MPM3840

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2.8V-5.5V, 4A, Power Module, Synchronous Step-Down Converter with Integrated Inductor MPM3840 Rev. 1.1 www.MonolithicPower.com 1 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. The Future of Analog IC Technology

DESCRIPTION

The MPM3840 is a DC/DC module that includes a monolithic, step-down, switch-mode converter with built-in, internal power MOSFETs and an inductor. The MPM3840 can provide 4A of continuous output current from a 2.8V to 5.5V input voltage with excellent load and line regulation. The MPM3840 is ideal for powering portable equipment that run on a single-cell Lithium-ion (Li+) battery. The output voltage can be regulated as low as 0.6V. Only input capacitors, output capacitors, and feedback (FB) resistors are required to complete the design. The constant-on-time (COT) control scheme provides a fast transient response, high light-load efficiency, and easy loop stabilization. Full protection features include cycle-by-cycle current limiting and thermal shutdown. The MPM3840 requires a minimal number of readily available, standard, external components and is available in an ultra-small QFN-20 (3mmx5mmx1.6mm) package.

FEATURES

 >80% Light-Load Efficiency  Low I Q: 40μA  Wide 2.8V to 5.5V Operating Input Range  Output Voltage as Low as 0.6V  100% Duty Cycle in Dropout  4A Output Current  25m Ω and 12mΩ Internal Power MOSFETs  1.2MHz Frequency  External Mode Control  External Mode Control (PWM.PFM) and Dynamic Analog Voltage  EN and Power Good for Power Sequencing  Cycle-by-Cycle Over-Current Protection (OCP)  1.5ms Internal Soft-Start Time with Pre- Biased Start-Up  Short-Circuit Protection (SCP) with Hiccup Mode  Thermal Shutdown  Stable with Low ESR Output Ceramic Capacitors  Available in a QFN-20 (3mmx5mmx1.6mm) Package

APPLICATIONS

 Networking/Servers  Space-Constraint Applications  Industrial Products  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 unde r Quality Assurance. “MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION IOUT (A) Efficiency VIN=5V 100 0.001 0.01 0.1 1 10 Vo=1V@PWM Vo=1.2V@PWM Vo=1.5V@PWM Vo=1.8V@PWM Vo=1V@PFM Vo=1.2V@PFM Vo=1.5V@PFM Vo=1.8V@PFM Vo=2.5V@PWM Vo=3.3V@PWM Vo=2.5V@PFM Vo=3.3V@PFM

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 2 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved.

ORDERING INFORMATION

Part Number* Package Top Marking MPM3840GQV QFN-20 (3mmx5mmx1.6mm) See Below * For Tape & Reel, add suffix –Z (e.g. MPM3840GQV–Z) TOP MARKING MP: MPS prefix Y: Year code W: Week code 3840: First four digits of the part number LLL: Lot number M: Module PACKAGE REFERENCE TOP VIEW SW PGVIN SW GND SW RAMP SW OUT OUT OUT EN FB MODEGND 1415161718 GND GND GND NC NC 19 20 QFN-20 (3mmx5mmx1.6mm)

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 3 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. ABSOLUTE MAXIMUM RATINGS (1) 6V (10V for <10ns) Continuous power dissipation (T A = +25°C) (2) Recommended Operating Conditions (3) Operating junction temp. (TJ). .. -40°C to +125°C Thermal Resistance (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 T J (MAX), the junction-to- ambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by P D (MAX) = (T J (MAX)-TA)/θJA. Exceeding the maximum allowable powe r 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.

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 4 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved.

