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| MCP1612 Single 1A, 1.4 MHz Synchronous Buck Regulator Features * * * * * * * * * * * * * Fixed Switching Frequency: 1.4 MHz Input Operating Voltage Range: 2.7V to 5.5V Integrated Buck and Synchronous Switches Adjustable-Output Voltage Range: 0.8V to 5.0V 100% Duty Cycle Capable for Low Input Voltage Continuous Output Current Capability: 1A Shutdown Control with IQ < 0.01 A (Typ.) Integrated Soft-Start Feature Integrated Undervoltage Lockout (UVLO) Protection Integrated Overtemperature Protection Fast Dynamic Response to Line and Load Steps Small, 8-Pin DFN and MSOP Packages Operating Temperature Range: -40C to +85C Description The MCP1612 is a 1A, 1.4 MHz, fully-integrated, current mode-controlled, synchronous buck regulator. The MCP1612 is packaged in the 8-pin MSOP and space-saving, 3x3 DFN packages. The DFN package also provides a lower thermal resistance package option for high-power, high ambient temperature applications. With an input operating range from 2.7V to 5.5V, the MCP1612 is ideal for applications that are powered by one single-cell Li-Ion, 2- to 3-cell NiMH, NiCd or alkaline sources. The output voltage of the MCP1612 is easily set over the range of 0.8V to 5.0V by using an external resistor divider. The external inductor and output capacitor size are minimized due to an internally-fixed, 1.4 MHz clock being used to set the switching frequency. The fixed clock allows for continuous, fixed-frequency PWM operation over the full load range. The MCP1612 is designed to provide fast dynamic response to sudden changes in input voltage and load current to minimize the necessary amount of external output capacitance. The MCP1612 can be used with ceramic, tantalum or aluminum electrolytic output capacitors. Ceramic capacitors with values as low as 4.7 F can be used to keep the output ripple voltage low. For applications that require better load step performance, the value of the output capacitor can be increased to 47 F. Additional features integrated into the MCP1612 include shutdown capability, soft-start, UVLO, overcurrent and overtemperature protection. Applications * * * * * * * * * * Network Interface Cards Portable Computers Set-Top Boxes DSL Modems and Routers USB-Powered Devices GBIC Modules High-Speed Data System Bus Termination Medical Instruments Cellular/GSM/PHS Phones +5V or +3.3V Distributed Voltages Package Types 8-Lead DFN VIN 1 VCC 2 SHDN 3 COMP 4 8 LX 7 PGND 6 AGND 5 FB 8-Lead MSOP VIN 1 VCC 2 SHDN 3 COMP 4 8 LX 7 PGND 6 AGND 5 FB (c) 2005 Microchip Technology Inc. DS21921B-page 1 MCP1612 Functional Block Diagram VCC Undervoltage Lockout (UVLO) Slope Comp. + + UVLO VIN ISENSE P-Channel Peak Current Limit Disable INSET Circuit IN PDRV LX NDRV Comp VREF FB - gm + SoftStart Disable Disable 1.4 MHz Clock LeadingEdge Blank VREF Peak Current Limit PGND PGND VCC VCC A 1.2V VBG UVLO Disable SHDN AGND 0.8V AGND AGND Thermal Shutdown DS21921B-page 2 (c) 2005 Microchip Technology Inc. MCP1612 Typical Application Circuit MCP1612 3.3V to 1.2V Synchronous Buck Converter 3.3 VIN 10% CIN 10 F Ceramic 10 1 VIN Lx 8 L = 3.3 H 1.2V VOUT @ 1A COUT 10 F Ceramic 100 k MCP1612 PGND AGND 7 6 2 CBYP 0.1 F Ceramic VCC 3 ON OFF SHDN 200 k 4 Comp FB 5 25 k 1000 pF (c) 2005 Microchip Technology Inc. DS21921B-page 3 MCP1612 1.0 ELECTRICAL CHARACTERISTICS 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. Absolute Maximum Ratings VIN - AGND .......................................................................6.0V (SHDN, FB, VCC, Comp ........... (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 .....................................-65C to +150C Ambient Temp. with Power Applied.................-40C to +85C Operating Junction Temperature...................-40C to +125C ESD protection on all pins (HBM) ....................................... 4 kV ESD protection on all pins (MM)......................................... 