Lm3622 lithium-ion battery charger controller

Lithium-Ion
LM3622
Lithium-Ion Battery Charger Controller
General Description
low-voltage battery threshold circuitry that removes this drivewhen the cell voltage drops below a preset limit. The LVSEL The LM3622 is a charge controller for Lithium-Ion batteries.
pin programs this threshold voltage to either 2.7V/cell or This monolithic integrated circuit accurately controls an ex- 2.15V/cell. The low-voltage detection, which is a user en- ternal pass transistor for precision Lithium-Ion battery charg- abled feature, provides an output signal that can be used to ing. The LM3622 provides a constant voltage or constant enable a "wake up charge" source automatically to precon- current (CVCC) configuration that changes, as necessary, to optimally charge lithium-ion battery cells. Voltage charging The LM3622 is available in a standard 8-lead SOIC surface versions (4.1V, 4.2V, 8.2V, and 8.4V) are available for one or two cell battery packs and for coke or graphite anode battery Features
The LM3622 accepts input voltages from 4.5V to 24V. Con-troller accuracy over temperature is ±30mV/cell for A grade n Versions for charging of 1 cell (4.1V or 4.2V) or 2 cells and ±50mV/cell for the standard grade. No precision exter- nal resistors are required. Furthermore, the LM3622’s pro- prietary output voltage sensing circuit drains less than n Precision (±30mV/cell) end-of-charge control Controller
200nA from the battery when the input source is discon- The LM3622 circuitry includes functions for regulating the charge voltage with a temperature compensated bandgapreference and regulating the current with an external sense Applications
resistor. The internal bandgap insures excellent controllerperformance over the operating temperature and input sup- The LM3622 can sink 15mA minimum at the EXT pin to drive the base of an external PNP pass transistor. It also has Typical Application
2004 National Semiconductor Corporation Connection Diagram
8-Lead Surface Mount Package
Refer to the Ordering Information Table in this Datasheet for Specific Part Number
See NS Package M08A
Pin Description
Description
Low-voltage detection threshold Select. The threshold is 2.15V/cell when this pin is pulled low to GND and 2.70V/cell when it is pulled up to V Low-voltage detection Enable. The low-voltage detection is enabled when this pin is pulled Low to GND. Pulling this pin HIGH to V Output of the low-voltage detection. This pin is a NPN open-collector output that goes is pulled LOW and the battery voltage is below . LV stays in HIGH impedance state at any battery voltage . LV can be used for turning on a low current source to recondition a deeply depleted battery.
Input for battery charge current and battery negative-terminal voltage sensing. Battery charging current is sensed through an external resistor, R battery’s negative terminal and GND. The maximum charge current is regulated to a Battery positive-terminal voltage sensing.
Output of the controller for driving a PNP transistor or P-MOSFET. The controller modulates the current sinking into this pin to control the regulation of either the charge Ordering Information
Accuracy
Order Information
Supplied As
Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Operating Ratings
Electrical Characteristics
LM3622-XX
= 5V/Cell T =T = 25˚C. Limits with standard typeface apply for T = 25˚C, and limits in bold-
face type apply over the indicated temperature range.
Parameter
Conditions
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: VEXT is not allowed to exceed (VCC+ 0.3V) or damage to the device may occur.
Note 3: Rating is for the human body model, a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin.
Note 4: The maximum power dissipation must be de-rated at elevated temperatures and is limited by TJMAX (maximum junction temperature), θJA (junction-to-
ambient thermal resistance) and TA (ambient temperature). The maximum power dissipation at any temperature is: PDissMAX = (TJMAX − TA) / θJA up to the value
listed in the Absolute Maximum Ratings.
Note 5: Limits reflect initial accuracy.
Electrical Characteristics (Continued)
Note 6: TJ = 85˚C, 1000 hours. Activation energy of 0.78eV used.
Typical Performance Characteristics
Unless otherwise specified, T = 25˚C.
