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MIC4685
Micrel
MIC4685
3A SPAK SuperSwitcherTM Buck Regulator
Final Information
General Description
The MIC4685 is a high-efficiency 200kHz stepdown (buck) switching regulator. Power conversion efficiency of above 85% is easily obtainable for a wide variety of applications. The MIC4685 achieves 3A of continuous current in the 7-lead SPAK package. The thermal performance of the SPAK allows it to replace TO-220s and TO-263s (D2 PAKs) in many applications. The SPAK saves board space with a 36% smaller footprint than TO-263. High efficiency is maintained over a wide output current range by utilizing a boost capacitor to increase the voltage available to saturate the internal power switch. As a result of this high efficiency, only the ground plane of the PCB is needed for a heat sink. The MIC4685 allows for a high degree of safety. It has a wide input voltage range of 4V to 30V (34V transient), allowing it to be used in applications where input voltage transients may be present. Built-in safety features include over-current protection, frequency-foldback short-circuit protection, and thermal shutdown. The MIC4685 is available in an 7-lead SPAK package with a junction temperature range of -40C to +125C.
Features
* * * * * * * * * * * * * * * * * * * Low 2mm profile SPAK package 3A continuous output current Wide 4V to 30V input voltage range (34V transient) Fixed 200kHz PWM operation Over 85% efficiency Output voltage adjustable to 1.235V All surface mount solution Internally compensated with fast transient response Over-current protection Frequency foldback short-circuit protection Thermal shutdown Point of load power supplies Simple high-efficiency step-down regulators 5V to 3.3V/2A conversion 12V to 5V/3.3V/2.5V/1.8V 3A conversion Dual-output 5V conversion Base stations LCD power supplies Battery chargers
Applications
Ordering Information
Part Number MIC4685BR Voltage Adj Junction Temperature Range -40C to +125C Package SPAK-07L
Typical Applications
VIN 8V to 30V VIN 5V 10% VOUT 1.8V/3A R1 3.01k R2 6.49k COUT 330F 6.3V CIN 68F 10V
DBS 3A, 20V CBS 0.33F/50V
1 6 3
2 5
MIC4685BR IN BS EN SW FB GND
4, Tab
1 6 3
CBS 0.33F/50V L1 39H D1 3A 40V
2 5
MIC4685BR IN BS EN SW FB GND
4, Tab
L1 39H D1 3A 20V R1 3.01k R2 1.78k
VOUT 3.3V/2A 330F 6.3V
CIN 33F 35V
1.8V Output Converter
5V to 3.3V Converter
Micrel, Inc. * 1849 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 944-0970 * http://www.micrel.com
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MIC4685
MIC4685
Micrel
Pin Configuration
7 6 5 4 3 2 1 NC SW EN GND FB IN BS
TAB, GND
SPAK-07L (R)
Pin Description
Pin Number 1 2 3 4, Tab 5 6 7 Pin Name BS IN FB GND EN SW NC Pin Function Bootstrap Voltage Node (External Component): Connect to external boost capacitor. Supply (Input): Unregulated +4V to 30V supply voltage (34V transient) Feedback (Input): Outback voltage feedback to regulator. Connect to 1.235V tap of resistive divider. Ground Enable (Input): Logic high = enable; logic low = shutdown Switch (Output): Emitter of NPN output switch. Connect to external storage inductor and Schottky diode. No Connect. Tie this pin to ground.
Detailed Pin Description
Switch (SW, Pin 6) The switch pin is tied to the emitter of the main internal NPN transistor. This pin is biased up to the input voltage minus the VSAT of the main NPN pass element. The emitter is also driven negative when the output inductor's magnetic field collapses at turn-off. During the OFF time the SW pin is clamped by the output Schottky diode to a -0.5V typically. Ground (GND, Pin 4, Tab) There are two main areas of concern when it comes to the ground pin, EMI and ground current. In a buck regulator or any other non-isolated switching regulator the output capacitor(s) and diode(s) ground is referenced back to the switching regulator's or controller's ground pin. Any resistance between these reference points causes an offset voltage/IR drop proportional to load current and poor load regulation. This is why its important to keep the output grounds placed as close as possible to the switching regulator's ground pin. To keep radiated EMI to a minimum it is necessary to place the input capacitor ground lead as close as possible to the switching regulator's ground pin. Input Voltage (VIN, Pin 2) The VIN pin is the collector of the main NPN pass element. This pin is also connected to the internal regulator. The output diode or clamping diode should have its cathode as close as possible to this point to avoid voltage spikes adding to the voltage across the collector.
