1、Lessons Learned Entry: 1603Lesson Info:a71 Lesson Number: 1603a71 Lesson Date: 2005-06-02a71 Submitting Organization: DFRCa71 Authored by: Jonathan BrownSubject: Digital Logic Device Latch-up Abstract: Component manufacturers advisories, along with low-inductance ground and power planes/paths within
2、 subsystems, must be heeded. Following the recommendations from the X43A Flight 1 MIB, the Pegasus actuator system was redesigned to accommodate the need for greater hinge torque. The analog-based legacy actuator system was redesigned for digital drive of the power output stage to the actuators, an
3、additional actuator was incorporated to provide the necessary torque including margins, and the power supply was increased to provide the required 80+ amps, instead of the previous 40 amp capability. Multiple failures during qualification testing, and the subsequent technical investigations, proved
4、the lack of understanding between the ideal circuit operation and the impact of system implementation. Low-inductance ground and power planes/paths within subsystems are essential for proper operation. Description of Driving Event: Following the recommendations from the X43A Flight 1 MIB, the Pegasu
5、s actuator system was redesigned to accommodate the need for greater hinge torque. The analog-based legacy actuator system was redesigned for digital drive of the power output stage to the actuators, an additional actuator was incorporated to provide the necessary torque including margins, and the p
6、ower supply was increased to provide the required 80+ amps, instead of the previous 40 amp capability. Multiple failures during qualification testing, and the subsequent technical investigations, proved the lack of understanding between the ideal circuit operation and the impact of system implementa
7、tion. Lesson(s) Learned: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-It was found that a combination of noise, back-feeding through the outputs of a logic device, and ground bounce were able to produce sufficient voltage below the components manu
8、facturer specified limit of -0.5 volts that resulted in the FET-based device “latch-up”. The outputs then went into a tri-state condition, allowing the output voltage to gradually rise to the rail voltage. This produced a destructive condition for the H-bridge output transistors. Also, the component
9、 manufacturer determined that once the logic device was exposed to this “latch-up” condition, it became more susceptible to future latch-ups Recommendation(s): It was found that a combination of noise, back-feeding through the outputs of a logic device, and ground bounce were able to produce suffici
10、ent voltage below the components manufacturer specified limit of -0.5 volts that resulted in the FET-based device “latch-up”. The outputs then went into a tri-state condition, allowing the output voltage to gradually rise to the rail voltage. This produced a destructive condition for the H-bridge ou
11、tput transistors. Also, the component manufacturer determined that once the logic device was exposed to this “latch-up” condition, it became more susceptible to future latch-ups Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration S
12、ystemsa71 Sciencea71 Aeronautics ResearchAdditional Key Phrase(s): a71 Accident Investigationa71 Flight Equipmenta71 Hardwarea71 Safety & Mission Assurancea71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2007-07-13a71 Approval Name: ghendersona71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
