EVALUATION KIT AVAILABLE MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation General Description Benefits and Features The MAX17543 uses peak current-mode control. The device can be operated in the pulse-width modulation (PWM), pulse-frequency modulation (PFM), or discontinuous conduction mode (DCM) control schemes. Reduces Number of DC-DC Regulators to Stock * Wide 4.5V to 42V Input * Adjustable 0.9V to 0.9 x VIN Output * 100kHz to 2.2MHz Adjustable Switching Frequency with External Synchronization The MAX17543 high-efficiency, high-voltage, synchronous step-down DC-DC converter with integrated MOSFETs operates over a 4.5V to 42V input. The converter can deliver up to 2.5A and generates output voltages from 0.9V up to 0.9 x VIN. The feedback (FB) voltage is accurate to within 1.1% over -40C to +125C. Reduces External Components and Total Cost * No Schottky--Synchronous Operation * Internal Compensation for Any Output Voltage * Built-In Soft-Start * All-Ceramic Capacitors, Compact Layout The device is available in a 20-pin (4mm x 4mm) TQFN package. Simulation models are available. Reduces Power Dissipation * Peak Efficiency >90% * PFM/DCM Enables Enhanced Light-Load Efficiency * 2.8A Shutdown Current Applications Industrial Power Supplies Operates Reliably in Adverse Industrial Environments * Peak Current-Limit Protection * Built-In Output Voltage Monitoring with RESET * Programmable EN/UVLO Threshold * Monotonic Startup into Prebiased Load * Overtemperature Protection * High Industrial -40C to +125C Ambient Operating Temperature Range/-40C to +150C Junction Temperature Range Distributed Supply Regulation High-Voltage Single-Board Systems Base Station Power Supply General-Purpose Point-of-Load Ordering Information appears at end of data sheet. Typical Application Circuit--5V, 500kHz Switching Frequency VIN (6.5V TO 42V) C1 2.2F RT EN/UVLO VIN VIN VIN BST SYNC LX MAX17543 MODE C2 2.2F C4 22F LX VCC VOUT 5V, 2.5A L1 10H LX R3 178k FB SGND R4 39k RESET CF SS C3 5.6nF 19-7054; Rev 1; 7/16 C5 0.1F PGND PGND PGND fSW = 500kHz MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Absolute Maximum Ratings VIN to PGND..........................................................-0.3V to +48V EN/UVLO to SGND................................................-0.3V to +48V LX to PGND................................................-0.3V to (VIN + 0.3V) BST to PGND.........................................................-0.3V to +53V BST to LX..............................................................-0.3V to +6.5V BST to VCC............................................................-0.3V to +48V CF, RESET, SS, MODE, SYNC, RT to SGND......................................................-0.3V to +6.5V FB to SGND..........................................................-0.3V to +1.5V VCC to SGND........................................................-0.3V to +6.5V SGND to PGND.....................................................-0.3V to +0.3V LX Total RMS Current............................................................4A Output Short-Circuit Duration.....................................Continuous Continuous Power Dissipation (TA = +70C) (multilayer board) TQFN (derate 30.3mW/C above TA = +70C).......2424.2mW Junction Temperature.......................................................+150C Storage Temperature Range............................. -65C to +160C Lead Temperature (soldering, 10s).................................. +300C Soldering Temperature (reflow)........................................+260C 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. Junction temperature greater than +125C degrades operating lifetimes. Package Thermal Characteristics (Note 1) TQFN Junction-to-Ambient Thermal Resistance (JA)...........33C/W Junction-to-Case Thermal Resistance (JC)..................2C/W Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial. Electrical Characteristics (VIN = VEN/UVLO = 24V, RRT = 40.2k (500kHz), CVCC = 2.2F, VPGND = VSGND = VMODE = VSYNC = 0V, LX = SS = RESET = open, VBST to VLX = 5V, VFB = 1V, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to SGND, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 42 V INPUT SUPPLY (VIN) Input Voltage Range Input Shutdown Current VIN IIN-SH VEN/UVLO = 0V (shutdown mode) 2.8 VFB = 1V, MODE = RT = open 118 VFB = 1V, MODE = open 162 IQ-DCM DCM mode, VLX = 0.1V 1.16 IQ_PWM Normal switching mode, fSW = 500kHz, VFB = 0.8V 9.5 IQ_PFM Input Quiescent Current 4.5 4.5 A 1.8 mA ENABLE/UVLO (EN/UVLO) EN/UVLO Threshold EN/UVLO Input Leakage Current VENR VEN/UVLO rising 1.19 1.215 1.26 VENF VEN/UVLO falling 1.068 1.09 1.131 -50 0 +50 nA 4.75 5 5.25 V 26.5 54 100 mA IEN VEN/UVLO = 0V, TA = +25C V LDO VCC Output Voltage Range VCC Current Limit VCC Dropout VCC UVLO www.maximintegrated.com VCC