Additional Evaluation Setups
8
SLVUAN2A – May 2016 – Revised July 2016
Copyright © 2016, Texas Instruments Incorporated
bq77905 3-5S Low Power Protector Evaluation Module
CAUTION
The bottom bq77905 module will not receive fault conditions from the top
module unless properly modified and connected. Confirm operation of your
modified evaluation setup.
Once modified, the bottom module will not enable FETs when disconnected from the top module.
3.5
Troubleshooting
If the bq77905 does not appear to be operating, check the VDD voltage at TP1 as this should be the
same as the BATT+ voltage. Check the AVDD voltage at J4 pin 1, this should be approximately 2.5 V.
Check that the shunts are installed at the H and L positions on J3 shorting pins 1 to 2 and pins 3 to 4.
Check that the cell input voltages are within the operating range of the part. If a fault has been induced,
check that the recovery condition has been met. The configuration of the supplied IC requires load
removal for recovery from undervoltage, therefore remove any load from the PACK terminals or supply a
charge voltage to recover from UV after the cell voltages have returned to normal. The
section is a good procedure to check the basic operation of the board. If the board has been
used for stacking evaluation be sure the R6 and R7 resistors have been replaced.
3.6
Changing Configuration or Conditions
If the board is modified to change the IC or other components or is operated at an expanded temperature
range, be sure to check component temperatures and other operating characteristics to be sure the board
does not provide a hazard in evaluation. A sample IC device may allow more current flow with higher
surface temperatures. Alternate FETs may require a change to the gate resistor to provide an appropriate
switching time.
4
bq77905EVM Circuit Module Schematic
This section contains information on other EVM features.
4.1
Alternate FETs
The EVM has TO-220 footprints for use as test points or power FETs as options for evaluation.
4.2
BATT Transient Pattern
D1 is a pattern for a TVS on the battery input terminals, if desired.
4.3
Other Uninstalled Components
The bq77905 EVM contains patterns for cell count configuration and stacking interface. Refer to the
schematic diagram and
for additional information.