The BQ24703PW /bq24702 is a highly integrated battery integrated selector supporting battery charge controller and selector tuning and smart battery learning loop and sub-laptop applications tailored for notebook PCs.

Zero Voltage Operation of the bq24702/bq24703 Using Dynamic Power Supplies

A selector feedback circuit ensures management (DPM) to minimize battery charging time Break-Before-Make by maximizing available wall adapter power. Transition This is achieved by dynamically adjusting the battery

±0.4% charging voltage accuracy, suitable for charging Li-ion batteries based on the charging current of the entire system (adapter) currently.

±4% charge current accuracy

The bq24702/bq24703 use fixed frequency pulses

300 kHz integrated PWM controller for width modulator (PWM) to precisely control battery efficient buck regulation charge current and voltage charge current limit can be.

Depleted battery detection and battery protection from overdischarge ±0.6% via a precision 5 V external resistive divider via keypad controller DAC or programmed indication, external bypass voltage reference

20-µA sleep mode current for low battery charge (VREF), drained by bq24702/bq24703.

24-pin TSSOP and 5 mm × 5 mm QFN packages (bq24703 only)

Battery voltage limits can be programmed using an internal 1.196-V, ±0.5% accuracy reference for the critical charging needs of Li-Ion batteries. In addition, the bq24702/bq24703 provide an option to override the accuracy reference and drive the error amplifier directly from an external reference or from a resistor divider to turn off the 5 V provided by the IC. The selector function allows manual selection of system power, battery or wall adapter power.

The bq24702/bq24703 support cell conditioning and cell learning cycles through the ACSEL function. The ACSEL feature allows manual selection of battery or wall power as the main system power source. It also provides automatic switching to remaining power (battery or AC) should the selected system power supply terminate (see the table of available options for differences between the bq24702 and bq24703). The bq24702/bq24703 also provide an alarm function to indicate battery exhaustion.

The bq24702/bq24703 PWM controllers are ideal for operation in buck converters, when applied

The wall adapter voltage is greater than the battery voltage.

Maximum Power Dissipation vs Free Air Temperature

Maximum Power Dissipation (Low K Board) VS Free Air Temperature

The JEDEC low-K (1s) board design used to derive these figures is a 3" x 3", two-layer board, 2 oz.

Copper traces on top of the board.

The JEDEC high-K (1s) board design used to derive this data is a 3" x 3" multilayer board, 1 oz.

Internal power and ground planes and 2oz copper traces on the top and bottom of the board.

Available options

Condition selector operation 20°C≤TJ≤125°C bq24702PW bq24703RHD

battery as power source

Battery Removal Auto-Select AC+Alarm Auto-Select AC+Alarm Reinsert battery Select Adapter Lock according to selector input until adapter is removed or AC select toggles.

AC AS POWER SOURCE

AC removal auto select battery auto select battery.

AC reinsertion based on selector input selection based on selector input selection of depleted battery condition The battery is sent as power. ALARM signal Automatically select ac to send ALARM signal.

AC as power supply Send ALARM signal Send ALARM signal

The alarm signal is valid, the battery is low and the battery is exhausted. When the selector input is not equal to the selector, a single pulse alarm is output.

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are the functional operating conditions of the device at these or any other conditions where the pressure rating is only outside the design operation is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

(2) All voltages are relative to ground. Current is positive and negative in the designated terminals. Consult the package data sheet section for thermal limitations and packaging considerations.

ACDET: AC or adapter power detection. This input pin is used to determine the presence of an AC adapter.

When the voltage level on the ACDET pin is less than VACPRES, the bq24702/bq24703 is in sleep mode,

PWM control is disabled, BATDRV is driven low and ACDRV is driven high. This feature can be used to automatically select the battery as the system power source.

ACDRV: AC or adapter power select output. This pin is used to drive an external P-channel MOSFET to switch to an AC wall adapter as a system power supply. When the ACSEL pin is high, the voltage on the ACDET pin is greater than VACPRES, and the output ACDRV pin is driven low (VHSP). This pin is driven high (VCC) when ACDET is less than VACPRES.

ACN, ACP: Negative and Positive Differential Inputs for AC-DC Adapter Current Sense Resistors, respectively.

ACPRES: This open-drain output pin is used to indicate the presence of AC power. A logic high level indicates the presence of a valid AC input. Low indicates loss of AC power. When the voltage level on the ACDET pin is high, ACPRES is higher than VACPRES.

ACSEL: AC adapter power selection. This input selects AC adapter or battery as power source. A logic high selects AC power and a logic low selects battery.

ACSET: Adapter current programming voltage. This input sets the system current level at which dynamic power management occurs. Adapter current above this programmed level activates dynamic power management and proportionally reduces the available power from the battery.

Low battery alarm output. This open-drain pin indicates the presence of a depleted battery condition. A pull-up resistor on ALARM goes high when the voltage on the BATDEP pin falls below VACPRES. On the bq24702, the ALARM output also activates when the selector input does not match the selector state.

