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System reset (with built-in watchdog timers): Monolithic IC MM1099a

Posted: 11 Jun 2003     Print Version  Bookmark and Share

Keywords:power 

ARTICLES/2003JUN/A/2003JUN11_ICD_POW_AN.PDF

MITSUMI System Reset (Built-in Watch Dog Timer) MM1099

System Reset (Built-in Watch Dog Timer)

Monolithic IC MM1099

Outline

The function of this IC series MM1099 is to accurately reset systems, a generating reset signal at the time of

instantaneous supply voltage off or lowering in varied CPU and other logic system.

Further, with the watch dog timer built-in it can diagnose the operation of the system, intermittently

generating reset pulses when they operate erroneously to prevent runaway.

Features

1. Built-in watch dog timer

2. Low current consumption 1305A TYP.

3. Low operating threshold voltage VCC=0.8V

4. Watch dog stop function (RCT terminal)

5. Long clock monitoring time

TPR (POWER ON) : TWD (clock monitoring)=1 : 1

6. Fewer outer components

Package

DIP-8B (MM1099AD, MM1099BD)

SOP-8C (MM1099AF, MM1099BF)

SIP-8A (MM1099AS, MM1099BS)

Applications

1. Reset circuit for microcomputers, CPU and MPU.

2. Reset circuit for logic circuitry.

3. Monitoring of microcomputer system, etc.

Pin Assignmemt

1 432

8 567

SOP-8C/DIP-8B

(TOP VIEW)

1 TC

2 N.C

3 CK

4 GND

5 VCC

6 RCT

7 VS

8 RESET

-----------------------------------------------------------

1 TC

2 N.C

3 CK

4 GND

5 VCC

6 RCT

7 VS

8 RESET

-----------------------------------------------------------

SIP-8A

1 3 5 72 4 6 8

MITSUMI System Reset (Built-in Watch Dog Timer) MM1099

Pin Description

Pin No. Pin name Function

1 TC

2 N.C

3 CK

4 GND

5 VCC

6 RCT

7 VS

8 RESET

Variable terminals TWD, TWR and TPR TPR (ms) = 5000 CT (5F)

The time for TWD, TWR and TPR to be TWD (ms) = 500 CT (5F)

determined by the external capacitor. TWR(ms) = 100 CT (5F)

Clock input terminal Inputs the clock from the logic system.

Ground terminal

Voltage detection MM1099A 3.2V MM1099B 4.2V

Watchdog timer stop pin Operation modes: Operation OPEN, Stop connect to GND

Detect voltage variable terminal

Reset output pin (low output)

Absolute Maximum Ratings

Item Symbol Rating Units

Power supply voltage VCC max. -0.3~+10 V

CK pin input voltage VCK -0.3~VCC+0.3 ( <= +10) V

VS pin input voltage VVS -0.3~VCC+0.3 ( <= +10) V

Voltage applied to RCT pin VRCT -0.3~VCC+0.3 ( <= +10) V

Voltage applied to RESET

----------------------------------------------------

pin VOH -0.3~VCC+0.3 ( <= +10) V

Allowable loss Pd 300 mW

Storage temperature TSTG -40~+125 0C

Recommended Operating Conditions

Item Symbol Rating Units

Power supply voltage VCC +2.2~+7.0 V

RESET

----------------------------------------------------

sync current IOL 0~1.0 mA

Clock monitoring time setting TWD 0.1~1000 ms

Clock rise and fall times tFC, tRC <100 5s

TC pin capacitance CT 0.0002~2 5F

Operating temperature TOP -25~+75 0C

MITSUMI System Reset (Built-in Watch Dog Timer) MM1099

Electrical Characteristics (DC) (Except where noted otherwise, MM1099A : VCC=3.6V, Ta=250C, MM1099B : VCC=5.0V)

Item Symbol Measurement conditions Min. Typ. Max. Units

Consumption current

MM1099A

ICC During watchdog timer operation

(100) (150)

5A

MM1099B 130 195

MM1099A

VSL

3.10 3.20 3.30

Detection voltage

MM1099B 4.05 4.20 4.35

V

MM1099A

VSH

3.15 3.25 3.35

MM1099B 4.15 4.30 4.45

Detection voltage temperature coefficient VS/ T 10.01 %/0C

Hysteresis voltage

MM1099A

VHYS

25 50 100

mV

MM1099B 50 100 150

CK input threshold VTH 0.8 1.2 2 V

CK input current

IIH A : VCK=3.6V, B : VCK=5.0V 0 1

5A

IIL VCK=0V -12 -6 -2

Output voltage MM1099A

VOH

3.0 3.4

V

(High) MM1099B 4.0 4.5

Output voltage (Low)

