BQ24350 Datasheet, PDF (7/17 Pages) Texas Instruments – Over-Voltage and Over-Current Charger Front-end Protection IC With Integrated Charging FET

bq24350
bq24352
www.ti.com ............................................................................................................................................................... SLUS943A – MAY 2009 – REVISED JUNE 2009
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
BATTERY OVP
VBAT 2 V/div
VACIN = 5 V, VBAT = 3.4 V to 5 V
CHGIN 2 V/div
10000
1000
100
Rdson vs Vgs
VCHGIN = 5 V,
V_CHGIN -V_OUT = 200 mV
IACIN 0.5 A/div
10
Q2
1
Time: 2 mS/div
Figure 10.
600
550
500
450
400
350
300
250
200
150
100
-50
0.1
0
1000
FET ON RESISTANCE vs TEMPERATURE
2000
3000
Vgs - Vchgin-Vgatdrv - mV
Figure 11.
4000
Q1 +Q2
Q1
Q2
0
50
100
150
T_J - Junction Temperature - °C
Figure 12.
5000
BACKGROUND
During the charging process for portable devices, input voltage spikes usually happen when the AC/DC adaptor
is plugged in, or charge current is cut off quickly under fault conditions, such as input OVP, OCP or battery OVP
and so on. The over voltage stress may damage the analog baseband chip which has lower voltage rating due to
its increased complexity. Therefore, over voltage protection is needed for the safe operation of portable devices.
Another challenge arises from the charge circuit that uses external charging FET in series with a reverse
blocking diode as the charging device. The battery may not be fully charged when input voltage is low due to the
additional diode voltage drop. bq24350/2 will provide the solution for above problems since it has input OVP,
OCP, battery OVP function, together with integrated charging FET which will eliminate the reverse blocking diode
in the previously mentioned charge circuit, as shown in Figure 1.
DETAILED FUNCTIONAL DESCRIPTION
The bq24350/2 is a highly integrated circuit designed to provide protection to Li-ion batteries from failures of the
charging circuit. The IC continuously monitors the input voltage and the battery voltage. In case of an input
over-voltage condition, the IC will turn off the internal power FET after a blanking time. If the battery voltage rises
to unsafe levels during charging process, power is removed from the system. If the input current exceeds the
over current threshold for a limited time, the IC will turn off the output power. The integrated charging FET can
regulate the charge voltage and current according to the control from the host. The device can also provide a
voltage source with over voltage and over current protection for host controller.
Copyright © 2009, Texas Instruments Incorporated
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