IVCC-MAX VCC-DO 6V < VIN < 42V, IVCC = 1mA 1mA IVCC 25mA VCC = 4.3V, VIN = 6V VIN = 4.5V, IVCC = 20mA 4.2 VCC_UVR VCC rising 4.05 4.2 4.3 V VCC_UVF VCC falling 3.65 3.8 3.9 V Maxim Integrated 2 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Electrical Characteristics (continued) (VIN = VEN/UVLO = 24V, RRT = 40.2k (500kHz), CVCC = 2.2F, VPGND = VSGND = VMODE = VSYNC = 0V, LX = SS = RESET = open, VBST to VLX = 5V, VFB = 1V, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to SGND, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS POWER MOSFET AND BST DRIVER High-Side nMOS On-Resistance RDS-ONH ILX = 0.3A 165 325 m Low-Side nMOS On-Resistance RDS-ONL ILX = 0.3A 80 150 m LX Leakage Current ILX_LKG VLX = VIN - 1V, VLX = VPGND + 1V, TA = +25C -2 +2 A VSS = 0.5V 4.7 5 5.3 A MODE = SGND or MODE = VCC 0.89 0.9 0.91 MODE = OPEN 0.89 0.915 0.936 0 < VFB < 1V, TA = +25C -50 SOFT-START (SS) Charging Current ISS FEEDBACK (FB) FB Regulation Voltage VFB_REG FB Input Bias Current IFB +50 V nA MODE MODE Threshold VM-DCM MODE = VCC (DCM mode) VM-PFM MODE = open (PFM mode) VM-PWM MODE = GND (PWM mode) VCC 1.6 V VCC / 2 1.4 CURRENT LIMIT Peak Current-Limit Threshold Runaway Current-Limit Threshold IPEAK-LIMIT 3.2 3.7 4.3 A IRUNAWAY-LIMIT 3.7 4.3 5 A 0 +0.16 Valley Current-Limit Threshold ISINK-LIMIT PFM Current-Limit Threshold IPFM MODE = open/VCC -0.16 MODE = GND -1.8 MODE = open 0.6 0.75 0.9 RRT = 210k 90 100 110 RRT = 102k 180 200 220 RRT = 40.2k 475 500 525 RRT = 8.06k 1950 2200 2450 RRT = open 460 500 540 fSW set by RRT 1.1 x fSW A A RT AND SYNC Switching Frequency fSW SYNC Frequency Capture Range SYNC Pulse Width SYNC Threshold FB Undervoltage Trip Level to Cause Hiccup www.maximintegrated.com 1.4 x fSW 50 VIH 0.8 0.56 kHz ns 2.1 VIL VFB-HICF kHz 0.58 0.65 V V Maxim Integrated 3 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Electrical Characteristics (continued) (VIN = VEN/UVLO = 24V, RRT = 40.2k (500kHz), CVCC = 2.2F, VPGND = VSGND = VMODE = VSYNC = 0V, LX = SS = RESET = open, VBST to VLX = 5V, VFB = 1V, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to SGND, unless otherwise noted.) (Note 2) PARAMETER SYMBOL Hiccup Timeout CONDITIONS MIN (Note 3) Minimum On-Time tON-MIN Minimum Off-Time tOFF-MIN 140 RESET Output Level Low IRESET = 10mA RESET Output Leakage Current TA = TJ = +25C, VRESET = 5.5V -0.1 VFB falling 90.5 VFB-OKF VFB-OKR VFB rising RESET Deassertion Delay After FB Reaches 95% Regulation 93.8 92 95 UNITS Cycles 135 ns 160 ns 5 RESET FB Threshold for RESET Deassertion MAX 32,768 LX Dead Time FB Threshold for RESET Assertion TYP ns 0.4 V +0.1 A 94.6 %VFB- 97.8 %VFB- REG REG 1024 Cycles 165 C 10 C THERMAL SHUTDOWN Thermal Shutdown Threshold Temperature rising Thermal Shutdown Hysteresis Note 2: All limits are 100% tested at +25C. Limits over temperature are guaranteed by design. Note 3: See the Overcurrent Protection/Hiccup Mode section for more details. www.maximintegrated.com Maxim Integrated 4 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Typical Operating Characteristics (VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = CVCC = 2.2F, CBST = 0.1F, CSS = 5600pF, RT = MODE = open, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) 100 90 90 80 80 VIN = 36V VIN = 24V 70 EFFICIENCY (%) VIN =12V 60 50 70 VIN = 12V 60 0 500 1000 1500 2000 40 2500 3.3V OUTPUT, PFM MODE, FIGURE CIRCUIT, FIGURE4b 4 CIRCUIT, EFFICIENCY VS. LOAD CURRENTTOC04 90 90 80 80 70 60 VIN = 24V 50 VIN = 36V 0 500 MODE = OPEN 1 1000 1500 2000 2500 100 VIN = 36V 90 VIN = 24V VIN = 12V VIN = 24V 80 70 VIN = 12V 60 50 40 MODE = VCC 1 10 100 30 1000 MODE = VCC 1 10 100 1000 LOAD CURRENT (mA) LOAD CURRENT (mA) LOAD CURRENT (mA) 5V OUTPUT, PWM MODE, FIGURE CIRCUIT, FIGURE 4a 3 CIRCUIT, 3.3V OUTPUT, PWM MODE, FIGURE 4b CIRCUIT, 5V OUTPUT, PFM MODE, FIGURE CIRCUIT, FIGURE 4a 3 CIRCUIT, TOC07 LOAD AND LINE REGULATION 3.35 TOC08 3.34 5.4 3.33 5.3 3.32 5.2 OUTPUT VOLTAGE (V) VIN = 36V 5.02 5.01 5 4.99 VIN = 12V VIN = 24V 4.97 3.31 3.3 3.29 3.28 3.27 4.96 3.26 4.95 3.25 500 1000 1500 LOAD CURRENT (mA) www.maximintegrated.com 2000 2500 VIN = 12V VIN = 24V VIN = 36V LOAD AND LINE REGULATION 5.5 5.03 0 1000 2500 100 3.3V OUTPUT, DCM MODE, FIGURE CIRCUIT, FIGURE 4b 4 CIRCUIT, EFFICIENCY VS. LOAD CURRENT 5.04 4.98 10 5V OUTPUT, DCM MODE, FIGURE CIRCUIT, FIGURE4a 3 CIRCUIT, EFFICIENCY VS. LOAD CURRENT VIN = 36V 60 MODE = OPEN 1 LOAD CURRENT (mA) 70 30 1000 2500 100 LOAD AND LINE REGULATION 5.05 OUTPUT VOLTAGE (V) 10 VIN = 12V LOAD CURRENT (mA) 40 40 VIN = 36V VIN = 24V 60 30 50 VIN = 12V 70 40 MODE = SGND 100 EFFICIENCY (%) EFFICIENCY (%) 100 80 50 LOAD CURRENT (mA) 30 VIN = 36V VIN = 24V EFFICIENCY (%) 40 90 50 MODE = SGND 5V OUTPUT, PFM MODE, FIGURE 4a CIRCUIT, EFFICIENCY VS. LOAD CURRENTTOC03 100 OUTPUT VOLTAGE (V) EFFICIENCY (%) 100 3.3V OUTPUT, PWM