The FM809, FM810 and FM1233 supervisory ICs from Fairchild Semiconductor International feature a precision comparator and a reset generator to ensure proper functioning of microcontroller- and microprocessor-based systems by monitoring the supply line (VCC). These devices are designed to monitor power supplies and other system voltages to generate a reset output when the voltage being monitored is out-of-tolerance. Fairchildıs new supervisory ICs consume typically 2 µA. Due to this low active current consumption, they are appropriate for battery-based applications.

These products represent three families having reset threshold voltages in the 2.63V to 4.63V range to accommodate various system voltages viz. 5.0V, 3.3V, 3.0V and 2.7V. In addition, the FM1233 family features bi-directional reset support with on chip de-bounce circuit. This feature allows a push-button to be directly connected to its reset output, to manually generate a reset without adding logic or extra pins.

The FM809 and FM1223 feature an active low reset polarity while the FM810 features an active high reset polarity. The reset output of both FM809 and FM810 is of "Push-Pull" type while the reset output of FM1233 is of "Open-Drain" type. With all three products, when the supply voltage (VCC) is out-of-tolerance, the reset line of the IC is driven to its active state and is held there until VCC returns to an in-tolerance state and the time for the reset pulse has expired. The standard offering has reset pulse duration of 256ms, but other reset pulse choices from 32 to 128 ms are available upon request. Customers are also able to order products with custom voltage threshold settings.

At first glance this trio of products could be considered a me-too introduction similar to several other well-known semiconductor manufacturers. They offer a strict voltage control comparator and reset capability, with active high or active low reset, and a selection of voltage reset delays from 32 ms to 256 ms with the factory standard of 256 ms. But upon closer inspection you discover that this supervisory IC consumes only 2 microamps compared with the 6 to as much as 45 microamps used by competing designs. That could be significant if you are placing the chip into cell phones that need to squeeze every bit of juice out of the battery. Typical applications include microcontrollers, microprocessors, DVD players, automotive systems, portable equipment, and cell phones.

The company covered the bases with the three offerings with circuits initiated by active low reset (FM809 and FM1233) or active high reset (FM810). The circuits monitor power supply or other system voltages and issue reset pulses when a fault condition exists. The FM1233 also offers an external reset switch to be wired to the reset pin. It allows an external reset pin to be connected without having to add debounce logic or an extra pin to the package.

The FM1233 detects when an external source is pulling the reset line low. Once this occurs, the FM1233 will pull the reset line low. When the external source stops driving the reset line, the FM1233 continues to hold the reset line low to prevent debounce.

All three devices are available in SOT-23 packages, and each has an operating temperature range of -40º C to 105º C. Other package options such as SOT-223 and SC-70 will be available soon.

Price: US$0.49 (1,000 pcs) FM1233
US$0.39 (1,000 pcs) FM809/810
Samples and production quantities are available now; delivery is 2-4 weeks ARO