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MIC4682
Precision Current Limit SOIC-8 SuperSwitcherTM 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 1A 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 -40C to +125C junction temperature range. Data sheets and support documentation can be found on Micrel's web site at: www.micrel.com. ___________________________________________________________________________________________________________
Typical Application
+7.5V to +34V C1 10F 50V (x2) MIC4682
5
IN
SW
8
L1 68H R1 3.01k R2 976
5V/1A
6 OUTPUT VOLTAGE (V)
MIC4682 Current Limit Characteristics
4
SHDN
FB GND
1
R3 10M ISET 3 R4 16.2k
D1 B240
C2 220F 10V
5 4 3 2 1 VIN = 12V 0 0 0.5 1 1.5 CURRENT LIMIT (A) 2
2, 6, 7
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
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MIC4682
Ordering Information
Part Number Standard MIC4682BM Pb-Free MIC4682YM Voltage Adj. Junction Temp. Range -40 to +125C Package 8-Pin SOIC
Note: Other Voltage available. Contact Micrel for details.
Pin Configuration
FB 1 GND 2 ISET 3 SHDN 4 8 7 6 5 SW GND GND IN
8-Pin Power SOIC (M)
Pin Description
Pin Number
1 2, 6, 7 3 4 5 8
Pin Name
FB GND ISET SHDN IN SW
Pin Function
Feedback (Input): Output voltage sense node. Connect to 1.23V-tap of the output voltage-divider network. Ground (Return): Ground. Current Limit Set (Input): Connect an external resistor to ground to set the current limit. Do not ground or float this pin. Shutdown (Input): Logic low (<0.8V) enables regulator. Logic high (>2V) shuts down regulator. Supply Voltage (Input): Unregulated +4V to +34V supply voltage. Switch (Output): Internal power emitter of NPN output switch.
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Absolute Maximum Ratings(1)
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) ...........-65C to +150C ESD Rating(5) .................................................................. 2kV
Operating Ratings(2)
Supply Voltage (VIN)(4, 7) ....................................... 4V to 34V Junction Temperature Range (TJ)............. -40C to +125C Thermal Resistance Impedance SOIC (JA)(6) .......................................................63C/W SOIC (JC)(6) .......................................................20C/W
Electrical Characteristics
VIN = 12V; IOUT = 500mA; RISET = 16.2k (1A current limit); TJ = 25C, bold values indicate -40C< TJ < +125C, unless noted.
Symbol
VIN IIN
Parameter
Supply Voltage Range Quiescent Current Standby Quiescent Current
Condition Note 4
VFB = 1.5V VSHDN = 5V (Regulator off) VSHDN = VIN (1%) (2%) 8V VIN 34V, 0.1A ILOAD 0.8A
Min
4
Typ
7 35 1
Max
34 12 100 1.243 1.255 1.267 1.280
Units
V mA A A V V V V A kHz % V A mA V V A A C
VFB
Feedback Voltage
1.217 1.205 1.193 1.180
1.230 1.230 1 200 95 1.4 2 2
ILIM fSW DMAX VSW ISW VSHDN ISHDN TJ
Notes:
Current Limit Accuracy, Note 7 Oscillator Frequency Maximum Duty Cycle Switch Saturation Voltage Switch Leakage Current Shutdown Input Logic Level Shutdown Input Current Thermal Shutdown
See Test Circuit, VOUT = 3.6V VFB = 1.0V IOUT = 1A VIN = 34V, VSHDN = 5V, VSW = 0V VIN = 34V, VSHDN = 5V, VSW = -1V Regulator Off Regulator On VSHDN = 5V (Regulator Off) VSHDN = 0V (Regulator On)
0.9
180 93
1.1
220
1.8
100 10 0.8 1 1
2 -10 -10
1.4 1.25 -0.5 -0.5 160
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, 1.5k 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.
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Test Circuit
OUTPUT VOLTAGE (V)
V IN C1 (x2) 10F 50V R3 10M MIC4682
5
IN
SW
8
L1 68H R1 3.01k R2
VOUT C2 220F 10V
5.0
4
SHDN ISET
3
FB GND
1
D1 B240A
3.6 10% 0 0.90 OUTPUT CURRENT (A) 1.10
2, 6, 7
RISET
Current Limit Test Circuit
Constant-Current Constant-Voltage Accuracy
Shutdown Input Behavior
OFF ON 0.8V 0V 1.25V 1.4V 2V VIN(max)
Shutdown Hysteresis
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Typical Characteristics
TA = 25C unless otherwise noted.
