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2022-09-15 14:32:14
L6924D battery charger system Lithium ion/lithium polymer power switch (1)
Features
Full integrated solution
MOSFET, reverse blocking diode, induction resistance, heat protection
ideal choice of coke and graphite anode single battery [123 ]
Lithium-ion bagLinear and quasi-pulse operation
closed-loop heat control
USB bus compatibility
The programmable charging current is as high as 1A [ 123]
Programmable pre -charging current
The ending current of programmable charging
The programmable pre -charging voltage threshold
A programmable charging timer
4.1V's programmable output voltage
4.2V, the output voltage accuracy is ± 1%
(NTC) or (PTC) battery thermist resistance interface
temperature monitoring And protection
The flexible charging process terminates
Drives the status output of LED or interface
Use the host processor
Small VFQFPN 16 Digestive Package (3mm x3 Mm)
Application
pda
Handheld device
MobileDigital camera
Independent charger
]
USB power supply chargerDevice description
L6924D is a full single -piece battery charger, which is dedicated to single battery lithium ion/polymer battery pack. It is an ideal solution for space limited applications, such as PDA, handheld devices, mobile phones and digital cameras. It uses BCD6 technology design, integrating power components (power MOSFET, reverse blocking diode and sensing resistance) small VFQFPN16 3mm x 3mm packaging. When the external voltage adjustment wall -mounted adapter is used, L6924D works in a linear mode, and is used as a battery charging/constant voltage (CC/CV) curve with constant current. In addition, when using a restricted adapter, the device can work in the quasi -pulse mode to significantly reduce power consumption. Regardless of charging, closed -loop heat control to avoid overheating equipment. The equipment has a working input voltage from 2.5V to 12V. L6924D allows users to program parameter thresholds such as pre -charging current, fast charging current, and pre -charging voltage, charging end current threshold and charging timer. L6924D provides two open formulas for the output for diagnostic destinations, which can be used to drive two external LEDs or communicate with the host microcontroller. Finally, L6924D also provides a very flexible control of the terminal and gas meter capacity of the charging process, as well as other functions, such as checking whether the battery exists, andControl and protect the battery's influence on the heat conditions.
maximum rated value
In the ""absolute maximum rated value"" table, the equipment stress Causes permanent damage to the device. These are only stress levels and the devices under the above conditions or any other conditions are not implicit. Long -term exposure to absolute maximum rated conditions may affect the reliability of the device next cycle. Please refer to the StMicroelectronics Sure program and other related quality files.
1 The device installed on the demonstration board
electrical characteristicstj u003d 25 ° C, vin u003d 5V, unless there is another other Regulations
Table 5. Electrical characteristics
Operation description
L6924D is a fully integrated battery charger, allowing very compact battery space Limited application management system. It integrates in a small package, all power components: power MOSFET, reverse blocking diode and sensitive resistance. When power supply from the external voltage adjustment adapter, it usually works as a linear charger. However, due to its very low minimum input voltage (as low as 2.5V), L6924D can also work as a quasi -pulse charger when the current -limited adapter is powered. The working conditions here are enough to set the charging current of the device than the charging current of the adapter (Chapter 19, Chapter 7.4). The advantage of the linear charging method is that the device has a direct control of the charging current, so designers do not need to rely on upstream adapters. However, the advantage of the quasi -pulse method is that the portable portable equipment that disperse internal power is greatly reduced. For the charging method, L6924D is charged to the battery in three stages:
Pre -charging Hengli: At this stage (when the battery power is deepened, the discharge is activated) The battery is charged at low current.Quick charging constant current: At this stage, the maximum current of the device is used.
Constant voltage: When the battery voltage is close to the selected output voltage, the device starts to reduce the current until the charging ends. Flexibility is:
programmable pre -charged current and voltage threshold (ipreth and VPRETH) (p. 7.2, Chapter 19, Chapter 7.3).
Programmable fast charging current (ICHG) (chapter 7.4).
Programmable charging ending current threshold (INDTH) (Chapter 20, Chapter 7.5).
The programmable charging ending timer (Tmaxh) (Chapter 22, Chapter 7.8).
If you don't need to finishFull flexibility, and the first choice of less external components, the default values u200bu200bof iPreth and VPRETH are available to keep their feet floating.
If a PTC or NTC resistor is used, the device can monitor the battery temperature in order to prevent the battery from working in an unsafe heat environment.
In addition to the low thermal resistance of the packaging, the built -in temperature control circuit provides additional safety. The knot temperature of the IC monitor continues. When the temperature reaches about 120 ° C, the thermal control circuit starts to work, and the charging current is reduced in turn to keep the IC knot temperature at 120 ° C.
