19-2979; Rev 2; 5/04 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter Features The MAX5033 easy-to-use, high-efficiency, high-voltage, step-down DC-DC converter operates from an input voltage up to 76V and consumes only 270µA quiescent current at no load. This pulse-width modulated (PWM) converter operates at a fixed 125kHz switching frequency at heavy loads, and automatically switches to pulseskipping mode to provide low quiescent current and high efficiency at light loads. The MAX5033 includes internal frequency compensation simplifying circuit implementation. The device uses an internal low-onresistance, high-voltage, DMOS transistor to obtain high efficiency and reduce overall system cost. This device includes undervoltage lockout, cycle-by-cycle current limit, hiccup-mode output short-circuit protection, and thermal shutdown. ♦ Wide 7.5V to 76V Input Voltage Range ♦ Fixed (3.3V, 5V, 12V) and Adjustable (1.25V to 13.2V) Voltage Versions ♦ 500mA Output Current ♦ Efficiency Up to 94% ♦ Internal 0.4Ω High-Side DMOS FET ♦ 270µA Quiescent Current at No Load, 10µA Shutdown Current ♦ Internal Frequency Compensation ♦ Fixed 125kHz Switching Frequency ♦ Thermal Shutdown and Short-Circuit Current Limit ♦ 8-Pin SO and PDIP Packages The MAX5033 delivers up to 500mA output current. The output current may be limited by the maximum power dissipation capability of the package. External shutdown is included, featuring 10µA (typ) shutdown current. The MAX5033A/B/C versions have fixed output voltages of 3.3V, 5V, and 12V, respectively, while the MAX5033D features an adjustable output voltage, from 1.25V to 13.2V. Ordering Information OUTPUT PINVOLTAGE PACKAGE (V) PART TEMP RANGE MAX5033AUSA 0°C to +85°C 8 SO MAX5033AUPA 0°C to +85°C 8 PDIP MAX5033AASA -40°C to +125°C MAX5033BUSA 0°C to +85°C 8 SO MAX5033BUPA 0°C to +85°C 8 PDIP MAX5033BASA -40°C to +125°C MAX5033CUSA 0°C to +85°C 8 SO MAX5033CUPA 0°C to +85°C 8 PDIP Automotive MAX5033CASA -40°C to +125°C Consumer Electronics MAX5033DUSA 0°C to +85°C 8 SO MAX5033DUPA 0°C to +85°C 8 PDIP MAX5033DASA -40°C to +125°C The MAX5033 is available in space-saving 8-pin SO and 8-pin plastic DIP packages and operates over the automotive (-40°C to +125°C) temperature range. Applications Industrial Distributed Power 3.3 8 SO 5.0 8 SO 12 8 SO ADJ 8 SO Pin Configuration Typical Operating Circuit VIN 7.5V TO 76V VIN 47µF BST 0.1µF 220µH MAX5033 LX R1 D1 50SQ100 ON/OFF 33µF ON FB R2 OFF VD SGND VOUT 5V, 0.5A GND 0.1µF BST 1 8 LX VD 2 7 VIN SGND 3 6 GND FB 4 5 ON/OFF MAX5033 SO/PDIP ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX5033 General Description MAX5033 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter ABSOLUTE MAXIMUM RATINGS (Voltages referenced to GND, unless otherwise specified.) VIN .........................................................................-0.3V to +80V SGND ....................................................................-0.3V to +0.3V LX.................................................................-0.8V to (VIN + 0.3V) BST ...............................................................-0.3V to (VIN + 10V) BST (transient < 100ns) ................................-0.3V to (VIN + 15V) BST to LX................................................................-0.3V to +10V BST to LX (transient < 100ns) ................................-0.3V to +15V ON/OFF........................................................-0.3V to (VIN + 0.3V) VD...........................................................................-0.3V to +12V FB MAX5033A/MAX5033B/MAX5033C ...................-0.3V to +15V MAX5033D .........................................................-0.3V to +12V VOUT Short-Circuit Duration...........................................Indefinite VD Short-Circuit Duration ..............................................Indefinite Continuous Power Dissipation (TA = +70°C) 8-Pin PDIP (derate 9.1mW/°C above +70°C)...............727mW 8-Pin SO (derate 5.9mW/°C above +70°C)..................471mW Operating Temperature Range MAX5033_U_ _ ...................................................0°C to +85°C MAX5033_A_ _ ..............................................