ELECTRICAL CHARACTERISTICS

VIN = 3.6V, V OUT = 1.2V, T J = -40°C to +125°C, typical value is tested at T J = +25°C. The limit over temperature is guaranteed by characterization, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units Feedback current I FB V FB = 0.65V 50 nA P-FET switch on resistance R DSON P 25 m Ω N-FET switch on resistance R DSON N 12 m Ω Dropout resistance R DR 100% on duty 47 m Ω Switch leakage T J = 25°C 0 1 μA P-FET peak current limit 4.5 5.5 6.5 A N-FET valley current limit 4 A On time TJ = 25°C 216 270 324 ns TJ = -40°C to 85°C 202 338 Switching frequency f s V OUT = 1.2V 1200 kHz Minimum off time T MIN-OFF 60 ns Minimum on time(5) T MIN-On 50 ns Soft-start time T SS-ON 1.5 ms PG UV threshold rising PGTH_Hi 0.9 VFB PG UV threshold falling PGTH_Lo 0.85 VFB PG OV threshold rising PGTH_Hi 1.15 VFB PG OV threshold falling PGTH_Lo 1.1 VFB Power good delay 140 μs Power good sink current capability V PG LO Sink 1mA 0.4 V Power good logic-high voltage V PG HI V IN = 5V, VFB = 0.6V 4.9 V Power good internal pull-up resistor R PG 500 k Ω Under-voltage lockout threshold rising 2.4 2.55 2.7 V Under-voltage lockout threshold hysteresis 300 mV EN input logic-low voltage 0.4 V EN input logic-high voltage 1.2 V EN input current VEN = 2V 2 μA VEN = 0V 0 μA Supply current (shutdown) V EN = 0V, TJ = 25°C 0.1 1 μA Supply current (quiescent) VIN = 3.6V, VEN = 2V, VFB = 0.65V, TJ = 25°C 40 60 μA Thermal shutdown(5) 150 °C Thermal hysteresis(5) 2 0 ° C Inductor L value 0.47 μH Inductor DC resistance 22 m Ω NOTE: 5) Guaranteed by design.

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 5 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. TYPICAL PERFORMANCE CHARACTERISTICS VIN = 5V, VOUT = 1.2V, COUT = 22μF*2, TA = +25°C, unless otherwise noted. EN THRESHOLD(V) REFERENCE VOLTAGE(mV) Quiescent Current vs. Temperature VIN=3.6V, No Switching Shutdown Current vs. Input Voltage VEN=Low EN Threshold vs. Temperature VIN=3.6V Reference Voltage vs. Temperature VIN=3.6V Current Limit vs. VIN VIN=3.6V Current Limit vs. Temperature VIN=3.6V INPUT VOLTAGE(V) PWM CURRENT LIMIT(A) VIN (V) PWM CURRENT LIMIT(A) INPUT VOLTAGE(V) Quiescent Current vs. Input Voltage No Switching 2.5 3 3.5 4 4.5 5 5.5 -40 -20 0 20 40 60 80 100120140 2.5 3 3.5 4 4.5 5 5.5 550 560 570 580 590 600 610 620 630 640 650 -40 -20 0 20 40 60 80 100120140 0.3 0.4 0.5 0.6 0.7 0.8 0.9 -40 -20 0 20 40 60 80 100120140 Falling Threshold Rising Threshold 3.5 4.5 5.5 6.5 -40 -20 0 20 40 60 80 100120140 NMOS PMOS 3.5 4.5 5.5 6.5 2.5 3 3.5 4 4.5 5 5.5 NMOS PMOS 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 6 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V, VOUT = 1.2V, COUT = 22μF*2, TA = +25°C, unless otherwise noted. IOUT (A) Efficiency VIN=3.3V IOUT (A) Efficiency VIN=5V 100 0.001 0.01 0.1 1 10 Vo=1V@PWM Vo=1.2V@PWM Vo=1.5V@PWM Vo=1.8V@PWM Vo=1V@PFM Vo=1.2V@PFM Vo=1.5V@PFM Vo=1.8V@PFM Vo=2.5V@PWM Vo=3.3V@PWM Vo=2.5V@PFM Vo=3.3V@PFM 100 0.001 0.01 0.1 1 10 Vo=1V@PWM Vo=1.2V@PWM Vo=1.5V@PWM Vo=1.8V@PWM Vo=1V@PFM Vo=1.2V@PFM Vo=1.5V@PFM Vo=1.8V@PFM OUTPUT CURRENT (A) OUTPUT CURRENT (A) Load Regulation Load Regulation VIN=3.3V Load Regulation Line Regulation Load Regulation VIN=3.3V OUTPUT CURRENT (A) INPUT VOLTAGE (V) OUTPUT CURRENT (A) -1.0 -0.5 0.0 0.5 1.0 2 2.5 3 3.5 4 4.5 5 5.5 6 0 0.5 1 1.5 2 2.5 3 3.5 4 PWM_Io=2A PWM_Io=0A PWM_Io=4A -0.50 -0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50 -0.50 -0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50 -0.50 -0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50 -0.50 -0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50 PFM_Vo=2.5V PFM_Vo=1V PFM_Vo=1.2V PWM_Vo=2.5V PWM_Vo=1V PWM_Vo=1.2V PFM_Vo=1V PFM_Vo=1.2V PWM_Vo=1V PWM_Vo=1.2V Case Temperature Rise IOUT(A) Case Temperature Rise VOUT=3.3V IOUT(A) 012345 VIN=3.3V VIN=5V 012345

