BQ24180_1 Datasheet, PDF (21/41 Pages) Texas Instruments – Fully Integrated Switch-Mode One-Cell Li-Ion Charger with Full USB Compliance and Accessory Power Connection

bq24180
www.ti.com
SLUSA02 A – FEBRUARY 2010 – REVISED FEBRUARY 2010
Hardware Disable Input (CD)
The bq24180 contains a CD input that is used to disable the charger and place the bq24180 into high-impedance
mode. Drive CD low to enable charge and enter normal operation. Drive CD high to disable charge and place the
bq24180 into high-impedance mode. Driving CD high during DEFAULT mode resets the safety timer. Driving CD
high during HOST mode suspends, but does NOT reset the safety timer. CD is internally pulled down to GND
with a 100kΩ resistor.
LDO Output (DRV)
The bq24180 contains a linear regulator (DRV) that is used to supply the internal MOSFET drivers and other
circuitry. Additionally, DRV supplies up to 10mA external loads to power the STAT LED or the USB transceiver
circuitry. The maximum value of the DRV output is 5.5V so it ideal to protect voltage sensitive USB circuits. The
LDO is on whenever a VBUS supply is connected to the bq24180. The DRV is disabled under the following
conditions:
1. Faulty adapter detected or VBUS < UVLO
2. Thermal Shutdown
AC Adapter Mode, Charge Current Limiting
After power is connected and startup is initiated, the PSEL input is read to determine the default startup values. If
PSEL is 0, AC Adapter mode is selected. In AC Adapter mode, the charge current is regulated to maximize the
charging time. The default parameters in AC Adapter mode are I_CHARGE=1A and V_OUTREG=3.6V. These values
may be changed at any time using the I²C interface. Additionally, if input current monitoring is required, this may
be used during AC Adapter mode as well, but is disabled in DEFAULT mode.
PC Mode, Input Current Limiting
After power is connected and startup is initiated, the PSEL input is read to determine the default startup values.
In PC mode, the input current is limited to maximize the charge rate of bq24180 without overloading the USB
port. The input current for bq24180 can be limited to 100mA, 500mA or 800mA and is programmed in the control
register. Once the input current reaches the input current limiting threshold, the charge current is reduced to
prevent the input current from exceeding the programmed threshold. The input current sensing resistor and
control loop are integrated into bq24180. The input current limit is disabled using I²C control; refer to the
definition of control register (01H) for detail. The default parameters in USB mode are I_INLIM=100mA and
V_OUTREG=3.6V. Charge current may be monitored in PC mode as well, but by default it is set to a maximum such
that the input current limit loop is active.
DCOUT Functionality
The bq24180 contains a DCOUT function that is used to connect a load to the battery through a switch. DCOUT
is implemented using back to back MOSFETs (Q4 and Q5 in Figure 1) to connect DCOUT to the battery. This
prevents reverse feeding the battery from DCOUT when DCOUT is disabled. DCOUT is a current limited source
and can provide up to 1A to power additional accessories. The current limit is programmable from 370mA to 1.5A
in 4 steps using the I²C interface. Additionally, the DCOUT output is enabled or disabled using the I²C interface.
If the load on DCOUT reaches the current limit, the FET that connects DCOUT to the battery is turned off after
the deglitch time (t_{dgl_DCOUT}), a single 128µs pulse is sent on the STAT and INT outputs and the FAULT_x bits of
the status register are updated in the I²C. The DCOUT may be enabled after the fault using the I²C interface.
External NTC Monitoring (TS)
The bq24180 provides a TS input for monitoring an external NTC thermistor. A current is sourced to the NTC
from the TS input and the voltage is monitored. There are 3 temperature thresholds that are monitored; the cold
battery threshold (T_NTC < 5°C), the warm battery threshold (45°C < T_NTC < 55°C) and the hot battery threshold
(T_NTC > 55°C). These temperatures correspond to the V_HOT, V_WARM, and V_COLD thresholds when using a 4.7kΩ
NTC thermistor (b=3500). The TS input is monitored at all times, however, it only affects charging during default
mode. During default mode, charging is suspended and timers are suspended when T_NTC < 5°C or T_NTC > 55°C.
When 45°C < T_NTC < 55°C, the charging current is reduced to 400mA (max). In PC mode, the charge current
remains at 100mA in this mode.
Copyright © 2010, Texas Instruments Incorporated
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