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LM5143-Q1: Questions about SYNCOUT and Standby-mode

RYO
Intellectual 2000 points
Part Number: LM5143-Q1


Hi all,

I got four questions about this IC. Can you answer to those questions?

  1. In master IC, is spread spectrum enabled on the signal from SYNCOUT?
  2. In the datasheet, there is a statement "When the LM5143-Q1 controller detects 16 missed switching cycles, it enters standby mode and switches to a low IQ state to reduce the current drawn from the input" in datasheet 8.4.1. Can you tell me what "16 missed switching cycles" are? Is it the time < minimum on time?
  3. Regarding to 2, can you tell me what is the condition to exit standby mode?
  4. There are two types of standby mode, standard and ultra-low Iq. Does the device first enter standard standby mode and then ultra-low Iq mode? Or does it directly enters ultra-low Iq mode when MODE=AGND, so that standard standby mode is not used when MODE=AGND?

Thanks,
RYO

  • 0
    TI__Guru* 75612 points

    Hi RYO,

    #1: Yes.

    #2: 16 missing cycles refers to no HO output (for example, when VOUT is high [VFB > VREF] and no switching is required).

    #3: VFB < 99% VREF and VCOMP > 300mV results in exit of standby mode.

    #4: Ultra-low Iq mode is only possible when MODE = 10k to AGND (the "standard" mode is then not applicable). More specifically, note that the standard and ultra-low Iq modes are configured differently. For ultra-low Iq, connect a 10kΩ from MODE to AGND. This reduces the error amp transconductance to 60 µS and the Iq to 15 µA typical. To configure the LM5143-Q1 for standard Iq, connect MODE to AGND - this sets transconductance gain to 1200 µS and under these conditions the Iq will be 25 µA.

    Regards,

    Tim