MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter General Description The MAX17501 high-efficiency, high-voltage, synchronous step-down DC-DC converter with integrated MOSFETs operates over a 4.5V to 60V input voltage range. It delivers output currents up to 500mA at output voltages of 0.9V to 92%VIN. The output voltage is accurate to within 1.7% over -40C to +125C. The MAX17501 is available in a compact TDFN package. Simulation models are available. The device features peak-current-mode control with pulse-width modulation (PWM). Users can choose devices with either pulse frequency modulation (PFM) or forced PWM scheme. PFM devices skip pulses at light load for higher efficiency, while forced-PWM devices operate with fixed switching frequency at any load for noise sensitive-applications. The low-resistance, on-chip MOSFETs ensure high efficiency at full load and simplify the layout. A programmable soft-start feature allows users to reduce input inrush current. The device also incorporates an output enable/undervoltage lockout pin (EN/UVLO) that allows the user to turn on the part at the desired inputvoltage level. An open-drain RESET pin provides a delayed power-good signal to the system upon achieving successful regulation of the output voltage. Applications Industrial Process Control HVAC and Building Control Base Station, VOIP, Telecom Home Theatre Automotive Battery-Powered Equipment General-Purpose Point-of-Load 19-6244; Rev 2; 1/13 Benefits and Features Eliminates External Components and Reduce Total Cost * No Schottky-Synchronous Operation for High Efficiency and Reduced Cost * Internal Compensation and Feedback Divider for 3.3V and 5V Outputs * All-Ceramic Capacitors, Ultra-Compact Layout Reduces Number of DC-DC Regulators to Stock * Wide 4.5V to 60V Input Voltage Range * 0.9V to 92%VIN Output Voltage * Delivers up to 500mA * 600kHz and 300kHz Switching Frequency Options * Available in a 10-Pin, 3mm x 2mm TDFN Package Reduces Power Dissipation * Peak Efficiency > 90% * PFM Feature for High Light-Load Efficiency * Shutdown Current = 0.9A (typ) Operates Reliably in Adverse Industrial Environments * Hiccup-Mode Current Limit, Sink Current Limit, and Autoretry Startup * Built-In Output-Voltage Monitoring (Open-Drain RESET Pin) * Resistor-Programmable EN/UVLO Threshold * Adjustable Soft-Start and Prebiased Power-Up * -40C to +125C Industrial Temperature Range Ordering Information appears at end of data sheet. For related parts and recommended products to use with this part, refer to www.maximintegrated.com/MAX17501.related. MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Absolute Maximum Ratings VIN to GND.............................................................-0.3V to +70V EN/UVLO to GND.......................................-0.3V to (VIN + 0.3V) LX to PGND................................................-0.3V to (VIN + 0.3V) FB, RESET, COMP, SS to GND..............................-0.3V to +6V VCC to GND..............................................................-0.3V to +6V GND to PGND.......................................................-0.3V to +0.3V LX Total RMS Current......................................................... 1.6A Output Short-Circuit Duration.....................................Continuous Continuous Power Dissipation (TA = +70C) (derate 14.9mW/C above +70C) (multilayer board)..1188.7mW Operating Temperature Range......................... -40C to +125C 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. Package Thermal Characteristics (Note 1) TDFN Junction-to-Ambient Thermal Resistance (JA)........67.3C/W Junction-to-Case Thermal Resistance (JC).............18.2C/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 = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1F, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, RESET = unconnected. TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 60 V INPUT SUPPLY (VIN) Input Voltage Range VIN IIN-SH Input Supply Current 4.5 VEN = 0V, shutdown mode IIN-HIBERNATE VFB = 1.03 x VOUT, MAX17501A/B 0.9 3.5 90 145 4.75 6.75 2.5 3.6 A IIN-SW Normal MAX17501E/F/G switching mode, MAX17501H no load VENR VEN rising 1.194 1.218 1.236 VENF VEN falling 1.114 1.135 1.156 V 8 200 nA 4.65 5 5.35 V 40 80 mA mA ENABLE/UVLO (EN/UVLO) EN Threshold VEN-TRUESD EN Input Leakage Current VEN falling, true shutdown