EVALUATION KIT AVAILABLE MAX618 28V Internal Switch, Step-Up DC-DC Converter General Description The MAX618 CMOS, PWM, step-up DC-DC converter generates output voltages up to 28V and accepts inputs from +3V to +28V. An internal 2A, 0.3 switch eliminates the need for external power MOSFETs while supplying output currents up to 500mA or more. A PWM control scheme combined with Idle ModeTM operation at light loads minimizes noise and ripple while maximizing efficiency over a wide load range. No-load operating current is 500A, which allows efficiency up to 93%. A fast 250kHz switching frequency allows the use of small surface-mount inductors and capacitors. A shutdown mode extends battery life when the device is not in use. Adaptive slope compensation allows the MAX618 to accommodate a wide range of input and output voltages with a simple, single compensation capacitor. The MAX618 is available in a thermally enhanced 16-pin QSOP package that is the same size as an industrystandard 8-pin SO but dissipates up to 1W. An evaluation kit (MAX618EVKIT) is available to help speed designs. Applications Features Adjustable Output Voltage Up to +28V Up to 93% Efficiency Wide Input Voltage Range (+3V to +28V) Up to 500mA Output Current at +12V 500A Quiescent Supply Current 3A Shutdown Current 250kHz Switching Frequency Small 1W, 16-Pin QSOP Package Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX618EEE+ -40C to +85C 16 QSOP +Denotes a lead(Pb)-free/RoHS-compliant package. Typical Application Circuit Industrial +24V and +28V Systems LCD Displays Palmtop Computers VIN 3V TO 28V Pin Configuration TOP VIEW GND 1 + 16 GND LX 4 MAX618 14 PGND 13 PGND SHDN 5 12 GND COMP 6 11 VL FB 7 10 IN 9 GND 8 GND QSOP Idle Mode is a trademark of Maxim Integrated Products, Inc. 19-1462; Rev 2; 4/15 MAX618 SHDN LX PGND 15 PGND LX 2 LX 3 IN VL COMP FB GND VOUT UP TO 28V MAX618 28V Internal Switch, Step-Up DC-DC Converter Absolute Maximum Ratings IN to GND ...............................................................-0.3V to +30V LX to GND ..............................................................-0.3V to +30V VL to GND ................................................................-0.3V to +6V SHDN, COMP, FB to GND ............................-0.3V to (VL + 0.3V) PGND to GND.....................................................................0.3V Continuous Power Dissipation (TA = +70C) (Note 1) 16-Pin QSOP (derate 15mW/C above +70C)...................1W Operating Temperature Range ...........................-40C to +85C Junction Temperature......................................................+150C Storage Temperature Range .............................-65C to +150C Soldering Temperature (reflow) .......................................+260C Note 1: With part mounted on 0.9 in.2 of copper. Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Electrical Characteristics (VIN = +6V, PGND = GND, CVL = 4.7F, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER SYMBOL CONDITIONS Input Voltage VIN Supply Current, No Load IIN VIN = 3V to 28V, VFB = 1.6V, SHDN = VL Supply Current, Full Load, VL Connected to IN IIN VIN = 3V to 5.5V, VFB = 1.4V, SHDN = VL = IN Supply Current, Full Load IIN VIN = 3.4V to 28V, VFB = 1.4V, SHDN = VL, VVL < VIN Shutdown Supply Current IIN VIN = 28V, VFB = 1.6V, SHDN = GND VL Output Voltage VVL VIN = 3.5V or 28V, no load VL Load Regulation DVVL VL Undervoltage Lockout VFB FB Input Bias Current IFB TYP MAX UNITS 28 V 500 700 A 5 6.5 mA 2.5 3.5 mA 3 8 A 2.9 3.05 3.2 V 25 40 mV 2.58 