The TPS3705, TPS3707 family of microprocessor supply-voltage supervisors provide circuit initialization and timing supervision, primarily for DSP and processor-based systems.

During power-on, RESET\ is asserted when the supply voltage VDD becomes higher than 1.1 V. Thereafter, the supply voltage supervisor monitors VDD and keeps RESET\ active as long as VDD remains below the threshold voltage VIT+. An internal timer delays the return of the output to the inactive state (high) to ensure proper system reset. The delay time, tdtyp = 200 ms, starts after VDD has risen above the threshold voltage VIT+. When the supply voltage drops below the threshold voltage VIT–, the output becomes active (low) again. No external components are required. All the devices of this family have a fixed-sense threshold voltage VIT– set by an internal voltage divider.

The TPS3705-xx and TPS3707-xx devices incorporate a manual reset input, MR\. A low level at MR\ causes RESET\ to become active.

The TPS370x-xx families integrate a power-fail comparator which can be used for low-battery detection, power-fail warning, or for monitoring a power supply other than the main supply.

The TPS3705-xx devices have a watchdog timer that is periodically triggered by a positive or negative transition at WDI. When the supervising system fails to retrigger the watchdog circuit within the time-out interval, tt(out) = 1.6 s, WDO\ becomes active. This event also reinitializes the watchdog timer. Leaving WDI unconnected disables the watchdog.

The TPS3707-xx devices do not have the Watchdog function, but include a high-level output RESET.

The product spectrum is designed for supply voltages of 2.5 V, 3 V, 3.3 V, and 5 V. The circuits are available in either 8-pin MSOP or standard SOIC packages. The TPS3705, TPS3707 devices are characterized for operation over a temperature range of –40°C to 85°C.

• Power-On Reset Generator with Fixed Delay Time of 200 ms, no External Capacitor Needed
• Precision Supply Voltage Monitor 2.5 V, 3 V, 3.3 V, and 5 V
• Pin-For-Pin Compatible with the MAX705 through MAX708 Series
• Integrated Watchdog Timer (TPS3705 only)
• Voltage Monitor for Power-Fail or Low-Battery Warning
• Maximum Supply Current of 50 µA
• MSOP-8 and SO-8 Packages
• Temperature Range . . . –40°C to 85°C

typical applications

• Designs Using DSPs, Microcontrollers or Microprocessors
• Industrial Equipment
• Programmable Controls
• Automotive Systems
• Portable/Battery Powered Equipment
• Intelligent Instruments
• Wireless Communication Systems
• Notebook/Desktop Computers