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MITSUBISHI
M5295AL/P/FP
WATCHDOG TIMER
DESCRIPTION
M5295A is a semiconductor integrated circuit which is designed for System Reset to detect +5V power supply. This IC keeps the operation microcomputer watching. When the system is abnormal,it generates Reset output until the system returns to normal states of the System. It is possible to vary the two detective voltage by connecting the resistor,so it is suitable to high quality and high performance system.
PIN CONFIGURATION (TOP VIEW)
8 7 6 5 4 3 2 1
ADJ2 RST2 Vcc ADJ1 GND RST1 TC WD
FEATURES
*Watch Dog Timer *Power on Reset Timer *Low circuit current 0.8mA(Typ,Vcc=5V) *Wide Range of power supply
Outline 8P5(AL) WD TC RST1
1 2 3 4 8 7 6 5
APPLICATION
Microcomputer Systems
ADJ2 RST2 Vcc ADJ1
RECOMMENDED OPERATING CONDITIONS
Supply voltage...........................................4V to 15V Rated supply voltage............................................5V
GND
Outline 8P4(AP) 8P2S-A(AFP)
BLOCK DIAGRAM
49.6k
51.2k
F.F F.F
+
-
+
+
-
20.4k
18.8k
W.D.T F.F
20k 30k 1.24V
REFERENCE VOLTAGE GENERATOR CIRCUIT
1 WD
2 TC
3 RST1
4 GND
5 ADJ1
6 Vcc
7 RST2
8 ADJ2
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MITSUBISHI
M5295AL/P/FP
WATCHDOG TIMER
ABSOLUTE MAXIMUM RATINGS (Ta=25C,unless otherwise noted)
Symbol Vcc VIN VOUT IOUT Pd K Topr Tstg Parameter Supply voltage Input voltage Output voltage Output current Power dissipation Thermal derating Operating temperature Storage temperature Ta25C Conditions Ratings 15 -10 to +10 15 10 800(SIP)/625(DIP)/440(FP) 8(SIP)/6.25(DIP)/4.4(FP) -20 to +75 -55 to +125 Unit V V V mA mW mW/C C C
ELECTRICAL CHARACTERISTICS (Ta=25C,Vcc=5V,unless otherwise noted) (1)DC FEATURES
Symbol IIH IIL VIH VIL IOUT IIN VVH3(H) VVH3(L) VOL ILEAK VTH1 VTH2(H) VTH2(L) VTH2 V5 V8 RST1 RST2 Icc ADJ1 voltage ADJ2 voltage RST1 on voltage RST2 on voltage Circuit current ADJ1 ADJ2 RST1 RST2 Vcc Vcc=1.2V,RL=4.7k Vcc=1.2V,RL=4.7k 0.8 Vcc detective voltage(2) Vcc Output voltage Output leak current Vcc detective voltage(1) Parameter WD input current Pin WD VIN=5V VIN=-5V WD input voltage TC output current TC input current Threshold voltage of watch dog timer WD TC TC TC RST1 RST2 Vcc IOUT=1mA VOUT=15V 4.05 4.5 4.45 0.05 1.17 1.07 4.25 4.7 4.6 0.1 1.46 1.34 VIN=1.5V VOUT=4.2V 3.7 1.7 3.3 4 2 0.1 4.3 2.3 0.5 5 4.45 4.9 4.75 0.2 1.75 1.61 0.5 0.5 1.5 Test conditions Min. 0.06 0.05 2 0.8 -1 Limits Typ. 0.15 -0.1 Max. 0.25 -0.15 Unit mA mA V V A mA V V V A V V V V V V V V V
(2)AC FEATURES
Symbol tWD Parameter Watch dog timer Pin RST1 C=0.1F,R1=10k tRST(1) Reset timer (1) RST1 C=0.1F,R1=10k RST1 WD RST1 RST2 R1=10k C=0.1F,R1=10k tWD IN td1 td2 Transmittal delay time Input pulse watch 40 3 20 10 0.2 0.5 Test conditions Min. Limits Typ. 1.1*C*R1 1.1 0.5*C*R1 0.5 830*C 83 220 1.1 1.7 Max. Unit s ms s ms s s s s s
tRST(2)
Reset timer (2)
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MITSUBISHI
M5295AL/P/FP
WATCHDOG TIMER OPERATING EXPLANETION
Vcc
VTH2(H) VTH1 0V VTH2(L) VTH1
VTH3(H) VTH3(L)
TC
0V
VIN
0V
RST1
0V
RST2
0V
tRST(1)
tWD
tRST(2)
12 3
4
5
6
78
9 10 11
1 The Vcc rises up to 0.8V,then Reset1 and 2 generate Low output,and Rising up to 4.25V,charge of C1 begins. 2 The Vcc rises up to 4.7V,then Reset2 generates high. 3 , 4 The voltage at TC pin is 2V,then Reset2 generates high,when 4V,C1 is discharged and Reset1 generates Low. 5 The voltage at TC pin falls to 2V,then Reset1 generates high unless normal clock signal is entered to WD pin,Reset1 repeats this operation. 7 Before the voltage at TC pin reaches 4V,if normal 6, clock signal is entered to WD pin,Low Reset1 is canceled.
