M MCP1601 500 mA Synchronous BUCK Regulator Features Description • • • • The MCP1601 is a fully integrated synchronous BUCK (step down) DC/DC converter for battery powered systems. With an input operating range of 2.7V to 5.5V, the MCP1601 is ideal for applications being powered by one single cell Li-Ion, 2 to 3 cell NiMH, NiCd or alkaline sources. Output voltages can range from 0.9V to VIN to accommodate a wide range of applications. Efficiency can exceed 92% while operating at 750 kHz with load current capability up to 500 mA. The MCP1601 is used to minimize space, cost and wasted energy. • • • • • • • • • • • Input Range of 2.7V to 5.5V 3 Operating Modes: PWM, PFM and LDO Integrated BUCK and Synchronous Switches Ceramic or Electrolytic Input/Output Filtering Capacitors 750 kHz Fixed Switching Frequency Oscillator Synchronization to 1 MHz PWM Mode Auto-Switching from PWM/PFM Operation 100% Duty Cycle Capable for Low Input Voltage 500 mA Continuous Output Current Capability Integrated Under-Voltage Lock-Out Protection Integrated Over-Temperature Protection Integrated Soft Start Circuitry Low Output Voltage Capability to 0.9V Temperature Range: -40°C to +85ºC Small 8-Pin MSOP Package Applications • • • • • • Low Power Handheld CPUs and DSPs Cellular Phones Organizers and PDAs Digital Cameras +5V or +3.3V Distributed Voltages USB Powered Devices Package Type 8-Pin MSOP VIN 1 8 LX SHDN 2 7 PGND FB 3 6 VOUT AGND 4 5 SYNC/PWM MCP1601 2003 Microchip Technology Inc. The PWM mode switching frequency is internally set to a fixed 750 kHz allowing the use of low profile, surface mount inductors and ceramic capacitors while maintaining a typical efficiency of 92%. The MCP1601 is capable of three distinct operating modes: PWM, PFM and Low Drop Out. When operating in PWM (pulse width modulation) mode, the DC/DC converter switches at a single high frequency determined by either the internal 750 kHz oscillator or external synchronization frequency. For applications that operate at very light to no load for extended periods of time, the MCP1601 is capable of operating in PFM (pulse frequency modulation mode) to reduce the number of switching cycles/sec and consume less energy. The third mode of operation (LDO mode) occurs when the input voltage approaches the output voltage and the BUCK duty cycle approaches 100%. The MCP1601 will enter a low drop out mode and the high-side P-Channel BUCK switch will saturate, providing the output with the maximum voltage possible. The MCP1601 has integrated over-current protection, over-temperature protection and UVLO (Under Voltage Lockout) to provide for a fail safe solution with no external components. The MCP1601 is available in the 8-pin MSOP package, with an operating temperature range of -40°C to +85°C. DS21762A-page 1 MCP1601 Typical Application Typical Application (2.7V to 4.2V) MCP1601 1 VIN 2 SHDN Input Voltage 2.7V-4.2V CIN 10 µF 3 FB 4 AGND VOUT Range 1.2V to 3.3V IOUT = 0 mA to 400 mA L Range 10 µH to 22 µH 10 µH LX 8 COUT 10 µF PGND 7 VOUT 6 SYNC/ 5 PWM COUT Range 10 µF to 47 µF R1 250 kΩ (for 1.8V) C1 47 pF R2 200 kΩ Functional Block Diagram VIN UVLO Internal Circuit Enable SHDN 10 pF FB 3 MΩ 0.8V 800 kΩ 12 pF RCOMP C COMP Enable Out Duty Clamp Cycle Internal Band Gap Reference Buffered 0.8V Output + VREF - Soft Start ISENSEP EA + + - AGND Duty Cycle Clamp 10% - 90% PWM Latch R Feedforward Oscillator K*VIN OUT SQW LX Inset Timing S ISENSEN ISENSEP VREF VOUT - PFM Comparator PFM Mode Timing PGND + VREF - PGND ISENSEN AGND VREF - SYNC/PWM AGND DS21762A-page 2 2003 Microchip Technology Inc. MCP1601 1.0 ELECTRICAL CHARACTERISTICS PIN FUNCTION TABLE NAME Absolute Maximum Ratings † VIN - AGND ......................................................................6.0V SHDN, FB, SYNC/PWM, VOUT ..... (AGND-0.3V) to (VIN+0.3V) LX to PGND................................................ -0.3V to (VIN+0.3V) PGND to AGND .................................................. -0.3V to +0.3V Output Short Circuit Current .................................continuous Storage temperature .....................................-65°C to +150°C Ambient Temp. with Power Applied ................-40°C to +85°C Operating Junction Temperature...................-40°C to +125°C ESD protection on all pins ..................................................