MIC4684 Micrel, Inc. MIC4684 2A High-Efficiency SuperSwitcher™ Buck Regulator General Description Features 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 60°C 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 –40°C to +125°C. • • • • • • • • • • 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 Applications • • • • • • Simple high-efficiency step-down regulator 5V to 3.3V/1.7A converter (60°C ambient) 12V to 1.8V/2A converter (60°C ambient) On-card switching regulator Dual-output ±5V converter Battery charger Ordering Information Part Number Standard Voltage Junction Temp. Range Package Adj -40°C to +125°C SOP-8 Pb-Free MIC4684BM MIC4684YM Typical Application CIN 33µF 35V MIC4684BM 3 VIN BS 4 8 EN SW 1 FB 5 GND 2, 6, 7 CBS 0.33µF/50V 68µH 3A 40V VOUT 2.5V/1.5A R1 3.01k R2 3.01k 100 330µF 6.3V EFFICIENCY (%) VIN 6.5V to 25V Adjustable Buck Converter Efficiency vs. Output Current VOUT = 3.3V 80 60 VOUT = 1.8V VOUT = 2.5V 40 20 0 0 VIN = 5.0V 0.5 1 1.5 OUTPUT CURRENT (A) 2 Efficiency vs. Output Current 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 January 2010 1 M9999-012610 Micrel, Inc. MIC4684 Pin Configuration SW 1 8 EN GND 2 7 GND VIN 3 6 GND BS 4 5 FB 8-Pin SOP (M) Pin Description Pin Number Pin Name 1 SW 2, 6, 7 GND Pin Function Switch (Output): Emitter of NPN output switch. Connect to external storage inductor and Shottky diode. Ground 3 4 BS Booststrap Voltage Node (External Component): Connect to external boost capacitor. 5 FB 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. 8 EN Enable (Input): Logic high = enable; logic low = shutdown IN Supply (Input): Unregulated +4V to 30V supply voltage (34V transient) 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 150µA. 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. 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. January 2010 2 M9999-012610 MIC4684 Micrel, Inc. Absolute Maximum Ratings (Note 1) Operating Ratings (Note 2) 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)......................... –65°C to +150°C ESD Rating................................................................ Note 3 Supply Voltage (VIN) Note 4............................. +4V to +30V Ambient Temperature (TA)........................... –40°C to +85°C Junction Temperature (TJ)......................... –40°C to +125°C Package Thermal Resistance θJA, Note 5........................................................... 75°C/W θJC, Note 5........................................................... 25°C/W Electrical Characteristics VIN = VEN = 12V, VOUT = 5V; IOUT = 500mA; TA = 25°C, unless otherwise noted. Bold values indicate –40°C ≤ TJ ≤ +125°C. Parameter Condition Feedback Voltage (±2%) (±3%) Min 8V ≤ VIN ≤ 30V, 0.1A ≤ ILOAD ≤ 1A, VOUT = 5V Max Units 1.210 1.235 1.198 Typ 1.260 1.272 V V 1.186 1.235 1.173 1.284 1.297 V V Feedback Bias Current 50 nA VFB = 1.0V 94 % 5 500 µA VIN = 30V, VEN = 0V, VSW = –1V 1.4 20 mA 6 12 VFB = 1.5V, VSW = 0V 250 380 5.5 6.2 VFB = 0V 30 50 120 kHz 200 225 kHz Maximum Duty Cycle Output Leakage Current Quiescent Current Bootstrap Drive Current Bootstrap Voltage Frequency Fold Back VIN = 30V, VEN = 0V, VSW = 0V VFB = 1.5V IBS = 10mA, VFB = 1.5V, VSW = 0V Oscillator Frequency Saturation Voltage Short Circuit Current Limit Shutdown Current Enable Input Logic Level 180 IOUT = 1A 0.59 VEN = 0V 150 VFB = 0V, See Test Circuit 2.2 regulator on 2 regulator off 0.8 Enable Pin Input Current VEN = 0V (regulator off) 50 VEN = 12V (regulator on) –1 Thermal Shutdown @ TJ 16 mA mA V V A µA V V µA –0.83 mA 160 °C Note 1. Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. Devices are ESD sensitive. Handling precautions recommended. Note 4. 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. Note 5. Measured on 1” square of 1 oz. copper FR4 printed circuit board connected to the device ground leads. January 2010 3 M9999-012610 Micrel, Inc. MIC4684 Test Circuit Device Under Test +12V 3 VIN SW 1 8 EN BS 4 I FB GND SOP-8 68µH 2,6,7 5 Current Limit Test Circuit Shutdown Input Behavior ON OFF GUARANTEED OFF 0V TYPICAL OFF 0.8V 1.25V 2V 1.4V GUARANTEED ON TYPICAL ON VIN(max) Enable Hysteresis January 2010 4 M9999-012610 MIC4684 Micrel, Inc. Typical Characteristics (TA = 25°C unless otherwise noted) 3.3VOUT Efficiency without 100 100 VIN = 24V 65 60 55 VOUT = 5V 50 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 OUTPUT CURRENT (A) BOOTSTRAP VOLTAGE (V) VIN = 12V 0.5 1 1.5 2 2.5 OUTPUT CURRENT (A) Minimum Duty Cycle vs. Input Voltage VIN = 12V 10.8 VOUT = 5V VFB = 1.3V 10.7 10.6 10.5 10.4 10.3 0 INPUT CURRENT (µA) 200 180 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 4 3 2 120 100 80 60 40 20 VEN = 0V 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) January 2010 VIN = 12V VFB = 1.5V 1 5 10 15 20 25 INPUT VOLTAGE (V) 30 Reference Voltage vs. Input Voltage 1.255 1.250 VOUT = 1.8V VIN = 5.0V 0.5 1 1.5 OUTPUT CURRENT (A) 2 Bootstrap Drive Current vs. Input Voltage 300 250 200 150 100 VIN = 12V VFB = 1.5V 50 0 0 2 4 6 8 10 12 14 16 18 20 INPUT VOLTAGE (V) 6.3 Quiescent Current vs. Input Voltage 6.1 1.240 1.235 VIN = 12V VOUT = VREF IOUT = 500mA 1.230 1.225 0 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 5.8 5.7 0 51.5 600 595 590 585 580 IOUT = 1A VOUT = 5V 575 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 5 6 5.9 Saturation Voltage vs. Input Voltage 605 570 0 65 60 6.2 1.245 Shutdown Current vs. Input Voltage 160 140 0 0 5 VOUT = 2.5V 75 70 350 6 0 0 3 REFERENCE VOLTAGE (V) DUTY CYCLE (%) 10.9 3.3VOUT 2.5VOUT 1.8VOUT 85 80 55 50 0 Bootstrap Voltage vs. Input Voltage 7 SATURATION VOLTAGE (mV) EFFICIENCY (%) 80 70 60 50 40 30 20 10 0 0 5VOUT VIN = 24V 55 VOUT = 3.3V 50 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 OUTPUT CURRENT (A) Efficiency vs. Output Current with Feed Forward Diode 100 90 VIN = 12V BOOTSTRAP CURRENT (mA) 65 60 75 70 INPUT CURRENT (mA) 75 70 5VIN Efficiency with Feed Forward Diode 95 V = 3.3V 90 OUT FREQUENCY (kHz) VIN = 12V 100 95 90 V = 8V IN 85 80 EFFICIECNY (%) EFFICIECNY (%) 95 VIN = 8V 90 85 80 Feed Forward Diode EFFICIENCY (%) 5VOUT Efficiency without Feed Forward Diode VEN= 5V 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) Foldback Frequency vs. Input Voltage 51 50.5 50 49.5 49 48.5 0 VFB = 0V 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) M9999-012610 Micrel, Inc. OUTPUT VOLTAGE (V) 1.209 1.208 6 1.207 1.206 1.205 1.204 1.203 VIN = 12V 1.202 VOUT =V FB 1.201 IOUT = 100mA 3 2 1 IOUT = 500mA 