns turn-off), high bandwidth, and low charge injection, the DG2032 is suited for switching a wide range of audio and video signals.

The DG2034 4:1 analog multiplexer offers low R(ON) of 4 ohms and off-isolation and crosstalk of -55 dB at 10 MHz. In addition to the QFN-12, the DG2034 is also available in the MSOP-10 package.

The DG2032 and DG2034 are available now with lead times of six to eight weeks for larger orders. Pricing in 10,000-piece quantities is 60 cents for the DG2032 and 70 cents for the DG2034.

Click here for the DG2032 data sheet.

Click here for the DG2034 data sheet.

The MAX4754 and MAX4758 low voltage quad/octal SPDT analog switches are the
industry's smallest analog switches that operate from 1.8 V to 5.5 V, according to Maxim (Sunnyvale, Calif). The MAX4754 is available in 2mm x 2mm 16-UCSP, and the MAX4758 is available in 3mm x 3mm 36-UCSP. The MAX4754 features 0.5-ohm R(ON) and 0.2-ohm R(ON) flatness. The MAX4758 features 0.5-ohm R(ON) and 0.2-ohm R(ON) flatness. The 0.5-ohm R(ON) switches are ideal for switching audio signals (20 Hz to 20 kHz) in cell phones.
These switches are based on the MAX4684 dual SPDT analog switch with 0.3 ohm/0.45 ohm R(ON) that set the trend for this market, said David Nam, Maxim's business manager. The MAX4684 is available in the 2mm x 1.5mm 12-UCSP.

Maxim's MAX4754, MAX4758, MAX4684 switches sell for $1.18, $2.04 and 94 cents each, respectively, in 25,000-piece quantities.

Click here for the MAX4754 data sheet.

Click here for the MAX4762 data sheet.

Click here for the MAX4850 data sheet.

Company Contacts:

Analog Devices Inc.

Call: 1-800-Analog-D

Fairchild Semiconductor Corp.

Call: (207) 775-4599 (Jerry Johnston)

Maxim Integrated Products Inc.

Call: 1-800-998-8800

Texas Instruments, Inc.

Call: (972) 644-5580

Vishay Intertechnology Inc./Siliconix Inc., an 80.4%-owned subsidiary of Vishay.

Call: (1) 619-336-0860

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