MIC2145 Micrel MIC2145 High Efficiency 2.5W Boost Converter Final General Description Features The MIC2145 is a small size boost switching regulator that can provide over 2.5W of output power. The input voltage range is between 2.4V to 16V, making the device suitable for one-cell Li-Ion and 3- to 4-cell alkaline/NiCad/NiMH applications. The output voltage of the MIC2145 can be adjusted up to 16V. The MIC2145 is well suited for portable, space-sensitive applications. Its typical 450kHz operation allows small surface mount external components to be used. The MIC2145 has a low quiescent current of 200µA, and a typical shutdown current of 0.5µA. The MIC2145 is capable of high efficiencies in a small board area. The MIC2145 features a low-on resistance internal switch that allows it to provide over 2.5W of output power. The peak switch current can be programmed through an external resistor. This allows the user to set the peak switch current at the level where maximum efficiency occurs. It also allows the user to further optimize for efficiency and inductor size by setting the peak current below the level of inductor saturation. The MIC2145 is available in an MSOP-8 and 3mm×3mm MLF™-10L package with an ambient operating temperature range from –40°C to +85°C. • • • • • • • • • • 2.4V to 16V input voltage Output adjustable to 16V Programmable peak current limit Soft start Up to 450kHz switching frequency 0.5µA shutdown current 200µA quiescent current Capable of 5V/ 500mA output with 3.3V input Achieves over 85% efficiency Implements low power BOOST, SEPIC, and FLYBACK topologies • MSOP-8 and 3mm×3mm MLF™-10L Applications • • • • • Flash LED driver LCD bias supply White LED driver DSL bias supply Local 3V to 5V conversion Ordering Information Part Number Voltage Ambient Temp. Range Package MIC2145BMM Adj –40°C to +85°C 8-lead MSOP MIC2145BML Adj –40°C to +85°C 3×3 MLF™-10L Typical Application L1 VIN 3.0V to 5.0V 10V Output Efficiency 10 H 90 D1 1 4 EN PGND SW VDD VOUT 10V/150mA 5 6 COUT 10 F/16V MIC2145BMM 3 2 RSET SS FB 7 SGND 8 85 EFFICIENCY (%) CIN 10 F/6.3V 80 75 70 65 I Limit 60 10 VIN = 3.0V 100 1000 OUTPUT CURRENT (mA) Adjustable Output Boost Converter with Programmable Peak Switch Current Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com May 2003 1 MIC2145 MIC2145 Micrel Pin Configuration EN 1 8 SGND SS 2 7 FB RSET 3 6 VDD PGND 4 5 SW EN 1 SS 2 RSET 3 PGND 4 PGND 5 10 SGND 9 FB 8 VDD 7 SW 6 SW 3mm× ×3mm MLF-10L (ML) 8-Lead MSOP (MM) Pin Description Pin Number MSOP Pin Number MLF Pin Name 1 1 EN Enable (Input): Logic high (≥1.5V) enables regulator. Logic low (≤0.7V) shuts down regulator. Do not float. 2 2 SS Soft Start Capacitor (External Component): Connect external capacitor to ground to control the rise time of the output voltage. 3 3 RSET Current Limit (External Component): Sets peak current limit of the internal power MOSFET using an external resistor. 4 4, 5 PGND Power Ground (Return): Internal power MOSFET source. 5 6, 7 SW Switch Node (Input): Internal power MOSFET drain. 6 8 VDD Supply (Input): +2.4V to +16V for internal circuitry. 7 9 FB 8 10 SGND MIC2145 Pin Function Feedback (Input): Output voltage sense node. Small Signal Ground (Return): Ground 2 May 2003 MIC2145 Micrel Absolute Maximum Ratings (Note 1) Operating Ratings (Note 2) Supply Voltage (VDD) .................................................... 18V Switch Voltage (VSW) .................................................... 18V Feedback Voltage (VFB) ................................................ 18V Switch Current (ISW) ........................................................ 2A Enable Voltage(VEN), Note 5 ........................................ 18V RSET Voltage (VRSET) .................................................... 6V ESD Rating, Note 3 ...................................................... 2kV Ambient Storage Temperature(TS) .......... –65°C to +150°C Supply Voltage (VDD) ....................................... 2.4V to 16V Switch Voltage (VSW) .................................................... 16V Ambient Temperature (TA) ......................... –40°C to +85°C Junction Temperature (TJ) ....................... –40°C to +125°C Package Thermal Resistance MSOP θJA (MSOP-8) .................................................... 206°C/W θJA (3mm×3mm MLF-10) .................................... 60°C/W Electrical Characteristics (Note 6) VDD = 10V, VOUT = 10V, IOUT = 100mA; TJ =25°C, unless otherwise noted, bold values indicate –40°C ≤ TJ ≤ 125°C. Parameter Condition Min Supply Voltage Typ 2.4 Max Units 16 V Shutdown Current EN = 0.3V, VDD = 10V, VFB=1.35V 0.5 5 µA Quiescent Current EN = VDD, VDD = 10V, VFB = 1.35V 200 300 µA Feedback Voltage Reference (±2%) 1.058 1.08 1.102 V (±3%) 1.048 1.112 V Comparator Hysteresis 18 mV Feedback Input Current VFB=1.35V 40 nA Peak Current Limit RSET=200Ω, VDD = 3.6V, Note 4 0.8 A RSET=1kΩ, VDD = 10V, Note 4 0.9 A 500 ns Current Limit Comparator Propagation Delay Switch On-Resistance ISW = 150mA, VDD = 3.0V 500 750 mΩ ISW = 1.2A, VDD = 10V 250 400 mΩ Maximum Off Time Enable Input Voltage Enable Input Current Soft Start Current 1000 Logic Low (turn-off) 1.1 ns 0.7 Logic High (turn-on) 1.5 1.1 V VEN = 0V –1 0.01 1 µA VEN = 2V –1 0.01 1 µA VEN = 2V, VDD=3.0V –8 –12 –16 µA 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. Human body model, 1.5KΩ in series with 100pF. Note 4. The current is measured in a DC mode. Actual peak switching current will be higher due to internal propagation delay of the circuit. Note 5. VEN ≤ VDD. Note 6. Specification for packaged product only. May 2003 V 3 MIC2145 MIC2145 Micrel Typical Characteristics Efficiency-Bootstrapped Configuration 90 10.0 8 10 12 VDD (V) 14 FEEDBACK VOLTAGE (V) 0.25 0.20 0.15 0.10 4 6 VOUT (V) 0.5 0.4 0.3 0.2 0.1 0.0 0 0.6 0.5 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 8 10 12 14 16 18 VDD (V) Feedback Current vs. Temperature 0.10 1.09 0.09 0.08 1.08 1.07 1.06 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Quiescent Current vs. Temperature 0.50 SHUTDOWN CURRENT (µA) 0.8 0.7 0.8 Shutdown Current vs. Temperature 1.5 1.0 0.9 6 0.9 1.1 Off Time vs. Temperature 1.2 1.1 4 1.05 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 8 10 12 14 16 18 VDD (V) 1.4 1.3 2 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0 0.01 0.08 0.07 0.04 0.03 0.7 0.6 1.0 Feedback Voltage vs. Temperature Quiescent Current vs. VDD 0.35 0.30 SWITCH ON-RESISTANCE (Ω) SWITCH ON-RESISTANCE (Ω) 16 0.9 0.8 FEEDBACK CURRENT (µA) 6 1.0 0.50 QUIESCENT CURRENT (mA) 4 0.45 0.40 MIC2145 0.02 Switch On-Resistance vs. Temperature L = 10µH 2 0.01 Switch On-Resistance vs. VDD 14.6 14.4 QUIESCENT CURRENT (Ω) 0 Line Regulation IOUT = 10mA 0 9.2 VIN = 3.6V L = 10µH OUTPUT CURRENT (A) 15.0 14.8 0.05 0.00 9.4 OUTPUT CURRENT (A) 15.4 15.2 0.50 9.6 OUTPUT CURRENT (A) 15.8 15.6 2 50 9.8 VIN = 3.3V VOUT = 10V L = 10µH 60 16.0 14.2 14.0 70 0.08 0.07 0.04 0.03 0.02 0.01 0 50 0.06 VIN = 3.3V VOUT = 10V L = 10µH 0.06 70 80 0.05 80 VOUT (V) 90 EFFICIENCY (%) 10.2 60 OFF TIME (µs) Load Regulation 100 0.05 EFFICIENCY (%) Efficiency-Basic Configuration 100 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 4 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 VIN = 3.6V 0.00 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) May 2003 MIC2145 Micrel Peak Current Limit vs. Temperature 12 10 8 6 4 2 VIN = 3.6V 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) May 2003 PEAK CURRENT LIMIT (A) SOFT START CURRENT (µA) 14 1.4 RSET = 200 1.3 1.2 1.1 R = 500 1.0 SET RSET = 1k 0.9 0.8 0.7 0.6 0.5 0.4 V = 3.6V RSET = 10k 0.3 IN 0.2 VOUT = 10V 0.1 L = 10µH 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 5 Peak Current Limit vs. RSET 2000 PEAK CURRENT LIMIT (mA) Soft Start Current vs. Temperature VIN = 1800 15V 1600 12V 1400 10V 1200 8.0V 1000 800 600 L = 10µH 400 VOUT/VIN > 1.25 100 1000 10000 RSET(Ω) 5.0V 4.2V 3.6V 3.3V 3.0V 2.4V 100000 MIC2145 MIC2145 Micrel Functional Diagram 10µH VIN L1 CIN D1 VDD 6 SW VOUT 5 R1 RSET 3 Thermal Shutdown COUT R2 Current Limit Comparator RSET CFF Soft Start One Shot 800nS POWER MOSFET SGND 8 PGND 4 Feedback Comparator FB 7 /S /Q EN VREF /R On(/Off) R1 VOUT = 1.08 1 + R2 1 SS 2 CSS Figure 1. Block Diagram MIC2145 6 May 2003 MIC2145 Micrel Output The maximum output voltage is limited by the voltage capability of the output switch. Output voltages of up to 16V can be achieved with the boost circuit. Higher output voltages require a flyback configuration. Peak Current Limit The peak current limit is externally set with a resistor. The peak current range is from 420mA to 2A. There is a minimum resistor value for RSET at lower VDD voltages. For resistor value selections, see the “Typical Characteristics: Peak Current Limit vs. RSET”. Soft Start The MIC2145 has a built in soft start that controls the rise time of the output voltage and the peak current limit threshold during start up. Functional Description See “Application Information” for component selection and pre-designed circuits. Overview The MIC2145 is a 2.5W boost regulator with programmable peak current limit and a constant off time. Quiescent current for the MIC2145 is typically 200µA when the switch is in the off state. Efficiencies above 80% throughout most operating conditions can be realized. Regulation Regulation is achieved by both of the comparators, which regulate the inductor current and the output voltage by gating the power MOSFET. Initially, power is applied to the SW and VDD pins. When the part is enabled, the power MOSFET turns on and current flows. When the current exceeds the peak current limit threshold, the current limit comparator fires the one-shot to turn off the power MOSFET for 1000ns and resets the SR flip-fop. The current limit comparator continues to cycle the power MOSFET on and off until the output voltage trips the upper threshold of the feedback comparator, which terminates the cycle. The cycle will begin again when the output voltage drops below the lower hysteresis threshold of the feedback comparator. The feedback comparator has a typical hysteresis of 18mV. Due to the gain of the feedback resistor divider, the voltage at VOUT experiences a typical 167mV of hysteresis for 10V output at 2.4V VDD. This can be reduced by adding a feed-forward capacitor, CFF (See “Output Voltage” section). VEN (2V/div) VIN = 3V VOUT = 10V RSET = 10k CSS = 0.01µF VOUT (5V/div) VSW (5V/div) IINDUCTOR (500mA/div) Time 200µs Figure 3. Typical Soft Start Waveforms Thermal Shutdown Built-in thermal protection circuitry turns off the power MOSFET when the junction temperature exceeds about 150°C. VOUT AC Couple (100mV/div) VSW (5V/div) IINDUCTOR (500mA/div) Time 20µs Figure 2. Typical Regulator Waveforms May 2003 7 MIC2145 MIC2145 Micrel Application Information A value of 1MΩ is recommended for R1 to minimize the quiescent current when the part is off. Then, R2 can be solved using the above equation. A feed-forward capacitor, CFF, ranging from 5pF to 100pF can be used in parallel with R1 to reduce the peak-to-peak output voltage ripple, which is shown in Figures 4 and 5. Pre-designed circuit information is at the end of this section. Output Voltage The output voltage of the regulator can be set between 2.4V and 16V by connecting a resistor divider at the FB pin. The resistor values are selected by the following equations: R 2= 1.08V • R1 VOUT − 1.08V VOUT AC Couple (100mV/div) VOUT AC Couple (100mV/div) VSW (5V/div) VSW (5V/div) Time 4µs Time 20µs Figure 5. With Feed-Forward Capacitor (100pF) Figure 4. Without Feed-Forward Capacitor MIC2145 8 May 2003 MIC2145 Micrel Bootstrap A bootstrapped configuration is recommended for applications that require high efficiency at heavy loads (>70mA). This is achieved by connecting the VDD pin to VOUT (see Figure 7). For applications that require high efficiency at light loads (<70mA), the VDD pin is connected to the input voltage (VIN); this is referred to as the basic configuration (see Figure 6). L1 10µH Sumida CR43-100 VIN 3.6V D1 On Semiconductor MBR0530T1 C1 10µF/6.3V Murata GRM42-6 X5R 106K 6.3 VDD EN SW PGND MIC2145 FB RSET SS R1 100k R2 10k R4 1M SGND C3 100pF VOUT 5V/250mA C4 10µF/6.3V Murata GRM42-6 X5R 106K 6.3 R3 274k C2 0.01µF Figure 6. Basic Configuration L1 10µH Sumida CR43-100 VIN 3.6V D1 On Semiconductor MBR0530T1 C1 10µF/6.3V Murata GRM42-6 X5R 106K 6.3 PGND SW SGND VDD MIC2145 R2 10k C3 100pF RSET EN SS R1 FB 100k VOUT 5V/350mA C4 10µF/6.3V Murata GRM42-6 X5R 106K 6.3 R4 1M C2 0.01µF R3 274k Figure 7. Bootstrap Configuration May 2003 9 MIC2145 MIC2145 Micrel Inductor The MIC2145 has a programmable peak current to allow the usage of small surface mount inductors. A 10µH or 4.7µH inductor is recommended for most portable applications such as powering white LEDs and biasing LCD panels. The inductor should have a saturation current rating higher than the peak current during circuit operation. A low ESR (Equivalent Series Resistance) inductor is also desirable for high efficiency. Below are tables that list the maximum output current at minimum input voltage with efficiencies greater than 80%. VIN(min) VIN(max) RSET IOUT(max) VOUT VIN(min) VIN(max) RSET IOUT(max) VOUT (V) (V) (Ω) (mA) (V) (V) (V) (Ω ) (mA) (V) 80 5 160 5 25 10 100 10 11.5 20 12 11.5 90 12 14.5 15 15 14.5 70 15 4.5 150 5 4.5 250 5 50 10 150 10 11.5 40 12 11.5 120 12 14.5 30 15 14.5 100 15 4.5 250 5 4.5 350 5 70 10 170 10 11.5 50 12 11.5 150 12 14.5 40 15 14.5 120 15 9.5 190 10 9.5 300 10 130 12 250 12 90 15 200 15 4.5 9.5 2.4 9.5 2.4 10k 9.5 3.0 9.5 9.5 10k 14.5 9.5 5.0 10k 11.5 10k 14.5 Table 2. Typical Application for 10µH Inductor in Bootstrap Configuration Table 1. Typical Application for 10µH Inductor in Basic Configuration VIN(min) VIN(max) RSET IOUT(max) VOUT VIN(min) VIN(max) RSET IOUT(max) VOUT (V) (V) (Ω) (mA) (V) (V) (V) (Ω) (mA) (V) 250 5 500 5 80 10 225 10 4.5 9.5 3.0 4.5 4.5 3.0 400 200 9.5 60 12 4.5 150 12 9.5 50 15 4.5 130 15 Table 4. Typical Application for 4.7µH Inductor in Bootstrap Configuration Table 3. Typical Application for 4.7µH Inductor in Basic Configuration MIC2145 10k 3.6 10k 11.5 10k 3.0 10k 3.6 5.0 4.5 10 May 2003 MIC2145 Micrel Diode A Schottky diode should be used for the output diode. Most of the application circuits on this data sheet specify the Motorola MBR0530 surface mount Schottky diode. It has a forward current of 0.5A and a low forward voltage drop. For applications that are cost driven, the 1N4148 or equivalent can be used but the efficiency will suffer due to higher forward voltage drop. Output Capacitor Low ESR capacitors should be used at the