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 7 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V, VOUT = 1.2V, COUT = 22μF*2, TA = +25°C, unless otherwise noted. Power On IOUT=0A, PWM Mode Power On IOUT=0A, PFM Mode Power On IOUT=4A, PWM Mode Power On IOUT=4A, PFM Mode VIN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 500mA/div. VIN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 500mA/div. VIN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 5A/div. VIN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 5A/div. MAXIMUM OUTPUT CURRENT(A) MAXIMUM OUTPUT CURRENT(A) OUTPUT VOLTAGE(V) VIN=3.3V VIN=5V -40 -20 0 20 40 60 80 100120140 VIN=3.3V,VOUT=2.5V VIN=5V,VOUT=3.3V VIN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 500mA/div. Power Off IOUT=0A, PWM Mode VIN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 500mA/div. VIN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 5A/div. Power Off IOUT=0A, PFM Mode Power Off IOUT=4A, PWM Mode

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 8 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V, VOUT = 1.2V, COUT = 22μF*2, TA = +25°C, unless otherwise noted. Enable Turn-On IOUT=0A, PWM Mode Enable Turn-On IOUT=4A, PWM Mode Enable Turn-On IOUT=4A, PFM Mode Enable Turn-Off IOUT=0A, PWM Mode Enable Turn-On IOUT=0A, PFM Mode VIN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 5A/div. VEN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 500mA/div. VEN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 5A/div. VEN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 5A/div. VEN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 500mA/div. VEN 2V/div. VSW 5V/div. VOUT 500mV/div. IOUT 500mA/div. Power Off IOUT=4A, PFM Mode Enable Turn-Off IOUT=0A, PFM Mode Enable Turn-Off IOUT=4A, PWM Mode Enable Turn-Off IOUT=4A, PFM Mode VEN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 500mA/div. VEN 2V/div. VSW 5V/div. VOUT 500mV/div. IOUT 5A/div. VEN 2V/div. VSW 2V/div. VOUT 500mV/div. IOUT 5A/div.

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 9 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V, VOUT = 1.2V, COUT = 22μF*2, TA = +25°C, unless otherwise noted. VIN 5V/div. VSW 5V/div. VOUT/AC 20mV/div. IOUT 500mA/div. VIN 5V/div. VSW 2V/div. VOUT/AC 50mV/div. IOUT 500mA/div. VIN 5V/div. VSW 5V/div. VOUT/AC 50mV/div. IOUT 2A/div. VIN 5V/div. VSW 5V/div. VOUT/AC 50mV/div. IOUT 5A/div. VIN 5V/div. VSW 5V/div. VOUT/AC 20mV/div. IOUT 5A/div. VIN 5V/div. VSW 2V/div. VOUT/AC 100mV/div. IOUT 500mA/div. Steady State IOUT=0A, PWM Mode Steady State IOUT=0A, PFM Mode Steady State IOUT=4A, PWM/PFM Mode Steady State IOUT=0.1A, PFM Mode Response to Transient Load IOUT=0 to 2A, PWM Mode Response to Transient Load IOUT=0 to 4A, PWM Mode VIN 5V/div. VSW 5V/div. VOUT/AC 50mV/div. IOUT 5A/div. VIN 5V/div. VSW 5V/div. VOUT/AC 50mV/div. IOUT 5A/div. VIN 5V/div. VSW 5V/div. VOUT/AC 50mV/div. IOUT 2A/div. Response to Transient Load IOUT=2A to 4A, PWM/PFM Mode Response to Transient Load IOUT=0 to 2A, PFM Mode Response to Transient Load IOUT=0 to 4A, PFM Mode

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 10 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V, VOUT = 1.2V, COUT = 22μF*2, TA = +25°C, unless otherwise noted. VOUT 500mV/div. VEN 2V/div. VPG 2V/div. VOUT 500mV/div. VEN 2V/div. VPG 2V/div. VIN 5V/div. VSW 5V/div. VOUT 500mV/div. IOUT 5A/div. VIN 5V/div. VSW 5V/div. VOUT 500mV/div. IOUT 5A/div. VIN 5V/div. VSW 5V/div. VOUT 500mV/div. IOUT 5A/div. VIN 5V/div. VSW 5V/div. VOUT 500mV/div. IOUT 5A/div. Power Good IOUT=0A Output Short Entry IOUT=0A, PFM Mode Power Bad IOUT=0A Output Short Recovery IOUT=0A, PFM Mode Output Short Entry IOUT=0A, PWM Mode Output Short Recovery IOUT=0A, PWM Mode

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 11 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. PIN FUNCTIONS Pin # Name Description 1, 2, 3, 17, 18 GND IC ground. Connect the GND pins to larger copper areas to the negative terminals of the input and output capacitors. 4, 5, 6, 16 SW Switch node. Connect SW to the inductor. SW also connects to the internal high- side and low-side power MOSFET switches. 7, 8, 9 OUT Output voltage sense. 10 FB Feedback. An external resistor divider from the output to GND tapped to FB sets the output voltage.

