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Technical content
500mA USB-Compatible Lithium Ion Battery Charger CN3052A General Description: The CN3052A is a complete constant-current /constant voltage linear charger for single cell Li-ion and Li Polymer rechargeable batteries. The device contains an on-chip power MOSFET and eliminates the need for the external sense resistor and blocking diode. Furthermore, the CN3052A is specifically designed to work within USB power specifications. Its low external component count makes CN3052A ideally suited for portable applications. Thermal feedback regulates the charge current to limit the die temperature during high power operation or high ambient temperature. The regulation voltage is fixed at 4.2V with 1% accuracy. The charge current can be programmed externally with a single resistor. When the input supply (wall adapter or USB supply) is removed, the CN3052A automatically enters a low power sleep mode , dropping the battery drain current to less than 3uA. Other features include undervoltage lockout, automatic recharge, chip enable function, battery temperature sensing and a pin to indicate charge status. The CN3052A is available in a thermally enhanced 8-pin SOP package. Applications: Cellular Telephones Digital Still Cameras MP3 Players Bluetooth Applications Portable Devices USB Bus-Powered Chargers Features: Charges Single Cell Li-Ion Batteries Directly from USB Port or AC Adaptor On-chip Power MOSFET No external Blocking Diode or Current Sense Resistors Required Preset 4.2V Regulation V oltage with 1% Accuracy Precharge Conditioning for Reviving Deeply Discharged Cells and Minimizing Heat Dissipation During Initial Stage of Charge Continuous Programmable Charge Current Up to 500mA Constant-Current/Constant-Voltage Operation with Thermal Regulation to Maximize Charge Rate Without Risk of Overheating Automatic Low-Power Sleep Mode When Input Supply Voltage is Removed Status Indication for LEDs or uP Interface C/10 Charge Termination Automatic Recharge Battery Temperature Sensing Chip Enable Input Available in SOP8 Package Pb-free Available Pin Assignment TEMP CE GND ISET VIN CHRG CN3052A 4 5 BAT FAULT w w w . c o n s o n a n c e - e l e c . c o m R E V 1 . 4 1
Typical Application Circuit VIN CE CHRG FAULT 330 LED BAT CN3052A 4.7uF Bat+ ISET GND TEMP Bat- RISET NT C Input Supply Voltage 4.35V to 6V Battery 330 LED 4.7uF Figure 1 Typical Application Circuit
Ordering Information
Part Number Regulation Voltage Package Operating Ambient Temperature CN3052A 4.2V SOP8 －40℃ to 85℃ w w w . c o n s o n a n c e - e l e c . c o m R E V 1 . 4 2
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Pin No. Name Function Description
1 TEMP
Temperature Sense Input. Connecting TEMP pin to NTC thermistor’s output in Lithium ion battery pack. If TEMP pin’s voltage is below 45% or above 80% of supply voltage VIN for more than 0.15S, this means that battery’s temperature is too high or too low, charging is suspended, and pin is pulled low to indicate a battery fault state. If TEMP’s voltage level is between 45% and 80%of supply voltage for more than 0.15S, battery fault state is released, pin is in high impedance state, and charging will resume. The temperature sense function can be disabled by grounding the TEMP pin.
2 ISET
Constant Charge Current Setting and Charge Current Monitor Pin. The charge current is set by connecting a resistor RISET from this pin to GND. When in precharge mode, the ISET pin’s voltage is regulated to 0.2V. When in constant charge current mode, the ISET pin’s voltage is regulated to 2V.In all modes during charging, the voltage on ISET pin can be used to measure the charge current as follows: I CH = (VISET／RISET)×900 3 GND Ground Terminal.
4 VIN
Positive Input Supply Voltage. VIN is the power supply to the internal circuit. When VIN drops to within 40mv of the BAT pin voltage, CN3052A enters low power sleep mode, dropping BAT pin’s current to less than 3uA.
5 BAT
Battery Connection Pin. Connect the positive terminal of the battery to BAT pin. BAT pin draws less than 3uA current in chip disable mode or in sleep mode. BAT pin provides charge current to the battery and provides regulation voltage of 4.2V. Open-Drain Fault Status Output. When the voltage at TEMP pin is below 45% of VIN or above 80% of VIN, this means that battery’s temperature is too high or too low, is pulled low by an internal switch to indicate a battery fault state; Otherwise pin is in high impedance state. Open Drain Charge Status Output. When the battery is being charged, the pin is pulled low by an internal switch, otherwise pin is in high impedance state. 8 CE Chip Enable Input. A high input will put the device in the normal operating mode. Pulling the CE pin to low level will put the CN3052A into disable mode. The CE pin can be driven by TTL or CMOS logic level. Absolute Maximum Ratings BAT Short-Circuit Duration……Continuous Operating Temperature…... －40℃ to 85 ℃ R E V 1 . 4 4 Stresses beyond those listed under ‘Absolute Maximum Ratings’ may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions above thos e indicated in the operational sections of the specifications is not im plied. Exposure to Absolute Maximum Rating Conditions for extended periods may affect device reliability.
