MIC2288 Micrel, Inc. MIC2288 1A 1.2MHz PWM Boost Converter in ×2 MLF™ Thin SOT-23 and 2× General Description Features The MIC2288 is a 1.2MHz PWM, DC/DC boost switching regulator available in low-profile Thin SOT-23 and 2mm × 2mm MLF™ package options. High power density is achieved with the MIC2288’s internal 34V/1A switch, allowing it to power large loads in a tiny footprint. The MIC2288 implements a constant frequency, 1.2MHz PWM, current mode control scheme with internal compensation that offers excellent transient response and output regulation performance. The high frequency operation saves board space by allowing small, low-profile, external components. The fixed frequency PWM topology also reduces spurious switching noise and ripple to the input power source. The MIC2288 is available in a low-profile Thin SOT-23-5 package and a 2mm × 2mm MLF™-8 leadless package. The 2mm × 2mm MLF™-8 package option has an output overvoltage protection feature. The MIC2288 has a junction temperature range of –40°C to +125°C. All support documentation can be found on Micrel’s web site at www.micrel.com. • • • • • • • • • • • • • • • 2.5V to 10V input voltage range Output voltage adjustable to 34V Over 1A switch current 1.2MHz PWM operation Stable with ceramic capacitors High-efficiency <1% line and load regulation Low input and output ripple <1µA shutdown current UVLO Output overvoltage protection (MIC2288BML) Over temperature shutdown Thin SOT-23-5 package option 2mm × 2mm leadless MLF™-8 package option –40°C to +125°C junction temperature range Applications • • • • • • Organic EL power supply TFT-LCD bias supply 12V supply for DSL applications Multi-output DC/DC converters Positive and negative output regulators SEPIC converters Typical Application L1 10µH VIN VOUT 15V 90 4 C1 2.2µF SW EN FB GND EFFICIENCY (%) 1-Cell Li Ion VIN VIN = 4.2V 85 MIC2288BD5 5 15VOUT Efficiency 1 R1 3 R2 C2 10µF 2 80 75 VIN = 3.2V 70 VIN = 3.6V 65 60 0 0.05 0.1 0.15 LOAD (A) 0.2 2mm × 2mm MLF™ Boost Regulator MLF and MicroLeadFrame are trademarks of Amkor Technology, 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 April 2005 1 M9999-042205 MIC2288 Micrel, Inc. Ordering Information Part Number Marking Code Output Voltage Overvoltage Protection Junction Temp. Range Package Lead Finish MIC2288BD5 SHAA Adjustable – –40°C to 125°C Thin SOT-23-5 Standard MIC2288YD5 SHAA Adjustable – –40°C to 125°C Thin SOT-23-5 Lead Free MIC2288BML SJA Adjustable 34V –40°C to 125°C 2×2 MLF™-8 Standard MIC2288YML SJA Adjustable 34V –40°C to 125°C 2×2 MLF™-8 Lead Free Pin Configuration FB GND SW 1 2 3 4 EN 5 VIN TSOT-23-5 (D5) OVP 1 8 PGND VIN 2 7 SW EN 3 6 FB AGND 4 5 NC EP 8-Pin MLF™ (ML) (Top View) Fused Lead Frame Pin Description Pin Number TSOT-23-5 Pin Number 2× ×2 MLF™-8 Pin Name 1 7 SW 2 GND Pin Function Switch Node (Input): Internal power Bipolar collector. Ground (Return): Ground. 3 6 FB Feedback (Input): 1.24V output voltage sense node. R1 VOUT = 1.24V 1 + R2 4 3 EN Enable (Input): Logic high enables regulator. Logic low shuts down regulator. 5 2 VIN Supply (Input): 2.5V to 10V input voltage. 1 OVP Output Overvoltage Protection (Input): Tie this pin to VOUT to clamp the output voltage to 34V maximum in fault conditions. Tie this pin to ground if OVP function is not required. 5 NC 4 AGND Analog ground. 8 PGND Power ground. EP GND M9999-042205 No Connect: No internal connection to die. Exposed backside pad. 2 April 2005 MIC2288 Micrel, Inc. Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN) ..................................................... 12V Switch Voltage (VSW) ..................................... –0.3V to 34V Enable Pin Voltage (VEN) ................................... –0.3 to VIN FB Voltage (VFB) ............................................................. 6V Switch Current (ISW) ....................................................... 2A Storage Temperature (TS) ....................... –65°C to +150°C ESD Rating(3) ................................................................ 2kV Supply Voltage (VIN) ........................................ 2.5V to 10V Junction Temperature Range (TJ) ........... –40°C to +125°C Package Thermal Impedance 2mm × 2mm MLF™-8 (θJA) ................................. 93°C/W Thin SOT-23-5 (θJA) .......................................... 256°C/W Electrical Characteristics(4) TA = 25°C, VIN = VEN = 3.6V, VOUT = 10V, IOUT = 20mA, unless otherwise noted. Bold values indicate –40°C ≤ TJ ≤ ±125°C. Symbol Parameter Condition Min VIN Supply Voltage Range 2.5 VUVLO Under Voltage Lockout 1.8 IVIN Quiescent Current VFB = 2V, (not switching) 0V(5) Typ Max Units 10 V 2.1 2.4 V 2.8 5 mA 0.1 1 µA 1.24 1.252 1.265 V V ISD Shutdown Current VEN = VFB Feedback Voltage (±1%) (±2%) (Over Temp) IFB Feedback Input Current VFB = 1.24V Line Regulation 3V ≤ VIN ≤ 5V 0.1 Load Regulation 5mA ≤ IOUT ≤ 40mA 0.2 % 90 % 1.2 A mV 1.227 1.215 –450 DMAX Maximum Duty Cycle 85 ISW Switch Current Limit VSW Switch Saturation Voltage ISW = 1A 550 ISW Switch Leakage Current VEN = 0V, VSW = 10V 0.01 VEN Enable Threshold Turn on Turn off nA 1 5 µA 0.4 V V 20 40 µA 1.05 1.2 1.35 MHz 30 32 34 V 1.5 IEN Enable Pin Current fSW Oscillator Frequency VOVP Output Overvoltage Protection MIC2288 MLF™ package option only TJ Overtemperature Threshold Shutdown Hysteresis % VEN = 10V 150 10 °C °C Notes: 1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(max), the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. 2. This device is not guaranteed to operate beyond its specified operating rating. 3. IC devices are inherently ESD sensitive. Handling precautions required. Human body model rating: 1.5K in series with 100pF. 4. Specification for packaged product only. 5. ISD = IVIN. April 2005 3 M9999-042205 MIC2288 Micrel, Inc. Typical Characteristics 83 81 79 VIN = 3.6V VIN = 3.3V 77 75 0 1.8 25 50 75 100 125 150 OUTPUT CURRENT (mA) 12.1 12.05 12 11.95 11.9 11.8 0 Current Limit vs. Supply Current 1.4 1.4 1.2 1 0.8 0.6 0.4 300 200 VIN = 3.6V 200 400 600 800 1000 SWITCH CURRENT (mA) 700 88 86 84 82 4 5.5 7 8.5 SUPPLY VOLTAGE (V) 10 1.22 1.20 1.18 1.16 1.14 1.12 1.10 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 300 400 300 200 VIN = 3.6V I = 500mA 100 200 150 100 50 ISW = 500mA 0 2.5 1.4 SW 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 95 93 91 89 VIN = 3.6V 87 85 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 4 4 5.5 7 8.5 SUPPLY VOLTAGE (V) 10 Frequency vs. Temperature 1.3 1.2 1.1 1.0 0.9 0.8 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) Maximum Duty Cycle vs. Temperature 97 Switch Saturation vs. Supply Voltage 250 Switch Saturation vs. Temperature 500 Feedback Voltage vs. Temperature 1.26 1.24 600 99 92 90 M9999-042205 0.4 Maximum Duty Cycle vs. Supply Voltage 96 94 80 2.5 0.6 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) SWITCH SATURATION VOLTAGE (mV) Switch Saturation vs. Current 400 100 98 0.8 10 500 0 0 Current Limit vs. Temperature 1.0 MAXIMUM DUTY CYCLE (%) SWITCH SATURATION VOLTAGE (mV) MAXIMUM DUTY CYCLE (%) 4 5.5 7 8.5 SUPPLY VOLTAGE (V) 600 100 50 75 100 125 150 LOAD (mA) 0.2 0.2 700 25 1.2 CURRENT LIMIT (A) CURRENT LIMIT (A) 1.6 0 2.5 VIN = 3.6V 11.85 FEEDBACK VOLTAGE (V) 85 12.15 1.30 1.28 SWITCH SATURATION VOLTAGE (mV) VIN = 4.2V 87 Load Regulation FREQUENCY (MHz) EFFICIENCY (%) 89 12.2 700 FEEDBACK CURRENT (nA) Efficiency at VOUT = 12V OUTPUT VOLTAGE (V) 91 FB Pin