output of the MIC2145 to minimize the switching output ripple voltage. Selection of the capacitor value will depend upon the peak inductor current, inductor size, and the load. MuRata offers the GRM43-2 series with up to 10µF at 25V, with a X5R temperature coefficient in a 1812 surface-mount package. For lower output voltage applications, the GRM42-2 (1210 package/10µF/16V) and GRM42-6 (1206 package/10µF/ 6.3V) series can be used. Typically, values ranging from 10µF to 47µF can be used for the output capacitor. May 2003 Reducing Peak Current If lower than 400mA peak current is required then the soft start pin may be shorted to ground. This changes the reference of the current limit comparator. With the soft start pin shorted to ground, the maximum current will approximately reduce to half. The peak current should always be set at least 50% higher than the maximum load current. 11 MIC2145 MIC2145 Micrel Pre-designed Application Circuits L1 4.7µH Murata LQH3C4R7M24 VIN 3.0V-4.2V C1 10µF/6.3V Murata GRM42-6 X5R 106K 6.3 D1 On Semiconductor MBR0530T1 VDD JP1 EN FB LED1 LED2 LEDn R R R R3 274k SGND SS R2 10k C4 10µF/6.3V Murata GRM42-6 X5R 106K 6.3 R4 C3 1M 100pF PGND MIC2145 RSET R1 100k VOUT 5V SW C2 0.01µF VIN VOUT Load Ripple Voltage Efficiency V V mA mV(peak-peak) % 3.6 5.0 40 <100 85 5V Output Efficiency 90 EFFICIENCY (%) 85 80 75 70 65 VIN = 3.6V 60 1 10 100 1000 OUTPUT CURRENT (mA) Figure 8. White LED Driver Application (Drives 1 to 10 LEDs in Parallel) MIC2145 12 May 2003 MIC2145 Micrel L1 10µH Sumida CR32-100 VIN 3.0V-5.0V C1 10µF/6.3V Murata GRM42-6 X5R 106K 6.3 D1 On Semiconductor MBR0530T1 PGND JP1 EN VDD MIC2145 RSET SS R1 100k R2 10k VOUT 10.0V SW R4 1M C3 100pF FB C4 10µF/16V Murata GRM42-2 X5R 106K 16 R3 121k SGND C2 0.01µF VIN VOUT Load Ripple Voltage Efficiency V V mA mV(peak-peak) % 3.0 10.0 150 <200 83 10V Output Efficiency 90 EFFICIENCY (%) 85 80 75 70 65 60 10 VIN = 3.0V 100 1000 OUTPUT CURRENT (mA) Figure 9. LCD Application — Bootstrap Configuration May 2003 13 MIC2145 MIC2145 Micrel L1 10 H Sumida CR32-100 VIN 3.0V-5.0V C1 10 F/6.3V Murata GRM42-6 X5R 106K 6.3 D1 On Semiconductor MBR0530T1 PGND JP1 EN VDD MIC2145 R1 100k R2 10k R4 1M LED1 LED2 LED3 LED4 C4 10 F/16V Murata GRM42-2 X5R 106K 16 C3 100pF FB RSET SS VOUT 15.0V SW R R3 78.7k SGND C2 0.01 F VIN VOUT Load Ripple Voltage Efficiency V V mA mV(peak-peak) % 3.6 15.0 40 <100 85 15V Output Efficiency 90 EFFICIENCY (%) 85 80 75 70 65 VIN = 3.6V 60 1 10 100 OUTPUT CURRENT (mA) Figure 10. Series White LED Driver Application MIC2145 14 May 2003 MIC2145 Micrel Package Information 0.199 (5.05) 0.187 (4.74) 0.122 (3.10) 0.112 (2.84) DIMENSIONS: INCH (MM) 0.120 (3.05) 0.116 (2.95) 0.036 (0.90) 0.032 (0.81) 0.043 (1.09) 0.038 (0.97) 0.007 (0.18) 0.005 (0.13) 0.012 (0.30) R 0.008 (0.20) 0.004 (0.10) 0.012 (0.3) 0.0256 (0.65) TYP 5° MAX 0° MIN 0.012 (0.03) R 0.039 (0.99) 0.035 (0.89) 0.021 (0.53) 8-Pin MSOP (MM) 0.85 +0.15 —0.05 1.60 +0.15 —0.15 3.00 BSC. 0.80 +0.15 —0.15 1.50 BSC. 0.01 +0.04 —0.01 0.48 typ. PIN 1 ID 0.23 +0.07 —0.05 1 1 1.50 BSC. +0.15 2 1.15 —0.15 2 3.00 BSC. 3 2.30 +0.15 —0.15 3 0.20 dia 0.50 BSC. 0.40 +0.15 —0.05 TOP SEATING PLANE TERMINAL TIP BOTTOM 0.23 +0.07 —0.05 0.50 BSC. 0.01 +0.04 —0.01 0.50 BSC. TERMINAL TIP ODD TERMINAL SIDE EVEN TERMINAL SIDE 10-Pin MLF (ML) MICREL, INC. TEL 1849 FORTUNE DRIVE SAN JOSE, CA 95131 + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB USA http://www.micrel.com The information furnished by Micrel in this datasheet 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 at Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2003 Micrel, Incorporated. May 2003 15 MIC2145