MODE, FIGURE 4b CIRCUIT, EFFICIENCY VS. LOAD CURRENTTOC02 EFFICIENCY (%) 5V OUTPUT, PWM MODE, FIGURE 4a CIRCUIT, EFFICIENCY VS. LOAD CURRENTTOC01 TOC09 VIN = 12V VIN = 24V 5.1 5 4.9 VIN = 36V 4.8 4.7 4.6 0 500 1000 1500 LOAD CURRENT (mA) 2000 2500 4.5 0 500 1000 1500 2000 2500 LOAD CURRENT (mA) Maxim Integrated 5 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Typical Operating Characteristics (continued) (VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = CVCC = 2.2F, CBST = 0.1F, CSS = 5600pF, RT = MODE = open, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) 3.3V OUTPUT, PFM MODE, FIGURE CIRCUIT, FIGURE 4b 4 CIRCUIT, LOAD AND LINE REGULATION 3.6 SWITCHING FREQUENCY vs. RT RESISTANCE TOC10 TOC11 2400 2200 2000 VIN = 12V 1800 3.4 SWITCHING FREQUENCY (kHz) OUTPUT VOLTAGE (V) 3.5 3.3 3.2 VIN = 24V 3.1 3 VIN = 36V 0 500 1000 1500 2000 1600 1400 1200 1000 800 600 400 200 0 2500 0 20 40 60 80 100 120 140 160 180 200 RRT (k) LOAD CURRENT (mA) SOFT-START/SHUTDOWN FROM EN/UVLO 5V OUTPUT, 2.5A LOAD CURRENT, FIGURE 4a CIRCUIT SOFT-START/SHUTDOWN FROM EN/UVLO 3.3V OUTPUT, 2.5A LOAD CURRENT, FIGURE 4b CIRCUIT MAX17543 toc12 MAX17543 toc13 SOFT-START/SHUTDOWN FROM EN/UVLO 5V OUTPUT, PFM MODE, 5mA LOAD CURRENT, FIGURE 4a CIRCUIT MAX17543 toc14 MODE = OPEN VEN/UVLO 2V/div VEN/UVLO 2V/div VEN/UVLO 2V/div VOUT 2V/div VOUT 2V/div IOUT 1A/div IOUT 1A/div VRESET 5V/div VRESET 5V/div VOUT 1V/div VRESET 5V/div 2ms/div 1ms/div 1ms/div SOFT-START/SHUTDOWN FROM EN/UVLO, 3.3V OUTPUT, PFM MODE, 5mA LOAD CURRENT, FIGURE 4b CIRCUIT 5V OUTPUT, PWM MODE SOFT-START WITH 2.5V PREBIAS, FIGURE 4a CIRCUIT 3.3V OUTPUT, PFM MODE SOFT-START WITH 2.5V PREBIAS, FIGURE 4b CIRCUIT MODE = OPEN MODE = SGND MODE = OPEN MAX17543 toc16 MAX17543 toc15 VEN/UVLO 2V/div VEN/UVLO 2V/div MAX17543 toc17 VEN/UVLO 2V/div VOUT 1V/div VOUT 2V/div VOUT 1V/div VRESET 5V/div VRESET 5V/div 2ms/div www.maximintegrated.com VRESET 5V/div 1ms/div 1ms/div Maxim Integrated 6 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Typical Operating Characteristics (continued) (VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = CVCC = 2.2F, CBST = 0.1F, CSS = 5600pF, RT = MODE = open, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) 5V OUTPUT, 2.5A LOAD CURRENT STEADY-STATE SWITCHING WAVEFORMS, FIGURE 4a CIRCUIT 5V OUTPUT, PWM MODE, NO LOAD STEADY-STATE SWITCHING WAVEFORMS, FIGURE 4a CIRCUIT MAX17543 toc18 MAX17543 toc19 VOUT (AC) 50mV/div VOUT (AC) 50mV/div VLX 10V/div VLX 10V/div MODE = SGND ILX 500mA/div ILX 1A/div 1s/div 1s/div 5V OUTPUT, PFM MODE, 25mA LOAD STEADY-STATE SWITCHING WAVEFORMS, FIGURE 4a CIRCUIT 5V OUTPUT, DCM MODE, 25mA LOAD STEADY-STATE SWITCHING WAVEFORMS, FIGURE 4a CIRCUIT MAX17543 toc20 MAX17543 toc21 VOUT (AC) 100mV/div VOUT (AC) 20mV/div VLX 10V/div VLX 10V/div ILX 500mA/div ILX 200mA/div MODE = OPEN MODE = VCC 10s/div 1s/div 5V OUTPUT, PWM MODE (LOAD CURRENT STEPPED FROM 1A TO 2A), FIGURE 4a CIRCUIT 3.3V OUTPUT, PWM MODE (LOAD CURRENT STEPPED FROM 1A TO 2A), FIGURE 4b CIRCUIT MODE = SGND MODE = SGND MAX17543 toc22 VOUT (AC) 100mV/div VOUT (AC) 50mV/div IOUT 1A/div IOUT 1A/div 40s/div www.maximintegrated.com MAX17543 toc23 40s/div Maxim Integrated 7 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Typical Operating Characteristics (continued) (VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = CVCC = 2.2F, CBST = 0.1F, CSS = 5600pF, RT = MODE = open, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) 5V OUTPUT, PWM MODE (LOAD CURRENT STEPPED FROM NO-LOAD TO 1A), FIGURE 4a CIRCUIT 3.3V OUTPUT, PWM MODE (LOAD CURRENT STEPPED FROM NO-LOAD TO 1A), FIGURE 4b CIRCUIT MODE = SGND MODE = SGND MAX17543 toc24 MAX17543 toc25 VOUT (AC) 100mV/div VOUT (AC) 50mV/div IOUT 1A/div IOUT 1A/div 40s/div 40s/div 5V OUTPUT, PFM MODE (LOAD CURRENT STEPPED FROM 5mA TO 1A), FIGURE 4a CIRCUIT 3.3V OUTPUT, PFM MODE (LOAD CURRENT STEPPED FROM 5mA TO 1A), FIGURE 4b CIRCUIT MODE = OPEN MODE = OPEN MAX17543 toc26 MAX17543 toc27 VOUT (AC) 100mV/div VOUT (AC) 50mV/div IOUT 500mA/div IOUT 500mA/div 2ms/div 2ms/div 5V OUTPUT, DCM MODE (LOAD CURRENT STEPPED FROM 50mA TO 1A), FIGURE 4a CIRCUIT 3.3V OUTPUT, DCM MODE (LOAD CURRENT STEPPED FROM 50mA TO 1A), FIGURE 4b CIRCUIT MODE = VCC MODE = VCC MAX17543 toc28 MAX17543 toc29 VOUT (AC) 100mV/div VOUT (AC) 100mV/div IOUT 500mA/div IOUT 500mA/div 200s/div www.maximintegrated.com 200s/div Maxim Integrated 8 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Typical Operating Characteristics (continued) (VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = CVCC = 2.2F, CBST = 0.1F, CSS = 5600pF, RT = MODE = open, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) 5V OUTPUT, APPLICATION OF EXTERNAL CLOCK AT 700kHz, FIGURE 4a CIRCUIT 5V OUTPUT, OVERLOAD PROTECTION, FIGURE 4a CIRCUIT MAX17543 toc30 MAX17543 toc31 VLX 10V/div IOUT 