BATDEP: The battery is low. A voltage divider network from the battery to the BATDEP pin is used to set the voltage level of the battery indicated by the ALARM pin as depleted. See the ALARM pin for details. A battery drain is detected when BATDEP is less than VACPRES. Battery voltage < 80% of depletion threshold when no battery condition is detected. In the battery-free state, the bq24702 automatically selects ac as the input source. If ENABLE = 1, the PWM remains enabled.

BATDRV: Battery Power Select Output. This pin drives an external P-channel MOSFET for switching the battery as the power supply for the system. When the voltage level on the ACDET pin is less than VACPRES, the output BATDRV pin is driven low, GND. This pin is driven high (VCC) when ACSEL is high and ACDET > VACPRES.

BATP: Battery charge regulation voltage measurement input to battery voltage gm amplifier. The voltage to turn on this pin usually comes from a voltage divider network connected across the battery. In the voltage loop, BATP is regulated to the battery voltage gm amplifier's VFB accuracy reference.

BATSET: External override for internal precision reference. When BATSET > 0.25 V, the voltage level turns on the BATSET pin to set the voltage charge level. When BATSET≤0.25V, connect the internal VFB reference to the inverting input of the battery error amplifier. To ensure proper battery voltage regulation using BATSET,

BATSET must be > 1.0 V. Simply ground BATSET to use the internal reference.

COMP: Inverting input of the PWM comparator and output of the gm amplifier. Type II compensation recommends a network between COMP and GND.

ENABLE: Charging enabled. A high level on this input pin allows PWM control operation for charging while a low level on this pin disables and forces the PWM output to a high state. Battery charging is initiated by asserting a logic 1 on the ENABLE pin.

GND: Power return and ground reference

IBAT: Battery current difference amplifier output. The output of this pin produces a voltage proportional to the voltage battery charging current. This voltage is suitable for driving the ADC input.

PWM: The gate drive output pin drives the P-channel MOSFET for PWM control. PWM control is active when ACPRES, ACSEL and ENABLE are high. The PWM is driven low to VHSP and high to VCC. SRN, SRP: Differential amplifier inputs for battery current sensing. These pins feed back the battery charge current for PWM control. The SRN is connected to the battery terminal. SRP is the source pin for zero volt operation.

SRSET: Battery charge current programming voltage. The level on this pin sets the battery charge current limit.

VCC: working power supply voltage.

VHSP: The VHSP pin is connected to a 1µF capacitor (close to the pin) to provide a regulated voltage source to drive the gate of the external MOSFET. VHSP = VCC - 10 V, VCC > 10.5 V, VHSP = VCC - 0.5 V. VCC < 10.5 V. A 13V Zener diode should be placed between VCC and VHSP to prevent overloading the MOSFET during startup.

VREF: Bypass precision voltage 5V output. It can be used to set a fixed level on any of the inverting inputs, one of three error amplifiers if desired. Tight tolerances are suitable for charging lithium-ion batteries.

VS: System (load) voltage input pin. The voltage on this pin represents the system voltage to ensure that a switch from AC to battery power is interrupted before the transition. The battery is protected. The P-channel MOSFET connected to the BATDRV pin is disabled if the voltage at VS is greater than BATP for an overvoltage condition. This feature can be eliminated by grounding the VS pin.

Dynamic Power Management

The bq24702/bq24703 fixed frequency PWM controllers are designed to provide closed-loop control of the battery charge current (ICH) based on three parameters, battery float voltage (VBAT), battery charge current and adapter charge current (IADPT). The bq24702/bq24703 are primarily used to control buck converter side P-channel MOSFET devices that use high levels.

These three control parameters can be voltage-programmed through the bq24702/bq24703's resistive divider precision 5 V reference, an external or internal precision reference, or a keyboard controller directly through the DAC interface. Adapter and battery charging current information is sensed and fed back to two transconductance (gm) amplifiers in series with the adapter and battery, respectively, through low-value sense resistors. The battery voltage information is sensed through an external resistor divider and fed back from the battery to the third gm amplifier. The precharge operation must be performed using a PWM regulator. The host can set the precharge current and externally monitor the ALARM pin, detect a depleted battery condition and program the SRSET voltage to obtain the desired precharge current level.

The overall accuracy of the battery charge regulation voltage is a function of the bypassed 5V reference voltage and the tolerances of R1 and R2. The precision voltage reference has a 0.5% tolerance and is suitable for the stringent battery voltage requirements of Li-ion batteries. Tolerance resistors of 0.1% are recommended for R1 and R2 and any resistors used to set BATSET.

The bq24702/bq24703 provides the ability to use an internal precision voltage reference by using a multiplexing scheme, see on the BATSET pin. When the BATSET voltage is below 0.25 V, a turns on the internal reference voltage and the BATSET pin switches from the gm amplifier input.

The BATSET voltage is greater than 0.25 V, the BATSET pin voltage is connected to the input of the gm amplifier and the output voltage is referenced.

If BATSET is used to set the voltage, the recommended minimum BATSET is 1.0 V.

The battery charging current is programmed by the voltage on the SRSET pin. This voltage can come from a 5VVREF resistor divider or DAC. A voltage-to-current source is used to create a voltage drop across an internal offset resistor at one input of the SR gmamplifier. Charge current is then a function of the battery charging current input threshold.