Bootstrap (BS, Pin 1) The bootstrap pin in conjunction with the external bootstrap capacitor provides a bias voltage higher than the input voltage to the MIC4685's main NPN pass element. The bootstrap capacitor sees the dv/dt of the switching action at the SW pin as an AC voltage. The bootstrap capacitor then couples the AC voltage back to the BS pin plus the dc offset of VIN where it is rectified and used to provide additional drive to the main switch, in this case a NPN transistor. This additional drive reduces the NPN's saturation voltage and increases efficiency, from a VSAT of 1.8V, and 75% efficiency to a VSAT of 0.5V and 88% efficiency respectively. Feedback (FB, Pin 3) The feedback pin is tied to the inverting side of an error amplifier. The noninverting side is tied to a 1.235V bandgap reference. An external resistor voltage divider is required from the output to ground, with the center tied to the feedback pin. Enable (EN, Pin 5) The enable (EN) input is used to turn on the regulator and is TTL compatible. Note: connect the enable pin to the input if unused. A logic-high enables the regulator. A logic-low shuts down the regulator and reduces the stand-by quiescent input current to typically 150A. The enable pin has an upper threshold of 2.0V minimum and lower threshold of 0.8V maximum. The hysterisis provided by the upper and lower thresholds acts as an UVLO and prevents unwanted turn on of the regulator due to noise.
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Absolute Maximum Ratings (Note 1)
Supply Voltage (VIN), Note 1 ...................................... +34V Enable Voltage (VEN) .................................... -0.3V to +VIN Steady-State Output Switch Voltage (VSW) ....... -1V to VIN Feedback Voltage (VFB) .............................................. +12V Storage Temperature (TS) ....................... -65C to +150C ESD Rating Note 3 ....................................................... 2kV
Operating Ratings (Note 2)
Supply Voltage (VIN) Note 4 ........................... +4V to +30V Junction Temperature (TJ) ....................... -40C to +125C Package Thermal Resistance JA, SPAK-7 Lead ............................................ 11.8C/W JC, SPAK-7 Lead .............................................. 2.2C/W
Electrical Characteristics
VIN = VEN = 12V, VOUT = 5V; IOUT = 500mA; TA = 25C, unless otherwise noted. Bold values indicate -40C TJ +125C. Parameter Feedback Voltage Condition (2%) (3%) 8V VIN 30V, 0.1A ILOAD 1A, VOUT = 5V, Note 4 Feedback Bias Current Maximum Duty Cycle Output Leakage Current VFB = 1.0V VIN = 30V, VEN = 0V, VSW = 0V VIN = 30V, VEN = 0V, VSW = -1V Quiescent Current Bootstrap Drive Current Bootstrap Voltage Frequency Fold Back Oscillator Frequency Saturation Voltage Short Circuit Current Limit Shutdown Current Enable Input Logic Level IOUT = 1A VFB = 0V, See Test Circuit VEN = 0V regulator on regulator off Enable Pin Input Current VEN = 0V (regulator off) VEN = 12V (regulator on) Thermal Shutdown @ TJ
Note 1. Note 2. Note 3. Note 4. Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. 2.5V of headroom is required between VIN and VOUT. The headroom can be reduced by implementing a bootstrap diode as seen on the 5V to 3.3V circuit on page 1.