Two epigrium opening outputs can be used to diagnose destinations (status pin ST1 and ST2). They can also use to drive external LEDs or interfaces with microcontroller.
The voltage on the resistor connected between IND and GND provides the following information actual charging current (as a gas meter), which can easily enter a μCADC. 当VPRE引脚不用于编程预充电电压阈值时,它有两个不同功能:如果VPRE引脚上的电压低于0.8V,当I lt;IENDTH时, The charging is notified by the status PIN, but the charging process is not disabled. The charging process ends when the maximum charging time expires.
If the pins VPRE is lower than 0.5V, the timer is reset at the decrease of the decrease. Due to differentiated induction and mandatory output, the battery is disconnected and controlled. A small water sinking sinks and forced it to pass. If VOSNS does not detect the battery IC entering the standby mode. Figure 5 shows the actual charging curve of the lithium ion battery, the fast charging current is 450 mAh (RPRG u003d 26K ),
Linear mode
] When running in a linear mode, the working method of the device is similar to the constant current restriction protection of a linear regulator. It charges the battery in three stages:
Pre -charging current (""Pre -charging"" stage).
Hengliu (""fast charging"" stage).
voltage (""constant voltage"" adjustment).
VADP is the output voltage of the upstream AC-DC adapter, which is L6924D. If the battery voltage is lower than the set pre -charging voltage (VPRETH), the pre -charging phase will occur. Use a low -current IPRE to pre -charged the battery (Chapter 7.2, p. 18). When the battery voltage is higher than the VPRETH, the battery will be used for the charging current ICHG by fast charging, and the external resistor is set (Chapter 19, Chapter 7.4). Finally, when the battery voltage is close to the adjustment output voltage VOPRGTH (4.1V or 4.2V), the voltage adjustment phase occurs, and the charging current is reduced. This charging processThe charging current reaches the set value or the charging timer expires (Chapter 23, Chapter 7.9). Figure 6 shows different stages
When the device starts quickly charging, the worst situation of power consumption appears. In fact, the battery voltage at its minimum value. In this case, this is the biggest difference between the adapter voltage and the battery voltage, and the charging current reaches the maximum value values. The dispersion power is concluded by the following formulas:
The higher the voltage of the adapter, the higher the power consumption. The maximum power disperse depends on the heat impedance of the device installed on the ship.
Metal pulse mode
When the system can depend on current limit, the quasi -pulse mode can be used as a battery charging upstream adapter. In this case, ICHG must be set to restrictions above the current appropriate accessories. In this mode, the L6924D uses the same three -phase battery charging and linear mode, but the power consumption is greatly reduced, as shown in Figure 7.
The biggest difference is because ICHG is higher than the current limit of the adapter. During the fast charging phase, the output voltage of the adapter dropped and dropped to the battery voltage plus the voltage drop on the charger power MOSFET, as shown in the following formula:
Ilim u003d Ilim u003d The current limit of the wall adapter, the resistance of the RDS (on) u003d power MOSFET. The difference between the setting of the charging current and the adapter restrictions should be large enough to minimize the RDS (on) value (on) value (on power consumption). This makes the control circuit completely unbalanced, and the power component is completely connected. Figure 8 shows that the RDS (ON) value of different output voltage and charging current is limited to 500mA.
When the device runs in this mode, ignore the voltage reduction on the charger ( #8710; vmos), its input voltage is equal to the input voltage of the battery , So the work input voltage is very low (as low as 2.5V). The power consumption of the device at this stage is:
When the battery voltage is close to the final value, the charger re -control the current and reduce the current. Therefore, the upstream adapter exits the current restrictions and its output rises to the adjustment voltage VADP. This is the worst situation of power consumption:
In short, the advantage of the linear charging method is that the designer has a control charging current, so the application is very simple. This disadvantage is high power consumption. The advantage of the quasi -pulse charging method is that the power consumption is greatly reduced. The disadvantage is that a dedicated upstream adapter is required.
Application information: Charging process
Pharmaceutical process flow drawing
Pre -chargingCurrent
L6924D allows the battery voltage to be lower than the specified threshold (VPRETH).The default value of the pre -charging current is equal to 10%of the fast charging current (see Chapter 18.2: Pre -charging current).It can be adjusted by connecting a resistor from the IPRE pin to the GND or VREF Figure 10, no matter what.When the resistor is connected from the IPRE pin and GND, the current is higher than the default value.This RPRE value is given by the following formulas:
When the RPRE is connected to VREF, the current is lower than the default value.VREF is an external reference equal to 1.8V, VBG is internal reference equal to 1.23V, and KPRE is a constant equal to 950.Figure 11 The relationship is shown in the equation: