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MIC4684
Micrel
MIC4684
2A High-Efficiency SuperSwitcherTM Buck Regulator
Final Information
General Description
The MIC4684 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 MIC4684 achieves 2A of continuous current in an 8-lead SO (small outline) package at 60C ambient temperature. 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, no external heat sink is required. The MIC4684, housed in an SO-8, can replace larger TO-220 and TO-263 packages in many applications. The MIC4684 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 MIC4684 is available in an 8-lead SO package with a junction temperature range of -40C to +125C.
Features
* * * * * * * * * * * * * * * * SO-8 package with 2A continuous output current Over 85% efficiency Fixed 200kHz PWM operation Wide 4V to 30V input voltage range 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 Simple high-efficiency step-down regulator 5V to 3.3V/1.7A converter (60C ambient) 12V to 1.8V/2A converter (60C ambient) On-card switching regulator Dual-output 5V converter Battery charger
Applications
Ordering Information
Part Number MIC4684BM Voltage Adj Junction Temperature Range -40C to +125C Package SOP-8
Typical Application
VIN 6.5V to 25V
3 8
MIC4684BM VIN BS EN SW FB GND
2, 6, 7
4 1
CBS 0.33F/50V 68H R1 3.01k R2 3.01k
VOUT 2.5V/1.5A 330F 6.3V
CIN 33F 35V
5
Efficiency vs. Output Current
100 VOUT = 3.3V 80
3A 40V
EFFICIENCY (%)
60 40 20 0
Adjustable Buck Converter
1A, 20V Feed forward diode VIN 5V 10%
VOUT = 1.8V
VOUT = 2.5V
VIN = 5.0V 0.5 1 1.5 OUTPUT CURRENT (A) 2
3 8
MIC4684BM VIN BS EN SW FB GND
2, 6, 7
4 1
CBS 0.33F/50V 47H
0
VOUT 3.3V/1.7A 220F 10V
CIN 68F 10V
5
Efficiency vs. Output Current
2A 20V
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
July 2001
1
MIC4684
MIC4684
Micrel
Pin Configuration
SW GND VIN BS 1 2 3 4 8 7 6 5 EN GND GND FB
8-Pin SOP (M)
Pin Description
Pin Number 1 2, 6, 7 3 4 5 Pin Name SW GND IN BS FB Pin Function Switch (Output): Emitter of NPN output switch. Connect to external storage inductor and Shottky diode. Ground Supply (Input): Unregulated +4V to 30V supply voltage (34V transient) Booststrap Voltage Node (External Component): Connect to external boost capacitor. Feedback (Input): Outback voltage feedback to regulator. Connect to output of supply for fixed versions. Connect to 1.23V tap of resistive divider for adjustable versions. Enable (Input): Logic high = enable; logic low = shutdown
8
EN
Detailed Pin Description
Switch (SW, pin 1) 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, pins 2,6,7) 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 its necessary to place the input capacitor ground lead as close as possible to the switching regulators ground pin. Input Voltage (VIN, pin 3) 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 4) The bootstrap pin in conjunction with the external bootstrap capacitor provides a bias voltage higher than the input voltage to the MIC4684'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 5) The feedback pin is tied to the inverting side of a GM error amplifier. The noninverting side is tied to a 1.235V bandgap reference. Fixed voltage versions have an internal voltage divider from the feedback pin. Adjustable versions require an external resistor voltage divider from the output to ground, with the center tied to the feedback pin. Enable (EN, pin 8) 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. 2 July 2001
MIC4684
MIC4684
Micrel
Absolute Maximum Ratings (Note 1)
Supply Voltage (VIN), Note 3 ...................................... +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
Operating Ratings (Note 2)
Supply Voltage (VIN) Note 4 ........................... +4V to +30V Ambient Temperature (TA) ......................... -40C to +85C Junction Temperature (TJ) ....................... -40C to +125C Package Thermal Resistance JA, Note 5 .......................................................... 75C/W JC, Note 5 .......................................................... 25C/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 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. Note 5. 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. 2.5V of headroom is required between VIN and VOUT. The headroom can be reduced by implementing a feed-forward diode a seen on the 5V to 3.3V circuit on page 1. Measured on 1" square of 1 oz. copper FR4 printed circuit board connected to the device ground leads.