IEN VEN = VIN = 60V, TA = +25C VCC 6V < VIN < 12V, 0mA < IVCC < 10mA, 12V < VIN < 60V, 0mA < IVCC < 2mA 0.7 LDO VCC Output Voltage Range VCC Current Limit VCC Dropout VCC UVLO www.maximintegrated.com IVCC-MAX VCC = 4.3V, VIN = 12V 15 VCC-DO VIN = 4.5V, IVCC = 5mA 4.1 VCC-UVR VCC rising 3.85 4 4.15 VCC-UVF VCC falling 3.55 3.7 3.85 V V Maxim Integrated 2 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Electrical Characteristics (continued) (VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1F, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, RESET = unconnected. TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 0.55 0.85 UNITS POWER MOSFETs TA = +25C High-Side pMOS On-Resistance RDS-ONH ILX = 0.5A (sourcing) Low-Side nMOS On-Resistance RDS-ONL ILX = 0.5A (sinking) LX Leakage Current ILX_LKG VEN = 0V, TA = +25C, VLX = (VPGND + 1V) to (VIN - 1V) TA = TJ = +125C (Note 3) 1.2 TA = +25C 0.2 TA = TJ = +125C (Note 3) 0.35 0.47 1 A SOFT-START (SS) Charging Current ISS VSS = 0.5V 4.7 5 5.3 A 0.884 0.9 0.916 V MAX17501A/E, VFB = 3.3V 6.8 12 17 MAX17501B/F, VFB = 5V 6.8 12 17 FEEDBACK (FB/VO) FB Regulation Voltage FB Input Bias Current VFB_REG IFB MAX17501G/H TA = +25NC A MAX17501G/H, VFB = 0.9V 100 nA OUTPUT VOLTAGE (VOUT) Output Voltage Range VOUT MAX17501A/E 3.248 3.3 3.352 MAX17501B/F 4.922 5 5.08 MAX17501G 0.9 0.92 x VIN MAX17501H 0.9 0.965 x VIN V VOUT Threshold for Entering Hibernate Mode VFB_HBR VFB rising, MAX17501A/B 103.3 % VOUT Threshold for Exiting Hibernate Mode VFB_HBF VFB falling, MAX17501A/B 101.3 % TRANSCONDUCTANCE AMPLIFIER (COMP) Transconductance ICOMP = 2.5A, MAX17501G/H 510 590 650 S COMP Source Current ICOMP_SRC MAX17501G/H 19 32 55 A COMP Sink Current ICOMP_SINK MAX17501G/H 19 32 55 A RCS MAX17501G/H 0.9 1 1.1 V/A Current-Sense Transresistance www.maximintegrated.com GM Maxim Integrated 3 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Electrical Characteristics (continued) (VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1F, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, RESET = unconnected. TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS CURRENT LIMIT Peak Current-Limit Threshold IPEAK-LIMIT 0.64 0.76 0.86 A Runaway Current-Limit Threshold IRUNAWAY- 0.65 0.78 0.905 A Sink Current-Limit Threshold ISINK-LIMIT PFM Current-Limit Threshold IPFM MAX17501A/B 560 600 640 fSW VFB > VOUT- MAX17501A/B/E/F/G MAX17501H HICF 280 300 320 VFB < VOUT-HICF 280 300 320 LIMIT MAX17501A/B 0.03 MAX17501E/F/G/H 0.3 0.35 0.4 0.125 A A TIMINGS Switching Frequency Events to Hiccup after Crossing Runaway Current Limit VOUT Undervoltage Trip Level to Cause Hiccup 1 VOUT-HICF VSS > 0.95V (soft-start is done) 69.14 HICCUP Timeout Minimum On-Time Maximum Duty Cycle 71.14 Event 73.14 32,768 tON_MIN DMAX VFB = 0.98 x MAX17501A/B/E/F/G VFB-REG MAX17501H % Cycles 75 120 92 94 96 96.5 97.5 98.5 LX Dead Time kHz 5 ns % ns RESET RESET Output Level Low IRESET = 1mA 0.02 V RESET Output Leakage Current High VFB = 1.01 x VFB-REG, TA = +25C 0.45 A VOUT Threshold for RESET Falling VOUT-OKF VFB falling 90.5 92.5 94.5 % VOUT Threshold for RESET Rising VOUT-OKR VFB rising 93.5 95.5 97.5 % RESET Delay After FB Reaches 95% Regulation VFB rising 1024 Cycles Temperature rising 165 C 10 C THERMAL SHUTDOWN Thermal-Shutdown Threshold Thermal-Shutdown Hysteresis Note 2: All limits are 100% tested at +25C. Limits over temperature are guaranteed by design. Note 3: Guaranteed by design, not production tested. www.maximintegrated.com Maxim Integrated 4 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1F, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, RESET = unconnected, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) 60 VIN = 36V VIN = 12V MAX17501 toc03 65 60 55 VIN = 48V 50 1 10 45 100 50 100 150 200 250 300 350 400 450 500 OUTPUT VOLTAGE vs. LOAD CURRENT (MAX17501A) OUTPUT VOLTAGE vs. LOAD CURRENT (MAX17501B) VIN = 36V VIN = 48V VIN = 24V 5.20 3.40 VIN = 36V 3.35 VIN = 24V VIN = 12V 3.30 5.15 MAX17501 toc06 3.45 50 VIN = 12V VIN = 24V 5.10 VIN = 36V 5.05 VIN = 48V 5.00 4.95 3.25 50 100 150 200 250 300 350 400 450 500 0 4.90 50 100 150 200 250 300 350 400 450 500 0 50 100 150 200 250 300 350 400 450 500 LOAD CURRENT (mA) LOAD CURRENT (mA) OUTPUT VOLTAGE vs. LOAD CURRENT (MAX17501E) OUTPUT VOLTAGE vs. LOAD CURRENT (MAX17501F) SHUTDOWN CURRENT vs. TEMPERATURE OUTPUT