MIC2204 Micrel, Inc. MIC2204 High-Efficiency 2MHz Synchronous Buck Converter General Description Features The Micrel MIC2204 is a high-efficiency, 2MHz PWM synchronous buck switching regulator. Power conversion efficiency of above 95% is easily obtainable over a wide range of applications. A proprietary internal compensation technique ensures stability with the smallest possible inductor and ceramic output capacitor. • • • • • • • • • • • • • • • The MIC2204 operates from 2.3V to 5.5V input and features internal power MOSFETs that can supply over 600mA of output current with output voltages down to 1V. The MIC2204 implements a constant 2MHz pulse-width-modulation (PWM) control scheme which reduces spurious noise in sensitive RF and communication applications. Additionally, the MIC2204 can be synchronized to an external clock, or multiple MIC2204s can easily be daisy-chained with the SYNCLOCK feature. The MIC2204 has a high bandwidth loop (typ. 200kHz) which allows ultra-fast transient response times. This is very useful when powering applications that require fast dynamic responses, such as the CPU cores and RF circuitry in highperformance cellular phones and PDAs. Input voltage range: 2.3V to 5.5V Output down to 1V/ 600mA 2MHz PWM operation Ultra-fast transient response (typical 200kHz GBW) Internal compensation All ceramic capacitors >95% efficiency Fully integrated MOSFET switches Easily synchronized to external clock SYNCLOCK feature to daisy-chain multiple 2204s <340µA quiescent current Logic controlled micropower shutdown Thermal shutdown and current limit protection 10-pin MSOP and 3mm×3mm MLF™-10L –40°C to +125°C junction temperature range Applications • • • • • • The MIC2204 is available in 10-pin MSOP and 3mm × 3mm MLF™-10L package options with an operating junction temperature range from –40°C to 125°C . High-efficiency portable power Cellular phones PDAs 802.11 WLAN power supplies RF power supplies Li Ion battery powered applications Typical Application 4.7µH 3.3V 500mA MIC2204BMM 10 2 9 90 SYNC_IN 3 8 4 7 5 6 4.7µF SYNC_OUT EN 10nF EFFICIENCY (%) 2.3V to 6V 1 100 95 85 80 75 70 Efficiency vs. Output Current 4.2VIN 3.6VIN 5VIN 65 60 55 50 0 3.3VOUT 100 200 300 400 500 OUTPUT CURRENT (mA) Adjustable Output Synchronous Buck Converter 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 MIC2204 Micrel, Inc. Ordering Information Part Number Voltage Junction Temp. Range Package Lead Finish MIC2204BMM Adjustable –40°C to +125°C 10-pin MSOP Standard MIC2204YMM Adjustable –40°C to +125°C 10-pin MSOP Lead-Free MIC2204BML Adjustable –40°C to +125°C 10-pin MLF™ Standard MIC2204YML Adjustable –40°C to +125°C 10-pin MLF™ Lead-Free Pin Configuration SW 1 10 GND VIN 2 9 GND SYNC_IN 3 8 GND SYNC_OUT 4 7 BIAS EN 5 SW VIN SYNC_IN SYNC_OUT 1 2 3 4 5 EN 6 FB MSOP-10 (MM) 10 GND 9 GND 8 GND 7 BIAS 6 FB MLF-10 (ML) Pin Description Pin Number Pin Name 1 SW Switch (Output): Internal power MOSFET output switches. 2 VIN Supply Voltage (Input): Requires bypass capacitor to GND. 3 SYNC_IN SYNC_IN for the MIC2204: Sync the main switching frequency to an external clock. Tie pin to ground if not using this function. Tying SYNC_IN high reduces the switching frequency to 1.6MHz (See “Applications Information” section). 4 SYNC_OUT SYNC_OUT an open collector output to feed into SYNC_IN. Float or ground the SYNC_OUT pin if not using sync out function. 5 EN A low level EN will power down the device, reducing the quiescent current to under 15µA (typ. 6.5µA). 6 FB Input to the error amplifier, connect to the external resistor divider network to set the output voltage. 7 BIAS Internal circuit bias supply, nominally 2.3V. Must be de-coupled to signal ground with a 0.01µF capacitor. 8, 9, 10 GND Ground. M9999-042205 Pin Function 2 April 2005 MIC2204 Micrel, Inc. Absolute Maximum Ratings(1) Operating Ratings(3) Supply Voltage (VIN) ....................................................... 6V Output Switch Voltage (VSW) .......................................... 6V Logic Input Voltage (VEN, VSYNC_IN) ............... VIN to –0.3V Power Dissipation(2) Storage Temperature (TS) ....................... –65°C to +150°C Supply Voltage (VIN) ................................... +2.3V to +5.5V Junction Temperature (TJ) ................ –40°C ≤ TJ ≤ +125°C Package Thermal Resistance MSOP (θJA) ....................................................... 115°C/W 3mm×3mm MLF™-10L (θJA) ............................... 60°C/W Electrical Characteristics(4) TA = 25°C with VIN =VEN = 3.5V, unless otherwise noted. Bold values indicate –40°C < TJ < +125°C Parameter Condition Min Supply Voltage Range Typ Max Units 5.5 V 1.2 2 A 2.3 Current Limit VFB = 0.7V 0.6 Quiescent Current VFB = 1.1V 320 450 µA EN = 0V 6.0 15 µA 1.0 1.02 V Feedback Voltage 0.98 Output Voltage Line Regulation VOUT = 1V, VIN = 2.3V to 5.5V, ILOAD= 100mA 0.2 % Output Voltage Load Regulation 0mA < ILOAD < 500mA 0.2 % Maximum Duty Cycle VFB = 0.7V Switch On-Resistance ISW = 300mA, VFB = 0.7V 0.72 Ω ISW = –300mA, VFB = 1.1V 0.55 Ω 100 Oscillator Frequency 1.8 Sync Frequency Range 1.8 % 2 2.2 MHz 2.5 MHz SYNC_IN Threshold 1.2 V Sync Minimum Pulse Width 10 ns SYNC_IN Input Current 1 2 µA 0.72 0.96 V Enable Threshold 0.52 Enable Hysteresis 20 Enable Input Current 1 mV 2 µA Overtemperature Shutdown 160 °C Overtemperature Shutdown Hysteresis 20 °C Notes: 1. Exceeding the ABSOLUTE MAXIMUM RATINGS may damage device. 2. Absolute maximum power dissipation is limited by maximum junction temperature where PD(MAX) = (TJ(MAX)–TA) ÷ θJA. 3. The device is not guaranteed to function outside its operating rating. 4. Specification for packaged product only. April 2005 3 M9999-042205 MIC2204 Micrel, Inc. Typical Characteristics 3.5VIN 75 70 3VIN 65 60 80 65 60 50 0 450 500 350 400 250 300 55 1.01 OUTPUT VOLTAGE (V) 1.005 1.0025 1 0.9975 0.995 0.9925 0.99 0 2.32 0.1 0.2 0.3 0.4 OUTPUT CURRENT (A) 0.5 2.5 350 318 IQ (µA) 50 0 0 Frequency vs. Temperature 1.70 1.60 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) M9999-042205 ENABLE THRESHOLD (V) FREQUENCY (MHz) 1.80 1 6 316 314 312 150 2.302 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 2 4 SUPPLY VOLTAGE (V) Quiescent Current vs. Temperature Quiescent Current vs. Supply Voltage 200 2.304 1.90 1.0 VFB = 0V 2.306 2.00 1.5 0 0 0.99 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 100 2.10 vs. Supply Voltage 0.5 250 2.20 100 200 300 400 500 OUTPUT CURRENT (mA) VBIAS Output Voltage vs. Temperature 0.995 IQ (µA) BIAS SUPPLY (V) 50 0 300 2.30 3.3VOUT 55 100 200 300 400 500 OUTPUT CURRENT (mA) 1 2.314 2.40 65 60 2.5VOUT 2.316 2.31 75 70 3.6VIN 5VIN 2.0 2.318 2.308 80 4.2VIN 1.005 Bias Supply vs. Temperature 2.312 90 85 VFB = 0V 1 2 3 4 5 6 SUPPLY VOLTAGE (V) 310 308 306 304 302 300 VIN = 3.6V 298 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) Enable Threshold vs. Supply Voltage 0.9 0.8 Enable On 0.7 0.6 0.5 Enable Off 0.4 0.3 0.2 0.1 0 2.3 2.8 3.3 3.8 4.3 4.8 5.3 SUPPLY VOLTAGE (V) 4 0.9 ENABLE THRESHOLD (V) OUTPUT VOLTAGE (V) Output Voltage vs. Output Current 1.0075 3.6VIN 75 70 OUTPUT CURRENT (mA) 1.01 3.3VIN Efficiency vs. Output Current 95 4.2VIN 90 85 1.8VOUT 150 200 0 55 50 100 VBIAS (V) 85 80 Efficiency vs. Output Current 95 4VIN 50 100 EFFICIENCY (%) 95 90 100 EFFICIENCY (%) Efficiency vs. Output Current EFFICIENCY (%) 100 Enable Threshold vs. Temperature 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 VIN = 3.6V 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) April 2005 MIC2204 Micrel, Inc. Functional Characteristics Disable Transient VOUT 500mV/div VOUT 500mV/div ENABLE 2V/div ENABLE 2V/div Enable Transient VIN = 3.6V VOUT = 1V L = 4.7µH C = 10µF IOUT = 500mA VIN = 3.6V VOUT = 1V L = 4.7µH C = 10µF TIME (40µs/div.) Line Transient Load Transient VIN = 3.6V VOUT = 2V L = 4.7µH C = 4.7µF VOUT 50mV/div VOUT 20mV/div VIN 200mA/div VIN 2V/div TIME (40µs/div.) VOUT = 1V L = 4.7µH C = 10µF IOUT = 500mA TIME (200µs/div.) TIME (20µs/div.) OUTPUT RIPPLE 10mV/div VSW 2V/div Switch Node Output Ripple VIN = 3.6V VOUT = 1V IOUT = 500mA L = 4.7µH C = 10µF X5R TIME (400ns/div.) April 2005 5 M9999-042205 MIC2204 Micrel, Inc. Block Diagram VIN CIN SYNC_OUT Oscillator Ramp Generator SYNC_IN BIAS VIN Internal Supply Error Amplifier PWM Comparator SW Driver VOUT COUT 1.0V EN MIC2204 FB PGND MIC2204 Block Diagram M9999-042205 6 April 2005 MIC2204 Micrel, Inc. Functional Description SYNC_OUT VIN Since SYNC_OUT is an open collector output that provides a signal equal to the internal oscillator frequency, multiple MIC2204s to be connected together in a master-slave configuration for frequency matching of the converters. A typical 10kΩ is recommended for a pull-up resistor. VIN provides power to the output and to the internal bias supply. The supply voltage range is from 2.3V to 5.5V. A minimum 1µF ceramic is recommended for bypassing the input supply. BIAS Enable The bias supply is an internal 2.3V linear regulator that supplies the internal biasing voltage to the MIC2204. A 10nF ceramic capacitor is required on this pin for bypassing. Do not use the BIAS pin as a supply. The BIAS pin was designed to supply internal power and not external circuitry. The enable pin provides a logic level control of the output. In the off state, supply current of the device is greatly reduced (typically 6.5µA). Also, in the off state, the output drive is placed in a “tri-stated” condition, where both the high-side P-Channel MOSFET and the low-side N-Channel are in an off or non-conducting state. Do not drive the enable pin above the supply voltage. Feedback The feedback pin provides the control path to control the output. A resistor divider connecting the feedback to the output is used to adjust the desired output voltage. Refer to the “Feedback” material in the “Applications Information” section for more detail. SYNC_IN SYNC_IN enables the ability to change the fundamental switching frequency. The SYNC_IN frequency has a minimum frequency of 1.8MHz and a maximum sync frequency of 2.5MHz. Careful attention should be paid to not driving the SYNC_IN pin greater than the supply voltage. While this will not damage the device, it will cause improper operation. MIC2204 “Master” VIN SW BIAS 10kΩ SYNC_IN SYNC_OUT FB MIC2204 “Slave” VIN SW BIAS SYNC_IN SYNC_OUT FB Figure 1. SYNC_OUT April 2005 7 M9999-042205 MIC2204 Micrel, Inc. The size requirements refer to the area and height requirements that are necessary to fit a particular design. Please refer to the inductor dimensions on their data sheet. Applications Information Input Capacitor A minimum 1µF ceramic is recommended on the VIN pin for bypassing. X5R or X7R dielectrics are recommended for the input capacitor. Y5V dielectrics are not recommended: they lose most of their capacitance over temperature and also become resistive at high frequencies. This reduces their ability to filter out high frequency noise. DC resistance is also important. While DCR is inversely proportional to size, DCR can represent a significant efficiency loss. Refer to the “Efficiency Considerations ” below for a more detailed description. Table 1 below shows a list of recommended 4.7µH inductors by manufacturer, part number and key specifications. Output Capacitor Bias Capacitor The MIC2204 was designed specifically for the use of a 4.7µF ceramic output capacitor. The output capacitor requires either an X7R or X5R dielectric. Y5V and Z5U dielectric capacitors, aside from the undesirable effect of their wide variation in capacitance over temperature, become resistive at high frequencies. Using Y5V or Z5U capacitors will cause instability in the MIC2204. For output voltages less than 1.6V, a 10µF capacitor may be required for stability. See the “Compensation” section for more detail. A small 10nF ceramic capacitor is required to bypass the BIAS pin. The use of low ESR ceramics provides improved filtering for the bias supply. Efficiency Considerations Efficiency is defined as the amount of useful output power, divided by the amount of power consumed. V ×I Efficiency % = OUT OUT × 100 VIN × IIN Total output capacitance should not exceed 15µF. Large values of capacitance can cause current limit to engage during start-up. If larger than 15µF is required, a feed-forward capacitor from the output to the feedback node should be used to slow the start-up time. Inductor Selection Maintaining high-efficiency serves two purposes. It reduces power dissipation in the power supply, reducing the need for heat sinks and thermal design considerations and it reduces consumption of current for battery powered applications. Reduced current draw from a battery increases the devices operating time, critical in handheld devices. Inductor selection will be determined by the following (not necessarily in the order of importance): There are two loss terms in switching converters: DC losses and switching losses. DC losses are simply the power dissipation of I2R. For example, power is dissipated in the highside switch during the on cycle, where power loss is equal to the high-side MOSFET RDSON multiplied by the Switch Current2. During the off cycle, the low-side N-Channel MOSFET conducts, also dissipating power. Device operating current also reduces efficiency. The product of the quiescent (operating) current and the supply voltage is another DC loss. The current required to drive the gates on and off at a constant 2MHz frequency and the switching transitions make up the switching losses. • Inductance • Rated current value • Size requirements • DC resistance (DCR) The MIC2204 is designed for use with a 4.7µH inductor. Maximum current ratings of the inductor are generally given in two methods: permissible DC current and saturation current. Permissible DC current can be rated either for a 40°C temperature rise or a 10% loss in inductance. Ensure the inductor selected can handle the maximum operating current. When saturation current is specified, make sure that there is enough margin that the peak current will not saturate the inductor. H(mm) W(mm) L(mm) DCR(mΩ) 2 3.2 3.2 81 LQH43CN4R7M01 2.6 3.2 4.6 150 Murata LQH32CN4R7M11 2.2 2.7 3.4 195 Coilcraft 1008PS-472M 2.74 3.8 3.8 350 1 5.2 5.8 240 0.8 6.3 5.8 216 Manufacturer P/N Sumida CDRH2D18-4R7 Murata Low Profile TDK LDR5610T-4R7MR90 Sumida CMD4D06 Table 1. Component Selection Table M9999-042205 8 April 2005 MIC2204 Micrel, Inc. Figure 2 shows an efficiency curve. On the non-shaded portion, from 0 to 200mA, efficiency losses are dominated by quiescent current losses, gate drive and transition losses. In this case, lower supply voltages yield greater efficiency in that they require less current to drive the MOSFETs and have reduced input power consumption. EFFICIENCY (%) 100 95 ing output voltage regulation. With a typical gain bandwidth of 200kHz, the MIC2204 is capable of extremely fast transient responses. The MIC2204 is designed to be stable with a 4.7µH inductor and a 4.7µF ceramic (X5R) output capacitor for output voltages greater than 1.6V. For output voltages less than 1.6V, a 10µF capacitor is required. Also, when a feed forward capacitor is used, the gain bandwidth is increased to unity gain. This will also require increasing the output capacitor to 10µF. Efficiency vs. Output Current 90 4.2VIN 85 80 5VIN 3.6VIN Feedback 75 70 The MIC2204 provides a feedback pin to adjust the output voltage to the desired level. This pin connects internally to an error amplifier. The error amplifier then compares the voltage at the feedback to the internal 1V reference voltage and adjusts the output voltage to maintain regulation. To calculate the resistor divider network for the desired output is as follows: 65 60 55 50 0 3.3VOUT 100 200 300 400 500 OUTPUT CURRENT (A) Figure 2. On the shaded region, 200mA to 500mA, efficiency loss is dominated by MOSFET RDSON and inductor losses. Higher input supply voltages will increase the Gate-to-Source threshold on the internal MOSFETs, reducing the internal RDSON. This improves efficiency by reducing DC losses in the device. All but the inductor losses are inherent to the device, making inductor selection even more critical in efficiency calculations. As the inductors are reduced in size, the DC resistance (DCR) can become quite significant. The DCR losses can be calculated as follows: R2 = Where VREF is 1.0V and VOUT is the desired output voltage. A 10kΩ or lower resistor value from the output to the feedback is recommended. Larger resistor values require an additional capacitor (feed-forward) from the output to the feedback. The large high-side resistor value and the parasitic capacitance on the feedback pin (~10pF) can cause an additional pole in the loop. The additional pole can create a phase loss at high-frequency. This phase loss degrades transient response by reducing phase margin. Adding feed-forward capacitance negates the parasitic capacitive effects of the feedback pin. A minimum 1000pF capacitor is recommended for feedforward capacitance. LPD=IOUT2 x DCR From that, the loss in efficiency due to inductor resistance can be calculated as follows: VOUT × IOUT Efficiency Loss = 1± × 100 VOUT × IOUT + LPD Also, large feedback resistor values increase the impedance, making the feedback node more susceptible to noise pick-up. A feed-forward capacitor would also reduce noise pick-up by providing a low impedance path to the output. Efficiency loss due to DCR is minimal at light loads and gains significance as the load is increased. Inductor selection becomes a trade-off between efficiency and size in this case. Compensation When using a feed-forward capacitor, the gain bandwidth of the device reaches unity gain at high-frequency. Therefore, output capacitance will need to be increased to a minimum 10µF. For more information on output capacitor selection for stability, see the “Compensation ” section. The MIC2204 is an internally compensated, voltage-mode buck regulator. Voltage mode is achieved by creating an internal 2MHz ramp signal and using the output of the error amplifier to pulsewidth modulate the switch node, maintain- April 2005 R1 VOUT ± 1 V REF 9 M9999-042205 MIC2204 Micrel, Inc. PWM Operation Synchronization The MIC2204 is a pulsewidth modulation (PWM) controller. By controlling the ratio of on-to-off time, or duty cycle, a regulated DC output voltage is achieved. As load or supply voltage changes, so does the duty cycle to maintain a constant output voltage. In cases where the input supply runs into a dropout condition, the MIC2204 will run at 100% duty cycle. SYNC_IN allows the user to change the frequency from 2MHz up to 2.5MHz or down to 1.8MHz. This controls the fundamental frequency and all the resultant harmonics. Maintaining a predictable frequency creates the ability to either shift the harmonics away from sensitive carrier and IF frequency bands, or to accurately filter out specific harmonic frequencies. The MIC2204 provides constant switching at 2MHz with synchronous internal MOSFETs. The internal MOSFETs include a high-side P-Channel MOSFET from the input supply to the switch pin and an N-Channel MOSFET from the switch pin to ground. Since the low-side N-Channel MOSFET provides the current during the off cycle, a free wheeling Schottky diode from the switch node to ground is not required. Connecting the SYNC_OUT function pin to the SYNC_IN of other MIC2204s will synchronize multiple MIC2204s in a daisy-chain. Synchronizing multiple MIC2204s means that regulators will run at the same fundamental frequency, resulting in matched harmonic frequencies and simplifying design for sensitive communication equipment. PWM control provides fixed frequency operation. By maintaining a constant switching frequency, predictable fundamental and harmonic frequencies are achieved. Other methods of regulation, such as burst and skip modes, have frequency spectrums that change with load and can interfere with sensitive communication equipment. M9999-042205 10 April 2005 MIC2204 Micrel, Inc. Package Information 3.15 (0.122) 2.85 (0.114) DIMENSIONS: MM (INCH) 4.90 BSC (0.193) 3.10 (0.122) 2.90 (0.114) 1.10 (0.043) 0.94 (0.037) 0.30 (0.012) 0.15 (0.006) 0.26 (0.010) 0.10 (0.004) 0.15 (0.006) 0.05 (0.002) 0.50 BSC (0.020) 6° MAX 0° MIN 0.70 (0.028) 0.40 (0.016) 10-Pin MSOP (MM) DIMENSIONS: 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. 2 2 3.00 BSC. 3 1.15 +0.15 –0.15 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 0.01 +0.04 –0.01 0.50 BSC. 0.50 BSC. TERMINAL TIP ODD TERMINAL SIDE EVEN TERMINAL SIDE 10-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