R
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 V
IN
input
comparing it with an internal voltage reference V
REF
. The
power-on reset function is initialized after V
IN
reaches V
REF
and takes the reset output inactive after a delay T
POR
depending on external resistance R
OSC
. The reset output goes
active low when the V
IN
voltage is less than V
REF
. 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 “open” time window. During the
remaining time, the watchdog time window is “closed” and a
reset will occur should a
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
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
Selection Table
Part Number
V
REF
Closed
Window
Open
Window
CAN-bus sleep
detector
V
DD
V
DD
100nF
Microprocessor
EM6151
R
OSC
R
OSC
V
SS
V
IN
TCL
RES
EN
R
1
EM6151
V30
EM6151
V50
EM6151
V53
EM6151
V55
1.17 V
1.52 V
1.52 V
1.275 V
67%
67%
33%
67%
33%
33%
67%
33%
No
No
No
I/O
RES
I/O
R
2
GND
Yes
Please refer to Fig. 4 for more information about the
open/closed window of the watchdog.
Fig. 1
Copyright © 2005, EM Microelectronic-Marin SA
rev. B / 06.06
1
www.emmicroelectronic.com
EMMICRO [ EM MICROELECTRONIC - MARIN SA ]