VOLTAGE (V) 5.03 3.310 3.305 3.300 VIN = 12V 3.295 VIN = 24V VIN = 36V 5.02 5.01 5.00 4.99 VIN = 48V VIN = 36V VIN = 24V VIN = 12V 4.98 4.97 50 100 150 200 250 300 350 400 450 500 LOAD CURRENT (mA) www.maximintegrated.com 4.95 1.05 1.00 0.95 0.90 0.85 0.80 0.75 4.96 0 1.10 MAX17501 toc09 5.04 SHUTDOWN CURRENT (A) MAX17501 toc07 5.05 MAX17501 toc08 LOAD CURRENT (mA) 3.315 OUTPUT VOLTAGE (V) VIN = 36V VIN = 12V EFFICIENCY vs. LOAD CURRENT (MAX17501F) 60 3.290 VIN = 24V 70 LOAD CURRENT (mA) 80 3.320 75 LOAD CURRENT (mA) 90 40 80 LOAD CURRENT (mA) VIN = 12V 70 VIN = 36V 40 100 85 OUTPUT VOLTAGE (V) 100 10 60 30 90 MAX17501 toc05 1 VIN = 24V VIN = 24V 70 50 OUTPUT VOLTAGE (V) 40 VIN = 12V 80 95 EFFICIENCY (%) 70 50 EFFICIENCY (%) EFFICIENCY (%) 80 90 MAX17501 toc04 EFFICIENCY (%) 90 30 100 MAX17501 toc01 100 EFFICIENCY vs. LOAD CURRENT (MAX17501E) EFFICIENCY vs. LOAD CURRENT (MAX17501B) MAX17501 toc02 EFFICIENCY vs. LOAD CURRENT (MAX17501A) 0 50 100 150 200 250 300 350 400 450 500 LOAD CURRENT (mA) 0.70 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C) Maxim Integrated 5 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) (VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1F, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, RESET = unconnected, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) 80 60 0 20 40 60 80 100 120 CURRENT LIMIT (A) 60 80 1.18 1.17 1.16 FALLING THRESHOLD 1.15 1.14 1.13 1.12 100 120 MAX17501 toc12 MAX17501 toc11 40 RISING THRESHOLD -40 -20 0 20 40 60 80 100 120 FEEDBACK VOLTAGE vs. TEMPERATURE OUTPUT VOLTAGE (V) -40 -20 0 20 40 60 80 100 120 5.000 4.975 4.950 -40 -20 0 20 40 60 80 100 120 MAX17501 toc15 5.025 0.92 FEEDBACK VOLTAGE (V) 5.050 MAX17501 toc14 NO-LOAD OUTPUT VOLTAGE vs. TEMPERATURE (MAX17501F) 0.91 0.90 0.89 0.88 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C) TEMPERATURE (C) PEAK AND RUNAWAY CURRENT LIMIT vs. TEMPERATURE SWITCHING FREQUENCY vs. TEMPERATURE NO-LOAD SOFT-START FROM EN/UVLO (MAX17501A) 0.75 RUNAWAY CURRENT LIMIT PEAK CURRENT LIMIT -40 -20 0 20 40 60 80 TEMPERATURE (C) www.maximintegrated.com 100 120 700 MAX17501 toc18 MAX17501 toc17 MAX17501 toc16 TEMPERATURE (C) 0.80 0.60 20 1.19 NO-LOAD OUTPUT VOLTAGE vs. TEMPERATURE (MAX17501E) 0.85 0.65 0 1.20 TEMPERATURE (C) 3.275 0.70 -40 -20 1.21 TEMPERATURE (C) 3.300 0.90 4.85 1.22 TEMPERATURE (C) 3.325 3.250 4.90 4.80 SWITCHING FREQUENCY (kHz) 3.350 -40 -20 4.95 EN/UVLO THRESHOLD vs. TEMPERATURE 1.23 EN/UVLO THRESHOLD VOLTAGE (V) 100 5.00 NO-LOAD SWITCHING CURRENT (mA) MAX17501 toc10 120 40 OUTPUT VOLTAGE (V) NO-LOAD SWITCHING CURRENT vs. TEMPERATURE (FORCED-PWM OPERATION) MAX17501 toc13 NO-LOAD SWITCHING CURRENT (A) 140 NO-LOAD SWITCHING CURRENT vs. TEMPERATURE (PFM OPERATION) 600 EN/UVLO 2V/div 500 400 VOUT 1V/div RESET 2V/div 300 200 -40 -20 0 20 40 60 80 100 120 1ms/div TEMPERATURE (C) Maxim Integrated 6 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) (VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1F, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, RESET = unconnected, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) NO-LOAD SOFT-START FROM EN/UVLO (MAX17501B) MAX17501 toc19 FULL-LOAD SOFT-START/SHUTDOWN FROM EN/UVLO (MAX17501E) MAX17501 toc20 EN/UVLO 2V/div EN/UVLO 2V/div VOUT 2V/div VOUT 1V/div IOUT 200mA/div RESET 2V/div RESET 5V/div 1ms/div 1ms/div FULL-LOAD SOFT-START/SHUTDOWN FROM EN/UVLO (MAX17501F) NO-LOAD SOFT-START FROM VIN (MAX17501A) MAX17501 toc21 MAX17501 toc22 VIN 20V/div EN/UVLO 2V/div VOUT 2V/div IOUT 200mA/div VOUT 1V/div RESET 2V/div RESET 5V/div 1ms/div 400s/div NO-LOAD SOFT-START FROM VIN (MAX17501B) FULL-LOAD SOFT-START FROM VIN (MAX17501E) MAX17501 toc23 VIN 20V/div VIN 20V/div IOUT 200mA/div VOUT 2V/div VOUT 1V/div RESET 2V/div RESET 5V/div 400s/div www.maximintegrated.com MAX17501 toc24 400s/div Maxim Integrated 7 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) (VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1F, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, RESET = unconnected, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) FULL-LOAD SOFT-START FROM VIN (MAX17501F) SOFT-START WITH 2V PREBIAS (MAX17501A) MAX17501 toc25 VIN 20V/div MAX17501 toc26 EN/UVLO 2V/div VOUT 1V/div IOUT 200mA/div VOUT 2V/div RESET 5V/div RESET 2V/div 400s/div 400s/div SOFT-START WITH 2.5V PREBIAS (MAX17501B) SOFT-START WITH 