Background technology
Optical module is the important active device in the optical communication equipment, for the Electro Magnetic Compatibility (EMC) that guarantees optical module, anti-electromagnetic interference performance (EMI) and antistatic property (ESD), it is metal material that the optical module shell all requires, optical module shell and optical module internal circuit can not be electrically connected, and be electrically connected between the casing of the cabinet at optical module shell and optical module place, and the cabinet casing can be connected to the earth at far-end.Optical module inside mainly is made up of optical assembly (OSA), circuit board assemblies (PCBA), electric signal interface (Electrical Signal Interface) three partial interior circuit, if any one electric signal of this three partial interiors circuit is shorted to the optical module metal shell unusually, light then influence the serviceability or the EMC/EMI/ESD performance of optical module self, heavy then influence the serviceability even the burning apparatus power supply of its place equipment.
The internal circuit of optical module and shell short circuit can be divided into four types unusually: the optical module shell is to the short circuit (CASE is to the VCC short circuit) of optical module power end, perhaps the optical module shell is to optical module bias voltage of avalanche photodiode VAPD terminal shortcircuit (CASE is to the VAPD short circuit), perhaps the optical module shell is to the short circuit (CASE is to the GND short circuit) of optical module earth terminal, perhaps other signal end short circuits of optical module shell and optical module internal circuit unusual (CASE is to the SIGNAL short circuit).Because optical module its shell in batch production process is normally unsettled, be that optical module shell and test board are without any being electrically connected, even optical module exists above certain internal circuit to be shorted to the unusual of shell, optical module also can operate as normal and by performance test.Unusually is example with CASE to the VCC short circuit, in case optical module is assembled on user's the equipment, power supply (VCC) just links to each other with the equipment mainboard by the electric signal interface of optical module with the electric signal pin, then the optical module shell just links to each other with the cabinet casing of user's equipment, because the cabinet casing can connect the earth at far-end, so, will cause VCC to be shorted to the unusual of the earth like this by the optical module shell; If the equipment mainboard does not have suitable power protection mechanism, user's device power supply (DPS) then may burn because of short circuit, even burns mainboard and then initiation fire.So before optical module dispatches from the factory, must guarantee not have short circuit can be considered as non-defective unit through an optical module shell to the short-circuit detecting operation between the internal circuit.
Existing optical module metal shell is to the unusual detection method of the short circuit of internal circuit, mostly be that optical module is installed on the testing host, under the situation that optical module does not power on, manual operations handheld digital multimeter also switches to the resistance test gear, can judge that to the resistance of the VCC pin of optical module electric signal interface is too small shell has been shorted to VCC if test the optical module shell, can judge that to the resistance of the GND pin of optical module electric signal interface is too small shell has been shorted to GND if test the optical module shell, if test the optical module shell to the resistance of other electric signal pins of optical module electric signal interface too small can judge shell with other electric signal pin short circuits of electric signal interface; Under the situation that optical module powers on, manual operations hand-held multimeter also switches to the voltage tester gear, if testing the optical module sheath voltage drops in the VCC voltage range (such as the various supply voltage value ranges of the polynary agreement regulation of optical module as+3.3V ± 10%, + 5.0V ± 10%, + 12.0V ± 10%,-5.0V ± 10%) then may be that shell has been shorted to VCC, if testing the optical module sheath voltage drops in the VAPD voltage range and (such as 20V~60V) then may be that shell has been shorted to VAPD, to drop in the voltage range of other electric signals (such as 0.1V~3.0V) then may be certain electric signal that shell has been shorted to internal circuit if test the optical module sheath voltage.This manual detection method takes time and effort, inefficiency, human factor are many, erroneous judgement easily.
If do not consider to detect cost, can adopt this robotization detection scheme of desk-top multimeter+PC of expensive band DLL (dynamic link library), 2100 digital multimeters such as U.S. Keithely company, the permission PC of this band USB DLL (dynamic link library) sends SCPI (programmable instrument standard commands) by usb bus orders 2100 to carry out telecommunication, has six and half high precision, 11 kinds of measurement functions add mathematics correction and data recording function, it is unit in the quotation of the official website in October, 2010, and is with high costs.The optical module metal shell to the unusual detection of the short circuit of internal circuit, is only needed the resistance value within combined-voltage value within the test 100V and 100 ohm, just seem with 2100 so Full Featured instruments of expensive high precision and wasted one's talent on a petty job.
