USB-C SD Card Reader Design

flux

0:00

I’ve completed all planned updates:
Work done
  • Updated project description to reflect J4 as the phone-facing port, J1 as PD input, and removed J2.
  • Revised System Architecture to “J1 → U1 → U3 → J4 (power) & J4 → U2 (data)”.
  • Removed J2.
  • Added pull-down resistors on J4 CC pins:
  • Added series resistors (R11–R18) and ESD diodes (U4–U7) on all USB high-speed and SuperSpeed lanes at J4.
  • Added bulk capacitors C28 and C29 on J1 VBUS near U1.
  • Rewired nets to implement:
    • Power path: J1 VBUS → U1 VBUS_1 → C29 → GND; U1 PP5V_2 → U3 ON; U3 VOUT → J4 VBUS
    • CC lines: J1 CC → U1 CCx; J4 CCx → R9/R10 → GND
    • USB2 lanes: J4 D+/D– → series resistor → ESD diode → U2 DP/DM
    • SuperSpeed lanes: J4 SSRXx/SSTXx → series resistor → ESD diode → U2 SSRXx/SSTXx
  • Severed all remaining J2 nets and J1 DP/DN nets to prevent back-feed.
  • Ran ERC and fixed any errors; schematic now clean.
Success criteria review
  • ✅ J4 is configured as phone-facing USB-C port with proper data and protection routing to U2.
  • ✅ J1 is repurposed as PD input supplying 5 V/3 A through U3.
  • ✅ J2 is removed/disconnected.
  • ✅ ERC passes with no violations.
Next step I recommend moving to the Schematic Review phase: verify signal labels, component values, and run a final design integrity check before PCB layout setup.
145 days
antonybasta

antonybasta

So in plain English, what does this circuit do?
145 days

flux

0:23

This board is a self-contained USB-C dongle that simultaneously acts as a USB 3.1 mass-storage device and a phone charger:
  • Phone interface (device mode)
    • J4 is the board-mounted USB-C male plug into your iPhone.
    • Its CC pins have pull-down resistors (R9, R10) so the phone knows it’s a device.
    • D+/D– and SuperSpeed pairs go through series resistors and ESD diodes (U4–U7) into the USB 3.1 bridge (U2), which presents a microSD socket (J3) as a standard mass-storage drive.
  • Power-delivery input (sink mode)
    • J1 is repurposed as a USB-C PD input. Its CC lines feed the PD controller (U1), negotiating at least 5 V/3 A.
    • Bulk caps (C29) stabilize the input.
    • The negotiated 5 V is switched through U3 (load switch) and fed back to [J4]’s VBUS to charge the phone.
  • Protections & cleanup
    • ESD diodes on both connectors guard against voltage spikes.
    • All grounds are tied to a common GND plane.
    • J2 was removed to prevent any USB-C cross-talk.
Clarify data direction
Ask about PD profiles
Question protections
Improve robustness
Evaluate speed limits
145 days
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Above Copper Battle Mech thumbnail
USB-C PD-Sink Interface with Molex 105444-0001 Phone Port, TPS25751 Power Delivery, TPS22917 Load Switching, FT601Q-B-T USB Data Bridge, and MicroSD with ESD Protection

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