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ELECTRIC

MITSUBISHI

M62021L,P,FP

MITSUBISHI<Dig.Ana.INTERFACE>

SYSTEM RESET IC WITH SWITCH FOR MEMORY BACK-UP

5

CONFIGURATION

<Power supply detector>

The internal reference voltage Vref is compared by means of

a comparator with resistor-divided voltage VR(resistor-divided

voltage produced by R1 and R2 from VIN).

If the input voltage is 5V,VR is set to 1.24V or higher,so the

comparator output is at low level and the Ct output(Q1

collector output)is set to high level.If the input voltage drops to

below 4.4V in an abnormal condition,VR becomes below

1.24V,so the comparator output goes from low to high level

and the Ct output,from high to low.The input voltage at this

point is called VSL.Next,when the input voltage,restored from

abnormal state,has a rise,the comparator output goes from

high to low level and the Ct output,from low to high.

The comparator used for detection has 100mV

hysteresis(

∆Vs),so that malfunctioning is prevented in case

that the input voltage slowly drops or VR nearly equals Vref.

<Delay Circuit>

Connecting an external capacitor to the Ct pin lets

RES,RES,CS,and VOUT be delayed due to RC transient

phenomenon(electric charge).

Delay time is determined as follows.

Delay time(tpd)= Ct X (R3 + R4) X In

[VOH(Ct)-INV1(VTH)]

[VOH(Ct)-VOL(Ct)]

=Ct X 22k

Ω X 0.2614

3

=5.75 X 10 X Ct

*Ct is an external capacitance.

.

.

Taking into consideration the time taken by the oscillator of

microcomputer to be stable,connect a 4.7µF capacitor to the

Ct pin.

(As the response time of detection can be slowed due to

internal structure depending on the rising rate of power

supply,avoid connecting a too large capacitance.

<Schmitt trigger circuit>

Since waveforms show a gentle rise due to the RC delay

circuit,INV1,INV2,R5,and R6 constitute a schmitt trigger circuit

to produce hysteresis so as to prevent each output from

chattering.

INTERNAL CIRCUIT

5

4

3

2

1

0

4.0 4.2 4.4 4.6 4.8 5.0

∆Vs

tpd

INV1(Vth)

DELAYED OUTPUT WAVEFORMS OF Ct

1

2

8

6

7

5

3

4

Ct

RES

RES

CS

GND

R1

60.94k

Q5

D1

Q4

Q3

Com

Q1

INV8

INV9

INV3 INV4

INV5 INV6 INV7

R4

R5

R6

R3

R9

R10

5k

22k

R7

R8

R2

24K

Vref

1.24V

22k

47

10k

INV1 INV2

10k

10k

800

R10

R11

10k

Q2