80 70 EFFICIENCY (%) 60 50 40 30 20 10 0 0 VOUT = 2.5V 0.4 0.8 1.2 1.6 OUTPUT CURRENT (A) 2 VIN = 6V VIN = 12V VIN = 30V VIN = 5V
Efficiency vs. Output Current
SHORT CIRCUIT 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 = 68H R3 = 10M 0.2 V OUT = 1.0V (Pulsed Load) 0 10 15 20 25 30 35 40 45 50 RISET (k)
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 RISET=40k 0.6 RISET=50k L = 68H 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)
SHORT CIRCUIT CURRENT LIMIT (A)
Current Limit vs. RISET at TJ = 125C
Short Circuit Current Limit vs. Input Voltageat TJ = -40C
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 = 68H 0.4 RISET=50k R3 = 10M 0.2 VOUT~0V (Pulsed Load) 0 4 8 12 16 20 24 28 32 INPUT VOLTAGE (V)
Short Circuit Current Limit vs. Input Voltageat TJ = 25C
CURRENT LIMIT (A)
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Typical Characteristics (continued)
SHORT CIRCUIT CURRENT LIMIT (A) J 2 RISET=10k 1.8 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 = 68H 0.4 R3 = 10M 0.2 VOUT~0V (Pulsed Load) 0 4 8 12 16 20 24 28 32 INPUT VOLTAGE (V) SHORT CIRCUIT CURRENT LIMIT (A)
Short Circuit Current Limit vs. Input Voltageat T = 85C
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 = 68H 0.4 R3 = 10M RISET=50k 0.2 VOUT~0V (Pulsed Load) 0 4 8 12 16 20 24 28 32 INPUT VOLTAGE (V)
Short Circuit Current Limit vs. Input Voltageat T = 125C
12 INPUT CURRENT (mA) 10 8 6 4 2 0 0
Quiescent Current vs. Input Voltage
VFB = 1.5V VEN = 0V 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
12 INPUT CURRENT (mA) 10 8 6 4 2
Quiescent Current vs. Temperature
V = 24V SHUTDOWN CURRENT (A)
140 120 100 80 60
Shutdown Current vs. Input Voltage
V = 12V
VFB = 1.5V VEN = 0V
40 V = 1.5V FB 20 VEN = VIN 0 0 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
0 -40 -20 0 20 40 60 80 100120 TEMPERATURE C) (
250 245 FREQUENCY (kHz) 240 235 230 225 220 215
Frequency vs. Temperature
VIN = 24V VIN = 12V
VFB = 0V 210 -40 -20 0 20 40 60 80 100120 TEMPERATURE C) (
5.016 OUTPUT VOLTAGE (V) 5.014 5.012 5.01 5.008 5.006 5.004
Load Regulation
5.002 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 OUTPUT CURRENT (A)
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Typical Safe Operating Area (SOA)(1)
2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 05
5V Output SOA
OUTPUT CURRENT (A)
TA = 25C
TA = 60C VOUT = 5V TJ = 125C D = Max Peak ILIMIT= 2A 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 05
3.3V Output SOA
TA = 25C
OUTPUT CURRENT (A)
TA = 60C VOUT = 3.3V TJ = 125C D = Max Peak ILIMIT= 2A 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
2 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 05
2.5V Output SOA
TA = 25C
2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 05
1.8V Output SOA
TA = 25C
TA = 60C VOUT = 2.5V TJ = 125C D = Max Peak ILIMIT= 2A 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
TA = 60C VOUT = 1.8V TJ = 125C 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
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Typical Bode Plots
The following bode plots show that the MIC4682 is stable using a 68H inductor (L) and a 220F output capacitor (COUT).To assure stability, it is a good practice to maintain a phase margin of greater than 35C.
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Functional Diagram
VIN IN SHDN ISET 200kHz Oscillator Internal Regulator
R1 VOUT = VFB + 1 R2 VFB = 1.23V V R1 = R2 OUT - 1 VFB R2 = R1 VOUT - 1 V FB
VOUT COUT R1 FB
Thermal Shutdown
Current Limit
Comparator SW Driver Reset 2A Switch
Error Amp MIC4682
1.23V Bandgap Reference GND
R2
Figure 1. MIC4682 Block Diagram
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
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 160C.
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MIC4682 Inductor and Output Capacitor A 68H inductor and a 220F 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 47H inductor and 330F 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 0.1F ceramic capacitor is recommended in parallel with the tantalum output capacitor to reduce the high frequency ripple. 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 10M to 15M, 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.
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 V FB
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 (10F/50V), tantalum capacitors are good values to use for the conditions listed in the SOA typical tables. A 0.1F 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. 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.
(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.
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Thermal Considerations
The MIC4682 SuperSwitcherTM 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 SuperSwitcherTM 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 (JA) of the design (package and ground plane). Examining JA in more detail: JA = (JC + CA) where: JC = junction-to-case thermal resistance CA = case-to-ambient thermal resistance JC is a relatively constant 20C/W for a power SOIC-8. CA 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. JA is ideally 63C/W, but will vary depending on the size of the ground plane to which the power SOIC-8 is attached.
SOIC-8
JA JC CA
AM
BIE
ground plane heat sink area
NT
printed circuit board
Figure 2. Power SOIC-8 Cross Section
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 75C above ambient.