≥ 4 kV † Notice: Stresses above those listed under “Maximum ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. FUNCTION VIN Input Source Voltage SHDN Device Shutdown Pin FB Output Voltage Feedback Input AGND Analog Ground VOUT Sensed Output Voltage SYNC/PWM Synchronous Clock input or PWM/ PFM select PGND Power Ground LX Output Inductor Node ELECTRICAL SPECIFICATIONS Electrical Specifications: Unless otherwise indicated, VIN=4.2V, VOUT=1.8V, ILOAD = 10 mA, TA=-40°C to +85°C. Parameters Sym Min Typ Max Units Conditions VIN 2.7 — 5.5 V Shutdown Current I(VIN) — 0.05 1.0 µA Shutdown Mode (SHDN = GND) PFM Mode Current I(VIN) — 119 180 µA SYNC/PWM = GND, PFM Mode (ILOAD = 0 mA) Internal Oscillator Frequency FOSC 650 750 850 kHz SYNC/PWM = VIN External Oscillator Capture Range FSYNC 850 — 1000 kHz FSYNC > FOSC FSYN-FALL 10 — 90 % FSYNC = 1 MHz RDSon P-CHANNEL RDSon-P — 500 — mΩ IP=100 mA, TA=+25°C, VIN=4.2V RDSon N-CHANNEL RDSon-N — 500 — mΩ IN=100 mA, TA=+25°C, VIN =4.2V VDROPOUT — 250 — mV VOUT = 2.7V, ILOAD = 300 mA, TA=+25°C, VDROPOUT=97%VOUT ILX -1.0 — 1.0 µA SHDN = 0V, VIN = 5.5V, LX = 0V, LX = 5.5V IPEAK-PWM — 1.0 — A PWM Mode, SYNC/PWM = VIN, TA = +25°C Power Input Requirements Voltage ILOAD = 0 mA to 500 mA Oscillator Section External Oscillator Duty Cycle Internal Power Switches Dropout Voltage Pin Leakage Current Output PWM Mode Peak Current Limit Output Voltage Output Voltage Range Reference Feedback Voltage VOUT 0.9 — VIN V VFB 0.78 0.8 0.82 V IVFB — 0.1 — nA Line Regulation VLINE-REG — 0.1 — %/V Load Regulation VLOAD-REG — 1.5 — % VIN = 3.6V, ILOAD = 0 mA to 300 mA TSTART — 0.5 — ms PWM Mode, SYNC/PWM=VIN Feedback Input Bias Current Start-Up Time 2003 Microchip Technology Inc. VIN=2.7V to 5.5V, ILOAD=10 mA DS21762A-page 3 MCP1601 ELECTRICAL SPECIFICATIONS (CONTINUED) Electrical Specifications: Unless otherwise indicated, VIN=4.2V, VOUT=1.8V, ILOAD = 10 mA, TA=-40°C to +85°C. Parameters Sym Min Typ Max Units — UVLO 2.4 890 — mA — 2.7 V UVLO-HYS TSHD — 190 — mV — 160 — °C TSHD-HYS — 10 — °C Logic Low Input VIN-HIGH — — 15 % of VIN Logic High Input VIN-HIGH 45 — — % of VIN IIN-LK — — 0.1 µA Conditions Protection Features Average Short Circuit Current Under-Voltage Lockout Under-Voltage Lockout Hysteresis Thermal Shutdown Thermal Shutdown Hysteresis RLOAD < 1 ohm For VIN decreasing Interface Signals (SHDN, SYNC/PWM) Input Leakage Current TEMPERATURE SPECIFICATIONS Electrical Specifications: Unless otherwise noted, all parameters apply at VDD = 2.7V to 5.5V Parameters Symbol Min Typ Max Units Specified Temperature Range TA -40 — +85 °C Operating Junction Temperature Range TJ -40 — +125 °C Storage Temperature Range TA -65 — +150 °C θJA — 208 — °C/W Conditions Temperature Ranges Thermal Package Resistances Thermal Resistance, 8 Pin MSOP DS21762A-page 4 Single-Layer SEMI G42-88 Board, Natural Convection 2003 Microchip Technology Inc. MCP1601 2.0 TYPICAL PERFORMANCE CURVES Note: The graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. The performance characteristics listed herein are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified operating range (e.g., outside specified power supply range) and therefore outside the warranted range. 100 VOUT = 1.2V Auto PWM/PFM Efficiency (%) 90 80 70 VIN = 3.6V VIN = 4.2V 60 VIN = 2.7V 50 40 0 100 200 300 400 PFM Mode Quiescent Current (µA) Note: Unless otherwise indicated, VIN = 4.2V, VOUT = 1.8V, L = 10 µH, COUT= 10 µF (X5R Ceramic), CIN = 10 µF (X5R Ceramic), SYNC/PWM=VIN. 130 VOUT = 1.8V PFM Mode ILOAD = 0 TA = + 25°C 120 TA = + 85°C TA = + 0°C 110 TA = - 40°C 100 500 2.7 3.1 3.5 Load Current (mA) Efficiency vs. Load Current 110 VOUT = 1.8V Auto PWM/PFM Efficiency (%) 100 90 80 VIN = 4.2V VIN = 3.6V 70 VIN = 2.7V 60 50 0 100 200 300 400 780.0 740.0 TA = + 125°C 720.0 TA = + 25°C 700.0 680.0 3.1 90 VIN = 5.0V 80 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) FIGURE 2-5: Input Voltage. VIN = 5.5V 70 60 Oscillator Frequency vs. 1.300 VOUT = 3.3V Auto PWM/PFM VIN = 4.5V 5.5 TA = - 40°C 2.7 VOUT = 1.2V Auto PWM/PFM 1.275 Output Voltage (V) Efficiency (%) 100 5.1 760.0 500 Efficiency vs. Load Current 110 4.7 TA = 0°C ILOAD = 10 mA Forced PWM Mode Load Current (mA) FIGURE 2-2: (VOUT = 1.8V). 4.3 FIGURE 2-4: PFM Mode Quiescent Current vs. Input Voltage. Internal Oscillator Frequency (kHz) FIGURE 2-1: (VOUT = 1.2V). 3.9 Input Voltage (V) 1.250 1.225 VIN = 3.6V VIN = 2.7V 1.200 1.175 1.150 VIN = 4.2V 1.125 50 1.100 0 100 200 300 400 500 0 FIGURE 2-3: (VOUT = 3.3V). Efficiency vs. Load Current 2003 Microchip Technology Inc. 100 200 300 400 500 Load Current (mA) Load Current (mA) FIGURE 2-6: Current. Output Voltage vs. Load DS21762A-page 5 MCP1601 Note: Unless otherwise indicated, VIN = 4.2V, VOUT = 1.8V, L = 10 µH, COUT= 10 µF (X5R Ceramic), CIN = 10 µF (X5R Ceramic), SYNC/PWM=VIN. Output Votlage (V) VIN = 2.7V 1.800 VOUT = 1.8V Auto PWM/PFM 1.780 1.760 VIN = 3.6V 1.740 VIN = 4.2V 1.720 1.700 LX Leakage Current (nA) 4.5 1.820 VIN = 5.0V 3.0 1.5 Synchronous NChannel BUCK Switch PChannel 0.0 0 100 200 300 400 500 -40 Load Current (mA) Output Voltage (V) FIGURE 2-7: Current. 