Min 1.210 1.198 1.186 1.173
Typ 1.235 1.235 50 94 5 1.4 6
Max 1.260 1.272 1.284 1.297
Units V V V V nA % A mA mA mA V
500 20 12
VFB = 1.5V VFB = 1.5V, VSW = 0V IBS = 10mA, VFB = 1.5V, VSW = 0V VFB = 0V 250 5.5 30 180
380 6.2 70 200 0.59 120 225
kHz kHz V
3.5 150 2
6 200
A A V
0.8 16 -1 -0.83 160 50
V A mA C
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MIC4685
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Test Circuit
+12V
2
Device Under Test 6 VIN SW
1
68H
5
EN GND
4, Tab
BS FB
3
I
Current Limit Test Circuit
Shutdown Input Behavior
ON OFF
GUARANTEED OFF TYPICAL OFF
0.8V 1.25V 1.4V
2V
GUARANTEED ON TYPICAL ON
0V
VIN(max)
Enable Hysteresis
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Typical Characteristics
(TA = 25C unless otherwise noted)
Efficiency vs. Output Current
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 Standard Configuration VOUT = 5.0V VIN = 8V VIN = 30V 100 VIN = 12V
EFFICIENCY (%)
Efficiency vs. Output Current
90 80 70 60 50 40 30 20 VIN = 8V
EFFICIENCY (%)
Efficiency vs. Output Current
100 90 VIN = 8V 80 VIN = 24V
VIN = 30V
VIN = 12V
70 60 50 40 30 20
VIN = 30V
VIN = 12V
10 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT CURRENT (A)
10 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT CURRENT (A)
Standard Configuration VOUT = 3.3V
Standard Configuration 10 VOUT = 2.5V 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT CURRENT (A)
Efficiency vs. Output Current
90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 Standard Configuration VOUT = 1.8V VIN = 30V VIN = 12V VIN = 8V
EFFICIENCY (%)
Efficiency vs. Output Current
100 90 80 70 60 50 40 30 20 Bootstrap Configuration VOUT = 5.0V VIN = 7.5V
EFFICIENCY (%)
Efficiency vs. Output Current
100 90 80 VIN = 4.5V VIN = 12V VIN = 5V VIN = 16V
VIN = 24V
VIN = 16V
VIN = 12V
70 60 50 40 30 20
0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT CURRENT (A)
10 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT CURRENT (A)
Bootstrap Configuration 10 VOUT = 3.3V 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT CURRENT (A)
Efficiency vs. Output Current
100 90 80 VIN = 5V VIN = 12V EFFICIENCY (%) 90 80 70 60 50 40 30 20 10
Efficiency vs. Output Current
VIN = 5V 6.3 INPUT CURRENT (mA) VIN = 12V 6.2 6.1 6 5.9 5.8
Quiescent Current vs. Input Voltage
EFFICIENCY (%)
70 60 50 40 30 20
VIN = 16V
VIN = 16V
10 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT CURRENT (A)
Bootstrap Configuration VOUT = 2.5V
0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 OUTPUT CURRENT (A)
Bootstrap Configuration VOUT = 1.8V
VEN= 5V 5.7 0 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
Bootstrap Voltage vs. Input Voltage
7 BOOTSTRAP CURRENT (mA) 350 300 250 200 150 100 50
Bootstrap Drive Current vs. Input Voltage
12 10 DUTY CYCLE (%) 8 6 4 2 0 0
Minimum Duty Cycle vs. Input Voltage
BOOTSTRAP VOLTAGE (V)
6 5 4 3 2 1 0 0 5 VIN = 12V VFB = 1.5V 10 15 20 25 INPUT VOLTAGE (V) 30
0 0 2 4 6 8 10 12 14 16 18 20 INPUT VOLTAGE (V)
VIN = 12V VFB = 1.5V
VOUT = 1.8V 5 10 15 20 25 INPUT VOLTAGE (V) 30
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Feedback Voltage vs. Input Voltage
1.250 FEEDBACK VOLTAGE (V) 1.245 1.240 1.235 1.230 1.225 1.220 1.215 1.210 1.205 0 5 IOUT = 10mA VOUT = 1.8V 10 15 20 25 INPUT VOLTAGE (V) 30 200 180
INPUT CURRENT (A)
Shutdown Current vs. Input Voltage
605
