TLC7725 Voltage Supervisor

Expanding its technology leadership in the analog market, Texas Instruments announces the industry's first 2.5V supply voltage supervisor. This device, which operates from only 16 micro-amps of supply current, will enable more advanced DSP-based systems, such as cellular telephones, and a variety of other battery-powered systems. Additionally, it is ideal in microprocessor-based systems like laptop personal computers, personal digital assistants (PDAs), computer games, and test and measurement applications.

"The trend to 2.5 volt systems is certainly one that we see emerging in the industry," said Bob Newton, TI's analog product specialist. "We were able to leverage TI's DSP design expertise to understand the needs of DSP systems as they move to 2.5 volts and develop a part that will meet these requirements. The trend to lower operating voltages is a natural one for DSPs, as well as logic functions, because it enables higher component densities and faster speeds. This is the first supply voltage supervisor designed specifically to enable supply line supervision and processor reset control for the new 2.5V operating level."

The device, which is designated the TLC7725, monitors and controls power supply lines during both power-up and power-down. On power-up, the TLC7725 issues a reset condition to the system's processor when the supply voltage reaches 1V. Once the voltage rises to the device's sense threshold of 2.5V, the TLC7725 initiates a programmable time-delay before the reset output returns to the inactive state and the system's processor is turned on. The time-delay is programmed by means of an external capacitor and ensures that the supply voltage has stabilized before the system reset is removed. When power is removed from the system, for whatever reason, the TLC7725 issues a reset condition to the system's processor when the voltage drops below the 2.5V sense threshold. This reset condition remains in effect until the voltage rises above the sense threshold and the programmable time-delay has expired.

The TLC7725 offers precise control of supply voltages to within 3.1 percent of the sense threshold of 2.5V and it operates on as little as 16 micro-amps of power. The device reduces the system's power consumption and saves board space by including totem pole outputs which eliminate the need for external pull-up or pull-down resistors. The TLC7725 can also be used to automatically disable static memory with battery backup in the event of a power loss.

The TLC7725 joins TI's family of supply voltage supervisors, which includes options for 5V, 3.3V, 3V and an adjustable voltage device.

This is a no-brainer in terms of "it had to happen" but it is a considerable surprise to me that the first 2.5-V supervisor would come from TI. That's certainly not a problem but it is a further sign that the incidentals of the DSP business are, now, on equal footing of importance as the DSPs themselves.

The part contains all the functionality expected of a line supervisor and processor reset, with tight controls, making the part ideal for DSP deployment; the power dissipation is impressive and the avoidance of external pull-up or pull-down resistors is a nice touch. The TLC7725 is also priced right.

A much-needed part timed well for market conditions, the TLC7725 is fabricated in TI's LinBICMOS process and is available now. The part is manufactured in 8-pin TSSOP, 8-pin SOIC and plastic 8-pin DIP at $0.75 in 1000 piece lots.