MP1601 1A, Synchronous, Step-Down Converter with 11µA Quiescent Current in SOT563 The Future of Analog IC Technology DESCRIPTION FEATURES The MP1601 is a monolithic, step-down, switchmode converter with built-in, internal power MOSFETs. It can achieve 1A of continuous output current from a 2.3V-to-5.5V input voltage range with excellent load and line regulation. The output voltage can be regulated as low as 0.6V. The constant-on-time control scheme provides a fast transient response and eases loop stabilization. Fault protections include cycle-bycycle current limiting and thermal shutdown. The MP1601 is available in an ultra-small SOT563 package and requires a minimal number of readily available, standard, external components. The MP1601 is ideal for a wide range of applications including high-performance DSPs, wireless power, portable and mobile devices, and other low-power systems. Low Quiescent Current: 11μA 2.2MHz Switching Frequency EN for Power Sequencing Power Good Only for Fixed Output Version Wide 2.3V-to-5.5V Operating Input Range Output Adjustable from 0.6V Up to 1A of Output Current 160mΩ and 120mΩ Internal Power MOSFET Switches Output Discharging Short-Circuit Protection (SCP) with Hiccup Mode Stable with Low ESR Output Ceramic Capacitors 100% Duty Cycle Available in a SOT563 Package APPLICATIONS Wireless/Networking Cards Portable and Mobile Devices Battery-Powered Devices Low-Voltage I/O System Power All MPS parts are lead-free, halogen-free, and adhere to the RoHS directive. For MPS green status, please visit the MPS website under Quality Assurance. “MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION L1 1μH VIN 5V SW VIN OUT C1 10μF R1 200kΩ MP1601 EN EN C2 10μF FB GND MP1601 Rev. 1.0 3/24/2016 VOUT 1.2V/1A R2 200kΩ www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 1 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ ORDERING INFORMATION Part Number* MP1601GTF MP1601GTF-12** MP1601GTF-15** MP1601GTF-18** MP1601GTF-25** MP1601GTF-33** Package SOT563 Top Marking See Below See Below See Below See Below See Below See Below VOUT Range Adjustable Fixed 1.2V Fixed 1.5V Fixed 1.8V Fixed 2.5V Fixed 3.3V * For Tape & Reel, add suffix –Z (e.g. MP1601GTF–Z) ** Contact factory for fixed output options. TOP MARKING (MP1601GTF) ARB: Product code of MP1601GTF Y: Year code LLL: Lot number TOP MARKING (MP1601GTF-12) AUU: Product code of MP1601GTF-12 Y: Year code LLL: Lot number TOP MARKING (MP1601GTF-15) AUN: Product code of MP1601GTF-15 Y: Year code LLL: Lot number MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 2 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ TOP MARKING (MP1601GTF-18) AUP: Product code of MP1601GTF-18 Y: Year code LLL: Lot number TOP MARKING (MP1601GTF-25) AUQ: Product code of MP1601GTF-25 Y: Year code LLL: Lot number TOP MARKING (MP1601GTF-33) AUR: Product code of MP1601GTF-33 Y: Year code LLL: Lot number MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 3 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ PACKAGE REFERENCE TOP VIEW TOP VIEW FB 1 6 OUT PG 1 6 OUT GND 2 5 EN GND 2 5 EN VIN 3 4 SW VIN 3 4 SW MP1601GTF-12 MP1601GTF-15 MP1601GTF-18 MP1601GTF-25 MP1601GTF-33 MP1601GTF SOT563 ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Supply voltage (VIN) ....................................... 6V VSW ................................ -0.6V (-5V for <10ns) to 6V (8V for <10ns or 10V for <3ns) All other pins ..................................... -0.3V to 6V Junction temperature ................................150°C Lead temperature .....................................260°C (2) Continuous power dissipation (TA = +25°C) ……….….. .................................................... 1W Storage temperature ................ -65°C to +150°C SOT563………………….......130……60.…°C/W Recommended Operating Conditions (3) Supply voltage (VIN) ........................ 