11 RAMP

External ramp. RAMP sets the ramp to optimize transient performance. Connect a ceramic capacitor (10pF to 47pF) between OUT and RAMP to improve transient performance. 12 EN Enable. Set EN to a high voltage level to enable the MPM3840. For automatic start- up, connect EN to VIN with a pull-up resistor.

13 MODE

Multi-use pin. MODE is also denoted as VCON. For PWM and PFM selection: When V MODE is more than 1.2V, the MPM3840 enters PWM, and the internal reference is 0.6V. When V MODE is lower than 0.4V or is floating, the MPM3840 enters PFM. For analog voltage dynamic regulation: When V MODE is between 0.6V and 1.1V, the reference voltage can be controlled by V MODE, and the MPM3840 works in PWM. Avoid setting V MODE between 0.4V and 0.6V as the MPM3840 may operate in an unknown mode. 14 PG Power good. PG has an internal, 500k Ω, pull-up resistor. PG is pulled up to VIN when the FB voltage is within 10% of the regulation level; otherwise, PG is low. There is a 140μs delay between the moment when VFB reaches the PG threshold and when PG goes high. 15 VIN Input supply. VIN requires a decoupling capacitor to ground to reduce switching spikes. 19, 20 NC Do not connect. NC must be left floating.

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 12 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. BLOCK DIAGRAM Figure 1: Functional Block Diagram

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 13 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. OPERATION The MPM3840 uses a constant-on-time (COT) control with input voltage feed-forward to stabilize the switching frequency over the full input range. At light load, the MPM3840 employs a proprietary control of low-side switching and inductor current on the switching node to improve efficiency. The module has an integrated inductor that makes the schematic and layout design very simple. Only input capacitors, output capacitors, and FB resistors are required to complete the design. Constant-On-Time (COT) Control Compared to fixed-frequency PWM control, constant-on-time (COT) control offers a simpler control loop and faster transient response. By using an input voltage feed-forward, the MPM3840 maintains a nearly constant switching frequency across the input and output voltage ranges. The switching pulse on time can be estimated with Equation (1): OUT ON IN To prevent inductor current runaway during the load transient, the MPM3840 has a constant minimum off-time of 60ns. This minimum off time limit will not affect operation in steady state in any way. Light-Load Operation During light loads, the MPM3840 uses a proprietary control scheme to save power and improve efficiency. A zero-current cross detection (ZCD) circuit is used to detect when the inductor current starts to reverse. The low- side MOSFET (LS-FET) turns off immediately when the inductor current starts to reverse and triggers ZCD in discontinuous conduction mode (DCM) operation. Considering the internal circuit propagation time, the typical delay is 50ns. This means that the inductor current continues falling after the ZCD is triggered in this delay time. If the inductor current falling slew rate is fast (V OUT is high or close to VIN), the LS-FET is turned off, and the inductor current may be negative. This prevents the MPM3840 from entering DCM operation. For example, if VIN is 3.6V, and V OUT is 3.3V, then the off time in CCM is 70ns. It is difficult to enter DCM at light load. Enable (EN) When the input voltage is greater than the under-voltage lockout (UVLO) threshold (typically 2.55V), the MPM3840 can be enabled by pulling EN higher than 1.2V. Leave EN floating or pull EN down to ground to disable the MPM3840. There is an internal 1MΩ resistor from EN to ground. MODE Selection and Analog Voltage Dynamic Regulation The MPM3840 has programmable pulse-width modulation (PWM) and pulse-frequency modulation (PFM) work modes. When the voltage on MODE (V MODE) is higher than 1.2V, the MPM3840 operates in PWM. When VMODE is lower than 0.4V or is floating, the MPM 3840 operates in PFM, which can achieve high efficiency in light-load condition. PWM mode can maintain a constant switching frequency and small V OUT ripple, but has low efficiency at light load. REFERENCE VOLTAGE (V) VCON (V) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Figure 2: Reference Voltage Change with VCON The MPM3840 can regulate the output voltage by dynamically changing the MODE voltage CON) to meet a situation where the output voltage must be adjusted directly. When V CON is an appropriate value (0.6V to 1.1V), the MPM3840 works in PWM, and the internal reference voltage changes smoothly as V CON changes to provide a new output voltage without changing the external resistor divider. When the V CON function is enabled, set the reference voltage (Vref) to be from 0.35V to 0.6V. The accuracy is typically 3%. When setting the V ref value from 0.1V to 0.35V, the accuracy is