2V PREBIAS (MAX17501E) MAX17501 toc27 EN/UVLO 2V/div MAX17501 toc28 EN/UVLO 2V/div VOUT 1V/div VOUT 1V/div RESET 5V/div RESET 2V/div 400s/div 400s/div SOFT-START WITH 2.5V PREBIAS (MAX17501F) MAX17501 toc29 LOAD TRANSIENT RESPONSE OF MAX17501A (LOAD CURRENT STEPPED FROM 5mA TO 255mA) MAX17501 toc30 VOUT (AC) 100mV/div EN/UVLO 2V/div VOUT 1V/div IOUT 100mA/div RESET 5V/div 400s/div www.maximintegrated.com 200s/div Maxim Integrated 8 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) (VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1F, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, RESET = unconnected, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) LOAD TRANSIENT RESPONSE OF MAX17501B (LOAD CURRENT STEPPED FROM 5mA TO 255mA) MAX17501 toc31 LOAD TRANSIENT RESPONSE OF MAX17501E (LOAD CURRENT STEPPED FROM NO-LOAD TO 250mA) MAX17501 toc32 VOUT (AC) 100mV/div VOUT (AC) 50mV/div IOUT 100mA/div IOUT 100mA/div 200s/div 20s/div LOAD TRANSIENT RESPONSE OF MAX17501F (LOAD CURRENT STEPPED FROM NO-LOAD TO 250mA) LOAD TRANSIENT RESPONSE OF MAX17501E (LOAD CURRENT STEPPED FROM 250mA TO 500mA) MAX17501 toc33 MAX17501 toc34 VOUT (AC) 50mV/div VOUT (AC) 100mV/div IOUT 200mA/div IOUT 100mA/div 20s/div 20s/div LOAD TRANSIENT RESPONSE OF MAX17501F (LOAD CURRENT STEPPED FROM 250mA TO 500mA) MAX17501 toc35 MAX17501 toc36 VOUT (AC) 50mV/div VOUT (AC) 100mV/div ILX 500mA/div IOUT 200mA/div LX 10V/div 20s/div www.maximintegrated.com SWITCHING WAVEFORMS OF MAX17501F AT 500mA LOAD 2s/div Maxim Integrated 9 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) (VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1F, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, RESET = unconnected, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C. All voltages are referenced to GND, unless otherwise noted.) SWITCHING WAVEFORMS OF MAX17501A AT 15mA LOAD OUTPUT OVERLOAD PROTECTION OF MAX17501F MAX17501 toc37 VOUT (AC) 100mV/div MAX17501 toc38 VOUT 2V/div LX 10V/div ILX 100mA/div IOUT 200mA/div 10s/div 20ms/div BODE PLOT OF MAX17501E AT 500mA LOAD BODE PLOT OF MAX17501F AT 500mA LOAD MAX17501 toc39 fCR = 51kHz PM = 55 4 www.maximintegrated.com 5 6 7 8 9 1 MAX17501 toc40 fCR = 49.8kHz PM = 62 2 4 5 6 7 8 9 1 2 Maxim Integrated 10 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Pin Configuration TOP VIEW MAX17501 10 LX 9 GND 3 8 RESET VCC 4 7 N.C./COMP FB/VO 5 6 SS PGND 1 VIN 2 EN/UVLO + EP* TDFN (3mm x 2mm) *EP = EXPOSED PAD. CONNECT TO GND Pin Description PIN NAME FUNCTION 1 PGND Power Ground. Connect PGND externally to the power ground plane. Connect GND and PGND pins together at the ground return path of the VCC bypass capacitor. 2 VIN 3 EN/UVLO 4 VCC 5 FB/VO 6 SS 7 N.C./COMP For fixed output voltage devices, leave this pin unconnected. For adjustable output voltage devices, connect an RC network from COMP to GND. 8 RESET Open-Drain RESET Output. The RESET output is driven low if FB drops below 92.5% of its set value. RESET goes high 1024 clock cycles after FB rises above 95.5% of its set value. RESET is valid when the device is enabled and VIN is above 4.5V. 9 GND 10 LX Switching Node. Connect LX to the switching side of the inductor. LX is high impedance when the device is in shutdown mode. -- EP Exposed Pad. Connect to the GND pin of the IC. Connect to a large copper plane below the IC to improve heat dissipation capability. www.maximintegrated.com Power-Supply Input. The input supply range is from 4.5V to 60V. Enable/Undervoltage Lockout Input. Drive EN/UVLO high to enable the output voltage. Connect to the center of the resistive divider between VIN and GND to set the input voltage (undervoltage threshold) at which the device turns on. Pull up to VIN for always on. 5V LDO Output. Bypass VCC with 1F ceramic capacitance to GND. Feedback Input. For fixed output voltage devices, directly connect FB/VO to the output. For adjustable output voltage devices, connect FB/VO to the center of the resistive divider between VOUT and GND. Soft-Start Input. Connect a capacitor from SS to GND to set the soft-start time. Analog Ground Maxim Integrated 11 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Block Diagram VCC PGND N DRIVER 5A SS LX MAX17501 HICCUP SS P DRIVER VIN CURRENT SENSE VCC PWM COMPARATOR LDO CLK PWM, PFM LOGIC OSC COMP HICCUP SLOPE COMPENSATION START EN RESET LOGIC SS 900mV REFERENCE