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LTC3886 Current Accuracy(Isense+/-) specification , PCB recommand guide, Current sense scheme review request.

Using the LTC3886 current sensing data is not matched my ideal result.

Could you please advice Isense schematic review,  PCB recommand guide(pattern thick, length, etc) and Current sense accuracy specification? 

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  • Hello Mike,

    There are two methods to sense the inductor current: Use precision current sense Rsense or Inductor's DCR as the current sense element. If you prefer to get the inductor current to be sensed accurately, it is recommended to use current sense resistor Rsense instead of Inductor's DCR as the current sense element. Please refer to the below images for a simplified drawing of these two current sense methods. For more details, please refer to LTC3886's datasheet, page 42.

    *Layout notes: Use Kelvin sense for (ISENSE+, ISENSE-) traces, C should be placed very close to ISENSE+, ISENSE- pin outs of the IC. For more details, please refer to the demo board layout of DC2155A-B as the reference. Click on the below link to download the schematic and layout files (File name: DC2155A-B_Design Files) for this demo board : http://www.analog.com/en/products/ltc3886.html#product-evaluationkit. Please also read LTC3886's, page #61 for specific guide of PC board layout of this part.

    *Current Sense Accuracy Specification: There are two selectable current limit range : Low Range or High Range. For more accurate current sense, select High Range. If High Range is selected, the variation of current sense voltage is +/-6mV for VI(ILIMIT)=50mV and +/-7mV for VI(ILIMIT)=75mV. Refer to LTC3886's datasheet, page #5, VI(ILIMIT) section for more details.

    *If you need a detail schematic and layout review of your design using LTC3886, please contact our local FAE so we can better assist you.

    Thank you,

    Best Regards,

    Gina.

Reply
  • Hello Mike,

    There are two methods to sense the inductor current: Use precision current sense Rsense or Inductor's DCR as the current sense element. If you prefer to get the inductor current to be sensed accurately, it is recommended to use current sense resistor Rsense instead of Inductor's DCR as the current sense element. Please refer to the below images for a simplified drawing of these two current sense methods. For more details, please refer to LTC3886's datasheet, page 42.

    *Layout notes: Use Kelvin sense for (ISENSE+, ISENSE-) traces, C should be placed very close to ISENSE+, ISENSE- pin outs of the IC. For more details, please refer to the demo board layout of DC2155A-B as the reference. Click on the below link to download the schematic and layout files (File name: DC2155A-B_Design Files) for this demo board : http://www.analog.com/en/products/ltc3886.html#product-evaluationkit. Please also read LTC3886's, page #61 for specific guide of PC board layout of this part.

    *Current Sense Accuracy Specification: There are two selectable current limit range : Low Range or High Range. For more accurate current sense, select High Range. If High Range is selected, the variation of current sense voltage is +/-6mV for VI(ILIMIT)=50mV and +/-7mV for VI(ILIMIT)=75mV. Refer to LTC3886's datasheet, page #5, VI(ILIMIT) section for more details.

    *If you need a detail schematic and layout review of your design using LTC3886, please contact our local FAE so we can better assist you.

    Thank you,

    Best Regards,

    Gina.

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