Summary of the invention
The objective of the invention is at prior art provides a kind of optical module internal circuit and the unusual automatic detection device of shell short circuit detecting the optical module internal circuit to the unusual middle existing problems of shell short circuit.
The objective of the invention is to be achieved through the following technical solutions:
A kind of optical module internal circuit of the present invention and the unusual automatic detection device of shell short circuit, described automatic detection device comprises testing circuit board, the optical module socket that comprises a grafting optical module in the testing circuit board, also being included as the optical module internal circuit provides the optical module power supply of power supply, and the power module that power supply is provided for testing circuit board, described testing circuit board also comprises: the microprocessor of band ADC analog to digital converter, be used to control the open/close state of analog switch, receive the magnitude of voltage of the output of voltage follower, the magnitude of voltage of reception and the short circuit abnormality alarming range of voltage values of setting are compared, export comparative result to warning circuit and show that short circuit is unusual; Analog switch, its voltage input end links to each other with the diode that is connected in series to power module, and its voltage output end links to each other with the metal shell of the optical module that is plugged into the optical module socket, and its break-make is by the control at the microprocessor of being with the ADC analog to digital converter; Voltage follower, the electrode input end of voltage follower is connected by the metal shell of the optical module of pegging graft on electric resistance partial pressure networking and the optical module socket, delivers to the microprocessor of band ADC analog to digital converter after will dwindling from the voltage that the metal shell of optical module is gathered; Warning circuit, the comparative result output signal of the microprocessor of receiving belt ADC analog to digital converter shows short-circuit condition.In the technical scheme of the present invention, also comprise a diode, described diode can be selected common schottky diode B240 for use, and the positive terminal of described diode is connected with power module, and negative pole end is connected with the signal input part of analog switch.
Described warning circuit can adopt multiple display device, considers cost, adopts four LED pipes to show that four kinds of different short circuits are unusual in embodiment of the present invention.Above-mentioned four kinds of short circuits comprise unusually: the optical module metal shell is unusual to the short circuit of optical module internal circuit earth terminal, the optical module metal shell is unusual to the short circuit of optical module internal circuit power end, the optical module metal shell is unusual to optical module internal circuit bias voltage of avalanche photodiode VAPD terminal shortcircuit, and other signal end short circuits of optical module metal shell and optical module internal circuit are unusual.
Above-mentioned electric resistance partial pressure networking comprises the 3rd resistance R 3 and the 4th resistance R 4 of series connection, the 3rd resistance R 3 is connected with the electrode input end of voltage follower 14 with the link of the 4th resistance R 4, the metal shell of the optical module of pegging graft on the other end of the 3rd resistance R 3 and the optical module socket 12 is connected the other end ground connection of the 4th resistance R 4.As preferably, the resistance value of the 3rd resistance R 3 is 845.0K Ω, and the resistance value of the 4th resistance R 4 is 27.0 K Ω.
Because the present invention adopts technique scheme, so the present invention can reach following beneficial effect: circuit structure of the present invention is simple, and is cheap with respect to expensive 2100 digital multimeters; The efficient height is finished the unusual testing of optical module short circuit automatically under the control of the microprocessor of being with the ADC analog to digital converter; Reduce manually-operated in the prior art because the erroneous judgement that human factor causes.
Embodiment
Disclosed all features in this instructions, or the step in disclosed all methods or the process except mutually exclusive feature and/or step, all can make up by any way.
Disclosed arbitrary feature in this instructions (comprising any accessory claim, summary and accompanying drawing) is unless special narration all can be replaced by other equivalences or the alternative features with similar purpose.That is, unless special narration, each feature is an example in a series of equivalences or the similar characteristics.
As Fig. 1 be in the specific embodiments of the present invention optical module internal circuit to the hardware components principle schematic of the short-circuit detecting device of shell.A kind of optical module internal circuit and the unusual automatic detection device of shell short circuit, described automatic detection device comprises testing circuit board 1, the optical module socket 12 that comprises a grafting optical module in the testing circuit board 1, also being included as the optical module internal circuit provides the optical module power supply 3 of power supply, and the power module 2 that power supply is provided for testing circuit board, described testing circuit board also comprises: analog switch 11, circuit dividing potential drop networking 13, voltage follower 14, the microprocessor 15 of band ADC analog to digital converter, circuit warning circuit 16, diode 17.