1A/div VSYNC 2V/div 20ms/div 2s/div 5V OUTPUT, 2.5A LOAD CURRENT BODE PLOT, FIGURE 4a CIRCUIT 5V OUTPUT, 2.5A LOAD CURRENT BODE PLOT, FIGURE 4b CIRCUIT MAX17543 toc32 MAX17543 toc33 60 80 50 30 60 40 80 20 40 30 60 20 20 40 GAIN 10 0 0 -10 -20 CROSSOVER FREQUENCY = 58.2kHz -30 PHASE MARGIN = 63.4 -40 -50 2 1k 4 6 81 2 -20 4 6 81 2 100k 10k GAIN (dB) PHASE PHASE () 100 50 GAIN (dB) MODE = SGND 120 100 PHASE 40 GAIN 10 20 0 -40 -10 CROSSOVER FREQUENCY = 62.5kHz -60 -20 PHASE MARGIN = 61.2 -80 -30 -100 -40 2 1k FREQUENCY (Hz) 4 6 81 2 0 PHASE () VOUT 500mV/div -20 -40 4 6 81 10k 100k 2 -60 -80 FREQUENCY (Hz) MAX17543, 5V OUTPUT, 2.5A LOAD CURRENT, FIGURE 4a CIRCUIT, CONDUCTED EMI CURVE CONDUCTED EMI (dBV) 60 QUASI-PEAK LIMIT 50 AVERAGE LIMIT MAX17543 toc34 70 40 30 20 PEAK EMISSIONS 10 AVERAGE EMISSIONS 0.15 1 10 FREQUENCY (MHz) 30 Measured on the MAX17543EVKITB with input filter - CIN = 4.7F, LIN = 10H, the input capacitor for the MAX17543: 4.7F. www.maximintegrated.com Maxim Integrated 9 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation PGND SGND VCC MODE TOP VIEW PGND Pin Configuration 15 14 13 12 11 PGND 16 10 RT LX 17 9 FB 8 CF 7 SS 6 SYNC MAX17543 LX 18 LX 19 2 3 4 5 EN/UVLO RESET VIN 1 VIN + VIN BST 20 TQFN 4mm x 4mm * EXPOSED PAD (CONNECT TO GROUND). Pin Description PIN NAME 1-3 VIN Power Supply Input. 4.5V to 42V input supply range. Connect the VIN pins together. Decouple to PGND with a 2.2F capacitor; place the capacitor close to the VIN and PGND pins. Refer to the MAX17543 EV kit data sheet for a layout example. 4 EN/UVLO Enable/Undervoltage Lockout. Drive EN/UVLO high to enable the output voltage. Connect to the center of the resistor-divider between VIN and SGND to set the input voltage at which the device turns on. Pull up to VIN for always-on operation. 5 RESET Open-Drain RESET Output. The RESET output is driven low if FB drops below 92% of its set value. RESET goes high 1024 clock cycles after FB rises above 95% of its set value. 6 SYNC 7 SS Soft-Start Input. Connect a capacitor from SS to SGND to set the soft-start time. 8 CF At switching frequencies lower than 500kHz, connect a capacitor from CF to FB. Leave CF open if switching frequency is equal to, or greater than, 500kHz. See the Loop Compensation section for more details. 9 FB Feedback Input. Connect FB to the center tap of an external resistor-divider from the output to GND to set the output voltage. See the Adjusting Output Voltage section for more details. 10 RT Connect a resistor from RT to SGND to set the regulator's switching frequency. Leave RT open for the default 500kHz frequency. See the Setting the Switching Frequency (RT) section for more details. MODE MODE pin configures the device to operate either in PWM, PFM, or DCM modes of operation. Leave MODE unconnected for PFM operation (pulse-skipping at light loads). Connect MODE to SGND for constant-frequency PWM operation at all loads. Connect MODE to VCC for DCM operation. See the MODE Setting section for more details. 11 www.maximintegrated.com FUNCTION The device can be synchronized to an external clock using this pin. See the External Frequency Synchronization section for more details. Maxim Integrated 10 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Pin Description (continued) PIN NAME 12 VCC FUNCTION 13 SGND Analog Ground 14-16 PGND Power Ground. Connect the PGND pins externally to the power ground plane. Connect the SGND and PGND pins together at the ground return path of the VCC bypass capacitor. Refer to the MAX17543 EV kit data sheet for a layout example. 17-19 LX 20 BST -- EP 5V LDO Output. Bypass VCC with 2.2F ceramic capacitance to SGND. Switching Node. Connect LX pins to the switching-side of the inductor. Refer to the MAX17543 EV kit data sheet for a layout example. Boost Flying Capacitor. Connect a 0.1F ceramic capacitor between BST and LX. Exposed Pad. Connect to the SGND pin. Connect to a large copper plane below the IC to improve heat dissipation capability. Add thermal vias below the exposed pad. Refer to the MAX17543 EV kit data sheet for a layout example. Block Diagram VCC 5V BST MAX17543 LDO VIN SGND CURRENT-SENSE LOGIC EN/UVLO HICCUP 1.215V PWM/ PFM/ HICCUP LOGIC AND DRIVERS LX RT PGND OSCILLATOR SYNC CF FB VCC SWITCHOVER LOGIC SS VBG = 0.9V SLOPE COMPENSATION 5A FB HICCUP www.maximintegrated.com MODE SELECTION LOGIC ERROR AMPLIFIER/ LOOP COMPENSATION EN/UVLO MODE RESET RESET LOGIC Maxim Integrated 11 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Detailed Description PFM Mode Operation The device features a peak-current-mode-control architecture. An internal transconductance error amplifier produces an integrated error voltage at an internal node, which sets the duty cycle using a PWM comparator, a highside current-sense amplifier, and a slope-compensation