Power and analog reference#

The SoM has two digital power paths: regulated carrier power through the underside array, and a separate 3.3 V debug input. An onboard mux selects between them. Analog measurements use the separate VAA connection.

Module power paths

Digital paths#

Carrier power enters on +VDC and reaches VIN and ON of U5, a TPS22950 load switch. Its output is the module’s +5V rail. U6, a TPS7A2633 regulator, takes that rail at IN and EN and produces 3.3VIN_LDO.

U4, a TPS2116 power mux, receives 3.3VIN_LDO on input 1 and the J2.1 debug supply, 3.3VIN_DEBUG, on input 2. Its output is +3.3V, which powers MCU VDD and the TCAN844 VIO connection.

Use regulated carrier power at +VDC. U5 switches the supply; it does not reduce its voltage. Raw battery power must not be connected here.

Connection	Net/path	How to use it
J1 D5, D7, E4, E6, F7, G4, G6	`+VDC` to U5	Regulated carrier supply input
J2.1	`3.3VIN_DEBUG` to mux input 2	Digital power input; check the debugger’s power direction
J5.1; J3.11; J6.4	`+5V`	Shared supply rail, also needed by the CAN transceiver
J6.11; J4.2	`+3.3V`	Digital rail shared with onboard loads
J1 F5; J3.4	`VAA`	Separate analog reference input

Reference and sequencing#

VAA reaches VREFHI through R5. ADC results scale with this reference: a change in reference voltage changes the voltage represented by each count. See analog acquisition for conversions and sampling.

Debug-only power is useful for communicating with the MCU. To read analog inputs, also supply VAA; to communicate over CAN, supply the transceiver’s 5 V rail.

When connecting external devices, avoid driving signals above an unpowered receiver’s supply rail. Check how the carrier, debug supply and connected accessories behave when one is powered and another is off, including possible reverse-current paths.

Supply limits#

The connector rails share their capacity with the module’s own circuitry. Available accessory current depends on the input supply, regulator voltage drop and temperature. Include those loads when sizing the carrier supply, and check rail voltage and heating with accessories connected. Component limits alone do not establish the assembled module’s load-current rating.