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MITSUMI
System Reset (with built-in watchdog timer) MM1095
System Reset (with built-in watchdog timer)
Monolithic IC MM1095
Outline
This IC functions in a variety of CPU systems and other logic systems to generate a reset signal and reset the system accurately during momentary interruption or lowering of power supply voltage. It also has a built-in watchdog timer for operation diagnosis. This prevents the system from running wild by generating an intermittent reset pulse during system mis-operation.
Features
1. 2. 3. 4. 5. Built-in watchdog timer Low minimum operating voltage Low operating limit voltage Watchdog stop function (RCT pin) Few external parts 100A typ. Vcc=0.8V
Package
DIP-8B (MM1095AD, MM1095BD) SOP-8C (MM1095AF, MM1095BF) SIP-8A (MM1095AS, MM1095BS)
Applications
1. Reset circuits in microcomputers, CPUs and MPUs 2. Logic circuit reset circuits 3. Microcomputer system monitoring, etc.
Pin Assignment
1 2 8 7 6 5 3 4 5 1 2 3 4 6 7 SOP-8C/DIP-8B 8
TC NC CK GND VCC RCT VS
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1 2 3 4 12345678 SIP-8A 5 6 7 8
TC NC CK GND VCC RCT VS
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RESET
RESET
MITSUMI
System Reset (with built-in watchdog timer) MM1095
Pin Description
Pin No. Name TWD, TWR, TPR variable pins 1 TC N.C CK GND VCC RCT VS
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Function . (TWD, TWR and TPR times are determined by the external capacitor.) TPR (ms)=5000 TWD (ms)=500 TWR (ms)=100 CT (F) CT (F) CT (F)
2 3 4 5 6 7 8
Clock input pin, inputs clock from logic system GND pin Voltage detection MM1095A 3.2V, MM1095B 4.2V OPEN, Stop connect to GND Watchdog timer stop pin Operation modes : Operation
Detection voltage variable pin
RESET Reset output pin (low output)
Absolute Maximum Ratings
Item Power supply voltage CK pin input voltage VS pin input voltage Voltage applied to RCT pin
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Symbol VCC max. VCK VVS VRCT VOH Pd TSTG
Rating -0.3~+10 -0.3~VCC+0.3 ( < +10) = -0.3~VCC+0.3 ( < +10) = -0.3~VCC+0.3 ( < +10) = -0.3~VCC+0.3 ( < +10) = 400 -40~+125
Units V V V V V mW C
Voltage applied to RESET pin Allowable loss Storage temperature
Recommended Operating Conditions
Item Power supply voltage
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Symbol VCC IOL TWD tFC, tRC CT TOP
Rating +2.2~+7.0 0~1.0 0.1~1000 <100 0.0002~2 -25~+75
Units V mA ms s F
C
RESET sync current Clock monitoring time setting Clock rise and fall times TC pin capacitance Operating temperature
MITSUMI
System Reset (with built-in watchdog timer) MM1095
Electrical Characteristics (DC)
Item Consumption current MM1095A MM1095B MM1095A Detection voltage MM1095B MM1095A MM1095B Detection voltage temperature coefficient Hysteresis voltage MM1095A MM1095B Symbol ICC VSL VSH VS/ T VHYS VTH IIH IIL VOH VOL1 VOL2 IOL ICT1 ICT2 VCCL
(Except where noted otherwise, MM1095A : Vcc=3.6V, Ta = 25C, MM1095B: Vcc=5.0V) Measurement conditions Min. Typ. 100 130 3.10 4.05 3.15 4.15 3.20 4.20 3.25 4.30 0.01 Max. 150 195 3.30 4.35 3.35 4.45 %/C 100 150 2 1 -2 mV V A V 0.4 0.5 -4.80 -0.48 1.0 V mA A A V V Units A
During watchdog timer operation VS=OPEN, VCC VS=OPEN, VCC
VSH-VSL, VCC
25 50 0.8
50 100 1.2 0 -6 3.4 4.5 0.2 0.3
CK input threshold CK input current Output voltage MM1095A (High) MM1095B
A : VCK=3.6V, B : VCK=5.0V VCK=0V I RESET =-1A VS=OPEN I RESET =0.5mA, VS=0V I RESET =1.0mA, VS=0V V RESET =1.0V, VS=0V VTC=1.0V during watchdog timer operation VTC=1.0V during power ON reset operation V RESET =0.4V I RESET =0.1mA
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-12 3.0 4.0
Output voltage (Low) R output sync current CT charge current Minimum operating power
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1 -1.60 -0.16
2 -2.40 -0.24 0.8
supply voltage to ensure RESET
MITSUMI
System Reset (with built-in watchdog timer) MM1095
Electrical Characteristics (DC)
Item MM1095A TPI MM1095B TCKW TCK TWD TWR TPR TPD tR tF VCC CK Symbol VCC
(Except where noted otherwise, MM1095A : VCC=3.6V, Ta=25C, MM1095B : VCC=5.0V) (Except where noted otherwise, resistance unit is )
Measurement conditions 3.6V 2.8V 5.0V 4.0V or
Min. 8
Typ.
