Texas Instruments bq2425xEVM-150, User Manual

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Introduction
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12 bq2425xEVM-150 Top Layer
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13 bq2425xEVM-150 Second Layer (Internal) Routine
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14 bq2425xEVM-150 Third Layer (Internal) Routine
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15 bq2425xEVM-150 Bottom Layer
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List of Tables
1 Connector and Test Points
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2 Test Points Description
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3 Pin Descriptions
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4 Control and Key Parameters
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5 bq2425xEVM-150 Bill of Materials
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1 Introduction
The bq24250, bq24251, and bq24257 devices are highly-integrated, single-cell, Li-Ion battery chargers
with integrated current sense resistors targeted for space-limited, portable applications with high-capacity
batteries. The single-cell charger has a single input that operates from either a USB port or AC wall
adapter for a versatile solution. BC1.2-compliant D+/D– detection allows for recognition of CDP, DCP,
SDP, and non-standard USB adapters. The use of an accessory dead-battery provision (DBP) pin allows
for the system to sync a dead battery state in order to enable/disable the BC1.2 detection in the case of
an external USB-PHI.
The bq24250, bq24251, and bq24257 devices have two modes of operation: 1) I
2
C™ mode, and 2)
standalone mode. In I
2
C mode, the host adjusts the charge parameters and monitors the status of the
charger operation. In standalone mode, the external resistor sets the input-current limit, and charge-
current limit. Standalone mode also serves as the default settings when a DCP adapter is present. They
enter host mode while the I
2
C registers are accessed and the watchdog timer has not expired (if enabled).
The battery is charged in four phases: trickle charge, pre-charge, constant current and constant voltage. In
all charge phases, an internal control loop monitors the IC junction temperature and reduces the charge
current if the internal temperature threshold is exceeded.
The bq24250 and bq24251 have system power path management. This feature allows this device to
power the system from a high efficiency DC/DC converter while simultaneously and independently
charging the battery. The charger monitors the battery current at all times and reduces the charge current
when the system load requires current above the input current limit. This allows for proper charge
termination and enables the system to run with a defective or absent battery pack. Additionally, this
enables instant system turn-on even with a totally discharged battery or no battery. The power-path
management architecture also permits the battery to supplement the system current requirements when
the adapter cannot deliver the peak system currents. This enables the use of a smaller adapter.
2 bq2425xEVM-150, Single-Cell Li-Ion Switch-Mode Charger SLUUA08A – March 2013 – Revised April 2013
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