Features

5.5 × 3 mm small packaging

designed for portable applications for single battery lithium ions or lithium polymers

Integrated dynamic power supply path management (DPPM) function, allows the AC adapter to supply the system and charge the battery at the same time

the power supply supplementary mode allows battery supplementary AC input current

Independent power supply (AC adapter or BAT)

support the total current of Gundam 2 amp

Heat of charging control

] LED or system interface charging status output indicator charging and fault status

reverse current, short circuit and heat protection

Application

smartphone and PDA

mp3 player

digital camera and handheld device [ 123] Internet Equipment

Instructions

BQ24070

The device is a highly integrated lithium ion linear charger and system power path management equipment, For portable applications with limited space. BQ24070 provides DC power supply (AC adapter) power path management in a single -chip device. It has autonomous power selection, power FET and current sensor, high -precision current and voltage adjustment, charging status and charging terminal.

BQ24070 supply the system, while charging the battery independently. This function reduces the charging and discharge cycle of the battery, allows the correct charging to terminate, and allows the system to run without a battery pack or defective battery pack. This function also allows the system to start from the external power supply in the case of deep discharge of the battery pack. The focus of integrated circuit design is to provide a continuous power supply to the system when AC adapters or battery power are available.

Power flowchart (1)

(1), see the function box diagram 2.

(2), P-FET backcut body diodes are broken to prevent body diode conduction.

Mode pins select the priority of the input source. If the input source is not available, select the battery as the source. In the case of high mode pins, BQ24070 tries to charge from the input terminal at the rate of ISET1 pin settings. In the mode of mode pins, BQ24070 defaults to the rate of USB charging. This function allows the use of a single connector (mini USB cable), and the host is based on the source of the connected (AC adapterOr USB port) programming mode pins. Table 1 summarizes the mode pin function.

(1), the battery charging ratio is always set up by ISET1, but it may be reduced due to limited input source (ISET2 USB mode) and iOUT system load.

Order information

(1), the latest software package and ordering information, please refer to the software package options at the end of this document.

(2), the RHL software package provides the following options:

R-rolling and scrolling, 3,000 devices per volume.

T-roll bands and rolls of 250 devices per volume.

(3), this product is compatible with ROHS, including the lead concentration of the lead exceeding 0.1%of the total weight of the product, which is suitable for the specified lead -free welding process. In addition, this product uses a packaged material without halogen, including bromine (br) or 锑 (SB), which accounts for more than 0.1%of the product.

(4), if AC LT; VO (OUT-Reg), then AC is connected to the OUT pin through P-FET (Q1).

Figure Figure

Function description

Charging control BQ24070 supports precision lithium for single battery portable equipment Ion or lithium polymer charging system. See the typical charge distribution diagram, application circuit and operation flowchart in Figure 1 to 3.

Autonomous power selection, mode control pins

Mode input low, BQ24070 defaults Iset2 pin limit (100 mAh for ISET2 low, 500 mAh for ISET2 high). If the input source is not available, select the battery as the source.

Starting order

In order to facilitate system startup and USB enumeration, the BQ24070 provides a proprietary startup sequence. When the BQ24070 was first powered on, this function enabled the 100mAh USB charging rate to last about 150 milliseconds (t (start)), and ignore the ISET2 and CE input settings. At the end of this period, the BQ24070 executes CE and ISET2 input settings. Table 1 shows the time to enable this function. See Figure 8.

Power path management

BQ24070 supply system power, and at the same time, it is independent of battery charging. This function reduces the charging and discharge cycle of the battery, allows the correct charging to terminate, and allows the system to run without a battery pack or defective battery pack. This function gives the system input power priority, allowing the system to use depth to placeThe battery pack power supply. The working principle of this function is as follows.

S situation 1: AC mode (mode high)

System power

In this case, the system load passes through the internal transistor tube through internal transistor tube Q1 Direct power supply from the AC adapter (see Figure 4). If the output voltage of the system is lower than 4.V, the output voltage of the system drops to 4.V.

Charging Control

In the communication mode, charging the battery through the switch Q2 according to the charging ratio set on the ISET1 input.

Dynamic power supply path management (DPPM)

This function monitor whether the output voltage (system voltage) causes input power loss due to power failure, current limit or disconnect input power supply. If the input current is limited, the voltage on the OUT pin drops to the preset value V (DPPM) × SF, the battery charging current will be reduced until the output voltage stops decrease. DPPM control attempts to reach a stable state. At this time, the system obtains the required current and charges the battery with the remaining current. There is no active control of the current of the system; therefore, if the current required by the system exceeds the current that the input can be provided, the output voltage will be reduced to the level slightly lower than the battery voltage. Q2 will turn on to supplement the input current of the system. DPPM has three main advantages.

1. If the average system load is medium compared to its peak power, this function allows designers to select wall adapters with lower power. For example, if the peak system load is 1.75 A, the average system load is 0.5 A, and the fast charging current of the battery is 1.25 A, the total peak demand may be 3 A. For DPPM, you can choose 2 A adapter instead of 3.25 A power supply. When the peak load of the system is 1.75A and the charging load is 1.25A, the voltage of the smaller ornament is reduced until the output voltage reaches the DPPM adjustment voltage threshold. The charging current is reduced until the output voltage no longer decreases. The system charging is 1.75A, the battery charging current is reduced from 1.25A to 0.25A. When the peak load of the system drops to 0.5A, the charging current is restored to 1A, and the output voltage resumes normal values.

2. Compared with configuration without DPPM, using DPPM can save electricity. Without DPPM, if the system current plus the charging current exceeds the current limit, the output is pulled down to the battery. Linear charger consumes unused power (VIN-Vout) × ILOAD. The current is still very high (under the current limit), and the voltage drop is large to reach the maximum power consumption. With DPPM, the system's voltage is lower (VIN-V (DPPM-Reg)), which means higher efficiency. In these two cases, the efficiency of charging batteries is the same. Its advantages include small power consumption, low system temperature, and high overall efficiency.

3.DPPM maintenance system electricityRegardless of the cause, the voltage decreases, if possible. It implements this by reducing non -critical charging load while maintaining the maximum power output of the adapter.

Note that DPPM voltage V (DPPM) programming is as follows:

where:

r (dppm) is connected to DPPM and VSS External resistor between pins.

i (DPPM) is an internal current source.

The proportion factor is specified in the table.

Safety timer adjusts dynamically in DPPM mode. The voltage on the Iset1 pin is proportional to the charging current of programming. When the programmatic charging current decreases, the timer clock slows down due to DPPM, ISET1 and TMR voltage, thereby prolonging the safety time. V (TMR) 2.5 V at normal working; and when the clock slows down, V (TMR) is reduced. When V (TMR) 1.25 V, the value of the safety timer is 2 times the value of the normal operating timer. See Figure 5 to Figure 6.

Case 2: USB mode (mode L)

System power

In this case, the system load is powered by the internal switch Q1 from the USB port (see Figure 4 4 u200bu200b(see 4 To. Note that in this case, Q1 adjusts the total current to 100 mA or 500 mA, as selected on the ISET2 input. Output, vout, adjustment to 4.4 V. The power management of the system is responsible for keeping its system load below the selected USB current level (if the battery power is seriously insufficient or missing). Otherwise, the output will drop to the battery voltage; therefore, the system should have a low power consumption mode for USB power applications. The DPPM function is reduced to below the programming settings by reducing the charging current to prevent the output from the battery charging current.

Charging control

In USB mode, Q1 will adjust the input current to the value of the ISET2 pin selection (0.1/0.5 A). The charging current of the battery is set by the Iset1 resistor (usually greater than 0.5 A). Because the charging current is commonly programmed as a current that limits the current than the USB current limit, the output voltage is reduced to the battery voltage or DPPM voltage, which is subject to higher. If the DPPM threshold is reached first, the charging current will be reduced until VOUT stops falling. If VOUT drops to the battery voltage, the battery can supplement the input current to the system.