VOL1 I =0.5mA, VS=0V 0.2 0.4

V

VOL2 I =1.0mA, VS=0V 0.3 0.5

R output sync current IOL V =1.0V, VS=0V 1 2 mA

CT charge current

ICT1 VTC=1.0V during watchdog timer operation -0.16 -0.24 -0.48 5A

ICT2 VTC=1.0V during power ON reset operation -0.16 -0.24 -0.48 5A

Minimum operating power

VCCL 0.8 1.0 V

supply voltage to ensure RESET

---------------------------------------------------

RESET

----------------------------------------------------

RESET

----------------------------------------------------

RESET

----------------------------------------------------

VS=OPEN, VCC

VS=OPEN, VCC

VSH-VSL, VCC

V =0.4V

I =0.1mARESET

----------------------------------------------------

RESET

----------------------------------------------------

I =-15A, VS=OPENRESET

----------------------------------------------------

MITSUMI System Reset (Built-in Watch Dog Timer) MM1099

Electrical Characteristics (AC)

(Except where noted otherwise, MM1096A : VCC=3.6V, Ta=250C MM1096B : VCC=5.0V)

(Except where noted otherwise, resistance unit is )

Notes :

*1 The "monitoring time" means the time interval from the last pulse of the clock pulses for timer clear

(negative edge) to the output of the reset pulse. If the clock pulse is not input during this time interval, the

reset output will be given.

*2 The "reset time" is no other than the reset pulse width, except when resetting the POWER ON.

*3 The "reset hold time" is the time interval from the time point when VCC exceeds the detect (VSH) at the time

of Power On Reset (Power variation reset) to the reset release (RESET

-------------------------------------------------

output "HIGH").

*4 The "output delay time" means the time interval from when the supply voltage comes lower than the

detect voltage (VSL) to when comes the reset state (RESET

-------------------------------------------------

output "Low").

*5 The voltage range is 10 to 90% when measuring the output rise and fall times.

*6 By varying the capacitance of CT, we can vary the watch dog timer monitoring time (TWD), the reset time at

the time of the watch dog timer (TWR), and the reset hold time at the time of power source rise (TPR). The

variable time can be expressed by the following formulas:

TPR (ms) .=. 5000 CT (5F)

TWD (ms) .=. 5000 CT (5F)

TWR (ms) .=. 100 CT (5F)

Example : When CT=0.025F

TPR

.

=. 100ms

TWD

.

=. 100ms

TWR

.

=. 2ms

Item Symbol Measurement conditions Min. Typ. Max. Units

MM1099A 8

VCC input

TPI 5s

pulse width

MM1099B 8

CK input pulse width TCKW 3 5s

CK input cycle TCK 20 5s

Watchdog timer

monitoring time

*1

TWD CT=0.025F 50 100 150 ms

Reset time for

watchdog timer

*2

TWR CT=0.025F 1 2 3 ms

Reset hold time for

power supply rise

*3

TPR 50 100 150 ms

Output delay time from VCC

*4 TPD RESET

----------------------------------------------------------------------

pin, RL=10k, CL=20pF 2 10 5s

Output rise time

*5 tR RESET

----------------------------------------------------------------------

pin, RL=10k, CL=20pF 2.0 4.0 5s

Output fall time

*5 tF RESET

----------------------------------------------------------------------

pin, RL=10k, CL=20pF 0.2 1.0 5s

VCC

3.6V

2.8V

VCC

5.0V

4.0V

CT=0.025F, VCC

CK or

MITSUMI System Reset (Built-in Watch Dog Timer) MM1099

Measuring Circuits

Measuring Circuit 1 (DC) Measuring Circuit 2 (AC)

Measuring Circuit 1 SW & Power Supply Table

Measuring Circuit 2 SW & Power Supply Table

Item Symbol SW1 SW2 SW3 SW4 SW5 SW6 SW7 VCC VCK VCT I VM, IM Notes

Consumption current ICC OFF OFF OFF ON ON ON A 3.6V 3.6V 0V - ICC

Detection voltage

VSL OFF OFF ON ON ON ON A 3.6V 3V 0V 2V - VO1, CRT1

VSH OFF OFF ON ON ON ON A 3V 3.6V 0V 2V - VO1, CRT1

CK input threshold VTH OFF OFF OFF ON ON ON A 3.6V 0V 3V 1V - ICK, VCK

CK input current

IIH OFF OFF OFF ON ON ON A 3.6V 3.6V 0V - ICK

IIL OFF OFF OFF ON ON ON A 3.6V 0V 0V - ICK

Output voltage (High) VOH ON OFF ON ON ON ON A 3.6V 3.6V 2V -15A VO1

Output voltage (Low)

VOL1 ON ON ON ON ON ON A 3.6V 3.6V 2V 0.5mA VO1

VOL2 ON ON ON ON ON ON A 3.6V 3.6V 2V 1.0mA VO1

Output sink current IOL1 OFF ON ON ON ON ON B 3.6V 3.6V 2V - IO1 VO=1V

CT charge current 1 ITC1 OFF OFF OFF ON ON OFF A 3.6V - 1V - ITC

CT charge current 2 ITC2 OFF OFF OFF ON ON OFF A 3.6V - IV - ITC

Minimum operating power

supply voltage to ensure RESET

------------------------------------------------------ VCCL ON OFF ON ON ON ON A 0V 2V 0V 0V - VO1, VCC

RESET

-----------------------------------------------

Item Symbol SW1 SW2 VCCA VCC VCKA VCK CRT Notes

VCC input pulse width TP1 C B - -

CRT1

T1=85s

CRT2

CK input pulse width TCKW A B - 3.6V -

CRT1

T2=35s

CRT2

CK input cycle TCK A B - 3.6V -

CRT1

T3=205s

CRT2

Watchdog timer

TWD A A - 3.6V - 3.6V

CRT1

monitoring time CRT2

Reset time

TWR A A - 3.6V - 3.6V

CRT1

for watchdog timer CRT2

Reset hold time for

TPR B A A - 3.6V - 3.6V

CRT1

power supply rise CRT2

Output delay time

from VCC

TPD C A - - 0V CRT1

Output rise time TR A A - 3.6V - 3.6V CRT1

Output fall time TF A A - 3.6V - 3.6V CRT1

3.6V

2.8V

T1 1.4V

0V

T2 T3

1.4V

0V

T2

T2or

1.4V

0V

3.6V

0V

T2 T3

MITSUMI System Reset (Built-in Watch Dog Timer) MM1099

Block Diagram

RA RB

MM1099A ~- 305k ~- 195k

MM1099B ~- 350k ~- 150k

Note 1. Cp = approx. 0.15F

Note 2. C >= 1000pF

Note 3. The watchdog timer can be stopped by grounding the RCT pin.

(Function as voltage detection circuit.)

Note 4. TPR, TWD can be varied by pulling up the RCT pit to VCC using a resisteor.

Timing Chart

1 2 3 4 5 5 6 7 8 9 10 11 12

VCC

CK

CT

RESET

VSL

0.3V

VSH

TCK

TPR TWD

TWR

TPR

MITSUMI System Reset (Built-in Watch Dog Timer) MM1099

Description of Operation

1. The RESET

-------------------------------------------------------

will become "Low" if VCC rises to about 0.8V.

Approximately 15A (Vcc=0.8V) of pull up current is output from RESET

----------------------------------------------------------------

2. Charging starts at the capacitor CT when VCC riset to VSH (MM1099A

.

=. 3.25V, MM1099B

.

=. 4.3V), when the

output has been reset.

3. The output reset is released after a given interval TPR from when the CT Starts charging and to when it

discharges (that is, the time from when CT voltage takes a given value 1 (

.

=. 1.4V) up until decreases to a

given value 2 (.=. 0.2V). (RESET

-------------------------------------------------------

will become "High"). The RESET will output a pull up current, about 15A

(VCC=0.8V). The reset hold time TPR is expressed by the following formula:

TPR (ms)

.

=. 5000 CT (5F)

After the reset release CT restarts charging and the watch dog timer begins operating.

Note that input of clock while POWER ON RESET time TPR will cause an erroneous operation.

4. If clock is input into CK terminal while CT is charging (negative edge trigger), CT changes from charging

over to discharging.

5. When the CT voltage decreases to a given threshold (

.

=. 0.2V), then discharging changes over to charging.

Steps 4 and 5 will be repeated while normal clock is input from the logic system.

6. When the clock ceases and CT voltage reaches the RESET ON threshold (

.

=. 1.4V), the output enters into

reset state (RESET

-------------------------------------------------------

becoming "Low").

The CT charging time TWD up until the reset is output (watch dog monitoring time) is expressed by the

following formula:

TWD (ms) .=. 5000 CT (5F)

7. The reset time at the time of watch dog time TWR is the discharging time while the CT voltage lowers down

to the reset off threshold (

.

=. 0.2V). The calculation formula:

TWR (ms) .=. 100 CT (5F)

After the reset off threshold is reached, the output reset is released and CT commences to charge. If

thenceforth the clock is input normally, steps 4 and 5 will be repeated, and setps 6 and 7 repeated if the

clock ceases.

8. When VCC lowers down to VSL (MM1099A .=. 3.2V, MM1099B .=. 4.2V), the reset is output. At the same time

CT charged.

9. CT discharging starts when VCC rises up to VSH.

If VCC lower instantaneously, charging starts after load discharging of CT if the time interval from when VCC

comes lower than VSL up until when it rises to VSH or higher is equal or superior to the reference value of

VCC input pulse width TPI.

10.The output reset is released TPR after VCC becomes VSH or higher, and the watch dog time will start. Then if

VCC becomes VSL or lower, steps 8 to 10 will be repeated.

11.If power Off occurs, reset is output if VCC becomes VSL or lower.

12.When VCC comes down to 0V, the reset output will hold up until VCC becomes 0.8V.





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