MIC4682 Precision Current Limit SOIC-8 SuperSwitcher™ Buck Regulator General Description Features The MIC4682 is an easy-to-use step-down (buck) switch• Programmable output current limit mode voltage regulator. It features a programmable – 10% accuracy over temperature current limit that allows 10% current limit accuracy over its • Wide 4V to 34V operating input voltage range full operating temperature range. The precision current • Fixed 200kHz PWM operation limit makes the MIC4682 ideal for constant-voltage • Power SOIC-8 package allows 2A continuous output constant-current applications, such as simple battery current chargers. The precision current limit also gives designers the ability to set the maximum output current below the • All surface mount solution saturation current rating of the inductor. This allows the • Internally compensated use of the smallest possible inductors for a given • Less than 1µA typical shutdown-mode current application, saving valuable space and cost. • Thermal shutdown protection The MIC4682 is a very robust device. Its 4V to 34V input voltage range allows the MIC4682 to safely be used in applications where voltage transients may be present. Applications Additional protection features include cycle-by-cycle • Battery chargers current limiting and over-temperature shutdown. The • White LED drivers MIC4682 is available in a thermally optimized power SOIC-8 package that allows it to achieve 2A of continuous • Constant voltage constant current step-down output current. converters The MIC4682 requires a minimum number of external • Simple step-down regulator with precise current limit components and can operate using a standard series of • USB power supplies inductors. Compensation is provided internally for fast transient response and ease of use. The MIC4682 is available in the 8-pin power SOIC with a –40°C to +125°C junction temperature range. Data sheets and support documentation can be found on Micrel’s web site at: www.micrel.com. ___________________________________________________________________________________________________________ Typical Application MIC4682 5 4 IN SW SHDN R3 10M ISET 3 FB 8 L1 68µH 5V/1A 6 R1 3.01k 1 GND 2, 6, 7 R4 16.2k D1 B240 R2 976 C2 220µF 10V OUTPUT VOLTAGE (V) +7.5V to +34V C1 10µF 50V (x2) MIC4682 Current Limit Characteristics 5 4 3 2 1 VIN = 12V 0 0 0.5 1 1.5 CURRENT LIMIT (A) 2 Constant Current/Constant Voltage Li-Ion Battery Charger SuperSwitcher is a trademark of Micrel, Inc Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com June 2007 M9999-061507 Micrel, Inc. MIC4682 Ordering Information Part Number Standard Pb-Free MIC4682BM MIC4682YM Voltage Junction Temp. Range Package Adj. –40° to +125°C 8-Pin SOIC Note: Other Voltage available. Contact Micrel for details. Pin Configuration FB 1 8 SW GND 2 7 GND ISET 3 6 GND SHDN 4 5 IN 8-Pin Power SOIC (M) Pin Description Pin Number Pin Name 1 FB 2, 6, 7 GND Ground (Return): Ground. 3 ISET Current Limit Set (Input): Connect an external resistor to ground to set the current limit. Do not ground or float this pin. 4 SHDN Shutdown (Input): Logic low (<0.8V) enables regulator. Logic high (>2V) shuts down regulator. June 2007 5 IN 8 SW Pin Function Feedback (Input): Output voltage sense node. Connect to 1.23V-tap of the output voltage-divider network. Supply Voltage (Input): Unregulated +4V to +34V supply voltage. Switch (Output): Internal power emitter of NPN output switch. 2 M9999-061507 Micrel, Inc. MIC4682 Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN)(3) ....................................................38V Shutdown Voltage (VSHDN)............................. –0.3V to +38V Steady-State Output Switch Voltage (VSW) ....................–1V Feedback Voltage (VFB) .................................................12V Current Limit Set Voltage (VISET) ....................... 