-40°C to +125°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+150°C Lead Temperature (soldering, 10s) .................................+300°C 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 (MAX5033_U_ _) (VIN = +12V, VON/OFF = +12V, IOUT = 0, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C. See the Typical Application Circuit.) PARAMETER Input Voltage Range Undervoltage Lockout Output Voltage Feedback Voltage Efficiency Quiescent Supply Current Shutdown Current SYMBOL VIN CONDITIONS VFB η IQ ISHDN MAX 76.0 MAX5033B 7.5 76.0 MAX5033C 15 76 MAX5033D 7.5 76.0 UVLO VOUT TYP 7.5 5.2 3.185 3.3 3.415 MAX5033B, VIN = 7.5V to 76V, IOUT = 20mA to 500mA 4.85 5.0 5.15 MAX5033C, VIN = 15V to 76V, IOUT = 20mA to 500mA 11.64 12 12.36 VIN = 7.5V to 76V, MAX5033D 1.192 1.221 1.250 VIN = 12V, ILOAD = 500mA, MAX5033A 86 VIN = 12V, ILOAD = 500mA, MAX5033B 90 VIN = 24V, ILOAD = 500mA, MAX5033C 94 VIN = 12V, VOUT = 5V, ILOAD = 500mA, MAX5033D 90 VFB = 3.5V, VIN = 7.5V to 76V, MAX5033A 270 440 VFB = 5.5V, VIN = 7.5V to 76V, MAX5033B 270 440 VFB = 13V, VIN = 15V to 76V, MAX5033C 270 440 VFB = 1.3V, MAX5033D 270 440 VON/OFF = 0V, VIN = 7.5V to 76V 10 45 1.5 2.1 ILIM (Note 1) Switch Leakage Current IOL VIN = 76V, VON/OFF = 0V, VLX = 0V 0.95 1 _______________________________________________________________________________________ UNITS V V MAX5033A, VIN = 7.5V to 76V, IOUT = 20mA to 500mA Peak Switch Current Limit 2 MIN MAX5033A V V % µA µA A µA 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter (VIN = +12V, VON/OFF = +12V, IOUT = 0, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C. See the Typical Application Circuit.) PARAMETER Switch On-Resistance PFM Threshold SYMBOL RDS(ON) IPFM FB Input Bias Current IB CONDITIONS MIN TYP MAX UNITS 0.4 0.80 Ω 35 65 95 mA MAX5033D -150 +0.01 +150 nA Rising trip point 1.53 1.69 1.85 ISWITCH = 500mA Minimum switch current in any cycle ON/OFF CONTROL INPUT ON/OFF Input-Voltage Threshold VON/OFF ON/OFF Input-Voltage Hysteresis VHYST ON/OFF Input Current ION/OFF 100 VON/OFF = 0V to VIN V mV 10 150 nA 125 135 kHz OSCILLATOR Oscillator Frequency fOSC Maximum Duty Cycle DMAX 109 MAX5033D 95 % VOLTAGE REGULATOR Regulator Output Voltage VD Dropout Voltage ∆VD/∆IVD Load Regulation VIN = 8.5V to 76V, IL = 0mA 6.9 7.8 8.8 V 7.5V ≤ VIN ≤ 8.5V, IL = 1mA 2.0 V 0 to 5mA 150 Ω SO package (JEDEC 51) 170 DIP package (JEDEC 51) 110 PACKAGE THERMAL CHARACTERISTICS Thermal Resistance (Junction to Ambient) θJA °C/W THERMAL SHUTDOWN Thermal-Shutdown Junction Temperature Thermal-Shutdown Hysteresis TSH +160 °C THYST 20 °C ELECTRICAL CHARACTERISTICS (MAX5033_A_ _) (VIN = +12V, VON/ OFF = +12V, IOUT = 0, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. See the Typical Application Circuit.) (Note 2) PARAMETER Input Voltage Range Undervoltage Lockout Output Voltage SYMBOL VIN CONDITIONS MIN MAX MAX5033A 7.5 76.0 MAX5033B 7.5 76.0 MAX5033C 15 76 MAX5033D 7.5 UVLO VOUT TYP UNITS V 76.0 5.2 V MAX5033A, VIN = 7.5V to 76V, IOUT = 20mA to 500mA 3.185 3.3 3.415 MAX5033B, VIN = 7.5V to 76V, IOUT = 20mA to 500mA 4.825 5.0 5.175 MAX5033C, VIN = 15V to 76V, IOUT = 20mA to 500mA 11.58 12 12.42 V _______________________________________________________________________________________ 3 MAX5033 ELECTRICAL CHARACTERISTICS (MAX5033_U_ _) (continued) MAX5033 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter ELECTRICAL CHARACTERISTICS (MAX5033_A_ _) (VIN = +12V, VON/ OFF = +12V, IOUT = 0, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. See the Typical Application Circuit.) (Note 2) PARAMETER Feedback Voltage Efficiency Quiescent Supply Current Shutdown Current SYMBOL VFB η IQ ISHDN CONDITIONS VIN = 7.5V to 76V, MAX5033D 90 94 VIN = 12V, VOUT = 5V, ILOAD = 