SN32F760 Series
32-Bit Cortex-M0 Micro-Controller
SONiX TECHNOLOGY CO., LTD
Page 42
Version 2.0
the power drops and keeps in dead-
band. Under the situation, the power won’t drop deeper and not touch the system
reset voltage. That makes the system under dead-band.
AC application:
In AC power application, the DC power is regulated from AC power source. This kind of power usually couples with AC
noise that makes the DC power dirty. Or the external loading is very heavy, e.g. driving motor. The loading operating
induces noise and overlaps with the DC power. VDD drops by the noise, and the system works under unstable power
situation.
The power on duration and power down duration are longer in AC application. The system power on sequence protects
the power on successful, but the power down situation is like DC low battery condition. When turn off the AC power, the
VDD drops slowly and through the dead-band for a while.
3.1.3.2
THE SYSTEM OPERATING VOLTAGE DECSRIPTION
To improve the brown out reset needs to know the system minimum operating voltage which is depend on the system
executing rate and power level. Different system executing rates have different system minimum operating voltage. The
electrical characteristic section shows the system voltage to executing rate relationship.
Vdd (V)
System Rate (Fcpu)
System Mini.
Operating Voltage.
System Reset
Voltage.
Dead-Band Area
Normal Operating
Area
Reset Area
Normally the system operation voltage area is higher than the system reset voltage to VDD, and the reset voltage is
decided by LVD detect level. The system minimum operating voltage rises when the system executing rate upper even
higher than system reset voltage. The dead-band definition is the system minimum operating voltage above the system
reset voltage.
3.1.3.3
BROWN-OUT RESET IMPROVEMENT
How to improve the brown reset condition?
There are some methods to improve brown out reset as following.
LVD reset
Watchdog reset
Reduce the system executing rate
External reset circuit. (Zener diode reset circuit, Voltage bias reset circuit, External reset IC)
Note: The “Zener diode reset circuit”, “Voltage bias reset circuit” and “External reset IC” can completely
improve the brown out reset, DC low battery and AC slow power down conditions.
