BQ24707 Datasheet, PDF (10/36 Pages) Texas Instruments – 1-4 Cell Li+ Battery SMBus Charge Controller With Independent Comparator and Advanced Circuit Protection

bq24707
bq24707A
SLUSA78B – JULY 2010 – REVISED MARCH 2011
CH1: PHASE, 20V/div, CH2: LODRV, 10V/div, CH3: battery voltage,
5V/div, CH4: inductor current, 2A/div, 4us/div
Figure 13. Battery to Ground Short Transition
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98
97
4-cell 16.8 V
96
95
3-cell 12.6 V
94
93
2-cell 8.4 V
92
91
90
V_I = 20 V,
f = 750 kHz,
89
L = 4.7 mH
88
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Charge Current
Figure 14. Efficiency vs Output Current
PIN
NO. NAME
1 ACN
2 ACP
3 CMPOUT
4 CMPIN
5 ACOK
6 ACDET
7 IOUT
8 SDA
9 SCL
10 ILIM
11 IFAULT
12 SRN
PIN FUNCTIONS – 20-PIN QFN
DESCRIPTION
Input current sense resistor negative input. Place an optional 0.1µF ceramic capacitor from ACN to GND for
common-mode filtering. Place a 0.1µF ceramic capacitor from ACN to ACP to provide differential mode filtering.
Input current sense resistor positive input. Place a 0.1µF ceramic capacitor from ACP to GND for common-mode
filtering. Place a 0.1µF ceramic capacitor from ACN to ACP to provide differential-mode filtering.
Open-drain output of independent comparator. Place a 10kΩ pull-up resistor from CMPOUT to pull-up supply rail.
Internal reference is 0.6V or 2.4V, selectable by SMBus command ChargeOption(). When CMPIN is above the internal
reference, CMPOUT goes HIGH. Place a resistor between CMPIN and CMPOUT to program hysteresis.
Input of independent comparator. It has one 50kΏ series resistor and one 2000kΏ pull-down resistor. Program CMPIN
voltage by connecting a resistor divider from the IOUT pin to the CMPIN pin to the GND pin for adapter or charge
current comparison or from the SRN pin to the CMPIN pin to the GND pin for battery voltage comparison. The internal
reference is 0.6V or 2.4V, selectable by SMBus command ChargeOption(). When CMPIN is above the internal
reference, CMPOUT goes HIGH. Place a resistor between CMPIN and CMPOUT to program hysteresis.
AC adapter detect open drain output. It is pulled LOW to GND by an internal MOSFET when the voltage on the
ACDET pin is above 2.4V, voltage on the VCC pin is above UVLO and voltage on the VCC pin is 245mV above the
voltage on the SRN pin, indicating a valid adapter is present to start charge. If any one of the above conditions cannot
meet, it is pulled HIGH to the external pull-up supply rail by an external pull-up resistor. Connect a 10kΩ pull-up
resistor from the ACOK pin to the pull-up supply rail.
Adapter detection input. Program the adapter valid input threshold by connecting a resistor divider from the adapter
input to the ACDET pin to the GND pin. When the ACDET pin is above 0.6V and VCC is above UVLO, REGN LDO is
present, ACOK comparator and IOUT are both active.
Buffered adapter or charge current output, selectable with SMBus command ChargeOption(). IOUT voltage is 20 times
the differential voltage across the sense resistor. Place a 100pF or less ceramic decoupling capacitor from the IOUT
pin to GND.
SMBus open-drain data I/O. Connect to the SMBus data line from the host controller or smart battery. Connect a 10kΩ
pull-up resistor according to SMBus specifications.
SMBus open-drain clock input. Connect to the SMBus clock line from the host controller or smart battery. Connect a
10kΩ pull-up resistor according to SMBus specifications.
Charge current limit input. Program ILIM voltage by connecting a resistor divider from the system reference 3.3V rail to
the ILIM pin to the GND pin. The lower of the ILIM voltage or DAC limit voltage sets the charge current regulation limit.
To disable control on ILIM, set ILIM above 1.6V. Once the voltage on the ILIM pin falls below 75mV, charge is
disabled. Charge is enabled when the ILIM pin rises above 105mV.
Open-drain output. It is pulled LOW by an internal MOSFET when ACOC or a short circuit is detected. It is pulled
HIGH to the external pull-up supply rail by an external pull-up resistor in normal condition.
Charge current sense resistor negative input. The SRN pin is for battery voltage sensing as well. Connect SRN pin to
a 7.5 Ω resistor first then from resistor another terminal connect a 0.1µF ceramic capacitor to GND for common-mode
filtering and connect to current sensing resistor. Connect a 0.1µF ceramic capacitor between current sensing resistor
to provide differential mode filtering. See application information about negative output voltage protection for hard
shorts on battery to ground or battery reverse connection by adding small resistor.
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