Features

Integrated power field effect crystal tube and current sensor, which is used to exchange adaptors up to 1-A charging application

saver with a safe timer Charging adjustment

good state output of charging and power supply

low -power automatic sleep mode

integrated charging current monitor

Fixed 7 -hour fast charging safety timer

applicable to low -voltage differential charger of single battery lithium -ion battery or lithium -ion battery set in limited space for space Design

Small 3 mm × 3 mm Son packaging

Application

PDA, MP3 player

#8226 Digital camera

Internet device

smartphone

Instructions

bq24080

and

] BQ24081 is a highly integrated and flexible lithium ion linear charging equipment, which is mainly used for limited charger applications. They provide integrated power field effect pipes and current sensors, high -precision current and voltage adjustment, charging status, and charging terminal, in a single -chip device. Set the size of the charging current in the external resistance. This device is charged to the battery in three stages: adjustment, constant current and constant voltage. Terminal charging according to the minimum current. The internal charging timer provides spare safety for charging. If the battery voltage is lower than the internal threshold, the device will automatically start charging. After removing the AC adapter, the device will automatically enter the sleep mode.

Figure Figure

Typical features

[ 123]

(6), DEGLITCH TIMER Expires – Charge Done Is Deglitch DeClitch Timer Expires – Jarge DECLITCH TIMER Expires -It has been declared that the charging is completed. Function description This device supports precision lithium ions and lithium -ion battery charging systems suitable for single batteries. Figure 6 shows a typical charge distribution chart, and Figure 7 shows a operation flowchart.

Battery pre -processing

During the charging cycle, if the battery voltage is lower than the V (low V) threshold, the device will apply the battery to the battery to the battery. This feature resurrected deeply discharged cells. The resistance RSET connected between ISET and VSS determines the pre -charging rate. V (prechg) and K (set) parameters are specified in the electrical characteristic table.

At the adjustment phase, the device starts the safety timer T (Prechg). If the V (low voltage) threshold is not reached during the timer time, the device turns off the charger and displays the failure on the STATX pin. For more details, see the timer failure recovery part.

The battery is fast charging constant current

The device provides the current current current adjustment and programmable setting point. The resistance RSET connected between ISET and VSS determines the charging rate. The specification table specifies the V (set) and K (set) parameters.

Charging current monitor

When the charging function is enabled, the internal circuit generates a proportional current to the ISET pin. When the external charging current programming resistor RISET is applied, the current generates an analog voltage, and the external host can monitor the voltage to calculate the current from the output pin.

The fast charging voltage adjustment of the battery

Voltage adjustment feedback through the OUT pin. The input is directly connected to the positive electrode of the battery pack. The device monitors battery pack voltage between OUT and VSS pins. When the battery voltage rises to the VO (REG) threshold, the voltage adjustment phase begins, and the charging current begins to decrease.

As a safe backup, the device can also monitor the charging time in the charging mode. If the charger is not terminated in this period of time T (CHG), the charger is closed, and the STATX pin is set to fault. For more details, see the timer failure and recovery part.

Charging termination detection and charging

The device monitors the charging current during the voltage adjustment phase. Once the termination threshold I (terminal) is detected, the charge is terminated. The specification table specifies V (terminology) and K (set) parameters.

After the charging is terminated, once the voltage on the OUT pin is lower than the V (RCH) threshold, the device will start charging again. This function can always be in a full capacity state.

The device monitors the charging current during the voltage adjustment phase. Once the termination threshold I (TERM) is detected, the charge will be terminated immediately.

The resistance RSET connected between Iset and VSS determines the current level at the terminal threshold.

Sleep mode

If the input power supply (IN) is removed from the circuit, the device enters the low -power dormant mode. This function prevents battery power from exhausted without input power.

Charging status output

The output of the opening of the drainage STAT1 and STAT2 indicates the operation of various chargers, as shown in the table below. These state pins can be used to drive LEDs or communicate with host processors. Note that the level indicates that the leakage transistor is cut off.

pg output (BQ24080)

When there is an effective input voltage, the opening of the leakage power (PG) output is low. This output is closed (high impedance) in the dormant mode. PG pins can be used to drive LEDs or communicate with host processors.

Charging enable (CE) input (BQ24080)

Use CE to enable or disable digital input. The low -level signal on this pin is enabled to charge, and the high level signal is disabled and charged and the device is placed in the low power consumption mode. The high to low conversion on this pin will also reset all timer and timer fault conditions.

The timer enables (TE) input (BQ24081)

TE digital input is used to disable or enable fast charging timers. The low -level signal on this pin enables fast charging timer, and this function is disabled by high level signals.

Temperature assessment (BQ24081)

BQ24081 continuously monitor the battery temperature by measuring the voltage between TS and VSS pins.

The internal current source is a common 10-k negative temperature coefficient thermistor (NTC) offers bias (see functional frame diagram). The device compares the voltage on the TS pin with the internal V (TS1) and V (TS2) threshold to determine whether it is allowed to charge. If the temperature exceeds the threshold of V (TS1) and V (TS2), the device will immediately suspend charging by turning off the power FET and maintaining the timer value (that is, the timer does not reset). When the temperature returns to the normal range, charging is recovered.

The allowable temperature range of the 103AT thermistor is 0 ° C to 45 ° C. However, users can modify these thresholds by adding external resistors (see Figure 8 and Figure 9).

timer failure and recovery

As shown in Figure 7, the device provides a recovery method to handle the timer failure. The following summarizes this method: Condition 1

RCH voltage exceeds the threshold and fails (RCH voltage exceeds the threshold).