1.23V to 7V Ambient Storage Temperature (Ts) ...........–65°C to +150°C ESD Rating(5) .................................................................. 2kV Supply Voltage (VIN)(4, 7) ....................................... 4V to 34V Junction Temperature Range (TJ)............. –40°C to +125°C Thermal Resistance Impedance SOIC (θJA)(6) .......................................................63°C/W SOIC (θJC)(6) .......................................................20°C/W Electrical Characteristics VIN = 12V; IOUT = 500mA; RISET = 16.2k (1A current limit); TJ = 25°C, bold values indicate –40°C< TJ < +125°C, unless noted. Symbol Parameter Condition VIN Supply Voltage Range Note 4 IIN Quiescent Current Min Typ Max 34 V VFB = 1.5V 7 12 mA Standby Quiescent Current VSHDN = 5V (Regulator off) 35 100 µA Feedback Voltage (±1%) (±2%) 1.217 1.205 1.230 1.243 1.255 V V 8V ≤ VIN ≤ 34V, 0.1A ≤ ILOAD ≤ 0.8A 1.193 1.180 1.230 1.267 1.280 V V 0.9 1 1.1 A 180 200 220 kHz 93 95 4 VSHDN = VIN VFB 1 ILIM Current Limit Accuracy, Note 7 fSW Oscillator Frequency DMAX Maximum Duty Cycle VFB = 1.0V VSW Switch Saturation Voltage IOUT = 1A ISW Switch Leakage Current VIN = 34V, VSHDN = 5V, VSW = 0V VSHDN Shutdown Input Logic Level See Test Circuit, VOUT = 3.6V VIN = 34V, VSHDN = 5V, VSW = –1V Regulator Off 2 Regulator On ISHDN TJ Shutdown Input Current Units µA % 1.4 1.8 V 2 100 µA 2 10 mA 1.4 V 1.25 0.8 V VSHDN = 5V (Regulator Off) –10 –0.5 1 µA VSHDN = 0V (Regulator On) –10 –0.5 1 µA Thermal Shutdown 160 °C Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Absolute maximum rating is intended for voltage transients only; prolonged DC operation is not recommended. 4. VIN(MIN) = VOUT + 2.5V or 4V whichever is greater. 5. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF. 6. Measured on 1.5” square of 1oz. copper FR4 printed circuit board connected to the device ground leads. 7. Short circuit protection is guaranteed to VIN = 30V max. June 2007 3 M9999-061507 Micrel, Inc. MIC4682 Test Circuit 5 C1 (x2) 10µF 50V 4 R3 10M IN SW SHDN ISET FB 68µH VOUT R1 3.01k C2 220µF 10V 1 GND 3 L1 8 D1 B240A OUTPUT VOLTAGE (V) MIC4682 V IN R2 2, 6, 7 RISET 5.0 3.6 10% 0 0.90 1.10 OUTPUT CURRENT (A) Current Limit Test Circuit Constant-Current Constant-Voltage Accuracy Shutdown Input Behavior OFF ON 0.8V 0V 1.25V 2V 1.4V VIN(max) Shutdown Hysteresis June 2007 4 M9999-061507 Micrel, Inc. MIC4682 Typical Characteristics TA = 25°C unless otherwise noted. 80 Efficiency vs. Output Current EFFICIENCY (%) 70 60 50 40 30 June 2007 2 R =10k 1.8 ISET R =15.8k 1.6 ISET 1.4 R =20k ISET 1.2 RISET=25k 1 RISET=30k 0.8 R ISET=40k 0.6 RISET=50k L = 68µH 0.4 R3 = 10M 0.2 VOUT~0V (Pulsed Load) 0 4 7 10 13 16 19 22 25 28 31 34 INPUT VOLTAGE (V) 5 SHORT CIRCUIT CURRENT LIMIT (A) CURRENT LIMIT (A) 2 VIN = 4V 1.8 VIN = 5V 1.6 VIN = 24V VIN = 12V 1.4 VIN = 30V 1.2 VIN = 34V 1 0.8 0.6 0.4 L = 68µH R3 = 10M 0.2 V OUT = 1.0V (Pulsed Load) 0 10 15 20 25 30 35 40 45 50 RISET (kΩ) SHORT CIRCUIT CURRENT LIMIT (A) 0 0 Short Circuit Current Limit vs. Input Voltageat TJ = –40°C VIN = 5V VIN = 30V 20 10 Current Limit vs. RISET at TJ = 125°C VIN = 6V VIN = 12V VOUT = 2.5V 0.4 0.8 1.2 1.6 OUTPUT CURRENT (A) 2 Short Circuit Current Limit vs. Input Voltageat TJ = 25°C 2 1.8 RISET=10k 1.6 1.4 RISET=15.8k 1.2 RISET=20k 1 RISET=25k 0.8 RISET=30k 0.6 RISET=40k L = 68µH 0.4 RISET=50k R3 = 10M 0.2 VOUT~0V (Pulsed Load) 0 4 8 12 16 20 24 28 32 INPUT VOLTAGE (V) M9999-061507 Micrel, Inc. MIC4682 12 Quiescent Current vs. Temperature INPUT CURRENT (mA) V = 24V 10 8 6 V = 12V 4 2 VFB = 1.5V VEN = 0V Short Circuit Current Limit vs. Input Voltageat T = 125°C J 2.0 RISET=10k 1.8 1.6 15.8k 1.4 1.2 RISET=20k 1.0 RISET=25k 0.8 RISET=30k 0.6 RISET=40k L = 68µH 0.4 R3 = 10M RISET=50k 0.2 VOUT~0V (Pulsed Load) 0 4 8 12 16 20 24 28 32 INPUT VOLTAGE (V) 140 0 -40 -20 0 20 40 60 80 100120 TEMPERATURE °C) ( 12 INPUT CURRENT (mA) SHORT CIRCUIT