Current vs. Temperature 600 500 400 300 200 100 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) April 2005 MIC2288 Micrel, Inc. Function Characteristics OUTPUT VOLTAGE (1mV/div) AC-Coupled Line Transient Response Enable Voltage 3.6VIN 12VOUT 150mA Load 3.2V 12VOUT 150mA Load Time (400µs/div) Load Transient Response Switching Waveforms 10mA 3.6VIN 12VOUT COUT = 10µF 5 SWITCH SATURATION (5V/div) 150mA OUTPUT VOLTAGE (50mV/div) Time (400µs/div) Time (400µs/div) April 2005 4.2V INPUT VOLTAGE (2V/div) Output Voltage INDUCTOR CURRENT (500mA/div) LOAD CURRENT OUTPUT VOLTAGE (100mA/div) (100mV/div) AC-Coupled ENABLE VOLTAGE (2V/div) OUTPUT VOLTAGE (5V/div) Enable Characteristics Output Voltage Inductor Current (10µH) VSW 3.6VIN 12VOUT 150mA Time (400ns/div) M9999-042205 MIC2288 Micrel, Inc. Functional Diagram VIN FB OVP* EN OVP* SW PWM Generator gm VREF 1.24V Σ 1.2MHz Oscillator Ramp Generator CA GND *OVP available on MLFTM package option only. Figure 1. MIC2288 Block Diagram The gm error amplifier measures the feedback voltage through the external feedback resistors and amplifies the error between the detected signal and the 1.24V reference voltage. The output of the gm error amplifier provides the voltage-loop signal that is fed to the other input of the PWM generator. When the current-loop signal exceeds the voltage-loop signal, the PWM generator turns off the bipolar output transistor. The next clock period initiates the next switching cycle, maintaining the constant frequency current-mode PWM control. Functional Description The MIC2288 is a constant frequency, PWM current mode boost regulator. The block diagram is shown in Figure 1. The MIC2288 is composed of an oscillator, slope compensation ramp generator, current amplifier, gm error amplifier, PWM generator, and a 1A bipolar output transistor. The oscillator generates a 1.2MHz clock. The clock’s two functions are to trigger the PWM generator that turns on the output transistor, and to reset the slope compensation ramp generator. The current amplifier is used to measure the switch current by amplifying the voltage signal from the internal sense resistor. The output of the current amplifier is summed with the output of the slope compensation ramp generator. This summed current-loop signal is fed to one of the inputs of the PWM generator. M9999-042205 6 April 2005 MIC2288 Micrel, Inc. Applications Information Component Selection DC-to-DC PWM Boost Conversion The MIC2288 is a constant-frequency boost converter. It operates by taking a DC input voltage and regulating a higher DC output voltage. Figure 2 shows a typical circuit. Boost regulation is achieved by turning on an internal switch, which draws current through the inductor (L1). When the switch turns off, the inductor’s magnetic field collapses, causing the current to be discharged into the output capacitor through an external Schottky diode (D1). Voltage regulation is achieved by modulating the pulse width or pulse-width modulation (PWM). Inductor Inductor selection is a balance between efficiency, stability, cost, size, and rated current. For most applications a 10µH is the recommended inductor value. It is usually a good balance between these considerations. Larger inductance values reduce the peak-to-peak ripple current, affecting efficiency. This has the effect of reducing both the DC losses and the transition losses. There is also a secondary effect of an inductor’s DC resistance (DCR). The DCR of an inductor will be higher for more inductance in the same package size. This is due to the longer windings required for an increase in inductance. Since the majority of input current (minus the MIC2288 operating current) is