Dynamic power path management (DPPM)

The working principle is the same as the situation 1, but Q1 is limited to the USB current level selected by the ISET2 pin.

Note that DPPM voltage V (DPPM) programming is as follows:

]

Among them:

R (DPPM) is an external resistor connected between DPPM and VSS pins.

i (DPPM) is an internal current source.

SF is the proportional factor specified in the specification table.

特征图

图5显示了输出电流（IOUT）增加时的DPPM和电池补充模式；通道1（CH1）VAC 5.4 V；通道2（CH2）VOUT；通道3 (CH3) IOUT 0 to 2.2 A to 0 a; Channel 4 (CH4) vbat 3.5 v; i (pgm-chg) 1 A. In typical operations, BQ24070 (VOUT 4.4 Vreg), through the overload conditions and recovery of AC adapters. AC input settings to ~ 5.1 V (1.5 A current limit), i (CHG) 1 a, v (dppm-set) 3.7 v, v (dpm-out) 1.15 × v (dpm-set) 4.26 V , Vbat 3.5 v, mode h, USB input is not connected. The output load increases from 0 a to ~ 2.2 a, and then return to 0 A, as shown in the bottom waveform. When the iOUT load reaches 0.5A, with the 1-A charging current, the adapter starts the current limit, and the output voltage drops to the DPPM-OUT threshold 4.26V. This is the DPPM mode. The output voltage of the AC input through the AC field effect tube tracks the output voltage. Then adjust the battery charging current as needed to prevent further decline in the output voltage. Once the output load current exceeds the input current, the battery must supplement too much current, and the output voltage is dropped below the battery voltage through the voltage of the battery field effect tube. This is a battery supplement mode. When the output load current is reduced, the operation is opposite as shown in the figure. If the DPPM-OUT voltage is set to below the battery voltage, during the input current limit, the output drops directly to the battery voltage.

Under the USB operation, when the load exceeds the input current threshold of programming, a similar mode is observed. If the output load exceeds the available USB current, the output immediately enters the battery supplement mode.

FIG. 6 shows that when the mode is switched to 500 μs. The power supply is transmitted from the communication to the USB and then transmitted to the communication; the channel 1 (CH1) VAC 5.4 V; the channel 2 (CH2) v (USB) 5 V; the channel 3 (CH3) vout; the output current iOut 0.25 A; the channel 4 (CH4) VBAT 3.5 V; i (PGM-CHG) 1A. When the mode becomes lower (1st div), the AC FET opens and the output decreases until the USB FET opens. Turn off the source power supply before turning on the replacement power supply. The discharge rate at the output end is system capacitanceThe function of the load. Please note that when AC and USB input are in a load state, the IR of the cable decreases. In part 4, the output reached a steady -state operation at the DPPM voltage level (the charging current decreased due to the limit of the USB input current). In area 6, the model becomes high, the USB field effect tube is closed, and the exchange field effect tube is opened. The output is restored to the specified value, and the battery is restored to the program level.

FIG. 7 shows that the battery is inserted to power power; Channel 1 (CH1) VAC 0 V; Channel 2 (CH2) vusb 0 V; Channel 3 (CH3) Vout; output current iOUT 0.25 A, if Vout GT; 2 V; Channel 4 (CH4) vbat 3.5 V; C (DPPM) 0 PF. When there is no power and inserted into the battery, if there is no load ( lt; 10 mAh load) on the output, the output will track the battery voltage, as shown in the figure. If there is a load that makes the output below 200 mm of the battery of the battery, it indicates that there is a short -circuit state. At this point, the load must be removed to recover. A capacitor can be placed on the DPPM tube foot to delay the short -circuit mode and obtain an unlimited (non -restricted) current.