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Electrical Characteristics
(VIN=5V, T A=－40℃ to 85 ℃, Typical Values are measured at TA=25℃,unless otherwise noted) Parameters Symbol Test Conditions M i n T y p M a x U n i t Input Supply Voltage VIN 4.35 6 V CE=VIN, No load at BAT pin 400 650 950Operating Current IVIN Chip disable mode, CE=GND 4 uA Undervoltage Lockout Vuvlo VIN rising 3.95 4.21 V Undervoltage Lockout Hysteresis Huvlo 0.1 V Regulation Voltage VREG CN3052A 4.158 4.2 4.242 V RISET=3.6K,constant current mode, CN3052A 400 500 600 RISET=3.6K, VBAT＝2.3V CN3052A 2 5 5 0 7 5 mA VBAT=VREG, standby mode 1 . 7 5 3 . 5 7 CE=GND, disable mode 3 BAT pin Current IBAT V I N = 0 V , s l e e p m o d e 3 uA Precharge Threshold Precharge Threshold VPRE Voltage at BAT pin rising 2.9 3.0 3.1 V Precharge Threshold Hysteresis HPRE 0.1 V Charge Termination Threshold Charge Termination Threshold Vterm Measure voltage at ISET pin 0.18 0.22 0.26 V Recharge Threshold Recharge Threshold VRECH VREG－0.1 V Sleep Mode Sleep Mode Threshold VSLP VIN from high to low, measures the voltage (VIN－VBAT) 40 mv Sleep mode Release Threshold VSLPR VIN from low to high, measures the voltage (VIN－VBAT) 90 mv ISET Pin Precharge mode 0.2 ISET Pin Voltage VISET Constant current mode 2.0 V TEMP PIN High Input Threshold VHIGH 8 0 8 2 . 5 %VIN Low Input Threshold VLOW 42.5 45 %VIN TEMP input Current TEMP to VIN or to GND 0 . 5 u A CE Pin Logic Input Low VCEL C E v o l t a g e f a l l i n g , C h i p d i s a b l e d 0 . 7 5 V Logic Input High VCEH CE voltage rising, Chip enabled 2.0 V ICEL CE=GND, VIN=6V －1 CE Pin Current ICEH C E = V I N = 6 V 1 uA
Electrical Characteristics(Continued from last page) Parameters Symbol Test Conditions M i n T y p M a x U n i t Pin Pin Sink Current ICHRG V CHRG=0.3V, charge mode 10 mA Leakage Current CE=GND, V CHRG= 6 V 1 u A Pin Pin Sink Current IFAULT V FAULT=0.3V,Fault status 10 mA Pin Leakage Current CE=GND, VFAULT=6V 1 u A Detailed Description The CN3052A is a linear battery charger designed primarily for charging single cell lithium-ion or lithium-polymer batteries. Featuring an internal P-channel power MOSFET, the charger uses a constant-current/constant-voltage to charge the batteries. Continuous charge current can be programmed up to 500mA with an external resistor. No blocking diode or sense resistor is required. The open-drain output and indicates the charger’s status. The internal thermal regulation circuit reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 115℃. This feature protects the CN3052A from excessive temperature, and allows the user to push the limits of the power handling capability of a given circuit board without risk of damaging the CN3052A or the external components. Another benefit of adopting thermal regulation is that charge current can be set according to typical, not worst-case, ambient temperatures for a given application with the assurance that the charger will automatically reduce the current in worst-case conditions. The charge cycle begins when the voltage at the VIN pin rises above the UVLO level, a current set resistor is connected from the ISET pin to ground, and the CE pin is pulled above the chip enable threshold. The pin outputs a logic low to indicate that the charge cycle is ongoing. At the beginning of the charge cycle, if the battery voltage is below 3V, the charger is in precharge mode to bring the cell voltage up to a safe level for charging. The charger goes into the fast charge constant-current mode once the voltage on the BAT pin rises above 3V. In constant current mode, the charge current is set by R ISET. When the battery approaches the regulation voltage, the charge current begins to decrease as the CN3052A enters the constant-voltage mode. When the current drops to charge termination threshold, the charge cycle is terminated, and pin assumes a high impedance state to indicate that the charge cycle is terminated. The charge termination threshold is 10% of the current in constant current mode. To restart the charge cycle, remove the input voltage and reapply it, or momentarily force CE pin to 0V. The charge cycle can also be automatically restarted if the BAT pin voltage falls below the recharge threshold. The on-chip reference voltage, error amplifier and the resistor divider provide regulation voltage with 1% accuracy which can meet the requirement of lithium-ion and lithium polymer batteries. When the input voltage is not present, the charger goes into a sleep mode, dropping battery drain current to less than 3uA. This greatly reduces the current drain on the battery and increases the standby time. The charger can be shutdown by forcing the CE pin to GND. The charging profile is shown in the following figure: R E V 1 . 4 6