2.7 2.8 V 1.47 1.5 1.53 V 1 50 nA 0.08 %/V 3 ILOAD = 0 to 2mA, VFB = 1.6V Rising edge, 1% hysteresis FB Set Voltage MIN VFB = 1.6V Line Regulation DVOUT VIN = 3V to 6V,VOUT = 12V 0.01 Load Regulation DVOUT VOUT = 12V, ILOAD = 10mA to 500mA 0.2 LX Voltage LX Switch Current Limit VLX ILXON PWM mode Idle Mode Current Limit Threshold % 28 V 1.7 2.2 2.7 A 0.25 0.35 0.45 A 0.3 0.6 0.02 10 A LX On-Resistance RLXON LX Leakage Current ILXOFF VLX = 28V COMP Maximum Output Current ICOMP FB = GND 100 200 A DFB = 0.1V 0.8 1 mmho COMP Voltage to Switch Current Transconductance SHDN Input Logic Low VIL SHDN Input Logic High VIH Shutdown Input Current V 1 A 300 kHz 2.0 V SHDN = GND or VL Switching Frequency f 200 250 Maximum Duty Cycle DC 90 95 www.maximintegrated.com 0.8 % Maxim Integrated 2 MAX618 28V Internal Switch, Step-Up DC-DC Converter Electrical Characteristics (continued) (VIN = +6V, PGND = GND, CVL = 4.7F, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER SYMBOL MAX UNITS 28 V VIN = 3V to 28V, VFB = 1.6V, SHDN = VL 800 A IIN VIN = 3V to 5.5, VFB = 1.4V, SHDN = VL = IN 7.5 mA Supply Current, Full Load IIN VIN = 3.4V to 28V, VFB = 1.4V, SHDN = VL, VVL < VIN 4 mA Supply Current Shutdown IIN VIN = 28V, VFB = 1.6V, SHDN = GND 10 A VL Output Voltage VVL VIN = 3.5V or 28V, no load 3.3 V VL Undervoltage Lockout VVL Rising edge, 1% hysteresis 2.55 2.85 V FB Set Voltage VFB 1.455 1.545 V 28 V 3 A 0.6 312 kHz Input Voltage VIN Supply Current, No Load IIN Supply Current, Full Load, VL Connected to IN MIN TYP 3 LX Voltage Range VLXON LX Switch Current Limit ILXON LX On-Resistance RLXON Switching Frequency CONDITIONS 2.85 PWM mode 1.4 f 188 Note 2: Specifications to -40C are guaranteed by design, not production tested. Typical Operating Characteristics (Circuit of Figure 1, TA = +25C.) VIN = 5V 60 50 40 30 VIN = 5V 80 EFFICIENCY (%) EFFICIENCY (%) 70 VIN = 12V 90 VIN = 3V 70 60 50 40 30 500 460 440 420 400 380 20 360 10 10 340 0 0 1 10 100 OUTPUT CURRENT (mA) www.maximintegrated.com 1000 0.1 1 10 100 OUTPUT CURRENT (mA) 1000 VOUT = 12V 480 20 0.1 NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX618 toc03 VIN = 3V 80 100 SUPPLY CURRENT (A) VIN = 8V 90 MAX618 toc01 100 EFFICIENCY vs. OUTPUT CURRENT (VOUT = 28V) MAX618 toc02 EFFICIENCY vs. OUTPUT CURRENT (VOUT = 12V) 320 2 3 4 5 6 7 8 9 10 11 12 SUPPLY VOLTAGE (V) Maxim Integrated 3 MAX618 28V Internal Switch, Step-Up DC-DC Converter Typical Operating Characteristics (continued) (Circuit of Figure 1, TA = +25C.) 0.50 0.45 600 550 VIN = 5V 500 VIN = 8V 450 400 350 5 10 15 20 INPUT VOLTAGE (V) 25 30 300 -50 -30 -10 10 30 50 70 TEMPERATURE (C) 90 MAX618 toc06 1.5 1.0 2 7 VOUT (100mV/div) VOUT (100mV/ div) MAX618 toc09 6V VIN (5V/div) 3V 2s/div VIN = 5V, VOUT = 12V, IOUT = 200mA 2ms/div IOUT = 200mA, VOUT = 12V VIN = 5V, VOUT = 12V, IOUT = 500mA MAXIMUM OUTPUT CURRENT vs. INPUT VOLTAGE SHUTDOWN RESPONSE LOAD-TRANSIENT RESPONSE MAX618 toc11 MAX618 toc10 SHDN (2V/div) 1.6 0 12V IOUT (100mA/div) 0 32 0 VLX (10V/div) VOUT (200mV/div) 27 VOUT (50mV/div) 0 2s/div 12 17 22 SUPPLY VOLTAGE (V) LINE-TRANSIENT RESPONSE MAX618 toc08 VLX (10V/div) VOUT (2V/div) 5V www.maximintegrated.com 2.0 0 110 IL (1A/div) VIN = 5V, VOUT = 12V 2.5 HEAVY-LOAD SWITCHING WAVEFORMS MAX618 toc07 5ms/div 3.0 0.5 INCLUDES CAPACITOR LEAKAGE CURRENT MEDIUM-LOAD SWITCHING WAVEFORMS IL (1A/div) 3.5 500s/div VIN = 5V, VOUT = 12V, ILOAD = 500mA MAXIMUM OUTPUT CURRENT (A) 0 4.0 MAX618 toc12 0.55 VIN = 3V 650 SHUTDOWN CURRENT (A) MAX618 toc04 0.60 0.40 700 SUPPLY CURRENT (A) SUPPLY