SMBP2501BPB datasheet(39/107 Pages) SONIX

39 / 107 page

SN8P2501B

8-Bit Micro-Controller

SONiX TECHNOLOGY CO., LTD

Page 39

Version 2.1

3.4.1 THE SYSTEM OPERATING VOLTAGE

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.

3.4.2 LOW VOLTAGE DETECTOR (LVD)

VDD

VSS

System Normal Run

System Stop

LVD Detect Voltage

Power On

Delay Time

Power

System Status

Power is below LVD Detect

Voltage and System Reset.

The LVD (low voltage detector) is built-in Sonix 8-bit MCU to be brown out reset protection. When the VDD drops and

is below LVD detect voltage, the LVD would be triggered, and the system is reset. The LVD detect level is different by

each MCU. The LVD voltage level is a point of voltage and not easy to cover all dead-band range. Using LVD to

improve brown out reset is depend on application requirement and environment. If the power variation is very deep,

violent and trigger the LVD, the LVD can be the protection. If the power variation can touch the LVD detect level and

make system work error, the LVD can’t be the protection and need to other reset methods. More detail LVD information

is in the electrical characteristic section.

The LVD is three levels design (2.0V/2.4V/3.6V) and controlled by LVD code option. The 2.0V LVD is always enable for

power on reset and Brown Out reset. The 2.4V LVD includes LVD reset function and flag function to indicate VDD

status function. The 3.6V includes flag function to indicate VDD status. LVD flag function can be an easy low battery

detector. LVD24, LVD36 flags indicate VDD voltage level. For low battery detect application, only checking LVD24,

LVD36 status to be battery status. This is a cheap and easy solution.

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