CURRENT LIMIT (A) Short Circuit Current Limit vs. Input Voltageat T = 85°C J 2 R =10k 1.8 ISET 1.6 1.4 RISET=15.8k RISET=20k 1.2 RISET=25k 1 RISET=30k 0.8 RISET=40k 0.6 RISET=50k L = 68µH 0.4 R3 = 10M 0.2 VOUT~0V (Pulsed Load) 0 4 8 12 16 20 24 28 32 INPUT VOLTAGE (V) SHUTDOWN CURRENT (µA) SHORT CIRCUIT CURRENT LIMIT (A) Typical Characteristics (continued) Quiescent Current vs. Input Voltage 10 8 6 4 2 0 0 VFB = 1.5V VEN = 0V 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) Shutdown Current vs. Input Voltage 120 100 80 60 40 V = 1.5V FB 20 VEN = VIN 0 0 250 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) Frequency vs. Temperature FREQUENCY (kHz) 245 240 VIN = 24V 235 230 VIN = 12V 225 220 215 VFB = 0V 210 -40 -20 0 20 40 60 80 100120 TEMPERATURE °C) ( OUTPUT VOLTAGE (V) 5.016 Load Regulation 5.014 5.012 5.01 5.008 5.006 5.004 5.002 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 OUTPUT CURRENT (A) June 2007 6 M9999-061507 Micrel, Inc. MIC4682 2 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 05 5V Output SOA OUTPUT CURRENT (A) 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 05 TA = 25°C TA = 60°C VOUT = 5V TJ = 125°C D = Max Peak ILIMIT= 2A 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 2.5V Output SOA 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 05 2 TA = 25°C OUTPUT CURRENT (A) OUTPUT CURRENT (A) OUTPUT CURRENT (A) Typical Safe Operating Area (SOA)(1) TA = 60°C VOUT = 2.5V TJ = 125°C D = Max Peak ILIMIT= 2A 1.8 1.6 TA = 25°C TA = 60°C VOUT = 3.3V TJ = 125°C D = Max Peak ILIMIT= 2A 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 1.8V Output SOA TA = 25°C 1.4 1.2 1 0.8 0.6 0.4 0.2 0 05 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 3.3V Output SOA TA = 60°C VOUT = 1.8V TJ = 125°C D = Max = 2A Peak I LIMIT 10 15 20 25 30 35 40 INPUT VOLTAGE (V) Note 1. SOA measured on the MIC4682 evaluation board. Functional Characteristics June 2007 7 M9999-061507 Micrel, Inc. MIC4682 Typical Bode Plots The following bode plots show that the MIC4682 is stable using a 68µH inductor (L) and a 220µF output capacitor (COUT).To assure stability, it is a good practice to maintain a phase margin of greater than 35°C. June 2007 8 M9999-061507 Micrel, Inc. MIC4682 Functional Diagram VIN ⎛ R1 ⎞ VOUT = VFB ⎜ + 1⎟ ⎝ R2 ⎠ IN SHDN VFB = 1.23V Internal Regulator ISET 200kHz Oscillator Thermal Shutdown ⎛V ⎞ R1 = R2 ⎜ OUT − 1⎟ ⎝ VFB ⎠ Current Limit R2 = R1 ⎛ VOUT ⎞ – 1⎟ ⎜ V ⎝ FB ⎠ Comparator VOUT SW Driver 2A Switch Reset COUT R1 FB Error Amp 1.23V Bandgap Reference R2 MIC4682 GND Figure 1. MIC4682 Block Diagram the maximum duty cycle which turns the switch off. The external resistor at the ISET pin sets the peak current limit. The maximum duty cycle is controlled by the Reset circuitry. At this time, energy is stored in the inductor. The current charges the output capacitor and supplies to the load. The Schottky diode is reversed bias. When the internal switch is off, the stored energy in the inductor starts to collapse. The voltage across the inductor reverses polarity and the inductor current starts to decrease. The Schottky diode clamps the switch voltage from going too negative and provides the path for the inductor current. During the off time, the inductor and the output capacitor provide current to the load. An internal regulator provides power to the control circuitry and the thermal protection circuitry turns off the internal switch when the junction temperature exceeds about 160°C. Functional Description The MIC4862 is a constant frequency, voltage modeswitching regulator. Referring to the block diagram, regulation is achieved when the feedback voltage is equal to the band gap reference. The FB pin senses the output voltage and feeds into the input of the Error Amp. The output of the Error Amp produces a positive voltage to compare with the 200kHz saw-tooth waveform. These two signals