10 35 60 85 Ambient Temperature (°C) Output Voltage vs. Load 3.35 3.33 3.30 3.28 3.25 3.23 3.20 3.18 3.15 3.13 3.10 -15 FIGURE 2-10: Temperature. Switch Leakage vs. VOUT = 3.3V Auto PWM/PFM VIN = 4.5V VIN = 5.0V VIN = 5.5V 0 100 200 300 400 500 Load Current (mA) FIGURE 2-8: Current. Dropout Voltage (mV) 450 Output Voltage vs. Load FIGURE 2-11: Typical PWM Mode of Operation Waveforms. Dropout = (VIN-VOUT) in mV @ 97% of VOUT 400 350 VOUT = 2.7V 300 250 VOUT = 3.3V 200 150 100 50 0 0 100 200 300 400 500 Load Current (mA) FIGURE 2-9: Input to Output Voltage Differential for 100% Duty Cycle vs. Load Current. DS21762A-page 6 FIGURE 2-12: Typical PFM Mode of Operation Waveforms. 2003 Microchip Technology Inc. MCP1601 Note: Unless otherwise indicated, VIN = 4.2V, VOUT = 1.8V, L = 10 µH, COUT= 10 µF (X5R Ceramic), CIN = 10 µF (X5R Ceramic), SYNC/PWM=VIN. FIGURE 2-13: Typical Startup From Shutdown Waveform. FIGURE 2-16: to PWM). Load Step Response (PFM FIGURE 2-14: Startup From 0V Input. FIGURE 2-17: (Forced PWM). Line Step Response FIGURE 2-15: (Forced PWM). Load Step Response FIGURE 2-18: Mode). Line Step Response (PFM 2003 Microchip Technology Inc. DS21762A-page 7 MCP1601 Note: Unless otherwise indicated, VIN = 4.2V, VOUT = 1.8V, L = 10 µH, COUT= 10 µF (X5R Ceramic), CIN = 10 µF (X5R Ceramic), SYNC/PWM=VIN. FIGURE 2-19: Typical Output Ripple Voltage (Forced PWM Mode). FIGURE 2-21: Synchronization. External Oscillator FIGURE 2-20: Typical Output Ripple Voltage (PFM Mode). DS21762A-page 8 2003 Microchip Technology Inc. MCP1601 3.0 PIN FUNCTIONS TABLE 3-1: 3.5 PIN FUNCTION TABLE Pin Name Function 1 VIN 2 SHDN Shutdown Input 3 FB Feedback Input Input Voltage Analog Ground Return Oscillator Synchronization or PWM/ PFM Select Mode Input (SYNC/PWM) Connect an external oscillator to SYNC/PWM to synchronize. With an external oscillator present, the device is forced into a PWM-only mode of operation. For internal oscillator operation, the SYNC/PWM pin is tied high to operate in a forced PWM-only mode and low for a PWM/PFM mode of operation. 4 AGND 5 SYNC/ PWM 6 VOUT Sensed Output Voltage Input Connect the output voltage directly to VOUT for sensing. 7 PGND Power Ground Return 3.7 8 LX BUCK Inductor Output 3.1 Oscillator Synchronization or PWM/ PFM Select Mode Input Input Voltage (VIN) Connect the unregulated input voltage source to VIN. If the input voltage source is located more than several inches away, or is a battery, a typical input capacitor of 10 µF is recommended. 3.2 Shutdown Input (SHDN) 3.6 Output Voltage Sense (VOUT) Power Ground Return (PGND) Connect all large signal ground returns to PGND. (See Section 5.6, “Printed Circuit Board Layout”, for details). 3.8 BUCK Inductor Connection (LX) Connect LX directly to the BUCK inductor. This pin carries large signal-level currents and all connections should be as short and wide as possible. (See Section 5.6, “Printed Circuit Board Layout”, for details). Connect SHDN to a logic low input to force the device into a shutdown low quiescent current mode. When in shutdown, both the P-Channel and N-Channel switches are turned off, in addition to the internal oscillator and other circuitry. When connected to a logic high input, the device will operate in the selected mode. 3.3 Feedback Input (FB) Connect FB to an external resistor divider to set output voltage regulation. The feedback pin is typically equal to 0.8V. See Section 5.0, “Applications Information”, for details in selecting feedback resistors. 3.4 Analog Ground Return (AGND) Tie all small signal ground returns to AGND. (See Section 5.6, “Printed Circuit Board Layout”, for details). 2003 Microchip Technology Inc. DS21762A-page 9 MCP1601 4.0 DEVICE OPERATION The MCP1601 is a synchronous DC/DC converter with integrated switches. Developed to provide high efficiency across a wide line and load range, the MCP1601 integrates the three modes of operation described below. In addition to three operating modes, the MCP1601 also integrates many features that minimize external circuitry, saving board space and cost. With two external resistors used to set the output voltage, the MCP1601 output is adjustable from 0.9V to VIN. 4.1 Operating Modes The MCP1601 has three distinct modes of operation, with each one optimized for a specific operating condition commonly encountered in handheld portable power applications. 