300V DC CHARACTERISTICS Electrical Specifications: Unless otherwise noted, VIN = VCC = VSHDN = 3.3V, VOUT = 1.8V, CIN = COUT = 10 F, L = 3.3 H, ILOAD = 100 mA, TA = +25C. Boldface specifications apply over the TA range of -40C to +85C. Parameters Input Voltage Input Operating Voltage Input Shutdown Current Input Quiescent Current Oscillator Characteristics Internal Oscillator Frequency Internal Power Swicthes RDSon P-Channel RDSon N-Channel LX Pin Leakage Current Positive Current Limit Threshold Negative Current Limit Threshold Feedback Characteristics Transconductance from FB to COMP Output Voltage Output Voltage Range Reference Feedback Voltage Feedback Input Bias Current Line Regulation Load Regulation Note 1: VOUT VFB IVFB VLINE-REG VLOAD-REG 0.8 0.78 -- -- -- -- 0.8 1 0.15 0.25 VIN 0.82 -- 0.5 -- V V nA %/V % VIN = 2.7V to 5.5V, ILOAD = 100 mA VIN = 4.2V, ILOAD = 100 mA to 1A gm 35 62 90 A/V RDSon-P RDSon-N ILX +ILX(MAX) -ILX(MAX) -- -- -1 -- -- 300 300 -- 2.3 -1.4 -- -- 1 -- -- m m A A A IP = 250 mA IN = 250 mA SHDN = 0V, VIN = 5.5V, LX = 0V, LX = 5.5V FOSC 1.2 1.4 1.6 MHz VIN I(VIN) I(VIN) 2.7 -- -- -- 0.01 5 5.5 1 7 V A mA Shutdown mode (SHDN = GND) ILOAD = 0 mA Sym Min Typ Max Units Conditions 2: The integrated MOSFET switches have an integral diode from the LX pin to VIN and from LX to PGND. In cases where these diodes are forward-biased, the package power dissipation limits must be adhered to. Thermal protection is not able to regulate the junction temperature for these cases. UVLO is specified for a falling VIN. Once the UVLO is activated, the UVLO-HYS must be overcome before the device will return to operation. DS21921B-page 4 (c) 2005 Microchip Technology Inc. MCP1612 DC CHARACTERISTICS (CONTINUED) Electrical Specifications: Unless otherwise noted, VIN = VCC = VSHDN = 3.3V, VOUT = 1.8V, CIN = COUT = 10 F, L = 3.3 H, ILOAD = 100 mA, TA = +25C. Boldface specifications apply over the TA range of -40C to +85C. Parameters Protection Features Undervoltage Lockout Undervoltage Lockout Hysteresis Thermal Shutdown Thermal Shutdown Hysteresis Interface Signal (SHDN) Logic-High Input Logic-Low Input Note 1: VIN-HIGH VIN-LOW 45 -- -- -- -- 15 % of VIN % of VIN UVLO UVLO-HYS TSHD TSHD-HYS 2.4 -- -- -- 2.55 200 160 9 2.7 -- -- -- V mV C C Note 1 Note 2 Sym Min Typ Max Units Conditions 2: The integrated MOSFET switches have an integral diode from the LX pin to VIN and from LX to PGND. In cases where these diodes are forward-biased, the package power dissipation limits must be adhered to. Thermal protection is not able to regulate the junction temperature for these cases. UVLO is specified for a falling VIN. Once the UVLO is activated, the UVLO-HYS must be overcome before the device will return to operation. TEMPERATURE SPECIFICATIONS Electrical Specifications: VIN = 3.0V to 5.5V, FOSC = 1 MHz with 10% Duty Cycle, CIN = 0.1 F. TA = -40C to +125C. Parameters Temperature Ranges Storage Temperature Range Maximum Junction Temperature Operating Junction Temperature Range Thermal Package Resistances Thermal Resistance, 8L-MSOP JA JA -- -- 208 41 -- -- C/W C/W Typical 4-layer board interconnecting vias Typical 4-layer board interconnecting vias TA TJ TA -65 -- - 40 -- -- -- +150 +150 + 125 C C C Continuous Transient Only Continuous Operation Sym Min Typ Max Units Conditions Thermal Resistance, 8L-DFN (c) 2005 Microchip Technology Inc. DS21921B-page 5 MCP1612 2.0 Note: TYPICAL PERFORMANCE CURVES 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. Note: Unless otherwise indicated, VIN = VCC = VSHDN = 3.3V, COUT = CIN = 10 F, L = 3.3 H, ILOAD = 100 mA, TA = +25C. Boldface specifications apply over the TA range of -40C to +85C. 100 90 80 70 60 50 40 30 20 10 0 0.50 VOUT = 2.5V Dropout Voltage (V) VOUT = 2.7V 0.40 0.30 VOUT = 3.3V Efficiency (%) VOUT = 1.2V VOUT = 1.8V 0.20 0.10 0.00 VIN = 3.3V 10 100 Load Current (mA) 1000 0 200 400 600 800 1000 Load Current (mA) FIGURE 2-1: VIN = 3.3V. 100 90 80 70 60 50 40 30 20 10 0 10 Efficiency vs. Load Current, FIGURE 2-4: Load Current. Input Quiescent Current (mA) 6.5 6.0 5.5 5.0 4.5 4.0 3.5 2.5 3 TA = -40 C o Dropout Voltage vs. VOUT = 3.3V Efficiency (%) TA = +85oC VOUT = 2.5V TA = +25 C o VIN = 5.0V VOUT = 1.8V 100 Load Current (mA) 1000 3.5 4 4.5 5 5.5 Input Voltage (V) FIGURE 2-2: VIN = 5.0V. Change In Output Voltage (mV) Efficiency vs. Load Current, FIGURE 2-5: Input Voltage. 