CIRRENT (A) 0.65 SHUTDOWN CURRENT vs. SUPPLY VOLTAGE SUPPLY CURRENT vs. TEMPERATURE MAX618 toc05 NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE VOUT = 12V 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 2 3 4 5 6 7 8 9 INPUT VOLTAGE (V) 10 11 12 Maxim Integrated 4 MAX618 28V Internal Switch, Step-Up DC-DC Converter Pin Description PIN NAME FUNCTION 1, 8, 9, 12, 16 GND 2, 3, 4 LX 5 SHDN Shutdown Input. A logic low puts the MAX618 in shutdown mode and reduces supply current to 3A. SHDN must not exceed VL. In shutdown, the output falls to VIN less one diode drop. 6 COMP Compensation Input. Bypass to GND with the value of capacitance shown in Table 2. 7 FB Feedback Input. Connect a resistor-divider network to set VOUT. FB threshold is 1.5V. 10 IN LDO Regulator Supply Input. IN accepts inputs up to +28V. Bypass to GND with a 1F ceramic capacitor as close to pins 10 and 12 as possible. 11 VL Internal 3.1V LDO Regulator Output. Bypass to GND with a 4.7F capacitor. 13, 14, 15 PGND Ground Drain of Internal n-channel Switch. Connect the inductor between IN and LX. Power Ground. Source of internal N-channel switch. LOW BATTERY INPUT +5V INPUT R3 169k LBD 8 MAX618 1 LBR R4 100k LOW-BATTERY OUTPUT (LOW IF INPUT < 3V) COMP 2 1.31V L1 470 2 CX OSC 40kHz R2 47.5k VFB 7 R1 499k COMP 1 CC 3 LX D1 1N4148 SHUTDOWN IC 6 RON AT 3 4 GND OPERATE 1.31V BANDGAP REFERENCE AND BIAS GENERATOR +VS 5 C1 470mF 25V +15V OUTPUT 20mA Figure 1. Single-Supply Operation www.maximintegrated.com Maxim Integrated 5 MAX618 28V Internal Switch, Step-Up DC-DC Converter Detailed Description The MAX618 pulse-width modulation (PWM) DC-DC converter with an internal 28V switch operates in a wide range of DC-DC conversion applications including boost, SEPIC, and flyback configurations. The MAX618 uses fixed-frequency PWM operation and Maxim's proprietary Idle Mode control to optimize efficiency over a wide range of loads. It also features a shutdown mode to minimize quiescent current when not in operation. PWM Control Scheme and Idle Mode Operation The MAX618 combines continuous-conduction PWM operation at medium to high loads and Idle Mode operation at light loads to provide high efficiency over a wide range of load conditions. The MAX618 control scheme actively monitors the output current and automatically switches between PWM and Idle Mode to optimize efficiency and load regulation. Figure 2 shows a functional diagram of the MAX618's control scheme. The MAX618 normally operates in low-noise, continuousconduction PWM mode, switching at 250kHz. In PWM mode, the internal MOSFET switch turns on with each clock pulse. It remains on until either the error comparator trips or the inductor current reaches the 2A switch-current limit. The error comparator compares the feedback-error signal, current-sense signal, and slope-compensation signal in one circuit block. When the switch turns off, energy transfers from the inductor to the output capacitor. Output current is limited by the 2A MOSFET current limit IDLE MODE CURRENT LIMIT MAX618 PWM CURRENT LIMIT CURRENTSENSE CIRCUIT PGND IN VL ERROR COMPARATOR PWM LOGIC 250kHz OSCILLATOR GND SLOPE COMPENSATION NMOS R LX FB 14R REFERENCE INTEGRATOR SHDN SHUTDOWN THERMAL SHUTDOWN OUT COMP LINEAR REGULATOR IN VL Figure 2. Functional Diagram www.maximintegrated.com Maxim Integrated 6 MAX618 28V Internal Switch, Step-Up DC-DC Converter and the MAX618's package power-dissipation limit. See the Maximum Output Current section for details. In Idle Mode, the MAX618 improves light-load efficiency by reducing inductor current and skipping cycles to reduce the losses in the internal switch, diode, and inductor. In this mode, a switching cycle initiates only when the error comparator senses that the output voltage is about to drop out of regulation. When this occurs, the NMOS switch turns on and remains on until the inductor current exceeds the nominal 350mA Idle Mode current limit. Refer to Table 1 for an estimate of load currents at which the MAX618 transitions between PWM and Idle Mode. Compensation Scheme Although the higher loop gain of voltage-controlled architectures tends to provide tighter load regulation, current-controlled architectures are generally easier to compensate over wide input and output voltage ranges. The MAX618 uses both control schemes in parallel: the dominant, low-frequency components of the error signal are tightly regulated with a voltage-control loop, while a current-control loop improves stability at higher www.maximintegrated.com frequencies. Compensation is achieved through the selection of the output capacitor (COUT), the integrator capacitor (CCOMP), and the pole capacitor (CP) from FB to GND. CP cancels the zero formed by COUT and its ESR. Refer to the Capacitor Selection section for guidance on selecting these capacitors. VL Low-Dropout Regulator The MAX618 contains a 3.1V low-dropout linear regulator to power internal circuitry. The regulator's input is IN and its output is VL. The IN to VL dropout voltage is 100mV, so that when IN is less than 3.2V, VL is typically 100mV below IN. The MAX618 still operates when the LDO is in dropout, as long as VL remains above the 2.7V undervoltage lockout. Bypass VL with a 4.7F ceramic capacitor placed as close to the VL and GND pins as possible. VL can be overdriven by an external supply between 2.7V and 5.5V. In systems with +3.3V or +5V logic power supplies available, improve efficiency by powering VL and VIN directly from the logic supply as shown in Figure 3. Maxim Integrated 7 15 16 VOUT 17 18 19 20 21 22 23 24 25 26 27 28 www.maximintegrated.com 0.22 0.15 0.19 0.20 0.21 0.21 0.20 0.20 0.19 0.18 0.17 0.17 0.16 0.15 0.14 0.14 0.13 0.23 0.15 0.18 0.20 0.21 0.21 0.21 0.20 0.20 0.19 0.18 0.18 0.17 0.16 0.15 0.15 0.24 0.16 0.17 0.19 0.20 0.21 0.21 0.20 0.20 0.19 0.19 0.18 0.17 0.17 0.16 0.25 0.17 0.17 0.19 0.20 0.21 0.21 0.21 0.20 0.20 0.19 0.19 0.18 0.17 0.25 0.18 0.16 0.18 0.20 0.20 0.21 0.21 0.21 0.20 0.20 0.19 0.19 0.26 0.19 0.16 0.18 0.19 0.20 0.21 0.21 0.21 0.20 0.20 0.20 0.26 0.20 0.15 0.17 0.19 0.20 0.20 0.21 0.21 0.21 0.20 0.27 0.20 0.15 0.17 0.19 0.20 0.20 0.21 0.21 0.21 0.27 0.21 0.16 0.17 0.18 0.19 0.20 0.21 0.21 0.27 0.21 0.17 0.16 0.18 0.19 0.20 0.20 0.28 0.22 0.17 0.16 0.18 0.19 0.20 0.28 0.22 0.18 0.15 0.17 0.19 0.28 0.23 0.18 0.15 0.17 0.28 0.23 0.19 0.15 0.29 0.24 0.19 0.29 0.24 0.29 11 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 0.21 0.16 0.19 0.20 0.21 0.21 0.20 0.19 0.18 0.17 0.17 0.16 0.15 0.14 0.13 0.13 0.12 0.11 12 0.20 0.17 0.20 0.21 0.21 0.20 0.19 0.18 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.12 0.11 0.10 0.10 9 10 0.19 0.18 0.20 0.21 0.20 0.20 0.19 0.17 0.16 0.15 0.14 0.13 0.13 0.12 0.11 0.10 0.10 0.09 0.09 0.08 14 8 13 0.17 0.19 0.21 0.21 0.20 0.19 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.10 0.10 0.09 0.08 0.08 0.07 0.07 0.07 12 0.15 0.20 0.21 0.20 0.19 0.18 0.16 0.15 0.13 0.12 0.11 0.10 0.10 0.09 0.08 0.08 0.07 0.07 0.06 0.06 0.05 0.05 11 7 10 6 9 0.16 0.20 0.21 0.19 0.17 0.16 0.14 0.13 0.11 0.10 0.09 0.09 0.08 0.07 0.07 0.06 0.06 0.05 0.05 0.04 0.04 0.04 0.04 8 0.18 0.21 0.20 0.17 0.15 0.13 0.12 0.10 0.09 0.08 0.07 0.07 0.06 0.05 0.05 0.04 0.04 0.04 0.03 0.03 0.03 0.03 0.03 0.03 7 5 6 4 5 0.20 0.20 0.18 0.15 0.12 0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.04 0.04 0.03 0.03 0.03 0.03 0.03 0.02 0.02 0.02 0.02 0.02 0.02 4 3 VIN Table 1. PWM/Idle-Mode Transition Load Current (IOUT in Amps) vs. Input and Output Voltage MAX618 28V Internal Switch, Step-Up DC-DC Converter Maxim Integrated 8 MAX618 28V Internal Switch, Step-Up DC-DC Converter Operating Configurations conversion power (inductor voltage). The logic supply (between 2.7V and 5.5V) connects to VL and IN. VL = IN; voltages of 3.3V or more improve efficiency by providing greater gate drive for the internal MOSFET. The MAX618 can be connected in one of three configurations described in Table 2 and shown in Figures 1, 3, and 4. The VL linear regulator allows operation from a single supply between +3V and +28V as shown in Figure 1. The circuit in Figure 4 allows separate supplies to power IN and the inductor voltage. It differs from the connection in Figure 3 in that the MAX618 chip supply is not limited to 5.5V. The circuit in Figure 3 allows a logic supply to power the MAX618 while using a separate source for DC-DC Table 2. Input Configurations CIRCUIT CONNECTION Figure 1 Input voltage connects to IN and inductor. Figure 3 IN and VL connect together. Inductor voltage supplied by a separate source. Figure 4 IN and inductor voltage supplied by separate sources. VIND UP TO 28V VIN RANGE INDUCTOR VOLTAGE 3V to VOUT (up to 28V) VIN 2.7V to 5.5V 0V to VOUT (up to 28V) 3V to 28V 0V to VOUT (up to 28V) BENEFITS/COMMENTS * * Single supply operation. SHDN must be connected to or pulled up to VL. On/off control requires an open-drain or open-collector connection to SHDN. * * Increased efficiency. SHDN can be driven by logic powered from the supply connected to IN and VL, or can be connected to or pulled up to VL. Input power source (inductor voltage) is separate from the MAX618's bias (VIN = VL) and can be less than or greater than VIN. * * * Input power source (inductor voltage) is separate from the MAX618's bias (VIN) and can be less than or greater than VIN. SHDN must be connected to or pulled up to VL. On/off control requires an open-drain or open-collector connection to SHDN. VIND UP TO 28V L CIND IN 2.7V TO 5.5V CIND IN 1F OUT UP TO 28V LX MAX618 IN 3V TO 28V 4.7F FB CP GND Figure 3. Dual-Supply Operation (VIN = 2.7V to 5.5V) www.maximintegrated.com COUT MAX618 PGND R1 VL VL COMP OUT UP TO 28V LX SHDN R1 PGND CCOMP IN 1F COUT SHDN 4.7F L R2 CCOMP FB COMP CP R2 GND Figure 4. Dual-Supply Operation (VIN = 3V to 28V) Maxim Integrated 9 MAX618 28V Internal Switch, Step-Up DC-DC Converter Shutdown Mode In shutdown mode (SHDN = 0), the MAX618's feedback and control circuit, reference, and internal biasing circuitry turn off and reduce the IN supply current to 3A (10A max). When in shutdown, a current path remains from the input to the output through the external inductor and diode. Consequently, the output falls to VIN less one diode drop in shutdown. SHDN may not exceed VL. For always-on operation, connect SHDN to VL. To add on/off control to the circuit of Figure 1 or 4, pull SHDN to VL with a resistor (10k to 100k) and drive SHDN with an open-drain logic gate or switch as shown in Figure 5. Alternatively, the circuit of Figure 3 allows direct SHDN drive by any logic-level gate powered from the same supply that powers VL and IN, as shown in Figure 6. Design Procedure The MAX618 operates in a number of DC-DC converter configurations including step-up, SEPIC, and flyback. The following design discussion is limited to step-up converters. Setting the Output Voltage Two external resistors (R1 and R2) set the output voltage. First, select a value for R2 between 10k and 200k. Calculate R1 with: V = R 1 R 2 OUT - 1 VFB where VFB is 1.5V. Determining the Inductor Value The MAX618's high switching frequency allows the use of a small value inductor. The recommended inductor value is proportional to the output voltage and is given by the following: L= VOUT 7 x 10 5 After solving for the above equation, round down as necessary to select a standard inductor value. When selecting an inductor, choose one rated to 250kHz, with a saturation current exceeding the peak inductor current, and with a DC resistance under 200m. Ferrite core or equivalent inductors are generally appropriate (see MAX618 EV kit data sheet). Calculate the peak inductor current with the following equation: = ILX(PEAK) I OUT - VIN ) VOUT V (V + 2s IN OUT VIN VOUT L Note that the peak inductor current is internally limited to 2A. Diode Selection The MAX618's high switching frequency demands a highspeed rectifier. Schottky diodes are preferred for most applications because of their fast recovery time and low forward voltage. Make sure that the diode's peak current rating exceeds the 2A peak switch current, and that its breakdown voltage exceeds the output voltage. MAX618 MAX618 VL OPEN-DRAIN LOGIC SYSTEM LOGIC SUPPLY 100k ON/OFF CONTROL SHDN Figure 5. Adding On/Off Control to Circuit of Figure 1 or 4 www.maximintegrated.com IN SYSTEM LOGIC VL ON/OFF CONTROL SHDN Figure 6. Adding On/Off Control to Circuit of Figure 3 Maxim Integrated 10 MAX618 28V Internal Switch, Step-Up DC-DC Converter Maximum Output Current The MAX618's 2.2A LX current limit determines the output power that can be supplied for most applications. In some cases, particularly when the input voltage is low, output power is sometimes restricted by package dissipation limits. The MAX618 is protected by a thermal shutdown circuit that turns off the switch when the die temperature exceeds +150C. When the device cools by 10C, the switch is enabled again. Table 3 details output current with a variety of input and output voltages. Each listing in Table 3 is either the limit set by an LX current limit or by package dissipation at +85C ambient, whichever is lower. The values in Table 3 assume a 40m inductor resistance. Capacitor Selection Input Capacitors The input bypass capacitor (CIND) reduces the input ripple created by the boost configuration. High-impedance sources require high CIND values. However, 68F is generally adequate for input currents up to 2A. Low-ESR capacitors are recommended because they will decrease the ripple created on the input and improve efficiency. Capacitors with ESR below 0.3 are generally appropriate. In addition to the input bypass capacitor, bypass IN with a 1F ceramic capacitor placed as close to the IN and GND pins as possible. Bypass VL with a 4.7F ceramic capacitor placed as close to the VL and GND pins as possible. Output Capacitor Use Table 4 to find the minimum output capacitance necessary to ensure stable operation. In addition, choose an output capacitor with low ESR to reduce the output ripple. The dominant component of output ripple is the product of the peak-to-peak inductor ripple current and the ESR of the output capacitor. ESR below 50m generates