500mA, MAX5033D 90 VFB = 3.5V, VIN = 7.5V to 76V, MAX5033A 270 440 VFB = 5.5V, VIN = 7.5V to 76V, MAX5033B 270 440 VFB = 13V, VIN = 15V to 76V, MAX5033C 270 440 VFB = 1.3V, MAX5033D 270 440 VON/OFF = 0V, VIN = 7.5V to 76V 10 45 1.5 2.20 (Note 1) VIN = 76V, VON/OFF = 0V, VLX = 0V IPFM IB V VIN = 24V, ILOAD = 500mA, MAX5033C IOL FB Input Bias Current UNITS VIN = 12V, ILOAD = 500mA, MAX5033B ILIM PFM Threshold MAX 1.250 86 Switch Leakage Current RDS(ON) TYP 1.221 VIN = 12V, ILOAD = 500mA, MAX5033A Peak Switch Current Limit Switch On-Resistance MIN 1.192 0.95 1 ISWITCH = 500mA Minimum switch current in any cycle % 0.4 µA µA A µA 0.80 Ω 35 65 110 mA MAX5033D -150 +0.01 +150 nA Rising trip point 1.50 1.69 1.85 ON/OFF CONTROL INPUT ON/OFF Input-Voltage Threshold VON/OFF ON/OFF Input-Voltage Hysteresis VHYST ON/OFF Input Current ION/OFF 100 VON/OFF = 0V to VIN V mV 10 150 nA 125 137 kHz OSCILLATOR Oscillator Frequency fOSC Maximum Duty Cycle DMAX 105 MAX5033D 95 % VOLTAGE REGULATOR Regulator Output Voltage VD Dropout Voltage Load Regulation ∆VD/∆IVD VIN = 8.5V to 76V, IL = 0mA 6.5 7.8 9.0 V 7.5V ≤ VIN ≤ 8.5V, IL = 1mA 2.0 V 0 to 5mA 150 Ω SO package (JEDEC 51) 170 DIP package (JEDEC 51) 110 PACKAGE THERMAL CHARACTERISTICS Thermal Resistance (Junction to Ambient) θJA °C/W THERMAL SHUTDOWN Thermal-Shutdown Junction Temperature Thermal-Shutdown Hysteresis TSH +160 °C THYST 20 °C Note 1: Switch current at which the current limit is activated. Note 2: All limits at -40°C are guaranteed by design, not production tested. 4 _______________________________________________________________________________________ 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter 12.3 IOUT = 0.1A 5.05 LINE REGULATION (MAX5033CASA, VOUT = 12V) 12.4 MAX5033 toc02 5.10 MAX5033 toc01 12.4 VOUT vs. TEMPERATURE (MAX5033BASA, VOUT = 5V) 12.3 12.1 VOUT (V) 12.2 IOUT = 0.1A VOUT (V) 5.00 IOUT = 0.5A 12.0 IOUT = 0A 12.1 12.0 IOUT = 0.5A IOUT = 0.5A 4.95 11.9 11.9 11.8 4.90 -50 -25 25 0 100 125 150 75 50 11.8 -50 -25 0 TEMPERATURE (°C) 10 12.3 20 30 40 VIN = 24V VOUT (V) VOUT (V) IOUT = 0.5A 12.1 12.0 VIN = 76V 4.95 70 80 5.10 VIN = 7.5V, 24V 5.05 5.00 60 LOAD REGULATION (MAX5033BASA, VOUT = 5V) 5.05 12.2 50 INPUT VOLTAGE (V) MAX5033 toc05 12.4 MAX5033 toc04 IOUT = 0A 50 75 100 125 150 TEMPERATURE (°C) LOAD REGULATION (MAX5033CASA, VOUT = 12V) LINE REGULATION (MAX5033BASA, VOUT = 5V) 5.10 25 MAX5033 toc06 VOUT (V) 12.2 VOUT (V) MAX5033 toc03 VOUT vs. TEMPERATURE (MAX5033CASA, VOUT = 12V) 5.00 VIN = 76V 4.95 11.9 11.8 4.90 16 26 36 46 56 66 200 300 400 500 100 200 300 400 ILOAD (mA) EFFICIENCY vs. LOAD CURRENT (MAX5033BASA, VOUT = 5V) EFFICIENCY vs. LOAD CURRENT (MAX5033CASA, VOUT = 12V) OUTPUT CURRENT LIMIT vs. TEMPERATURE 60 VIN = 24V 50 VIN = 76V VIN = 48V VIN = 24V 60 VIN = 76V 50 VIN = 48V 40 30 30 20 20 10 10 0 VIN = 15V 70 200 300 LOAD CURRENT (mA) 400 500 2.0 1.7 1.4 1.1 0.8 MAX5033BASA 5% DROP IN VOUT 0.5 0 100 500 MAX5033 toc09 80 EFFICIENCY (%) VIN = 7.5V VIN = 12V 90 OUTPUT CURRENT LIMIT (A) 100 MAX5033 toc07 80 70 0 0 ILOAD (mA) 90 EFFICIENCY (%) 100 INPUT VOLTAGE (V) 100 40 4.90 0 76 MAX5033 toc08 6 0 100 200 300 LOAD CURRENT (mA) 400 500 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX5033 Typical Operating Characteristics (VIN = 12V, VON/OFF = 12V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. See the Typical Application Circuit, if applicable.) Typical Operating Characteristics (continued) (VIN = 12V, VON/OFF = 12V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. See the Typical Application Circuit, if applicable.) OUTPUT CURRENT LIMIT vs. INPUT VOLTAGE 1.1 MAX5033BASA VOUT = 5V 5% DROP IN VOUT 0.5 320 280 240 16 26 36 46 56 66 76 290 260 230 -50 -25 25 0 6 100 125 150 75 50 16 26 36 56 46 INPUT VOLTAGE (V) TEMPERATURE (°C) INPUT VOLTAGE (V) SHUTDOWN CURRENT vs. TEMPERATURE SHUTDOWN CURRENT vs. INPUT VOLTAGE OUTPUT VOLTAGE vs. INPUT VOLTAGE 15 10 5 15 0 50 75 100 125 150 TEMPERATURE (°C) 9 6 5 3 