1.42 1.41 1.40 1.39 1.38 1.37 1.36 TA = +85oC Input Quiescent Current vs. Oscillator Frequency (MHz) 0 -0.2 -0.4 -0.6 -0.8 -1 -1.2 VOUT = 3.3V, VIN = 5.0V VOUT = 1.8V, VIN = 3.3V VOUT = 1.2V VIN = 3.3V TA = -40oC TA = +25oC -1.4 0 200 400 600 800 1000 2.5 3 3.5 4 4.5 5 5.5 Load Current (mA) Input Voltage (V) FIGURE 2-3: Load Current. Output Voltage vs. FIGURE 2-6: Input Voltage. Oscillator Frequency vs. DS21921B-page 6 (c) 2005 Microchip Technology Inc. MCP1612 TYPICAL PERFORMANCE CURVES (Continued) Note: Unless otherwise indicated, VIN = VCC = VSHDN = 3.3V, COUT = CIN = 10 F, L = 3.3 H, ILOAD = 100 mA, TA = +25C. Boldface specifications apply over the TA range of -40C to +85C. Start-up from VIN = 0V to 3.3V IOUT = 100 mA to 800 mA VIN = 5.0V VOUT = 3.3V VIN 2.0V/DIV VOUT 100 mV/DIV VOUT 1.0V/DIV 1.0 ms/DIV IOUT 500 mA/DIV VOUT = 1.8V 500 s/DIV FIGURE 2-7: Power-Up from VIN. Start-up from SHDN FIGURE 2-10: Load Transient Response. Line Step Response, VIN = 3.0V to 4.0V SHDN 2.0V/DIV VIN 2.0V/DIV VOUT 50 mV/DIV VOUT 1.0V/DIV 1.0 ms/DIV VOUT = 1.8V IOUT = 800 mA 200 s/DIV VOUT = 1.8V FIGURE 2-8: Power-Up from Shutdown. IOUT = 100 mA to 800 mA FIGURE 2-11: Line Transient Response. Line Step Response, VIN = 4.5V to 5.5V VIN 2.0V/DIV VOUT 200 mV/DIV IOUT 500 mA/DIV VOUT = 1.8V 50 s/DIV VOUT 50 mV/DIV VOUT = 3.3V IOUT = 800 mA 200 s/DIV FIGURE 2-9: Load Transient Response. FIGURE 2-12: Line Transient Response. (c) 2005 Microchip Technology Inc. DS21921B-page 7 MCP1612 TYPICAL PERFORMANCE CURVES (Continued) Note: Unless otherwise indicated, VIN = VCC = VSHDN = 3.3V, COUT = CIN = 10 F, L = 3.3 H, ILOAD = 100 mA, TA = +25C. Boldface specifications apply over the TA range of -40C to +85C. IOUT = 10 mA, VOUT = 1.8V LX 2.0V/DIV VOUT 10 mV/DIV IIND 100 mA/DIV VIN = 3.3V 500 ns/DIV LX 5.0V/DIV VOUT 10 mV/DIV IIND 500 mA/DIV IOUT = 1A, VOUT = 1.8V VIN = 3.3V 500 ns/DIV FIGURE 2-13: Waveform. Low Load Current Switching FIGURE 2-14: Waveform. High Load Current Switching DS21921B-page 8 (c) 2005 Microchip Technology Inc. MCP1612 3.0 MCP1612 PIN DESCRIPTIONS The descriptions of the pins are listed in Table 3-1. TABLE 3-1: Pin No. 1 2 3 4 5 6 7 8 PIN FUNCTION TABLE Name VIN VCC SHDN COMP FB AGND PGND LX Input Voltage Pin Analog Input Voltage Pin Shutdown Control Input Pin Transconductance Amplifier Output Pin Feedback Input Pin Analog Ground Pin Power Ground Pin Buck Inductor Output Pin Function 3.1 Input Voltage Pin (VIN) 3.5 Feedback Pin (FB) Connect the input voltage source to VIN. For normal operation, the voltage on VIN should be between +2.7V and +5.5V. A 10 F bypass capacitor should be connected between VIN and PGND. Connect the output voltage of the buck converter through an external resistor divider to FB to regulate the output voltage. The nominal voltage compared to this input for pulse termination is 0.8V. 3.2 Analog Input Voltage Pin (VCC) 3.6 Analog Ground Pin (AGND) VCC provides bias for internal analog functions. This voltage is derived by filtering the VIN supply. Tie all small-signal ground returns to AGND. Noise on AGND can effect the sensitive internal analog measurements. 3.3 Shutdown Input Pin (SHDN) 3.7 Power Ground Pin (PGND) Connect all large-signal ground returns to PGND. These large-signal traces should have a small loop area and length to prevent coupling of switching noise to sensitive traces. Connect SHDN to a logic-level input in order to turn the regulator on or off. A logic-high (>45% of VIN) will enable the regulator. A logic-low (<15% of VIN) will force the regulator into Shutdown mode. When in shutdown, both the P-channel and N-channel switches are turned off. 3.8 3.4 Compensation Pin (COMP) COMP is the internal transconductance amplifier output pin. External compensation is connected to COMP for control-loop stabilization. Buck Inductor Output Pin (LX) Connect LX directly to the buck inductor. This pin carries large signal-level currents; all connections should be made as short as possible. (c) 2005 Microchip Technology Inc. DS21921B-page 9 MCP1612 4.0 4.1 DETAILED DESCRIPTION Device Overview 4.4 Current Limit The MCP1612 is a 1A synchronous buck converter switching at 1.4 MHz to minimize external component size and cost. While utilizing a fixed-frequency Current mode architecture, the MCP1612 provides fast response to sudden load