SFFS927 July   2024 ISO7741TA-Q1 , ISO7741TB-Q1

 

  1.   1
  2.   Trademarks
  3. 1Overview
  4. 2Functional Safety Failure In Time (FIT) Rates
    1. 2.1 16-DW SOIC Package
  5. 3Failure Mode Distribution (FMD)
  6. 4Pin Failure Mode Analysis (Pin FMA)
    1. 4.1 16-DW SOIC Package

4 Pin Failure Mode Analysis (Pin FMA)

This section provides a failure mode analysis (FMA) for the pins of the ISO7741Tx-Q1 (16-DW SOIC). 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

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

  • The external transformer for the push-pull driver is connected with a winding between D1 and VCC1 and the second winding is connected between D2 and VCC1.
  • For short-to-ground analysis, the ground referenced for the short is the ground on that side of the isolation barrier.
  • For short-to-supply analysis, the supply referenced for the short is the supply on that side of the isolation barrier.
  • The default output state for OUTx outputs are high for ISO7741TADWRQ1 and ISO7741TBDWRQ1 and low for ISO7741FTADWRQ1 and ISO7741FTBDWRQ1.
  • The switching frequency for the A, 160kHz, or B, 420kHz, versions of the ISO7741Tx-Q1 device does not impact the pinFMA.
  • The signal drivers to any or all input channels, INx, do not have enough current sourcing capability to provide regular operating current of the device if the input signal current is conducted into the VCCx supply of the device through an ESD diode on the INx pin if the VCCx pin on the input pin side of the device is floating.