BQ24075-Q1_15 Datasheet, PDF (17/38 Pages) Texas Instruments – SLUSAU3B –FEBRUARY 2012–REVISED MARCH 2012

bq24075-Q1
www.ti.com
SLUSAU3B – FEBRUARY 2012 – REVISED MARCH 2012
OVERVOLTAGE PROTECTION (OVP)
The bq24075-Q1 accepts inputs up to 28V without damage. Additionally, an overvoltage protection (OVP) circuit
is implemented that shuts off the internal LDO and discontinues charging when V_IN > V_OVP for a period long than
t_DGL(OVP). When in OVP, the system output (OUT) is connected to the battery and PGOOD is high impedance.
Once the OVP condition is removed, a new power on sequence starts (See the POWER ON section). The safety
timers are reset and a new charge cycle will be indicated by the CHG output.
DYNAMIC POWER-PATH MANAGEMENT
The bq24075-Q1 features an OUT output that powers the external load connected to the battery. This output is
active whenever a source is connected to IN or BAT. The following sections discuss the behavior of OUT with a
source connected to IN to charge the battery and a battery source only.
INPUT SOURCE CONNECTED (ADAPTER or USB)
With a source connected, the dynamic power-path management (DPPM) circuitry of the bq24075-Q1 monitors
the input current continuously. The OUT output for the bq24075-Q1 is regulated to a fixed voltage (V_O(REG)). The
current into IN is shared between charging the battery and powering the system load at OUT. The bq24075-Q1
has internal selectable current limits of 100mA (USB100) and 500mA (USB500) for charging from USB ports, as
well as a resistor-programmable input current limit.
The bq24075-Q1 is USB IF compliant for the inrush current testing. The USB spec allows up to 10μF to be hard
started, which establishes 50μC as the maximum inrush charge value when exceeding 100mA. The input current
limit for the bq24075-Q1 prevents the input current from exceeding this limit, even with system capacitances
greater than 10μF. Note that the input capacitance to the device must be selected small enough to prevent a
violation (<10μF), as this current is not limited. Figure 26 demonstrates the startup of the bq24075-Q1 and
compares it to the USB-IF specification.
10 μC
50 μC
100 μs/div
Figure 26. USB-IF Inrush Current Test
The input current limit selection is controlled by the state of the EN1 and EN2 pins as shown in Table 1. When
using the resistor-programmable current limit, the input current limit is set by the value of the resistor connected
from the ILIM pin to VSS, and is given by the equation:
I_IN-MAX = K_ILIM/R_ILIM
(1)
The input current limit is adjustable up to 1.5A. The valid resistor range is 1.1 kΩ to 8 kΩ.
When the IN source is connected, priority is given to the system load. The DPPM and Battery Supplement
modes are used to maintain the system load. These modes are explained in detail in the following sections.
Copyright © 2012, Texas Instruments Incorporated
Product Folder Link(s): bq24075-Q1
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