BQ24171_15 Datasheet, PDF (24/39 Pages) Texas Instruments – bq24171 JEITA-Compliant Stand-Alone, Switched-Mode Li-Ion and Li-Polymer Battery Charger With Integrated MOSFETs and Power Path Selector

bq24171
SLUSAF2C – FEBRUARY 2011 – REVISED APRIL 2015
Feature Description (continued)
Table 2 summarizes typical LC components for various charge currents.
Table 2. Typical Values as a Function of Charge Current
CHARGE CURRENT
Output inductor L
Output capacitor C
1A
6.8 µH
10 µF
2A
3.3 µH
20 µF
3A
3.3 µH
20 µF
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4A
2.2 µH
30 µF
9.3.23 Charge Status Outputs
The open-drain STAT outputs indicate various charger operations as listed in Table 3. These status pins can be
used to drive LEDs or communicate with the host processor. OFF indicates that the open-drain transistor is
turned off.
Table 3. STAT Pin Definition
CHARGE STATE
Charge in progress (including recharging)
Charge complete, Sleep mode, Charge disabled
Charge suspend, Input overvoltage, Battery overvoltage, timer fault, , battery absent
STAT
ON
OFF
BLINK
9.4 Device Functional Modes
The bq24171 is a JEITA-compliant stand-alone switched-mode charger with power path selector. The device can
operate from either a qualified adapter or supply system power from the battery. Dynamic Power Management
(DPM) mode allows for a smaller adapter to be used effectively in systems with more dynamic system loads.
The bq24171 device provides power path selector gate driver ACDRV/CMSRC on input NMOS pair ACFET (Q1)
and RBFET (Q2), and BATDRV on a battery PMOS device (Q3). When the qualified adapter is present, the
system is directly connected to the adapter. Otherwise, the system is connected to the battery. In addition, the
power path prevents battery from boosting back to the input.
The bq24171 features DPM to reduce the charge current when the input power limit is reached to avoid
overloading the adapter. A highly accurate current-sense amplifier enables precise measurement of input current
from adapter to monitor overall system power.
The total input current from an AC adapter or other DC sources is a function of the system supply current and
the battery charging current. System current normally fluctuated as portions of the systems are powered up or
down. Without DPM, the source must be able to supply the maximum system current and the maximum available
charger input current simultaneously. By using DPM, the input current regulator reduces the charging current
when the summation of system power and charge power exceeds the maximum input power. Therefore, the
current capability of the AC adapter can be lowered, thus reducing system cost.
Although the bq24171 is a stand-alone charger, external control circuitry can effectively be used to change pin
settings such as ISET, ACSET, and enable Battery Learn mode to accommodated for dynamic charging
conditions.
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