SWITCHOVER LOGIC RESET COMP N.C./COMP GM FB INTERNAL COMPENSATION (FOR A, B, E, F VERSIONS) GND www.maximintegrated.com Maxim Integrated 12 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Detailed Description GND. The device employs an undervoltage-lockout circuit that disables the internal linear regulator when VCC falls below 3.7V (typical). The internal VCC linear regulator can source up to 40mA (typical) to supply the device and to power the low-side gate driver. The device uses a peak-current-mode control scheme. An internal transconductance error amplifier generates an integrated error voltage. The error voltage sets the duty cycle using a PWM comparator, a high-side current-sense amplifier, and a slope-compensation generator. At each rising edge of the clock, the high-side p-channel MOSFET turns on and remains on until either the appropriate or maximum duty cycle is reached, or the peak current limit is detected. Operating Input Voltage Range The MAX17501 synchronous step-down regulator operates from 4.5V to 60V and delivers up to 500mA load current. Output voltage regulation accuracy meets 1.7% over temperature. 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 n-channel MOSFET turns on and remains on until either the next rising edge of the clock arrives or sink current limit is detected. The inductor releases the stored energy as its current ramps down, and provides current to the output (the internal low RDSON pMOS/nMOS switches ensure high efficiency at full load). This device also integrates enable/undervoltage lockout (EN/UVLO), adjustable soft-start time (SS), and opendrain reset output (RESET) functionality. PFM Operation The A and B versions of the MAX17501 feature a PFM scheme to improve light load efficiency. At light loads, once the part enters PFM mode, the inductor current is forced to a fixed peak of 125mA (typical) every clock cycle until the output rises to 103.3% of nominal voltage. Once output reaches 103.3% of nominal voltage, both highside and low-side FETs are turned off and the part enters hibernate operation until the load discharges output to 101.3% of nominal voltage. Most of the internal blocks are turned off in hibernate operation to save quiescent current. Such an operation reduces the effective switching frequency of the converter at light loads, resulting in reduced switching losses and improved light load efficiency. The part naturally exits PFM mode when the load current exceeds 62.5mA (typical). Linear Regulator (VCC) 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 VCC linear regulator should be bypassed with a 1F ceramic capacitor to www.maximintegrated.com The maximum operating input voltage is determined by the minimum controllable on-time and the minimum operating input voltage is determined by the maximum duty cycle and circuit voltage drops. The minimum and maximum operating input voltages for a given output voltage should be calculated as: VIN(MIN) = VOUT + (I OUT(MAX) x (R DCR + 0.47)) D MAX + (I OUT(MAX) x 0.73) 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 switching frequency (maximum) and tON(MIN) is the worst-case minimum switch on-time (120ns). The following table lists the fSW(MAX) and DMAX values to be used for calculation for different versions of the MAX17501: PART VERSION fSW (MAX) (kHz) DMAX MAX17501A/B/E/F/G 640 0.92 MAX17501H 320 0.965 Overcurrent Protection/HICCUP Mode The device 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 760mA (typ). A runaway current limit on the high-side switch current at 780mA (typ) protects the device under high input voltage, short-circuit conditions when there is insufficient output voltage available to restore the inductor current that built up during the on period of the step-down converter. One occurrence of the runaway current limit triggers a hiccup mode. In addition, if due to a fault condition, output voltage drops to 71.14% (typ) of its nominal value any time after soft-start is complete, hiccup mode is triggered. Maxim Integrated 13 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter 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, soft-start is attempted again. This operation results in minimal power dissipation under overload fault conditions. the input DC bus further. In applications where the source is located distant from the device input, an