FIG. 8 shows the startup and power -on through USB; Channel 1 (CH1) V (USH) 0 to 5 V; Channel 2 (CH2) USB input current (0.2 A/div); mode low; CE high; ISET2 high; vbat 3.85 v; v (dppm) 3.0 v (v (dppm) × 1.15 lt; vbat, otherwise DPPM mode will increase duration). When using a USB power supply (if there is no AC power supply), the CE pin and the ISET2 pin are ignored during the launch, and the maximum input current of the OUT or BAT pin is 100 mAh. After the start time, IC implements CE and ISET2 pins according to programming.

Battery temperature monitoring

BQ24070 to continuously monitor the battery temperature by measuring the voltage between TS and VSS pins. The internal current source is the most common 10 k #8486; negative temperature coefficient thermistor (NTC) provides bias (see Figure 9). The device compares the voltage on the TS pin with the internal V (LTF) and V (HTF) threshold to determine whether it is allowed to charge. Once the temperature of the threshold of V (LTF) and V (HTF) is detected, the device will immediately suspend charging. This device is stopped by closing the power field effect tube and keeping 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 103AT thermistor is 0 ° C to 45 ° C. However, users can increase the temperature range by adding two external resistors. See Figure 10.

Battery pre -processing

During the charging cycle, if the battery voltage is lower than the V (low V) threshold, the BQ24070 will apply the battery to the battery to pre -charged current IO (Prechg). This feature resurrected deeply discharged cells. The resistance RSET connected between Iset1 and VSS determines the pre -charging rate. The specification table specifies V (Prechg) and K (set) parameters. Please note that this is suitable for the communication mode and USB mode charging.

BQ24070 starts a safe timer T (Prechg) during the adjustment phase. If the V (low voltage) threshold is not reached during the timer cycle, the BQ24070 is off the charger, and the failure is displayed on the STAT1 and STAT2 pins. If the charging current decreases through DPPM or heat adjustment, the timeout time is extended. For more details, see the timer failure recovery part.

Battery charging current

BQ24070 provides a chip current adjustment and programmable setting value. The resistance RSET connected between Iset1 and VSS determines the charge level. The charging level can be reduced to make the system give priority to input current (see DPPM). The specification table specifies the V (set) and K (set) parameters.

When supplying power from the USB port, the available input current (0.1 A/0.5 A) is usually smaller than the (ISET1) charging current, so the DPPM function is trying to reduce charging by reducing charging Current to prevent the output from being pulled down.

Only during the operation of the communication mode (mode high), the charging level can be changed to coefficient 2 by setting the ISET2 pin high (complete charging) or low (semi -charging). In the semi -constant charging mode, the voltage on the Iset1 pin is divided by 2. Note that in a low mode, the Iset2 pin controls only 0.1 A/0.5 A USB current.

For more details, see the part of the title of the power path management.

Battery voltage adjustment

Voltage adjustment feedback via the BAT pin. The input is directly connected to the positive electrode of the battery pack. BQ24070 monitor battery pack voltage between BAT 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.

If there is no battery, the battery pins are circulated between charging (VO (REG)) and charging (battery charging threshold, ~ 4.1 V).

Please see the battery inserted into the power supply in Figure 7.

As a safe backup, BQ24070 also monitor the charging time in the charging mode. If the charging is not terminated within this time period T (CHG), the BQ24070 is closed to the chargingThe device shows failure on STAT1 and STAT2 pin. For information about extending the security timer during the DPPM operation, see the DPPM operation under the case 1. For more details, see the Timer Fault Recovery section.

Temperature adjustment and thermal protection

In order to maximize the charging rate, the BQ24070 has a knotting temperature adjustment circuit. If the power consumption of the integrated circuit causes the knot temperature higher than the TJ (REG) threshold, the BQ24070 will save the charging current so that the knot temperature will be kept near the TJ (REG) threshold. To avoid errors, the detection function is banned in this mode.

BQ24070 also monitor the chip temperature TJ. If TJ exceeds T (SHTDWN), the OUT pin is broken from the input end. This operation continues until TJ drops below the lagging level specified in the specification table.

The battery supplement mode is not available. If the input power is insufficient, the Q2 effect transistor continues to connect the battery to the output (system); however, the short -circuit protection circuit limits the battery discharge current, thereby not exceeding the maximum power consumption of the component under typical design conditions.

