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Internals

Power

  1. STANDBY_3V3 - Always on (manual switch), supplied from MAX1837EUT33 regulartor (VCC 5V -> 3.3V)
    • system MCU
      • VCC
      • USB port
      • I2C pullup
      • Reset pullup
    • RTC
    • FUSB302BMPX (USB-C with power delivery)
    • Qwiic I2C
    • Power rails latch (enables other power domains)
    • SYSCTL UART 1 connector (keyboard)
    • W25Q32JVSS (Flash?)
  2. VCC 5V - Supplied from charcher
    • MAX1837EUT33 (4.5V - 24V -> 3.3V) provides STANDBY_3V3
    • TPS5450DDAR when enabled via power latch provides 5V rail
    • TPS5450DDAR when enabled via power latch provides 3.3V rail
    • LM2830XQMFE/NOPB when enabled via power latch profides 1.1V rail
  3. USB_VBUS - Power form USB-C port 1 (PD port)
    • VCHG Power to charger
  4. +5V - Enabled via latch
    • AP22815A Power distribution switch; when enabled it powers USB_VBUS so any connected USB device for port 1 (PD port)
    • TLV320AIC3100 Audio codec for speaker and headphones
    • USB port 2 VBUS
    • TPD12S521 HDMI port
    • SoM (CPU card)
    • TUSB8041 USB Hub
    • Keyboard USB power
    • (not connected) Internal USB port for flashing SYS MCU (Receptacle) - this is via do not populate (DNP) resistor so it is not connected to +5V
  5. +3V3 - Enabled via latch
    • TXS0108EPW level shifter for modem (+1V8 -> +3V3)
    • MicroSD card slot
    • TPD12S521 HDMI port
    • IMX Reset pullup
    • DAC I2C pullup (audio)
    • IMX Uart pullup
    • NCV1117ST18T3G 3.3V -> 1.8V (1V8 supply)
    • Ethernet LED
    • USB Hub
    • M2 connectors
    • M2 phone modem
    • MIPI-DSI Display connector
  6. +1V1 - Enabled via latch
    • USBH_1V1 USB Hub
  7. +1V8 - Powered from +3V3 rail by TLV1117-18 (or ON SEMI NCV1117ST18T3G)
    • MIPI-DSI Dispaly connector
    • TXS0108EPW level shifter for modem (+1V8 -> +3V3)
    • MicroSD card slot
    • TLV320AIC3100 Audio codec for speaker and headphones

Summary:

  • Main power from batteries/charger or USB-C comes on VCC 5V.
  • Standby 3.3V power is regulated from the VCC 5V and is supplied to many components including charger (not used), system MCU, keyboard MCU (via UART connector), power latch, real time clock, USB-C PD chip.
  • Power latch is used to enable other rails: 5V, 3.3V (both regulate VCC 5V) and 1.1V (from 3.3V).
  • The 5V power is used many chips, USB power, SoM power, internal USB to keyboard.
  • The 3.3V power may chips and is used for SoM UART and I2C audio chip pullups.
  • The 1.1V is used only for USB Hub.
  • There is also 1.8V supply that regulates from 3.3V for display, modem, MicroSD card and audio.

Interfaces

Qwiic

  • Internal connector
  • Powered with 3.3 standby power
  • I2C to the SYS MCU (SDA0/GPIO0, SCL0/GPIO1)

Pinout:

    GND 3.3V (standby) SDA (RP2040 SDA0/GPIO0) SCL (RP2040 SCL0/GPIO1)

    On SDA0/SCL0 we also have two chips on charger board and PD chip FUSB302BMPX.

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