3V Voltage Monitoring, Low-Cost, µP Supervisory Circuits

The MAX706P/R/S/T, MAX706AP/AR/AS/AT, and MAX708R/S/T microprocessor (µP) supervisory circuits reduce the complexity and number of components required to monitor +3V power-supply levels in +3V to +5V µP systems. These devices significantly improve system reliability and accuracy compared to separate ICs or discrete components.

The MAX706P/R/S/T and MAX706AP/AR/AS/AT supervisory circuits provide the following four functions:

1) A reset output during power-up, power-down, and brownout conditions.

2) An independent watchdog output that goes low if the watchdog input has not been toggled within 1.6s.

3) A 1.25V threshold detector for power-fail warning, low-battery detection, or for monitoring a power supply other than the main supply.

4) An active-low, manual-reset input.

The only difference between the MAX706R/AR, MAX706S/AS, and MAX706T/AT is the reset-threshold voltage levels, which are 2.63V, 2.93V, and 3.08V, respectively. All have active-low reset output signals. The MAX706P/AP are identical to the MAX706R/AR, except the reset output signal is active-high. The watchdog timer function for the MAX706AP/AR/AS/AT disables when the WDI input is left open or connected to a high-impedance state of a low-leakage tri-state output.

The MAX708R/S/T provide the same functions as the MAX706R/S/T and MAX706AR/AS/AT except they do not have a watchdog timer. Instead, they provide both active-low RESET and RESET outputs. As with the MAX706, devices with R, S, and T suffixes have reset thresholds of 2.63V, 2.93V, and 3.08V, respectively.

These devices are available in 8-pin SO, DIP, and µMAX® packages and are fully specified over the operating temperature range.

Applications

* Battery-Powered Equipment * Computers * Controllers * Critical µP Power Monitoring * Intelligent Instruments * Portable Instruments

* µMAX Package, Small 8-Pin SO

* Precision Supply-Voltage Monitors

* 2.63V (MAX706P/R, MAX706AP/AR, and MAX708R)

* 2.93V (MAX706S, MAX706AS, and MAX708S)

* 3.08V (MAX706T, MAX706AT, and MAX708T)

* 200ms Reset Time Delay

* Debounced TTL/CMOS-Compatible Manual Reset Input

* 100µA Quiescent Current

* WDI Disable Feature (MAX706AP/AR/AS/AT)

* Watchdog Timer: 1.6s Timeout

* Reset Output Signal:

* Active-High Only (MAX706P, MAX706AP)

* Active-Low Only (MAX706R/S/T, MAX706AR/AS/AT)

* Active-High and Active-Low (MAX708R/S/T)

* Voltage Monitor for Power-Fail or Low-Battery Warning

* 8-Pin Surface-Mount Package

* Guaranteed active-low RESET Assertion to VCC = 1V