Features

Suitable for car applications

is an ideal selection of single batteries, dual batteries or three batteries lithium ions and lithium-polymers for high-efficiency charger design The battery pack

It is also applicable to the LIFEPO4 battery (see using the BQ24105 to charge the LIFEPO4 battery)

Integrated synchronous fixed frequency pulse controller to work at 1.1 MM The empty ratio is 0%to 100%

the integrated power field effect of the charging ratio up to 2 ampel

high -precision voltage current regulation

Independent (built -in charging management and control) version

LED or host processor status output interface indicator is being charged, the charging, failure and AC adapter existing conditions

] 20-V maximum rated voltage input and output needle

High-voltage side battery current fluidity

battery temperature monitoring

#8226; Low -power automatic dormant mode

reverse leakage protection to prevent battery discharge

heat shutdown and protection

#8226 Built -in battery detection

Provide 20 stitches, 3.5 mm × 4.5 mm, QFN packaging

Instructions

BQ switch #8482; This series is height Integrated lithium ion and lithium polymer switch mode charge management equipment, for extensive portable applications. BQ switch #8482; This series provides integrated synchronous PWM controller and power field effects transistor, high -precision current and voltage adjustment, charging pre -processing, charging status, and charging terminal. In a small, heat enhancement QFN packaging.

The BQ switch charges the battery in three stages: adjustment, constant current and constant voltage. Termination of charging according to the minimum current level that users can choose. Programmable charging timer provides a safe backup for charging. If the battery voltage is lower than the internal threshold, the BQ switch will automatically restart the charging cycle. When the VCC power supply is disconnected, the BQ switch is automatically entered the dormant mode.

Typical application circuit

Typical operating performance

]

Function box diagram

Operation flowchart

] Detailed instructions

BQ switch #8482; supporting precision lithium ions or lithium polymer charging systems for single batteries, dual batteries or three batteries. The typical charge distribution is shown in Figure 4.

PWM controller

Provides 241MHz integrated charging voltage adjustment function. This type of controller is used to help improve the transient response of the line, thereby simplify compensation network for continuous and discontinuous circuit operations. The voltage and current circuit adopt III -type compensation scheme for internal compensation. This scheme provides sufficient phase voltage for stable operation and allows small ceramic capacitors with very low ESR. The bottom of the PWM slope has a 0.5 ambient, which allows the device to work between 0%and 100%duty cycle.

Internal PWM door drives can directly control PMOS and NMOS power MOSFET. The high -voltage side grille voltage from VCC (when it is off) to VCC – 6 (when the connection and VCC greater than 6 V), by increasing the grid voltage to the standard 5V, it will help reduce the conduction loss of the converter. The low side grille voltage from 6 V fluctuates to NMOS, and then turns off NMO. BQ24105 has two backs of P-MOSFET on the back of the high-pressure side. Enter P-MOSFET to prevent the battery from discharging, and IN is lower than BAT. The second P-MOSFET is manifested as the switch to control the FET, and there is no need to hold a capacitor.

The internal high -side sensing field effect transistor (FET) sensing circulation current limit. The threshold is set to nominal 3.6A peak current. Whether the synchronous or synchronous side FET also has low current restrictions. This threshold is set to 100mA, and the low -side NMOS is turned off before the current reverse to prevent battery discharge. When the current of the low -border effect transistor is greater than 100 mAh, synchronous operations are used to minimize power loss.

Temperature appraisal

The BQ switch continuously monitor the battery temperature by measuring the voltage between the TS pin and the VSS pin. The negative temperature coefficient thermistor (NTC) and external compressors usually generate this voltage. The BQ switch compares this voltage with the internal threshold to determine whether it is allowed to charge. To start the charging cycle, the battery temperature must be within the range of V (LTF) -V (HTF) threshold. If the battery temperature exceeds this range, the BQ switch will be suspended and waited until the battery temperature is within the range of V (LTF) -v (HTF). During the charging cycle (pre-charging and fast charging), the battery temperature must be within the range of V (LTF) -V (TCO) threshold. If the battery temperature exceeds this range, the BQ switch will be suspended and waited until the battery temperature is within the range of V (LTF) -v (HTF). The BQ switch is closed by turning off the PWM and keeping the timer value (that is, the timer is not reset at the pause state). Pay attention, external resistance divisionThe bias of the pressure device comes from VTSB output. The constant voltage between the V (LTF) -V (HTF) threshold is applied to the TS pin. The temperature sensing function will be disabled.