8 , 9 In the case of entrance of abnormal signal input, as the waveform of TC pin repeats charge and discharge of Reset1 alternatively from 2V to 4V,the Reset1 repeats high and low output operation. 10 The Vcc falls to 4.6V,then Reset2 generates Low, this detective voltage has a 100mV hysteresis. 11 When Vcc goes down to 4.25V(VTH1),the status of TC pin is switched to discharge.When the potentional at TC pin is detected being VTH3(H) or VTH3(L),the status of Reset1 becomes "low".
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MITSUBISHI
M5295AL/P/FP
WATCHDOG TIMER TERMINOLOGY
tRST1:Time required for TC pin potential to rise from 0V VTH3(L) when Vcc is being applied. tWD: Time required for TC pin potential to rise from VTH3(L) to VTH3(H). tRST2:Time required for TC pin potential to go down from VTH3(H) to VTH3(L).
2.Pin 1 (WD Pin) Input Frequency, Input Pulse Width,Charge Time and Discharge Time
When input to WD pin 1 is normal,TC pin 2 output waveform is as shown below: (Vcc=5V) 4V Pin 2 xV
1.Pin 2 (TC Pin) Charge Time and Discharge Time
When input to WD pin is abnormal,TC pin output waveform is as shown below: 4 *Vcc 5 TC 0V 2 *Vcc 5 t1=C*R1*in tRST(1) tRST(2) t2=1000*C*in -1 (discharge time) -3 Input
2V t1 t2
tWDIN 3 (charge time) 5-x R1 1000 2* +1 x-5 (discharge time) -3
tWD
tRST(1)=0.51*C*R1 tWD=1.1*C*R1(charge time) 4* R1 tRST(2)=1000*C*in 1000 2* R1 1000
R1 1000
Vcc R1 2 C
PIN 1 (WD PIN)INPUT REQUIREMENTS (1)Connect capacitor between WD pin and voltage input. (Refer to Section 3.) (2)Input cycle:No more than tWD (Discharge should start before voltage at WD pin reaches 4V.) 1 Resistance R1:10kR130k When R1 is 10k,tRST(2) is 830*C. C=103 100s
Vcc=5V R1=10k 50s 0.5 ms
t2 4 3 2 DISCHARGE VOLTAGE x(V)
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MITSUBISHI
M5295AL/P/FP
WATCHDOG TIMER 3.Relationship between Input Pulse Width and Input Capacitance Cin
When input to pin 1 is 1.5V or more,TC pin discharges electricity. Determine pulse width and input capacitance Cin with reference to the diagram shown on the right. Vin VIN Vin WD 1 1.5V t3 tWD 4V 2V t t4 t
VIN 1 Cin
30k 20k
TC 2 Q1 RST1 3
t
t
Q1 is off when voltage at pin 1 is 1.5V or less. t3=Cin*5X10 4 *In Vin 1.5 RST1 is output when t4 is longer than tWD.
Cin:10.000pF,t3=0.6ms Cin:1000pF,t3=0.6s Cin:100pF,t3=6s When t3 is too long,TC pin output waveform frequency changes as shown above.Set t3 to be sufficiently long to turn on Q1[tWDIN(3s)or more] but not to exceed t2(Discharge time). (t2:Discharge time during normal input)
VTH1(V) R1(k)
R2(k)
Detection voltage calculation formula VTH1= R01+R02 X1.24(V) R02 R01=R1//49.6k R02=R2//20.4k
4.Vcc Detection Voltage Adjustment (1)Detection voltage 1(VTH1)adjustment.
13 10 7 5 4.25
10 10 10 10 10.90 8.59
0.92 1.25 1.96 3.17 5 5
6 R1 5 R2 20.4k 1.24V 49.6k + RL
4 3.5
-
3
To adjust detection voltage 1,determine external resistance with the following equation: a. VTH>4.25V(R1=10k) R2= 1 1 R0 1 20.4k R0= 8.322kX1.24 VTH1-1.24
4
b. VTH1<4.25V(R2=5k) R1= 1 1 R0 1 49.6k R0= (VTH1-1.24)4.016k 1.24
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MITSUBISHI
M5295AL/P/FP
WATCHDOG TIMER
(2)Detection voltage 2(VTH2(L))adjustment
VTH2(L)(V)
R3(k)
R4(k)
VTH2(mV)
Detection voltage calculation formula VTH2(L)= R03+R04 X1.24(V) R04 R03=R3//51.2k R04=R4//18.8k VTH2= R03 51.2k X100(mV)
13 10 6 R3 5 R4 18.8k 1.24V 4 51.2k + RL 7 5 4.6 4 7 3.5
10 10 10 10 10.61 8.38
0.93 1.26 1.99 3.24 5 5
16.3 16.3 16.3 16.3 100 17.2 14.1
-
To adjust detection voltage 2,determine external resistance with the following equations: a. VTH2(L)>4.6V(R3=10k) R4= 1 1 R0 1 18.8k R0= 8.37kX1.24 VTH2(L)-1.24
APPLICATION EXAMPLE
b. VTH2(L)<4.6V(R4=5k) R3= 1 1 R0 1 51.2k R0= (VTH2(L)-1.24)3.95k 1.24
M5295AL
1
2
3
4
5
6
7
8
CLOCK
RST1 (RESET) MCU/MPU
RST2 (HOLD) VDD Example of Backup Circuit with M5295AL
OPERATION INSTRUCTIONS
1.When malfunction occurs due to noise or other related trouble,connect capacitance of approximately 1000pF between pin 5 and GND as well as pin 8 and GND to stabilize operation. 2.To adjust detection voltage,add resistance of 15k or less to both Vcc and GND via adjusting pins. (Set detection voltage to no less than 3V.) 3.Set tWD and tRST(2) as shown below: 110stWD1.1s 8.3stRST(2)83ms 10kR130k 4.Input clock pulses to pin 1 via capacitor.To determine capacitance,refer to "Relationship between Input Pulse Width and Input Capacitance Cin".
