BQ24075RGTT 查看數據表（PDF） - Teccor Electronics
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BQ24075RGTT Datasheet PDF : 53 Pages
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bq24072, bq24073, bq24074, bq24075, bq24079
SLUS810L – SEPTEMBER 2008 – REVISED JUNE 2018
Feature Description (continued)
9.3.3 Overvoltage Protection (OVP)
The bq2407x accepts inputs up to 28 V without damage. Additionally, an overvoltage protection (OVP) circuit is
implemented that shuts off the internal LDO and discontinues charging when VIN > VOVP for a period long than
tDGL(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 Power On ). The safety timers are
reset and a new charge cycle will be indicated by the CHG output.
9.3.4 Dynamic Power-Path Management
The bq2407x 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.
9.3.4.1 Input Source Connected (ADAPTER or USB)
With a source connected, the dynamic power-path management (DPPM) circuitry of the bq2407x monitors the
input current continuously. The OUT output for the bq24073/ 74/ 75/ 79 is regulated to a fixed voltage (VO(REG)).
For the bq24072, OUT is regulated to 200 mV above the voltage at BAT. When the BAT voltage falls below 3.2
V, OUT is clamped to 3.4 V. This allows for proper startup of the system load even with a discharged battery.
The current into IN is shared between charging the battery and powering the system load at OUT. The bq2407x
has internal selectable current limits of 100 mA (USB100) and 500 mA (USB500) for charging from USB ports,
as well as a resistor-programmable input current limit.
The bq2407x is USB IF compliant for the inrush current testing. The USB specification allows up to 10 μF to be
hard started, which establishes 50 μC as the maximum inrush charge value when exceeding 100 mA. The input
current limit for the bq2407x prevents the input current from exceeding this limit, even with system capacitances
greater than 10 μF. The input capacitance to the device must be selected small enough to prevent a violation
(<10 μF), as this current is not limited. Figure 17 demonstrates the start-up of the bq2407x and compares it to
the USB-IF specification.
10 μC
50 μC
100 μs/div
Figure 17. USB-IF Inrush Current Test
The input current limit selection is controlled by the state of the EN1 and EN2 pins as shown in the EN1/EN2
Settings table in Pin Configuration and Functions . 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:
IIN-MAX = KILIM/RILIM
(1)
The input current limit is adjustable up to 1.5 A. The valid resistor range is 1.1 kΩ to 8 kΩ.
Copyright © 2008–2018, Texas Instruments Incorporated
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