Battery pre -processing (pre -charging)

When power is powered on, if the battery voltage is lower than the VlowV threshold, BQ switching The device applies a pre -charged current IPRECHG to the battery. This feature resurrected deeply discharged cells. In the adjustment phase, the BQ switch starts the safety timer TPRECHG. If the VlowV threshold is not reached within the timer time, the BQ switch will turn off the charger and display the failure on the STATX pin. In the case of failure, the BQ switch reduces the current to Idetect. Idetect is used to detect battery replacement. Clear failure through POR or replace the battery.

The size of the pre -charged current IO (Prechg) is determined by the value of the programming resistor R (ISET2) connected to the ISET2 pin.

where:

RSNS is an external current detection resistor

V (ISET2) is the output voltage of the Iset2 pin

K (Iset2) is V/A gain factor

V (Iset2) and K (ISET2) in the electrical characteristic table.

The battery charging current

The resistor R (SNS) and the resistor R (ISET1) connected to the ISET1 pin were set to determine the battery charging current IO (charging).

In order to set the current, the regulating threshold Vireg based on the resistance based on the resistance was selected. When Vireg is between 100 MV and 200 MV, the best accuracy is reached.

If the result is not a standard sensor resistance value, please select the next larger value. Use the selected standard value to solve Vireg. Once you select the sensing resistance, you can use the following square to calculate the ISET1 resistor:

Battery voltage adjustment

voltage adjustment feedback generated through the BAT pin. The input is directly connected to the positive electrode of the battery pack. BQ switch monitor battery pack voltage between BAT and VSS pin.

The output regulating voltage specifications are:

where R1 and R2 are resistance divisors from BAT to FB and FB to VSS.

The charging threshold voltage regulations are:

Charging termination and charging

At the charging levelDuan, BQ monitor the charging voltage. Once the termination threshold ITERM is detected, BQSWITCHER will terminate the charging. The terminal current level is selected from the value of the programming resistor R (ISET2) connected to the Iset2 pin.

where:

R (SNS) is an external current detection resistor

vterm is the output of the ISET2 pin

[

123] K (Iset2) is the A/V gain coefficient

Vterm and K (ISET2) specify

as a safe backup in the electrical characteristic table. Charging timer. The charging time is programmed by the capacitor value connected between the TTC pin and GND according to the following formulas:

where:

C (TTC) is connected to the connection to the connection to The capacitor of TTC pin

K (TTC) is multiplication

When one of the following situations is detected, a new charging cycle will be activated:

battery; battery; The voltage is lower than the VRCH threshold.

power -on reset (POR), if the battery voltage is lower than the VRCH threshold

CE switch

TTC pin, As described below.

In order to disable charging termination and secure timer, users can pull TTC input below the VTTC_EN threshold. More than this threshold will enable the termination and safety timer function and reset the timer. Binding TTC high only disables security timers.

Sleep mode

If the VCC pin is removed from the circuit, the BQ switch enters the low -power dormant mode. This function prevents battery power from exhausted without VCC.

Charging status output

The output of the opening of the drainage STAT1 and STAT2 indicates the operation of various chargers, as shown in Table 1. These state pins can be used to drive LEDs or communicate with host processors. Note that the level indicates that the leakage transistor is turned off.

PG output

Discost PG (good power supply) indicates when the AC-To-DC adapter (ie VCC) exists. When the dormant mode exits threshold VSLP-EXIT, the output is opened. This output is closed in the sleep mode. PG pins can be used to drive LEDs or communicate with host processors.

CE input (charging enable)

CE digital input is used to disable or enable the charging process. The A-C pin charging level is high and this signal is disabled. The high to low conversion on this pin will also be resetThere are timers and fault conditions. Note that the CE pin cannot be pulled to the VTSB voltage. This may lead to power -on.

timer failure recovery

As shown in Figure 6, Bqswitcher provides a recovery method to handle the timer failure. The following summarizes this method.

Condition 1: VI (BAT) is higher than the charging threshold (Voreg-VRCH) and occurs over time failure.

Recovery method: BQSWITCHER wait for the battery voltage to be lower than the charging threshold. This may be caused by battery load, self -discharge, or disassembling battery. Once the battery is lower than the charging threshold, the BQ switch will remove the fault and enter the battery missing detection program. The POR or CE switch can also clear the failure.