CONTINUOUS OUTPUT CURRENT (A) 1.5 8V 1.0 12V
24V VIN = 30V
0.5
TA = 50C 0 0 5 10 15 20 25 AREA (cm2)
Figure 3. Output Current vs. Ground Plane Area
Determining Ground-Plane Heat-Sink Area There are two methods of determining the minimum ground plane area required by the MIC4682. 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.
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.
Checking the Maximum Junction Temperature For this example, with an output power (POUT) of 5W, (5V output at 1A maximum with VIN = 12V) and 65C maximum ambient temperature, what is the maximum junction temperature? Referring to the "Typical Characteristics: Efficiency vs. Output Current" graph, read the efficiency () for 1A output current at VIN = 12V or perform you own measurement. = 81% The efficiency is used to determine how much of the output power (POUT) is dissipated in the regulator circuit (PD).
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MIC4682 Calculating the maximum junction temperature given a maximum ambient temperature of 65C: TJ = 0.936 x 20C/W + (45C - 25C) + 65C TJ = 103.7C This value is within the allowable maximum operating junction temperature of 125C as listed in "Operating Ratings." Typical thermal shutdown is 160C and is listed in "Electrical Characteristics."
PD =
5W - 5W 0.81
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 x 1.17W PD(IC) = 0.936W Calculate the worst-case junction temperature: TJ = P D(IC) JC + (TC - TA) + TA(max) where: TJ = MIC4682 junction temperature PD(IC) = MIC4682 power dissipation JC = junction-to-case thermal resistance. The JC for the MIC4682's power-SOIC-8 is approximately 20C/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 CIN Power SOIC-8 MIC4682BM IN SW
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.
5
8
L1 68H COUT
VOUT R1 Load
4
SHDN GND ISET
267 3
FB
1
D1
R2
GND
Figure 4. Critical Traces for Layout
U1 MIC4682BM
5 1
J1 VIN 4V to 34V C1 10F 50V J2 GND C2 10F 50V C3 0.1F 50V
OFF ON
IN
SW
8 1
1
L1 68H
2
JP1 1-2=OFF JP1 2-3-ON
2 4
D1 B340A
J3 VOUT C4 Option C5 220F 10V R4 2.94k R3 1.78k
6
SHDN ISET GND
2
GND FB GND
6
7 2 1
JP1
3
R9 10M R8 option R7 16.2k JP3b 1.0A
6
R1 3.01k
C6 Option
3
C7 0.1F 50V
R6 25k JP3a 0.6A
R5 6.49k
2
R2 976
8
2
JP3c 2.0A
4
JP2a 1.8V
4
JP2b 2.5V
JP2c 3.3V
JP2d 5.0V J4 GND
1
3
5
1
3
5
7
Figure 5a. Evaluation Board Schematic Diagram
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Layout Example
Figure 5b. Top Silkscreen
Figure 5d. Bottom Silkscreen
Figure 5c. Top Layer
Figure 5e. Bottom Layer
Bill of Materials
Item
C1, C2 C3, C7 C5 D1 L1
Part Number
593D106X005D2T VJ0805Y104KXAMT 593D227X0010D2T B340A CDRH127-680MC
Manufacturer
Vishay Sprague Vishay Sprague Diodes, Inc Sumida
(2) (3) (4) (1) (1)
Description
10F/50V 0.1F/50V 220F/10V Schottky 3A/40V 68H, 2.1A ISAT
Qty.
2 2 1 1 1
Vishay Vitramon
(1)
U1
Notes:
MIC4682BM
Micrel, Inc.
Precision Circuit Limit Buck Regulator
1
1. Vishay: www.vishay.com 2. Diodes, Inc.: www.diodes.com 3. Sumida: www.sumida.com 4. Micrel, Inc.: www.website.com
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Typical Application Circuits
MIC4682 V IN 11V to 24V C1 10F/25V Taiyo Yuden TMK432BJ106MM R1 10M R2 28k
5
IN ISET SHDN
4
SW FB GND
2,6,7
8
L1 47H Sumida CDRH6D28-470NC R3 3.01k R4
MIC79050
2
IN
BAT FB
3
VOUT 4.2V 0.75% C3 4.7F/20V AVX TPSA475M020R1800
3
1
C2 EN 100F GND 10V(x2) AVX 5-8 TPSC107M010R0200
1
4
GND D1 1A/40V MBRX140 Micro Commercial Components
GND
4.5 OUTPUT VOLTAGE (V)
MIC4682 Current Limit Characteristics
4
3.5
3 VIN = 12V 2.5 0 250 500 750 1000 OUTPUT CURRENT (mA)
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 01 2 3 4 5 6 TIME (hrs)
Typical Charging Characteristics
0.6 0.5 0.4 0.3 0.2 0.1 CURRENT (A)
VOLTAGE (V)
7
0
Figure 6.Low-Cost Li Ion Battery Charger with 0.75% Precision Output Voltage
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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. (c) 2003 Micrel, Incorporated.
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