I am fairly new to pcb design and I am having trouble understanding why my PCB is not working. I am using a LTC4417 power path converter and a IRF7324 power mosfet to turn on an embedded system with a pair of 14.4V batteries. I have one internal battery and one swappable battery in my system.

LTC4417 datasheet http://cds.linear.com/docs/en/datasheet/4417f.pdf

IRF7324 datasheet https://www.infineon.com/dgdl/irf7324.pdf?fileId=5546d462533600a4015355f5e10a1b47

My system has an ON button (JP5 connection) that when shorted routes >1 V to the LTC4417 ENABLE pin that should then result in V1 (on LTC4417) being routed to Vout (on LTC4417) and the mosfet opening, thus allowing BINT_OUT to flow to V_toboard.

Problems: The gate drivers VS1 and G1 show the same voltage so the mosfet is not opening. I believe G1 should be pulled low causing the mosfet to open.

I have shown three pictures below. The first is the schematic of the power controller section of my board.

The second pictures shows all the voltage readings on each of the LTC4417 pin when the EN pin is low.

The third pictures shows all of the voltage readings on each pin of the LTC4417 when the EN pin is high. In this scenario, V_toboard should be the same as B_int. Note: VALID1 connected to a pullup resistor and the 16.3 V reads a value of 0.4V but should read 0V when the voltage into V1 is valid.

Can you help me solve why the Vtoboard does not match Bint_out

This is the schematic of the power converter section of my board

Voltages on each pin of LTC4417 when EN pin is low

Voltages on each pin of LTC4417 when EN pin is high

  • 2
    \$\begingroup\$ Welcome to EE.SE. Please rotate your bottom diagrams so they are readable. If over sized the software will insert horizontal or vertical elevators bars as required. \$\endgroup\$ – VTNCaGNtdDVNalUy Feb 13 '18 at 1:36
  • \$\begingroup\$ Jordan did you compare your design with the Demo board? What are the differences? power sources and battery differences? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Feb 13 '18 at 1:56
  • \$\begingroup\$ V_valid only requires UV and OV to be both < 1V. and G1 has to go low for the external PFETs to switch V_toboard to B_int_out \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Feb 13 '18 at 2:09
  • \$\begingroup\$ Are you using the SSOP package or the QFN package? \$\endgroup\$ – Dan Laks Feb 13 '18 at 4:41
  • \$\begingroup\$ Also, why are you shorting CAS to ground? \$\endgroup\$ – Dan Laks Feb 13 '18 at 4:45

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