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 50 200 0.59 120 225
kHz kHz V A A V
2.2 150 2 0.8 16 -1 -0.83 160 50
V A mA C
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MIC4684
MIC4684
Micrel
Test Circuit
+12V
3
Device Under Test 1 VIN SW
4
68H
8
EN GND FB
5 2,6,7
BS
I
SOP-8
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
MIC4684
4
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Micrel
Typical Characteristics
(TA = 25C unless otherwise noted)
5VOUT Efficiency without Feed Forward Diode 100
95 VIN = 8V 90 EFFICIECNY (%)
EFFICIECNY (%)
3.3VOUT Efficiency without
100
Feed Forward Diode
5VIN Efficiency with Feed Forward Diode 100
95 V = 3.3V 90 OUT
EFFICIENCY (%)
85 80 75 70 65 60 VIN = 24V
VIN = 12V
95 90 V = 8V IN 85 80 75 70 65 60 VIN = 12V VIN = 24V
85 80 75 70 65 60 55 50 0 VOUT = 1.8V
VOUT = 2.5V
55 VOUT = 5V 50 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 OUTPUT CURRENT (A)
55 VOUT = 3.3V 50 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 OUTPUT CURRENT (A)
V
IN
= 5.0V 2
0.5 1 1.5 OUTPUT CURRENT (A)
Efficiency vs. Output Current with Feed Forward Diode
100 5VOUT 3.3VOUT 2.5VOUT 1.8VOUT
BOOTSTRAP VOLTAGE (V)
Bootstrap Voltage vs. Input Voltage
7 6 5 4 3 2 1 0 0 5 VIN = 12V VFB = 1.5V 10 15 20 25 INPUT VOLTAGE (V) 30
BOOTSTRAP CURRENT (mA)
Bootstrap Drive Current vs. Input Voltage
350 300 250 200 150 100 50 VIN = 12V VFB = 1.5V
90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0
VIN = 12V 0.5 1 1.5 2 2.5 OUTPUT CURRENT (A) 3
0 0 2 4 6 8 10 12 14 16 18 20 INPUT VOLTAGE (V)
Minimum Duty Cycle vs. Input Voltage
10.9 REFERENCE VOLTAGE (V) VIN = 12V 10.8 VOUT = 5V VFB = 1.3V 10.7 10.6 10.5 10.4 10.3 0 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 1.255 1.250 1.245 1.240 1.235 1.230 1.225 0 5
Reference Voltage vs. Input Voltage
6.3 INPUT CURRENT (mA) 6.2 6.1 6 5.9 5.8
Quiescent Current vs. Input Voltage
DUTY CYCLE (%)
VIN = 12V VOUT = VREF IOUT = 500mA 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
VEN= 5V 5.7 0 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
Shutdown Current vs. Input Voltage
200 605 SATURATION VOLTAGE (mV) 600 595 590 585 580 575 570 0 5
Saturation Voltage vs. Input Voltage
51.5 51 FREQUENCY (kHz) 50.5 50 49.5 49 48.5 0
Foldback Frequency vs. Input Voltage
INPUT CURRENT (A)
180 160 140 120 100 80 60 40 20 0 0 VEN = 0V 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
IOUT = 1A VOUT = 5V 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
VFB = 0V 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
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MIC4684
MIC4684
Micrel
Feedback Voltage vs. Temperature
1.210 FEEDBACK VOLTAGE (V)
OUTPUT VOLTAGE (V)
Shutdown Hysteresis vs. Temperature
6
OUTPUT VOLTAGE (V)
Load Regulation
5.020 5.018 5.016 5.014 5.012 5.010 5.008 5.006 5.004 5.002 5.000 0 VIN = 12V
1.209 1.208 1.207 1.206 1.205 1.204 1.203 VIN = 12V 1.202 VOUT = VFB 1.201 IOUT = 100mA 20 40 60 80 100 -60 -40 -20 0 120 140 1.200
5 4 3 2 1 0 -1 -50 0 50 100 150 TEMPERATURE (C) 200 OFF ON
TEMPERATURE (C)
0.2 0.4 0.6 0.8 1 1.2 1.4 OUTPUT CURRENT (A)
Line Regulation
5.08
THRESHOLD TRIP POINTS
Enable Threshold vs. Temperature
1.2 1.18 1.16 1.14 1.12 1.1 1.08 1.06 1.04 1.02 1 Upper Threshold
OUTPUT VOLTAGE (V)
5.07 5.06 5.05 5.04 5.03 5.02 5.01 5 4.99 4.98 0 IOUT = 500mA 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
Lower Threshold
VIN = 12V VOUT = 5V IOUT = 100mA
20 40 -20 0 60 80 100 120
-60 -40
TEMPERATURE (C)
MIC4684
6
140
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MIC4684
Micrel
CONTINUOUS OUTPUT CURRENT (A)
5VOUT SOA with Standard Configuration
2.5 OUTPUT CURRENT (A) 2 1.5 1 0.5 0 0 VOUT = 5V TA = 60C TJ = 125C 5 10 15 20 25 30 INPUT VOLTAGE (V) 35 TA = 25C
3.3V
2.5 2 1.5 1 0.5 0 0
OUT
SOA with Feed
Forward Diode
VOUT = 3.3V TA = 60C TJ = 125C 5 10 15 INPUT VOLTAGE (V) 20
SOA Measured on the MIC4684 Evaluation Board.
