Chips that combine better electromagnetic and radio frequency interference (EMI/RFI) filters with circuit-protection elements and line-termination componentry are squeezing more into less space for today's broad range of computing, mobile, wireless and general consumer devices.
New applications and functions usually mean designers must find room for larger numbers of discrete passives to provide advanced filtering and protection in next-generation products. With space and money at a premium, however, developers are migrating to the use of standard IC and chip-scale packages.
"In most all cases, it costs more to place a chip resistor on board than to buy it," said Shawn Wood, senior analyst at iSuppli Corp. (El Segundo, Calif.), referring to the overhead associated with discrete devices. "Six-and-a-half percent of the average finished electronic product is component placement cost, 55 percent of which is discrete passives. Integrated passives are coming especially for cell phones, PCs, set-top boxes and cable modems," he said.
By Woods' count, a typical cell phone currently houses about 495 passive units, 410 of which are discrete passives. Integrated passives represent only 17 percent of the total passives count, Wood said.
While power limitations ensure a future for competing integrated passive packages, interest in thin-film monolithic devices, vs. thick-film and modular integrated passives that bring discretes under one roof, remains high-despite a downturn in actual products that went to market last year. Most IC vendors with an integrated-passives program attribute that development to a lack of industry standardization. Nonetheless, products that actually make it to market demonstrate better filtering characteristics at higher frequencies, yet also provide as much as 30 kilovolts of electrostatic discharge (ESD) protection.
"Integrated passives-EMI, ESD and termination circuits-provide a virtually complete cost-effective solution," said Kyle Baker, vice president of California Micro Devices (Milpitas, Calif.), one of the most active developers in this area. "Integrated RC filters eliminate parasitic inductances and cover a broader frequency range in a smaller footprint. They also deliver the highest levels of ESD protection in a smaller footprint."
One major application is protecting liquid crystal displays (LCDs) found in wireless handsets. Semtech Corp. (Camarillo, Calif.) claims its SFC2309-200 is the industry's first such chip-scale type integrated protection array for color LCDs. The newest member of the company's ChipClamp family comes in a 2.6 x 2.6 x 0.65-mm flip-chip package that replaces up to 40 discrete components. The device uses a filter and two transient-voltage suppressors (TVSes) on each line to provide a minimum of 25 dB of EMI/RFI attenuation over 800 MHz to 3 GHz and 15 kV (air) of ESD protection (8 kV contact) for 10 signal lines.
Guarding data lines
California Micro Devices, using its newly developed Centurion technology for zener diodes, has just launched its CSPEMI608 as part of its application-specific integrated-passive family. The device is a low-capacitance EMI filter array with ESD protection for the LCD's data lines. The CSPEMI608, in a 20-bump chip-scale footprint measuring 4 x 1.46 mm, includes a pi-filter (15 pF, 100 ohms) for each of eight lines that provide 30-dB attenuation at 1 GHz and 40-dB attenuation at 3 GHz. Each line's output capacitance is about one-half that of competing solutions for this particular application, according to the company. Each filter section also includes plus/minus 15 kV ESD protection (zener diode at input and output) to meet the IEC61000-4-2 Level 4 spec. The company said this chip will cut board-space requirements by up to 90 percent compared with discrete parts solutions. The device is currently in sampling and will be available in September.
Earlier this year, California Micro Devices released the CM1214, its newest addition to the PicoGuard family of ultralow-capacitance ESD protection arrays. The company claims this device is the only ESD protection array with sub 1-pF ESD protection. The CM1214 features an input capacitance of 0.8 pF and an ESD rating of plus/minus 8 kV contact discharge for both ac and dc signal nodes in one- and two-channel apps suited to Gigabit Ethernet, multiband wireless handsets, power amps, and Bluetooth modules. It features a clamp voltage of 7 V, and is particularly applicable to typical RF ICs that are powered by a 5-V source. These devices, in 3-lead SOT-23 and 8-lead MSOPs, will tolerate multistrikes.
California Micro Devices earlier this year had released a device similar to the CM1214, but for use with the universal serial bus, USB 2.0. The CM1213 provides protection for up to 8 channels and in this application, matching is important: Channel capacitance in these devices is matched to within 0.2 pF, and channel-to-channel cross-coupling capacitance is 0.003 pF. Clamping voltage for these 9-V operating bus devices is less than 14 V.
Meanwhile, ON Semiconductor (Phoenix) has launched five new monolithic devices in its MicroIntegration series, three of which are for ESD protection and two of which are combination filter-with-TVS diodes for high-speed data ports-digital video interface (DVI), Ethernet and USB-in PCs. The combination filter-protection devices each replace 12 discrete components. Seven additional devices, of which two are integrated filter and line-protection devices, are expected shortly.
Elsewhere, Semtech has developed a device to provide surge protection for various high-speed interfaces, from 100 MHz to1 GHz and including DVI and high-definition multimedia interface. The RClamp0504M integrates four surge-rated low-capacitance steering diodes and an avalanche TVS diode to protect four high-speed I/O lines and the positive power rail. The TVS diode can be used to prevent an overvoltage condition on the positive power supply rail. The device, intended for use with a 5-V source, features a maximum line capacitance of 5 pF, 15-kV ESD protection and high surge capability (12 amps with 8/20 microsecond waveform characteristics). The device comes in a 10-lead MSOP.
In the consumer set-top area, California Micro Devices previously released its CM1209. Using a pair of diodes that steer ESD currents to the positive or negative supply rail, it provides plus/minus 15 kV contact and air ESD protection for 4, 6 or 8 channels. The device also includes a zener supply clamp and eliminates the need for an external capacitor. The device features low loading capacitance (6 pF typical), and a clamping voltage of 15 V with no higher trigger voltages. It also provides overload shutdown protection.
Integration, however, hasn't really caught on yet.
"Integrated passives aren't quite there, because there hasn't been as much standardization in this market," said Jim Somers, product-marketing manager for advanced passives at Bourns Inc. (Riverside, Calif.), reflecting industry consensus. "The company provides three product lines: thick film; standard thin-film ICs in QSOP type packages; and bare silicon on chip-scale packages. We have to focus on devices that provide a standard function, rather than being customer specific. The designer has to make a choice; with the short lifetimes of a typical handset, custom may not be worthwhile."
Bourns, which previously has released such products as the 2DTF and 2DTG terminator/filters with ESD protection in a QSOP package for the IEEE 1284 spec, has more recently begun to offer seven- and 12-line ESD products in chip-scale packages.
In addition, Bourns has just launched its 2FAD-C20R, a 4 x 5-array, 20-bump device measuring 2.04mm x 2.64 mm. It contains six EMI filters with zener diodes for ESD protection.
California Micro Devices