The bq2407x is a family of integrated Li-Ion battery linear chargers with system power path management functionality targeted at space-constrained portable applications. The devices operate from either a USB port or an AC adapter and support charge currents up to 1.5 A. The input voltage range with input overvoltage protection supports unregulated adapters. The USB input current limit accuracy and start up sequence allow the bq2407x to meet USB-IF inrush current specifications. Additionally, the input dynamic power management (VIN-DPM) prevents system crashes because of incorrectly configured USB sources and maximizes the power available from the adapter.
The bq2407x features dynamic power path management (DPPM) that powers the system while simultaneously and independently charging the battery. The DPPM circuit reduces the charge current when the input current limit causes the system output to fall to the DPPM threshold; thus, supplying the system load at all times while monitoring the charge current separately. This feature reduces the number of charge and discharge cycles on the battery, allows for proper charge termination and enables the system to run with a defective or absent battery pack.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
bq24076 | VQFN (16) | 3.00 mm × 3.00 mm |
bq24078 |
Changes from * Revision (October 2017) to A Revision
Additionally, the regulated system input enables instant system turn-on when plugged in even with a totally discharged battery. The power-path management architecture also lets the battery supplement the system current requirements when the adapter cannot deliver the peak system currents, thus enabling the use of a smaller adapter.
The battery is charged in three phases: conditioning, constant current, and constant voltage. In all charge phases, an internal control loop monitors the IC junction temperature and reduces the charge current if the internal temperature threshold is exceeded. The charger power stage and charge current sense functions are fully integrated. The charger function has high accuracy current and voltage regulation loops, charge status display, and charge termination. The input current limit and charge current are programmable using external resistors.
PART NUMBER(1) (2) | VOVP | VBAT(REG) | VOUT(REG) | VDPPM | OPTIONAL FUNCTION |
---|---|---|---|---|---|
bq24072 | 6.6 V | 4.2 V | VBAT + 225 mV | VO(REG) – 100 mV | TD |
bq24073 | 6.6 V | 4.2 V | 4.4 V | VO(REG) – 100 mV | TD |
bq24074 | 10.5 V | 4.2 V | 4.4 V | VO(REG) – 100 mV | ITERM |
bq24075 | 6.6 V | 4.2 V | 5.5 V | 4.3 V | SYSOFF |
bq24076 | 6.6 V | 4.4 V | VBAT + 210mV | VBAT +100 mV | SYSOFF |
bq24078 | 6.6 V | 4.35 V | VBAT + 210mV | VBAT +100 mV | SYSOFF |
bq24079 | 6.6 V | 4.1 V | 5.5 V | 4.3 V | SYSOFF |
PIN | I/O | DESCRIPTION | |
---|---|---|---|
NAME | NO. | ||
BAT | 2, 3 | I/O | Charger Power Stage Output and Battery Voltage Sense Input. Connect BAT to the positive terminal of the battery. Bypass BAT to VSS with a 4.7-μF to 47-μF ceramic capacitor. |
CE | 4 | I | Charge Enable Active-Low Input. Connect CE to a high logic level to suspend charging. When CE is high, OUT is active and battery supplement mode is still available. Connect CE to a low logic level to enable the battery charger. CE is internally pulled down with approximately 285 kΩ. Do not leave CE unconnected to ensure proper operation. |
CHG | 9 | O | Open-Drain Charging Status Indication Output. CHG pulls to VSS when the battery is charging. CHG is high impedance when charging is complete and when charger is disabled. Connect CHG to the desired logic voltage rail using a 1kΩ-100kΩ resistor, or use with an LED for visual indication. |
EN1 | 6 | I | Input Current Limit Configuration Inputs. Use EN1 and EN2 control the maximum input current and enable USB compliance. See Table 2 for the description of the operation states. EN1 and EN2 are internally pulled down with ≉285 kΩ. Do not leave EN1 or EN2 unconnected to ensure proper operation. |
EN2 | 5 | I | |
ILIM | 12 | I | Adjustable Current Limit Programming Input. Connect a 1100-Ω to 8-kΩ resistor from ILIM to VSS to program the maximum input current (EN2=1, EN1=0). The input current includes the system load and the battery charge current. Leaving ILIM unconnected disables all charging. |
IN | 13 | I | Input Power Connection. Connect IN to the external DC supply (AC adapter or USB port). The input operating range is 4.35 V to 6.6 V (bq24076 and bq24078). The input can accept voltages up to 26 V without damage but operation is suspended. Connect bypass capacitor 1 μF to 10 μF to VSS. |
ISET | 16 | I/O | Fast Charge Current Programming Input. Connect a 590-Ω to 8.9-kΩ resistor from ISET to VSS to program the fast charge current level. Charging is disabled if ISET is left unconnected. While charging, the voltage at ISET reflects the actual charging current and can be used to monitor charge current. See Charge Current Translator for more details. |
OUT | 10, 11 | O | System Supply Output. OUT provides a regulated output when the input is below the OVP threshold and above the regulation voltage. When the input is out of the operation range, OUT is connected to VBAT except when SYSOFF is high. Connect OUT to the system load. Bypass OUT to VSS with a 4.7-μF to 47-μF ceramic capacitor. |
PGOOD | 7 | O | Open-drain Power Good Status Indication Output. PGOOD pulls to VSS when a valid input source is detected. PGOOD is high-impedance when the input power is not within specified limits. Connect PGOOD to the desired logic voltage rail using a 1-kΩ to 100-kΩ resistor, or use with an LED for visual indication. |
SYSOFF | 15 | I | System Enable Input. Connect SYSOFF high to turn off the FET connecting the battery to the system output. When an adapter is connected, charging is also disabled. Connect SYSOFF low for normal operation. SYSOFF is internally pulled up to VBAT through a large resistor (approximately 5 MΩ). Do not leave SYSOFF unconnected to ensure proper operation. |
Thermal Pad | – | – | There is an internal electrical connection between the exposed thermal pad and the VSS pin of the device. The thermal pad must be connected to the same potential as the VSS pin on the printed circuit board. Do not use the thermal pad as the primary ground input for the device. VSS pin must be connected to ground at all times. |
TMR | 14 | I | Timer Programming Input. TMR controls the pre-charge and fast-charge safety timers. Connect TMR to VSS to disable all safety timers. Connect a 18-kΩ to 72-kΩ resistor between TMR and VSS to program the timers a desired length. Leave TMR unconnected to set the timers to the default values. |
TS | 1 | I | External NTC Thermistor Input. Connect the TS input to the NTC thermistor in the battery pack. TS monitors a 10-kΩ NTC thermistor. For applications that do not use the TS function, connect a 10-kΩ fixed resistor from TS to VSS to maintain a valid voltage level on TS. |
VSS | 8 | – | Ground. Connect to the thermal pad and to the ground rail of the circuit. |
EN2 | EN1 | MAXIMUM INPUT CURRENT INTO IN PIN |
---|---|---|
0 | 0 | 100 mA. USB100 mode |
0 | 1 | 500 mA. USB500 mode |
1 | 0 | Set by an external resistor from ILIM to VSS |
1 | 1 | Standby (USB suspend mode) |