4.1.1 FEEDFORWARD VOLTAGE PULSE WIDTH MODULATION (PWM) MODE The Pulse Width Modulation (PWM) mode of operation is desired when operating from typical to maximum output currents with the proper head room voltage at the input. This mode of operation optimizes efficiency and noise by switching at a fixed frequency. Typical output ripple voltage is less than 10 mV when using a 10 µH inductor and 10 µF ceramic capacitor. The internal operating frequency of the MCP1601 is 750 kHz, nominal. The duty cycle, or “ON” time, of the high-side, integrated, P-Channel MOSFET is determined by the continuous mode BUCK transfer function. For the continuous inductor current case, the duty cycle can be approximated by VOUT/VIN. The integrated high-side BUCK P-Channel switch will conduct for the “on” time. At the end of the “on” time, the high-side P-Channel switch is turned off and the integrated, low-side, NChannel synchronous switch is turned on to freewheel the inductor current. The PWM mode architecture employed in the MCP1601 is a feedforward voltage mode control and feeds the input voltage into the PWM oscillator ramp. This information is used to quickly change the operating duty cycle in the event of a sudden input voltage change. The effects on the output voltage are minimized. To force the MCP1601 into PWM mode, the SYNC/PWM pin should be tied to a logic high. The forced PWM mode should be used for applications that require the fastest transient response from light load to heavy load or applications that require a single switching frequency independent of load. An external oscillator between 850 kHz and 1 MHz can be connected to the SYNC/PWM pin for synchronization to an external clock source. The MCP1601 will always operate in the PWM mode when synchronized to an external oscillator. DS21762A-page 10 4.1.2 PULSE FREQUENCY MODULATION (PFM) MODE The MCP1601 is also capable of operating in a pulse frequency modulation mode. This mode of operation is desired for applications that have very long periods of inactivity and the output current requirement placed on the MCP1601 is very low. By entering the PFM mode of operation, the switching frequency becomes mainly a function of load current and will decrease as the load current decreases. By switching slower, the energy used turning “on” and “off” the high-side P-Channel and low-side N-Channel is reduced, making the PFM mode more efficient with light output load currents. When load activity is encountered, the MCP1601 will automatically switch from the PFM mode to the fixed frequency PWM mode by sensing the increase in load current. The auto PWM/PFM mode is selected by placing a logic low at the SYNC/PWM input pin. If an external clock is used to synchronize the MCP1601 switching frequency, the PFM mode is automatically disabled. To enter the PFM mode of operation, the SYNC/PWM pin must be held to a logic low level and the peak inductor current, sensed internal to the MCP1601, is below the internal PFM threshold for more than 1024 clock cycles. If both of these conditions are met, the MCP1601 will enter the PFM mode. While in the PFM mode, the MCP1601 will disable the low-side N-Channel switch to optimize efficiency at low operating currents. A cycle will begin by turning on the high-side P-Channel switch and will end when the output voltage exceeds a predetermined voltage set point. If the peak inductor current exceeds the internal PFM mode current threshold prior to the output voltage exceeding the voltage set point, the load current has increased and the MCP1601 will automatically switch to PWM operation. The typical hysteresis on the PFM comparator is 6 mV. The typical output ripple voltage is below 40 mV when using a 10 µH inductor and 10 µF ceramic output capacitor when VIN = 4.2V. For proper PFM mode operation, the value of the external inductor and the external capacitor should be the same. For example, when using a 10 µH inductor, a 10 µF capacitor should be used. When using a 22 µH inductor, a 22 µF capacitor should be used. 4.1.3 LOW DROP OUT (LDO) MODE When the input voltage to the MCP1601 is decreasing and approaches the set output voltage level, the duty cycle increases to a maximum of 90% (typically). To continue to regulate the output to as high a voltage as possible, the MCP1601 enters the low drop out mode of operation. In this mode, the high-side P-Channel MOSFET acts like a saturated LDO. This mode allows the operation of the load circuitry down to the minimum input supply that is typical in battery-powered applications. 2003 Microchip Technology Inc. MCP1601 4.2 Cross-Conduction Timing Proper timing between turning on the P-Channel, highside MOSFET and turning off the N-Channel, low-side MOSFET (and vice versa) is critical to obtaining high efficiency. This delay between transitions is what limits the maximum duty cycle obtainable by the MCP1601. The delay between transitions leads to more time when the external inductor current is freewheeling through the internal N-Channel body diode and leads to a decrease in efficiency. If the timing delay is too short and both the internal P-Channel MOSFET and NChannel MOSFET conduct, high peak currents will be observed shooting through the device. This will also reduce the operating efficiency. The MCP1601 inset timing is integrated to optimize efficiency for the entire line and load operating range of the device. 4.3 4.3.1 Integrated Protection Features SHUTDOWN By placing a logic low on the SHDN pin of the MCP1601, the device will enter a low quiescent current shutdown mode. This feature turns off all of the internal bias and drivers within the MCP1601 in an effort to minimize the quiescent current. This feature is popular for battery-operated, portable power applications. The shutdown low quiescent current is typically 1 µA. 4.3.2 4.3.3 INTERNAL SOFT START The MCP1601 completely integrates the soft start function and requires no external components. The soft start time is typically 0.5 ms and is reset during overcurrent and over-temperature shutdown. 4.3.4 OVER-TEMPERATURE PROTECTION The MCP1601 protects the internal circuitry from overtemperature conditions by sensing the internal device temperature and shutting down when it reaches approximately 160°C. The device will shut down, the temperature will cool to approximately 150°C, soft start will be enabled and normal operation will resume with no external circuit intervention. 4.3.5 UNDER-VOLTAGE LOCKOUT Protection from operating at sustained input voltages that are out of range is prevented with the integrated Under-Voltage Lockout feature. When the input voltage dips below 2.5V (typically), the MCP1601 will shutdown and the soft start circuit will be reset. Normal operation will resume when the input voltage is elevated above 2.7V, maximum. This hysteresis is provided to prevent the device from starting with too low of an input voltage. INTERNAL OSCILLATOR AND SYNCHRONIZATION CAPABILITY The internal oscillator is completely integrated and requires no external components. The frequency is set nominally to 750 kHZ in an effort to minimize the external inductor and capacitor size needed for the BUCK topology. In addition to the internal 750 kHz oscillator, the MCP1601 is capable of being synchronized to an external oscillator. The external oscillator frequency must be greater than 850 kHz and less than 1 MHz. For proper synchronization, the duty cycle of the external synchronization clock must be between 10% and 90%. The minimum low voltage level should be below 15% of VIN and the high level of the clock should be above 45% of VIN. Rise and fall time requirements for the external synchronization clock must be faster than 100 ns from 10% to 90%. When synchronizing to an external clock, the MCP1601 will always operate in the PWM mode in an effort to eliminate multiple switching frequency’s and their harmonics. 2003 Microchip Technology Inc. DS21762A-page 11 MCP1601 5.0 APPLICATIONS INFORMATION MCP1601 Application Circuit MCP1601 1 VIN 2 SHDN Input Voltage 2.7V-4.2V CIN 10 µF 3 FB 4 AGND L Range 10 µH to 22 µH 10 µH LX 8 COUT 10 µF PGND 7 VOUT 6 SYNC/ 5 PWM COUT Range 10 µF to 47 µF C1 47 pF 1 MΩ 5.1 R1 250 kΩ (for 1.8V) R2 200 kΩ For VOUT < 1.2V ONLY FIGURE 5-1: VOUT Range 1.2V to 3.3V IOUT = 0 mA to 400 mA Typical Application Circuit. Setting Output Voltage 5.1.1 LEAD CAPACITOR The MCP1601 output voltage is set by using two external resistors for output voltages ≥ 1.2V. For output voltages < 1.2V, a third 1 MΩ series resistor is necessary to compensate the control system. A 200 kΩ resistor is recommended for R2, the lower end of the voltage divider. Using higher value resistors will make the circuit more susceptible to noise on the FB pin, causing unstable operation. Lower value resistors can be used down to 20 kΩ or below, if necessary. Capacitor C1 is used for applications that utilize ceramic output capacitors. To lower the PFM mode ripple voltage, a 47 pf capacitor for C1 is used to couple the output AC ripple voltage to the internal PFM mode comparator. For PWM mode, only applications that use electrolytic capacitors that have 0.2Ω or greater of ESR (Equivalent Series Resistance), C1 is not necessary. The feedback reference voltage for the MCP1601 is typically 0.8V. The equation used to calculate the output voltage is shown below. 