Post Go back to editing

LTC6993-1 internal short from Output pin to Div pin

Category: Hardware
Product Number: LTC6993-1

I am currently working on a failure modes effects and criticality analysis and was wondering if you can give me some insight into what would happen if there is an internal short between the output pin and the div pin of a LTC6993-1. Thanks in advance

  • An internal or external short of the output pin to the DIV pin is interesting. First, if the DIV pin is off chip configured to DIVCODE =0 or 15, the output would then be shorted to GND or V+ which would result in nothing happening at the output due to the short. If configured to any other DIVCODE it gets a bit interesting. At power up the signal on the TRIG pin is ignored for some time and the output is held low. (Fig 6, page 15 of data sheet). This would put the part in DIVCODE=0 mode (with NDIV=1 and POL=0) as the output driver will override the large valued resistors R1 and R2 off chip. The output will stay low until triggered by a rising edge on the TRIG input. With Ndiv=1, the maximum output pulse is 16us as set by the resistor on the SET pin. Note that this time is one internal Master Oscillator clock cycle. Being only one master clock cycle wide, this pulse will be ignored by the DIV pin's ADC as there is a time hysteresis on the ADC. See the description on "Changing DIVCODE After Start-up" section on page 15. So, in this case the part will act like a "normal" LTC6993-1 part with the DIVCODE set to 0 and will not recover or change from that state. Note that for this to happen would be extremely unlikely, on-chip due to the test coverage and off-chip due to the pin locations of DIV and OUT.