IOUT = 0.3A IOUT = 0.5A 0 6 25 MAX5033CASA VOUT = 12V VON/OFF = VIN 12 10 0 0 16 26 36 46 56 66 76 0 3 6 MAX5033BASA LOAD-TRANSIENT RESPONSE MAX5033 toc16 9 15 MAX5033BASA LOAD-TRANSIENT RESPONSE MAX5033 toc17 VOUT = 5V 12 VIN (V) INPUT VOLTAGE (V) MAX5033BASA LOAD-TRANSIENT RESPONSE 76 MAX5033 toc15 20 VOUT (V) SHUTDOWN CURRENT (µA) 20 66 15 MAX5033 toc14 25 MAX5033 toc13 25 -50 -25 320 200 200 6 MAX5033 toc12 MAX5033 toc11 360 350 QUIESCENT SUPPLY CURRENT (µA) 1.4 400 QUIESCENT SUPPLY CURRENT (µA) MAX5033 toc10 OUTPUT CURRENT LIMIT (A) 1.7 0.8 QUIESCENT SUPPLY CURRENT vs. INPUT VOLTAGE QUIESCENT SUPPLY CURRENT vs. TEMPERATURE 2.0 SHUTDOWN CURRENT (µA) MAX5033 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter MAX5033 toc18 VOUT = 5V VOUT = 5V A A A B B B 400µs/div A: VOUT, 200mV/div, AC-COUPLED B: IOUT, 500mA/div, 100mA TO 500mA 6 400µs/div A: VOUT, 100mV/div, AC-COUPLED B: IOUT, 200mA/div, 100mA TO 250mA 400µs/div A: VOUT, 100mV/div, AC-COUPLED B: IOUT, 500mA/div, 250mA TO 500mA _______________________________________________________________________________________ 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter MAX5033BASA LX WAVEFORMS MAX5033BASA LX WAVEFORMS MAX5033 toc19 MAX5033BASA LX WAVEFORMS MAX5033 toc20 MAX5033 toc21 A A A 0 0 0 B B B 0 0 4µs/div MAX5033BASA STARTUP WAVEFORM (IO = 0) 4µs/div 4µs/div A: SWITCH VOLTAGE, 20V/div, VIN = 48V B: INDUCTOR CURRENT, 100mA/div (IOUT = 30mA) A: SWITCH VOLTAGE (LX PIN), 20V/div, VIN = 48V B: INDUCTOR CURRENT, 100mA/div (IOUT = 0) MAX5033BASA STARTUP WAVEFORM (IO = 0.5A) PEAK SWITCH CURRENT LIMIT vs. INPUT VOLTAGE MAX5033 toc23 2.0 A A B B PEAK SWITCH CURRENT LIMIT (A) MAX5033 toc22 MAX5033 toc24 A: SWITCH VOLTAGE (LX PIN) 20V/div, VIN = 48V B: INDUCTOR CURRENT, 200mA/div, (IOUT = 500mA) 1.7 1.4 1.1 0.8 MAX5033BASA VOUT = 5V 5% DROP IN VOUT 0.5 1ms/div 1ms/div A: VON/OFF, 2V/div B: VOUT, 2V/div A: VON/OFF, 2V/div B: VOUT, 2V/div 6 16 26 36 46 56 66 76 INPUT VOLTAGE (V) _______________________________________________________________________________________ 7 MAX5033 Typical Operating Characteristics (continued) (VIN = 12V, VON/OFF = 12V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. See the Typical Application Circuit, if applicable.) 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter MAX5033 Pin Description PIN NAME 1 BST Boost Capacitor Connection. Connect a 0.1µF ceramic capacitor from BST to LX. FUNCTION 2 VD Internal Regulator Output. Bypass VD to GND with a 0.1µF ceramic capacitor. 3 SGND Internal Connection. SGND must be connected to GND. Output Sense Feedback Connection. For fixed output voltage (MAX5033A, MAX5033B, MAX5033C), connect FB to VOUT. For adjustable output voltage (MAX5033D), use an external resistive voltage-divider to set VOUT. VFB regulating set point is 1.22V. 4 FB 5 ON/OFF 6 GND 7 VIN Input Voltage. Bypass VIN to GND with a low-ESR capacitor as close to the device as possible. 8 LX Source Connection of Internal High-Side Switch Shutdown Control Input. Pull ON/OFF low to put the device in shutdown mode. Drive ON/OFF high for normal operation. Ground Simplified Block Diagram VIN ON/OFF ENABLE REGULATOR (FOR ANALOG) 1.69V REGULATOR (FOR DRIVER) VD CPFM IREF-PFM HIGH-SIDE CURRENT SENSE CILIM OSC VREF RAMP IREF-LIM BST MAX5033 CLK FB RAMP CONTROL LOGIC Rh x1 Rl TYPE 3 COMPENSATION VREF THERMAL SHUTDOWN CPWM EAMP GND LX SGND 8 _______________________________________________________________________________________ 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter The MAX5033 step-down DC-DC converter operates from a 7.5V to 76V input voltage range. A unique voltage-mode control scheme with voltage feed-forward and an internal switching DMOS FET provides high efficiency over a wide input voltage range. This pulsewidth modulated converter operates at a fixed 125kHz switching frequency. The device also features automatic pulse-skipping mode to provide low quiescent current and high efficiency