Spread spectrum oscillator slashes EMI

It offers customers a drop-in replacement for standard clock oscillators with a reduction in electromagnetic interference (EMI) by as much as 12dB.

In electronic systems a principal cause of EMI is the system clock oscillator and traditional “patching-up” methods of combatting interference – ferrite beads, ground planes, metal shielding and similar – are frequently costly and awkward to implement and most often applied after a system has failed EMI testing.

The most efficient method to reduce EMI is to suppress it at source and that’s where Euroquartz’s new EQHM22 intervenes.

Compared with conventional clock oscillators, spread spectrum (dithered) oscillators can reduce EMI by up to 12dB and the parts are drop-in replacements for standard components so there is no requirement to redesign existing PCBs.

Offering a choice of modulation rates and spreads, these new devices offer frequencies from 16 to 40MHz in a miniature surface mount package measuring 2.5 x 2.0 x 0.9mm. Frequency stability is available as low as ±25ppm in both commercial (0 to 70°C) and industrial (-40 to +85°C) grades with input voltages of 1.8, 2.5 and 3.3V DC available, all ±10%. Output logic is CMOS with load capability of 15pF.

Additional specifications include current consumption of 4, 5 or 6mA depending on voltage model, rise/fall times from 7ns to 10ns, start up time of 1ms typical, 5ms maximum, output enable/disable function and duty cycle of 50% ±10%. Ageing is ±5ppm/year maximum at 25°C ambient temperature.

These low EMI oscillators are ideal for use in a wide range of applications including printers and multifunction printers, digital copiers, PDAs, networking LAN/WAN and routers, storage systems such as CD-ROM, DVD and HDD, scanners, modems, projectors, embedded systems, automotive GPS navigation systems, LCD PC monitors and TVs, ADSL, PCMCIA devices and digital cameras.