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| EM6151 Datasheet, PDF (1/10 Pages) EM Microelectronic - MARIN SA – Low Power Windowed Watchdog with Reset, Sleep Mode Functions | |||
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EM MICROELECTRONIC - MARIN SA
EM6151
Low Power Windowed Watchdog with Reset,
Sleep Mode Functions
Description
The EM6151 offers a high level of integration by combining
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 RES
and EN outputs are guaranteed to be in a correct state for a
supply 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 âopenâ time window. During the
remaining time, the watchdog time window is âclosedâ and a
reset will occur should a TCL pulse be received by the
watchdog during this âclosedâ 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 TCL input of the
EM6151 (version 55) and it goes into a stand-by mode in
order to save power (CAN-bus sleep detector).
Features
 Low quiescent current 35 μA
 -40°C to +125°C temperature range
 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)
 Voltage reference accuracy ±3%
 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 1.2 V
 System ENABLE output offers added security
 Qualified according to AEC-Q100
 Green SO-8 package (RoHS compliant)
Applications
 Automotive systems
 Industrial
 Home security systems
 Telecom / Networking
 Computers
 Set top boxes
Typical Operating Configuration
ROSC
VDD
EM6151
ROSC
VSS
VIN
TCL
RES
EN
R1
100nF
R2
VDD
I/O
RES
I/O
GND
Fig. 1
Selection Table
Part Number VREF
EM6151V30
EM6151V50
EM6151V53
EM6151V55
1.17 V
1.52 V
1.52 V
1.275 V
Closed
Window
67%
67%
33%
67%
Open
Window
33%
33%
67%
33%
CAN-bus sleep
detector
No
No
No
Yes
Please refer to Fig. 4 for more information about the
open/closed window of the watchdog.
Copyright © 2005, EM Microelectronic-Marin SA
1
rev. B / 06.06
www.emmicroelectronic.com
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