are fed into the comparator to generate the Pulse Width Modulation (PWM) signal to turn on and off the internal switch. The duty cycle is defined as the time the switch turns on divided by the period of the sawtooth oscillator. Initially, when power is applied to the IN pin, the duty cycle is high because the feedback is close to ground. As the output and feedback voltage start to rise, the duty cycle decreases. During the on time, current flows through the switch and into the inductor until it reaches the peak current limit or June 2007 9 M9999-061507 Micrel, Inc. MIC4682 Inductor and Output Capacitor A 68µH inductor and a 220µF tantalum output capacitor are chosen because of their stability over the input voltage range with maximum output current listed in the SOA typical tables. The Sumida CDRH127-680 and Vishay Sprague 593D106X9050D2T are recommended. See “Bode Plots” for additional information. With the same conditions, a lower value inductor and a higher output capacitor can be used. The disadvantages for this combination are that the output ripple voltage will be higher and the output capacitor’s package size will be bigger. For example, a 47µH inductor and 330µF output capacitor are good combination. Another option is to use a higher value inductor and a lower output capacitor. The advantages of this combination are that the switch peak current and the output ripple voltage will be lower. The disadvantage is that the inductor’s package size will be bigger. Applications that have lower output current requirement can use lower inductor value and output capacitor. See “Typical Application Circuits” for an example. A 0.1µF ceramic capacitor is recommended in parallel with the tantalum output capacitor to reduce the high frequency ripple. Application Information Output Voltage The output voltage of the MIC4682 is determined by using the following formulas: ⎛ R1 ⎞ VOUT = VFB ⎜ + 1⎟ ⎝ R2 ⎠ R2 = R1 ⎛ VOUT ⎞ ⎜⎜ ⎟⎟ − 1 ⎝ VFB ⎠ VFB = 1.23V For most applications, a 3.01k resistor is recommended for R1 and R2 can be calculated. Input Capacitor Low ESR (Equivalent Series Resistance) capacitor should be used for the input capacitor of the MIC4862 to minimize the input ripple voltage. Selection of the capacitor value will depend on the input voltage range, inductor value, and the load. Two Vishay Sprague 593D106X9050D2T (10µF/50V), tantalum capacitors are good values to use for the conditions listed in the SOA typical tables. A 0.1µF ceramic capacitor is recommended in parallel with the tantalum capacitors to filter the high frequency ripple. The ceramic capacitor should be placed close to the IN pin of the MIC4682 for optimum result. For applications that are cost sensitive, electrolytic capacitors can be used but the input ripple voltage will be higher. Current Limit Set Resistor An external resistor connects between the ISET pin and ground to control the current limit of the MIC4682 ranging from 400mA to 2A. For resistor value selections, see the “Typical Characteristics: Current Limit vs. RISET." In addition to the RISET, a resistor, ranging from 10MΩ to 15MΩ, between the ISET and IN pin is recommended for current limit accuracy over the input voltage range. When the MIC4682 is in current limit, the regulator is incurrent mode. If the duty cycle is equal or greater than 50%, the regulator is in the sub-harmonic region. This lowers the average current limit. The below simplified equation determines at which input and output voltage the MIC4682 exhibits this condition. Diode A Schottky diode is recommended for the output diode. Most of the application circuits on this data sheet specify the Diode Inc. B340A or Micro Commercial SS34A surface mount Schottky diode. Both diodes have forward current of 3A and low forward voltage drop. These diodes are chosen to operate at wide input voltage range and at maximum output current. For