SOA Measured on the MIC4684 Evaluation Board.
Note 1. With feed-forward diode implementation as seen in 5V to 3.3V circuit on page 1.
2.5VOUT SOA with Feed Forward Diode 2.5
OUTPUT CURRENT (A) 2 1.5 1 0.5 0 0 VOUT = 2.5V TA = 60C TJ = 125C 5 10 15 INPUT VOLTAGE (V) 20 OUTPUT CURRENT (A)
1.8VOUT SOA with Feed Forward Diode 2.5
2 1.5 1 0.5 0 0 VOUT = 1.8V TA = 60C TJ = 125C 5 10 15 INPUT VOLTAGE (V) 20
SOA measured on the MIC4684 Evaluation Board.
SOA measured on the MIC4684 Evaluation Board.
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MIC4684
MIC4684
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
IOUT (500mA/div.)
1A
0A
70kHz
TIME
TIME (100ms/div.)
Frequency Foldback The MIC4684 folds the switching frequency back during a hard short circuit condition to reduce the energy per cycle and protect the device.
MIC4684
8
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MIC4684
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 MIC4684 1.235V Bandgap Reference R2 COUT VOUT
Adjustable Regulator
Functional Description
The MIC4684 is a variable duty cycle switch-mode regulator with an internal power switch. Refer to the above block diagram. Supply Voltage The MIC4684 operates from a +4V to +30V (34V transient) unregulated input. Highest efficiency operation is from a supply voltage around +12V. See the efficiency curves 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 Fixed-voltage versions of the regulator have an internal resistive divider from the feedback (FB) pin. Connect FB directly to the output voltage. Adjustable versions require an external resistive voltage divider 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 MIC4684 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. 9 MIC4684
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MIC4684
Micrel
JA = (JC + CA) where: JC = junction-to-case thermal resistance CA = case-to-ambient thermal resistance JC is a relatively constant 25C/W for a power SOP-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 75C/W, but will vary depending on the size of the ground plane to which the power SOP-8 is attached. Determining Ground-Plane Heat-Sink Area Make sure that MIC4684 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 MIC4684 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. Examining JA in more detail:
Applications Information
Adjustable Regulators Adjustable regulators require a 1.23V 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
Minimum Pulse Width The minimum duty cycle of the MIC4684 is approximately 10%. See Minimum Duty Cycle Graph. If this input-to-output voltage characteristic is exceeded, the MIC4684 will skip cycles to maintain a regulated VOUT.
Max. VIN for a Given VOUT for Constant-Frequency Switching
40 35 30 25 20 15 10 5 0 0 1 2 3 4 5 OUTPUT VOLTAGE (V) 6
MAX. INPUT VOLTAGE (V)
SOP-8
JA JC CA
AM BIE
ground plane heat sink area
NT
Figure 1. Minimum Pulse Width Characteristic Thermal Considerations The MIC4684 SuperSwitcherTM features the power-SOP-8. This package has a standard 8-lead small-outline package profile, but with much higher power dissipation than a standard SOP-8. Micrel's MIC4684 SuperSwitcherTM family are the first dc-to-dc converters to take full advantage of this package. The reason that the power SOP-8 has higher power dissipation (lower thermal resistance) is that pins 2, 6, and 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 MIC4684 design is the junction-to-ambient thermal resistance (JA) of the design (package and ground plane).
printed circuit board
Figure 2. Power SOP-8 Cross Section When designing with the MIC4684, 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 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 1A output current at VIN = 12V or perform you own measurement. = 84% The efficiency is used to determine how much of the output power (POUT) is dissipated in the regulator circuit (PD). PD = PD = POUT - POUT
5W - 5W 0.84 PD = 0.95W MIC4684 10 July 2001
MIC4684
A worst-case rule of thumb is to assume that 80% of the total output power dissipation is in the MIC4684 (PD(IC)) and 20% is in the diode-inductor-capacitor circuit. PD(IC) = 0.8 PD PD(IC) = 0.8 x 0.95W PD(IC) = 0.76W Calculate the worst-case junction temperature: TJ = PD(IC) JC + (TC - TA) + TA(max) where: TJ = MIC4684 junction temperature PD(IC) = MIC4684 power dissipation JC = junction-to-case thermal resistance. The JC for the MIC4684's power-SOP-8 is approximately 25C/W. TC = "pin" temperature measurement taken at the entry point of pins 2, 6 or 7 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 = 0.76 x 25C/W + (41C - 25C) + 60C TJ = 95C
Micrel
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 SOA curves on pages 7 through 8. 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 1 and pins 2, 6, and 7, keep L1 away from sensitive node FB, and keep CIN close to pin 3 and pins 2, 6, and 7. 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. Feed Forward Diode The FF diode (feed forward) provides an external bias source directly to the main pass element, this reduces VSAT thus allowing the MIC4684 to be used in very low head-room applications I.E. 5VIN to 3.3VOUT.