passed through the inductor, higher DCR inductors will reduce efficiency. To maintain stability, increasing inductor size will have to be met with an increase in output capacitance. This is due to the unavoidable “right half plane zero” effect for the continuous current boost converter topology. The frequency at which the right half plane zero occurs can be calculated as follows: L1 10µH VIN D1 VOUT MIC2288BML VIN C1 2.2µF SW OVP EN C2 10µF FB GND GND R1 R2 GND Figure 2. Typical Application Circuit Frhpz = Duty Cycle Considerations Duty cycle refers to the switch on-to-off time ratio and can be calculated as follows for a boost regulator: D = 1− 2 VOUT × L × IOUT × 2π The right half plane zero has the undesirable effect of increasing gain, while decreasing phase. This requires that the loop gain is rolled off before this has significant effect on the total loop response. This can be accomplished by either reducing inductance (increasing RHPZ frequency) or increasing the output capacitor value (decreasing loop gain). Output Capacitor Output capacitor selection is also a trade-off between performance, size, and cost. Increasing output capacitance will lead to an improved transient response, but also an increase in size and cost. X5R or X7R dielectric ceramic capacitors are recommended for designs with the MIC2288. Y5V values may be used but to offset their tolerance over temperature, more capacitance is required. The following table shows the recommended ceramic (X5R) output capacitor value vs. output voltage. VIN VOUT The duty cycle required for voltage conversion should be less than the maximum duty cycle of 85%. Also, in light load conditions where the input voltage is close to the output voltage, the minimum duty cycle can cause pulse skipping. This is due to the energy stored in the inductor causing the output to overshoot slightly over the regulated output voltage. During the next cycle, the error amplifier detects the output as being high and skips the following pulse. This effect can be reduced by increasing the minimum load or by increasing the inductor value. Increasing the inductor value reduces peak current, which in turn reduces energy transfer in each cycle. Overvoltage Protection For the MLF™ package option, there is an overvoltage protection function. If the feedback resistors are disconnected from the circuit or the feedback pin is shorted to ground, the feedback pin will fall to ground potential. This will cause the MIC2288 to switch at full duty cycle in an attempt to maintain the feedback voltage. As a result, the output voltage will climb out of control. This may cause the switch node voltage to exceed its maximum voltage rating, possibly damaging the IC and the external components. To ensure the highest level of protection, the MIC2288 OVP pin will shut the switch off when an overvoltage condition is detected, saving itself and other sensitive circuitry downstream. April 2005 VIN Output Voltage Recomended Output Capacitance <6V 22µF <16V 10µF <34V 4.7µF Table 1. Output Capacitor Selection Diode Selection The MIC2288 requires an external diode for operation. A Schottky diode is recommended for most applications due to their lower forward voltage drop and reverse recovery time. Ensure the diode selected can deliver the peak inductor current and the maximum reverse voltage is rated greater than the output voltage. 