changes, as well as overcurrent protection in the event of a shorted load. The input voltage range is 2.7V to 5.5V, while the output voltage is adjustable by properly setting an external resistor divider and can range from 0.8V to VIN. Integrated soft-start, UVLO and overtemperature protection minimize external circuitry and component count. Cycle-by-cycle current limit is used to protect the MCP1612 from being damaged when an external short circuit is applied. The typical peak current limit is 2.3A. If the sensed inductor current reaches the 2.3A limit, the P-channel MOSFET is turned off, even if the output voltage is not in regulation. 4.5 Soft-Start 4.2 Current Mode Control Scheme The MCP1612 incorporates a Peak Current mode control scheme. Peak Current mode is used to obtain high gain in the PWM control loop for very fast response to dynamic line and load conditions. With both the P-channel and N-channel MOSFETs turned off, the beginning of a cycle occurs on the negative edge of the internal 1.4 MHz oscillator, the P-channel MOSFET turns on and current ramps up into the buck inductor. The inductor current is sensed and tied to one input of a high-speed comparator. The other input of the high-speed comparator is the error amplifier output. This is the amplified difference between the internal 0.8V reference and the divided-down VOUT signal at the FB pin of the MCP1612. When the sensed inductor current ramps up to the point that is equal to the amplified error signal, the high-speed comparator output switches states and the P-channel MOSFET is turned off until the beginning of the next clock cycle and the N-channel is turned on. The width of the pulse (or duty cycle) is ideally determined by the VOUT/VIN ratio of the DC/DC converter. The actual duty cycle is slightly larger to account for the non-ideal losses of the integrated MOSFET switches and the losses in the external inductor. During normal power-up, as VIN rises above the UVLO protection setting (or, in the case of a logic-low to logichigh transition on the shutdown pin), the rise time of the MCP1612 output voltage is controlled by the soft-start feature. This is accomplished by allowing the output of the error amplifier to slowly rise. This feature prevents the output voltage from overshooting the desired value and the sudden inrush of current, depleting the input capacitors and causing a large dip in input voltage. This large dip in the input voltage can trip the UVLO threshold, causing the converter to shut down prior to reaching steady-state operation. 4.6 Undervoltage Lockout (UVLO) The UVLO feature uses a comparator to sense the input voltage level (VIN). If the input voltage is lower than the voltage necessary to properly operate the MCP1612, the UVLO feature will hold the converter off. When VIN rises above the necessary input voltage, the UVLO is released and soft-start begins. For the MCP1612, the UVLO protection threshold is at a maximum of 2.7V. Hysteresis is built into the UVLO circuit to compensate for input impedance. For example, if there is any resistance between the input voltage source and the converter (once it starts), there will be a voltage drop at the converter input equal to IIN x RIN. The typical hysteresis for the MCP1612 is 200 mV. 4.7 Overtemperature Protection 4.3 Low-Dropout Operation The MCP1612 is capable of operating over a wide range of input voltages. The PWM architecture allows for the P-channel MOSFET to achieve 100% duty cycle operation for applications that have minimal input voltage headroom. During 100% Duty Cycle mode, the output voltage (VOUT) is equal to the Output Current (IOUT) x Resistance (P-channel RDSON + RINDUCTOR). The MCP1612 has an integrated overtemperature protection circuit that monitors the device junction temperature and shuts the device off if the junction temperature exceeds the typical 160C threshold. If the overtemperature threshold is reached, the soft-start is reset so that, when the junction temperature cools to approximately 151C, the device will automatically restart and the output voltage will not overshoot. 