Max.
Units
VCC input pulse width
s 8 3 20 CT=0.02F CT=0.02F 5 1 50 10 2 100 2 2.0 0.2 15 3 150 10 4.0 1.0 s s ms ms ms s s s
CK input pulse width CK input cycle Watchdog timer monitoring time 1
*
Reset time for watchdog timer 2
*
Reset hold time for power supply rise 3
*
CT=0.02F, VCC
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VCC
Output delay time from VCC 4
*
RESET pin, RL=10k, CL=20pF
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Output rise time 5
* Output fall time 5 *
RESET pin, RL=10k, CL=20pF
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RESET pin, RL=10k, CL=20pF
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 VCC exceeds detection voltage (VSH) during power ON reset until reset release (RESET output high). 4 Output delay time is the time from when power supply voltage drops below detection voltage (VSL) until reset (RESEToutput low). 5 Voltage range when measuring output rise and fall is 10~90%. 6 Watchdog timer monitoring time (TWD), watchdog timer reset time (TWR) and reset hold time (TPR) during power supply rise can be changed by varying CT capacitance. The times are expressed by the following formulae.
* * * * * *
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. TPR (ms) = 5000 CT (F) . TWD (ms) . . 500 CT (F) = TWR (ms) . . 100 CT (F) = Example: When CT=0.02F TPR . . 100ms = TWD . . 10ms = TWR . . 2ms =
MITSUMI
System Reset (with built-in watchdog timer) MM1095
Measuring Circuits
Measuring Circuit 1(DC) Measuring Circuit 2 (AC)
Measuring Circuit 1
Item Consumption current Detection voltage CK input threshold CK input current Output voltage (High) Output voltage (Low) Output sink current CT charge current 1 CT charge current 2 Minimum operating power
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SW & Power Supply Table
VCC 3.6V VCK 3.6V VCT 0V 2V 2V 1V 0V 0V 2V 2V 2V 2V 1V 1V 0V I RESET -1A 0.5mA 1.0mA -------------------------------------------------------
Symbol SW1 SW2 SW3 SW4 SW5 SW6 SW7 ICC VSL VSH VTH IIH IIL VOH VOL1 VOL2 IOL1 ITC1 ITC2 VCCL OFF OFF OFF OFF OFF OFF ON ON ON OFF OFF OFF ON OFF OFF OFF OFF OFF OFF OFF ON ON ON OFF OFF OFF OFF ON ON OFF OFF OFF ON ON ON ON OFF OFF ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON OFF OFF ON A A A A A A A A A B A A A
VM, IM ICC VO1, CRT1 VO1, CRT1 ICK, VCK ICK ICK VO1 VO1 VO1 IO1 ITC ITC VO1, VCC
Notes
3.6V 3V 0V 3V 3.6V 0V 3.6V 0V 3V 3.6V 3.6V 3.6V 3.6V 3.6V 3.6V 3.6V 3.6V 0V 2V 3.6V 0V 3.6V 3.6V 3.6V 3.6V 0V
VO=1V
supply voltage to ensure RESET
Measuring Circuit 2
Item VCC input pulse width TP1
SW & Power Supply Table
VCCA 3.6V 2.5V 3.6V 0V T1 VCC 3.6V 3.6V 3.6V 3.6V 3.6V 3.6V 3.6V 1.4V 0V 1.4V 0V 1.4V 0V T2 or T2 T2 T3 3.6V 3.6V 3.6V 0V 3.6V 3.6V VCKA T2 T3 VCK CRT CRT1 CRT2 CRT1 CRT2 CRT1 CRT2 CRT1 CRT2 CRT1 CRT2 CRT1 CRT2 CRT1 CRT1 CRT1 Notes T1=8s T2=3s T3=20s
Symbol SW1 SW2 C A A A A BA C A A B B B A A A A A A