at light loads. Under no load, the MAX5033 consumes only 270µA, and in shutdown mode, consumes only 10µA. The MAX5033 also features undervoltage lockout, hiccup-mode output shortcircuit protection, and thermal shutdown. Shutdown Mode Drive ON/OFF to ground to shut down the MAX5033. Shutdown forces the internal power MOSFET off, turns off all internal circuitry, and reduces the VIN supply current to 10µA (typ). The ON/OFF rising threshold is 1.69V (typ). Before any operation begins, the voltage at ON/OFF must exceed 1.69V (typ). The ON/OFF input has 100mV hysteresis. Undervoltage Lockout (UVLO) Use the ON/OFF function to program the UVLO threshold at the input. Connect a resistive voltage-divider from VIN to GND with the center node to ON/OFF as shown in Figure 1. Calculate the threshold value by using the following formula: On startup, an internal low-side switch connects LX to ground and charges the BST capacitor to VD. Once the BST capacitor is charged, the internal low-side switch is turned off and the BST capacitor voltage provides the necessary enhancement voltage to turn on the high-side switch. Thermal-Overload Protection The MAX5033 features integrated thermal-overload protection. Thermal-overload protection limits total power dissipation in the device, and protects the device in the event of a fault condition. When the die temperature exceeds +160°C, an internal thermal sensor signals the shutdown logic, turning off the internal power MOSFET and allowing the IC to cool. The thermal sensor turns the internal power MOSFET back on after the IC’s die temperature cools down to +140°C, resulting in a pulsed output under continuous thermaloverload conditions. Applications Information Setting the Output Voltage The MAX5033A/B/C have preset output voltages of 3.3V, 5.0V, and 12V, respectively. Connect FB to the preset output voltage (see the Typical Operating Circuit). The MAX5033D offers an adjustable output voltage. Set the output voltage with a resistive voltage-divider connected from the circuit’s output to ground (Figure 1). Connect the center node of the divider to FB. Choose R4 less than 15kΩ, then calculate R3 as follows: R1 VUVLO(TH) = 1 + × 1.85V R2 The minimum recommended VUVLO(TH) is 6.5V, 7.5V, and 13V for the output voltages of 3.3V, 5V, and 12V, respectively. The recommended value for R2 is less than 1MΩ. If the external UVLO threshold-setting divider is not used, an internal undervoltage-lockout feature monitors the supply voltage at VIN and allows operation to start when VIN rises above 5.2V (typ). This feature can be used only when VIN rise time is faster than 2ms. For slower VIN rise time, use the resistive divider at ON/OFF. R3 = (VOUT − 1.22) × R4 1.22 VIN 7.5V TO 76V 47µF R1 220µH VIN LX ON/OFF BST 0.1µF R2 COUT 33µF R3 41.2kΩ MAX5033D Boost High-Side Gate Drive (BST) Connect a flying bootstrap capacitor between LX and BST to provide the gate-drive voltage to the high-side n-channel DMOS switch. The capacitor is alternately charged from the internally regulated output-voltage VD and placed across the high-side DMOS driver. Use a 0.1µF, 16V ceramic capacitor located as close to the device as possible. D1 50SQ100 VOUT 5V, 0.5A FB VD SGND GND 0.1µF R4 13.3kΩ Figure 1. Adjustable Output Voltage _______________________________________________________________________________________ 9 MAX5033 Detailed Description MAX5033 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter The MAX5033 features internal compensation for optimum closed-loop bandwidth and phase margin. With the preset compensation, it is strongly advised to sense the output immediately after the primary LC. Inductor Selection The choice of an inductor is guided by the voltage difference between VIN and VOUT, the required output current, and the operating frequency of the circuit. Use an inductor with a minimum value given by: L= (VIN − VOUT ) × D 0.3 × IOUTMAX × fSW where: D = VOUT/VIN, IOUTMAX is the