AN2201 Freescale Semiconductor / Motorola, AN2201 Datasheet - Page 3

• Manufacturer Part Number: AN2201
• Description: Low Battery Cranking Pulse in Automotive Applications
• Manufacturer: Freescale Semiconductor / Motorola

MOTOROLA
6,5V-8.5V (?) early voltage drop warning
12-14V
Note that the absolute shape of the voltages Vbat, Vbat1 and Vdd can look
different from application to application due to combinations of voltage
regulator specifications and the surrounding components, but the overall
desired result is still the same; the module must not exhibit uncontrolled
behavior.
In some non-critical systems, it is often enough to make sure that the MCU is
being put into proper reset that keeps the application under control. Still, with
the rising complexity and increase of networking in the car, the desire is to finish
the ongoing communication with other modules before the application ceases
to work. Furthermore, it is not enough to simply reboot the system – data must
be stored safely while the MCU is unable to work.
Low Battery Cranking Pulse in Automotive Applications
5.0V
4.2V
3.7V
3.0V
0V
Freescale Semiconductor, Inc.
U
For More Information On This Product,
Cranking Pulse
(Example from Car maker)
Black Line = VBat coming directly from the car battery
Blue Line = Vbat1 (incl. voltage reversal protection)
Red Line
VBat
VBat1
Vdd
Go to: www.freescale.com
= Vdd to MCU
1
2
1
2
3
4
Figure 3
Early warning- MCU saves Data, enters power saving mode
(e.g. pseudo Stop + cyclic wake up)
MCU resumes normal operation, data integrity
check
MCU
VBat falling
3
sees
RESET
Data must be safe
MCU Reset
4
AN2201/D
t
3