lower output current and lower input voltage applications, a smaller Schottky diode such as B240A or equivalence can be used. June 2007 (VOUT + 1.4 ) > 50% VIN Do not short or float the ISET pin. Shorting the ISET pin will set a peak current limit greater than 2.1A. Floating the ISET pin will exhibit unstable conditions. To disable the current limit circuitry, the voltage at the ISET pin has to be between 2V and 7V. 10 M9999-061507 Micrel, Inc. MIC4682 Thermal Considerations The MIC4682 SuperSwitcher™ features the powerSOIC-8.This package has a standard 8-pin small-outline package profile, but with much higher power dissipation than a standard SOIC-8. Micrel’s MIC4682 SuperSwitcher™ family are the first DC-to-DC converters to take full advantage of this package. The reason that the power SOIC-8 has higher power dissipation (lower thermal resistance) is that pins 2, 6, 7 and the die-attach paddle are a single piece of metal. The die is attached to the paddle with thermally conductive adhesive. This provides a low thermal resistance path from the junction of the die to the ground pins. This design significantly improves package power dissipation by allowing excellent heat transfer through the ground leads to the printed circuit board. One limitation of the maximum output current on any MIC4682 design is the junction-to-ambient thermal resistance (θJA) of the design (package and ground plane). Examining θJA in more detail: θJA = (θJC + θCA) where: θJC = junction-to-case thermal resistance θCA = case-to-ambient thermal resistance θJC is a relatively constant 20°C/W for a power SOIC-8. θCA is dependent on layout and is primarily governed by the connection of pins 2, 6 and 7 to the ground plane. The purpose of the ground plane is to function as a heat sink. θJA is ideally 63°C/W, but will vary depending on the size of the ground plane to which the power SOIC-8 is attached. Minimum Copper/Maximum Current Method Using Figure 3, for a given input voltage range, determine the minimum ground-plane heat-sink area required for the application’s maximum continuous output current. Figure 3 assumes a constant die temperature of 75°C above ambient. Determining Ground-Plane Heat-Sink Area There are two methods of determining the minimum ground plane area required by the MIC4682. When designing with the MIC4682, it is a good practice to connect pins 2, 6 and 7 to the largest ground plane that is practical for the specific design. Quick Method Make sure that MIC4682 pins 2, 6 and 7 are connected to a ground plane with a minimum area of 6cm2. This ground plane should be as close to the MIC4682 as possible. The area may be distributed in any shape around the package or on any PCB layer as long as there is good thermal contact to pins 2, 6 and 7. This ground plane area is more than sufficient for most designs. Checking the Maximum Junction Temperature For this example, with an output power (POUT) of 5W, (5V output at 1A maximum with VIN = 12V) and 65°C maximum ambient temperature, what is the maximum junction temperature? Referring to the “Typical Characteristics: Efficiency vs. Output Current” graph, read the efficiency (η) for 1A output current at VIN = 12V or perform you own measurement. η = 81% The efficiency is used to determine how much of the output power (POUT) is dissipated in the regulator circuit (PD). June 2007 SOIC-8 JA JC CA AM BIE ground plane heat sink area NT printed circuit board CONTINUOUS OUTPUT CURRENT (A) Figure 2. Power SOIC-8 Cross Section 1.5 8V 1.0 12V 24V VIN = 30V 0.5 TA = 50°C 0 0 5 10 15 20 25 AREA (cm2) Figure 3. Output Current vs. Ground Plane Area 11 M9999-061507 Micrel, Inc. MIC4682 POUT − POUT η PD = 5W − 5W 0.81 Calculating the maximum junction temperature given a maximum ambient temperature of 65°C: TJ = 0.936 × 20°C/W + (45°C – 25°C) + 65°C TJ = 103.7°C This value is within the allowable maximum