electrolytic capacitor should be added in parallel to the 1F ceramic capacitor to provide necessary damping for potential oscillations caused by the longer input power path and input ceramic capacitor. The device includes a RESET comparator to monitor the output voltage. The open-drain RESET output requires an external pullup resistor. RESET can sink 2mA of current while low. RESET goes high (high impedance) 1024 switching cycles after the regulator output increases above 95.5% of the designated nominal regulated voltage. RESET goes low when the regulator output voltage drops to below 92.5% of the nominal regulated voltage. RESET also goes low during thermal shutdown. RESET is valid when the device is enabled and VIN is above 4.5V. Inductor Selection Prebiased Output where VIN, VOUT, and fSW are nominal values. Ensure that at any operating condition, the ratio (VOUT/(L x fSW)) is between 150mA and 250mA. RESET Output When the device starts into a prebiased output, both the high-side and low-side switches are turned off so 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 first with the high-side switch. The output voltage is then smoothly ramped up to the target value in alignment with the internal reference. Thermal-Overload Protection Thermal-overload 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 the device 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-overload protection in normal operation. Applications Information Input Capacitor Selection The discontinuous input-current waveform of the buck converter causes large ripple currents in the input capacitor. The switching frequency, peak inductor current, and the allowable peak-to-peak voltage ripple that reflects back to the source dictate the capacitance requirement. The device's high switching frequency allows the use of smaller value input capacitors. X7R capacitors are recommended in industrial applications for their temperature stability. A minimum value of 1F should be used for the input capacitor. Higher values help reduce the ripple on www.maximintegrated.com Three key inductor parameters must be specified for operation with the device: inductance value (L), inductor saturation current (ISAT), and DC resistance (RDCR). The switching frequency, input voltage, and output voltage determine the inductor value as follows: L= VOUT x (VIN - VOUT ) 0.15 x VIN x f SW 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 (IPEAK-LIMIT (typ) = 0.76A for the device). Output Capacitor Selection X7R ceramic output capacitors are preferred due to their stability over temperature in industrial applications. The output capacitor is usually sized to support a step load of 50% of the maximum output current in the application, so the output-voltage deviation is contained to 3% of the output-voltage change. For fixed 3.3V and 5V output voltage versions, connect a minimum of 10F (1206) capacitor at the output. For adjustable output voltage versions, the output capacitance can be calculated as follows: C OUT= 1 I STEP x t RESPONSE x 2 VOUT t RESPONSE 0.33 1 + fC f SW where ISTEP is the load current step, tRESPONSE is the response time of the controller, VOUT is the allowable output-voltage deviation, fC is the target closed-loop crossover frequency, and fSW is the switching frequency. Select fC to be 1/12th of fSW. Consider DC bias and aging effects while selecting the output capacitor. Maxim Integrated 14 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Soft-Start Capacitor Selection The MAX17501 implements adjustable soft-start operation to reduce inrush current. A capacitor connected from the SS pin to GND programs the soft-start period. The soft-start time (tSS) is related to the capacitor connected at SS (CSS) by the following equation: C= SS 5.55 x t SS where tSS is in milliseconds and CSS is in nanofarads. For example, to program a 600s soft-start time, a 3300pF capacitor should be connected from the SS pin to GND. Ensure that (CSEL x VOUT/tSS) is less than 150mA, where CSEL is the selected output capacitance. Adjusting Output Voltage The MAX17501A/E and MAX17501B/F have preset output voltages of 3.3V and 5.0V, respectively. Connect FB/ VO directly to the positive terminal of the output capacitor (see the Typical Applications Circuits). The MAX17501G/H offer an adjustable output voltage. Set the output voltage with a