2.3V to 5.5V Operating junction temp. (TJ). .. -40°C to +125°C MP1601 Rev. 1.0 3/24/2016 (4) θJA θJC NOTES: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = (TJ (MAX)-TA)/θJA. Exceeding the maximum allowable power dissipation produces an excessive die temperature, causing the regulator to go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 3) The device is not guaranteed to function outside of its operating conditions. 4) Measured on JESD51-7, 4-layer PCB. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 4 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ ELECTRICAL CHARACTERISTICS VIN = 3.6V, TJ = -40°C to +125°C. Typical value is tested at TJ = +25°C. The limit over temperature is guaranteed by characterization, unless otherwise noted. Parameter Symbol Feedback voltage (MP1601GTF only) VFB (7) Fixed Output Voltage Feedback current (MP1601GTF only) P-FET switch on resistance N-FET switch on resistance IFB RDSON RDSON Condition Min Typ Max 2.3V ≤ VIN ≤ 5.5V, TJ = 25°C 594 600 606 TJ = -40°C to +125°C 588 1.188 1.2 1.212 V Only for MP1601GTF-12, IOUT=10mA, TJ=-40°C to +125°C 1.176 1.2 1.224 V Only for MP1601GTF-15, IOUT=10mA, TJ=+25C 1.485 1.5 1.515 V Only for MP1601GTF-15, IOUT=10mA, TJ=-40°C to +125°C 1.470 1.5 1.530 V Only for MP1601GTF-18, IOUT=10mA, TJ=+25C 1.782 1.8 1.818 V Only for MP1601GTF-18, IOUT=10mA, TJ=-40°C to +125°C 1.764 1.8 1.836 V Only for MP1601GTF-25, IOUT=10mA, TJ=+25C 2.475 2.5 2.525 V Only for MP1601GTF-25, IOUT=10mA, TJ=-40°C to +125°C 2.450 2.5 2.550 V Only for MP1601GTF-33, IOUT=10mA, TJ=+25C 3.267 3.3 3.333 V Only for MP1601GTF-33, IOUT=10mA, TJ=-40°C to +125°C 3.234 3.3 3.366 V 50 100 nA VFB = 0.63V 160 120 P N VEN = 0V, VIN = 6V, VSW = 0V and 6V, TJ = 25°C P-FET peak current limit Sourcing N-FET valley current limit Sourcing, valley current limit ZCD MP1601 Rev. 1.0 3/24/2016 TON mV Only for MP1601GTF-12, IOUT=10mA, TJ=+25C Switch leakage current On time (MP1601GTF only) 612 Units VIN = 5V, VOUT = 1.2V VIN = 3.6V, VOUT = 1.2V 0 1.8 mΩ mΩ 1 μA 2.4 A 1.5 A 0 mA 110 150 ns www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 5 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ ELECTRICAL CHARACTERISTICS VIN = 3.6V, TJ = -40°C to +125°C. Typical value is tested at TJ = +25°C. The limit over temperature is guaranteed by characterization, unless otherwise noted. Parameter Symbol Switching frequency Minimum off time Minimum on time (5) Soft-start time fs Condition VIN = 5V, VOUT = 1.2V, IOUT = 500mA, TJ = 25°C(5) VIN = 5V, VOUT = 1.2V, IOUT = 500mA, TJ = -40°C to +125°C(5) Min Typ Max Units 1760 2200 2640 kHz 1650 2200 2750 kHz TMIN-OFF 60 ns TMIN-ON 60 ns 0.5 ms TSS-ON VOUT rise from 10% to 90% Under-voltage lockout threshold rising Under-voltage lockout threshold hysteresis EN input logic low voltage 2 150 EN input logic high voltage Output discharge resistor Supply current (shutdown) Supply current (quiescent) VEN = 0V, VOUT = 1.2V VEN = 2V VEN = 0V VEN = 0V, TJ = 25°C VEN = 2V, VFB = 0.63V, VIN = 3.6V, 5V, TJ = 25°C IPG Vo with Respect to the Regulation V mV 0.4 V 1 1.2 0 0 1 kΩ μA μA μA 11 13 μA 50 100 nA 1.2 RDIS EN input current Power Good Leakage Current (MP1601GTF-XX only) Power Good Upper Trip Threshold (MP1601GTF-XX only) Power Good Lower Trip Threshold (MP1601GTF-XX only) Power Good Delay (MP1601GTF-XX only) Power Good Sink Current Capability (MP1601GTF-XX only) 2.25 V 90 % 85 % 70 μs Sink 1mA 400 mV Thermal shutdown(6) 160 °C Thermal hysteresis(6) 30 °C NOTES: 5) Guaranteed by characterization. 6) Guaranteed by design. 