generator. At each rising-edge of the clock, the highside MOSFET turns on and remains on until either the appropriate or maximum duty cycle is reached, or the peak current limit is detected. During the high-side MOSFET's on-time, the inductor current ramps up. During the second-half of the switching cycle, the high-side MOSFET turns off and the low-side MOSFET turns on. The inductor releases the stored energy as its current ramps down and provides current to the output. DCM Mode Operation The MAX17543 high-efficiency, high-voltage, synchro nously-rectified step-down converter with dual integrated MOSFETs operates over a 4.5V to 42V input. It delivers up to 2.5A and 0.9V to 90%VIN output voltage. Built-in compensation across the output voltage range eliminates the need for external components. The feedback (FB) regulation accuracy over -40C to +125C is 1.1%. The PFM mode of operation disables negative inductor current and also skips pulses at light loads for high efficiency. In PFM mode, the inductor current is forced to a fixed peak of 750mA every clock cycle until the output rises to 102.3% of the nominal voltage. Once the output reaches 102.3% of the nominal voltage, both the highside and low-side FETs are turned off and the device enters hibernation mode until the load discharges the output to 101.1% of the nominal voltage. Most of the internal blocks are turned off in hibernation mode to save quiescent current. After the output falls below 101.1% of the nominal voltage, the device comes out of hibernation mode, turns on all internal blocks, and again commences the process of delivering pulses of energy to the output until it reaches 102.3% of the nominal output voltage. The advantage of PFM mode is higher efficiency at light loads due to lower quiescent current drawn from supply. The disadvantage is that the output voltage ripple is higher than in the PWM or DCM modes of operation, and the switching frequency is not constant at light loads. The device features a MODE pin that can be used to operate the device in PWM, PFM, or DCM control schemes. The device integrates adjustable-input undervoltage lockout, adjustable soft-start, open RESET, and external frequency-synchronization features. The DCM mode of operation features constant-frequency operation down to lighter loads than PFM mode by disabling negative inductor current at light loads instead of skipping pulses. DCM operation offers efficiency performance that lies between the PWM and PFM modes. Mode Selection (MODE) Linear Regulator (VCC) The logic state of the MODE pin is latched when VCC and EN/UVLO voltages exceed the respective UVLO rising thresholds and all internal voltages are ready to allow LX switching. If the MODE pin is open at power-up, the device operates in PFM mode at light loads. If the MODE pin is grounded at power-up, the device operates in constant-frequency PWM mode at all loads. Finally, if the MODE pin is connected to VCC at power-up, the device operates in constant-frequency DCM mode at light loads. State changes on the MODE pin are ignored during normal operation. PWM Mode Operation In PWM mode, the inductor current is allowed to go negative. PWM operation provides constant frequency operation at all loads, and is useful in applications sensitive to switching frequency. However, the PWM mode of operation gives lower efficiency at light loads when compared to PFM and DCM modes of operation. www.maximintegrated.com An internal linear regulator (VCC) provides a 5V nominal supply to power the internal blocks and the low-side MOSFET driver. The output of the linear regulator (VCC) should be bypassed with a 2.2F ceramic capacitor to SGND. The device employs an undervoltage lockout circuit that disables the internal linear regulator when VCC falls below 3.8V (typ). Setting the Switching Frequency (RT) The switching frequency of the device can be programmed from 100kHz to 2.2MHz by using a resistor connected from the RT pin to SGND. The switching frequency (fSW) is related to the resistor connected at the RT pin (RRT) by the following equation: R RT 21x 10 3 - 1.7 f SW where RRT is in k and fSW is in kHz. Leaving the RT pin open causes the device to operate at the default switching frequency of 500kHz. See Table 1 for RT resistor values for a few common switching frequencies. To operate the MAX17543 at switching frequencies lower than 200kHz, an Maxim Integrated 12 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Table 1. Switching Frequency vs. RT Resistor SWITCHING FREQUENCY (kHz) RT RESISTOR (k) 500 Open 100 210 200 102 400 49.9 1000 19.1 2200 8.06 R-C network has to be connected in parallel to the resistor connected from RT to SGND, as shown in Figure 1. The values of the components R8 and C13 are 90.9k and 220pF, respectively. R5 R8 C13 Figure 1. Setting