3 bq20z65 Circuit Module Schematic
3.1 Schematic
3.2 Modifications for Choosing Particular Precharge Mode
3.3 Testing Fuse-Blowing Circuit
4 Circuit Module Physical Layouts and Bill of Materials
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bq20z65 Circuit Module Schematic
This section contains information for modifying and choosing a precharge mode for bq20z65/bq29412
implementation.
The schematic follows the bill of materials in this user's guide.
In order to charge, the charge FET (CHG-FET) must be turned on to create a current path. When the
V
(BAT)
is 0 V and CHG-FET = ON, the V
(PACK)
is as low as the battery voltage. In this case, the supply
voltage for the device is too low to operate. This function has three possible configurations, and the IC can
be easily configured according to the application needs. The three modes are 0-V Charge FET mode,
Common FET mode, and Precharge FET mode.
1. 0-V Charge FET mode - Dedicates a precharge current path using an additional FET (ZVCHG-FET) to
sustain the PACK+ voltage level.
2. Common FET mode - Does not use a dedicated precharge FET. The charge FET (CHG-FET) is set to
ON state as default.
3. Precharge FET mode - Dedicates a precharge current path using an additional open-drain (OD) pin
drive FET (PCHG-FET) to sustain the PACK+ voltage level.
To use a particular mode of charging with the EVM, add or remove some elements shown in Table 2 , and
use the given settings of DF.Configuration, ZVCHG1, 0.
Table 2. Components and Flash-Memory Settings for Different Precharge
Modes
MODE RESISTORS PRECHG FET ZVCHG1 ZVCHG0
1. 0-V Chg (default) R21, R28 Q3 0 0
2. Common FET R24 Q2 0 1
3. Precharge R23, R28 Q3 1 0
For more details about precharge operation and mode choices, see the bq20z65 data sheet (SLUS878 ).
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 TP3 low if a fuse-blow condition occurs; so, monitoring TP3 can be
used to test this condition. Fuse placement on the application board is shown in the bq20z65 data sheet
reference-board schematic.
This section contains the printed-circuit board (PCB) layout, bill of materials, and assembly drawings for
the bq20z65/bq29412 circuit module.
SLUU353 – June 2009 bq20z65EVM-001 SBS 1.1 Impedance Track™ Technology 3
Enabled Battery Management Solution Evaluation Module
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