7) Without Sleep Mode. MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 6 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ TYPICAL PERFORMANCE CHARACTERISTICS VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25°C, unless otherwise noted. Quiescent Current vs. Input Voltage 1 SHUTDOWN CURRENT ( A) 18 16 14 12 10 8 6 4 2 2 3 4 5 INPUT VOLTAGE (V) VEN=0V 0.4 0.8 0.6 0.4 0.2 0 -0.2 6 2 Line Regulation vs. Input Voltage 6 0.2 0.1 VOUT=3.3V 0.0 -0.1 -0.2 VOUT=1.2V -0.3 -0.4 -0.5 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 OUTPUT CURRENT (A) Efficiency vs. Output Current 100 12 95 0.4 0.3 CASE TEMPERATURE RIS LINE REGULATION ( ) 3 4 5 INPUT VOLTAGE (V) 0.3 Case Temperature Rise vs. Output Current 0.5 IOUT=0.15A 0.2 0.1 0.0 -0.1 IOUT=0.5A -0.2 -0.3 IOUT=1A -0.4 -0.5 0.5 LOAD REGULATION ( ) 20 0 Load Regulation vs. Output Current Shutdown Current vs. Input Voltage 2 3 4 5 6 10 90 85 8 VOUT=2.5V VOUT=1.2V 80 V OUT=1.8V 75 VIN=3.3V 6 70 4 65 2 0 60 VIN=5V 0 0.2 0.4 0.6 0.8 INPUT VOLTAGE (V) OUTPUT CURRENT (A) Efficiency vs. Output Current Current Limit vs. VIN VIN=3.3V VOUT=3.3V 55 1 50 0.001 0.01 0.1 1 OUTPUT CURRENT (A) 3 100 95 85 CURRENT LIMIT (A) 90 VOUT=1.8V VOUT=1.2V 80 V OUT=2.5V 75 70 65 60 2.5 2 1.5 55 50 0.001 0.01 0.1 OUTPUT CURRENT (A) MP1601 Rev. 1.0 3/24/2016 1 1 2 3 4 5 6 INPUT VOLTAGE (V) www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 7 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25°C, unless otherwise noted. MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 8 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25°C, unless otherwise noted. Steady State Steady State Steady State without Load with 1A Load VIN=3.6V, VOUT=3.3V, IOUT=0A VOUT/AC 10mV/div. VOUT/AC 50mV/div. VOUT/AC 100mV/div. VIN 5V/div. VIN 5V/div. VIN 5V/div. VSW 2V/div. VSW 2V/div. IL 500mA/div. VSW 5V/div. IL 0.2A/div. IL 1A/div. Steady State VIN=3.6V, VOUT=3.3V, IOUT=0.05A, AAM Steady State Steady State VIN=3.6V, VOUT=3.3V, IOUT=0.25A, AAM VIN=3.6V, VOUT=3.3V, IOUT=1A, AAM VOUT/AC 20mV/div. VOUT/AC 50mV/div. VIN 5V/div. VIN 5V/div. VIN 5V/div. VSW 2V/div. VSW 2V/div. VOUT/AC 100mV/div. VSW 2V/div. IL 0.2A/div. IL 0.2A/div. VIN Power Up IL 1A/div. VIN Power Up without Load VIN Shut Down with 1A Load without Load VOUT 1V/div. VIN 5V/div. VOUT 1V/div. VIN 5V/div. VOUT 1V/div. VIN 5V/div. VSW 5V/div. VSW 5V/div. VSW 5V/div. IL 1A/div. IL 1A/div. IL 1A/div. MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 9 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25°C, unless otherwise noted. MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 10 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED) VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25°C, unless otherwise noted. MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 11 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ PIN FUNCTIONS Pin # Name Description 1 MP1601GTF: Feedback. An external resistor divider from the output to GND tapped to FB sets the output voltage. FB/PG MP1601GTF-XX: Power good indicator. The output of PG is an open-drain output. Keep PG pulls up voltage is not more than Vin. 2 GND Power ground. 3 VIN 4 SW 5 EN 6 OUT MP1601 Rev. 1.0 3/24/2016 Supply voltage. The MP1601 operates on a +2.3V to +5.5V unregulated input. A decoupling capacitor is needed to prevent large voltage spikes from appearing at input. Output switching node. SW is the drain of the internal high-side P-channel MOSFET. Connect the inductor to SW to complete the converter. On/off control. Output voltage power rail and input sense. Connect the load to OUT. An output capacitor is needed to decrease the output voltage ripple. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 12 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ BLOCK DIAGRAM Figure 1: Functional Block Diagram NOTE: Option 1) FB is only for the MP1601GTF Option 2) PG is only for the MP1601GTF-XX MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 13 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ OPERATION The MP1601 uses constant-on-time control with an input voltage feed-forward to stabilize the switching frequency over the full input range. It achieves 1A of continuous output current from a 2.3V-to-5.5V input voltage range with excellent load and line regulation. The