5.2.1 EQUATION R1 = R2 × [ ( VOUT ⁄ V FB ) – 1 ] Where: VOUT is the desired output voltage, VFB is the MCP1601 internal feedback reference voltage R1 is the resistor connected to VOUT in the voltage divider R2 is the resistor connected to ground in the voltage divider Example: 5.2 Choosing External Components CAPACITORS The MCP1601 was developed to take full advantage of the latest ceramic capacitor technology, though electrolytic types can be used as well. When selecting the best capacitor for the application, the capacitance, physical size, ESR, temperature coefficient, ripple current ratings (electrolytic) and cost are considered in making the best choice. When selecting ceramic capacitors for COUT, the temperature coefficient of the dielectric should be evaluated. Two dielectrics are recommended as they are stable over a wide temperature range (X5R and X7R). Other dielectrics can be used, but their capacitance should stay within the recommended range over the entire operating temperature range. Desired VOUT = 2.5V VFB = 0.8V R2 = 200 kΩ R1 = 425 kΩ DS21762A-page 12 2003 Microchip Technology Inc. MCP1601 126.96.36.199 Input For all BUCK-derived topologies, the input current is pulled from the source in pulses, placing some burden on the input capacitor. For most applications, a 10 µF ceramic capacitor connected to the MCP1601 input is recommended to filter the current pulses. Less capacitance can be used for applications that have low source impedance. The ripple current ratings for ceramic capacitors are typically very high due to their low loss characteristics. Lower-cost electrolytic capacitors can be used, but ripple current ratings should not be exceeded. 188.8.131.52 Output For BUCK-derived topologies, the output capacitor filters the continuous AC inductor ripple current while operating in the PWM mode. Typical inductor AC ripple current for the MCP1601 is 120 mA peak-to-peak with a 3.6V input, 10 µH inductor for a 1.8V output application. Using an output capacitor with 0.3Ω of ESR, the output ripple will be approximately 36 mV. The recommended range for the output capacitor is from 10 µF (±20%) to 47 µF (±20%). Larger value capacitors can be used, but require evaluation of the control system stability. EQUATION V Ripple = ILRipple × COUTesr The above equation assumes that the output capacitance is large enough so that the ripple voltage (as a result of charging and discharging the capacitor) is negligible and can be used for applications that use electrolytic capacitors with esr > 0.3Ω. The maximum peak inductor current is equal to the maximum DC output current plus 1/2 the peak-to-peak AC ripple current in the inductor. The AC ripple current in the inductor can be calculated using the following relationship. EQUATION VL = L × dI dt Solving for ∆IL: EQUATION ∆IL = ( VL ⁄ L ) × ∆t Where: ∆t is equal to the “on” time of the P-Channel switch and, VL = the voltage across the inductor (VIN - VOUT) Example: VIN = 3.6V VOUT = 1.8V FSW = 750 kHz IOUT(MAX) = 300 mA The approximate “on” time is Duty Cycle (VOUT / VIN) x 1/FSW. equal TON = (1.8V/3.6V) x 1/(750 kHz) TON = 667 ns VL = 3.6V - 1.8V = 1.8V ∆IL = (1.8V/10 µH) x 667 ns ∆IL = 120 mA When using a 10 µF ceramic X5R dielectric capacitor, the output ripple voltage is typically less than 10 mV. IL(PEAK) = 5.2.2 IL(PEAK) = 300 mA + (120 mA) / 2 IL(PEAK) = 360 mA BUCK INDUCTOR There are many suppliers and choices for selecting the BUCK inductor. The application, physical size requirements (height vs. area), current rating, resistance, mounting method, temperature range, minimum inductance and cost all need to be considered in making the best choice. When choosing an inductor for the MCP1601 Synchronous BUCK, there are two primary electrical specifications to consider. 1. 2. Current rating of the inductor. Resistance of the inductor. When selecting a BUCK inductor, many suppliers specify a maximum peak current. to the IOUTMAX + 1/2 ∆IL Many suppliers of inductors rate the maximum RMS (Root Mean Square) current. The BUCK inductor RMS current is dependent on the output current, inductance, input voltage, output voltage and switching frequency. For the MCP1601, the inductor RMS current over the 2.7V to 5.5V input range, 0.9V to 5V output voltage range is no more than 15% higher than the average DC output current for the minimum recommended inductance of 10 µH ±20%. When selecting an inductor that has a maximum RMS current rating, use a simple approximation that the RMS current is 1.2 times the maximum output current. Example: IOUT(MAX) = 300 mA, the inductor should have an RMS rating > 360 mA (1.2 x IOUT(MAX)). 2003 Microchip Technology Inc. DS21762A-page 13 MCP1601 DC resistance is another common inductor specification. The MCP1601 will work properly with inductor DC resistance down to 0Ω. The trade-off in selecting an inductor with low DC resistance is size and cost. To lower the resistance, larger wire is used to wind the inductor. The switch resistance in the MCP1601 is approximately 0.5Ω. Inductors with DC resistance lower than 0.1Ω will not have a significant impact on the efficiency of the converter. 