FMEA WORKSHEET

 

FXO INC. Analysis of a Dual Computer with Interface Unit FMEA

 

Item / Function

Potential Failure Mode

Potential Effect(s) of Failure

Severity Classification

Potential Cause(s) Mechanism(s) of Failure

C1

Power Supply Regulation

Open Ckt

Poor Regulation on the Vdd bus. Output of MUX_A signals subject to ringing and droop

IV: Minor

Internal failure, Broken lead, Broken solder joint

 

Short Ckt

No output from MUX_A. CONTROL_A signal is stuck low. Inputs signals to MUX_A are also shorted low through the input diodes on the MUX_A inputs. This causes a mission critical failure.

I: Catastrophic, loss of both Computer 1 and Computer2 Control signals

Electromigration causing capacitor electrodes to short.

 

Change in Capacitance/ Drift

Poor Regulation on the Vdd bus

IV: Minor

Electromigration causes capacitance to change. Or component degrading.

C2

Power Supply Regulation

Open Ckt

Poor Regulation on the Vdd bus. Output of MUX_A signals subject to ringing and droop

IV: Minor

Internal failure, Broken lead, Broken solder joint

 

Short Ckt

No output from MUX_B. CONTROL_A signal is stuck low. Inputs signals to MUX_B are also shorted low through the input diodes on the MUX_B inputs. This causes a mission critical failure.

I: Catastrophic, loss of both Computer 1 and Computer2 Control signals

Electromigration causing capacitor electrodes to short.

 

Change in Capacitance/ Drift

Poor Regulation on the Vdd bus

IV: Minor

Electromigration causes capacitance to change. Or component degrading.

MUX_A Computer control signal multiplexing

Short circuit between any two adjacent connections

Pin 1 and Pin 2: The control signals from the redundant computers are shorted. Mission Critical Failure

I: Catastrophic, loss of both Computer 1 and Computer2 Control signals

Bent pin, broken trace, foreign substance causing the short.

 

Short circuit between any two adjacent connections

Pin 2 and Pin 3: The control signal from Computer 2 is shorted to the MUX_A output. Causes loss of redundancy

II: Loss of Redundancy: Can't use Computer 2 or IU bus A

Bent pin, broken trace, foreign substance causing the short.

 

Open circuit on any pin

Pin 1, or 2 or 3: Loss of the Computer control logic on Side A

II: Loss of Redundancy: Can't use Bus A

Bent pin, broken trace, foreign substance causing the short.

 

Input or output stuck hi or low

Pin 1: Stuck input will also be stuck on the MUX_B input. Causes loss of Computer 1.

II: Loss of Redundancy: Can't use Computer 1

Bent pin, broken trace, foreign substance causing the short.

 

Input or output stuck hi or low

Pin 2: Stuck input will also be stuck on the MUX_B input. Causes loss of Computer 2.

II: Loss of Redundancy: Can't use Computer 2 or IU bus A

Bent pin, broken trace, foreign substance causing the short.

 

Input or output stuck hi or low

Pin 3: Stuck output, causes loss of Bus A

II: Loss of Redundancy: Can't use Bus A

Bent pin, broken trace, foreign substance causing the short.

 

Simultaneous short on all connections

All the pins on the chip are shorted together

I: Catastrophic, loss of both Computer 1 and Computer2 Control signals

Internal chip failure.

 

Output signal varies by >25%

Pin 3: output varies by >25%, may cause loss of Bus A

II: Loss of Redundancy: Can't use Bus A

Internal chip failure.

 

Parasitic oscillation of outputs

Pin 3: Output oscillates, causes loss of Bus A

II: Loss of Redundancy: Can't use Bus A

Internal chip failure.

MUX_B Computer control signal multiplexing

Short circuit between any two adjacent connections

Pin 1 and Pin 2: The control signals from the redundant computers are shorted. Mission Critical Failure

I: Catastrophic, loss of both Computer 1 and Computer2 Control signals

Bent pin, broken trace, foreign substance causing the short.

 

Short circuit between any two adjacent connections

Pin 2 and Pin 3: The control signal from Computer 2 is shorted to the MUX_B output. Causes loss of redundancy

II: Loss of Redundancy: Can't use Computer 1 or IU bus B

Bent pin, broken trace, foreign substance causing the short.

 

Open circuit on any pin

Pin 1, or 2 or 3: Loss of the Computer control logic on Side B

II: Loss of Redundancy: Can't use Bus B

Bent pin, broken trace, foreign substance causing the short.

 

Input or output stuck hi or low

Pin 1: Stuck input will also be stuck on the MUX_A input. Causes loss of Computer 2.

II: Loss of Redundancy: Can't use Computer 2

Bent pin, broken trace, foreign substance causing the short.

 

Input or output stuck hi or low

Pin 2: Stuck input will also be stuck on the MUX_A input. Causes loss of Computer 1.

II: Loss of Redundancy: Can't use Computer 1 or IU bus B

Bent pin, broken trace, foreign substance causing the short.

 

Input or output stuck hi or low

Pin 3: Stuck output, causes loss of Bus B

II: Loss of Redundancy: Can't use Bus B

Bent pin, broken trace, foreign substance causing the short.

 

Simultaneous short on all connections

All the pins on the chip are shorted together

I: Catastrophic, loss of both Computer 1 and Computer2 Control signals

Internal chip failure.

 

Output signal varies by >25%

Pin 3: output varies by >25%, may cause loss of Bus B

II: Loss of Redundancy: Can't use Bus B

Internal chip failure.

 

Parasitic oscillation of outputs

Pin 3: Output oscillates, causes loss of Bus B

II: Loss of Redundancy: Can't use Bus B

Internal chip failure.

 

 

 

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