acceptable levels of output ripple for most applications. Integrator Capacitor The compensation capacitor (CCOMP) sets the dominant pole in the MAX618's transfer function. The proper compensation capacitance depends upon output capacitance. Table 5 shows the capacitance value needed for the output capacitances specified in Table 4. However, if a www.maximintegrated.com different output capacitor is used (e.g., a standard value), then recalculate the value of capacitance needed for the integrator capacitor with the following formula: C COMP (Table 5) x C OUT C OUT (Table 4) C COMP = Pole Compensation Capacitor The pole capacitor (CP) cancels the unwanted zero introduced by COUT's ESR, and thereby ensures stability in PWM operation. The exact value of the pole capacitor is not critical, but it should be near the value calculated by the following equation: CP = R ESR x C OUT (R 1 + R 2 ) R1 x R 2 where RESR is COUT's ESR. Layout Considerations Proper PC board layout is essential due to high current levels and fast switching waveforms that radiate noise. Use the MAX618 evaluation kit or equivalent PC layout to perform initial prototyping. Breadboards, wire-wrap, and proto-boards are not recommended when prototyping switching regulators. It is important to connect the GND pin, the input bypass capacitor ground lead, and the output filter capacitor ground lead to a single point to minimize ground noise and improve regulation. Also, minimize lead lengths to reduce stray capacitance, trace resistance, and radiated noise, with preference given to the feedback circuit, the ground circuit, and LX. Place the feedback resistors as close to the FB pin as possible. Place a 1F input bypass capacitor as close as possible to IN and GND. Refer to the MAX618 evaluation kit for an example of proper board layout. Chip Information PROCESS: BiCMOS Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 16 QSOP EF16+8F 21-0055 Maxim Integrated 11 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 VIN 4 5 6 7 0.77 0.59 0.49 0.41 0.96 0.76 0.64 1.09 0.89 1.18 8 0.34 0.56 0.76 0.99 1.26 9 0.29 0.49 0.67 0.85 1.07 1.32 10 0.25 0.43 0.60 0.76 0.93 1.13 1.37 11 0.22 0.38 0.54 0.68 0.83 1.00 1.19 1.41 12 0.20 0.34 0.50 0.63 0.76 0.90 1.06 1.24 1.44 13 0.18 0.31 0.45 0.58 0.70 0.82 0.96 1.11 1.28 1.47 14 0.17 0.28 0.41 0.54 0.65 0.76 0.88 1.01 1.15 1.31 1.49 15 0.15 0.26 0.37 0.50 0.60 0.71 0.81 0.93 1.05 1.19 1.34 1.52 16 0.14 0.24 0.34 0.46 0.57 0.66 0.76 0.86 0.97 1.10 1.23 1.37 1.53 VOUT 17 0.13 0.22 0.32 0.42 0.53 0.62 0.71 0.81 0.91 1.02 1.13 1.26 1.40 1.55 18 0.12 0.21 0.30 0.39 0.50 0.59 0.67 0.76 0.85 0.95 1.05 1.16 1.29 1.42 1.57 Table 3. Typical Output Current vs. Input and Output Voltages 19 0.12 0.19 0.28 0.37 0.46 0.56 0.64 0.72 0.80 0.89 0.99 1.09 1.19 1.31 1.44 1.58 20 0.11 0.18 0.26 0.34 0.43 0.53 0.61 0.68 0.76 0.84 0.93 1.02 1.12 1.22 1.33 1.46 1.59 21 0.10 0.17 0.25 0.32 0.41 0.50 0.58 0.65 0.72 0.80 0.88 0.96 1.05 1.14 1.25 1.36 1.47 1.60 22 0.10 0.16 0.23 0.31 0.38 0.47 0.55 0.62 0.69 0.76 0.83 0.91 0.99 1.08 1.17 1.27 1.37 1.49 1.61 23 0.09 0.16 0.22 0.29 0.36 0.44 0.53 0.59 0.66 0.73 0.80 0.87 0.94 1.02 1.11 1.20 1.29 1.39 1.50 1.62 24 0.09 0.15 0.21 0.28 0.35 0.42 0.50 0.57 0.63 0.70 0.76 0.83 0.90 0.97 1.05 1.13 1.22 1.31 1.41 1.51 1.63 25 0.08 0.14 0.20 0.26 0.33 0.40 0.47 0.55 0.61 0.67 0.73 0.79 0.86 0.93 1.00 1.07 1.15 1.24 1.33 1.42 1.53 1.64 26 0.08 0.14 0.19 0.25 0.31 0.38 0.45 0.52 0.58 0.64 0.70 0.76 0.82 0.89 0.95 1.02 1.10 1.18 1.26 1.35 1.44 1.54 1.64 27 0.08 0.13 