MIC79050 Micrel MIC79050 Simple Lithium-Ion Battery Charger Preliminary Information General Description Features The MIC79050 is a simple single-cell lithium-ion battery charger. It includes an on-chip pass transistor for high precision charging. Featuring ultrahigh precision (+0.75% over the Li-ion battery charging temperature range) and "zero" off mode current, the MIC79050 provides a very simple, cost effective solution for charging lithium-ion battery. * High accuracy charge voltage: 0.75% over -5C to + 60C (Li-ion charging temperature range) * "Zero" off-mode current * 10A reverse leakage * Ultralow 380mV dropout at 500mA * Wide input voltage range * Logic controlled enable input (8-pin devices only) * Thermal shutdown and current limit protection * Power MSOP-8, Power SOP-8, and SOT-223 * Pulse charging capability Other features of the MIC79050 include current limit and thermal shutdown protection. In the event the input voltage to the charger is disconnected, the MIC79050 also provides minimal reverse-current and reversed-battery protection. The MIC79050 is a fixed 4.2V device and comes in the thermally-enhanced MSO-8, SO-8, and SOT-223 packages. The 8-pin versions also come equipped with enable and feedback inputs. All versions are specified over the temperature range of -40C to +125C. Applications * * * * * Li-ion battery charger Celluar phones Palmtop computers PDAs Self charging battery packs Ordering Information Part Number Voltage Junct. Temp. Range Package MIC79050-4.2BS 4.2V -40C to +125C SOT-223 MIC79050-4.2BM 4.2V -40C to +125C SOP-8 MIC79050-4.2BMM 4.2V -40C to +125C MSOP-8 Typical Applications Regulated or unregulated wall adapter MIC79050-4.2BS IN BAT 4.2V 0.75% Over Temp Li-Ion Cell GND Simplest Battery Charging Solution Regulated or unregulated wall adapter MIC79050-4.2BMM IN BAT EN FB GND 4.2V 0.75% Li-Ion Cell External PWM* *See Applications Information Pulse-Charging Application Micrel, Inc. * 1849 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 944-0970 * http://www.micrel.com September 2001 1 MIC79050 MIC79050 Micrel Pin Configuration GND TAB 1 2 3 IN GND BAT MIC79050-x.xBS SOT-223 EN 1 8 GND IN 2 7 GND 3 6 GND FB 4 5 GND BAT MIC79050-x.xBM SOP-8 and MSOP-8 Pin Description Pin No. SOT-223 Pin No. SOP-8 MSOP-8 Pin Name Pin Function 1 2 IN Supply Input 2, TAB 5-8 GND Ground: SOT-223 pin 2 and TAB are internally connected. SO-8 pins 5 through 8 are internally connected. 3 3 BAT Battery Voltage Output 1 EN Enable (Input): TTL/CMOS compatible control input. Logic high = enable; logic low or open = shutdown. 4 FB Feedback Node MIC79050 2 September 2001 MIC79050 Micrel Absolute Maximum Ratings (Note 1) Operating Ratings (Note 2) Supply Input Voltage (VIN) ............................ -20V to +20V Power Dissipation (PD) ............... Internally Limited, Note 3 Junction Temperature (TJ) ....................... -40C to +125C Lead Temperature (soldering, 5 sec.) ....................... 260C Storage Temperature (TS) ....................... -65C to +150C Supply Input Voltage (VIN) ........................... +2.5V to +16V Enable Input Voltage (VEN) .................................. 0V to VIN Junction Temperature (TJ) ....................... -40C to +125C Package Thermal Resistance (Note 3) ............................... MSOP-8 (JA) ...................................................... 80C/W SOP-8(JA) .......................................................... 63C/W SOT-223(JC) ...................................................... 