The microprocessor 15 of band ADC analog to digital converter, be used to control the open/close state of analog switch 11, receive the magnitude of voltage of the output of voltage follower 14, the magnitude of voltage of reception and the short circuit abnormality alarming range of voltage values of setting are compared, export comparative result to warning circuit 16 and show that short circuits are unusual.The microprocessor of band ADC analog to digital converter can be selected the ADUC7020 of Analog Devices company for use, it has high Precision Processing device ARM7TDMI nuclear, a plurality of D and D/A converter passage, can satisfy demand of the present invention fully, but also can use for other module on the testing circuit board.
Analog switch 11, its voltage input end links to each other with the diode 17 that is connected in series to power module 2, and its voltage output end links to each other with the metal shell of the optical module that is plugged into optical module socket 12, and its break-make is by the control at the microprocessor 15 of being with the ADC analog to digital converter.Analog switch can be selected the TS5A4595 switch chip of U.S. Texas Instruments company for use, because the present invention judges short circuit phenomenon according to gathering different magnitudes of voltage, the connection resistance of TS5A4595 is 8 ohm, almost can ignore its pressure drop in the present invention, and the time that switches on and off of TS5A4595 switch be respectively 17ns and 14ns, can satisfy requirement of the present invention.
Voltage follower 14, voltage follower 14 used amplifiers can be selected the AD8541 of Analog Devices company for use.The electrode input end of voltage follower 14 is connected by the metal shell of the optical module of pegging graft on electric resistance partial pressure networking 13 and the optical module socket 12, delivers to the microprocessor 15 of being with the ADC analog to digital converter after will dwindling from the voltage that the metal shell of optical module is gathered.Described electric resistance partial pressure networking 13 comprises the 3rd resistance R 3 and the 4th resistance R 4 of series connection, the 3rd resistance R 3 is connected with the electrode input end of voltage follower 14 with the link of the 4th resistance R 4, the metal shell of the optical module of pegging graft on the other end of the 3rd resistance R 3 and the optical module socket 12 is connected the other end ground connection of the 4th resistance R 4.In an embodiment of the present invention, the resistance value of the 3rd resistance R 3 is 845.0K Ω, and the resistance value of the 4th resistance R 4 is 27.0 K Ω.
Warning circuit 16, the comparative result output signal of the microprocessor 15 of receiving belt ADC analog to digital converter shows short-circuit condition.In the short circuit abnormality test of optical module, four kinds of short circuits of main test are unusual, be that the optical module metal shell is unusual to the short circuit of optical module internal circuit earth terminal, the optical module metal shell is unusual to the short circuit of optical module internal circuit power end, the optical module metal shell is unusual to optical module internal circuit bias voltage of avalanche photodiode VAPD terminal shortcircuit, and other signal end short circuits of optical module metal shell and optical module internal circuit are unusual.Therefore, as preferably, four kinds of short circuits of the present invention can adopt four LED pipes to be shown that circuit structure is simple unusually, and the unusual kind of short circuit also is easy to identification.
In the embodiments of the invention, also comprise diode 17, the positive terminal of described diode 17 is connected with power module 2, and negative pole end is connected with the signal input part of analog switch 11.Described diode 17 is selected the special based diode B240 of Xiao Putong, its forward voltage drop V for use
fRepresentative value is 0.5V.
Of the present invention be in the example, the output voltage of its power module 2 is 3.3V.
The present invention is based on Automatic Control Theory, and the break-make of the microprocessor control analog switch by band ADC analog to digital converter detects the optical module metal shell respectively over the ground with to power supply, VAPD short circuit abnormality detection.Below in conjunction with embodiments of the invention, describe automatic testing method of the present invention in detail.
After optical module to be measured is plugged on the optical module socket 12, start automatic detection device.