4.2V Figure 3 Charging Profile
Application Information
Undervoltage Lockout (UVLO) An internal undervoltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until VIN rises above the undervoltage lockout voltage. The UVLO circuit has a built-in hysteresis of 0.1V. Sleep mode There is an on-chip sleep comparator. The comparator keeps the charger in sleep mode if VIN falls below sleep mode threshold(VBAT+40mv). Once in sleep mode, the charger will not come out of sleep mode until VIN rises 90mv above the battery voltage. Precharge mode At the beginning of a charge cycle, if the battery voltage is below 3V, the charger goes into precharge mode , and the charge current is 10% of fast charge current in constant current mode. Chip Enable/Disable The CN3052A can be disabled by pulling the CE pin to less than 0.75V. For normal operation, pull the CE pin above 2.0V. Applying a voltage between 0.75V to 2.0V to this pin may cause larger operating current, and the CN3052A may be in uncertain state. When the chip is disabled, the internal linear regulator and the power MOSFET are turned off. Programming Charge Current The formula for the battery charge current in constant current mode is: ICH = 1800V / RISET Where: ICH is the charge current in ampere RISET is the total resistance from the ISET pin to ground in ohm For example, if 500mA charge current is required, calculate: R E V 1 . 4 7
RISET = 1800V/0.5A = 3.6kΩ For best stability over temperature and time, 1% metal film resistors are recommended. If the charger is in constant-temperature or constant voltage mode, the charge current can be monitored by measuring the ISET pin voltage, and the charge current is calculated as the following equation: ICH = (VISET / RISET) × 900 USB and Wall Adapter Power Although the CN3052A allows charging from a USB port, a wall adapter can also be used to charge Li-Ion/Li-polymer batteries. Figure 4 shows an example of how to combine wall adapter and USB power inputs. A P-channel MOSFET, M1, is used to prevent back conducting into the USB port when a wall adapter is present and Schottky diode, D1, is used to prevent USB power loss through the 1kΩ pull-down resistor. VIN CN3052A USB Power Wall Adapter Figure 4 Combining Wall Adapter and USB Power Battery Temperature Sense To prevent the damage caused by the very high or very low temperature done to the battery pack, the CN3052A continuously senses battery pack te mperature by measuring the voltage at TEMP pin determined by the voltage divider circuit and the battery’s internal NTC thermistor as shown in Figure 1. The CN3052A compares the voltage at TEMP pin (V TEMP) against its internal V LOW and V HIGH thresholds to determine if charging is allowed. In CN3052A, V LOW is fixed at (45% ×VIN), while VHIGH is fixed at (80% × VIN). If VTEMP<VLOW or V TEMP>VHIGH for 0.15 seconds, it indicates that the battery temperature is too high or too low and the charge cy cle is suspended. When V TEMP is between V LOW and V HIGH for more than 0.15 seconds, the charge cycle resumes. The battery temperature sense function can be disabled by connecting TEMP pin to GND. Selecting R1 and R2 The values of R1 and R2 in the application circuit can be determined according to the assumed temperature monitor range and thermistor’s values. The Follows is an example: Assume temperature monitor range is T L ～TH (T L ＜TH ＝; the thermistor in battery has negative temperature coefficient (NTC), R TL is thermistor’s resistance at TL, RTH is the resistance at T H, so RTL＞RTH, then at temperature TL, the voltage at TEMP pin is: At temperature TH, the voltage at TEMP pin is: R E V 1 . 4 8
We know, VTEMPL＝VHIGH＝k2×VIN (k2=0.8) VTEMPH＝VLOW＝k1×VIN (k1=0.45) Then we can have: R1＝ 2 1 THTL 1 2 TH TL k )k R (R ) k (k R R R2＝ ) k k (k R ) k k (k R ) k (k R R 2 1 2 TH2 1 1 TL 1 2 TH TL Likewise, for positive temperature coefficient thermistor in battery, we have R TH＞RTL and we can calculate: R1＝ 2 1 TLTH 1 2 TH TL k )k R (R ) k (k R R R2＝ ) k k (k R ) k k (k R ) k (k R R 2 1 2 TL 2 1 1 TH 1 2 TH TL We can conclude that temperature monitor range is independent of power supply voltage VIN and it only depends on R1, R2, R TL and R TH: The values of R TH and R TLcan be found in related battery handbook or deduced from testing data. In actual application, if only one terminal temperature is concerned(normally protecting overheating), there is no need to use R2 but R1. It becomes very simple to calculate R1 in this case. Recharge After a charge