SATURATION VOLTAGE (mV)
Saturation Voltage vs. Input Voltage
600 595 590 585 580 575 570 0 5 IOUT = 1A VOUT = 5V 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
160 140 120 100 80 60 40 20 0 0 5 VEN = 0V 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
Feedback Voltage vs. Temperature
1.258 FEEDBACK VOLTAGE (V)
OUTPUT VOLTAGE (V)
Shutdown Hysteresis vs. Temperature
6
OUTPUT VOLTAGE (V)
Load Regulation
1.809 1.808 1.807 1.806 1.805 1.804 1.803 1.802 0 VOUT = 13V 0.5 1 1.5 2 2.5 3 OUTPUT CURRENT (A) 3.5
1.248 1.238 1.228 1.218 1.208 IOUT = 10mA VIN = 12V VOUT = 1.8V
5 4 3 2 1 0 -1 -50 0 50 100 150 TEMPERATURE (C) 200 OFF ON
1.198 -40 -20 0 20 40 60 80 100120140 TEMPERATURE (C)
Line Regulation
1.83 THRESHOLD TRIP POINTS 1.20 1.18 1.16 1.14 1.12 1.10 1.08 1.06 1.04 1.02 1.00
Enable Threshold vs. Temperature
Upper Threshold
OUTPUT VOLTAGE (V)
1.82 1.81 1.80 1.79 1.78 1.77 1.76 0 IOUT = 0.100A 5 10 15 20 25 30 OUTPUT CURRENT (A) 35
Lower Threshold
VIN = 12V VOUT = 5V IOUT = 100mA -60 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C) 140
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Typical Safe Operating Area (SOA)
(SOA measured on the MIC4685 Evaluation Board*)
5V Output SOA Standard Configuration
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
3.3V Output SOA Standard Configuration
5.0
OUTPUT CURRENT (A)
2.5V Output SOA Standard Configuration
5.0 4.5 TA = 25C 4.0 TJ = 125C 3.5 D = Max 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 5
5.0 T = 25C 4.5 A TJ = 125C 4.0 D = Max 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 5 TA = 60C TJ = 125C D = Max 10 15 20 25 30 INPUT VOLTAGE (V) 35
4.5 TA = 25C 4.0 TJ = 125C 3.5 D = Max 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 5
TA = 60C TJ = 125C D = Max 10 15 20 25 30 INPUT VOLTAGE (V) 35
TA = 60C TJ = 125C D = Max 10 15 20 25 30 INPUT VOLTAGE (V) 35
1.8V Output SOA Standard Configuration
5.0 OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
5.0V Output SOA Bootstrap Configuration
4.5
OUTPUT CURRENT (A)
3.3V Output SOA Bootstrap Configuration
4.5 4.0 TA = 25C TJ = 125C 3.5 D = Max 3.0 2.5 2.0 1.5 1.0 0.5 0.0 3 5 7 9 11 13 15 17 INPUT VOLTAGE (V) TA = 60C TJ = 125C D = Max
T = 25C 4.5 A T = 125C 4.0 J D = Max 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 5
TA = 25C TJ = 125C 3.5 D = Max 3.0 4.0 2.5 2.0 1.5 1.0 0.5 0.0 6 8 TA = 60C TJ = 125C D = Max 10 12 14 16 INPUT VOLTAGE (V) 18
TA = 60C TJ = 125C D = Max 10 15 20 25 30 INPUT VOLTAGE (V) 35
2.5V Output SOA Bootstrap Configuration
5.0
1.8V Output SOA Bootstrap Configuration
5.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
T = 25C 4.5 A T = 125C 4.0 J D = Max 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
T = 25C 4.5 A T = 125C 4.0 J D = Max 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 TA = 60C TJ = 125C D = Max 3 5 7 9 11 13 15 17 INPUT VOLTAGE (V)
TA = 60C TJ = 125C D = Max 3 5 7 9 11 13 15 17 INPUT VOLTAGE (V)
* IOUT < 3A, D1: Diode Inc. B340 (3A/40V) IOUT > 3A, D1: SBM1040 (10A/40V)
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MIC4685
Micrel
Functional Characteristics
Switching Frequency Foldback
VSW (NORMAL) 12V IN, 5V/1A OUT
Load Transient
VIN = 12V VOUT = 5V IOUT = 1.0A to 0.1A
VOUT (100mV/div.)
Normal Operation
5.1V 5V
200kHz
VSW (SHORTED) 12V IN, 0V OUT
Short Circuit Operation Typical
IOUT (500mA/div.)