15C/W Electrical Characteristics VIN = VBAT + 1.0V; COUT = 4.7F, IOUT = 100A; TJ = 25C, bold values indicate -40C TJ +125C; unless noted. Symbol Parameter Conditions VBAT Battery Voltage Accuracy variation from nominal VOUT -5C to +60C VBAT/T Battery Voltage Temperature Coefficient Note 4 VBAT/VBAT Line Regulation VIN = VBAT + 1V to 16V 0.009 0.05 0.1 %/V %/V VBAT/VBAT Load Regulation IOUT = 100A to 500mA, Note 5 0.05 0.5 0.7 % % VIN - VBAT Dropout Voltage, Note 6 IOUT = 500mA 380 500 600 mV mV IGND Ground Pin Current, Notes 7, 8 VEN 3.0V, IOUT = 100A 85 130 170 A A VEN 3.0V, IOUT = 500mA 11 20 25 mA mA VEN 0.4V (shutdown) 0.05 3 A VEN 0.18V (shutdown) 0.10 8 A IGND Ground Pin Quiescent Current, Note 8 Min Typical -0.75 Max Units +0.75 % 40 PSRR Ripple Rejection f = 120Hz 75 ILIMIT Current Limit VBAT = 0V 750 VBAT/PD Thermal Regulation Note 9 0.05 VEN = logic low (shutdown) 0.4 ppm/C dB 900 1000 mA mA %/W ENABLE Input VENL Enable Input Logic-Low Voltage 0.18 VEN = logic high (enabled) IENL Enable Input Current 2.0 V VENL 0.4V (shutdown) 0.01 -1 A VENL 0.18V (shutdown) 0.01 -2 A 5 20 25 A A VENH 2.0V (enabled) IENH V V Note 1. Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. The maximum allowable power dissipation at any TA (ambient temperature) is calculated using: PD(max) = (TJ(max) - TA) / JA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. Note 4. Battery voltage temperature coefficient is the worst case voltage change divided by the total temperature range. Note 5. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load range from 100A to 500mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification. Note 6. Dropout voltage is defined as the input to battery output differential at which the battery voltage drops 2% below its nominal value measured at 1V differential. Note 7: Ground pin current is the charger quiescent current plus pass transistor base current. The total current drawn from the supply is the sum of the load current plus the ground pin current. Note 8: VEN is the voltage externally applied to devices with the EN (enable) input pin. [MSO-8(MM) and SO-8 (M) packages only.] Note 9: Thermal regulation is the change in battery voltage at a time "t" after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 500mA load pulse at VIN = 16V for t = 10ms. September 2001 3 MIC79050 MIC79050 Micrel Typical Characteristics Dropout Voltage vs. Output Current Dropout Voltage vs. Temperature 200 100 500 400 300 200 100 0 -40 100 200 300 400 500 OUTPUT CURRENT (mA) 500mA 2 1 2 4 INPUT VOLTAGE (V) 6 4 2 250mA 125mA 100 50 0 -40 6 Ground Current vs. Temperature OUTPUT VOLTAGE (V) GROUND CURRENT (mA) 12.5 12.0 11.5 MIC79050 0 40 80 TEMPERATURE (C) 0 40 80 TEMPERATURE (C) 120 16 3.6 3.4 3.2 3.0 -40 120 4.210 13.0 4 8 12 SUPPLY VOLTAGE (V) 3.8 Battery Voltage vs. Temperature 13.5 11.0 -40 0.5 4.0 4.205 4.200 4.195 4.190 -40 -20 0 20 40 60 80 100120140 TEMPERATURE (C) 4 0 40 80 TEMPERATURE (C) 120 Short Circuit Current vs. Temperature SHORT CIRCUIT CURRENT (mA) 1 2 3 4 5 SUPPLY VOLTAGE (V) 5mA Ground Current vs. Temperature GROUND CURRENT (mA) GROUND CURRENT (uA) GROUND CURRENT (mA) 0 0 50mA 0 0 100 200 300 400 500 OUTPUT CURRENT (mA) 150 500mA 5mA 50mA, 150mA 2 4 6 8 10 12 14 16 INPUT VOLTAGE (V) 1 Ground Current vs. Temperature 15 5 1 1.5 8 0 0 6 25 10 2 Ground Current vs. Supply Voltage 10 Ground Current vs. Supply Voltage 20 120 GROUND CURRENT (mA) GROUND CURRENT (mA) OUTPUT VOLTAGE (V) 250mA 3 3 0 0 12 5 0 0 0 40 80 TEMPERATURE (C) 4 Output Current vs. Ground Dropout Characteristics 4 5 OUTPUT VOLTAGE (V) 300 0 0 Dropout Characteristics 600 DROPOUT VOLTAGE (mV) DROPOUT VOLTAGE (mV) 400 800 700 600 500 400 300 200 100 0 -40 0 40 80 TEMPERATURE (C) 120 September 2001 0.25 Upper Lower -0.25 -0.75 0 200 400 600 TIME (hrs) 800 September 2001 Reverse Leakage Current vs. Output Voltage 20 15 10 5 0 0 1 2 3 4 OUTPUT VOLTAGE (V) 5 REVERSE LEAKAGE CURRENT (A) Typical Voltage Drift Limits vs. Time 0.75 REVERSE LEAKAGE CURRENT (A) Micrel REVERSE LEAKAGE