maximum output current required, and fSW is the operating frequency of 125kHz. Use an inductor with a maximum saturation current rating equal to at least the peak switch current limit (ILIM). Use inductors with low DC resistance for higher efficiency. Selecting a Rectifier The MAX5033 requires an external Schottky rectifier as a freewheeling diode. Connect this rectifier close to the device using short leads and short PC board traces. Choose a rectifier with a continuous current rating greater than the highest expected output current. Use a rectifier with a voltage rating greater than the maximum expected input voltage, VIN. Use a low forward-voltage Schottky rectifier for proper operation and high efficiency. Avoid higher than necessary reverse-voltage Schottky rectifiers that have higher forward-voltage drops. Use a Schottky rectifier with forward-voltage drop (VFB) less than 0.45V at +25°C and maximum Table 1. Diode Selection VIN (V) 7.5 to 36 7.5 to 56 7.5 to 76 10 DIODE PART NUMBER MANUFACTURER 15MQ040N IR B240A Diodes, Inc. B240 Central Semiconductor MBRS240, MBRS1540 ON Semiconductor 30BQ060 IR B360A Diodes, Inc. CMSH3-60 Central Semiconductor MBRD360, MBR3060 ON Semiconductor 50SQ100, 50SQ80 IR MBRM5100 Diodes, Inc. load current to avoid forward biasing of the internal body diode (LX to ground). Internal body-diode conduction may cause excessive junction temperature rise and thermal shutdown. Use Table 1 to choose the proper rectifier at different input voltages and output current. Input Bypass Capacitor 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 MAX5033 high switching frequency allows the use of smaller-value input capacitors. The input ripple is comprised of ∆VQ (caused by the capacitor discharge) and ∆VESR (caused by the ESR of the capacitor). Use low-ESR aluminum electrolytic capacitors with high ripple-current capability at the input. Assuming that the contribution from the ESR and capacitor discharge is equal to 90% and 10%, respectively, calculate the input capacitance and the ESR required for a specified ripple using the following equations: ESRIN = ∆VESR ∆IL IOUT + 2 I × D(1− D) CIN = OUT ∆VQ × fSW where ∆IL = (VIN − VOUT ) × VOUT VIN × fSW × L V D = OUT VIN IOUT is the maximum output current of the converter and fSW is the oscillator switching frequency (125kHz). For example, at VIN = 48V and VOUT = 3.3V, the ESR and input capacitance are calculated for the input peak-topeak ripple of 100mV or less, yielding an ESR and capacitance value of 130mΩ and 27µF, respectively. Low-ESR, ceramic, multilayer chip capacitors are recommended for size-optimized application. For ceramic capacitors, assume the contribution from ESR and capacitor discharge is equal to 10% and 90%, respectively. The input capacitor must handle the RMS ripple current without significant rise in temperature. The maximum capacitor RMS current occurs at about 50% duty cycle. ______________________________________________________________________________________ 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter ICRMS = capacitance and the ESR required for a specified ripple using the following equations: ESROUT = IPRMS2 − IAVGIN2 where COUT ≈ D IPRMS = IPK 2 + IDC2 + (IPK × IDC ) × 3 V ×I IAVGIN = OUT OUT VIN × η ∆I ∆I IPK = IOUT + L , IDC = IOUT − L 2 2 VOUT and D = VIN IPRMS is the input switch RMS current, IAVGIN is the input average current, and η is the converter efficiency. The ESR of aluminum electrolytic capacitors increases significantly at cold temperatures. Use a 1µF or greater value ceramic capacitor in parallel with the aluminum electrolytic input capacitor, especially for input voltages below 8V. Output Filter Capacitor The worst-case peak-to-peak and RMS capacitor ripple current, allowable peak-to-peak output ripple voltage, and the maximum deviation of the output voltage during load steps determine the capacitance and the ESR requirements for the output capacitors. The output