Charging timer operation

As a safe backup, BQ24070 monitor the charging time in the charging mode. If the termination threshold is not detected in the time period T (CHG), the BQ24070 will turn off the charger and display the failure on the STAT1 and STAT2 pin. The resistance RTMR connected between TMR and VSS determines the cycle of the timer. The K (TMR) parameters are specified in the specification table. In order to disable the charging timer, eliminate the RTMR, and connect the TMR pin directly to the VREF pin. Please note that this operation will eliminate all security timers and clear all timer failures. The TMR pin should not be kept floating.

When it is in a thermal regulation mode or DPPM mode, the BQ24070 dynamic adjustment timer cycle is provided to provide the extra time required for the battery to fully charge. This proprietary function aims to prevent early or errors. The maximum charging time T (CHG-TREG) in this mode is calculated by Formula 6.

Please note that because this adjustment is dynamic and changes with the changes in the environmental temperature and charging level, the timer clock is adjusted. If the above equation is not included during the charging cycle, it is difficult to estimate the total safety time. Therefore, understanding the theory of anti -proportional adjustment of safety time and charging current, and the rated current of the battery is hours, and the safety time can be adjusted appropriately.

V (set) parameter specifies in the specification table. V (SET-TREG) is the voltage on the ISET pin in the hot adjustment or DPPM mode, which is a function of the charging current. ((Please note that the charging current is dynamically adjusted in thermal regulation or DPPM mode. )

All mud removal time is also adjusted proportional to T (chg-Treg).

Charging termination and charging

BQ24070 monitor the voltage on the ISET1 pin during voltage adjustment to determine when to terminate #169;/10–250 mv). Once the termination threshold I (terminology) is detected, the BQ24070 terminates charging. The resistor programming settings connected between Iset1 and VSS (RSET) set the fast charging current #169; VISET1 2.5 V), thereby programming C/10 and C/25 current terminal threshold levels. The specification table specifies V (terminology) and K (set) parameters. Please note that this is suitable for communication and USB charging.

After the charging is terminated, once the voltage on the BAT pin is lower than the V (RCH) threshold, the BQ24070 will restart the charging. This function can always be in a full capacity state.

Sleep and standby mode

If you remove the input from the circuit, the BQ24070 charger circuit will enter a low -power dormant mode. This function prevents the battery into BQ24070 without the input power supply. Please note that in the dormant mode, Q2 keeps open (that is, the battery is connected to the OUT pin) so that the battery can continue to power the system.

If the input power exists and the CE input is low, the BQ24070 enters the low -power standby mode. In this pause mode, the internal power supply FET Q1 (see Figure 4) is closed, and the BAT input is powered by the system through the OUT pin. This function aims to limit the power consumed from the input power supply (such as USB hanging mode).

Charging status output

Open drain (OD) STAT1 and STAT2 output indicates various chargers operations, as shown in Table 2. 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. Note that this assumes that CE high.

PG, the output (good power)

When the leakage of the road leakes, PG indicates when there is an input power supply and higher than the battery voltage. When exiting the dormant mode (the input voltage is higher than the battery voltage), the corresponding output is opened (low). This output is closed in the dormant mode (the leak opening road). PG pins can be used to drive LEDs or communicate with host processors. Note that the level indicates that the leakage transistor is cut off.

CE input (chip enable)

CE (chip enable) digital input is used to disable or enable IC. The high -level signal on this pin allows the chip to work, and the low level signal makes the device fail and start the standby mode. CWhen the E input is low and there is input, the BQ24070 enters the low -power standby mode. In this hanging mode, the internal power supply FET Q1 (see square frame) is turned off; the battery (BAT pin) is powered by the system through Q2 and OUT pins. This function aims to limit the power consumed from the input power supply (such as USB hanging mode).

Charging disable function

DPPM input can be used to disable the charging process. This can be achieved by floating DPPM pins.

timer failure recovery

As shown in Figure 3, the BQ24070 provides a recovery method to handle the timer failure. The following summarizes this method:

Condition 1: The charging voltage is higher than the charging threshold (V (RCH)), and the timeout failure occurs.