cycle has terminated, if the battery voltage drops below the recharge threshold of 4.1V, a new charge cycle will begin automatically. Constant-Current/Constant-Voltage/Constant-Temperature The CN3052A use a unique architecture to charge a battery in a constant-current, constant-voltage, constant temperature fashion as shown in Figure 2. Amplifiers Iamp, Vamp, and Tamp are used in three separate feedback loops to force the charger into constant-current, constant-voltage, or constant-temperature mode, respectively. In constant current mode the charge current delivered to the battery equal to 1800V/RISET. If the power dissipation of the CN3052A results in the junction temperature approaching 115℃, the amplifier Tamp will begin decreasing the charge current to limit the die temperature to approximately 115℃. As the battery voltage rises, the CN3052A either returns to constant-current mode or it enters constant voltage mode straight from constant-temperature mode. Open-Drain Status Outputs The CN3052A have 2 open-drain status outputs: and is pulled low when the charger is in charging status, otherwise becomes high impedance. is pulled low if battery pack’s temperature is in out of temperature condition for more than 0.15S, otherwise becomes high impedance. When the battery is not present, the charger charges the output capacitor to the regulation voltage quickly, then the BAT pin’s voltage decays slowly to recharge threshold because of low leakage current at BAT pin, which results in a 100mv ripple waveform at BAT pin, in the meantime, pin outputs a pulse to indicate that the battery’s absence. The pulse’s frequency is around 10Hz when a 4.7uF output capacitor is used. The open drain status output that is not used should be tied to ground. VIN Bypass Capacitor CIN Many types of capacitors can be used for input bypassing, CIN is typically a 4.7uF capacitor. R E V 1 . 4 9
For the consideration of the bypass capacitor, please refer to the Application Note AN102 from our website. Stability Typically a 4.7uF capacitor from BAT pin to GND is required to stabilize the feedback loop. In constant current mode, the stability is also affected by the impedance at the ISET pin . With no additional capacitance on the ISET pin, the loop is stable with current set resistors values as high as 50KΩ. However, additional capacitance on ISET pin reduces the maximum allowed current set resistor. The pole frequency at ISET pin should be kept above 200KHz. Therefore, if ISET pin is loaded with a capacitance C, the following equation should be used to calculate the maximum resistance value for RISET: In order to measure average charge current or isolate capacitive load from ISET pin, a simple RC filter can be used on ISET pin as shown in Figure 5. CN3052A ISET RISET 10K Cfilter Figure 5 Isolating Capacitive Load on ISET Pin Board Layout Considerations 1. RISET at ISET pin should be as close to CN3052A as possible, also the parasitic capacitance at ISET pin should be kept as small as possible. 2. The capacitance at VIN pin and BAT pin should be as close to CN3052A as possible. 3. During charging, CN3052A’s temperature may be high, the NTC thermistor should be placed far enough to CN3052A so that the thermistor can reflect the battery’s temperature correctly. 4. It is very important to use a good thermal PC board layout to maximize charging current. The thermal path for the heat generated by the IC is from the die to the copper lead frame through the package lead(especially the ground lead) to the PC board copper, the PC board copper is the heat sink. The footprint copper pads should be as wide as possible and expand out to larger copper areas to spread and dissipate the heat to the surrounding ambient. Feedthrough vias to inner or backside copper layers are also useful in improving the overall thermal performance of the charger. Other heat sources on the board, not related to the charger, must also be considered when designing a PC board la yout because they will affect overall temperature rise and the maximum charge current. The ability to deliver maximum charge current under all conditions require that the exposed metal pad on the back side of the CN3052A package be soldered to the PC board ground. Failure to make the thermal contact between the exposed pad on the backside of the package and the copper board will result in larger thermal resistance. R E V 1 . 4 1 0
Package Information
Consonance does not assume any responsibility for use of any circuitry described. Consonance reserves the right to change the circuitry and specifications without notice at any time. R E V 1 . 4 1 1