SLUAAA3A September   2020  – June 2025 UCC2808A-1Q1 , UCC2808A-2Q1

 

  1.   1
  2. 1Overview
  3. 2Functional Safety Failure In Time (FIT) Rates
  4. 3Failure Mode Distribution (FMD)
  5. 4Pin Failure Mode Analysis (Pin FMA)
  6. 5Revision History

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a failure mode analysis (FMA) for the pins of the UCC2808A-xQ1(SOIC 8). The failure modes covered in this document include the typical pin-by-pin failure scenarios:

  • Pin short-circuited to ground (see Table 4-2)
  • Pin open-circuited (see Table 4-3)
  • Pin short-circuited to an adjacent pin (see Table 4-4)
  • Pin short-circuited to supply (see Table 4-5)

Table 4-2 through Table 4-5 also indicate how these pin conditions can affect the device as per the failure effects classification in Table 4-1.

Table 4-1 TI Classification of Failure Effects
ClassFailure Effects
APotential device damage that affects functionality.
BNo device damage, but loss of functionality.
CNo device damage, but performance degradation.
DNo device damage, no impact to functionality or performance.

Figure 4-1 shows the UCC2808A-xQ1 (SOIC 8) pin diagram. For a detailed description of the device pins please refer to the Pin Configuration and Functions section in the UCC2808A-xQ1 data sheet.

UCC2808A-2Q1 UCC2808A-1Q1 Pin Diagram Figure 4-1 Pin Diagram

Following are the assumptions of use and the device configuration assumed for the pin FMA in this section:

  • The UCC2808A-xQ1 devices are connected according to the Typical Application diagram in the UCC2808A-xQ1 data sheet.
Table 4-2 Pin FMA for Device Pins Short-Circuited to Ground
Pin NamePin No.Description of Potential Failure EffectsFailure Effect Class
COMP1No output.B
FB2OUTA and OUTB operate with maximum duty cycle. The converter output cannot regulate.C
CS3OUTA and OUTB operate with maximum duty cycle. The converter output cannot regulate.C
RC 4 No output. B
GND 5 No impact. D
OUTB 6 OUTB stays low. Device damage is possible. A
OUTA 7 OUTA stays low. Device damage is possible. A
VDD 8 The device is not biased. No output. B
Table 4-3 Pin FMA for Device Pins Open-Circuited
Pin NamePin No.Description of Potential Failure EffectsFailure Effect Class
COMP1COMP pin voltage is unstable. OUTA and OUTB duty cycle is unstable. The converter output voltage oscillates.C
FB2COMP voltage stays high. OUTA and OUTB operate with maximum duty cycle. The converter output voltage cannot regulate.C
CS3COMP voltage stays high. OUTA and OUTB operate with maximum duty cycle. The converter output voltage cannot regulate.C
RC 4 No output. B
GND 5 Converter operation is unpredictable. Device damage is possible. A
OUTB 6 The converter operates as a forward converter. The converter output might not be regulated. C
OUTA 7 The converter operates as a forward converter. The converter output might not be regulated. C
VDD 8 The device is not biased. B
Table 4-4 Pin FMA for Device Pins Short-Circuited to Adjacent Pin
Pin NamePin No.Shorted toDescription of Potential Failure EffectsFailure Effect Class
COMP1FBThe converter output loses regulation.C
FB2CSOUTA and OUTB operate with maximum duty cycle. The converter output loses regulation.C
CS3RCNo output.B
RC 4 N/A N/A N/A
GND 5 OUTB OUTB stays low. Device damage is possible. A
OUTB 6 OUTA OUTA and OUTB stay low. Device damage is possible. A
OUTA 7 VDD OUTA stays high. Device damage is possible A
VDD 8 N/A N/A N/A
Table 4-5 Pin FMA for Device Pins Short-Circuited to Supply
Pin NamePin No.Description of Potential Failure EffectsFailure Effect Class
COMP1OUTA and OUTB operate with maximum duty cycle. Device damage is possible.A
FB2OUTA and OUTB stay low. Device damage is possible.A
CS3OUTA and OUTB stay low. Device damage is possible.A
RC 4 OUTA and OUTB stay low. Device damage is possible. A
GND 5 The device is not biased. OUTA and OUTB stay low. B
OUTB 6 OUTB stays high. Device damage is possible. A
OUTA 7 OUTA stays high. Device damage is possible. A
VDD 8 No effect. D