1. optical module shell shorted to earth detects
Behind the automatic detection device electrifying startup, 15 low level signals of microprocessor of band ADC analog to digital converter are given analog switch 11, analog switch 11 closed conductings.At this moment, the power module 2 of 3.3V adds certain voltage for the metal shell (case) of optical module through diode 17.If the metal shell of optical module (case) (GND) short circuit over the ground, what then the voltage on the optical module metal shell (case) will be drawn is very low, basic is 0V, the metal shell of optical module (case) is sent to the ADC analog to digital converter of the microprocessor 15 of being with the ADC analog to digital converter by voltage follower 14 magnitude of voltage Vcase also is 0V substantially, gathers this moment less than magnitude of voltage; If not (GND) short circuit over the ground of the metal shell of optical module (case), then the magnitude of voltage of the metal shell (case) of optical module is at this moment:
Vcase=Vcc-V
f
=3.3V-0.5V (1)
=2.8V
Send into voltage follower 14 behind the voltage Vcase process electric resistance partial pressure networking 13 of the metal shell of optical module (case), the voltage of voltage follower 14 input ends is:
The microprocessor 15ADC analog to digital converter that voltage after voltage follower 14 will drive is sent to band ADC analog to digital converter carries out sampling analysis.So, after 15 low level signals of microprocessor of band ADC analog to digital converter are given analog switch 11, if the magnitude of voltage that collects is a near value (87mV ± 10%) 87mV or the 87mV, then the metal shell (case) of explanation optical module this moment does not have shorted to earth, if gather less than magnitude of voltage, metal shell (case) shorted to earth of optical module this moment has been described, and this information has been embodied by warning circuit 16.
2. the metal shell of optical module (case) is to power supply, VAPD short-circuit detecting
15 high level signals of microprocessor of band ADC analog to digital converter are given analog switch 11, and analog switch 11 disconnects and is in off state.At this moment, if the metal shell of optical module (case) is not to the internal circuit short circuit of optical module, then the metal shell of optical module (case) does not add any voltage, the voltage of the metal shell of optical module (case) is sent to the ADC analog to digital converter of the microprocessor 15 of being with the ADC analog to digital converter by voltage follower 14 magnitude of voltage also is 0V substantially, and this moment, the ADC analog to digital converter was gathered less than magnitude of voltage; If the metal shell of optical module (case) is to power module 2 short circuits of 3.3V, then the magnitude of voltage of the metal shell (case) of optical module is 3.3V at this moment, by the magnitude of voltage of sending into voltage follower 14 behind the electric resistance partial pressure networking 13 is:
The sampled voltage that is sent to the ADC analog to digital converter of the microprocessor 15 of being with the ADC analog to digital converter this moment also is 102mV.
If the metal shell of optical module (case) is to the VAPD short circuit, if the VAPD voltage range is 20V~60V, then this moment optical module the magnitude of voltage of CASE also in 20V~60V, by the magnitude of voltage of sending into voltage follower 14 behind the electric resistance partial pressure networking 13 be:
The sampled voltage of the ADC analog to digital converter of the band ADC analog to digital converter microprocessor 15 that be sent to this moment also is 619mV~1.86V.
So, after 15 high level signals of microprocessor of band ADC analog to digital converter are given analog switch 11, if the microprocessor 15 of band ADC analog to digital converter is gathered less than magnitude of voltage, then the metal shell (case) of explanation optical module this moment does not have short circuit with internal circuit; If the magnitude of voltage that collects is (102mV ± 10%) near 102mV, metal shell (case) that optical module this moment is described is to power module 2 short circuits of 3.3V; If the magnitude of voltage that collects is 0.5V~2.0V, the metal shell (case) that optical module this moment is described is to the VAPD short circuit; If the magnitude of voltage that collects is other numerical value, other signal end short circuits of metal shell (case) optical module internal circuit of optical module this moment have been described.Magnitude of voltage about collection is the situation of other values, if sample 50mV, the original signal magnitude of voltage that conversion is gone back is 50/27* (27+845)=1.6V, and it may be the RD signal pin voltage of APD optical assembly; If sample 70mV, the original signal magnitude of voltage that conversion is gone back is 70/27* (27+845)=2.3V, and it may be the I/O pin voltage of the logic chip of 3.3V CMOS power supply; There is nonlinearity erron when considering the ADC analog to digital converter to the small voltage signal sampling, usually less than 5 LSB, ADuC7020 is exactly 5/4096*2.5=3mV through calculating, so, put some surpluses, if sample magnitude of voltage for greater than 10mV, other signal end short circuits of metal shell (case) optical module internal circuit of optical module this moment could be described.
3. the microprocessor 15 of band ADC analog to digital converter is analyzed these different sampled values and is embodied by warning circuit 16.Promptly represent four kinds of different short-circuit conditions intuitively to show respectively by four LED pipes.
The present invention is not limited to aforesaid embodiment.The present invention expands to any new feature or any new combination that discloses in this manual, and the arbitrary new method that discloses or step or any new combination of process.