Condition 2: The charging voltage is lower than the charging threshold (Voreg -VRCH), and the timeout failure

recovery method: In this case, the BQSWITCHER applies Idetect 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 battery voltage is higher than the charging threshold, the BQ switch will disable the Idetect current and perform the recovery method described in the condition 1. Once the battery is lower than the charging threshold, the BQ switch will remove the fault and enter the battery missing detection program. The POR or CE switch can also clear the failure.

Output overvoltage protection

The BQ switch provides a built -in overvoltage protection to protect equipment and other components from damage. If the battery voltage is too high, if the battery suddenly removes. When the pressure is detected, this function will close the PWM and STATX pins. Once the VIBAT drops to the charging threshold (Voreg -vrch), the fault is cleared.

Electrochemical, capacitor and sensor selection guidelines

BQ switch provides internal circuit compensation. In this scheme, when the LC resonance frequency FO is about 16kHz (8KHz ~ 32kHz), the stability is the best. Formula 9 can be used to calculate the value of the output inductance and capacitance. Table 3 summarizes the typical composition value of various charging rates.

Battery detection

For the application of removable battery packs, Bqswitcher provides a battery lack detection solution to in order Reliable to detect the insertion and/or remove of the battery pack.

After the fast charging, after the battery is charged, the voltage at the battery pin is kept above the battery charging threshold (Voreg -vrch). When the voltage on the BAT pin drops to the charging threshold, whether it is due to the battery load or due to the removal of the battery, the BQ switch starts the battery deficiency detection test. TestIncluding enable detection current IDISCHARGE1 for a period of time, and check whether the battery voltage is lower than the short -circuit threshold vshort. After that, the tail IWAKE will last for a period of time and check the battery voltage again to ensure that it is higher than the charging threshold. The role of this current is to try to turn off the battery set protector (if one of them is connected to the BQ switch).

The discharge and charging test showed that there was a battery deficiency failure at the STAT pin. Any test failure will start a new charging cycle. Without a battery, the voltage on the battery pins usually rises and decreased infinitely between 0V and VOVP threshold.

Battery detection example

Under the following discharge conditions, the battery discharge should not exceed the maximum value:

A. discharge ( IDISCHRG1 u003d 400 μA, TDISCHRG1 u003d 1S, vshort u003d 2V):

B, Tail Stream (IWake u003d 2mA, TWAKE u003d 0.5s, Voreg-VRCH u003d 4.1V):

Based on these calculations, in order to ensure the normal operation of the battery detection scheme, the recommended maximum output capacitor is 100 μF, which will allow process and temperature changes.

FIG. 9 shows the battery detection scheme when inserting into the battery. Channel 3 is the output signal, and channel 4 is the output current. The output signal is switched between Voreg and GND until the battery is inserted. Once the battery is detected, the output current will be increased from 0A to 1.3A, which is the programming charging current of this application.

FIG. 10 shows the battery detection scheme when removing the battery. Channel 3 is the output signal, and channel 4 is the output current. When the battery is removed, due to the energy stored in the inductor, the output signal will rise and will exceed the Voreg -VRCH threshold. At this time, the output current is 0A, the IC termination of the charging process, and open IDISCHG2 for TDISCHG2. This will cause the output voltage to drop below the Voreg -vrchg threshold, thereby trigger the battery deficiency and start the battery detection scheme.

The current detection amplifier

provides a current detection amplifier function that converts the charging current to DC voltage. Figure 11 is a frame diagram of this feature.

The voltage on the Iset2 pin can be used to calculate the charging current. Formula 12 shows the relationship between Iset2 voltage and charging current:

This function can be used to supervise during the current regulation stage (only fast charging) and voltage adjustment phase supervision stage.Measure the charging current (Figure 12). The diagram of the application circuit of the waveform is shown in Figure 14.

The design example of the BQ switch system

The following section provides a detailed system design example of BQ24100.

System design specifications:

vin u003d 16v

vbat u003d 4.2V (1 core)

#8226 ; Icharge u003d 1.33 amp

iprecharge u003d iterm u003d 133 mia

Safety timer u003d 5 hours

inductor sensor Tattoos current u003d 30%of fast charging current

initial installation temperature u003d 0 ° C to 45 ° C

1. Determine the inductor value of the specified charging current ripple ripple (LOUT):

Set the output sensor to the standard 10 μH. Calculate the total ripple current with 10 μH inductor:

Calculate the maximum output current (peak current):

Use The saturated current is more than 1.471A, a standard 10 μH induction (that is, Sumida CDRH74-100).