the Switching Frequency Operating Input Voltage Range The minimum and maximum operating input voltages for a given output voltage should be calculated as follows: VIN(MIN) = VOUT + (I OUT(MAX) x (R DCR + 0.15)) 1- (f SW(MAX) x t OFF(MAX) ) + (I OUT(MAX) x 0.175) VIN(MAX) = VOUT f SW(MAX) x t ON(MIN) ) where VOUT is the steady-state output voltage, IOUT (MAX) is the maximum load current, RDCR is the DC resistance of the inductor, fSW(MAX) is the maximum switching frequency, tOFF-MAX is the worst-case minimum switch off-time (160ns), and tON-MIN is the worst-case minimum switch on-time (135ns). External Frequency Synchronization (SYNC) The internal oscillator of the device can be synchronized to an external clock signal on the SYNC pin. The external synchronization clock frequency must be between www.maximintegrated.com 1.1 x fSW and 1.4 x fSW, where fSW is the frequency programmed by the RT resistor. The minimum external clock pulse-width high should be greater than 50ns. See the RT AND SYNC section of the Electrical Characteristics table for details. Overcurrent Protection/Hiccup Mode The MAX17543 is provided with a robust overcurrent protection scheme that protects the device under overload and output short-circuit conditions. A cycle-by-cycle peak current limit turns off the high-side MOSFET whenever the high-side switch current exceeds an internal limit of 3.7A (typ). A runaway current limit on the high-side switch current at 4.3A (typ) protects the device under high input voltage, short-circuit conditions when there is insufficient output voltage available to restore the inductor current that was built up during the ON period of the step-down converter. One occurrence of runaway current limit triggers a hiccup mode. In addition, if, due to a fault condition, feedback voltage drops to 0.58V (typ) any time after soft-start is complete, hiccup mode is triggered. In hiccup mode, the converter is protected by suspending switching for a hiccup timeout period of 32,768 clock cycles. Once the hiccup timeout period expires, softstart is attempted again. Note that when soft-start is attempted under an overload condition, if the feedback voltage does not exceed 0.58V, the device switches at half the programmed switching frequency. Hiccup mode of operation ensures low power dissipation under output short-circuit conditions. RESET Output The device includes a RESET comparator to monitor the output voltage. The open-drain RESET output requires an external pullup resistor. RESET goes high (high impedance) 1024 switching cycles after the regulator output increases above 95% of the designed nominal regulated voltage. RESET goes low when the regulator output voltage drops to below 92% of the nominal regulated voltage. RESET also goes low during thermal shutdown. Prebiased Output When the device starts into a prebiased output, both the high-side and low-side switches are turned off so that the converter does not sink current from the output. Highside and low-side switches do not start switching until the PWM comparator commands the first PWM pulse, at which point switching commences. The output voltage is then smoothly ramped up to the target value in alignment with the internal reference. Maxim Integrated 13 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Thermal-Shutdown Protection Thermal-shutdown protection limits total power dissipation in the device. When the junction temperature of the device exceeds +165C, an on-chip thermal sensor shuts down the device, allowing it to cool. The thermal sensor turns the device on again after the junction temperature cools by 10C. Soft-start resets during thermal shutdown. Carefully evaluate the total power dissipation (see the Power Dissipation section) to avoid unwanted triggering of the thermal shutdown in normal operation. Applications Information Input Capacitor Selection The input filter capacitor reduces peak currents drawn from the power source and reduces noise and voltage ripple on the input caused by the circuit's switching. The input capacitor RMS current requirement (IRMS) is defined by the following equation: = IRMS I OUT(MAX) x VOUT x (VIN - VOUT ) IN where, IOUT(MAX) is the maximum load current. IRMS has a maximum value when the input voltage equals twice the output voltage (VIN = 2 x VOUT), so IRMS(MAX) = IOUT(MAX)/2. Choose an input capacitor that exhibits less than +10C temperature rise at the RMS input current for optimal long-term reliability. Use low-ESR ceramic capacitors with high-ripple-current capability at the input. X7R capacitors are recommended in industrial applications for their temperature stability. Calculate the input capacitance using the following equation: C IN = I OUT(MAX) x D x (1- D) x f SW x VIN where D = VOUT/VIN is the duty ratio of the controller, fSW is the