4.8 Shutdown Input Operation The SHDN pin is used to turn the MCP1612 on and off. When the SHDN pin is tied low, the MCP1612 is off. When tied high, the MCP1612 will be enabled and begin operation as long as the input voltage is not below the UVLO threshold. DS21921B-page 10 (c) 2005 Microchip Technology Inc. MCP1612 5.0 APPLICATION CIRCUITS/INFORMATION MCP1612 3.3V to 1.2V Synchronous Buck Converter 3.3VIN 10% CIN 10 F Ceramic 10 1 VIN Lx 8 L = 3.3 H 1.2V VOUT @ 1A COUT 10 F Ceramic 100 k MCP1612 PGND AGND 7 6 2 CBYP 0.1 F Ceramic VCC 3 ON OFF SHDN 200 k 4 Comp FB 5 25 k 1000 pF FIGURE 5-1: Typical Application Circuit. resistors will make the circuit more susceptible to noise on the FB pin. Lower-value resistors can be used, if necessary. Equation 5-1, used to calculate the output voltage, is shown below. 5.1 Typical Applications The MCP1612 buck controller can be used in several different applications where a voltage that is lower than the supply voltage is required. Its small size, low cost and high efficiency make the MCP1612 a good choice for densely-packaged applications. The input voltage range, low-dropout voltage and low shutdown current make this part perfectly suited for battery-powered applications. EQUATION 5-1: V OUT R1 = R 2 x ------------- - 1 V FB Where: VOUT = desired output voltage VFB = MCP1612 internal reference voltage R1 = top resistor value R2 = bottom resistor value For this example: VOUT = 1.2V VFB = 0.8V R2 = 200 k R1 = 100 k The MCP1612 is capable of a 15% duty cycle. Instability may result when the duty cycle is below 15%. If less than 15% duty cycle operation is needed, care must be taken to ensure stable operation. 5.2 Design Example The step-by-step design of a buck converter with the following parameters is presented to illustrate how easy the MCP1612 is to use. Input voltage = 3.3V Output voltage = 1.2V Output current = 0A to 1A Switching frequency = 1.4 MHz 5.2.1 SETTING OUTPUT VOLTAGE The output voltage of the MCP1612 is set by using an external resistor-divider network. The voltage present at FB is internally compared to a 0.8V reference voltage. A 200 k resistor is recommended for R2, the lower-end of the voltage divider. Using higher-value (c) 2005 Microchip Technology Inc. DS21921B-page 11 MCP1612 5.2.2 BUCK INDUCTOR There are many requirements that need to be satisfied when selecting the buck inductor. The application, physical size, current rating, resistance, mounting method, supplier, temperature range, minimum inductance and cost all need to be considered. Many suppliers specify the maximum peak current that an inductor can handle before magnetic saturation occurs. The peak current is equal to the maximum DC output current, plus one-half the peak-to-peak AC ripple current. When the P-channel MOSFET is on, the current in the buck inductor is ramped up. The voltage across the inductor, the inductance and the MOSFET on-time are required to determine the peak-to-peak ripple current. When operating in Continuous Current mode, the ontime of the P-channel MOSFET is determined by multiplying the duty cycle by the switching period. The following equation can be used to determine the duty cycle. The value of the buck inductor is chosen to be 3.3 H. The AC ripple current is controlled by the size of the buck inductor. The value of the inductor will therefore need to be raised so that the converter operates in Continuous Conduction mode. Calculation of the buck inductor current rating follows. VIN = 3.3V VOUT = 1.2V FSW = 1.4 MHz IOUT(MAX) = 1A TON = (1.2V/3.3V) x (1/1.4 MHz) TON = 260 ns VL = (3.3V - 1.2V) = 2.1V IL = (2.1V/3.3 H) x 260 ns IL = 165 mA IL(PEAK) = IOUT(MAX) + 1/2 IL IL(PEAK) = 1A + (165 mA)/2 IL(PEAK) = 1.08A The inductor selected must have an inductance of 3.3 H at a peak current rating of 1.08A. The DC resistance of the inductor should be as low as is feasibly possible. Extremely low DC resistance inductors are available, though a trade-off between size and cost should be considered. EQUATION 5-2: V OUT DutyCycle = ------------V IN The on-time is then defined as follows. 5.2.3 EQUATION 5-3: T ON Where: FSW = switching frequency The AC ripple current in the inductor can be calculated by the following relationship. 