California Micro Devices Launches microSD Interface Protection Filter For Mobile Handsets
California Micro Devices announced the CM1624, an application specific microSD (micro Secure Digital) interface protection filter for mobile and computing devices. The popular microSD flash memory card is increasingly used in portable devices to allow users to store or use data across different devices.
The CM1624 protects the microSD memory card user interface against ESD (electrostatic discharge) damage to the card or to the hardware and suppresses EMI (electromagnetic interference) while providing excellent digital signal integrity. It is a member of the leading edge Praetorian III® product line and is said to combine outstanding filter performance with minimal line capacitance. The CM1624 also features integrated pull-up resistors, eliminating the need for additional circuitry on the handset PCB (printed circuit board) and saving additional bill of materials cost.
Inductor based filter solutions offer the highest level of digital signal integrity available. The CM1624 can support clock frequencies up to 96 MHz, rise/fall times as fast at 5 nSec, and high levels of attenuation from 700 MHz to 3 GHz. The CM1624 pinout is optimized for the microSD interface standard and features 6 lines of EMI suppression with IEC 61000-4-2 +/-15kV (contact) integrated ESD protection, one line of through package ESD protection for the Vcc line, and two additional discrete ESD diodes for related functions such as Card Detect. Additionally, CMD has integrated 25k ohms pull-up resistors to help detect the presence of the memory card.
As process geometries used in manufacturing baseband and applications processors migrate to increasingly smaller feature sizes, system operating voltages are also becoming lower so that the amount of capacitive loading on the data lines has become a major concern for handset designers. The microSD interface specification allows for a total capacitive loading budget of 40pF and traditional filter architectures consume too much of this tight design parameter. The CM1624 features a specification 0Vdc capacitance of 20pF, and less than 12 pF at operating voltage - the lowest level of capacitance available in EMI filters designed for the microSD interface. The lower filter line capacitance affords handset designers greater design latitude with respect to PCB routing and improved ease of design.
The CM1624-08DE is available in an industry standard, compact, RoHS compliant microDFN16 package. Samples and are available now and are priced at $0.16 each in quantities of 3000 units.