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 14 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. typically 10%. The detailed V Ref curve is shown in Figure 2. Calculate Vref with Equation (2): Ref(V)=0.985 VCON(V)-0.486 (2) Soft Start (SS) The MPM3840 has a built-in soft start (SS) that ramps up the output voltage at a constant slew rate to avoid overshooting at start-up. The soft- start time is about 1.5ms, typically. Pre-Bias Start-Up The MPM 3840 can start up with a pre-biased output voltage. If the internal SS voltage is lower than the FB voltage, the HS-FET and LS- FET remain off until the SS voltage crosses the FB voltage. Power Good (PG) Indicator The MPM3840 has an open drain with a 500k Ω pull-up resistor as a power good (PG) indicator. PG is pulled up to VIN when the FB voltage is within 10% of the regulation level; otherwise, PG is low. There is a 140 μs delay between the moment when V FB reaches the PG threshold and when PG goes high. The MOSFET has a maximum R DS(ON) of 100Ω. Current Limit The MPM3840 has a 5.5A current limit for the HS-FET. When the HS-FET reaches its current limit, the MPM3840 enters hiccup mode until the current drops to prevent the inductor current from rising and damaging the components. Short Circuit and Recovery The MPM 3840 enters short-circuit protection (SCP) mode when it reaches the current limit and attempts to recover with hiccup mode. The MPM3840 disables the output power st age, discharges the soft-start capacitor, and attempts to soft start. If the short-circuit condition remains after the soft start ends, the MPM3840 repeats this operation until the short circuit is removed and the output rises back to regulation levels.

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 15 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved.

APPLICATION INFORMATION

Setting the Output Voltage The external resistor divider sets the output voltage (see the Typical Application Circuit on page 17). Select the feedback resistor (R1) to reduce V OUT leakage current, typically between 40kΩ to 200k Ω. There is no strict requirement on the feedback resistor. R1 > 10k Ω is reasonable for most applications. R2 can be calculated with Equation (2): out R1R2 V 10.6 (2) The feedback circuit is shown in Figure 3. Vo ut FB Figure 3: Feedback Network Table 1 lists the recommended resistor values for common output voltages. Table 1: Resistor Values for Common Output Voltages VOUT (V) R1 (k Ω) R2 (k Ω) 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. Use low ESR capacitors for the best performance. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR values and small temperature coefficients. For most applications, a 22µF capacitor is sufficient. For higher output voltages, a 47µF capacitor may be needed to improve system stability. Since the input capacitor absorbs the input switching current, it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated with Equation (3): OUT OUT C1 LOAD IN IN VVII 1 VV   (3) The worst-case condition occurs at VIN = 2V OUT, shown in Equation (4): LOAD II 2 (4) For simplification, choose an input capacitor with an RMS current rating greater than half of the maximum load current. The input capacitor can be electrolytic, tantalum, or ceramic. When using electrolytic or tantalum capacitors, use a small, high-quality, 0.1 μF, ceramic capacitor placed as close to the IC as possible. When using ceramic capacitors, ensure that they have enough capacitance to prevent excessive voltage ripple at the input. The input voltage ripple caused by the capacitance can be estimated with Equation (5): LOAD OUT OUT IN INSI N IV VV1 fC 1V V (5)

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR MPM3840 Rev. 1.1 www.MonolithicPower.com 17 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. TYPICAL APPLICATION CIRCUIT GND SWSWSWSW Figure 4: Application for 1.2V Output

MPM3840 – 4A, 2.8V-5.5V, POWER MODULE SYNCHRONOUS STEP-DOWN CONVERTERWITH INTEGRATED INDUCTOR NOTICE: The information in this document is subject to change wi thout notice. Please contact M PS for current specifications. Users should warrant and guarantee that third party Intellectual Property rights ar e not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MPM3840 Rev. 1.1 www.MonolithicPower.com 18 3/10/2017 MPS Proprietary Information. Patent Protec ted. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved.

PACKAGE INFORMATION

QFN-20 (3mmx5mmx1.6mm)