JIRA: MH-57 - Getting issue details... STATUS
Before you begin, read Micah's page and the related links on how to use our equipment (see: Test Equipment).
It'd also be helpful to familiarize yourself with the ICs on the board.
CAN Controller (U1): http://ww1.microchip.com/downloads/en/DeviceDoc/MCP2515-Stand-Alone-CAN-Controller-with-SPI-20001801J.pdf
CAN Transceiver (U2): http://www.ti.com/lit/ds/symlink/tcan332.pdf
Precharge Control Load Switch (U3): https://www.onsemi.com/pub/Collateral/NCP45520-D.PDF
Charge Pump Voltage Converter (U4): https://www.onsemi.com/pub/Collateral/NCP45520-D.PDF
Opto-isolator (U5): https://uk.rs-online.com/webdocs/0ad5/0900766b80ad5e24.pdf
CMOS SR Latch (U6): https://www.onsemi.com/pub/Collateral/NCP45520-D.PDF
Micropower Comparator (U7): http://www.ti.com/lit/ds/symlink/tlv1701-q1.pdf
2-Input AND Gate (U8): http://rohmfs.rohm.com/en/products/databook/datasheet/ic/logic_switch/standard_logic/bu4s81g2-e.pdf
Isolated DC/DC Converter (U9): https://uk.rs-online.com/webdocs/0ad5/0900766b80ad5e24.pdf
Initial board validation:
Before we test the precharge function, check to make sure the board is brought up without problems. This includes checking for short circuits and making parts that should or shouldn't be powered are done so. Using the connectivity function on the DMM, check the pins on the 50POS connector to make sure nothing important is bridged (check with the schematic). Do the same with any ICs. As of this point, basically everything should be unpowered. Look over the schematic and make sure any thing powered from VBAT_PRECHARGE_SW is unpowered. It also doesn't hurt to check isolated side.
Test setup:
Set the voltage/current limit on the power supply to 12V/0.1A and connect it to the VBAT connector P1. This is usually supplied by our power distribution board, and controls whether the entirety of the board is powered or not. Capacitors will be ordered to simulate the capacitors in the motor controllers (see: Future Steps/Considerations). Put the capacitors in parallel by soldering wires to their leads to create ~270uF of capacitance. The capacitors are 4 lead and have the following pin-out:
As seen, the closer lead pairs act as one node on either side of the capacitor. The capacitors should be connected to the P4 connector on the isolated side of the board. P4 is an ultrafit connector, harness wires to a matching connector to connect the board to the capacitors.
Enabling precharge:
Normally precharge will be enabled through a firmware signal from the MCU to the enable pin on the load switch U3. If the firmware is unavailable, this can be powered by connecting a 3V3 source to the connector P1 and the enable pin (pin 2). Whenever the enable pin receives power, the isolated side of the board turns on and precharge starts. Before enabling precharge, set up the oscilloscope to read voltage output. There are multiple points of interest to be measured over the duration of precharging and discharging. To precharge and discharge the capacitors, supply and stop supplying the 3V3 to the enable pin on the load switch. With the 3 x 1 kohm resistance for precharge and 1 x 5 kohm resistance for discharge, allow 3s for the capacitor to precharge and 5s for discharge each test.
In place of the 150V supplied by the battery, another 12V source (or any lower voltage source) can be used to connect to the HV line. The precharge functions should be tested with a lower voltage first, remember to recalculate the voltage division values to see when precharge stops.
Before plugging in the capacitors or the HV (12V or similar in this case) to the board, enable precharge via the enable pin and probe the Vin+ pin on the isolated DC/DC and the Vcc pin on the opto-isolater. If the load switch is working correctly, there should be a 12V reading at these points.
Isolated DC/DC:
Still before plugging in the capacitors and HV, enable precharge and probe the test points ISO_1, ISO_2 and DISC_GATE. These should all be reading a 12V signal. If ISO_1 or ISO_2 isn't reading properly, double-check the pins on the isolated DC/DC U9 aren't shorted and connectivity between components is good. If DISC_GATE isn't reading, do the same with charge pump DC/DC U4.
Precharge Test points:
Relevant page on testing MSXII: Precharge Revisions
Connect the HV line (12V or similar) and the capacitors.
The first point to test is the capacitor itself. Enable precharge and measure of the change in voltage over the duration of the capacitor's charge. Note the time taken to fully charge the capacitors. It should follow the expected curve of voltage in an RC circuit. Now unpower the enable pin and measure the discharge. The times taken should be similar:
Precharge Discharge (Note: should be flipped as this is the charge graph)
Next point to test is the voltage on the capacitor side of the precharge circuit and at the IN+ pin of the comparator alongside the comparator output test point. When using 12V in place of the 150V, the voltage at the IN- should be 0.75V. Then the voltage on the capacitor side should be around 11.45V when IN+ exceeds IN-. Check that the capacitor stops precharging when the voltage on the capacitor side indeed reaches around 11.45V and the IN+ pin reaches 0.75V.
Repeat this test, except instead of checking the voltage on the capacitor, measure the test points COMP_OUT, AND_OUT, ISO_LATCH_OUT, LATCH_OUT, and ISO_2. The latter 4 should all be logic low to start and only send a 12V signal when the condition above is met. COMP_OUT will probably output a logic high when both pins are unpowered at the start. Note the times taken for each output to reach logic high. Also check the behaviour of LATCH_OUT to ensure it doesn't oscillate during the transition from logic high to logic low. Examples of transient tests can be seen in the related page posted above (recommended read for understanding of the board regardless).
CAN tests:
Thermistor tests:
Fans: