The MAX696/MAX6971AUG supervisory circuits reduce the complexity and number of components required for power-supply monitoring and battery-control functions in microprocessor (μP) systems. These include μP reset and backup-battery switchover, watchdog timer, CMOS RAM write protection, and power-failure warning. The MAX696/MAX6971AUG significantly improve system reliability and accuracy compared to that obtained with separate ICs or discrete components. The MAX696 and MAX6971AUG are supplied in 16-pin packages and perform six functions:
A reset output during power-up, power-down, and brownout conditions. The threshold for this "lowline" reset is adjustable by an external voltage-divider.
A reset pulse if the optional watchdog timer has not been toggled within a specified time.
Individual outputs for low-line and watchdog fault conditions.
The reset time may be left at its default value of 50ms, or may be varied with an external capacitor or clock pulses.
A separate 1.3V threshold detector for power-fail warning, low-battery detection, or to monitor a power supply other than VCC. The MAX696 also has battery-backup switching for CMOS RAM, CMOS microprocessor, or other low-power logic. The MAX6971AUG lacks battery-backup switching, but has write-protection pins (active-low CE IN and active-low CE OUT) for CMOS RAM or EPROM. In addition, it consumes less than 250 microamperes.
Feature
- Adjustable Low-Line Monitor and Power-Down Reset
- Power-OK/Reset Time Delay
- Watchdog Timer—100ms, 1.6s, or Adjustable
- Minimum Component Count
- 1μA Standby Current
- Battery-Backup Power Switching (MAX696)
- On-Board Gating of Chip-Enable Signals (MAX697)
- Separate Monitor for Power-Fail or Low-Battery Warning
Applications
- Computers
- Controllers
- Critical μP Power Monitoring
- Intelligent Instruments