1A
0A
70kHz
TIME (25s/div.)
TIME
Frequency Foldback The MIC4685 folds the switching frequency back during a hard short circuit condition to reduce the energy per cycle and protect the device.
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Micrel
Block Diagrams
VIN IN
Bootstrap Charger Enable Internal Regulator
R1 VOUT = VREF + 1 R2 Current Limit V R1 = R2 OUT - 1 VREF VREF = 1.235V
200kHz Oscillator
Thermal Shutdown
Comparator SW Driver Reset R1 FB Error Amp MIC4685 1.235V Bandgap Reference R2 COUT VOUT
FIgure 1. Adjustable Regulator
Functional Description
The MIC4685 is a variable duty cycle switch-mode regulator with an internal power switch. Refer to the above block diagram. Supply Voltage The MIC4685 operates from a +4V to +30V (34V transient) unregulated input. Highest efficiency operation is from a supply voltage around +12V. See the efficiency curves in the Typical Characteristics section on page 5. Enable/Shutdown The enable (EN) input is TTL compatible. Tie the input high if unused. A logic-high enables the regulator. A logic-low shuts down the internal regulator which reduces the current to typically 150A when VEN = 0V. Feedback An external resistive voltage divider is required from the output voltage to ground, center tapped to the FB pin. See Table 1 and Table 2 for recommended resistor values. Duty Cycle Control A fixed-gain error amplifier compares the feedback signal with a 1.235V bandgap voltage reference. The resulting error amplifier output voltage is compared to a 200kHz sawtooth waveform to produce a voltage controlled variable duty cycle output.
A higher feedback voltage increases the error amplifier output voltage. A higher error amplifier voltage (comparator inverting input) causes the comparator to detect only the peaks of the sawtooth, reducing the duty cycle of the comparator output. A lower feedback voltage increases the duty cycle. The MIC4685 uses a voltage-mode control architecture. Output Switching When the internal switch is ON, an increasing current flows from the supply VIN, through external storage inductor L1, to output capacitor COUT and the load. Energy is stored in the inductor as the current increases with time. When the internal switch is turned OFF, the collapse of the magnetic field in L1 forces current to flow through fast recovery diode D1, charging COUT. Output Capacitor External output capacitor COUT provides stabilization and reduces ripple. Return Paths During the ON portion of the cycle, the output capacitor and load currents return to the supply ground. During the OFF portion of the cycle, current is being supplied to the output capacitor and load by storage inductor L1, which means that D1 is part of the high-current return path.
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MIC4685
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The efficiency is used to determine how much of the output power (POUT) is dissipated in the regulator circuit (PD). PD = PD = POUT - POUT
Applications Information
Adjustable Regulators Adjustable regulators require a 1.235V feedback signal. Recommended voltage-divider resistor values for common output voltages are included in Table 1. For other voltages, the resistor values can be determined using the following formulas:
R1 VOUT = VREF + 1 R2 V R1 = R2 OUT - 1 VREF VREF = 1.235V
Thermal Considerations The MIC4685 is capable of high current due to the thermally optimized SPAK package. One limitation of the maximum output current on any MIC4685 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 2.2C/W for a 7-lead SPAK. CA is dependent on layout and is primarily governed by the connection of pins 4, and Tab to the ground plane. The purpose of the ground plane is to function as a heat sink. Checking the Maximum Junction Temperature: For this example, with an output power (POUT) of 7.5W, (5V output at 1.5A with VIN = 12V) and 60C maximum ambient temperature, what is the junction temperature? Referring to the "Typical Characteristics: 5V Output Efficiency" graph, read the efficiency () for 1.5A output current at VIN = 12V or perform you own measurement. = 84%
7.5W - 7.5W 0.84 PD = 1.43W A worst-case rule of thumb is to assume that 80% of the total output power dissipation is in the MIC4685 (PD(IC)) and 20% is in the diode-inductor-capacitor circuit. PD(IC) = 0.8 PD PD(IC) = 0.8 x 1.43W PD(IC) = 1.14W Calculate the worst-case junction temperature: TJ = PD(IC) JC + (TC - TA) + TA(max) where: TJ = MIC4685 junction temperature PD(IC) = MIC4685 power dissipation JC = junction-to-case thermal resistance. The JC for the MIC4685's 7-lead SPAK is approximately 2.2C/W. TC = "pin" temperature measurement taken at the Tab. TA = ambient temperature TA(max) = maximum ambient operating temperature for the specific design. Calculating the maximum junction temperature given a maximum ambient temperature of 60C: TJ = 1.14 x 2.2C + (46C - 25C) + 60C TJ = 83.5C 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. Also see Typical Safe Operating Area (SOA) graphs on page 7.
