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LMZM23601: Drive capability at Start up timing

Part Number: LMZM23601

Hi Team,

Lmzm23601 didn’t seem to start up when pulling greater than 200mA by electoric load(CC mode) in my customer's evaluation using EVM. Could you answer following my customer's questions?

1. Does this device behave as constant current source at start up timing?
2. How much actual load can  LMZM23601 drive at start up timing? Is it possible to drive 1A at the timing also? 

Here are the their evaluation condition.
Vin : 24V
Vout : 3.3
Load: Electronic load (CC mode)


Issue). Device does not start up with electronic load greater than 200 mA

  • Hi Onawa-san,

    The LMZM23601 is able to drive up to the maximum rated current of 1-A. Figure 45 is a scope-shot taken from measuring the EVM during startup condition similar to your evaluation application(24-Vin, 3.3-Vout). This figure shows that during startup the time it takes PGOOD to be high after EN is high is roughly 6ms for full load 1-A operation.

    Can you check if your power supply's input current is limited? 

    Regards,

    Jimmy 

  • Hi jimmy-san,

    Thanks for your prompt response on this. OK, I understood LMZM23601 should start up under 1A actual load.
    The power supply's current limit is set to 1A. So that is not the root cause.

    Can you check if LMZM23601EVM can start up pulling grater than 200mA on CC mode of electric load on your bench also?

    Regards,
    Takashi Onawa
  • Hi Onawa-san,

    Yes I can take some scopeshots later today. Let me get back to you on this.

    Regards,

    Jimmy 

  • Hi Onawa-san,

    Sorry for the late reply. Attached is a  bench scopeshot of the LMZM23601EVM under the following conditions:

    VIN = 24V; VOUT = 3.3V; ILOAD = 300mA (Eload in CC mode) 

    In both startup cases, the 3.3V output voltage is regulated seen by the PWRGD pin HIGH output reading. 

    Regards,

    Jimmy 

  • Hi Jimmy-san,

    Thanks for taking the data on your bench!

    The customer noticed that electric load settings was wrong.
    After fixing that point, they also confirmed that LMZM23601 could start up with greater than 200mA .

    Regards,
    Takashi Onawa