capacitance and its ESR form a zero, which improves the closed-loop stability of the buck regulator. Choose the output capacitor so the ESR zero frequency (fZ) occurs between 20kHz to 40kHz. Use the following equation to verify the value of fZ. Capacitors with 100mΩ to 250mΩ ESR are recommended to ensure the closedloop stability while keeping the output ripple low. fZ = 1 2 × π × COUT × ESROUT The output ripple is comprised of ∆VOQ (caused by the capacitor discharge) and ∆VOESR (caused by the ESR of the capacitor). Use low-ESR tantalum or aluminum electrolytic capacitors at the output. Assuming that the contributions from the ESR and capacitor discharge equal 80% and 20%, respectively, calculate the output ∆VOESR ∆IL ∆IL 2.2 × ∆VOQ × fSW The MAX5033 has an internal soft-start time (tSS) of 400µs. It is important to keep the output rise time at startup below tSS to avoid output overshoot. The output rise time is directly proportional to the output capacitor. Use 68µF or lower capacitance at the output to control the overshoot below 5%. In a dynamic load application, the allowable deviation of the output voltage during the fast-transient load dictates the output capacitance value and the ESR. The output capacitors supply the step load current until the controller responds with a greater duty cycle. The response time (tRESPONSE) depends on the closedloop bandwidth of the converter. The resistive drop across the capacitor ESR and capacitor discharge cause a voltage droop during a step load. Use a combination of low-ESR tantalum and ceramic capacitors for better transient load and ripple/noise performance. Keep the maximum output-voltage deviation above the tolerable limits of the electronics being powered. Assuming a 50% contribution from the output capacitance discharge and the ESR drop, use the following equations to calculate the required ESR and capacitance value: ESROUT = ∆VOESR ISTEP I ×t COUT = STEP RESPONSE ∆VOQ where I STEP is the load step and t RESPONSE is the response time of the controller. Controller response time is approximately one-third of the reciprocal of the closed-loop unity-gain bandwidth, 20kHz (typ). PC Board Layout Considerations Proper PC board layout is essential. Minimize ground noise by connecting the anode of the Schottky rectifier, the input bypass-capacitor ground lead, and the output filter-capacitor ground lead to a single point (star- ______________________________________________________________________________________ 11 MAX5033 Ensure that the ripple specification of the input capacitor exceeds the worst-case capacitor RMS ripple current. Use the following equations to calculate the input capacitor RMS current: 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter MAX5033 Application Circuits VIN CIN VIN BST 0.1µF L1 VOUT LX D1 R1 MAX5033 COUT FB ON/OFF VD R2 SGND GND 0.1µF Figure 2. Fixed Output Voltages Table 2. Typical External Components Selection (Circuit of Figure 2) VIN (V) 7.5 to 76 7.5 to 76 15 to 76 VOUT (V) 3.3 5 12 IOUT (A) EXTERNAL COMPONENTS 0.5 CIN = 47µF, Panasonic, EEVFK2A470Q COUT = 47µF, Vishay Sprague, 594D476X_016C2T CBST = 0.1µF, 0805 R1 = 1MΩ ±1%, 0805 R2 = 384kΩ ±1%, 0805 D1 = 50SQ100, IR L1 = 150µH, Coilcraft Inc., DO5022P-154 0.5 CIN = 47µF, Panasonic, EEVFK2A470Q COUT = 33µF, Vishay Sprague, 594D336X_016C2T CBST = 0.1µF, 0805 R1 = 1MΩ ±1%, 0805 R2 = 384kΩ ±1%, 0805 D1 = 50SQ100, IR L1 = 220µH, Coilcraft Inc., DO5022P-224 0.5 CIN = 47µF, Panasonic, EEVFK2A470Q COUT = 15µF, Vishay Sprague, 594D156X_025C2T CBST = 0.1µF, 0805 R1 = 1MΩ ±1%, 0805 R2 = 384kΩ ±1%, 0805 D1 = 50SQ100, IR L1 = 330µH, Coilcraft Inc., DO5022P-334 ground configuration). A ground plane is required. Minimize lead lengths to reduce stray capacitance, trace resistance, and radiated noise. In particular, place the Schottky rectifier diode right next to the 12 device. Also, place BST and VD bypass capacitors very close to the device. Use the PC board copper plane