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MIC4685
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 as short as possible. For example, keep D1 close to pin 6 and pin 4, and Tab, keep L1 away from sensitive node FB, and keep CIN close to pin 2 and pin 4, and Tab. 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 Figure 7. Gerber files are available upon request.
Micrel
Bootstrap Diode The bootstrap diode provides an external bias source directly to the main pass element, this reduces VSAT thus allowing the MIC4685 to be used in very low head-room applications i.e. 5VIN to 3.3VOUT with high efficiencies. Bootstrap diode not for use if VIN exceeds 16V, VIN. See Figure 3.
VIN +4V to +30V (34V transient) CIN 7-lead SPAK
MIC4685BR
2 5
IN EN
BS SW FB GND
4, Tab
1 6
L1 39H COUT D1
VOUT R1
3
R2
GND
Figure 2. Critical Traces for Layout
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MIC4685
MIC4685
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Recommended Components for a Given Output Voltage (Bootstrap Configuration)
VOUT IOUT* 5.0V 2.1A
R1 3.01k
R2 976
VIN 7.5V-16V
C1 47F, 20V Vishay-Dale 595D476X0020D2T 47F, 20V Vishay-Dale 595D476X0020D2T 47F, 20V Vishay-Dale 595D476X0020D2T 47F, 20V Vishay-Dale 595D476X0020D2T
D1
D2
L1
C4
3A, 30V 1A, 20V 39H 330F, 6.3V Schottky Schottky Sumida Vishay-Dale B330A MBRX120 CDRH127R-390MC 594D337X06R3D2T 3A, 30V 1A, 20V 39H 330F, 6.3V Schottky Schottky Sumida Vishay-Dale B330A MBRX120 CDRH127R-390MC 594D337X06R3D2T 3A, 30V 1A, 20V 39H 330F, 6.3V Schottky Schottky Sumida Vishay-Dale B330A MBRX120 CDRH127R-390MC 594D337X06R3D2T 3A, 30V 1A, 20V 39H 330F, 6.3V Schottky Schottky Sumida Vishay-Dale B330A MBRX120 CDRH127R-390MC 594D337X06R3D2T
3.3V
2.2A
3.01k
1.78k
6.0V-16V
2.5V
2.0A
3.01k
2.94k
5.0V-16V
1.8V
2.0A
3.01k
6.49k
5.0V-16V
*
Maximum output current at minimum input voltage. See SOA curves for maximum output current vs. input voltage.
Table 1. Recommended Components for Common Ouput Voltages
JP3 J1 VIN
D2 MBRX120 1A/20V L1 39H
6
U1 MIC4685BR
2
IN
SW BS
J2 VOUT
C1 47F 20V J3 GND
ON OFF
C2 0.1F 50V
1
C3 0.33F 50V D1 B330A or SS33
R1
C4* optional C5 330F 6.3V C7 0.1F 50V J4 GND
5
EN GND
4, Tab
FB
3
R2
* C4 can be used to provide additional stability and improved transient response. Note: optimized for 5VOUT
Figure 3. Schematic Diagram
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Recommended Components for a Given Output Voltage (Standard Configuration)
VOUT 5.0V
IOUT* 2.0A
R1 3.01k
R2 976
VIN 8V-30V
C1 33F, 35V Vishay-Dale 595D336X0035R2T 33F, 35V Vishay-Dale 595D336X0035R2T 33F, 35V Vishay-Dale 595D336X0035R2T 47F, 25V Vishay-Dale 595D476X0025D2T
D1 3A, 40V Schottky B340A 3A, 40V Schottky B340A 3A, 40V Schottky B340A 3A, 40V Schottky B340A
L1 39H Sumida CDRH127-390MC 39H Sumida CDRH127-390MC 39H Sumida CDRH127-390MC 39H Sumida CDRH127-390MC
C5 330F, 6.3V Vishay-Dale 594D337X06R3D2T 330F, 6.3V Vishay-Dale 594D337X06R3D2T 330F, 6.3V Vishay-Dale 594D337X06R3D2T 330F, 6.3V Vishay-Dale 594D337X06R3D2T
3.3V
2.4A
3.01k
1.78k
8V-26V
2.5V
2.35A
3.01k
2.94k
7V-23V
1.8V
2.0A
3.01k
6.49k
6V-16V
*
Maximum output current at minimum input voltage. See SOA curves for maximum output current vs. input voltage.