Recovery method: The equipment waiting for the output pin voltage is lower than the charging threshold. This may be caused by battery load, self -discharge, or disassembly of battery. OnceThe pins voltage is lower than the charging threshold. The device will clear the failure and start a new charging cycle. POR, TE or CE switches can also clear the fault.

Condition 2

OUT pin voltage lower than the charging threshold (V (RCH)), and the timeout failure occurs.

Recovery method: In this case, device application i (fault) current. This small current is used to detect the disassembly of the battery. As long as the battery voltage is kept below the charging threshold, the current will be connected. If the output pin voltage is higher than the charging threshold, the device disables the recovery method of the I (fault) current and performs conditions 1. Once the output pin voltage is lower than the charging threshold, the BQ24080 will clear the fault and start a new charging cycle. POR, TE or CE switches can also clear the fault.

Application information

BQ24080/1 Charger design example

Requirement

power supply voltage u003d 5 v

#8226; Quick charging current about 750 mAh

Battery temperature detection (BQ24081): The default settings u003d –2 ° C to 44.5 ° C

[

123] The charging current of programming 750 mA:

Venture u003d [V (set) × k (set)/i (out)]

According to the electrical characteristic table, V (group) u003d 2.5 V.

According to the electrical characteristic table, k (set) u003d 322.

Improve pipe u003d [2.5 v × 322/0.75 a] u003d 1.073 k .

Select the closest standard value, and use 1.07-k resistors connected between ISET (needle foot 6) and ground.

Battery temperature detection (BQ24081):

Use Semi TEC 103AT-4 NTC thermistor connected between TS (needle pin 9) and ground.

R cold end u003d [v (ts1)/i (ts)] u003d 2.5V/100 μA u003d 25K rtherm hot u003d [v (ts2)/i (ts)] u003d 0.5V/100μAAAAA u003d 5K

Find the corresponding temperature value of the selected thermistor in the manufacturer's resistor temperature table. For 103AT-4 Semi-Taiki thermistor:

5 k u003d 44.5 ° C

25 k u003d 2 ° C

STAT quotes Foot (all device) and PG pin (BQ24080):

The status pin monitoring of the processor:

Select a pull -up resistor, which can provide input bias (leakage current) of input bias (leakage current) greater than the processor and state pins, and still provide a logical high level. RPULLUP ≤ [V (CC Pullup) — V (Logic Hi Min)/(I (μP-Monitor)+I (Stat OpenDrain)] u003d (3.3 v – 1.9 v)/(1 μA+1 μA) ≤700 k #8486 ; Connect a 100-k between each state pin and the VCC of the processor and the VCC of the processor. Connect each state pin to the μP monitor pin.

LED display status:

Select a LED with a rated current of less than 10 mia, and select a resistor to connect with LEDs to limit the current to the required current value (brightness). RLED u003d [(v (input) -v (LED lit))/i (LED)] u003d (5 volts -2 volts)/1.5 mAh u003d 2,000 Euros. A LED and resistor is connected in series between the input and each state pins.

Select input and output capacitors

In most applications, only the required is the high -frequency decoupling capacitor on the feet of the input power. A 0.1 μF ceramic capacitor is placed near IN-PIN and GND-PAD, which is very effective. In some applications, the heat insertion input voltage may need to be prevented. There are three methods:

1. The best way is to add a 6.2V input Zina between IN-PIN and VSS.

2. A low -power Ziner is enough to deal with the transient of the single event. Increased input capacitance will reduce the characteristics of the characteristic, so that the input resistance can effectively suppress the overwhelming, but it may damage the input contact due to high surge.

3. A resistor can be connected in series at the input terminal, but it will cause excessive power consumption.

This device only needs a small capacitor to stabilize the circuit. 0.1-μF ceramic capacitors placed between OUT and GND pads are usually enough.

Thermal factors

BQ24080 and BQ24081 packaging in thermal reinforcement MLP packaging. The package includes a hot pad to provide effective thermal contact between the device and the printing circuit board (PCB). The complete PCB design guide of this packaging is shown in the application report of QFN/SON PCB attachment (TI Literature Number SLUA271).

The most common packaging thermal performance measurement method is from the device connection to the thermal impedance of air (RθJa) around the packaging surface (environment). The mathematical expression of Rθja is:

where:

tj u003d the deviceJie temperature

ta u003d ambient temperature

equipment power consumption

The factors that affect the measurement and calculation of Rθja 123] Equipment direction (horizontal or vertical)

The environmental air volume and air flow around the measured equipment

use multiple 10–13 mil Tonghong #8482; ground copper wires in the power board.

Avoid cutting ground layers with signal trajectories near the power IC.

PCB's size must be sufficiently dissipated.

FR4 (FRP) thickness should be minimized.

The power consumption P of the device is a function of the internal power field effect of the transistor's charge and voltage drop. According to the following formula:

Due to the charging mode of the lithium XX battery, the maximum power consumption usually appears at the beginning of the charging cycle, when the battery voltage is at the lowest. See Figure 6.

PCB layout precautions

Pay special attention to the PCB layout. Here are some guidance principles:

In order to obtain the best performance, from VCC to V (in) decoupled capacitors and output filter capacitors from OUT to VSS Both the VSS pin should be tracked in a short distance. The VSS tube foot should have a short tracking operation to the GND tube foot.

All low -current VSS connections should be separated from the high current charging or discharge circuit of the battery. Use single -point grounding technology, including small signal grounding paths and power grounding paths.

The size of the high -current charging path of the input and output pins must be suitable for the maximum charging current to avoid voltage drops in these circuits.

The device is encapsulated in thermal enhancement MLP package. The package includes a hot pad to provide effective thermal contact between the device and the printing circuit board (PCB). The complete PCB design guide of this packaging is shown in the application report of QFN/SON PCB attachment (TI Literature Number SLUA271).