resistive voltage-divider connected from the positive terminal of the output capacitor (VOUT) to GND (see Figure 1). Connect the center node of the divider to FB/VO. To optimize efficiency and output accuracy, use the following procedure to choose the values of R4 and R5: For MAX17501G, select the parallel combination of R4 and R5, Rp to be less than 15k. For the MAX17501H, select the parallel combination of R4 and R5, Rp to be less than 30k. Once Rp is selected, calculate R4 as: R4 = Calculate R5 as follows: R5 = Choose R1 to be 3.3M, and then calculate R2 as: R2 = R1x 1.218 (VINU - 1.218) where VINU is the voltage at which the device is required to turn on. For adjustable output voltage devices, ensure that VINU is higher than 0.8 x VOUT. VIN R1 FB/VO R5 GND Figure 1. Setting the Output Voltage www.maximintegrated.com R4 x 0.9 (VOUT - 0.9) Setting the Input Undervoltage Lockout Level The device offers an adjustable input undervoltagelockout level. Set the voltage at which the device turns on with a resistive voltage-divider connected from VIN to GND (see Figure 2). Connect the center node of the divider to EN/UVLO. VOUT R4 Rp x VOUT 0.9 EN/UVLO R2 GND Figure 2. Adjustable EN/UVLO Network Maxim Integrated 15 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter External Loop Compensation for Adjustable Output Versions The MAX17501 uses peak current-mode control scheme and needs only a simple RC network to have a stable, high-bandwidth control loop for the adjustable output voltage versions. The basic regulator loop is modeled as a power modulator, an output feedback divider, and an error amplifier. The power modulator has DC gain GMOD(dc), with a pole and zero pair. The following equation defines the power modulator DC gain: 1 G MOD(dc) = 1 0.2 0.5 - D + + R LOAD VIN f SW x L SEL where RLOAD = VOUT/IOUT(MAX), fSW is the switching frequency, LSEL is the selected output inductance, D is the duty ratio, D = VOUT/VIN. The compensation network is shown in Figure 3. RZ can be calculated as: R= Z 12000 x f C x C SEL x VOUT where RZ is in . Choose fC to be 1/12th of the switching frequency. CZ can be calculated as follows: CZ = C SEL x G MOD(dc) RZ CP can be calculated as follows: CP = 1 - 5pF x R Z x f SW Power Dissipation The exposed pad of the IC should be properly soldered to the PCB to ensure good thermal contact. Ensure the junction temperature of the device does not exceed +125C under the operating conditions specified for the power supply. TO COMP PIN RZ CP CZ At high ambient temperatures, based on the operating condition, the heat dissipated in the IC might exceed the maximum junction temperature of +125C. Heat sink should be used to reduce JA at such operating conditions. For typical applications, refer to the temperature derating curves included in the MAX17501 Evaluation Kit data sheet. To prevent the part from exceeding 125C junction temperature, users need to do some thermal analysis. At a particular operating condition, the power losses that lead to temperature rise of the device 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 output power, is is the efficiency of the device, and RDCR is the DC resistance of the output inductor (refer to the Typical Operating Characteristics in the evaluation kit data sheets for more information on efficiency at typical operating conditions). The maximum power that can be dissipated in the 10-pin TDFN-EP package is 1188.7mW at +70C temperature. The power dissipation capability should be derated as the temperature goes above +70C at 14.9mW/C. For a typical multilayer board, the thermal performance metrics for the package are given as: JA = 67.3C W JC = 18.2C W The junction temperature of the device can be estimated at any given maximum ambient temperature (TA_MAX) from the following equation: 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 heat sinks, then the junction temperature of the device can be estimated at any given maximum ambient temperature as: T= J_MAX TEP_MAX + ( JC x PLOSS ) Figure 3. External Compensation Network www.maximintegrated.com Maxim Integrated 16 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter PCB Layout Guidelines Careful PCB layout is critical to achieve low switching losses and stable operation. For a sample layout that ensures first-pass success, refer to the MAX17501 evaluation kit layouts available at www.maximintegrated.com. Follow these guidelines for good PCB layout: 1) All connections carrying pulsed currents must be very short and as wide as possible. The loop area of these connections must be made very small to reduce stray inductance and radiated EMI. 2) A ceramic input filter capacitor should be placed close to the VIN pin of the device. The bypass capacitor for the VCC pin should also be placed close to the VCC pin. External compensation components should be PGND PLANE placed close to the IC and far from the inductor. The feedback trace should be routed as far as possible from the inductor. 