operating junction temperature of 125°C as listed in “Operating Ratings.” Typical thermal shutdown is 160°C and is listed in “Electrical Characteristics.” PD = 1.17W A worst-case rule of thumb is to assume that 80% of the total output power dissipation is in the MIC4682 (PD(IC)) and 20%is in the diode-inductor-capacitor circuit. PD(IC) = 0.8 PD PD(IC) = 0.8 × 1.17W PD(IC) = 0.936W Calculate the worst-case junction temperature: TJ = P D(IC) θJC + (TC – TA) + TA(max) where: TJ = MIC4682 junction temperature PD(IC) = MIC4682 power dissipation θJC = junction-to-case thermal resistance. The θJC for the MIC4682’s power-SOIC-8 is approximately 20°C/W. TC = “pin” temperature measurement taken at the entry point of pins 6 or 7. TA = ambient temperature TA(max) = maximum ambient operating temperature for the specific design. VIN +4V to +34V 5 Layout Considerations Layout is very important when designing any switching regulator. Rapidly changing currents through the printed circuit board traces and stray inductance can generate voltage transients which can cause problems. To minimize stray inductance and ground loops, keep trace lengths, indicated by the heavy lines in Figure 4, as short as possible. For example, D1 should be close to pin 7 and pin 8. CIN should be close to pin 5 and pin 6. See “Applications Information: Thermal Considerations” for ground plane layout. The feedback pin should be kept as far way from the switching elements (usually L1 and D1) as possible. A circuit with sample layouts are provided. See Figures 5a though 5e. Gerber files are available upon request. MIC4682BM IN SW VOUT L1 8 68µH COUT CIN 4 SHDN FB GND ISET Power SOIC-8 2 6 7 R1 1 D1 Load PD = R2 3 GND Figure 4. Critical Traces for Layout C1 10µF 50V J2 GND L1 68µH U1 MIC4682BM J1 VIN 4V to 34V 5 1 C2 10µF 50V C3 0.1µF 50V OFF SW 8 4 R9 10M JP1 3 3 R8 option 2 1 JP3c 2.0A 4 3 R7 16.2k JP3b 1.0A R6 25k 6 SHDN ISET GND 2 1 1 JP1 1-2=OFF JP1 2-3-ON 2 ON IN GND 7 FB 1 D1 B340A 2 C4 Option R1 3.01k R5 6.49k GND J3 VOUT 2 C5 220µF 10V R4 2.94k R3 1.78k C6 Option C7 0.1µF 50V R2 976 6 2 JP3a 0.6A 5 1 JP2a 1.8V 4 3 JP2b 2.5V 6 5 JP2c 3.3V 8 7 JP2d 5.0V J4 GND Figure 5a. Evaluation Board Schematic Diagram June 2007 12 M9999-061507 Micrel, Inc. MIC4682 Layout Example Figure 5b. Top Silkscreen Figure 5d. Bottom Silkscreen Figure 5c. Top Layer Figure 5e. Bottom Layer Bill of Materials Item Part Number C1, C2 593D106X005D2T C3, C7 VJ0805Y104KXAMT Manufacturer Description Qty. (1) 10µF/50V 2 (1) 0.1µF/50V 2 Vishay Sprague Vishay Vitramon (1) C5 593D227X0010D2T Vishay Sprague D1 B340A Diodes, Inc L1 U1 CDRH127-680MC MIC4682BM Sumida (2) (3) (4) Micrel, Inc. 220µF/10V 1 Schottky 3A/40V 1 68µH, 2.1A ISAT 1 Precision Circuit Limit Buck Regulator 1 Notes: 1. Vishay: www.vishay.com 2. Diodes, Inc.: www.diodes.com 3. Sumida: www.sumida.com 4. Micrel, Inc.: www.website.com June 2007 13 M9999-061507 Micrel, Inc. MIC4682 Typical Application Circuits MIC4682 V IN 11V to 24V C1 10µF/25V Taiyo Yuden TMK432BJ106MM 5 R1 10M R2 28k 3 IN SW ISET SHDN 4 8 L1 47H Sumida CDRH6D28-470NC R3 3.01k 1 FB R4 GND 2,6,7 MIC79050 2 1 IN C2 EN 100µF GND 10V(x2) AVX 5-8 TPSC107M010R0200 BAT FB VOUT 4.2V 0.75% 3 4 C3 4.7µF/20V AVX TPSA475M020R1800 GND GND D1 1A/40V MBRX140 Micro Commercial Components OUTPUT VOLTAGE (V) 4.5 MIC4682 Current Limit Characteristics 4 3.5 3 VIN = 12V 250 500 750 1000 OUTPUT CURRENT (mA) VOLTAGE (V) Typical Charging Characteristics 5 Constant Current 4.5 Constant Voltage 4 3.5 VIN = 12V 3 Batt = 1.25Ah 2.5 Cutoff Voltage = 3.0V 2 1.5 1 0.5 0 0 1 2 3 4 5 6 TIME (hrs) 0.6 0.5 0.4 0.3 0.2 CURRENT (A) 2.5 0 0.1 7 0 Figure 6.Low-Cost Li Ion Battery Charger with 0.75% Precision Output Voltage June 2007 14 M9999-061507 Micrel, Inc. MIC4682 Package Information 8-Pin SOIC (M) MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2003 Micrel, Incorporated. June 2007 15 M9999-061507