0.18 0.24 0.30 0.36 0.43 0.50 0.56 0.62 0.67 0.73 0.79 0.85 0.91 0.98 1.05 1.12 1.20 1.28 1.36 1.45 1.55 1.65 28 0.07 0.12 0.18 0.23 0.29 0.35 0.41 0.47 0.54 0.60 0.65 0.71 0.76 0.82 0.88 0.94 1.00 1.07 1.14 1.22 1.29 1.38 1.46 1.56 1.66 MAX618 www.maximintegrated.com 28V Internal Switch, Step-Up DC-DC Converter Maxim Integrated 12 www.maximintegrated.com 117 6 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 132 107 96 80 7 5 151 118 6 4 5 173 128 100 4 3 VIN 104 97 90 80 65 8 94 89 83 77 68 54 9 76 86 79 72 68 64 59 51 40 11 82 77 72 67 59 46 10 66 73 68 63 61 58 55 51 46 39 31 13 70 67 64 61 57 52 45 35 12 Table 4. Minimum COUT for Stability (F) 64 62 59 57 55 52 50 46 41 35 28 14 60 58 56 54 52 50 48 45 42 37 32 25 15 56 55 53 51 50 48 46 44 42 38 34 29 23 16 VOUT 53 52 50 49 47 46 44 42 41 39 35 31 27 21 17 50 49 48 47 45 44 43 41 39 38 35 32 29 24 19 18 48 47 46 44 43 42 41 40 38 37 35 33 30 26 23 18 19 46 45 44 43 42 40 39 38 37 36 34 33 30 28 25 21 17 20 43 43 42 41 40 39 38 37 36 35 34 32 31 28 26 23 20 15 21 42 41 40 39 38 37 37 36 35 34 33 32 30 29 26 24 21 18 15 22 40 39 38 38 37 36 35 35 34 33 32 31 30 29 27 25 23 20 17 14 23 38 38 37 36 36 35 34 33 33 32 31 30 29 28 27 25 23 21 19 16 13 24 37 36 36 35 34 34 33 32 32 31 30 29 29 28 27 25 24 22 20 18 15 12 25 35 35 34 34 33 33 32 31 31 30 29 29 28 27 26 25 24 22 21 19 17 15 12 26 34 34 33 33 32 32 31 30 30 29 29 28 27 27 26 25 24 23 21 20 18 16 14 11 27 33 33 32 32 31 31 30 29 29 28 28 27 27 26 25 25 24 23 21 20 19 17 15 13 10 28 MAX618 28V Internal Switch, Step-Up DC-DC Converter Maxim Integrated 13 www.maximintegrated.com 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 VIN 40 4 42 46 5 43 45 54 6 44 45 51 64 7 45 45 49 58 73 8 46 45 48 54 66 83 9 12 13 14 15 16 VOUT 17 18 19 20 21 22 23 24 25 26 27 28 46 46 47 47 50 57 67 82 46 47 48 46 48 52 58 68 81 48 47 46 48 51 56 63 74 88 49 47 47 48 50 54 60 68 80 96 49 47 47 47 49 52 57 64 74 86 103 49 47 47 47 49 51 55 61 68 79 92 49 48 47 47 48 50 54 58 64 73 85 99 50 48 47 47 48 50 52 56 61 68 78 90 50 48 47 47 48 49 52 55 59 65 73 83 95 50 48 47 47 48 49 51 54 57 62 69 77 88 50 48 47 47 48 49 50 53 56 60 65 72 82 93 50 49 48 47 48 48 50 52 55 58 63 69 77 86 98 50 49 48 47 48 48 49 51 53 57 61 66 72 81 91 51 49 48 47 48 48 49 51 53 55 59 63 69 76 85 95 51 49 48 48 48 48 49 50 52 54 57 61 66 72 80 89 99 51 49 48 48 48 48 49 50 51 53 56 59 64 69 75 84 93 51 49 48 48 48 48 48 49 51 53 55 58 62 66 72 79 88 97 104 109 103 108 113 119 124 101 107 113 119 125 132 139 146 105 112 119 127 134 142 150 159 167 176 111 120 128 137 147 156 166 176 187 197 209 220 100 109 119 130 141 152 164 176 188 201 214 228 242 257 272 287 46 47 49 54 62 75 91 105 118 130 143 157 172 187 203 219 236 253 271 290 309 329 349 370 391 11 45 47 52 60 74 94 10 Table 5. Minimum CCOMP for Stability (nF) MAX618 28V Internal Switch, Step-Up DC-DC Converter Maxim Integrated 14 MAX618 28V Internal Switch, Step-Up DC-DC Converter Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 0 6/09 Initial release 1 12/09 Updated part to lead-free, added soldering temperatures (reflow), and corrected error in equation 2 4/15 No /V ordering information; removed Automotive reference from Applications section DESCRIPTION -- 1, 2, 10 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated's website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. (c) 2015 Maxim Integrated Products, Inc. 15 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX618EEE+ MAX618EEE+T MAX618EEE MAX618EEE-T MAX618EEE/GG8-T