Output Voltage Regulation
Current Sense Voltage Regulation
Current Sense Voltage Regulation
Vs Temperature
Output Drive Current Vs V
Output Drive Current Vs V
Quiescent Current Vs V
Functional Description
FIGURE 1. LM3622 Simplified Block Diagram
The simplified LM3622 block diagram in gives a the power down switch will disconnect the resistor divider general idea of the circuit operation. The controller integrates from the CS pin, preventing the battery from discharging the reference, feedback and drive functions on-chip to con- trol a linear, lithium-ion battery charger in constant voltageand constant current (CVCC) charge operation. The regu- lated output voltage is sensed between CEL and CS, and the battery charge current is sensed across a current-sense source making it possible to eliminate the external base- resistor between CS and GND. The EXT pin is designed for emitter resistor when driving a PNP transistor, or the gate- driving a series pass element, which can be a PNP transistor source resistor when driving a P-MOSFET. However, the voltage applied to EXT is not allowed to be higher than (VCC pin to ground enables the controller’s low- + 0.3V), otherwise the reverse current from EXT pin to V voltage detection circuit. When the low-voltage detection circuit is enabled and a battery voltage below a presetthreshold is detected, the LM3622 will drive the LV pin low LV PIN CURRENT RATING
and shut off the current flowing into the EXT pin to suspend The LV pin is a low power, NPN open collector output that is the CVCC charge process. The low-voltage threshold is user rated to sink 10mA maximum. Therefore, the value of the pull selectable to be either 2.15V/cell or 2.7V/cell by pulling the up resistor should be chosen high enough to limit the current open collector output that can be used to turn on a lowcurrent source to wake up charge a deeply depleted battery.
When the low-voltage detection is disabled (LV In normal operation, the current limit threshold voltage for ), the LM3622 always starts the charge cycle in con- the CS pin is 100mV typical. In case of a fault condition, the stant current mode at any battery voltage below the control- voltage to this pin should be limited to below 5V.
ler’s regulation level, and maintains the LV pin at a high-impedance state.
Application Information
CEL PIN CURRENT DRAIN
The LM3622 has an internal power down switch in serieswith the on-chip resistor divider that is used for sensing thebattery voltage. In the event that the V Typical Application
FIGURE 2. Low Dropout, Constant Current/Constant Voltage Li-ion Battery Charger
The low dropout linear charger shown in provides LM3622 turns Q2 off and forces the LV pin low to drive Q1 on constant current and constant voltage charging of 1-cell to start a wake up charge phase. Q1 in conjunction with R2 lithium-ion battery packs. J1 and J2 are used for selecting provides a low current source to recondition the battery.
the operation of the low-voltage detection. The LM3622 ini- During the wake up charge mode, Q1 is driven into satura- tializes the charge cycle based on the battery voltage and tion and the wake up charge current is programmed by R2, the enable status of the low-voltage detection.
When the low-voltage detection is disabled, the LM3622 starts the charge cycle constant current mode if the battery emitter on state voltage of Q1, V 1 is the diode forward voltage is below the controller’s regulation level. In constant voltage of D1, and LVth is the low-voltage threshold level set current mode, the LM3622 modulates the base drive of Q2 to regulate a constant 100mV across the current sense resistor Once the battery voltage reaches the low-voltage threshold, the LV pin transitions to a high-impedance state to end the wake up charge phase, and the EXT pin resumes the base which is equal to 0.5A in this case.
drive of Q2 to start the constant current mode. The charging Once the battery voltage reaches the target regulation level cycle is completed in constant voltage mode when the bat- set by the LM3622, Q2 is controlled to regulate the voltage tery is fully charged. shows the timing diagram of across the battery, and the constant voltage mode of the the charge cycle with the low-voltage detection enabled.
charging cycle starts. Once the charger is in the constant D1 is a general-purpose silicon diode used for isolating the voltage mode, the charger maintains a regulated voltage battery from the charger circuitry that could discharge the across the battery and the charging current is dependent on battery when the input source is removed. Changing D1 to a the state of the charge of the battery. As the cell approaches Schottky diode will reduce the overall dropout voltage of the a fully charged condition, the charge current falls to a very circuit, but the penalty is higher leakage current associated When the low-voltage detection is enabled and the initialbattery voltage is below the low-voltage threshold, the Timing Diagram
FIGURE 3. Typical Charge Cycle with Low-Voltage Detection Enabled.
Physical Dimensions inches (millimeters) unless otherwise noted
Lithium-Ion
Controller
SOIC-8 Package
8-Lead Small-Outline Package (M8)
For Ordering, Refer to Ordering Information Table
NS Package Number M08A
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reservesthe right at any time without notice to change said circuitry and specifications.
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Source: http://skory.gylcomp.hu/alkatresz/LM3622_Li-tolto.pdf