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Microprocessor Supervisory Circuit

Full-Function µP Supervisory Circuit

Product Details

Key Features

Parametric specs for Battery Backup Circuits
Reset Thresh. (V) 3.3 to 5.5
Reset Out Active Low
Push-Pull
ICC (µA) (max) 150
Oper. Temp. (°C) -55 to +125
-40 to +85
0 to +70
Package/Pins CDIP/16
PDIP/16
SOIC (N)/16
Budgetary
Price (See Notes)
6.27
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Simplified Block Diagram

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Parameters

Parametric specs for Battery Backup Circuits
Reset Thresh. (V) 3.3 to 5.5
Reset Out Active Low
Push-Pull
ICC (µA) (max) 150
Oper. Temp. (°C) -55 to +125
-40 to +85
0 to +70
Package/Pins CDIP/16
PDIP/16
SOIC (N)/16
Budgetary
Price (See Notes)
6.27

Key Features

  • Precision 4.65V Voltage Monitoring
  • 200ms Power-OK/Reset Time Delay
  • Independent Watchdog Timer-Preset or Adjustable
  • 1µA Standby Current
  • Power Switching
    • 250mA Output in VCC Mode
    • 25mA Output in Battery-Backup Mode
  • On-Board Gating of Chip-Enable Signals
    • Memory Write-Cycle Completion
    • 6ns CE Gate Propagation Delay
  • MaxCap™ or SuperCap™ Compatible
  • Voltage Monitor for Power-Fail or Low-Battery Warning
  • Backup-Battery Monitor
  • Guaranteed RESET-bar Valid to VCC = 1V

Applications/Uses

  • Computers: Desktop, Workstation, Server
  • Controllers
  • Critical µP Monitoring
  • Intelligent Instruments
  • Portable Battery-Powered Equipment

Description

The MAX791 microprocessor (µP) supervisory circuit reduces the complexity and number of components needed to monitor power-supply and battery-control functions in µP systems. The 50µA supply current makes the MAX791 ideal for use in portable equipment, while the 6ns chip-enable propagation delay and 250mA output capability (25mA in battery-backup mode) make it suitable for larger, higher-performance equipment.

The MAX791 comes in 16-pin DIP and narrow SO packages and provides the following functions:
  1. µP reset-RESET-bar output is asserted during power-up, power-down, and brownout conditions, and is guaranteed to be in the correct state for VCC down to 1V, even with no battery in the circuit.
  2. Manual-reset input.
  3. A 1.25V threshold detector provides for power-fail warning and low-battery detection, or monitors a power supply other than +5V.
  4. Two-stage power-fail warning-a separate low-line comparator compares VCC to a threshold 150mV above the reset threshold.
  5. Backup-battery switchover for CMOS RAM, real-time clocks, µPs, or other low-power logic.
  6. Software monitoring of backup-battery voltage.
  7. A watchdog-fault output is asserted if the watchdog input has not been toggled within either a preset or an adjustable timeout period.
  8. Write protection of CMOS RAM or EEPROM.
  9. Pulsed watchdog output, to give advance warning of impending WDO-bar assertion caused by watchdog timeout.

Simplified Block Diagram

MAX791: Typical Operating Circuit MAX791: Typical Operating Circuit Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .

Sampling:
Selecting the Sample button above will redirect to the third-party ADI Sample Site. The part selected will carry over to your cart on this site once logged in. Please create a new account there if you have never used the site before. Contact SampleSupport@analog.com with any questions regarding this Sample Site.