MB3773
22
EXAMPLE 10: Circuit for Monitoring Multiple Microprocessor
VCC ( = 5 V)
1
2
3
4
8
7
6
5
CT
MB3773
RESET
RESET
CK
GND
Notes : connects from FF1 and FF2 outputs Q1 and Q2 to the NOR input.
Depending on timing, these connections may not be necessary.
Example : R
1 = R2 = 2.2 k
C
T = 0.1 µF
RESET
RESET
CK
GND
RESET
RESET
CK
GND
S
D
3
CK3
R
Q
3
Q3
S
D2
CK2
R
Q
2
Q2
S
D
1
CK1
R
Q
1
Q1
FF3FF2FF1
R2
R1
CK1
Q1
CK2
Q2
CK3
Q3
NOR
Output
Figure 1
Figure 2
***
*: Microprocessor
MB3773
23
Description of Application Circuits
Using one MB3773, this application circuit monitors multiple microprocessor in one system. Signals from each
microprocessor are sent to FF1, FF2 and FF3 clock inputs. Figure 2 shows these timings. Each flip-flop operates
using signals sent from microprocessor as its clock pulse. When even one signal stops, the relevant receiving
flip-flop stops operating. As a result, cyclical pulses are not generated at output Q
3. Since the clock pulse stops
arriving at the CK terminal of the MB3773, the MB3773 generates a reset signal.
Note that output Q
3 frequency f will be in the following range, where the clock frequencies of CK1, CK2 and CK3
are f1, f2 and f3 respectively.
where f
0 is the lowest frequency among f1, f2 and f3.
1
f
0
----
1
f
---
1
f
1
----
1
f
2
----
1
f
3
----
++≤≤
MB3773
24
CRT1
0.01 µF10 k 30 µs
0.1 µF10 k 300 µs
EXAMPLE 11: Circuit for Limiting Upper Clock Input Frequency
Notes : This is an example application to limit upper frequency f
H of clock pulses sent from
the microprocessor.
If the CK cycle sent from the microprocessor exceeds f
H, the circuit generates a reset signal.
(The lower frequency has already been set using C
T.)
When a clock pulse such as shown below is sent to terminal CK, a short T
2 prevents C2 voltage
from reaching the CK input threshold level ( := 1.25 V), and will cause a reset signal to be output.
The T
1 value can be found using the following formula :
Example : Setting C and R allow the upper
T1 value to be set (Refer to the table below).
VCC (5 V)
1
2
3
4
8
7
6
5
CT
RESET
RESET
CK
GND
R2
R1=10 k
C2
Tr1
T1 := 0.3 C2R2
T2
CK waveform
T3
C2 voltage
T1
where VCC = 5 V, T3 3.0 µs, T2 20 µs

MB3773PF-G-BND-JN-ERE1

Mfr. #:
Manufacturer:
Fujitsu
Description:
IC PWR SUPPLY MON W/WD 8SOP
Lifecycle:
New from this manufacturer.
Delivery:
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