BACKUP POWER SUPPLY
M5295AL
10K
1 2 3 4 5 6 7 8
3.5V R4
R3
Backup switching voltage TO SYSTEM VTH(L) Switching voltage calculation formula
Vcc
RESET OUTPUT
VTH2(L)= R03+R04 X1.24 R04 R03=R3//51.2k R04=R4//18.8k (Note)Set backup switching voltage to be more than or equal to backup supply voltage.
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MITSUBISHI
M5295AL/P/FP
WATCHDOG TIMER
TYPICAL CHARACTERISTICS
THERMAL DERATING (MAXIMUM RATING) DETECTION VOLTAGE VS. SUPPLY VOLTAGE
1000
M5295AL
4.9 4.8 VTH2(H)
M5295AP
800 4.7 4.6
M5295AFP
600 400 200 0
4.5 4.4 4.3 4.2
VTH2(L)
VTH1
0
25
50
75
100
125
4.1 -40 -20 0
20 40 60 80 100 120
AMBIENT TEMPERATURE Ta(C) CIRCUIT CURRENT VS. SUPPLY VOLTAGE
AMBIENT TEMPERATURE Ta(C) INTERRUPTION OUTPUT VOLTAGE VS. CIRCUIT CURRENT
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -40 -20 0 20 40 60 80 100 120 Vcc=5V
4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 0 2
(Icc FLUCTUATION CAUSED BY CIRCUIT OPERATION)
RL=4.7k
RST1 High RST2 High
4
6
8 10 12 14 16
AMBIENT TEMPERATURE Ta(C) CRITICAL OPERATION VOLTAGE CHARACTERISTICS
SUPPLY VOLTAGE Vcc(V) DELAY TIME VS.DELAY CAPACITY CHARACTERISTICS
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
100
7 5 3 2 7 5 3 2
Vcc=5V tWD(R1=10k)
10 RL=2.2k RL=22k RL=100k 1
tRST2
7 5 3 2
0.1 7
5 3 2 3 57
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
SUPPLY VOLTAGE Vcc(V)
0.01 2 0.01
0.1
2 3 57
1
2 3 57
10
2 3 57
100
DELAY CAPACITY C(F)
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MITSUBISHI
M5295AL/P/FP
WATCHDOG TIMER
OUTPUT SATURATION VOLTAGE VS. AMBIENT TEMPERATURE OUTPUT SATURATION VOLTAGE VS. LOAD CURRENT
0.4 Vcc=5V RL=4.7k 0.3
1.6 1.4 Vcc=5V 1.2 1.0
0.2
0.8 0.6
0.1
0.4 0.2
0 -40 -20
0
20 40 60 80 100 120
0 0.1
2 3 57
1
23
57
10
2 3 57
100
AMBIENT TEMPERATURE Ta(C)
LOAD CURRENT IOUT(mA)
WATCHDOG TIMER THRESHOLD VOLTAGE VS. AMBIENT TEMPERATURE
8 7 6 5 4 3
PIN TC INPUT CURRENT VS. AMBIENT TEMPERATURE
8 Vcc=5V 7 6 5 VTH3(H) 4 VTH3(L) 3 2 1 0 20 40 60 80 100 120 0 -40 -20 0 20 40 60 80 100 120 Vcc=5V
2 1 0 -40 -20
AMBIENT TEMPERATURE Ta(C)
AMBIENT TEMPERATURE Ta(C)
WATCHDOG TIMER VS. AMBIENT TEMPERATURE
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -40 -20 0 20 40 60 80 100 120 Vcc=5V C=0.1F R1=10k
RESET TIMER(2) VS. AMBIENT TEMPERATURE
320 280 240 200 160 120 80 40 0 -40 -20 0 20 40 60 80 100 120 Vcc=5V C=0.1F
AMBIENT TEMPERATURE Ta(C)
AMBIENT TEMPERATURE Ta(C)
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