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PDF M62021L Data sheet ( Hoja de datos )
| Número de pieza | M62021L | |
| Descripción | SYSTEM RESET IC WITH SWITCH FOR MEMORY BACK-UP | |
| Fabricantes | Mitsubishi | |
| Logotipo |  |
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MITSUBISHI<Dig.Ana.INTERFACE>
M62021L,P,FP
SYSTEM RESET IC WITH SWITCH FOR MEMORY BACK-UP
DESCRIPTION
The M62021 is a system IC that controls the memory backup
function of SRAM and microcomputer (internal RAM).
The IC outputs reset signals(RES/RES) to a microcomputer
at power-down and power failure.It also shifts the power
supply to RAM from main to backup,outputs a signal (CS) that
invokes standby mode,and alters RAM to backup circuit mode.
The M62021 contains,in a single chip,power supply monitor
and RAM backup functions needed for a microcomputer
system,so that the IC makes it possible to construct a system
easily and with fewer components compared with a
conventional case that uses individual ICs and discrete
components.
PIN CONFIGURATION (TOP VIEW)
8 CS
7 RES
6 GND
5 RES
4 Ct(DELAY CAPACITANCE)
3 VIN
2 VBAT
FEATURES
•Built-in switch for selection between main power supply and
backup power supply to RAM.
•Small difference between input and output voltage
(IOUT=80mA,VIN=5V)0.2V typ
•Detection voltage (power supply monitor voltage)4.40V±0.2V
•Chip select signal output(CS)
Two channels of reset outputs(RES/RES)
•Power on reset circuit built-in
•Delay time variable by an external capacitance connected to
Ct pin
•Facilitates to form backup function with a few number of
components
1 VOUT
Outline 8P5(L)
VOUT 1
VBAT 2
VIN 3
Ct(DELAY CAPACITANCE) 4
8 CS
7 RES
6 GND
5 RES
Outline 8P4(P)
8P2S-A(FP)
APPLICATION
Power supply control systems for memory backup of
microcomputer system and SRAM boards with built-in
backup function that require switching between external
power supply and battery.
BLOCK DIAGRAM
VIN 3
RES 7
RES 5
SW
R1
- Com
RESET
R2 + CIRCUIT
1.24V
DELAY
CIRCUIT
6
GND
MITSUBISHI
ELECTRIC
1 VOUT
D1
2 VBAT
8 CS
4 Ct
( 1 /9)
1 page  
MITSUBISHI<Dig.Ana.INTERFACE>
M62021L,P,FP
SYSTEM RESET IC WITH SWITCH FOR MEMORY BACK-UP
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.
5
4
3 ∆Vs
2
VSL VSH
1
0
4.0 4.2 4.4 4.6 4.8 5.0
INPUT VOLTAGE VIN(V)
tpd VOH(Ct)
Delay time(tpd)= Ct X (R3 + R4) X In
=Ct X 22kΩ X 0.2614
.=.5.75 X 103 X Ct
[VOH(Ct)-VOL(Ct)]
[VOH(Ct)-INV1(VTH)]
*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.
INV1(Vth)
VOL(Ct)
DELAYED OUTPUT WAVEFORMS OF Ct
INTERNAL CIRCUIT
R1
60.94k
Com
R2 Vref
24K 1.24V
Ct
4
R3
22k
R4
47
Q1
R5
10k
VIN RES RES
3 57
R7 R8
Q4
R6 10k 10k
Q2
INV1 INV2 INV3 INV4
R10
800
Q3
INV5 INV6 INV7
R9
INV8 INV9 5k
R10
22k
Q5
D1
R11
10k
1 VOUT
2 VBAT
8 CS
6 GND
MITSUBISHI
ELECTRIC
( 5 /9)
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet M62021L.PDF ] | |
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