EM6153- LDO with Windowed Watchdog

5V Automotive Regulator with Inhibit Input and Windowed Watchdog - Ultra-Low Power

General Description

The EM6153 offers a high level of integration by combining voltage regulation, voltage monitoring and software monitoring using a windowed watchdog.

A comparator monitors the voltage applied at the VIN input comparing it with an internal voltage reference VREF. The power-on reset function is initialized after VIN reaches VREF and takes the reset output inactive after a delay TPOR depending on external resistance ROSC. The reset output goes active low when the VIN voltage is less than VREF. The inverted RES and EN outputs are guaranteed to be in a correct state for a regulated output voltage as low as 1.2 V. The watchdog function monitors software cycle time and execution.

If software clears the watchdog too quickly (incorrect cycle time) or too slowly (incorrect execution) it will cause the system to be reset. For enhanced security, the watchdog must be serviced within an “open” time window. During the remaining time, the watchdog time window is “closed” and a reset will occur should an inverted TCL pulse be received by the watchdog during this “closed” time window. The ratio of the open/closed window is either 33%/67% or 67%/33%.

The system ENABLE output prevents critical control functions being activated until software has successfully cleared the watchdog three times. Such a security could be used to prevent motor controls being energized on repeated resets of a faulty system.

When the microcontroller goes in stand-by mode or stops working, no signal is received on the inverted TCL input and the EM6153 (version 55) goes into a stand-by mode in order to save power (CAN-bus sleep detector). In EM6153, the voltage regulator has a low dropout voltage and a low quiescent current of 75 /m/A. The quiescent current increases only slightly in dropout prolonging battery life. Built-in protection includes a positive transient absorber for up to 45 V (load dump) and the ability to survive an unregulated input voltage of -42 V (reverse battery). The input may be connected to ground or to a reverse voltage without reverse current flowing from the output to the input.

Solutions

  • Automotive systems
  • Industrial
  • Home security systems
  • Telecom / Networking
  • Computers
  • Set top boxes

Tools
Resistor Calculation Tool
The excel file below helps to calculate the value of the external resistor ROSC for a given/wanted watchdog timeout period.

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Features

  • Low quiescent current 90 mA
  • Very low OFF current consumption < 1mA
  • -40°C to +125°C temperature range
  • Highly accurate 5V, 150 mA guaranteed output (actual maximum current depends on power dissipation)
  • Low dropout voltage, typically 250 mV at 100 mA
  • Unregulated DC input can withstand -42V reverse battery and +45V power transients
  • Fully operational for unregulated DC input voltage up to 40V and regulated output voltage down to 3.5V
  • No reverse output current
  • Very low temperature coefficient for the regulated output
  • Current limiting
  • Windowed watchdog with an adjustable time windows, guaranteeing a minimum time and a maximum time between software clearing of the watchdog
  • Time base accuracy ±8% (at 100ms)
  • Sleep mode function (V55)
  • Adjustable threshold voltage using external resistors
  • Adjustable power on reset (POR) delay using one external resistor
  • Open-drain active-low RESET output
  • Reset output guaranteed for regulated output voltage down to 1.2V
  • System ENABLE output offers added security
  • Green SO-16 Exposed pad package (RoHS compliant)
AttachmentSize
Resistor Calculation Tool170 KB