Table 2. Recommended Components for Common Ouput Voltages
JP3 J1 VIN (34V transient)
D2*** B340 J2 VOUT 2A
U1 MIC4685BR
2
IN
SW BS
6
L1 39H C3 0.33F 50V
C1 33F 20V J3 GND
ON OFF
C2 0.1F 50V
1
5
EN GND
4, Tab
FB
3
R1 3.01k R2 6.49k
1
C4* optional R3 2.94k JP1b 2.5V
5
D1 B340A
R4 1.78k JP1c 3.3V
7
R5 976 JP1d 5.0V
C5 330F 6.3V
C6**
C7 0.1F 50V J4 GND
JP1a 1.8V
3
2
4
6
8
*
C4 can be used to provide additional stability and improved transient response. Note: optimized for 5VOUT ** C6 Optional *** D2 is not used for standard configuration and JP3 is open.
Figure 4. Evaluation Board Schematic Diagram
May 2002
13
MIC4685
MIC4685
Micrel
Printed Circuit Board
Figure 5a. Top Silk Screen
Figure 5b. Bottom Silk Screen
Figure 5c. Top Side Copper
Figure 5d. Bottom Side Copper
Abbreviated Bill of Material (Critical Components)
Reference C1 C2, C7 C3 C4* C5 D1 D2 L1 U1
1 2 3 4 5
Part Number 594D336X0035R2T VJ0805Y104KXAAB GRM426X7R334K50 Optional 594D337X06R3D2T B340A B340A MBRX120 CDRH127-390MC MIC4685BR
Manufacturer Vishay Sprague1
Description 33F 35V 0.1F 50V 0.33F, 50V ceramic capacitor 1800pF, 50V ceramic
Qty 1 2
Vitramon Murata
(1) 1 1 1 1 1
Vishay Diode
Sprague1
330F, 6.3V, tantalum Schottky 3A 40V Schottky 3A 40V Schottky 1A 22V 39H 3A 200kHz SPAK buck regulator
Inc2
Diode Inc2 Micro Commercial Component5 Sumida3 Micrel Semiconductor4
Vishay Sprague, Inc., tel: 207-490-7256, http://www.vishay.com Diodes Inc, tel: 805-446-4800, http://www.diodes.com Sumida, tel: 408-982-9960, http://www.sumida.com Micrel, tel: 408-944-0800, http://www.micrel.com Micro Commercial Component, tel: 818-701-4933, http://www.mccsemi.com
MIC4685
14
May 2002
MIC4685
Micrel
Package Information
0.375 (9.52) 0.365 (9.27) 0.360 (9.14) 0.350 (8.89) 0.050 (1.27) 0.030 (0.76) 0.256 BSC (6.50 BSC) DIMENSIONS: INCH (MM)
0.080 (2.03) 0.070 (1.78) 0.010 BSC (0.25 BSC)
0.320 (8.13) 0.310 (7.87)
0.316 BSC (8.03 BSC) 0.420 (10.67) 0.410 (10.41)
0.045 (1.14) 0.035 (0.89)
0.050 BSC (1.27 BSC)
0.031 (0.79) 0.025 (0.63)
0.005 (0.13) 0.001 (0.03)
0.010 BSC (0.25 BSC)
6 0 SCALE 20:1
SPAK-07L (R)
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
USA
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
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) 2002 Micrel Incorporated
May 2002
15
MIC4685

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