5.3 L and COUT Combinations When selecting the L-COUT output filter components, the inductor value range is limited from 10 µH to 22 µH. However, when using the larger inductor values, larger capacitor values should be used. The following table lists the recommended combinations of L and COUT. TABLE 5-1: Note: L-COUT COMBINATIONS L COUT 10 µH 10 µF to 47 µF 15 µH 15 µF to 47 µF 22 µH 22µF to 47 µF For proper PFM mode operation, the value of the external inductor and the external capacitor should be the same. For example, when using a 10 µH inductor, a 10 µF capacitor should be used. When using a 22 µH inductor, a 22 µF capacitor should be used. 5.4 Passive Component Suppliers TABLE 5-2: Supplier Type Description Murata® Ceramic 10 µF 0805 X5R 6.3V #GRM21BR60J106K Murata® Ceramic 10 µF 1206 X5R 6.3V #GRM319R60J106K Taiyo Yuden™ Ceramic 10 µF 1210 X5R 6.3V JMK325BJ106MD AVX™ Ceramic 10 µF 0805 X5R 6.3V #08056D106MAT4A AVX™ Ceramic 10 µF 1206 X5R 6.3V #12066D106MAT4A Kemet® Ceramic 10 µf 1210 6.3V #C1210C106M9PAC Murata® Ceramic 22 µF 1206 X5R 6.3V GRM31CR60J226ME20B Taiyo Yuden™ Ceramic 22 µF 1210 X5R 6.3V JMK325BJ226MY Note: Taiyo Yuden 1210 is a low profile case (1.15 mm) TABLE 5-3: Supplier ® DS21762A-page 14 CERAMIC CAPACITOR SUPPLIERS ELECTROLYTIC CAPACITOR SUPPLIERS Type Description Kemet Tantalum 47 µF D Case 200 MΩ 10V #T495D476M010AS AVX™ Tantalum 47 µF C Case 300 MΩ 6.3V #TPSC476M006S300 Sprague® Tantalum 47 µF C Case 110 MΩ 16V 594D47X0016C2T Sprague® Tantalum 22 µF B Case 380 MΩ 6.3V 594D226X06R3B2T Sprague® Tantalum 15 µF B Case 500 MΩ 10V 594D156X0010B2T 2003 Microchip Technology Inc. MCP1601 TABLE 5-4: INDUCTOR SUPPLIERS Supplier L Type Area (mm) Height (mm) DC Resistance Max. Current Sumida® 10 µH Unshielded 4.1 mm x 3.8 mm 3.0 mm 230 MΩ 0.76A C32 Sumida® 10 µH Shielded 4.0 mm x 4.0 mm 1.8 mm 160 MΩ 0.66A CDRH3D16 Series Sumida® 10 µH Shielded 5.7 mm x 5.7 mm 3.0 mm 65 MΩ 1.3A CDRH5D28 CT* 10 µH Shielded 7.3 mm x 7.3 mm 3.5 mm 70 MΩ 1.7A CTCDRH73 ® 10 µH Shielded 6.6 mm x 4.5 mm 3.0 mm 75 MΩ 1.0A DS1608 Coilcraft® 15 µH Shielded 6.6 mm x 4.5 mm 3.0 mm 90 MΩ 0.8A DS1608 ® 22 µH Shielded 6.6 mm x 4.5 mm 3.0 mm 110 MΩ 0.7A DS1608 Coilcraft® 10 µH Unshielded Wafer 6.0 mm x 5.4 mm 1.3 mm 300 MΩ 0.60A LPO6013 Coilcraft® 15 µH Unshielded Wafer 6.0 mm x 5.4 mm 1.3 mm 380 MΩ 0.55A LPO6013 Taiyo Yuden™ 10 µH Shielded 5.0 mm x 5.0 mm 2.0 mm 66 MΩ 0.7A NP04SB100M Coilcraft Coilcraft Note: 5.5 CT* = Central Technologies Efficiency Efficiency will be affected by the external component selection and the specific operating conditions for the application. In Section 2.0, “Typical Performance Curves”, there are curves plotted using typical inductors that can be used to estimate the converter efficiency for 1.2V, 1.8V and 3.3V. 5.6 Printed Circuit Board Layout The MCP1601 is capable of switching over 500 mA at 750 kHz. As with all high-frequency, switch mode, power supplies, a good board layout is essential to preventing the noise generated by the power train switching from interfering with the sensing circuitry. The MCP1601 has not demonstrated a sensitivity to layout, but good design practice will prevent undesired results. MCP1601 COUT CIN PGND AGND C1 PGND R1 R2 SILK FIGURE 5-2: AGND Component Placement. When designing a board layout for the MCP1601, the first thing to consider is the physical placement of the external components. In Figure 5-2, SM0805 10 µF ceramic capacitors are used for CIN and COUT. The SM0603 package is used for R1, R2 and C1. The inductor used is the Coilcraft® LPO2506 series low profile (0.047” high). The board outline in this example is 1” x 1”. CIN, L and COUT are positioned around the MCP1601 to make the high current paths as short as possible. 2003 Microchip Technology Inc. DS21762A-page 15 MCP1601 MCP1601 PGND PGND AGND BOT FIGURE 5-3: Top Layer. The top layer of the board layout is shown in Figure 5-3. The power conversion process is made up of two types of circuits. One circuit carries changing large signals (current, voltage), like CIN, COUT, L and the VIN, LX PGND pins of the MCP1601. The other circuitry is much smaller in signal and is used to sense, regulate and control the high-power circuitry. These components are R1, R2, C1 and pins FB, AGND. The top layer is partitioned so that the larger signal connections are short and wide, while the smaller signals are routed away from the large signals. FIGURE 5-4: AGND Bottom Layer. In Figure 5-4, the bottom layer is a partitioned ground plane that connects AGND to PGND near the input capacitor. The large signal current will circulate on the top PGND partition. The lower partition is used for a “quiet” ground, where AGND is connected. The MCP1601 utilizes two ground pins to separate the large signal ground current from the small signal circuit ground. The large signal (“Power Ground”) is labeled “PGND”. The small signal is labeled “Analog Ground” or “AGND”. In Figure 5-3, the PGND and the AGND are kept separate on the top layer. DS21762A-page 16 2003 Microchip Technology