output voltage can be regulated as low as 0.6V. Constant-on-Time Control Compared to fixed-frequency PWM control, constant-on-time control offers a simpler control loop and a faster transient response. By using an input voltage feed-forward, the MP1601 maintains a nearly constant switching frequency across the input and output voltage ranges. The switching pulse on time can be estimated with Equation (1): V (1) TON OUT 0.454s VIN To prevent inductor current runaway during the load transient, the MP1601 uses a fixed minimum off time of 60ns. Sleep Mode Operation The MP1601 uses sleep mode to achieve high efficiency at extremely light loads. In sleep mode, most of the circuit blocks are turned off, except the error amplifier and the PWM comparator. Therefore, the operating current is reduced to a minimal value (see Figure 2). Figure 2: Operation Blocks in Sleep Mode When the load becomes lighter, the output voltage ripple is bigger and drives the error amplifier output (EAO) lower. When the EAO hits an internal low threshold, it clamps at that level, and the MP1601 enters sleep mode. During sleep mode, the valley of the FB voltage is regulated to the internal reference voltage, MP1601 Rev. 1.0 3/24/2016 making the average output voltage slightly higher than the output voltage at DCM or CCM. The on-time pulse in sleep mode is around 40% larger than that in DCM or CCM. Figure 3 shows the average FB voltage relationship with the internal reference at sleep mode. Figure 3: FB Average Voltage at Sleep Mode When the MP1601 is in sleep mode, the average output voltage is higher than the internal reference voltage. The EAO is kept low and clamped in sleep mode. When the loading increases, the PWM switching period decreases to keep the output voltage regulated, and the output voltage ripple decreases as well. Once the EAO is higher than the internal low threshold, the MP1601 exits sleep mode and enters DCM or CCM, depending on the load. In DCM or CCM, the EAO regulates the average output voltage to the internal reference (see Figure 4). Figure 4: DCM Control There is always a loading hysteresis when entering and exiting sleep mode due to the error amplifier clamping response time. AAM Operation at Light-Load Operation The MP1601 uses an advanced asynchronous modulation (AAM) power-save mode with a zero-current cross detection (ZCD) circuit for light loads. The MP1601 uses AAM power-save mode in light loads (see Figure 5). The AAM current (IAAM) is set internally. The SW on pulse time is decided by an on-time generator and AAM comparator. At light-load condition, the SW on the pulse time is stretched. The AAM comparator pulse is longer than the on-time generator. The mode of operation is below in Figure 6. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 14 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ VFB EN COT Generator VREF FBCOMP S Q HS_ driver R IL_ sense Figure 9 shows the AAM threshold decreasing and TON increasing gradually. For CCM state, IOUT requires more than half of the AAM threshold. IAAM AAMCOMP Figure 5: Simplified AAM Control Logic Figure 6: AAM Comparator Control TON The AAM comparator pulse is shorter than the on-time generator. The mode of operation is shown below in Figure 7. This usually occurs when using a very small inductance. Figure 7: On-Time Control (TON) Besides the upper on-time method, the AAM circuit has another 150ns AAM blank time in sleep mode. If the on-timer is less than 150ns, the high-side MOSFET may turn off after the on-time generator pulse without AAM control. The on-time pulse at sleep mode is around 40% larger than that in DCM or CCM. In this condition, IL may not reach the AAM threshold (see Figure 8). Figure 9: AAM Threshold Decreases with TON Increasing The MP1601 uses ZCD to detect if the inductor current begins reversing. When the inductor current reaches the ZCD threshold, the low-side switch