7 M9999-042205 MIC2288 Micrel, Inc. Input capacitor A minimum 1µF ceramic capacitor is recommended for designing with the MIC2288. Increasing input capacitance will improve performance and greater noise immunity on the source. The input capacitor should be as close as possible to the inductor and the MIC2288, with short traces for good noise performance. Feedback Resistors The MIC2288 utilizes a feedback pin to compare the output to an internal reference. The output voltage is adjusted by selecting the appropriate feedback resistor network values. The R2 resistor value must be less than or equal to 5kΩ (R2 ≤ 5kΩ).The desired output voltage can be calculated as follows: R1 VOUT = VREF × + 1 R2 where VREF is equal to 1.24V. M9999-042205 8 April 2005 MIC2288 Micrel, Inc. Application Circuits L1 4.7µH VIN 3V to 4.2V L1 10µH VIN 3V to 4.2V VOUT 5V @ 400mA D1 MIC2288BML MIC2288BML C1 4.7µF 6.3V R1 5.62k SW VIN FB R2 1.87k GND GND R1 54.9k SW VIN C1 2.2µF 10V C2 22µF 6.3V OVP EN VOUT 15V @ 100mA D1 EN FB R2 5k GND GND GND C2 10µF 16V OVP GND C1 4.7µF, 6.3V, 0805 X5R Ceramic Capacitor 08056D475MAT AVX C1 2.2µF, 10V, 0805 X5R Ceramic Capacitor 08052D225KAT AVX C2 22µF, 6.3V, 0805 X5R Ceramic Capacitor 12066D226MAT AVX C2 10µF, 16V, 1206 X5R Ceramic Capacitor 1206YD106MAT AVX D1 1A, 40V Schotty Diode MBRM140T3 ON Semi. D1 1A, 40V Schotty Diode MBRM140T3 ON Semi. L1 4.7µH, 650mA Inductor LQH32CN4R7M11 Murata L1 10µH, 650mA Inductor LQH43CN100K03 Murata Figure 6. 3.3VIN – 4.2VIN to 15VOUT @ 100mA Figure 3. 3.3VIN to 5VOUT @ 400mA L1 10µH VIN 3V to 4.2V L1 10µH VIN 3V to 4.2V VOUT 9V @ 180mA D1 MIC2288BML MIC2288BML C1 2.2µF 10V VIN R1 31.6k SW FB GND C1 2.2µF, 10V, 0805 X5R Ceramic Capacitor GND 08052D225KAT AVX 10µF, 16V, 1206 X5R Ceramic Capacitor 1206YD106MAT AVX D1 1A, 40V Schotty Diode MBRM140T3 ON Semi. 10µH, 650mA Inductor LQH43CN100K03 Murata L1 10µH FB R2 1k GND 2.2µF, 10V, 0805 X5R Ceramic Capacitor 08052D225KAT AVX C2 4.7µF, 25V, 1206 X5R Ceramic Capacitor 12063D475MAT AVX D1 1A, 40V Schotty Diode MBRM140T3 ON Semi. L1 10µH, 650mA Inductor LQH43CN100K03 Murata Figure 7. 3.3VIN – 4.2VIN to 24VOUT @ 50mA L1 10µH VIN 5V VOUT 12V @ 100mA D1 EN C1 Figure 4. 3.3VIN – 4.2VIN to 9VOUT @ 180mA VIN 3V to 4.2V C2 4.7µF 25V OVP GND C2 L1 R1 18.2k SW GND R2 5k GND VIN C1 2.2µF 10V C2 10µF 16V OVP EN VOUT 24V @ 50mA D1 VOUT 9V @ 330mA D1 MIC2288BML MIC2288BML C1 2.2µF 10V VIN SW R1 42.3k C2 10µF 16V OVP EN FB GND GND C1 2.2µF 10V VIN SW OVP EN FB GND R2 5k R1 31.6k GND R2 5k C2 10µF 16V GND GND C1 2.2µF, 10V, 0805 X5R Ceramic Capacitor 08052D225KAT AVX C1 2.2µF, 10V, 0805 X5R Ceramic Capacitor 08052D225KAT AVX C2 10µF, 16V, 1206 X5R Ceramic Capacitor 1206YD106MAT AVX C2 10µF, 16V, 1206 X5R Ceramic Capacitor 1206YD106MAT AVX D1 1A, 40V Schotty Diode MBRM140T3 ON Semi. D1 1A, 40V Schotty Diode MBRM140T3 ON Semi. L1 10µH, 650mA Inductor LQH43CN100K03 Murata L1 10µH, 650mA Inductor LQH43CN100K03 Murata Figure 8. 5VIN to 9VOUT @ 330mA Figure 5. 3.3VIN – 4.2VIN to 12VOUT @ 100mA April 2005 9 M9999-042205 MIC2288 Micrel, Inc. L1 10µH VIN 5V L1 10µH VIN 5V VOUT 12V @ 250mA D1 MIC2288BML MIC2288BML C1 2.2µF 10V VIN SW R1 43.2k OVP EN FB GND GND VOUT 24V @ 80mA D1 R2 5k C1 2.2µF 10V C2 10µF 16V VIN SW OVP EN FB GND GND GND R1 18.2k R2 1k C2 4.7µF 25V GND C1 2.2µF, 10V, 0805 X5R Ceramic Capacitor 08052D225KAT AVX C1 2.2µF, 10V, 0805 X5R Ceramic Capacitor 08052D225KAT AVX C2 10µF, 16V, 1206 X5R Ceramic Capacitor 1206YD106MAT AVX C2 4.7µF, 25V, 1206 X5R Ceramic Capacitor 12066D475MAT AVX D1 1A, 40V Schotty Diode MBRM140T3 ON Semi. D1 1A, 40V Schotty Diode MBRM140T3 ON Semi. L1 10µH, 650mA Inductor LQH43CN100K03 Murata L1 10µH, 650mA Inductor LQH32CN4R7M11 Murata Figure 10. 5VIN to 24VOUT @ 80mA Figure 9. 5VIN to 12VOUT @ 250mA M9999-042205 10 April 2005 MIC2288 Micrel, Inc. Package Information All Dimensions are in millimeters 5-Pin TSOT (D5) 8-Pin MLF™ (ML) 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. © 2004 Micrel, Incorporated. April 2005 11 M9999-042205