Texas Instruments BQ20Z40EVM-001, User Manual, Page: 3 / 19

2.2 Pin Descriptions
3 bq20z40/bq29330 Circuit Module Schematic
3.1 Schematic
3.2 Choosing Particular Precharge Mode
3.3 Testing Fuse-Blowing Circuit
4 Circuit Module Physical Layouts and Bill of Materials
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bq20z40/bq29330 Circuit Module Schematic
PIN NAME DESCRIPTION
1N –ve connection of first (bottom) cell
1P +ve connection of first (bottom) cell
2P +ve connection of second cell
3P +ve connection of third cell
4P +ve connection of fourth (top) cell
SMBC Serial communication port clock
SMBD Serial communication data port
VSS Pack negative terminal
PACK– Pack negative terminal
SYS PRES System present pin (if low, system is present)
PACK+ Pack positive terminal
This section contains information on the schematic for the bq20z40/bq29330/bq29412 implementation.
The schematic follows the bill of materials in this user's guide.
The chipset supports both a charger that has a precharge mode and one that does not. The EVM
supports a charger that does not have a precharge mode by grounding the PMS pin with resistor R16.
R12 and Q2 are used as the precharge current path in order to sustain sufficient Pack+ voltage when the
battery voltage is too low to power up the bq29330 IC.
If the charger has a precharge function, R12 and FET Q2 are not used. The EVM does not have a
provision to pull high the PMS pin to disable ZVCHG output. The charge FET Q1 is used as the precharge
FET, and the charger must control the precharge current and voltage.
Note: The configuration at PMS pin is a hardware level control. Once the bq20z40 is up and running, the
firmware may change the precharge settings. See the bq20z40 data sheet (
SLUS801 ). for further
information.
To prevent the loss of board functionality during the fuse-blowing test, the actual chemical fuse is not
provided in the circuit. FET Q4 drives TP3 low if a fuse-blow condition occurs; so, monitoring TP3 can be
used to test this condition.
This section contains the board layout, bill of materials, and assembly drawings for the bq20z40/ bq29330/
bq29412 circuit module.
Note: For the battery pack designer: D3 may have side effects. See the application report bq29330
External Short-Circuit Protection ( SLUA436 )
SLUU320C – January 2009 – Revised June 2009 bq20z40EVM-001 SBS 1.1 Impedance Track™Technology 3
Enabled Battery Management Solution EVM
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