Lite SBC: Frequently asked questions - KBA236224
1. How do I handle unused pins in OPTIREG™ Lite SBC?
When functions or pins are not being used, make sure the settings such as "disabled via SPI," are correct. Handle the unused pins as follows:
- WK/VSENSE: Connect to GND and disable WK inputs via SPI
- RSTN / INTN / FO: Pin is open
- VCC2 / VCP: Pin is open and disabled
- VCAN: Connect to VCC1
- CANH/L, RXDCAN, TXDCAN: All the pins are kept open
- TEST: Pin is open or connected to GND for normal user mode operation or connected to VIO to activate SBC Development mode
- n.c.: Not connected; internally not bonded; left floating. Connect to GND to improve thermal behavior
If unused pins are routed to an external connector which leaves the ECU, there must be a provision for the jumper (depopulate if unused).
2. Can I use any MOSFET as switch MOSFET and RVP MOSFET, which is controlled by the VCP pin (charge pump output)?
You can use IPB80N04S4-04 OptiMOS™ -T2 Power-Transistor as given in the datasheet. Ensure that the charge pump load does not exceed the specification while using other MOSFETs. Test the turning (ON and OFF) of the MOSFET in the application to verify that the ON/OFF delays and its thresholds match.
3. Are there any restrictions on the state changes in the SBC development mode?
All the regular SBC mode transitions are possible as the device follows the state diagram in normal operation. The SBC development mode is only used for development purposes and not in the field.
4. Can the SBC wake up via a CAN message if VCAN is not powered?
Yes, the CAN transceiver can wake up even when the VCAN is not powered as the VS supplies the CAN wake receiver directly.
5. How to calculate the time from CAN wakeup to the VCC1 ramp-up?
This is the sum of two time periods for VCC1: wake-up reaction time and charging time.
The wake-up reaction time is 100 μs, as specified in the datasheet. Calculate the VCC1 ramp-up time according to the current limit, capacitor value, and VCC1 voltage.
6. Is it possible for an edge triggered wake-up event to occur when the SBC is in sleep mode resulting in a missed wake-up event?
The wake cell is independent of SBC mode. When the wake cell is enabled, SBC remains active regardless of any SBC mode activity.
7. Is there a minimum load requirement for a stable VCC1 operation?
At very light loads, the DC-DC is switched OFF, and a small LDO keeps running to save the quiescent current. The minimum load requirement for the regulation of LDO is 10 μA.
8. Can VCC1 and VCC2 be shorted to provide higher load currents?
Connecting two devices’ output to achieve higher current capability is expected but not recommended. In fact, due to the devices' tolerance, each converter’s regulated output voltage is different, leading to an unbalanced sharing of load. To resolve this, a current-balancing resistor at the regulator output can be used. There are no reliability issues if load sharing is handled correctly, which means that current is not supplied by a single regulator and there is no reverse flow (from VCC2 to VCC1).
9. Does TLE9471-2ES meet the CIA 601-4 v2.0.0 and v2.1.0 requirements?
TLE9471-2ES does not meet the CIA 601-4 standards. The CIA 601-4 standards refer to signal improvement transceivers (SIC) and the standard is only realized in the standalone transceiver with SIC.
10. How do I restart the CAN communication after powering down?
When the power is restored, the SBC returns to normal mode, and when the VCAN goes above the threshold, the communication is automatically retrieved by the CAN. VCAN undervoltage is detected during low VS, which stops the CAN communications. In addition, the SBC enters a fail-safe state.
11. Does the CAN receiver work when VCAN_UV is present?
In UV CAN mode, the CAN receiver is not affected; since highest voltage between VCAN and the 5 V internal supply is used to power the RX. The transceiver works in receive-only mode even if VCAN is not available because of the independent receiver supply.