CURRENT (uA) DRIFT FROM NOMINAL VOUT (%) MIC79050 Reverse Leakage Current vs. Output Voltage 20 4.2V 15 3.6V 10 3.0V 5 0 -5 VIN+VEN FLOATING 5 15 25 35 45 55 TEMPERATURE (C) Reverse Leakage Current vs. Temperature 20 4.2V 15 3.6V 10 3.0V 5 VIN+VEN 0 -5 GROUNDED 5 15 25 35 45 TEMPERATURE (C) 5 55 MIC79050 MIC79050 Micrel Block Diagrams VIN VBAT IN VIN VBAT IN FB Bandgap Ref. Bandgap Ref. V REF Current Limit Thermal Shutdown EN MIC79050-x.xBS Current Limit Thermal Shutdown GND MIC79050-x.xBMM/M GND 3-Pin Version 5-Pin Version drawn by the battery has approached a minimum and/or the maximum charging time has timed out. When disabled, the regulator output sinks a minimum of current with the battery voltage applied directly onto the output. This current is typically 12A or less. Feedback The feedback pin allows for external manipulation of the control loop. This node is connected to an external resistive divider network, which is connected to the internal error amplifier. This amplifier compares the voltage at the feedback pin to an internal voltage reference. The loop then corrects for changes in load current or input voltage by monitoring the output voltage and linearly controlling the drive to the large, PNP pass element. By externally controlling the voltage at the feedback pin the output can be disabled or forced to the input voltage. Pulling and holding the feedback pin low forces the output low. Holding the feedback pin high forces the pass element into saturation, where the output will be the input minus the saturation (dropout) voltage. Functional Description The MIC79050 is a high-accuracy, linear battery charging circuit designed for the simplest implementation of a single lithium-ion (Li-ion) battery charger. The part can operate from a regulated or unregulated power source, making it ideal for various applications. The MIC79050 can take an unregulated voltage source and provide an extremely accurate termination voltage. The output voltage varies only 0.75% from nominal over the standard temperature range for Li-ion battery charging (-5C to 60C). With a minimum of external components, an accurate constant current charger can be designed to provide constant current, constant voltage charging for Li-ion cells. Input Voltage The MIC79050 can operate with an input voltage up to 16V (20V absolute maximum), ideal for applications where the input voltage can float high, such as an unregulated wall adapter that obeys a load-line. Higher voltages can be sustained without any performance degradation to the output voltage. The line regulation of the device is typically 0.009%/V; that is, a 10V change on the input voltage corresponds to a 0.09% change in output voltage. Enable Battery Output The BAT pin is the output of the MIC79050 and connects directly to the cell to provide charging current and voltage. When the input is left floating or grounded, the BAT pin limits reverse current to <12A to minimize battery drain. The MIC79050 has an enable pin that allows the charger to be disabled when the battery is fully charged and the current MIC79050 6 September 2001 MIC79050 Micrel correctly e.g. For a 500mAhr battery, the output of the semiregulated supply should be between 225mA to 500mA ( 0.5C to 1C ). If it is below 225mA no damage will occur but the battery will take longer to charge. Figure 1B shows a typical wall adapter characteristic with an output current of 350mA at 4.5V. This natural impedance of the wall adapter will limit the max current into the battery, so no external circuitry is needed to accomplish this. If extra impedance is needed to achieve the desired loadline, extra resistance can easily be added in series with the MIC79050 IN pin. Applications Information Simple Lithium-Ion Battery Charger. Figure 