connecting to VIN and LX for heatsinking. ______________________________________________________________________________________ 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter MAX5033 Table 2. Typical External Components Selection (Circuit of Figure 2) (continued) VIN (V) VOUT (V) 3.3 IOUT (A) EXTERNAL COMPONENTS 0.5 CIN = 100µF, Panasonic, EEVFK1E101P COUT = 47µF, Vishay Sprague, 594D476X_016C2T CBST = 0.1µF, 0805 R1 = 1MΩ ±1%, 0805 R2 = 274kΩ ±1%, 0805 D1 = B220/A, Diodes Inc. L1 = 150µH, Coilcraft Inc., DO5022P-154 0.5 CIN = 100µF, Panasonic, EEVFK1E101P COUT = 33µF, Vishay Sprague, 594D336X_016C2T CBST = 0.1µF, 0805 R1 = 1MΩ ±1%, 0805 R2 = 274kΩ ±1%, 0805 D1 = B220/A, Diodes Inc. L1 = 220µH, Coilcraft Inc., DO5022P-224 0.5 CIN = 100µF, Panasonic, EEVFK1H101P COUT = 47µF, Vishay Sprague, 594D476X_016C2T CBST = 0.1µF, 0805 R1 = 1MΩ ±1%, 0805 R2 = 130kΩ ±1%, 0805 D1 = B240/A, Diodes Inc. L1 = 150µH, Coilcraft Inc., DO5022P-154 0.5 CIN = 100µF, Panasonic, EEVFK1H101P COUT = 33µF, Vishay Sprague, 594D336X_016C2T CBST = 0.1µF, 0805 R1 = 1MΩ ±1%, 0805 R2 = 130kΩ ±1%, 0805 D1 = B240/A, Diodes Inc. L1 = 220µH, Coilcraft Inc., DO5022P-224 0.5 CIN = 100µF, Panasonic, EEVFK1H101P COUT = 15µF, Vishay Sprague, 594D156X_025C2T CBST = 0.1µF, 0805 R1 = 1MΩ ±1%, 0805 R2 = 130kΩ ±1%, 0805 D1 = B240/A, Diodes Inc. L1 = 330µH, Coilcraft Inc., DO5022P-334 9 to 14 5 3.3 18 to 36 5 12 ______________________________________________________________________________________ 13 MAX5033 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter Table 3. Component Suppliers PHONE FAX AVX SUPPLIER 843-946-0238 843-626-3123 www.avxcorp.com Coilcraft 847-639-6400 847-639-1469 www.coilcraft.com Diodes Incorporated 805-446-4800 805-446-4850 www.diodes.com Nichicon 858-824-1515 858-824-1525 www.nichicon.com Panasonic 714-373-7366 714-737-7323 www.panasonic.com Sanyo 619-661-6835 619-661-1055 www.sanyo.com TDK 847-803-6100 847-390-4405 www.component.tdk.com Vishay 402-563-6866 402-563-6296 www.vishay.com MAX5033 PTC* ON/OFF VIN 12V VIN CIN 47µF Ct Rt WEBSITE FB BST 0.1µF L1 220µH VOUT 5V AT 0.5A LX VD SGND GND 0.1µF D1 B240 COUT 33µF *LOCATE PTC AS CLOSE TO HEAT-DISSIPATING COMPONENTS AS POSSIBLE. Figure 3. Load Temperature Monitoring with ON/OFF (Requires Accurate VIN) 14 ______________________________________________________________________________________ 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter R1 VIN 7.5V TO 36V 0.1µF VIN CIN 47µF Ct FB BST ON/OFF L1 220µH VOUT 5V AT 0.5A LX VD Rt MAX5033 MAX5033B COUT 68µF D1 B240 SGND GND 0.1µF MAX5033A R1* BST ON/OFF 0.1µF VIN C'IN 68µF Ct' Rt' FB L1' 150µH V'OUT 3.3V AT 0.5A LX VD SGND GND C'OUT 68µF D1' B240 0.1µF Figure 4. Dual-Sequenced DC-DC Converters (Startup Delay Determined by R1/R1’, Ct/Ct’ and Rt/Rt’) Chip Information TRANSISTOR COUNT: 4344 PROCESS: BiCMOS ______________________________________________________________________________________ 15 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) DIM A A1 B C e E H L N E H INCHES MILLIMETERS MAX MIN 0.069 0.053 0.010 0.004 0.014 0.019 0.007 0.010 0.050 BSC 0.150 0.157 0.228 0.244 0.016 0.050 MAX MIN 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 1.27 BSC 3.80 4.00 5.80 6.20 0.40 SOICN .EPS MAX5033 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter 1.27 VARIATIONS: 1 INCHES TOP VIEW DIM D D D MIN 0.189 0.337 0.386 MAX 0.197 0.344 0.394 MILLIMETERS MIN 4.80 8.55 9.80 MAX 5.00 8.75 10.00 N MS012 8 AA 14 AB 16 AC D A B e C 0 -8 A1 L FRONT VIEW SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, .150" SOIC APPROVAL DOCUMENT CONTROL NO. 21-0041 16 ______________________________________________________________________________________ REV. B 1 1 500mA, 76V, High-Efficiency, MAXPower Step-Down DC-DC Converter PDIPN.EPS Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 17 © 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX5033 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)