1998-10-05 , E/IC-1042/54
Product News From Philips Semiconductors

Although Lithium Ion (Li-ion) batteries provide the high energy densities required to power the latest generation of mobile phones, they are far from ideal in terms of unit cost and safety. A unique new DC/DC converter chip from Philips Semiconductors, Europe's largest semiconductor manufacturer, allows designers to replace a Li-ion battery by two AAA-sized Nickel-Cadmium (NiCd) or Nickel-Metal-Hydride (NiMH) cells - reducing unit costs and increasing safety without adversely affecting the phone's size, weight or performance. The TEA1210, which is being introduced at Power '98 (October 4-6, Santa Clara, USA), delivers pulsed output powers as high as 14 W from a 16-lead SSOP package, making it the world's smallest DC/DC converter in its class.

"GSM phones have got locked in to using Li-ion batteries," said Leo Warmerdam, Philips Semiconductors' product marketing manager for DC/DC converter ICs, "The TEA1210 now frees designers to cut battery pack costs by well over 60%, while at the same time eliminating the safety hazards of Lithium battery technology." "Even when you factor in the cost of the DC/DC converter circuitry, overall savings still amount to around 40%," he added.

In common with other members of Philips Semiconductors' highly successful TEA12xx family of DC/DC converter ICs, the TEA1210 utilises the company's proprietary digital pulse-width/pulse-frequency modulation techniques to maintain a very high DC/DC conversion efficiency and excellent dynamic performance for all load currents. In addition, this new IC features a unique 2-level current limit that is specifically designed to drive the pulsed RF power amplifier of a GSM phone. When the power amplifier is on, it is driven by the high current output of the TEA1210 plus the charge stored in an external capacitor. When the amplifier is turned off, the TEA1210 can be switched to its lower current limit in order to re-charge the capacitor ready for the next RF burst. By switching between the high and low current limits, the TEA1210 operates at maximum efficiently during both periods.

Boosting the voltage from two NiCd cells (2.4 V) to drive a GSM phone's 3.6-volt RF power amplifier at its 8:1 duty cycle, and using only a 660 nF capacitor to boost the load current, the TEA1210 achieves a typical conversion efficiency of 93%. Even when the battery pack approaches complete discharge (1.8 V), conversion efficiency only falls to 83%.

Because of the TEA1210's high conversion efficiency under all load conditions (from less than 1 mA to more than 1.5 A ), designers have the option of powering the entire phone from its output, without significantly impairing standby or talk times. Other features, such as clock synchronisation, under-voltage lock-out and shut-down modes make the TEA1210 particularly suitable for use in mobile phones. In particular, the ability to move from a Li-ion battery to just two AAA-sized cells means that battery packs can be made even smaller than they are today. As an added bonus, mobile phone users will be able to fit two standard alkaline batteries into their phones to power them in an emergency.