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bq28400 Circuit Module Schematic
2.2
Pin Descriptions
PIN NAME
DESCRIPTION
1N
–ve connection of first (bottom) cell
1P
+ve connection of first (bottom) cell
2P
+ve connection of second (top) cell
SMBC
Serial communication port clock
SMBD
Serial communication data port
PRES
System present pin (if low, system is present)
PACK–
Pack negative terminal
VSS
Pack negative terminal
PACK+
Pack positive terminal
3
bq28400 Circuit Module Schematic
This section contains information for modifying and choosing a pre-charge mode for bq28400/bq29200
implementation.
3.1
Schematic
The schematic follows the bill of materials in this user's guide (see
NOTE:
The optional Zener diode (D3) and resistor (R21) on the PRES pin, which are only required
if PRES has a chance to short to PACK+.
3.2
Testing Fuse-Blowing Circuit
To prevent the loss of board functionality during the fuse-blowing test, the actual chemical fuse is not
provided in the circuit. FET Q1 drives TP8 low if a fuse-blow condition occurs (a pull-up at TP8 is
required); so, monitoring TP8 can be used to test this condition.
3
SLUU494 – February 2011
bq28400EVM-001 SBS 1.1 Compliant Tablet PC and Netbook 2-Series Cell
Li-Ion Battery Gas Gauge and Protection
© 2011, Texas Instruments Incorporated