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) January 2010 OFF 0 1.2 1.18 1.16 1.14 1.12 1.1 1.08 1.06 1.04 1.02 1 0 50 100 150 TEMPERATURE (°C) 200 5.018 5.016 Load Regulation VIN = 12V 5.014 5.012 5.010 5.008 5.006 5.004 5.002 5.000 0 0.2 0.4 0.6 0.8 1 1.2 1.4 OUTPUT CURRENT (A) Enable Threshold vs. Temperature Upper Threshold Lower Threshold VIN = 12V VOUT = 5V IOUT = 100mA -60 -40 -20 0 20 40 60 80 100 120 140 OUTPUT VOLTAGE (V) 5.06 5.05 5.04 5.03 5.02 5.01 5 4.99 4.98 0 THRESHOLD TRIP POINTS Line Regulation ON 4 TEMPERATURE (°C) 5.08 5.07 5.020 5 -1 -50 -60 -40 -20 0 20 40 60 80 100 120 140 1.200 Shutdown Hysteresis vs. Temperature OUTPUT VOLTAGE (V) Feedback Voltage vs. Temperature 1.210 FEEDBACK VOLTAGE (V) MIC4684 TEMPERATURE (°C) 6 M9999-012610 Micrel, Inc. 2.5 Typical 5VOUT SOA with Standard Configuration 2 1.5 1 VOUT = 5V TA = 60°C TJ = 125°C 0.5 0 0 5 10 15 20 25 30 INPUT VOLTAGE (V) 1 VOUT = 2.5V TA = 60°C TJ = 125°C 10 15 5 INPUT VOLTAGE (V) 0.5 VOUT = 3.3V TA = 60°C TJ = 125°C 10 15 5 INPUT VOLTAGE (V) 20 Typical 1.8VOUT SOA with Feed Forward Diode 2 1.5 1 0.5 0 0 20 SOA measured on the MIC4684 Evaluation Board. January 2010 1 2.5 OUTPUT CURRENT (A) OUTPUT CURRENT (A) Typical 2.5VOUT SOA with Feed Forward Diode 1.5 0 0 1.5 SOA Measured on the MIC4684 Evaluation Board. 2 0.5 2 0 0 35 SOA Measured on the MIC4684 Evaluation Board. 2.5 Typical 3.3VOUT SOA with Feed Forward Diode 2.5 TA = 25°C OUTPUT CURRENT (A) CONTINUOUS OUTPUT CURRENT (A) MIC4684 VOUT = 1.8V TA = 60°C TJ = 125°C 10 15 5 INPUT VOLTAGE (V) 20 SOA measured on the MIC4684 Evaluation Board. 7 M9999-012610 Micrel, Inc. MIC4684 Functional Characteristics Load Transient VOUT (100mV/div.) Normal Operation 200kHz VIN = 12V VOUT = 5V IOUT = 1.0A to 0.1A Short Circuit Operation 5.1V 5V 1A IOUT (500mA/div.) VSW (SHORTED) 12V IN, 0V OUT VSW (NORMAL) 12V IN, 5V/1A OUT Switching Frequency Foldback 0A 70kHz TIME (100ms/div.) TIME 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. January 2010 8 M9999-012610 MIC4684 Micrel, Inc. Block Diagrams VIN IN Bootstrap Charger Enable Internal Regulator 200kHz Oscillator Thermal Shutdown VOUT = VREF R1 = R2 Current Limit R1 + 1) ( R2 (VVOUT - 1) REF VREF = 1.235V Comparator Driver VOUT SW COUT Reset FB Error Amp R1 R2 1.235V Bandgap Reference MIC4684 Adjustable Regulator Functional Description 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. 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 150µA 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 January 2010 9 M9999-012610 Micrel, Inc. MIC4684 Applications Information 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 25°C/W for a power SOP-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 75°C/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. 