LTM4675 test GUI for LTpowerPlay

Dear Sir 

I have some questions to ask about the LTM4675 test GUI LTpowerPlay 

Customers are in urgent need of knowing this setting rule, this is a urgent case, Thanks 

The attached file is the GUI LTpowerPlay screen , FYI 

(1) About the setting of IIN_OC_WARN_LIMIT this option

    What is his main function?

(2) Settings for the OUTPUT_Voltage option
     What is his main function?

(3) The customer currently needs a function to output SPEC current of 1A, but the limit current should be set at 1.2A. Is this feasible?

     The current verification test with the customer is to set the output current 1A, and the Current limit is 4.1A. Is this verification correct?
     Or do you have other verification test methods to provide a reference?

  • 0
    •  Analog Employees 
    on Oct 18, 2019 4:27 PM

    Hello Jason,

    Please see comments align with your questions below. LTM4675 is dual 9A and single 18A parts. Please refer the detail definition on these register via datasheets. Just search and you will find that. Please reach local FAE for direct prompt support as well.

    The faults in the screen show the OC and UV faults. Please also review your design and make sure the output sensing are tied to VOUTs. 

    Thank you. 

    (1) About the setting of IIN_OC_WARN_LIMIT this option

        What is his main function? This is to set the input current warning value.

    (2) Settings for the OUTPUT_Voltage option
         What is his main function? This is to set the output voltage

    (3) The customer currently needs a function to output SPEC current of 1A, but the limit current should be set at 1.2A. Is this feasible?

    IOUT_OC_FAULT_LIMIT set the inductor peak current. 

    If the maximum output current is Imax and desired the fault load current as 20% higher (1.2xImax), IOUT_OC_FAULT_LIMIT should be set as 1.2Imax +1/2 of the peak to peak inductor current. There are pull down menu in IOUT_OC_FAULT_LIMIT setting and these values can be selected. 

         The current verification test with the customer is to set the output current 1A, and the Current limit is 4.1A. Is this verification correct?
         Or do you have other verification test methods to provide a reference?

  • Hi sir 

    i still have test issue for GUI 

    1. Connect the LTM4675 dual output (dual 9A) in parallel to single output (single 18A). After testing different output voltages, the GUI display current distribution is uneven. See the figure below.(figure 1)

    2. Under the condition of 12V to 5.5V (18A), Switching Frequency: 1MHz, the temperature read by the GUI is too high, which will cause the voltage output to be abnormal.
         The output voltage is reduced to 5V (18A), as is the case.

    3. If Iout_OC_Fault_limit is set to 20A, but output 14A still triggers OCP?
         The figure below is the default value. Is it relevant?

    4. When the reading temperature is higher than OT_fault_limit_paged, the output voltage will not have any action? Even if the action has the option "Immediate off", as shown below.

    5. If the load is 9A or 18A at a time, the output voltage will not respond; it must be added to the 9A or 18A from the low load. (I will do more verification)

    6. Is it possible to fix a switching frequency to match all voltage outputs (0.5V~5.5V)?

     The customer wants to know if the 525KHZ frequency can be used, and the output voltage is 0.5V~5.5V.

    Also, why is the frequency set to 1MHz when the output voltage is set to 5Vout (reference table provided by spec)

  • 0
    •  Analog Employees 
    on Dec 4, 2019 1:28 AM in reply to jasonjc.chang@arrowasia.com
    1. Please check out schematic if the single output configuration is all right. Also double check if configuration register Vale are the same for the two channel .

     

    Current mode is used and the two would share the current equally.

     

    1. Please uses fans or other heatsink at this condition at full loading condition. Also uses the EXTVCC to provide bias voltage externally and relief the thermal stress on the module. PCB layout with wider ara and higher copper thickness also can help.

     

    1. IOUT_FAULT_LIMIT is set the peak inductor current fault value.

    For 14A load output, the peak current would be much higher. The setting of 15A cannot fulfill.please read the initial answer regarding the fault current setting . Also data sheet has detail information .

     

    1. Here both immediately off and infinite retry are selected. When only OFF is need when OT occurred, immediately off and never retry should be selected for OT fault response.

     

    1. Please check out if there is any fault occurs when directly applied full load. Then relax these limitation to see if direct load wo rks.

     

    1. Peak to speak current information is used in control loop. At different output voltage with same inductance build inside the module, the peak to peak current value would be different.

     

    There is a recommendation frequency for different output voltage . If prefer to use one frequency for a wide output voltage range , you will need to test to see if it works .

     

    Please choose the high current limit and largeat OC Fault LImit from pull down menu, higher peak to peak current at higher Voltage with lower frequency may trigger the OC fault.

  • Hi sir 

    Want to ask some questions for LTM4675 IC parallel MAX 

    1. Customers want to use LTM4675 to design 100A output, they need to know how many ic can be connected in parallel 

    Thanks for you help