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MITSUMI
System Reset (with built-in watchdog timer) MM1142
System Reset (with built-in watchdog timer)
Monolithic IC MM1142
Outline
This IC was developed to drive low voltage batteries, and has a watchdog timer with built-in microcomputer
reset voltage detection circuit and low battery detection circuit.
A single reference voltage is used for low battery voltage detection and microcomputer reset voltage
detection, so detection voltage difference is uniform (
.
=. 0.2V). Further, there is a built-in watchdog timer for
operation diagnosis, which prevents the system from running wild by generating an intermittent reset pulse
during system mis-operation.
Features
1. Accurate voltage drop detection voltage
1. Low battery detection
2.2V3%
2. Power supply voltage detection
2.0V3%
3. Detection voltage error
0.2V20mV 1-2
4. Hysteresis
both 50mV typ.
2. Watchdog function stop pin (can be made to function only as reset IC during V
CC
rise)
3. Low current consumption
150A typ.
Package
SOP-8C (MM1142XF)
Series Table
T
PR
: Reset hold time during Vcc rise
T
WD
: Timer monitoring time
T
WR
: Reset time
V
SLB
: Battery check detection voltage
V
SLR
: Reset detection voltage
Model
V
SLB
V
SLR
T
PR
T
WD
T
WR
MM1142
2.2V
2.0V
100mS
100mS
2mS
*
C
T
=0.02F
Applications
1. 2V cordless telephones
2. Portable communication equipment
3. Various types of small, handy equipment
MITSUMI
System Reset (with built-in watchdog timer) MM1142
1
4
3
2
8
5
6
7
SOP-8C
Pin Assignment
Pin Description
Block Diagram
1
TC
2
BC(RESET
----------------------------------------------
)
3
CK
4
GND
5
V
CC
6
RCT
7
V
S
8
RESET
----------------------------------------------
Pin No.
Pin name
Function
1
TC
T
WD
, T
WR
, T
PR
time setting pins.
2
BC(RESET
-----------------------------------------------------------------------------------
) Battery check output pin (RESET low level output) for 3.4V
3
CK
Clock input pin
4
GND
GND pin
5
V
CC
Power supply voltage input pin
6
RCT
Watchdog timer stop pin Operation modes
Operation OPEN, Stop connect to GND
7
V
S
Detection voltage fine adjustment pin
8
RESET
-----------------------------------------------------------------------------------
Reset output pin (low output)
MITSUMI
System Reset (with built-in watchdog timer) MM1142
Absolute Maximum Ratings
(Ta=25
C)
Recommended Operating Conditions
Item
Symbol
Rating
Units
Power supply voltage
V
CC
max.
-0.3~+7
V
Voltage applied to input pin
V
IN
-0.3~V
CC
+0.3 ( <
= +7)
V
Voltage applied to output pin
V
OUT
-0.3~V
CC
+0.3 ( <
= +7)
V
Allowable loss
Pd
300
mW
Storage temperature
T
STG
-40~+125
C
Item
Symbol
Rating
Units
Power supply voltage
V
CC
+1.9~+6.5
V
RESET sync current
I
OLR
0~500
A
BC sync current
I
OLC
0~5.0
mA
Clock input high level voltage
V
CKH
1.0<
V
Clock input low level voltage
V
CKL
<0.2
V
Clock monitoring time setting
T
WD
1~10000
mS
Clock rise and fall times
t
RCK
, t
FCK
<100
S
Power supply voltage rise times
t
RVCC
100<
S
Power supply voltage fall times
t
FVCC
50<
S
TC pin capacitance
C
T
0.0022~2.2
F
Operating temperature
T
OP
-20~+70
C
Item
Symbol
Measurement conditions
Min. Typ. Max.