1= DutyCycle x --------F SW OUTPUT CAPACITOR EQUATION 5-4: I L V L = L x -------t Solving for IL yields: The output capacitor is used to filter the inductor AC ripple current and provide storage for load transients. The size and Equivalent Series Resistance (ESR) of the output capacitor determines the amount of ripple voltage present at the output of the converter. When selecting the output capacitor, a design trade-off has to be made between the acceptable ripple voltage and the size/cost of the output capacitor. Ceramic capacitors have very low ESR, but increase in cost with higher values. Tantalum and electrolytic capacitors are relatively inexpensive in higher values, but they also have a much higher ESR. The amount of capacitance needed to obtain the desired ripple voltage is calculated by using the following relationship. EQUATION 5-5: VL I L = ----- x t L Where: VL = voltage across the inductor (VIN - VOUT) t = on-time of the P-channel MOSFET EQUATION 5-6: V C I C = C x ---------t DS21921B-page 12 (c) 2005 Microchip Technology Inc. MCP1612 Solving for C: t C = I C x ---------V C Where: IC = peak-to-peak ripple current t = on-time of P-channel MOSFET VC = output ripple voltage There will also be some ripple voltage caused by the ESR of the capacitor. The ripple is defined as follows. 5.2.6 COMPENSATION COMPONENTS An internal transconductance error amplifier is used to compensate the buck converter. An external resistor (RC) and capacitor (CC), connected between COMP and GND, are all that is needed to provide a highbandwidth loop. Table 5-1 identifies values for RC and CC for standard buck inductor (L) and output capacitor (COUT) values. TABLE 5-1: L 3.3 H 2.2 H RC and CC VALUES COUT 10.0 F 4.7 F RC 25 k 10 k CC 1000 pF 1000 pF EQUATION 5-7: V ESRRIPPLE = ESR x IC 5.3 For this example: IC = 165 mA C = 4.7 F t = 260 ns ESR = 8 m VC = (260 ns x 165 mA)/4.7 F VC = 9.13 mV VESRRIPPLE = 8 m x 165 mA VESRRIPPLE = 1.32 mV VOUT = VC + VESRRIPPLE VOUT = 9.13 mV + 1.32 mV VOUT = 10.45 mV Printed Circuit Board (PCB) Layout The MCP1612 is capable of switching over 1A at 1.4 MHz. As with all high-frequency switching power supplies, good PCB layout techniques are essential to prevent noise generated by the switching power-train from interfering with the sensing circuitry. There are two ground pins (PGND and AGND) on the MCP1612 to separate the large-signal ground current from the small-signal circuit ground. These two grounds should be kept separate, only connecting near the input bulk capacitor. Care must also be taken to minimize the length and loop area of the large signal connections. Components connected to this loop consist of the input bulk capacitor, VIN, PGND and LX pins of the MCP1612, the buck inductor and the output filter capacitor. 5.2.4 INPUT CAPACITOR For the buck topology, the input current is pulled from the source and the input capacitor in pulses. The size of the input capacitor will determine the amount of current pulled from the source. For most applications, a 10 F ceramic capacitor connected between the MCP1612's VIN and PGND is recommended to filter the current pulses. Less capacitance can be used for applications that have low source impedance. The ripple current rating for ceramic capacitors are typically very high due to their low loss characteristics. Low-cost electrolytic capacitors can be used, but their ripple current rating should not be exceeded. 5.2.5 VCC INPUT The VCC input is used to bias the internal MCP1612 circuitry. A 10 resistor is recommended between the unregulated inputs VIN and VCC, along with a 0.1 F capacitor to ground to help isolate the VCC pin from the switching noise. (c) 2005 Microchip Technology Inc. DS21921B-page 13 MCP1612 6.0 6.1 PACKAGING INFORMATION Package Marking Information 8-Lead DFN (3mm x 3mm) Example: XXXX YYWW NNN 1612 I0532 256 8-Lead MSOP Example: XXXXX YWWNNN 1612I 532256 Legend: XX...X Y YY WW NNN e3 * Customer-specific information Year code (last digit of calendar year) Year code (last 2 digits of calendar year) Week code (week of January 1 is week `01') Alphanumeric traceability code Pb-free JEDEC designator for Matte Tin (Sn) This package is Pb-free. The Pb-free JEDEC designator ( e3 ) can be found on the outer packaging for this package. Note: 