VIN +4V to +30V (34V transient) CIN Power SOP-8
MIC4684BM
3 8
IN EN
BS SW FB GND
2 6 7
4 1
L1 68H COUT D1
VOUT R1
5
R2
GND
Figure 5. Critical Traces for Layout
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Load
MIC4684
MIC4684
Micrel
Recommended Components for a Given Output Voltage (Feed-Forward Configuration)
VIN = 4V to 16V (in feed-forward configuration)
VOUT 5.0V IOUT 1.6A R1 R2 VIN 6.5V-16V CIN 47F, 20V Vishay-Dale 595D476X0020D2T D1 D2 L1 COUT 120F, 6.3V Vishay-Dale 594D127X06R3C2T 220F, 6.3V Vishay-Dale 594D227X06R3C2T 330F, 6.3V Vishay-Dale 594D337X06R3D2T 330F, 6.3V Vishay-Dale 594D337X06R3D2T 3.01k 976k 2A, 30V 1A, 20V 27H Schottky Schottky Sumida SS23 MBRX120 CDH74-270MC 2A, 30V 1A, 20V 27H Schottky Schottky Sumida SS23 MBRX120 CDH74-270MC 2A, 30V 1A, 20V 27H Schottky Schottky Sumida SS23 MBRX120 CDH74-270MC 2A, 30V 1A, 20V 27H Schottky Schottky Sumida SS23 MBRX120 CDH74-270MC
3.3V
1.7A
3.01k
1.78k
4.85V-16V 47F, 20V Vishay-Dale 595D476X0020D2T 4.5V-16V 47F, 20V Vishay-Dale 595D476X0020D2T 47F, 20V Vishay-Dale 595D476X0020D2T
2.5V
1.8A
3.01k
2.94k
1.8V
2A
3.01k
6.49k
4.2V-16V
Note 1.
This bill of materials assumes the use of feedforward schotty diode from VIN to the bootstrap pin.
Table 1. Recommended Components for Common Ouput Voltages (VIN = 4V to 16V)
D2 MBRX120 1A/20V J1 VIN 4V to +16V C2 0.1F 50V L1 47H
1
U1 MIC4684BM
3
VIN
SW BS
J2 VOUT 2A
4
C1 15F 35V J3 GND
C6 0.33F 50V D1 B340A or SS34
ON OFF
8
EN GND
SOP-8 2, 6, 7
FB
5
R1 3.01k R2 6.49k
1
C3* optional R3 2.94k JP1b 2.5V
5
R4 1.78k JP1c 3.3V
7
R5 976 JP1d 5.0V
C4 330 F 6.3V
C5 0.1F 50V J4 GND
JP1a 1.8V
3
2
4
6
8
* C3 can be used to provide additional stability and improved transient response. Note: optimized for 5VOUT
Figure 6. 4V - 16V Input Evaluation Board Schematic Diagram
MIC4684
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MIC4684
Micrel
Printed Circuit Board
Evaluation Board Optimized for Low Input Voltage by using Feed-Forward Diode Configuration (VIN = 4V to 16V)
Figure 7a. Bottom Side Copper
Figure 7b. Top Side Copper
Figure 7c. Bottom Side Silk Screen
Figure 7d. Top Side Silk Screen
Abbreviated Bill of Material (Critical Components)
Reference C1 C2, C5 C6 C3 C4 D1 D2 L1 U1
1 2 3 4 5 6
Part Number 594D156X0035D2T VJ0805Y104KXAAB GRM426X7R334K50 Optional 594D337X06R3D2T B340A MBRX120 CDRH104R-470MC MIC4684BM
Manufacturer Vishay Sprague1
Description 15F 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
Sprague2
330F, 6.3V, tantalum Schottky 3A, 40V Schottky 1A, 20V 47H, 2.1A ISAT 1A 200kHz power-SO-8 buck regulator
Inc3
Micro Com. Components5 Sumida4 Micrel Semiconductor6
Vishay Dale, Inc., tel: 1 402-644-4218, http://www.vishay.com Vishay Sprague, Inc., tel: 1 207-490-7256, http://www.vishay.com Diodes Inc, tel: (805) 446-4800, http://www.diodes.com Sumida, tel: (408) 982-9960, http://www.sumida.com Micro Commercial Components, tel: (800) 346-3371 Micrel, tel: (408) 944-0800, http://www.micrel.com