2. Use 16 kHz as a resonance frequency to determine the output capacitance value (OUT):

Use standard value 10 μF, 25V, X5R, ± 20%ceramic ceramics Capacitor (that is, Panasonic 1206 ECJ-3YB1E106M

3. Use the following formula to determine sensing resistance:

In order %), Set VRSN between 100 MV and 200 MV. Use VRSNS u003d 100 MV and calculate the value of the sensor.

This value is not the standard of the resistance standard Value. If this happens, select the next larger value. In this example, it is 0.1 #8486;. Use the same equation (15), and the actual VRSN is 133mV. The calculation of the power consumption resistor measured the resistor in the calculation. :

Select the standard value 100 m #8486;, 0.25W 0805, 1206 or 2010 size, high-precision sensor resistor. 4. Use the following formula to determine iSET 1 resistor:

Select the standard value 7.5 k #8486;, 1/16W ± 1%resistor (ie Vishay CRCWD0603-7501-F).

5. Use the following formula to determine the Iset 2 resistor:

Select the standard value 7.5 k #8486;, 1/16W ± 1%resistor ( That is Vishay Crcwd0603-7501-F).

6. Use the following formula to determine the TTC capacitor (TTC) of 5.0 hours of safety timer:

Select the standard value 100nf, 16V, X7R, ± 10 10 %Ceramic capacitor (ie Panasonic ECJ-1VB1C104K). With this capacitor, the actual safety timer is 4.3 hours.

7. Determine the TS resistance network with a working temperature range of 0 ° C to 45 ° C.

Assuming that there is a 103AT NTC thermistor on the battery pack, use the following procedures to determine the value of RT1 and RT2:

123] Application information

Charging the battery and power supply system without affecting the battery charging and terminal connection.

The BQ switch is designed as an independent battery charger, but it can be easily adapted to the system load supply, and at the same time consider some small problems.

Advantage:

1. The charger controller is based on the current of the current fluid resistor (so the pre -charging, constant current, and terminals can work normally), not affected by the system load Essence

2. The input voltage has been converted from the input end to an effective system voltage.

3. No additional external FET is needed to switch the power to the battery.

4.TTC pin can be ground to disable the terminal and keep the converter running and the battery fully charged, or let the switch end when the battery is full, and then exhaust the battery through the induction resistor.

Other problems:

1. If the system load current is large (≥1A), the decrease in IR on the battery impedance will cause the battery voltage to drop below the refresh threshold and start a new charging. The charger will end due to the low charging current. Therefore, the charger will circulate between charging and termination. If the load is small, the battery will have to discharge to refresh the threshold, which will cause a slower cycle. Note that the grounded TTC pins keep the converter continued to run.

2. If the TTC is grounded, the battery voltage is kept at 4.2 V (and the full chargingThe battery is not much different from the air load).

3. When discharging the system through sensing resistance, the efficiency decreases by 2-3%.

Use BQ24105 to charge the LIFEPO4 battery

Lifepo4 battery has many unique features, such as high thermal outlet temperature, discharge current capacity and charging current. These special features make it very attractive in many applications, such as electric tools. The recommended charging voltage is 3.6V and the termination current is 50mA. Figure 15 shows the application circuit using BQ24105 as a single battery LIFEPO4. The charging voltage is 3.6V and the charging voltage is 3.516V. The fast charging current is set to 1.33A and the termination current is 50mA. This circuit can easily change to support the application of two or three units. However, there is only a difference between the adjustment set value and the charging threshold, so that it will frequently enter the charging mode at a small load current. This can be solved by reducing the charging voltage threshold to 200 millivolves, so that more energy is released before the battery enters the charging mode again. For more details, please refer to the application report and charge the Lifepo4 battery (SLUA443) with BQ24105/25. The charging threshold should be selected according to the actual application.

The switch is encapsulated in the thermal increase MLP package. The package includes a hot pad to provide effective thermal contact between IC and printing circuit board (PCB). The complete PCB design guide of this packaging is provided in the application report of: QFN/SON PCB attachment (SLUA271).