switching frequency, VIN is the allowable input voltage ripple, and is the efficiency. In applications where the source is located some distance from the device input, an electrolytic capacitor should be added in parallel to the ceramic capacitor to provide necessary damping for potential oscillations caused by the inductance of the longer input power path and input ceramic capacitor. saturation current (ISAT), and DC resistance (RDCR). The switching frequency and output voltage determine the inductor value as follows: L= VOUT f SW where VOUT, and fSW are nominal values. Select a low-loss inductor closest to the calculated value with acceptable dimensions and having the lowest possible DC resistance. The saturation current rating (ISAT) of the inductor must be high enough to ensure that saturation can occur only above the peak current-limit value of 3.7A. Output Capacitor Selection X7R ceramic output capacitors are preferred due to their stability over temperature in industrial applications. The output capacitors are usually sized to support a step load of 50% of the maximum output current in the application, such that output voltage deviation is contained to 3% of nominal output voltage. The minimum required output capacitance can be calculated as follows: 5.5 C OUT = (f C x VOUT ) where COUT is in Farad and fC is the target closed-loop crossover frequency in Hz. Select fC to be 1/9th of fSW if the switching frequency is less than or equal to 500kHz. If the switching frequency is more than 500kHz, select fC to be 55kHz. Derating of ceramic capacitors with DC-voltage must be considered while selecting the output capacitor. Derating curves are available from all major ceramic capacitor vendors. Soft-Start Capacitor Selection The device implements adjustable soft-start operation to reduce inrush current. A capacitor connected from the SS pin to SGND programs the soft-start time. The selected output capacitance (CSEL) and the output voltage (VOUT) determine the minimum required soft-start capacitor as follows: C SS 28 x 10 -6 x C SEL x VOUT The soft-start time (tSS) is related to the capacitor connected at SS (CSS) by the following equation: t SS = C SS Inductor Selection 5.55 x 10 -6 For example, to program a 1ms soft-start time, a 5.6nF capacitor should be connected from the SS pin to SGND. www.maximintegrated.com Maxim Integrated 14 Three key inductor parameters must be specified for operation with the device: inductance value (L), inductor MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation VIN VOUT R1 R3 EN/UVLOV FB R2 R4 SGND SGND Figure 2. Setting the Input Undervoltage Lockout Figure 3. Setting the Output Voltage Table 2. C6 Capacitor Value at Various Switching Frequencies Adjusting Output Voltage SWITCHING FREQUENCY RANGE (kHz) C6 (pF) 200 to 300 2.2 300 to 400 1.2 400 to 500 0.75 Setting the Input Undervoltage-Lockout Level The device offers an adjustable input undervoltage-lockout level. Set the voltage at which the device turns on with a resistive voltage-divider connected from VIN to SGND. Connect the center node of the divider to EN/UVLO. Choose R1 to be 3.3M and then calculate R2 as follows: R1x 1.215 R2 = (VINU - 1.215) where VINU is the voltage at which the device is required to turn on. Ensure that VINU is higher than 0.8 x VOUT. If the EN/UVLO pin is driven from an external signal source, a series resistance of minimum 1k is recommended to be placed between the signal source output and the EN/UVLO pin, to reduce voltage ringing on the line. Loop Compensation The device is internally loop-compensated. However, if the switching frequency is less than 500kHz, connect a 0402 capacitor C6 between the CF pin and the FB pin. Use Table 2 to select the value of C6. If the switching frequency is less than 200kHz, connect an additional R-C network in parallel to the top resistor of the feedback divider (R3). See Figure 5 to calculate the values of the components R7, C12, and C6. Set the output voltage with a resistive voltage-divider connected from the positive terminal of the output capacitor (VOUT) to SGND (see Figure 3). Connect the center node of the divider to the FB pin. Use the following procedure to choose the resistive voltage-divider values: Calculate resistor R3 from the output to the FB pin as follows: 216 x 10 3 R3 = (fC x COUT) where R3 is in k, crossover frequency fC is in kHz, and the output capacitor (COUT) is in F. Choose fC to be 1/9th of the switching frequency (fSW) if the switching frequency is less than or equal to 500kHz. If the switching frequency is more than 500kHz, select fC to be 55kHz. Calculate resistor R4 from the FB pin to SGND as follows: R4 = R3 x 0.9 (VOUT - 0.9) Power Dissipation At a particular operating condition, the power losses that lead to temperature rise of the part are estimated