1A shows a simple, complete lithium-ion battery charger. The charging circuit comprises of a cheap wall adapter, with a load-line characteristic. This characteristic is always present with cheap adapters due to the internal impedance of the transformer windings. The load-line of the unregulated output should be < 4.4V to 4.6V at somewhere between 0.5C to 1C of the battery under charge. This 4.4 to 4.6V value is an approximate number based on the headroom needed above 4.2V for the MIC79050 to operate Impedence VS MIC79050-4.2BM IN BAT EN FB GND 10k 1k MIC6270 AC Load-line Wall Adapter End of Charge R1 VEOC = VREF 1 + R2 R1 4.7F R2 LM4041 CIM3-1.2 VREF = 1.225V Figure 1A. Load-Line Charger With End-Of-Charge Termination Circuit. Load-Line Source Characteristics SOURCE VOLTAGE (V) 8 6 4 2 0 0 0.2 0.4 0.6 SOURCE CURRENT (A) 0.8 Figure 1B. Load-Line Characteristics of AC Wall Adapter September 2001 7 MIC79050 MIC79050 Micrel End of Charge (VEOC) Open Circuit Charger Voltage VEOC Unregulated Input Voltage(VB) 79050 Programmed Output Voltage (No Load Voltage) Battery Voltage (VB) Battery Current (IB) State A State B State C State D Initial Charge Voltage Charge End of Charge Charge Top State C Figure 1C. Charging Cycles The Charging Cycle (See Figure 1C.) input voltage has reached such a level so the current in the battery is low, indicating full charge. 3. State C: End of charge cycle. When the input voltage, VS reaches VEOC, an end of charge signal is indicated. 4. State D: Top up charge. As soon as enough current is drawn out of the input source, which pulls the voltage lower than the VEOC, the end of charge flag will be pulled low and charging will initiate. Variations on this scheme can be implemented, such as the circuit shown in Figure 2. For those designs that have a zero impedance source , see Figure 3. 1. State A: Initial charge. Here the battery's charging current is limited by the wall adapter's natural impedance. The battery voltage approaches 4.2V. 2. State B: Constant voltage charge. Here the battery voltage is at 4.2V 0.75% and the current is decaying in the battery. When the battery has reached approximately 1/10th of its 1C rating, the battery is considered to have reached full charge. Because of the natural characteristic impedance of the cheap wall adapters, as the battery voltage decreases so the input voltage increases. The MIC6270 and the LM4041 are configured as a simple voltage monitor, indicating when the 5V 5%@ 400mA 5% MIC79050-4.2BM IN BAT 0.050 EN FB GND 1k 4.7F 10k R2 8.06M 47k Q1 1k MIC7300 10k MIC6270 47k LM4041 CIM3-1.2 Figure 2. Protected Constant-Current Charger MIC79050 8 September 2001 MIC79050 Micrel Protected Constant-Current Charger Another form of charging is using a simple wall adapter that offers a fixed voltage at a controlled, maximum current rating. The output of a typical charger will source a fixed voltage at a maximum current unless that maximum current is exceeded. In the event that the maximum current is exceeded, the voltage will drop while maintaining that maximum current. Using an MIC79050 after this type of charger is ideal for lithium-ion battery charging. The only obstacle is end of charger termination. Using a simple differential amplifier and a similar comparator and reference circuit, similar to Figure 1, completes a single cell lithium-ion battery charger solution. Lithium-Ion Battery Charging Single lithium-ion cells are typically charged by providing a constant current and terminating the charge with constant voltage. The charge cycle must be initiated by ensuring that the battery is not in deep discharge. If the battery voltage is below 2.5V, it is commonly recommended to trickle charge the battery with 5mA to 10mA of current until the output is