3) The analog small-signal ground and the power ground for switch ing currents must be kept separate. They should be connected together at a point where switching activity is at minimum, typically the return terminal of the VCC bypass capacitor. The ground plane should be kept continuous as much as possible. 4) A number of thermal vias that connect to a large ground plane should be provided under the exposed pad of the device, for efficient heat dissipation. Figure 4 and 5 show the recommended component placement for MAX17501. VOUT PLANE C4 L1 C1 EP VIN PLANE LX PLANE R1 R2 RESET C2 R4 C3 GND PLANE VIAS TO BOTTOM SIDE PGND PLANE VIAS TO BOTTOM SIDE VOUT TRACK VIAS TO BOTTOM SIDE GND PLANE Figure 4. Recommended Component Placement for MAX17501A/B/E/F www.maximintegrated.com Maxim Integrated 17 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter PGND PLANE VOUT PLANE C4 L1 C1 LX PLANE EP VIN PLANE R1 R2 RESET R3 C2 R4 C3 R5 C9 C5 GND PLANE VIAS TO BOTTOM SIDE PGND PLANE VIAS TO BOTTOM SIDE VOUT TRACK VIAS TO BOTTOM SIDE GND PLANE Figure 5. Recommended Component Placement for MAX17501G/H www.maximintegrated.com Maxim Integrated 18 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Applications Circuits VIN 24V C1 1F 1206 LX VIN 1 JU1 2 3 L1 33H C4 10F, 1206 R1 3.32M EN/UVLO R2 866k C2 1F C3 3300pF PGND VOUT 3.3V, 500mA MAX17501 GND VCC FB/VO SS RESET N.C. RESET Figure 6. MAX17501A/E Application Circuit (3.3V Output, 500mA Maximum Load Current, 600kHz Switching Frequency) VIN 24V C1 1F 1206 LX VIN 1 JU1 2 3 L1 47H C4 10F, 1206 R1 3.32M EN/UVLO R2 866k C2 1F C3 3300pF PGND VOUT 5V, 500mA MAX17501 VCC SS N.C. GND FB/VO RESET RESET Figure 7. MAX17501B/F Application Circuit (5V Output, 500mA Maximum Load Current, 600kHz Switching Frequency) www.maximintegrated.com Maxim Integrated 19 MAX17501 VIN 24V 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter C1 1F 1206 LX VIN 1 JU1 2 3 PGND EN/UVLO R2 316k C3 6800pF VOUT 12V, 500mA C4 4.7F, 1206 R1 3.32M C2 1F R4 174k MAX17501 GND VCC FB/VO SS R5 14k COMP C9 10pF L1 100H RESET RESET R3 27.4k C5 1200pF Figure 8. MAX17501G Application Circuit (12V Output, 500mA Maximum Load Current, 600kHz Switching Frequency) VIN 24V C1 2.2F 1210 LX VIN 1 JU1 2 3 C4 22F, 1210 R1 3.32M EN/UVLO R2 1M C2 1F C3 6800pF PGND VCC SS VOUT 2.5V, 500mA R4 69.8k MAX17501 COMP C9 47pF L1 47H GND FB/VO R5 39.2k RESET RESET R3 20k C5 2200pF Figure 9. MAX17501H Application Circuit (2.5V Output, 500mA Maximum Load Current, 300kHz Switching Frequency) www.maximintegrated.com Maxim Integrated 20 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Ordering Information/Part Selector Guide PART PIN-PACKAGE OUTPUT VOLTAGE (V) SWITCHING FREQUENCY (kHz) MODE MAX17501AATB+ 10 TDFN-EP* 3.3 600 PFM MAX17501BATB+ 10 TDFN-EP* 5 600 PFM MAX17501EATB+ 10 TDFN-EP* 3.3 600 PWM MAX17501FATB+ 10 TDFN-EP* 5 600 PWM MAX17501GATB+ 10 TDFN-EP* Adjustable 600 PWM MAX17501HATB+ 10 TDFN-EP* Adjustable 300 PWM +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed paddle. 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 OUTLINE NO. LAND PATTERN NO. 10 TDFN T1032N+1 21-0429 90-0082 *EP = Exposed pad. www.maximintegrated.com Maxim Integrated 21 MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter Revision History REVISION NUMBER REVISION DATE PAGES CHANGED DESCRIPTION 0 5/12 Initial release 1 11/12 Added MAX17501A, MAX17501B, MAX17501G, MAX17501H to data sheet 1-22 -- 2 1/13 Added explanation on detailed condition for RESET 11, 14 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) 2013 Maxim Integrated Products, Inc. 22 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX17501AEUB+ MAX17501BEUB+ MAX17501AEUB+T MAX17501BEUB+T MAX17501AATB+T MAX17501BATB+T MAX17501CATB+T MAX17501DATB+T