Units
Consumption current
I
CC
No load
200
280
A
RESET detection voltage
V
SLR
V
CC
: High Low, RCT : GND, V
TC
=OPEN
2.00
3%
V
Detection voltage temperature
0.01 0.05
%/
C
coefficient R
Hysteresis voltage R
V
HYSR
V
CC
: Low High, RCT=GND, V
TC
=OPEN
25
50
100
mV
BC detection voltage
V
SLB
V
CC
: High Low, R
LB
=10k
2.20
3%
V
Detection voltage temperature
0.01 0.05
%/
C
coefficient B
Hysteresis voltage B
V
HYSB
V
CC
: Low High, R
LB
=10k
25
50
100
mV
Detection voltage difference
V
SL
V
SL
=V
SLB
-V
SLR
0.175 0.200 0.225
V
CK input threshold
V
TH
0.4
0.6
1.2
V
CK input current
I
IH
V
CK
=2.6V
0
1
A
I
IL
V
CK
=0.0V
-15
-6
-2
Output voltage RH
V
OHR
I
RESET
--------------------------------------------
=-1A
2.0
2.2
V
Output voltage BH
V
OHB
R
LB
=10k
2.0
2.2
V
Output voltage RL
V
OLR
I
RESET
--------------------------------------------
=500A, V
CC
=1.8V
0.3
0.5
V
Output voltage BL
V
OLB
I
BC
=5mA, V
CC
=1.8V
0.3
0.5
V
Output sync current R
I
OLR
V
RESET
--------------------------------------------
=0.5V, V
CC
=1.8V
500
700
A
Output sync current B
I
OLB
V
BC
=0.5V, V
CC
=1.8V
5
7
mA
Output source current R
I
OHR
V
RESET
--------------------------------------------
=2.0V
2
4
A
C
T
charge current
I
CT
1
V
TC
=0.5V during watchdog timer operation -0.300 -0.150 -0.075
A
I
CT
2
V
TC
=0.5V during power ON reset operation -0.300 -0.150 -0.075
Minimum operating power supply voltage
V
CCL
0.8
1.0
V
to ensure RESET
-------------------------------------------------------------------------------
V
SR
T
V
SB
T
Electrical Characteristics
(Except where noted otherwise, Ta=25C, V
CC
=2.6V)
V
RESET
---------------------------------------------
=0.4V, I
RESET
---------------------------------------------
=0.05mA
MITSUMI
System Reset (with built-in watchdog timer) MM1142
Item
Symbol Measurement
conditions
Min.
Typ.
Max.
Units
V
CC
input pulse width
20
T
PI
S
CK input pulse width
T
CKW
10
S
CK input cycle
T
CK
50
S
Watchdog timer
T
WD
C
T
=0.022F
50
100
150
mS
monitoring time
*
1
Watchdog timer
reset time
*
2
T
WR
C
T
=0.022F
1
2
3
mS
Reset hold time for
power supply rise
*
3
T
PR
C
T
=0.022F
50
100
150
mS
RESET
------------------------------------------------------
delay time
t
PDR
V
CC
: High Low, R
LR
=100k
, C
LR
=15pF
10
S
BC delay time
t
PDB
V
CC
: High Low, R
LB
=10k
, C
LB
=15pF
10
S
RESET
------------------------------------------------------
rise time
t
RR
R
LR
=100k
, C
LR
=15pF
10
S
RESET
------------------------------------------------------
fall time
t
FR
R
LR
=100k
, C
LR
=15pF
2
S
BC rise time
t
RB
R
LB
=10k
, C
LB
=15pF
10
S
BC fall time
t
FB
R
LB
=10k
, C
LB
=15pF
2
S
V
CC
2.6V
1.8V
CK
T
CKW
or
CK
T
CK
T
PI
Notes:
*
1 Monitoring time is the time from the last pulse (negative edge) of the timer clear clock pulse until reset
pulse output.
In other words, reset output is output if a clock pulse is not input during this time.
*
2 Reset time means reset pulse width. However, this does not apply to power ON reset.
*
3 Reset hold time is the time from when V
CC
exceeds detection voltage (V
SHR
) during power ON reset until
reset release (RESET
----------------------------------------------
output high).
*
4 Watchdog timer monitoring time (T
WD
), watchdog timer reset time (T
WR
) and reset hold time (T
PR
) during
power supply rise can be changed by varying C
T
capacitance. The times are expressed by the following
formulae.
Example : When C
T
=0.22F
T
PR
(mS) ~
- 4500 C
T
(F) T
PR
~
- 100mS
T
WD
(mS) ~
- 4500 C
T
(F)
T
WD
~
- 100mS
T
WR
(mS) ~
- 90 C
T
(F)
T
WR
~
- 2mS
*
5 T
WD
can be varied by placing a resistor (1M
or more)between the RCT pin and V
CC
.
*
6 The voltage range when measuring output rise and fall time is 10~90%.
*
7 V
CC
rise time should be 100S or more, and fall time should be 50S or more.
MITSUMI
System Reset (with built-in watchdog timer) MM1142
Measuring Circuit
Timing Chart
V
CC
CK
C
T
RESET
BC
RCT
V
SHB
V
SLB
V
SHR
V
SLR
0.8V
T
CK
T
CKW
T
PR
T
WR
T
WD
OPEN
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