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 V OUT = 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 Switchin g 40 MAX. INPUT VOLTAGE (V) 35 30 SOP-8 25 20 15 10 5 0 0 1 2 3 4 5 OUTPUT VOLTAGE (V) θJA 6 θJC θCA AM Figure 1. Minimum Pulse Width Characteristic Thermal Considerations The MIC4684 SuperSwitcher™ 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 SuperSwitcher™ 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 (θJA) of the design (package and ground plane). NT 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 60°C maximum ambient temperature, what is the junction temperature? Referring to the “Typical Characteristics: 5V Output Efficiency” graph, read the efficiency (η) for 1A output current at VIN = 12V or perform you own measurement. η = 84% The efficiency is used to determine how much of the output power (POUT) is dissipated in the regulator circuit (PD). P PD = OUT − POUT η 5W PD = − 5W 0.84 January 2010 ground plane heat sink area BIE 10 PD = 0.95W M9999-012610 MIC4684 Micrel, Inc. 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 × 0.95W PD(IC) = 0.76W Calculate the worst-case junction temperature: TJ = PD(IC) θJC + (TC – TA) + TA(max) where: TJ = MIC4684 junction temperature PD(IC) = MIC4684 power dissipation θJC = junction-to-case thermal resistance. 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. 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. TA(max) = maximum ambient operating temperature for the specific design. Calculating the maximum junction temperature given a maximum ambient temperature of 60°C: TJ = 0.76 × 25°C/W + (41°C – 25°C) + 60°C TJ = 95°C VIN +4V to +30V (34V transient) 3 8 CIN Power SOP-8 MIC4684BM IN BS EN SW FB GND 2 6 4 L1 1 68µH 5 VOUT COUT D1 7 R1 R2 Load The θJC for the MIC4684’s power-SOP-8 is approximately 25°C/W. TC = “pin” temperature measurement taken at the entry point of pins 2, 6 or 7 TA = ambient temperature GND Figure 5. Critical Traces for Layout January 2010 11 M9999-012610 Micrel, Inc. MIC4684 Recommended Components for a Given Output Voltage (Feed-Forward Configuration) VIN = 4V to 16V (in feed-forward configuration) VOUT IOUT R1 R2 VIN CIN D1 D2 L1 COUT 5.0V 1.6A 3.01k 976kΩ 6.5V–16V 47µF, 20V Vishay-Dale 595D476X0020D2T 2A, 30V 1A, 20V 27µH Schottky Schottky Sumida SS23 MBRX120 CDH74-270MC 120µF, 6.3V Vishay-Dale 594D127X06R3C2T 3.3V 1.7A 3.01k 1.78k 4.85V–16V 47µF, 20V Vishay-Dale 595D476X0020D2T 2A, 30V 1A, 20V 27µH Schottky Schottky Sumida SS23 MBRX120 CDH74-270MC 220µF, 6.3V Vishay-Dale 594D227X06R3C2T 2.5V 1.8A 3.01k 2.94k 4.5V–16V 47µF, 20V Vishay-Dale Schottky 595D476X0020D2T 2A, 30V 1A, 20V 27µH Schottky Sumida Vishay-Dale SS23 MBRX120 CDH74-270MC 330µF, 6.3V 1.8V 2A 3.01k 6.49k 4.2V–16V 47µF, 20V Vishay-Dale 595D476X0020D2T 2A, 30V 1A, 20V 27µH Schottky Schottky Sumida SS23 MBRX120 CDH74-270MC 330µF, 6.3V Vishay-Dale 594D337X06R3D2T 594D337X06R3D2T 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 C1 15µF 35V J3 GND 3 ON OFF C2 0.1µF 50V 8 U1 MIC4684BM VIN SW EN BS 4 FB 5 GND SOP-8 1 2, 6, 7 J2 VOUT 2A L1 47µH C6 0.33µF 50V D1 B340A or SS34 R1 3.01k R2 6.49k 1 2 3 JP1a 1.8V 4 C3* optional R3 2.94k 5 JP1b 2.5V 6 R4 1.78k 7 JP1c 3.3V 8 R5 976Ω JP1d 5.0V C4 330µF 6.3V C5 0.1µF 50V J4 GND * 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 January 2010 12 M9999-012610 MIC4684 Micrel, Inc. 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 Part Number Manufacturer Description C1 594D156X0035D2T Vishay Sprague(1) 15µF 35V 1 2 C2, C5 VJ0805Y104KXAAB Vitramon 0.1µF 50V C6 GRM426X7R334K50 Murata 0.33µF, 50V ceramic capacitor C3 Optional C4 594D337X06R3D2T Vishay Sprague(2) Inc(3) D1 B340A Diode D2 MBRX120 Micro Com. Components(5) L1 CDRH104R-470MC Sumida(4) U1 MIC4684BM Micrel, Inc.