Inc. MCP1601 6.0 PACKAGING INFORMATION 6.1 Package Marking Information 8-Lead MSOP XXXXXX YWWNNN Legend: Note: * Example: 1601I 344025 XX...X Customer specific information* YY Year code (last 2 digits of calendar year) WW Week code (Week of January 1 is week ‘01) NNN Alphnumeric traceability code In the event the full Microchip part number cannot be marked on one line, it will be carried over to the next line thus limiting the number of available characters for customer specific information. Standard device marking consists of Microchip part number, year code, week code, and traceability code. 2003 Microchip Technology Inc. DS21762A-page 17 MCP1601 8-Lead Plastic Micro Small Outline Package (MS) (MSOP) E E1 p D 2 B n 1 α A2 A c φ A1 (F) L β Units Number of Pins Pitch Dimension Limits n p Overall Height MILLIMETERS* INCHES MIN MAX NOM MIN NOM 0.65 .026 .044 A 1.18 .038 0.76 .006 0.05 .193 .200 .114 .118 .114 .118 L .016 .035 Foot Angle F φ Lead Thickness c .004 Lead Width B α .010 Mold Draft Angle Top Mold Draft Angle Bottom β Molded Package Thickness A2 .030 Standoff A1 .002 E .184 Molded Package Width E1 Overall Length D Foot Length Footprint (Reference) § Overall Width MAX 8 8 0.86 0.97 4.67 4.90 .5.08 .122 2.90 3.00 3.10 .122 2.90 3.00 3.10 .022 .028 0.40 0.55 0.70 .037 .039 0.90 0.95 1.00 6 0 .006 .008 0.10 0.15 0.20 .012 .016 0.25 0.30 0.40 .034 0 0.15 6 7 7 7 7 *Controlling Parameter § Significant Characteristic Notes: Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed .010" (0.254mm) per side. Drawing No. C04-111 DS21762A-page 18 2003 Microchip Technology Inc. MCP1601 PRODUCT IDENTIFICATION SYSTEM To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office. PART NO. Device X /XX Temperature Range Package Device: MCP1601: 500 mA Synchronous BUCK Regulator MCP1601T: 500 mA Synchronous BUCK Regulator Tape and Reel Temperature Range: I Package: MS = Plastic Micro Small Outline (MSOP), 8-lead Examples: a) MCP1601-I/MS: b) MCP1601T-I/MS: Tape and Reel, 8LD MSOP package. 8LD MSOP package. = -40°C to +85°C Sales and Support Data Sheets Products supported by a preliminary Data Sheet may have an errata sheet describing minor operational differences and recommended workarounds. To determine if an errata sheet exists for a particular device, please contact one of the following: 1. 2. 3. Your local Microchip sales office The Microchip Corporate Literature Center U.S. FAX: (480) 792-7277 The Microchip Worldwide Site (www.microchip.com) Please specify which device, revision of silicon and Data Sheet (include Literature #) you are using. Customer Notification System Register on our web site (www.microchip.com/cn) to receive the most current information on our products. 2003 Microchip Technology Inc. DS21762A-page19 MCP1601 NOTES: DS21762A-page 20 2003 Microchip Technology Inc. Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip's Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property. • Microchip is willing to work with the customer who is concerned about the integrity of their code. • Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as “unbreakable.” Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our products. Attempts to break microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act. Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. No representation or warranty is given and no liability is assumed by Microchip Technology Incorporated with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arising from such use or otherwise. Use of Microchip’s products as critical components in life support systems is not authorized except with express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, under any intellectual property rights. Trademarks The Microchip name and logo, the Microchip logo, KEELOQ, MPLAB, PIC, PICmicro, PICSTART, PRO MATE and PowerSmart are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. FilterLab, microID, MXDEV, MXLAB, PICMASTER, SEEVAL and The Embedded Control Solutions Company are registered trademarks of Microchip Technology Incorporated in the U.S.A. Accuron, dsPIC, dsPICDEM.net, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP, ICEPIC, microPort, Migratable Memory, MPASM, MPLIB, MPLINK, MPSIM, PICC, PICkit, PICDEM, PICDEM.net, PowerCal, PowerInfo, PowerTool, rfPIC, Select Mode, SmartSensor, SmartShunt, SmartTel and Total Endurance are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. Serialized Quick Turn Programming (SQTP) is a service mark of Microchip Technology Incorporated in the U.S.A. All other trademarks mentioned herein are property of their respective companies. © 2003, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved. Printed on recycled paper. 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