is turned off. AAM mode and the ZCD circuit together cause the MP1601 to work in DCM in light load continuously, even if VOUT is close to VIN. Enable (EN) When the input voltage is greater than the under-voltage lockout (UVLO) threshold (typically 2V), the MP1601 can be enabled by pulling EN higher than 1.2V. Floating EN or pulling it down to ground disables the MP1601. There is an internal 1MΩ resistor from EN to ground. When the device is disabled, the MP1601 goes into output discharge mode automatically. Its internal discharge MOSFET provides a resistive discharge path for the output capacitor. Soft Start (SS) The MP1601 has a built-in soft start that ramps up the output voltage at a controlled slew rate to avoid overshooting at start-up. The soft start time is about 0.5ms, typically. Figure 8: AAM Blank Time in Sleep Mode MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 15 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ Power Good Indictor (Only for the MP1601GTF-XX) The MP1601 has an open drain and requires an external pull-up resistor between 100kΩ~500kΩ for the power good indicator. (Note: Keep PG pulls up voltage is not more than Vin). When VFB is within -10% of regulation voltage, VPG is pulled up to VIN by the external resistor. If VFB exceeds the -10% window, the internal MOSFET pulls PG to ground. The MOSFET has a maximum RDS(ON) of less than 400Ω. Short Circuit and Recovery The MP1601 enters short-circuit protection mode when it reaches the current limit and attempts to recover with hiccup mode. In this process, the MP1601 disables the output power stage, discharges the soft-start capacitor, and then attempts to soft start again automatically. If the short-circuit condition remains after the softstart ends, the MP1601 repeats this cycle until the short-circuit disappears and the output rises back to regulation level. Current Limit The MP1601 has a 2.4A high-side switch current limit, typically. When the high-side switch reaches its current limit, the MP1601 remains in hiccup mode until the current drops. This prevents the inductor current from continuing to rise and damaging components. MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 16 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ APPLICATION INFORMATION Setting the Output Voltage (Only for MP1601GTF) The external resistor divider sets the output voltage (see the Typical Application Circuit on Figure 12). Select the feedback resistor (R1), typically between 40kΩ to 200kΩ, to reduce the VOUT leakage current. There is no strict requirement on the feedback resistor. R1 > 10kΩ is reasonable for most applications. Calculate R2 with Equation (2): R1 (2) R2 Vout 1 0.6 Figure 10 shows the feedback circuit. Table 2: Suggested Inductor List Manufacturer P/N Inductance (μH ) Manufacturer PIFE25201B-1R0MS 1.0 CYNTEC CO. LTD 1239AS-H-1R0M 1.0 Tokyo 74438322010 1.0 Wurth For most designs, the inductance value can be calculated with Equation (3): L1 VOUT (VIN VOUT ) VIN IL fOSC Where ∆IL is the inductor ripple current. Choose the inductor current to be approximately 30% of the maximum load current. The maximum inductor peak current can be calculated with Equation (4): IL(MAX ) ILOAD Figure 10: Feedback Network Table 1 lists the recommended resistor values for common output voltages. Table 1: Resistor Values for Common Output Voltages VOUT (V) 1.0 1.2 1.8 2.5 3.3 R1 (kΩ) 200 (1%) 200 (1%) 200 (1%) 200 (1%) 200 (1%) R2 (kΩ) 300 (1%) 200 (1%) 100 (1%) 63.2 (1%) 44.2 (1%) Selecting the Inductor Most applications work best with a 0.47µH-to2.2µH inductor. Select an inductor with a DC resistance below 50mΩ to optimize efficiency. A high-frequency switch mode power supply with a magnetic device has a strong, electronic, magnetic inference for the system. Any unshielded power inductor should be avoided. Metal alloy or multiplayer chip power inductors are ideal shielded inductors for the application of the EMI as they can decrease the influence effectively. Table 2 lists some recommended inductors. MP1601 Rev. 1.0 3/24/2016 (3) IL 2 (4) Selecting the Input Capacitor The input current to the step-down converter is discontinuous and therefore requires a capacitor to supply AC current to the step-down converter while maintaining the DC input voltage. For best performance, use low ESR capacitors. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 10µF capacitor is sufficient. Higher output voltages may require a 22μF capacitor to increase system stability. The input capacitor requires an adequate ripple current rating because it absorbs the input switching current. Estimate the RMS current in the input capacitor with Equation (5): IC1 ILOAD VOUT VOUT 1 VIN VIN (5) The worst case occurs at VIN = 2VOUT, shown in Equation (6): I (6) IC1 LOAD 2 For simplification, choose an input capacitor with an RMS current rating greater than half of the maximum load current. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 17 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ The input capacitor can be electrolytic, tantalum, or ceramic. When using electrolytic or tantalum capacitors, add a small, high-quality ceramic 0.1μF capacitor as close to the IC as possible. When using ceramic capacitors, ensure that they have enough capacitance to provide a sufficient charge to prevent excessive voltage ripple at the input. The input voltage ripple caused by capacitance can be estimated with Equation (7): VIN ILOAD V V OUT 1 OUT fS C1 VIN VIN (7) Selecting the Output Capacitor The output capacitor (C2) stabilizes the DC output voltage. Ceramic capacitors are recommended. For best results, use low ESR capacitors to limit the output voltage ripple. The output voltage ripple can be estimated with Equation (8): VOUT (8) VOUT VOUT 1 1 RESR fS L1 VIN 8 fS C2 PCB Layout Guidelines Efficient PCB layout is critical for stable operation. For the high-frequency switching converter, a poor layout design can result in poor line or load regulation and stability issues. For best results, refer to Figure 11 and follow the guidelines below. 1. Place the high-current paths (GND, IN, and SW) very close to the device with short, direct, and wide traces. 2. Place the input capacitor as close to IN and GND as possible. 3. Place the external feedback resistors next to FB. 4. Keep the switching node SW short and away from the feedback network. 5. Keep the VOUT sense line as short as possible or keep it away from the power inductor. Where L1 is the inductor value and RESR is the equivalent series resistance (ESR) value of the output capacitor. When using ceramic capacitors, the capacitance dominates the impedance at the switching frequency and causes most of the output voltage ripple. For simplification, the output voltage ripple can be estimated with Equation (9): ∆VOUT V VOUT 1 OUT 8 fS L1 C2 VIN 2 (9) Figure 11: Two Ends of the Input Decoupling Capacitor Close to Pin 2 and Pin 3 For tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated with Equation (10): ∆VOUT VOUT V 1 OUT fS L1 VIN RESR (10) The characteristics of the output capacitor also affect the stability of the regulation system. MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 18 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ TYPICAL APPLICATION CIRCUITS Figure 12: Typical Application Circuit for the MP1601GTF NOTE: VIN < 3.3V may need more input capacitors Figure 13: Typical Application Circuit for the MP1601GTF-XX NOTE: 1) VIN < 3.3V may need more input capacitor 2) VIN > VOUT for application MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 19 MP1601 – 1A, SYNCHRONOUS, STEP-DOWN CONVERTER WITH 11µA IQ PACKAGE INFORMATION SOT563 NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MP1601 Rev. 1.0 3/24/2016 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 20