above 2.5V. At this point the battery can be charged with constant current until it reaches its top off voltage (4.2V for a typical single lithium-ion cell) or a time out occurs. For the constant-voltage portion of the charging circuit, an extremely accurate termination voltage is highly recommended. The higher the accuracy of the termination circuit, the more energy the battery will store. Since lithium-ion cells do not exhibit a memory effect, less accurate termination does not harm the cell but simply stores less usable energy in the battery. The charge cycle is completed by disabling the charge circuit after the termination current drops below a minimum recommended level, typically 50mA or less, depending on the manufacturer's recommendation, or if the circuit times out. Time Out The time-out aspect of lithium-ion battery charging can be added as a safety feature of the circuit. Often times this function is incorporated in the software portion of an application using a real-time clock to count out the maximum amount of time allowed in the charging cycle. When the maximum recommended charge time for the specific cell has been exceeded, the enable pin of the MIC79050 can be pulled low, and the output will float to the battery voltage, no longer providing current to the output. Figure 2 shows this solution in completion. The source is a fixed 5V source capable of a maximum of 400mA of current. When the battery demands full current (fast charge), the source will provide only 400mA and the input will be pulled down. The output of the MIC79050 will follow the input minus a small voltage drop. When the battery approaches full charge, the current will taper off. As the current across RS approaches 50mA, the output of the differential amplifier (MIC7300) will approach 1.225V, the reference voltage set by the LM4041. When it drops below the reference voltage, the output of the comparator (MIC6270) will allow the base of Q1 to be pulled high through R2. Zero-Output Impedance Source Charging Input voltage sources that have very low output impedances can be a challenge due to the nature of the source. Using the circuit in Figure 3 will provide a constant-current and constant voltage charging algorithm with the appropriate end-of-charge termination. The main loop consists of an op-amp controlling the feedback pin through the schottky diode, D1. The charge current through RS is held constant by the op-amp circuit until the output draws less than the set charge-current. At this point, the output goes constant-voltage. When the current through RS gets to less than 50mA, the difference amp output becomes less than the reference voltage of the MIC834 and the output pulls low. This sets the output of the MIC79050 less than nominal, stopping current flow and terminating charge. As a second option, the feedback pin of the MIC79050 can be modulated as in Figure 4. Figure 4. shows a simple circuit where the MIC834, an integrated comparator and reference, monitors the battery voltage and disables the MIC79050 output after the voltage on the battery exceeds a set vaue. When the voltage decays below this set threshold, the MIC834 drives Q1 low allowing the MIC79050 to turn on MIC79050-4.2BM RS=0.200 5V IN BAT EN FB GND 16k 16.2k 1 MIC7122 2 D1 R2=124k 221k MIC834 VDD OUT R1=1k INP R3=1k 10k 8.06M SD101 0.01F 4.7F GND 1 MIC7122 2 R4=124k ICC = 80mV Rs IEOC = 1.240V x R1 R 2 x RS Figure 3. September 2001 9 MIC79050 MIC79050 Micrel again and provide current to the battery until it is fully charged. This form of pulse charging is an acceptable way of maintaining the full charge on a cell until it is ready to be used. MIC79050-4.2BMM IN BAT VIN EN FB GND 4.7F Li-Ion Cell MIC4417 4.7F Li-Ion Cell 1k MIC834 VDD OUT 100k 40k 200pF R1 INP