Electric power conversion systems – Current conversion – Including automatic or integral protection means
Reexamination Certificate
2002-08-05
2004-02-03
Nguyen, Matthew V. (Department: 2838)
Electric power conversion systems
Current conversion
Including automatic or integral protection means
Reexamination Certificate
active
06687140
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disconnection detecting circuit which judges whether there is a disconnection or not in a signal line connecting a micro processor and an IC or a sensor which are used with high reliability at the same time in environments accompanied by vibration, such as in planes and automobiles.
2. Description of Related Art
FIG. 10
is an explanatory diagram to show one example of a conventional disconnection detecting circuit. Reference numeral
1
denotes a device having a disconnection detecting circuit, such as a micro processor, reference sign
1
a
denotes a body of the device
1
, i.e., IC package, reference numeral
2
denotes a lead member provided in the IC package
1
a,
reference numeral
3
denotes an IC chip on which an integrated circuit is formed, reference numeral
4
denotes a bonding wire for connecting the lead member
2
and the IC chip
3
, reference numeral
5
denotes a bonding pad connected to the lead member
2
with the bonding wire
4
, reference numeral
6
denotes an output buffer which is a constituent of the integrated circuit formed on the IC chip
3
, reference numeral
7
denotes an input buffer which is a constituent of the integrated circuit formed on the IC chip
3
, reference numeral
8
denotes a peripheral device such as an integrated circuit device (hereinafter referred to as “IC”) or a sensor, which is connected to the device
1
and reference numeral
9
denotes a signal line for connecting the device
1
and the peripheral device
8
.
Next, an operation of the disconnection detecting circuit will be discussed.
Discussion will be made on a disconnection detecting circuit in which the device
1
and the peripheral device
8
are connected with the signal line
9
as an exemplary conventional one. In advance a predetermined signal or signal level is set in the peripheral device
8
as an expected value. The peripheral device
8
outputs the expected value signal to the signal line
9
like an ordinary transmit data, to transmit it to the device
1
. The device
1
judges whether the received expected value signal coincides with the signal or signal level set in advance or not, for judgment on whether there is a disconnection or not in the signal line
9
.
FIG. 11
is an explanatory diagram to show another example of conventional disconnection detecting circuit. The disconnection detecting circuit shown in
FIG. 11
is intended for judgment on whether there is a disconnection or not in the signal line
9
without outputting the expected value signal from the peripheral device
8
, and constituent elements thereof identical to or corresponding to those of the disconnection detecting circuit of
FIG. 10
are denoted by the same reference signs and further description thereon will be omitted. In
FIG. 11
, reference numeral
10
denotes a resistor loaded on the signal line
9
and reference numeral
11
denotes wiring capacitance generated in the signal line
9
which connects the peripheral device
8
and the device
1
.
Next, an operation of the disconnection detecting circuit will be discussed.
The disconnection detecting circuit shown in
FIG. 11
detects disconnection by accumulating electric charges in the following procedure. To begin with, a predetermined signal is temporarily output from the output buffer
6
of the device
1
to the signal line
9
. Then, the electric charges are accumulated in the wiring capacitance
11
of the signal line
9
. After that, the output of the output buffer
6
is stopped and a given period later, the signal input to the device
1
through the lead member
2
is observed. From this observation result, it is judged whether there is a disconnection or not as follows. The observation is made on the output side of the input buffer
7
.
1. When a signal of high level (hereinafter referred to as “H”) is temporarily output from the output buffer
6
and H electric charges are accumulated in the wiring capacitance
11
, judgment is made as follows:
i) If the output of the input buffer is H, there is a possibility of disconnection.
ii) If the output of the input buffer is low level (hereinafter referred to as “L”), there is no possibility of disconnection.
This judgment on whether there is a disconnection or not, is made from a fact that if a terminal voltage of the peripheral device
8
connected to the signal line
9
is L, when an H signal is output from the output buffer
6
of the device
1
to the signal line
9
for a given period and stopped, the potential of the signal line
9
falls from H level and converges on the terminal voltage of the peripheral device
8
.
2. When an L signal is temporarily output from the output buffer
6
and L electric charges are accumulated in the wiring capacitance
11
, judgment is made as follows:
i) If the output of the input buffer is H, there is no possibility of disconnection.
ii) If the output of the input buffer is L, there is a possibility of disconnection.
This judgment on whether there is a disconnection or not, is made from a fact that if the terminal voltage of the peripheral device
8
connected to the signal line
9
is H, when an L signal is output from the output buffer
6
of the device
1
to the signal line
9
for a given period and stopped, the potential of the signal line
9
rises from L level and converges on the terminal voltage of the peripheral device
8
.
When it can be judged that there is a possibility of disconnection in both cases of the above items 1 and 2, it is supposed that disconnection occurs between the resistor
10
and the device
1
. Further, when it is judged that there is no possibility of disconnection in either case of the above item 1 or 2, it can be judged that disconnection does not occur between the resistor
10
and the device
1
.
That is, if the electric charges output from the output buffer
6
are accumulated in the wiring capacitance
11
for a longer time than a predetermined period, it is judged that disconnection occurs in the signal line
9
and if the electric charges accumulated in the wiring capacitance
11
are not detected at the output of the input buffer
7
by a drive of the peripheral device
8
connected to the device
1
through the resistor
10
in either item 1 or 2, it is judged that the signal line is normally connected. Further, when the output of the input buffer
7
is read, the output of the output buffer
6
should be brought into a high impedance state so that it does not affect data to be measured which are output from the peripheral device
8
.
Since the conventional disconnection detecting circuit has the above constitution, it is possible to perform a relatively easy detection of disconnection in the signal line or the like when the peripheral device has a function of outputting the expected value signal set in advance. However, when the peripheral device has no function of outputting the expected value signal, the resistor is inserted in the signal line as shown in FIG.
11
and it is indirectly judged whether disconnection occurs in the signal line, using the characteristics that the wiring capacitance holds the electric charges for a given period. In this case, the time period while the electric charges are accumulated in the wiring capacitance and the length of time until the electric charges accumulated in the wiring capacitance are observed are closely related to a lot of factors, such as the resistance value of the resistor, the output characteristics of the peripheral device, the value of the wiring capacitance and the characteristics of the output buffer and the input buffer provided in the device, and they can not be uniquely determined. This causes a problem that the resistance value of the resistor, the output time of the output buffer and the length of time until the electric charges accumulated in the wiring capacitance are observed should be determined, with repeated trial and error after the circuit employing the device and the peripheral device are completed.
SUMMARY OF THE INVENTION
The pre
Burns Doane , Swecker, Mathis LLP
Nguyen Matthew V.
LandOfFree
Disconnection detecting circuit detecting disconnection... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Disconnection detecting circuit detecting disconnection..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Disconnection detecting circuit detecting disconnection... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3309530