The most common measurement method of packaging thermal performance is from the chip to the heat impedance (θJa) from the chip to the surface (environment). The mathematical expression of θja is:

where:

tj u003d chip knot temperature

ta u003d ambient temperature

] P u003d Equipment power consumption

The factors affecting θja measurement and calculation are:

Whether the device is installed on the board

, Ingredients, thickness and geometric shapes

Equipment direction (horizontal or vertical)

environmental air volume and air flow around the device

Whether the other surfaces are close to the measured device

The power consumption P is a function of the internal power field effect of the transistor of the transistor. Can be calculated based on the following formula:

p u003d [vin × lin-vbat × ibat]

Due to the charging mode of lithium XX batteries, the maximum power consumption usually appears in theAt the beginning of the charging cycle, when the battery voltage is at the lowest. (See Figure 5.)

PCB layout Consider

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

In order to obtain the best performance, the power input capacitor connected from the input end to PGND should be as close to the BQ switch as possible. The output sensor should be placed directly above the integrated circuit, and the output capacitor is connected between the PGND of the inductors and the integrated circuit. The purpose is to minimize the circuit area from the OUT pin to the LC filter and then back to the GND pin. The sensing resistance should be close to the level of the inductance and output capacitance. The detection lead wiring connected to R (SNS) is returned to IC, and the (minimum circuit area) is close to each other or overlap each other on the adjacent layer (do not detect the leading lead through the high current path wiring). If the long (inductive) battery is used, the optional capacitor is used downstream in the lower reaches of the sensor.

Place all small signal components (CTTC, RSET1/2, and TS) near its respective IC pins (do not place components to avoid wiring interrupt power level). All small control signals should stay away from the large current path.

PCB should have a ground plane (circuit), which is directly connected to the circuit of all components by passing through the hole (three pores of each capacitor of the power -class capacitor, three pores of IC PGND, Each capacitor of a small signal component). Star-ground design methods are usually used to keep circuit block current isolation (high-power/low-power small signal), thereby reducing the problem of noise coupling and grounding rebound. A single ground design result is very good. Due to this small layout and a single ground plane, there is no ground rebound problem, and the components are separated to minimize the coupling between the signals.

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 PGND pin should be connected to the ground plane to return the current through the internal low -side FET. The heating hole #8482 in the integrated circuit power board provides a return path connection.

BQ switch is encapsulated in the heat -enhancing MLP packaging. The package includes a hot pad to provide effective thermal contact between IC and PCB. The complete PCB design guide of this packaging is provided in the application report of: QFN/SON PCB attachment (SLUA271). 6 10-13 dense ear-mounted holes are the minimum of the proposed minimum number, placed on the power board of IC, connecting it to the grounding thermal plane on the other side of the PWB. The potential of the plane must be the same as the VSS and PGND of the IC.

Examples about good layout, please refer to the user guide SLU200.

Polkida: All waveforms are lout (iC) Pack) Collection. VIN u003d 7.6 V, the battery is set to 2.6 V, 3.5 V and 4.2 V. When the top switch of the converter is opened, the waveform is ~ 7.5 V. When it is closed, the waveform is close to the ground. Please note that the bell on the edge of the switch is small. This is due to the compact layout (minimum circuit area), the shielding induction (closed iron core), and the use of the low -induced range ground line (that is, short circuit with the minimum circuit).

Pre-charging: The current is very low at the pre-charged; therefore, the bottom synchronous FET is closed after its shortest connection time, which explains #8777; 0V and -0.5 The step between V. When the bottom FET and the top FET are closed, the current through the body diodes of the bottom FET, causing the diode to fall below the ground potential. The initial negative peak was a delay of the opening of the bottom field effect transistor. This is to prevent the penetrating current when the top field effect transistor is closed.

Quick charging: This was captured during the constant current stage. These two negative peaks are the result of a brief delay when switching between the top and the bottom. First break and then the action can prevent current breakdown, and the body diode is reduced below the land power within the disconnection time.

Voltage adjustment and charging close to the termination: Note that this waveform is similar to the pre -charged electric waveform. The difference is that the battery voltage is high, so the duty cycle is slightly higher. The bottom field effect of the crystal pipe is maintained for a longer time, because there are more current loads during the pre -charging period; it takes longer to slow down the inductor current to the current threshold, and the synchronous field effect tube is disabled.