GND R2 Figure 5B. PWM Based Pulse-charging Applications GND R1 VBAT(low) = VREF 1 + R2 Figure 6 shows another application to increase the output current capability of the MIC79050. By adding an external PNP power transistor, higher output current can be obtained while maintaining the same accuracy. The internal PNP now becomes the driver of a darlington array of PNP transistors, obtaining much higher output currents for applications where the charge rate of the battery is much higher. VREF=1.240V Figure 4. Pulse Charging For Top-off Voltage Charging Rate Lithium-ion cells are typically charged at rates that are fractional multiples of their rated capacity. The maximum varies between 1C - 1.3C (1x to 1.3x the capacity of the cell). The MIC79050 can be used for any cell size. The size of the cell and the current capability of the input source will determine the overall circuit charge rate. For example, a 1200mAh battery charged with the MIC79050 can be charged at a maximum of 0.5C. There is no adverse effects to charging at lower charge rates; that charging will just take longer. Charging at rates greater than 1C are not recommended, or do they decrease the charge time linearly. The MIC79050 is capable of providing 500mA of current at its nominal rated output voltage of 4.2V. If the input is brought below the nominal output voltage, the output will follow the input, less the saturation voltage drop of the pass element. If the cell draws more than the maximum output current of the device, the output will be pulled low, charging the cell at 600mA to 700mA current. If the input is a fixed source with a low output impedance, this could lead to a large drop across the MIC79050 and excess heating. By driving the feedback pin with an external PWM-circuit, the MIC79050 can be used to pulse charge the battery to reduce power dissipation and bring the device and the entire unit down to a lower operating temperature. Figure 5 shows a typical configuration for a PWM-based pulse-charging topology. Two circuits are shown in Figure 5: circuit a uses an external PWM signal to control the charger, while circuit b uses the MIC4417 as a low dutycycle oscillator to drive the base of Q1. (Consult the battery manufacturer for optimal pulse-charging techniques). VIN MIC79050-4.2BMM IN BAT EN FB GND VIN=4.5V to 16V MIC79050-4.2BMM IN BAT EN FB GND MIC79050-4.2BMM IN BAT 4.7F EN FB GND Figure 6. High Current Charging Regulated Input Source Charging When providing a constant-current, constant-voltage, charger solution from a well-regulated adapter circuit, the MIC79050 can be used with external components to provide a constant voltage, constant-current charger solution. Figure 7 shows a configuration for a high-side battery charger circuit that monitors input current to the battery and allows a constant current charge that is accurately terminated with the MIC79050. The circuit works best with smaller batteries, charging at C rates in the 300mA to 500mA range. The MIC7300 op-amp compares the drop across a current sense resistor and compares that to a high-side voltage reference, the LM4041, pulling the feedback pin low when the circuit is in the constant-current mode. When the current through the resistor drops and the battery gets closer to full charge, the output of the op-amp rises and allows the internal feedback network of the regulator take over, regulating the output to 4.2V. RS 16.2k 4.7F Li-Ion Cell MIC79050-4.2BMM IN BAT EN FB GND 4.7F MIC7300 LM4041CIM3-1.2 SD101 221k 10k ICC = 80mV RS 0.01F External PWM Figure 5A. Figure 7. Constant Current, MIC79050 10 September 2001 MIC79050 Micrel Constant Voltage Charger The MIC79050 is rated to a maximum junction temperature of 125C. It is important not to exceed this maximum junction