MIC2145BMM

MIC2145 Micrel, Inc. MIC2145 High Efficiency 2.5W Boost Converter 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 Standard Pb-Free Voltage Ambient Temp. Range Package MIC2145BMM MIC2145YMM Adj –40°C to +85°C 8-lead MSOP MIC2145BML MIC2145YML Adj –40°C to +85°C 10-lead MLF™ Typical Application L1 VIN 3.0V to 5.0V 10V Output Efficiency 10µH 90 D1 1 4 EN PGND SW VDD VOUT 10V/150mA 5 6 COUT 10µF/16V MIC2145BMM 3 2 RSET SS FB 7 SGND 8 85 EFFICIENCY (%) CIN 10µF/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 MLF and MicroLeadFrame are trademarks of Amkor Technologies, 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 MIC2145 Micrel, Inc. 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 M9999-042205 Pin Function Feedback (Input): Output voltage sense node. Small Signal Ground (Return): Ground 2 April 2005 MIC2145 Micrel, Inc. 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. April 2005 V 3 M9999-042205 MIC2145 Micrel, Inc. Typical Characteristics Efficiency-Bootstrapped Configuration 90 10.0 8 10 12 VDD (V) 14 0.30 0.25 0.20 0.15 0.10 0.05 4 6 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) 0.9 0.8 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) Feedback Current vs. Temperature 1.08 1.07 1.06 0.10 0.09 0.08 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) Shutdown Current vs. Temperature SHUTDOWN CURRENT (µA) 0.8 0.7 8 10 12 14 16 18 VDD (V) 1.05 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 1.5 1.0 0.9 6 1.09 Off Time vs. Temperature 1.2 1.1 4 1.1 8 10 12 14 16 18 VDD (V) 1.4 1.3 2 0.50 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 0.09 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 0.6 0.5 1.0 Feedback Voltage vs. Temperature FEEDBACK VOLTAGE (V) 0.40 0.35 SWITCH ON-RESISTANCE (Ω) VOUT (V) SWITCH ON-RESISTANCE (Ω) 16 0.8 0.7 FEEDBACK CURRENT (µA) 6 1.0 0.9 Quiescent Current vs. Temperature QUIESCENT CURRENT (mA) 4 Quiescent Current vs. VDD M9999-042205 0.02 Switch On-Resistance vs. Temperature L = 10µH 2 0.01 Switch On-Resistance vs. VDD 14.4 14.2 QUIESCENT CURRENT (Ω) 0 Line Regulation 14.8 14.6 0 9.2 VIN = 3.6V L = 10µH OUTPUT CURRENT (A) 15.2 15.0 0.00 9.4 OUTPUT CURRENT (A) IOUT = 10mA 0.50 0.45 9.6 OUTPUT CURRENT (A) 15.6 15.4 2 50 9.8 VIN = 3.3V VOUT = 10V L = 10µH 60 16.0 15.8 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 0.50 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) April 2005 MIC2145 Micrel, Inc. 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) April 2005 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 M9999-042205 MIC2145 Micrel, Inc. 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 M9999-042205 6 April 2005 MIC2145 Micrel, Inc. 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 April 2005 7 M9999-042205 MIC2145 Micrel, Inc. 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: R2 = 1.08 × R1 VOUT − 1.08 VOUT AC (100mV/div) VOUT AC (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 M9999-042205 8 April 2005 MIC2145 Micrel, Inc. 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 (