(6) Qty 1800pF, 50V ceramic (1) 330µF, 6.3V, tantalum 1 Schottky 3A, 40V 1 Schottky 1A, 20V 1 47µH, 2.1A ISAT 1 1A 200kHz power-SO-8 buck regulator 1 Notes: 1. Vishay Dale, Inc., tel: 1 402-644-4218, http://www.vishay.com 2. Vishay Sprague, Inc., tel: 1 207-490-7256, http://www.vishay.com 3. Diodes Inc, tel: (805) 446-4800, http://www.diodes.com 4. Sumida, tel: (408) 982-9960, http://www.sumida.com 5. Micro Commercial Components, tel: (800) 346-3371 6. Micrel, Inc. tel: (408) 944-0800, http://www.micrel.com January 2010 13 M9999-012610 Micrel, Inc. MIC4684 Recommended Components for a Given Output Voltage (Standard Configuration) VIN = 4V to 30V VOUT IOUT R1 R2 VIN CIN D1 L1 COUT 5.0V 1.7A 3.01k 976kΩ 8V–30V 33µF, 35V Vishay-Dale 595D336X0035R2T 3A, 40V Schotty SS34 68µH Sumida CDRH104R-680MC 120µF, 6.3V Vishay-Dale 594D127X06R3C2T 3.3V 1.5A 3.01k 1.78k 7V–28V 33µF, 35V Vishay-Dale 595D336X0035R2T 3A, 40V Schotty SS34 68µH Sumida CDRH104R-680MC 220µF, 6.3V Vishay-Dale 594D227X06R3C2T 2.5V 1.5A 3.01k 2.94k 6.5V–23V 33µF, 35V Vishay-Dale 595D336X0035R2T 3A, 40V Schotty SS334 68µH Sumida CDRH104R-680MC 330µF, 6.3V Vishay-Dale 594D337X06R3D2T 1.8V 1.5A 3.01k 6.49k 6V–17V 47µF, 25V Vishay-Dale 595D476X0025D2T 3A, 40V Schotty SS334 68µH Sumida CDRH104R-680MC 330µF, 6.3V Vishay-Dale 594D337X06R3D2T Table 2. Recommended Components for Common Ouput Voltages (VIN = 4V to 30V) J1 VIN 4V to +30V (34V transient) C1 15µF 35V J3 GND L1 3 ON OFF C2 0.1µF 50V 8 U1 MIC4684BM VIN SW EN BS 4 FB 5 GND SOP-8 1 2, 6, 7 J2 VOUT 2A 47µH C6 0.33µF 50V D1 B340A or SS34 R1 3.01k R2 6.49k 1 2 3 JP1a 1.8V 4 C3* optional R3 2.94k 5 JP1b 2.5V 6 R4 1.78k 7 JP1c 3.3V 8 R5 976Ω JP1d 5.0V C4 330µF 6.3V C5 0.1µF 50V J4 GND * C3 can be used to provide additional stability and improved transient response. Note: optimized for 5VOUT Figure 8. 4V - 30V Input Evaluation Board Schematic Diagram January 2010 14 M9999-012610 MIC4684 Micrel, Inc. Printed Circuit Board General Purpose Evaluation Board (VIN = 4V to 30V) Figure 9a. Bottom Side Copper Figure 9b. Top Side Copper Figure 9c. Bottom Side Silk Screen Figure 9d. Top Side Silk Screen Abbreviated Bill of Material (Critical Components) Reference Part Number Manufacturer Description Sprague(1) C1 594D156X0035D2T Vishay C2, C5 VJ0805Y104KXAAB Vitramon C6 GRM426X7R334K50 Murata C3 Optional 594D337X06R3D2T Vishay D1 B340A Diode Inc(3) L1 CDRH104R-470MC Sumida(4) U1 MIC4684BM Micrel, Inc.(5) 15µF 35V 1 0.1µF 50V 2 0.33µF, 50V ceramic capacitor Sprague(2) C4 Qty 1800pF, 50V ceramic (1) 330µF, 6.3V, tantalum 1 Schottky 3A 40V 1 47µH, 2.1A ISAT 1 1A 200kHz power-SO-8 buck regulator 1 Notes: 1. Vishay Dale, Inc., tel: 1 402-644-4218, http://www.vishay.com 2. Vishay Sprague, Inc., tel: 1 207-490-7256, http://www.vishay.com 3. Diodes Inc, tel: (805) 446-4800, http://www.diodes.com 4. Sumida, tel: (408) 982-9960, http://www.sumida.com 5. Micrel, Inc. tel: (408) 944-0800, http://www.micrel.com January 2010 15 M9999-012610 Micrel, Inc. MIC4684 Package Information 8-Lead SOP (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 This 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. © 2001 Micrel Incorporated January 2010 16 M9999-012610