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. DS21921B-page 14 (c) 2005 Microchip Technology Inc. MCP1612 8-Lead Plastic Dual-Flat, No-Lead Package (MF) 3x3x0.9 mm Body (DFN) - Saw Singulated D b p n L E EXPOSED METAL PAD (NOTE 2) E2 PIN 1 ID INDEX AREA (NOTE 1) 2 D2 1 TOP VIEW BOTTOM VIEW ALTERNATE EXPOSED PAD CONFIGURATIONS A1 A3 A EXPOSED TIE BAR (NOTE 3) Units Dimension Limits Number of Pins Pitch Overall Height Standoff Contact Thickness Overall Length Exposed Pad Width Overall Width Exposed Pad Length Contact Width Contact Length * Controlling Parameter n p A A1 A3 E E2 D D2 b L .059 .009 .008 .043 .031 .000 MIN INCHES NOM 8 .026 BSC .035 .001 .008 REF. .118 BSC .061 .118 BSC .092 .012 .016 .096 .015 .020 1.50 0.23 0.20 .063 1.09 .039 .002 0.80 0.00 MAX MIN MILLIMETERS* NOM 8 0.65 BSC 0.90 0.02 0.20 REF. 3.00 BSC 1.55 3.00 BSC 2.37 0.30 0.40 2.45 0.37 0.50 1.60 1.00 0.05 MAX Notes: 1. Pin 1 visual index feature may vary, but must be located within the hatched area. 2. Exposed pad varies according to die attach paddle size. 3. Package may have one or more exposed tie bars at ends. BSC: Basic Dimension. Theoretically exact value shown without tolerances. See ASME Y14.5M REF: Reference Dimension, usually without tolerance, for information purposes only. See ASME Y14.5M JEDEC equivalent: M0-229 Drawing No. C04-062 Revised 07-20-05 (c) 2005 Microchip Technology Inc. DS21921B-page 15 MCP1612 8-Lead Plastic Micro Small Outline Package (MS) (MSOP) E E1 p D 2 B n 1 c A A2 F Units Dimension Limits Number of Pins Pitch Overall Height Molded Package Thickness Standoff Overall Width Molded Package Width Overall Length Foot Length Footprint (Reference) Foot Angle Lead Thickness Lead Width Mold Draft Angle Top Mold Draft Angle Bottom n p A A2 A1 E E1 D L F c B .016 .030 .000 MIN L A1 INCHES NOM 8 MAX MIN MILLIMETERS* NOM 8 0.65 BSC .043 .037 .006 0.75 0.00 4.90 BSC 3.00 BSC 3.00 BSC .031 8 .009 .016 15 15 0.40 0 0.08 0.22 5 5 0.60 0.95 REF 8 0.23 0.40 15 15 0.80 0.85 1.10 0.95 0.15 MAX .026 BSC .033 .193 BSC .118 BSC .118 BSC .024 .037 REF 0 .003 .009 5 5 .006 .012 - * Controlling Parameter Notes: Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed .010" (0.254mm) per side. BSC: Basic Dimension. Theoretically exact value shown without tolerances. See ASME Y14.5M REF: Reference Dimension, usually without tolerance, for information purposes only. See ASME Y14.5M JEDEC Equivalent: MO-187 Drawing No. C04-111 Revised 07-21-05 DS21921B-page 16 (c) 2005 Microchip Technology Inc. MCP1612 APPENDIX A: REVISION HISTORY Revision B (September 2005) The following is the list of modifications: 1. 2. 3. 4. 5. Changed pin 6 in Package Types diagram on front page. Removed device qualification note in Package Marking section. Removed device qualification note in Package Outline drawing. Removed device qualification note in Package Identification System section Replaced MSOP and QFN package diagrams. Revision A (December 2004) * Original Release of this Document. (c) 2005 Microchip Technology Inc. DS21921B-page 17 MCP1612 NOTES: DS21921B-page 18 (c) 2005 Microchip Technology Inc. MCP1612 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 Temperature Range /XX Package Examples: a) b) Industrial Temperature, 8LD MSOP package. MCP1612T-ADJI/MS: Tape and Reel Industrial Temperature, 8LD MSOP package. MCP1612-ADJI/MF: Industrial Temperature, 8LD DFN package. MCP1612T-ADJI/MF: Tape and Reel Industrial Temperature, 8LD DFN package. MCP1612-ADJI/MS: Device: MCP1612: Synchronous Buck Regulator MCP1612T: Synchronous Buck Regulator (Tape and Reel) c) d) Temperature Range: I = -40C to +85C Package: MF = Dual Flat, No Lead (3x3mm Body), 8-lead MS = Plastic MSOP, 8-lead (c) 2005 Microchip Technology Inc. DS21921B-page 19 MCP1612 NOTES: DS21921B-page 20 (c) 2005 Microchip Technology Inc. MCP1612 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 provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. Microchip disclaims all liability arising from this information and its use. 