Datasheet, Design on Altium Drive

To the power board the LiPo Battery is connected. The power board ensures that the battery is not discharged beyond its limits through a bms system. Besides, it provides a place for all other PCBs to interconnect, namely the Top Board, Kicker Chipper Board, Dribbler Board and Ballsensor. For the Kicker Chipper Board and Dribbler Board it also provides 5V and 3.3V. Formerly, some functionality of the power board was done by a PCB called the back board, which is now not in the robot anymore.

The design can be divided in three sections, as done below. This also corresponds to three sheets in the datasheet.

A battery management system (BMS) is any electronic system that manages a rechargeable battery (cell or battery pack), such as by protecting the battery from operating outside its safe operating area and providing charge information to the micro controller. The BMS on the power board utilizes three ICs to archive this. The design is loosely based on the BMS used by Tigers Mannheim.

Warning: note that Q100 is responsible cutting off power to the rest of the robot, thus all 24V will be present on the lines before this mosfet.

The LiPo Battery is connected via a XT60 connector P100 to the power board. Thereafter a non resealable very fast acting 10A fuse F100 prevents the robot from drawing more than 10A from the battery. Note that this is more than the cut-off current set for U100.

U101 LTC2950CTS8-1 s a micropower, wide input voltage range, pushbutton ON/OFF controller. The part contains a pushbutton input with independently programmable ON and OFF debounce times that control the toggling of an open drain enable output. The part also contains a simple micropro cessor interface to allow for proper system housekeeping prior to power down. Under system fault conditions, an internal KILL timer ensures proper power down. Push button S100 provides a signal to U101, which eventually toggles EN pin 6. The 100pF capacitor C103 connected to ONT pin 3 defines that, together with an internal capacitance, the push button needs to be held down for at least 34ms before the EN is turned high. Thereafter the PB input is ignored for 512ms, acting as a debounce protection. Note that if KILL pin 8 is not brought high during this 512ms time window, the enable output is released. However, because of pull-up resistor R112, this is always the case. This resistor can be removed in future implementations, such that this feature can be utilized. For example, power can be disconnected when the microcontroller does not boot, or does not behave as expected. For power down, button S100 can be pressed again for at least 34ms as set by C104. First INT pin 5 will be low, notifying the microcontroller power will be cut within 1024ms. After this time, EN pin 6 will be pulled low. This time can be shortened by pulling KILL pin 8 low by the microcontroller. KILL pin 8 can always be pulled low by the microcontroller, resulting in an instant low in the EN pin 6. Note the difference between LTC2950CTS8-1 and LTC2950CTS8-2, which lies in the EN pin.

U100 LTC4231CMS-2 provides over voltage, under voltage and over current protection. Futuremore it acts as a Hot Swap controller that allows safe circuit board insertion and removal from a live power supply. An internal high side switch driver controls the gate of an external N-channel MOSFET. Back-to-back MOSFETs can be used for reverse supply protection down to –40V. Between U101 and U100, SW100 can be used to overwrite the EN signal from U101 by connecting SHDN pin 3 to ground such that the system is always off. U100 GATE pin 12 drives n-mosfet Q100 connecting the battery to the rest of the system. This is only done when all start-up conditions are satisfied. These conditions are: (1) a high input on SHDN pin 3, (2) the OV and UV protection inputs on pin 2, 4-7 and (3) the the OC protection sensed by SENSE pin 1. For over current (OC) protection, U100 measures the voltage drop over R100. The value of R100 defines the maximum current, R_sense = 47mV / I_max. When this is exceeded for more than 11.3ms, as set by C105 connected to TIMER pin 10, the external mosfet will be cut off. The resistor network R121 - R125 defines the over voltage (OV) and under voltage (UV). When the battery is connected, its voltage needs to be between 22.5V and 30V. Once connected, it should stay above 22.5V. U102 can provide a digital voltage and current measurement interface to the microcontroller. At the time of writing this is not yet implement in the robocode. This very small and unhandy package has been chosen because at the time of development no other IC was available.

The battery voltage is converted to 5V by fixed step down regulator U300. This 5V is also used by LDO IC300 to create 3.3V.

For all interconnections with other PCBs, The WR-MM Mini Module from Würth are used. For UART and I2C breakout, standard 2.54 mm header pins are used.

1. Inspect the board for faulty soldering connections.
2. Check if VCC, 5V and 3.3V are not shorted to GND.
3. Connect a charged battery to the board.
4. Check if there is any voltage after fuse F100.
5. Press button S100.
6. Check if there is an voltage on VCC.
7. Check if there is 5V and 3.3V.

No testing procedure for U102 yet.

-- Testing code

• Board does not start up.
  • Ensure SW100 is set correctly.
  • Check if the battery is charge, so it does not lay outside the OV and UV protection.
  • Check if F100 is not blown using the continuity of resistance setting on a multimeter. If so, the fuse can be taken out of its holder and be replaced.
  • Check the output of EN pin 6 of U101. This can easily be done on the pins of SW100. See also next problem. If this line does not respond to any input from S100, U101 might be broken. Happened one or two times.
  • Follow the power line from the battery to VCC and find out where there is no power anymore. It is fairly unlikely that Q100 is broken.
• Board only turns on for about a second.
  • Check if there LDO IC300 generates 3.3V. If not replace it.
  • Check Kill line connected to the KILL pin 8 on U101 to be high. If not check R112.
• The board turns on only now and then.
  • Check if S100 is still working properly. It has happened that the quality of the switch is bad.
• There is no 3.3V and/or 5V.
  • Without 5V, there is also no 3.3V. Replace U300 or IC300.