Both the contrast and viewing angle of liquid crystal displays depend on the provision of a highly stable supply voltage, yet in phone-line powered telephones this is difficult to achieve because of the wide variations that occur in telephone line conditions. With the introduction of the TEA1114A Speech/Transmission IC, Philips Semiconductors provides a fully integrated solution to this problem - by incorporating a high-performance voltage stabilizer into this innovative new telephone IC. The TEA1114A's stabilized supply generator not only ensures consistent LCD performance, it is also capable of delivering more than enough current to drive Philips Semiconductors' latest generation of 3.3-volt telecom oriented TELX microcontrollers. Another new feature of the TEA1114A is a gain boost facility on the earpiece amplifier.

"The introduction of the TEA1114A indicates Philips Semiconductors' on-going commitment to producing ICs that continually improve telephone performance," said product marketing manager Muriel Gombaud. "Based around our world-beating speech/transmission circuit design, these ICs will further strengthen our number-one position in the telephone IC market," she added.

The output of this new IC's on-chip voltage stabilizer follows the line voltage up to 3.3 V, at which point it regulates the output voltage at this level for output currents as high as 3 mA. Continuous stabilization of the output under all normal ringing, dialling and speech transmission conditions eliminates LCD display disturbances and ensures continuous operation of connected microcontrollers and peripherals.

The speech/transmission circuit in the TEA1114A includes all the features for which Philips Semiconductors' telephone ICs have become famous. These include low line voltage modes that allow several telephones to be operated in parallel on the same line, automatic line-loss compensation, adjustable DC and AC set impedance and superior EMC performance. In addition, the TEA1114A features a variable gain earpiece amplifier with gain boost facilities, on-chip microphone and DTMF amplifiers, a muting input and automatic confidence tone insertion. On-chip default settings for all amplifier gains and voltage levels mean that very few external components are required in the majority of telephones.

A new era is literally opened up with this part . . . a new breed of phones for the home! We should start to see telephones produced really soon with LCDs but no connection from the phone to wall power. That will save the OEM a couple of bucks just there and enhance the ability of consumers to accept phones with LCD features. That the stabilizer can supply enough current to drive an on-board microcontroller opens up the range of such phones' features quite dramatically -- again for phones connected only by the telephone cord. At the same time the price of the TEA1114A is incredibly low.

Nothing has been taken away from this part compared with earlier versions from Philips, and the on-chip earpiece volume control is a welcome addition to further save external circuitry. This part will, I am sure, keep the company way ahead in the marketplace for some time. As far as I can tell from the specifications the part causes no problems to the telephone line being used for power: This is not, for example, just an effective 3.3-V zener junction slapped across the line!

The TEA1114A is manufactured in a bipolar process at Philips' facility in Caen, France, and is in either a 16-pin DIP or a 16-lead SOP. It is priced at $0.55 in 100,000-piece lots..