temperature during operation of the device. To prevent this maximum junction temperature from being exceeded, the appropriate ground plane heat sink must be used. Figure 9 shows curves of copper area versus power dissipation, each trace corresponding to different temperature rises above ambient. From these curves, the minimum area of copper necessary for the part to operate safely can be determined. The maximum allowable temperature rise must be calculated to determine operation along which curve. Simple Charging The MIC79050 is available in a three-terminal package, allowing for extremely simple battery charging. When used with a current-limited, low-power input supply, the MIC790504.2BS completes a very simple, low-charge-rate, batterycharger circuit. It provides the accuracy required for termination, while a current-limited input supply offers the constantcurrent portion of the algorithm. Thermal Considerations The MIC79050 is offered in three packages for the various applications. The SOT-223 is most thermally efficient of the three packages, with the power SOP-8 and the power MSOP-8 following suit. Power SOP-8 Thermal Characteristics One of the secrets of the MIC79050's performance is its power SO-8 package featuring half the thermal resistance of a standard SO-8 package. Lower thermal resistance means more output current or higher input voltage for a given package size. Lower thermal resistance is achieved by joining the four ground leads with the die attach paddle to create a singlepiece electrical and thermal conductor. This concept has been used by MOSFET manufacturers for years, proving very reliable and cost effective for the user. Thermal resistance consists of two main elements, JC, or thermal resistance junction to case and CA, thermal resistance case to ambient (Figure 8). JC is the resistance from the die to the leads of the package. CA is the resistance from the leads to the ambient air and it includes CS, thermal resistance case to sink, and SA, thermal resistance sink to ambient. Using the power SOP-8 reduces the JC dramatically and allows the user to reduce CA. The total thermal resistance, JA, junction to ambient thermal resistance, is the limiting factor in calculating the maximum power dissipation capability of the device. Typically, the power SOP-8 has a JC of 20C/W, this is significantly lower than the standard SOP8 which is typically 75C/W. CA is reduced because pins 58 can now be soldered directly to a ground plane, which significantly reduces the case to sink thermal resistance and sink to ambient thermal resistance. TJA = 600 500 400 300 200 100 0 0 0.25 0.50 0.75 1.00 1.25 1.50 POWER DISSIPATION (W) Figure 9. Copper Area vs. Power-SOP Power Dissipation ( (TJA) Where T = Tj(max) - Ta(max) Tj(max) = 125C Ta(max) = maximum ambient operating temperature For example, the maximum ambient temperature is 40C, the T is determined as follows: T = +125C - 40C T = +85C Using Figure 9, the minimum amount of required copper can be determined based on the required power dissipation. Power dissipation in a linear regulator is calculated as follows: PD = (Vin-Vout)*Iout + Vin*Ignd For example, using the charging circuit in Figure 7, assume the input is a fixed 5V and the output is pulled down to 4.2V at a charge current of 500mA. The power dissipation in the MIC79050 is calculated as follows: PD = (5V - 4.2V)*0.5A + 5V*0.012A PD = 0.460W SOP-8 From Figure 9, the minimum amount of copper required to operate this application at a T of 85C is less than 50mm2. Quick Method Determine the power dissipation requirements for the design along with the maximum ambient temperature at which the device will be operated. Refer to Figure 10 , which shows safe operating curves for 3 different ambient temperatures: +25C, +50C and +85C. From these curves, the minimum amount of copper can be determined by knowing the maximum power JA JC 700 100C COPPER AREA (mm2) 800 40C 50C 55C 65C 75C 85C 900 CA ground plane heat sink area AMBIENT printed circuit board Figure 8. Thermal Resistance September 2001 11 MIC79050 MIC79050 Micrel Power MSOP-8 Thermal Characteristics The power-MSO-8 package follows the same idea as the power-SO-8 package, using four ground leads with the die attach paddle to create a single-piece electrical and thermal conductor, reducing thermal resistance and increasing power dissipation capability. The same method of determining the heat sink area used for the power-SOP-8 can be applied directly to the powerMSOP-8. The same two curves showing power dissipation versus copper area are reproduced for the power-MSOP-8 and they can be applied identically. Quick Method Determine the power dissipation requirements for the design along with the maximum ambient temperature at which the device will be operated. Refer to Figure 12, which shows safe operating curves for 3 different ambient temperatures, +25C, +50C and +85C. From these curves, the minimum amount of copper can be determined by knowing the maximum power dissipation required. If the maximum ambient temperature is +25C and the power dissipation is 1W, the curve in Figure 12v shows that the required area of copper is 500mm2,when using the power MSOP-8 dissipation required. If the maximum ambient temperature is +40C and the power dissipation is as above, 0.46W, the curve in Figure 10 shows that the required area of copper is 50mm2. The JA of this package is ideally 63C/W, but it will vary depending upon the availability of copper ground plane to which it is attached. COPPER AREA (mm2) 900 800 T = 125C J 700 85C 50C 25C 600 500 400 300 200 100 0 0 0.25 0.50 0.75 1.00 1.25 1.50 POWER DISSIPATION (W) Figure 10. Copper Area vs. Power-SOP Power Dissipation (TA) 700 100C COPPER AREA (mm2) 800 40C 50C 55C 65C 75C 85C 900 600 500 400 300 200 100 0 0 0.25 0.50 0.75 1.00 1.25 1.50 POWER DISSIPATION (W) Figure 11. Copper Area vs. Power-MSOP Power Dissipation (TJA) 900 COPPER AREA (mm2) 800 700 TJ = 125C 85C 50C 25C 600 500 400 300 200 100 0 0 0.25 0.50 0.75 1.00 1.25 1.50 POWER DISSIPATION (W) Figure 12. Copper Area vs. Power-MSOP Power Dissipation (TA) MIC79050 12 September 2001 MIC79050 Micrel Package Information 3.15 (0.124) 2.90 (0.114) CL 3.71 (0.146) 7.49 (0.295) 3.30 (0.130) 6.71 (0.264) CL 2.41 (0.095) 2.21 (0.087) 1.04 (0.041) 0.85 (0.033) 4.7 (0.185) 4.5 (0.177) 0.10 (0.004) 0.02 (0.0008) DIMENSIONS: MM (INCH) 6.70 (0.264) 6.30 (0.248) 1.70 (0.067) 16 1.52 (0.060) 10 10 MAX 0.38 (0.015) 0.25 (0.010) 0.84 (0.033) 0.64 (0.025) 0.91 (0.036) MIN SOT-223 (S) 0.026 (0.65) MAX) PIN 1 0.157 (3.99) 0.150 (3.81) DIMENSIONS: INCHES (MM) 0.050 (1.27) TYP 0.064 (1.63) 0.045 (1.14) 0.197 (5.0) 0.189 (4.8) 0.020 (0.51) 0.013 (0.33) 0.0098 (0.249) 0.0040 (0.102) 0-8 SEATING PLANE 45 0.010 (0.25) 0.007 (0.18) 0.050 (1.27) 0.016 (0.40) 0.244 (6.20) 0.228 (5.79) 8-Pin SOP (M) September 2001 13 MIC79050 MIC79050 Micrel 0.122 (3.10) 0.112 (2.84) 0.199 (5.05) 0.187 (4.74) DIMENSIONS: INCH (MM) 0.120 (3.05) 0.116 (2.95) 0.036 (0.90) 0.032 (0.81) 0.043 (1.09) 0.038 (0.97) 0.012 (0.30) R 0.012 (0.03) 0.0256 (0.65) TYP 0.008 (0.20) 0.004 (0.10) 5 MAX 0 MIN 0.007 (0.18) 0.005 (0.13) 0.012 (0.03) R 0.039 (0.99) 0.035 (0.89) 0.021 (0.53) 8-Pin MSOP (MM) MIC79050 14 September 2001 MIC79050 September 2001 Micrel 15 MIC79050 MIC79050 Micrel MICREL INC. TEL 1849 FORTUNE DRIVE SAN JOSE, CA 95131 + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB USA http://www.micrel.com This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. (c) 2001 Micrel Incorporated MIC79050 16 September 2001