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2.2
Pin Descriptions
3
bq20z70/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
bq20z70/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 for modifying and choosing a precharge mode for
bq20z70/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 by
default supports a charger that does not have a precharge mode. This is configured by grounding the
PMS pin with a resistor. 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 PMS pin must be pulled high
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 bq20z70 is up and running, the
firmware may change the precharge settings. Please refer to bq20z70 datasheet 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 bq20z70/ bq29330/
bq29412 circuit module.
Note:
For the battery pack designer: D3 is not recommended, and should be shorted out if the
DSG FET does not have built-in zener diode protection.
4
bq20z70EVM-001 SBS 1.1 Impedance Track™Technology
SLUU242A – May 2006 – Revised June 2006
Enabled Battery Management Solution Evaluation Module
