Revised Worksheet

Revised Worksheet

	*FXO INC.* Re-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.	II: Loss of Redundancy: Can't use IU bus A	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.	II: Loss of Redundancy: Can't use IU bus B	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.
R1 Buffering resistance to protect inputs	Open Ckt	CONTROL1 signal is opened to MUX A input	II: Loss of Redundancy: Can't use IU bus A	Internal failure, Broken lead, Broken solder joint
	Short Ckt	No effect	IV: Minor	part failure
	Change in Resistance	No effect for resistance within 25%	IV: Minor	part failure
R2 Buffering resistance to protect inputs	Open Ckt	CONTROL2 signal is opened to MUX A input	II: Loss of Redundancy: Can't use IU bus A	Internal failure, Broken lead, Broken solder joint
	Short Ckt	No effect	IV: Minor	part failure
	Change in Resistance	No effect for resistance within 25%	IV: Minor	part failure
R3 Buffering resistance to protect inputs	Open Ckt	CONTROL1 signal is opened to MUX B input	II: Loss of Redundancy: Can't use IU bus B	Internal failure, Broken lead, Broken solder joint
	Short Ckt	No effect	IV: Minor	part failure
	Change in Resistance	No effect for resistance within 25%	IV: Minor	part failure
R4 Buffering resistance to protect inputs	Open Ckt	CONTROL2 signal is opened to MUX B input	II: Loss of Redundancy: Can't use IU bus B	Internal failure, Broken lead, Broken solder joint
	Short Ckt	No effect	IV: Minor	part failure
	Change in Resistance	No effect for resistance within 25%	IV: Minor	part failure
MUX_A Computer control signal multiplexing	Short circuit between any two adjacent connections	Pin 1 and Pin 2: The buffered control signals from the redundant computers are shorted.	II: Loss of Redundancy: Output from Bus A is wrong, but Bus B is good	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 buffered Computer 2 is shorted to the MUX_A output. Causes loss of redundancy	II: Loss of Redundancy: Can't use 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 to MUX A input.	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 2: Stuck input on MUX A input.	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 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	II: Loss of Redundancy: Can't use Bus A	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 buffered control signals from the redundant computers are shorted.	II: Loss of Redundancy: Output from Bus B is wrong, but Bus A is good	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 buffered Computer 2 is shorted to the MUX_B output. Causes loss of redundancy	II: Loss of Redundancy: Can't use 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 to MUX B input.	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 2: Stuck input on MUX B input.	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 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	II: Loss of Redundancy: Can't use Bus B	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.