MP2158 1A, 6V, 1.5MHz, 17μA IQ, COT Synchronous Step Down Switcher In Ultra-small 2x1.5mm QFN The Future of Analog IC Technology DESCRIPTION FEATURES The MP2158 is a monolithic step-down switch mode converter with built-in internal power MOSFETs. It achieves 1A continuous output current from a 2.5V to 6V input voltage with excellent load and line regulation. The output voltage can be regulated as low as 0.6V. The Constant-On-Time control scheme provides fast transient response and eases loop stabilization. Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. The MP2158 is available in the small QFN8 2.0x1.5mm package and requires a minimum number of readily available standard external components. The MP2158 is ideal for a wide range of applications including High Performance DSPs, FPGAs, PDAs, and portable instruments. Very Low IQ: 17μA Default 1.5MHz Switching Frequency EN and Power Good for Power Sequencing Ultra-small 2.0x1.5mm QFN8 Package Wide 2.5V to 6V Operating Input Range Output Adjustable from 0.6V Up to 1A Output Current 118mΩ and 88mΩ Internal Power MOSFET Switches Cycle-by-Cycle Over Current Protection Short Circuit Protect with Hiccup Mode Stable with Low ESR Output Ceramic Capacitors APPLICATIONS Wireless/Networking Cards Portable Instruments Battery Powered Devices Low Voltage I/O System Power All MPS parts are lead-free and adhere to the RoHS directive. For MPS green status, please visit MPS website under Products, Quality Assurance page. “MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION MP2158 Rev. 1.0 10/10/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 1 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER ORDERING INFORMATION Part Number* MP2158GQH Package QFN8 (2.0x1.5mm) Top Marking BE * For Tape & Reel, add suffix –Z (e.g. MP2158GQH–Z); PACKAGE REFERENCE TOP VIEW EN 1 8 PG FB 2 7 VIN AGND 3 6 SW OUT 4 5 PGND QFN2.0x1.5-8 ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Supply Voltage VIN ...................................... 6.5V VSW ...................................................................... -0.3V (-1.5V for <10ns) to 6.5V (7V for <10ns) All Other Pins ................................ -0.3V to 6.5 V Junction Temperature ...............................150C Lead Temperature ....................................260C (2) Continuous Power Dissipation (TA = +25°C) ……….….. ............................................... 1.14W Storage Temperature ............... -65C to +150C QFN8 (2.0x1.5mm) ................ 110 ..... 55... C/W Recommended Operating Conditions (3) Supply Voltage VIN ............................. 2.5V to 6V Operating Junction Temp. (TJ). -40°C to +125°C MP2158 Rev. 1.0 10/10/2012 (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 will cause excessive die temperature, and the regulator will 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. © 2012 MPS. All Rights Reserved. 2 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER ELECTRICAL CHARACTERISTICS (5) VIN = 5V, TA = +25C, unless otherwise noted. Parameter Symbol Feedback Voltage VFB Feedback Current PFET Switch On Resistance NFET Switch On Resistance IFB RDSON RDSON Condition 2.5V ≤ VIN ≤ 6V o o TA=-40 C to +85 C (6) Min Typ Max -3% 0.600 +3% -3.5% VFB = 0.6V P N VEN = 0V, VIN = 6V VSW = 0V and 6V Switch Leakage PFET Current Limit ON Time TON Switching frequency Minimum Off Time Soft-Start Time Fs -20% -25% TMIN-OFF TSS-ON Power Good Upper Trip Threshold PGH Power Good Lower Trip Threshold Power Good Delay Power Good Sink Current Capability Power Good Logic High Voltage Power Good Internal Pull Up Resistor Under Voltage Lockout Threshold Rising Under Voltage Lockout Threshold Hysteresis EN Input Logic Low Voltage EN Input Logic High Voltage PGL PGD EN Input Current Supply Current (Shutdown) Supply Current (Quiescent) Thermal Shutdown(5) Thermal Hysteresis VIN=5V, VOUT=1.2V VIN=3.6V, VOUT=1.2V VOUT=1.2V TA=-40oC to +85oC(6) (5) FB voltage respect to the regulation VPG-L Sink 1mA VPG-H VIN=5V, VFB=0.6V +3.5% 50 nA mΩ mΩ 0 1 μA 2 185 245 1500 1500 60 1.5 A ns +20% +25% % -10 50 % μs V V 550 2.3 kΩ 2.45 260 1.2 1.5 0 0 17 V mV 0.4 VEN=2V VEN=0V VEN=0V VEN=2V, VFB=0.63V, VIN=5V kHz/% kHz/% ns ms +10 4.9 2.15 V/% 10 118 88 0.4 RPG Units 1 20 V V μA μA μA μA 150 C 30 C Notes: 5) Guaranteed by design. 6) Guaranteed by characterization test. MP2158 Rev. 1.0 10/10/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 3 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER TYPICAL PERFORMANCE CHARACTERISTICS VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted. MP2158 Rev. 1.0 10/10/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 4 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted. MP2158 Rev. 1.0 10/10/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 5 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 5V, VOUT = 1.2V, L = 1.0µH, TA = +25ºC, unless otherwise noted MP2158 Rev. 1.0 10/10/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 6 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER PIN FUNCTIONS Pin # 8 7 6 5 4 3 2 1 MP2158 Rev. 1.0 10/10/2012 Name Description Power Good Indicator. The output of this pin is an open drain with internal pull up resistor PG to IN. PGOOD is pulled up to IN when the FB voltage is within 10% of the regulation level, if FB voltage is out of that regulation range, it is LOW. Supply Voltage. The MP2158 operates from a +2.5V to +6V unregulated input. C1 is VIN needed to prevent large voltage spikes from appearing at the input. SW Switch Output PGND Power ground OUT Input sense pin for output voltage AGND Analogy ground for internal control circuit Feedback pin. An external resistor divider from the output to GND, tapped to the FB pin, FB sets the output voltage. EN On/Off Control www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 7 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER BLOCK DIAGRAM VIN Bias & Voltage Reference EN Soft start + COMP VTH Lo-Iq 0.6V RST + + E.A. - Constant On- Time Pulse PDRV PWM Main Switch (PCH) PWM + Lo-Iq + FB SW EN FBCOMP Driver VOUT Lo-Iq Ramp generator Synchronous Rectifier ( NCH) SW Lo-Iq Hi-Z NDRV OUT GND IN FB for fixed output 0.66V + + COMP COMP - Lo-Iq + COMP 0.54V PG - Figure 1: MP2158 Block Diagram MP2158 Rev. 1.0 10/10/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 8 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER OPERATION MP2158 uses constant on-time control with input voltage feed forward to stabilize the switching frequency over full input range. At light load, MP2158 employs a proprietary control of low side switch and inductor current to eliminate ringing on switching node and improve efficiency. Constant On-time Control Compare to fixed frequency PWM control, constant on-time control offers the advantage of simpler control loop and faster transient response. By using input voltage feed forward, MP2158 maintains a nearly constant switching frequency across input and output voltage range. The ontime of the switching pulse can be estimated as: TON VOUT 0.667s VIN To prevent inductor current run away during load transient, MP2158 fixes the minimum off time to be 60ns. However, this minimum off time limit will not affect operation of MP2158 in steady state in any way. Light Load Operation In light load condition, MP2158 uses a proprietary control scheme to save power and improve efficiency. The MP2158 will turn off the low side switch when inductor current starts to reverse. Then MP2158 works in discontinuous conduction mode (DCM) operation. Enable When input voltage is greater than the undervoltage lockout threshold (UVLO), typically 2.3V, MP2158 can be enabled by pulling EN pin to higher than 1.2V. Leaving EN pin float or pull down to ground will disable MP2158. There is MP2158 Rev. 1.0 10/10/2012 an internal 1Meg Ohm resistor from EN pin to ground. Soft Start MP2158 has built-in soft start that ramps up the output voltage in a controlled slew rate, avoiding overshoot at startup. The soft start time is about 1.5ms typical. Power GOOD Indictor MP2158 has an open drain with 550kΩ pull-up resistor pin for power good indicator PGOOD. When FB pin is within +/-10% of regulation voltage, i.e. 0.6V, PGOOD pin is pulled up to IN by the internal resistor. If FB pin voltage is out of the +/-10% window, PGOOD pin is pulled down to ground by an internal MOS FET. The MOS FET has a maximum Rdson of less than 150Ω. Current limit MP2158 has a typical 2A current limit for the high side switch. When the high side switch hits current limit, MP2158 will touch the hiccup threshold until the current lower down. This will prevent inductor current from continuing to build up which will result in damage of the components. Short Circuit and Recovery MP2158 enters short circuit protection mode also when the current limit is hit, and tries to recover from short circuit with hiccup mode. In short circuit protection, MP2158 will disable output power stage, discharge soft-start cap and then automatically try to soft-start again. If the short circuit condition still holds after softstart ends, MP2158 repeats this operation cycle till short circuit disappears and output rises back to regulation level. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 9 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER APPLICATION INFORMATION COMPONENT SELECTION Setting the Output Voltage The external resistor divider is used to set the output voltage (see Typical Application on page 1). The feedback resistor R1 can not be too large neither too small considering the trade-off for stability and dynamic. Choose R1 to be around 120kΩ to 200kΩ. R2 is then given by: R2 R1 Vout 1 0.6 The feedback circuit is shown as Figure 2. Figure 2: Feedback Network Table 1 lists the recommended resistors value for common output voltages. Table 1—Resistor Selection for Common Output Voltages VOUT (V) R1 (kΩ) R2 (kΩ) 1.0 1.2 1.8 2.5 3.3 200(1%) 200(1%) 200(1%) 200(1%) 200(1%) 300(1%) 200(1%) 100(1%) 63.2(1%) 44.2(1%) Selecting the Inductor A 0.68µH to 2.2µH inductor is recommended for most applications. For highest efficiency, the inductor DC resistance should be less than 15mΩ. For most designs, the inductance value can be derived from the following equation. L1 VOUT (VIN VOUT ) VIN IL fOSC Where ΔIL is the inductor ripple current. MP2158 Rev. 1.0 10/10/2012 Choose inductor current to be approximately 30% of the maximum load current. The maximum inductor peak current is: IL(MAX) ILOAD I L 2 Selecting the Input Capacitor The input current to the step-down converter is discontinuous, therefore a capacitor is required to supply the 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 and small temperature coefficients. For most applications, a 10µF capacitor is sufficient. For higher output voltage, 47uF may be needed for more stable system. 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 by: I C1 ILOAD VOUT VOUT 1 VIN VIN The worse case condition occurs at VIN = 2VOUT, where: IC1 ILOAD 2 For simplification, choose the input capacitor whose 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, a small and high quality ceramic capacitor, i.e. 0.1μF, should be placed as close to the IC as possible. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. The input voltage ripple caused by capacitance can be estimated by: VIN ILOAD V V OUT 1 OUT fS C1 VIN VIN www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 10 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER VOUT VOUT VOUT 1 1 RESR fS L1 VIN 8 fS C2 Where L1 is the inductor value and RESR is the equivalent series resistance (ESR) value of the output capacitor. Using ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. The output voltage ripple is mainly caused by the capacitance. For simplification, the output voltage ripple can be estimated by: ΔVOUT V VOUT 1 OUT 2 VIN 8 fS L1 C2 In the case of tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: ΔVOUT V V OUT 1 OUT RESR fS L1 VIN The characteristics of the output capacitor also affect the stability of the regulation system. PCB Layout Proper layout of the switching power supplies is very important, and sometimes critical for proper function. For the high-frequency switching converter, poor layout design can result in poor line or load regulation and stability issues. The high current paths (GND, IN and SW) should be placed very close to the device with short, direct and wide traces. The input capacitor needs to be as close as possible to the IN and GND pins. The external feedback resistors should be placed next to the FB pin. Keep the switching node SW short and away from the feedback network. EN PG AGND R2 R1 Selecting the Output Capacitor The output capacitor (C2) is required to maintain the DC output voltage. Ceramic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: 1 8 2 7 3 6 4 5 C1 C2 SW OUT GND VIN Figure 3: PCB Layout Recommendation Design Example Below is a design example following the application guidelines for the specifications: Table 2: Design Example VIN 5V VOUT 1.2V fSW 1500kHz The detailed application schematic is shown in Figure 4. The typical performance and circuit waveforms have been shown in the Typical Performance Characteristics section. For more device applications, please refer to the related Evaluation Board Datasheets. MP2158 Rev. 1.0 10/10/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 11 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER TYPICAL APPLICATION CIRCUITS Figure 4: Typical Application Circuit MP2158 Rev. 1.0 10/10/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 12 MP2158 – 1A, 6V, 1.5MHz SYNCHRONOUS STEP-DOWN SWITCHER PACKAGE INFORMATION QFN8 (2.0X1.5mm) PIN 1 ID PIN 1 ID MARKING PIN 1 ID INDEX AREA BOTTOM VIEW TOP VIEW SIDE VIEW NOTE: 0.125 X 45 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH. 3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETERS MAX. 4) JEDEC REFERENCE IS MO-220. 5) DRAWING IS NOT TO SCALE. RECOMMENDED LAND PATTERN NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications. 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. MP2158 Rev. 1.0 10/10/2012 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 13