as follows: ( 1 PLOSS = (POUT x ( - 1)) - I OUT 2 x R DCR ) P= OUT VOUT x I OUT where POUT is the total output power, is the efficiency of the converter, and RDCR is the DC resistances of the inductor. (See the Typical Operating Characteristics for more information on efficiency at typical operating conditions.) For a multilayer board, the thermal performance metrics for the package are given below: JA = 33C W JC =2C W www.maximintegrated.com Maxim Integrated 15 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation The junction temperature of the device can be estimated at any given maximum ambient temperature (TA_MAX) from the equation below: TJ_MAX = T A _MAX + ( JA x PLOSS ) If the application has a thermal management system that ensures that the exposed pad of the device is maintained at a given temperature (TEP_MAX) by using proper heatsinks, then the junction temperature of the device can be estimated at any given maximum ambient temperature from the equation below: T= J_MAX TEP_MAX + ( JC x PLOSS ) Junction temperature greater than +125C degrades operating lifetimes. PCB Layout Guidelines All connections carrying pulsed currents must be very short and as wide as possible. The inductance of these connections must be kept to an absolute minimum due to the high di/dt of the currents. Since inductance of a current carrying loop is proportional to the area enclosed by the loop, if the loop area is made very small, inductance is reduced. Additionally, small-current loop areas reduce radiated EMI. www.maximintegrated.com A ceramic input filter capacitor should be placed close to the VIN pins of the IC. This eliminates as much trace inductance effects as possible and gives the IC a cleaner voltage supply. A bypass capacitor for the VCC pin also should be placed close to the pin to reduce effects of trace impedance. When routing the circuitry around the IC, the analog small-signal ground and the power ground for switching currents must be kept separate. They should be connected together at a point where switching activity is at a minimum, typically the return terminal of the VCC bypass capacitor. This helps keep the analog ground quiet. The ground plane should be kept continuous/unbroken as far as possible. No trace carrying high switching current should be placed directly over any ground plane discontinuity. PCB layout also affects the thermal performance of the design. A number of thermal vias that connect to a large ground plane should be provided under the exposed pad of the part, for efficient heat dissipation. For a sample layout that ensures first pass success, refer to the MAX17543 evaluation kit layout available at www.maximintegrated.com. Maxim Integrated 16 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Typical Application Circuits VIN (6.5V TO 42V) C1 2.2F VIN EN/UVLO RT VIN VIN BST SYNC LX MAX17543 MODE C2 2.2F C5 0.1F VOUT 5V, 2.5A L1 10H C4 22F LX LX VCC R3 178k FB SGND R4 39k RESET CF SS PGND PGND PGND C3 5.6nF fSW = 500kHz Figure 4a - 5V Output, 500kHz Switching Frequency VIN (6.5V TO 42V) C1 2.2F VIN EN/UVLO RT C2 2.2F VIN VIN VIN BST SYNC LX MODE LX MAX17543 C5 0.1F C4 47F LX VCC VOUT 3.3V, 2.5A L1 6.8H R3 127k FB SGND R4 47.5k RESET CF SS C3 5600pF PGND PGND PGND fSW = 500kHz Figure 4b - 3.3V Output, 500kHz Switching Frequency www.maximintegrated.com Maxim Integrated 17 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Typical Application Circuits (continued) VIN (4.5V to 42V) C13 R8 220pF 90.9k R5 210k C1 2.2F EN/UVLO RT VIN VIN VIN BST SYNC C2 2.2F C5 0.1F L1 33H LX MODE FB SGND PGND PGND R3 97.6k C6 15pF CF SS C9 100F C14 100F LX VCC RESETB VOUT 3.3V, 2.5A C4 100F LX MAX17543 C8 2.2F C12 47pF R7 1k R4 36.5k PGND C3 33000pF fSW = 100kHz C12 = 0.5/ (R3 x fSW) R7 = R3/100 C6 = (1.4 x 10-6)/fSW C4 = C9 = C14 = JMK325ABJ107MM-T Figure 5 - 3.3V Output, 100kHz Switching Frequency Ordering Information PART MAX17543ATP+ Package Information PIN-PACKAGE 20 TQFN 4mm x 4 mm Note: All devices operate over the -40C to +125C temperature range, unless otherwise noted. +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. Chip Information PROCESS: BiCMOS www.maximintegrated.com 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 OUTLINE NO. LAND PATTERN NO. 20 TQFN-EP T2044+4 21-0139 90-0409 *EP = Exposed pad. Maxim Integrated 18 MAX17543 4.5V-42V, 2.5A, High-Efficiency, Synchronous Step-Down DC-DC Converter with Internal Compensation Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 0 9/14 Initial release 1 7/16 Updated operating and junction temperature values, added new TOC and text DESCRIPTION -- 1-9, 15, 16 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) 2016 Maxim Integrated Products, Inc. 19 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX17543ATP+ MAX17543ATP+T MAXM17543ALJ+T MAXM17543ALJ+