CK input pulse width TCKW CK input cycle Watchdog timer monitoring time Reset time for watchdog timer Reset hold time for power supply rise Output delay time from VCC Output rise time Output fall time TCK TWD TWR TPR TPD TR TF
MITSUMI
System Reset (with built-in watchdog timer) MM1095
Block Diagram
RA MM1095A MM1095B ~ 305k ~ 350k RB ~ 195k ~ 150k -
Note 1 : CP=0.1F approx. Note 2 : C > 1000pF = Note 3 : The watchdog timer can be stopped by connecting the RCT pin to GND. (Then it functions as a voltage detection circuit.)
Timing Chart
VCC
VSH VSL
CK
CT
TCK
RESET
TPR
TWD
TWR
TPR
12
345
5
67
89
10
1 12 1
MITSUMI
System Reset (with built-in watchdog timer) MM1095
Description of Operation
1. RESET goes low when VCC rises to approximately 0.8V. 2. Capacitor CT charging starts when VCC rises to VSH (MM1095A . . 3.25V, MM1095B . . 4.3V). Output is in = = reset state at this time. 3. Output reset is released (RESET goes high) after a certain time (TPR), from when CT starts charging until discharge (the time from when CT voltage reaches a certain threshold value 1 (. . 1.4V) until CT voltage = . 0.2V). Approximately 1A (VCC=0.8V) drops to a certain threshold value 2 ( = of pull up current is output . from RESET. Reset hold time : TPR is as follows. TPR (ms) . . 5000 CT (F) = CT charging starts again after reset release, and watchdog timer operation begins. 4. If a clock is input (negative edge trigger) to the CK pin during CT charging, charging switches to discharge. 5. Discharge switches to charging when CT voltage drops to a certain threshold value (. . 0.2V). Steps 4 and 5 = are repeated while a normal clock is input from the logic system. 6. Output goes to reset state (RESET goes low) when the clock ceases and CT voltage reaches reset ON threshold value (. . 1.4V). = The formula for CT charging time (TWD: watchdog timer monitoring time) until reset is output is as follows. TWD (ms) . . 500 CT (F) = 7. Watchdog timer reset time TWR is the discharge time until CT voltage drops to reset OFF threshold value . ( = 0.2V). The formula is as follows. . TWR (ms) . . 100 CT (F) = After reset OFF threshold value is reached, output reset is released and CT starts charging. Thereafter, steps 4 and 5 are repeated if a normal clock is input, and when the clock ceases, 6 and 7 are repeated. 8. Reset is output when VCC drops to VSL (MM1095A . . 3.2V, MM1095B . . 4.2V). CT is charged = = simultaneously. 9. CT charging starts when VCC rises to VSH. When Vcc drops momentarily, CT charging begins after the charge is first discharged, if the time from VCC dropping below VSL until it rises to VSH is longer than the VCC input pulse width standard value TPI. 10.Output reset is released after VCC goes above VSH and after TPR, and the watchdog timer starts. Thereafter, 8~10 are repeated when VCC goes below VSL. 11.When power is OFF, reset is output if VCC goes below VSL. 12.When VCC drops to 0V, reset output is held until VCC reaches 0.8V.
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