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 Microchip intellectual property rights. Trademarks The Microchip name and logo, the Microchip logo, Accuron, dsPIC, KEELOQ, microID, MPLAB, PIC, PICmicro, PICSTART, PRO MATE, PowerSmart, rfPIC, and SmartShunt are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. AmpLab, FilterLab, Migratable Memory, MXDEV, MXLAB, PICMASTER, SEEVAL, SmartSensor and The Embedded Control Solutions Company are registered trademarks of Microchip Technology Incorporated in the U.S.A. Analog-for-the-Digital Age, Application Maestro, dsPICDEM, dsPICDEM.net, dsPICworks, ECAN, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP, ICEPIC, Linear Active Thermistor, MPASM, MPLIB, MPLINK, MPSIM, PICkit, PICDEM, PICDEM.net, PICLAB, PICtail, PowerCal, PowerInfo, PowerMate, PowerTool, rfLAB, rfPICDEM, Select Mode, Smart Serial, SmartTel, Total Endurance and WiperLock are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. 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. (c) 2005, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved. Printed on recycled paper. Microchip received ISO/TS-16949:2002 quality system certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona and Mountain View, California in October 2003. The Company's quality system processes and procedures are for its PICmicro(R) 8-bit MCUs, KEELOQ(R) code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory and analog products. In addition, Microchip's quality system for the design and manufacture of development systems is ISO 9001:2000 certified. (c) 2005 Microchip Technology Inc. DS21921B-page 21 WORLDWIDE SALES AND SERVICE AMERICAS Corporate Office 2355 West Chandler Blvd. Chandler, AZ 85224-6199 Tel: 480-792-7200 Fax: 480-792-7277 Technical Support: http://support.microchip.com Web Address: www.microchip.com Atlanta Alpharetta, GA Tel: 770-640-0034 Fax: 770-640-0307 Boston Westborough, MA Tel: 774-760-0087 Fax: 774-760-0088 Chicago Itasca, IL Tel: 630-285-0071 Fax: 630-285-0075 Dallas Addison, TX Tel: 972-818-7423 Fax: 972-818-2924 Detroit Farmington Hills, MI Tel: 248-538-2250 Fax: 248-538-2260 Kokomo Kokomo, IN Tel: 765-864-8360 Fax: 765-864-8387 Los Angeles Mission Viejo, CA Tel: 949-462-9523 Fax: 949-462-9608 San Jose Mountain View, CA Tel: 650-215-1444 Fax: 650-961-0286 Toronto Mississauga, Ontario, Canada Tel: 905-673-0699 Fax: 905-673-6509 ASIA/PACIFIC Australia - Sydney Tel: 61-2-9868-6733 Fax: 61-2-9868-6755 China - Beijing Tel: 86-10-8528-2100 Fax: 86-10-8528-2104 China - Chengdu Tel: 86-28-8676-6200 Fax: 86-28-8676-6599 China - Fuzhou Tel: 86-591-8750-3506 Fax: 86-591-8750-3521 China - Hong Kong SAR Tel: 852-2401-1200 Fax: 852-2401-3431 China - Qingdao Tel: 86-532-8502-7355 Fax: 86-532-8502-7205 China - Shanghai Tel: 86-21-5407-5533 Fax: 86-21-5407-5066 China - Shenyang Tel: 86-24-2334-2829 Fax: 86-24-2334-2393 China - Shenzhen Tel: 86-755-8203-2660 Fax: 86-755-8203-1760 China - Shunde Tel: 86-757-2839-5507 Fax: 86-757-2839-5571 China - Wuhan Tel: 86-27-5980-5300 Fax: 86-27-5980-5118 China - Xian Tel: 86-29-8833-7250 Fax: 86-29-8833-7256 ASIA/PACIFIC India - Bangalore Tel: 91-80-2229-0061 Fax: 91-80-2229-0062 India - New Delhi Tel: 91-11-5160-8631 Fax: 91-11-5160-8632 India - Pune Tel: 91-20-2566-1512 Fax: 91-20-2566-1513 Japan - Yokohama Tel: 81-45-471- 6166 Fax: 81-45-471-6122 Korea - Gumi Tel: 82-54-473-4301 Fax: 82-54-473-4302 Korea - Seoul Tel: 82-2-554-7200 Fax: 82-2-558-5932 or 82-2-558-5934 Malaysia - Penang Tel: 604-646-8870 Fax: 604-646-5086 Philippines - Manila Tel: 632-634-9065 Fax: 632-634-9069 Singapore Tel: 65-6334-8870 Fax: 65-6334-8850 Taiwan - Hsin Chu Tel: 886-3-572-9526 Fax: 886-3-572-6459 Taiwan - Kaohsiung Tel: 886-7-536-4818 Fax: 886-7-536-4803 Taiwan - Taipei Tel: 886-2-2500-6610 Fax: 886-2-2508-0102 Thailand - Bangkok Tel: 66-2-694-1351 Fax: 66-2-694-1350 EUROPE Austria - Weis Tel: 43-7242-2244-399 Fax: 43-7242-2244-393 Denmark - Copenhagen Tel: 45-4450-2828 Fax: 45-4485-2829 France - Paris Tel: 33-1-69-53-63-20 Fax: 33-1-69-30-90-79 Germany - Munich Tel: 49-89-627-144-0 Fax: 49-89-627-144-44 Italy - Milan Tel: 39-0331-742611 Fax: 39-0331-466781 Netherlands - Drunen Tel: 31-416-690399 Fax: 31-416-690340 Spain - Madrid Tel: 34-91-352-30-52 Fax: 34-91-352-11-47 UK - Wokingham Tel: 44-118-921-5869 Fax: 44-118-921-5820 08/24/05 DS21921B-page 22 (c) 2005 Microchip Technology Inc. |
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