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MIC4684
MIC4684
Micrel
Recommended Components for a Given Output Voltage (Standard Configuration)
VIN = 4V to 30V
VOUT 5.0V IOUT 1.7A R1 3.01k R2 976k VIN 8V-30V CIN 33F, 35V Vishay-Dale 595D336X0035R2T 33F, 35V Vishay-Dale 595D336X0035R2T 33F, 35V Vishay-Dale 595D336X0035R2T 47F, 25V Vishay-Dale 595D476X0025D2T D1 3A, 40V Schotty SS34 3A, 40V Schotty SS34 3A, 40V Schotty SS334 3A, 40V Schotty SS334 L1 68H Sumida CDRH104R-680MC 68H Sumida CDRH104R-680MC 68H Sumida CDRH104R-680MC 68H Sumida CDRH104R-680MC COUT 120F, 6.3V Vishay-Dale 594D127X06R3C2T 220F, 6.3V Vishay-Dale 594D227X06R3C2T 330F, 6.3V Vishay-Dale 594D337X06R3D2T 330F, 6.3V Vishay-Dale 594D337X06R3D2T
3.3V
1.5A
3.01k
1.78k
7V-28V
2.5V
1.5A
3.01k
2.94k
6.5V-23V
1.8V
1.5A
3.01k
6.49k
6V-17V
Table 2. Recommended Components for Common Ouput Voltages (VIN = 4V to 30V)
J1 VIN 4V to +30V (34V transient)
L1
3
U1 MIC4684BM VIN SW BS
47H
1
J2 VOUT 2A
C1 15F 35V J3 GND
ON OFF
C2 0.1F 50V
4
C6 0.33F 50V D1 B340A or SS34
8
EN GND
SOP-8 2, 6, 7
FB
5
R1 3.01k R2 6.49k
1
C3* optional R3 2.94k JP1b 2.5V
5
R4 1.78k JP1c 3.3V
7
R5 976 JP1d 5.0V
C4 330 F 6.3V
C5 0.1F 50V J4 GND
JP1a 1.8V
3
2
4
6
8
* C3 can be used to provide additional stability and improved transient response. Note: optimized for 5VOUT
Figure 6a. 4V - 30V Input Evaluation Board Schematic Diagram
MIC4684
14
July 2001
MIC4684
Micrel
Printed Circuit Board
General Purpose Evaluation Board (VIN = 4V to 30V)
Figure 7a. Bottom Side Copper
Figure 7b. Top Side Copper
Figure 7c. Bottom Side Silk Screen
Figure 7d. Top Side Silk Screen
Abbreviated Bill of Material (Critical Components)
Reference C1 C2, C5 C6 C3 C4 D1 L1 U1
1 2 3 4 5
Part Number 594D156X0035D2T VJ0805Y104KXAAB GRM426X7R334K50 Optional 594D337X06R3D2T B340A CDRH104R-470MC MIC4684BM
Manufacturer Vishay Sprague1 Vitramon Murata
Description 15F 35V 0.1F 50V 0.33F, 50V ceramic capacitor 1800pF, 50V ceramic
Qty 1 2
(1) 1 1 1 1
Vishay Diode
Sprague2
330F, 6.3V, tantalum Schottky 3A 40V 47H, 2.1A ISAT 1A 200kHz power-SO-8 buck regulator
Inc3
Sumida4 Micrel Semiconductor5
Vishay Dale, Inc., tel: 1 402-644-4218, http://www.vishay.com Vishay Sprague, Inc., tel: 1 207-490-7256, 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
July 2001
15
MIC4684
MIC4684
Micrel
Package Information
0.026 (0.65) MAX) PIN 1
0.157 (3.99) 0.150 (3.81)
DIMENSIONS: INCHES (MM)
0.050 (1.27) TYP
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)
0.064 (1.63) 0.045 (1.14)
0.197 (5.0) 0.189 (4.8)
0.050 (1.27) 0.016 (0.40) 0.244 (6.20) 0.228 (5.79)
8-Lead SOP (M)
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) 2001 Micrel Incorporated
MIC4684
16
July 2001

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