Recycling method: BQ24070 wait for the battery voltage to drop below the charging threshold. This may be caused by battery load, self -discharge, or disassembly of battery. Once the battery is lower than the charging threshold, the BQ24070 will clear the fault and start a new charging cycle. The POR or CE switch can also clear the failure.

Condition 2: The charging voltage is lower than the charging threshold (V (RCH)), and the timeout failure occurs.

Recycling method: In this case, the BQ24070 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 battery voltage is higher than the charging threshold, the BQ24070 will disable the recovery method described by the I (fault) current and perform conditions 1. Once the battery is lower than the charging threshold, the BQ24070 will clear the fault and start a new charging cycle. The POR or CE switch can also clear the failure.

Short -circuit recovery

Output can undergo two types of short -circuit protection, one is related to input, and the other is related to the battery.

If the output voltage drops below ~ 1V, it means that the input is short -circuit and the input FET Q1 is closed. In order to recover from this state, the 500Ω upper pull resistor of the input end is applied (switched) to the output end. In order to restore, the load on the output must reduce {road gt; 1V × 500 #8486; (vin -vout)}, so that the pull -up resistance can increase the output voltage to more than 1V so that the input FET can be re -connected.

If the output voltage is lower than the battery voltage 200 millivoltti, the battery field effect transistor Q2 is considered a short circuit, and the battery field effect transistor is closed. In order to recover from this state, there is a 10mAh current source from the battery to the output. Once the output load is reduced, the output can be received within 200 millivolves of the battery in the battery, and the field effect transistor can be reopened.

If the short-circuit is eliminated, and the minimum system load is still too large [R LT; (VBAT-200MV)/10 MA], short -circuit protection may be temporarily invalidated. If the voltage on the DPPM pin is lower than 1 V, it can be disabled for short -circuit protection (it is recommended to use it in a short time). The pins pulse below 1 V and lasting for a few microfinances should be enough to recover.

This short -circuit disable function is mainly used to power on the battery. Because the BAT input voltage increases much faster than the output voltage (VOUT LT; VBAT-200 millivolt), the part may be stuck in the short-circuit mode when there is most capacitance loads at the output end. Place a capacitor between the DPPM pin and the ground to slow the rise time of VDPPM during the power -on period and delay short circuit protection. If the output is short -circuited, the capacitance on this pin is too large (excessive delay) may lead to high current. The recommended capacitor is 1 nf to 10 nf. VDPPM rising time is a function of 100-μA DPPM current sources, DPPM resistors and capacitors added.

VREF

VREF is used for internal reference and compensation (3.3 V typical value). In addition, by connecting TMR to the VREF pin, it can be used to disable safe timers and terminals. For internal compensation, the VREF pin requires at least 0.1-μF ceramic capacitors. VREF capacitors should not exceed 1 μF.

Application information

Select input and output capacitors

In most applications, only the input -end high -frequency decoupled capacitance is required. A 0.1-μF ceramic capacitor is placed near the IN-TO-VSS pin, and the effect is very good. In some applications, according to the characteristics of the power supply and the length of the cable, additional 10 μF ceramic capacitors may be needed to add to the input terminal.

BQ24070 only needs a small output capacitor to ensure the stability of the ring. Usually, it is enough to place a 0.1-μF ceramic capacitor between OUT and VSS pins.

It is recommended to install at least 33-μF capacitors between battery pins and VSS (parallel). This ensures that the normal heat is poured power supply in the case of air load (no system load or battery connection).

Thermal factors

BQ24070 packaged in the heat -enhanced MLP packaging. The package includes a QFN 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 provided in the application description of the QFN/SON PCB attachment (SLUA271). The power board should be tied to the VSS aircraft. The most common measurement method of packaging thermal performance is from chip ending to the thermal impedance (θ) of air around the package surface (environment). Youth Achievement Organization

θJa's mathematical expression is:

Among them