MAX17760ATC+

Click here for production status of specific part numbers. MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter General Description Benefits and Features The Himalaya series of voltage regulator ICs, power modules, and chargers enable cooler, smaller, and simpler power supply solutions. The MAX17760 is a high-efficiency, high-voltage, Himalaya synchronous step-down DCDC converter with integrated MOSFETs operating over an input-voltage range of 4.5V to 76V. The device can deliver up to 300mA current. Output voltage is programmable from 0.8V up to 88% of input voltage (VIN). Built-in control loop compensation eliminates the need for external components. ● Reduces External Components and Total Cost • No Schottky—Synchronous Operation • Internal Compensation Components • All-Ceramic Capacitors, Compact Layout The MAX17760 features a peak-current-mode control architecture. The device can be operated in either the forced pulse-width modulation (PWM) or pulse-frequency modulation (PFM) control schemes. Forced PWM mode provides constant frequency operation at all loads for frequency sensitive applications, while PFM mode provides superior light-load efficiency by skipping pulses. The device integrates an open drain RESET output voltage monitor, adjustable input undervoltage lockout (EN/UVLO) and programmable soft-start. The feedback voltage regulation accuracy over -40°C to +125°C is +1.6% to -1.7%. The MAX17760 is available in a compact 12-pin (3mm x 3mm) TDFN package. Simulation models are available. Applications ● ● ● ● ● ● Industrial Control Power Supplies General Purpose Point-of-Load Distributed Supply Regulation Base Station Power Supplies Wall Transformer Regulation High Voltage Single-Board Systems VOUT VIN MA X17760 LX EN/UVLO SS RT/SYNC VCC 19-100795; Rev 0; 4/20 FB EXTVCC MODE SGND PGND EP RESET VOUT ● Reduces Power Dissipation • 93% Peak Efficiency • PFM Mode Enables Enhanced Light-Load Efficiency • EXTVCC Bootstrap Input for Improved Efficiency • 5μA Shutdown Current ● Operates Reliably in Adverse Industrial Environments • Built-in Hiccup Mode Overload Protection • Programmable Soft-Start and Prebiased Power-up • Built-in Output-Voltage Monitoring with RESET • Programmable EN/UVLO Threshold • Overtemperature Protection • CISPR 22 Class B Compliant • Wide -40°C to +125°C Ambient Operating Temperature Range/ -40°C to +150°C Junction Temperature Range Ordering Information appears at end of data sheet. Simplified Application Circuit VIN ● Reduces Number of DC-DC Regulators to Stock • Wide 4.5V to 76V Input • Adjustable Output Range from 0.8V up to 88% of VIN • Up to 300mA Output Current • 200kHz, 300kHz, 400kHz, and 600kHz Programmable Switching Frequency with External Clock Synchronization. MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Absolute Maximum Ratings VIN to SGND........................................................... -0.3V to +80V EN/UVLO to SGND ....................... -0.3 to min((VIN + 0.3V), 26V) EXTVCC to SGND.................................................. -0.3V to +26V LX to PGND .................................................... -0.3 to (VIN + 0.3V) FB, RESET, SS, MODE, VCC, RT/SYNC to SGND . -0.3V to +6V PGND to SGND ..................................................... -0.3V to +0.3V LX Total RMS Current ......................................................... ±0.6A Continuous Power Dissipation (Multilayer Board) (TA = +70°C, derate 24.4mW/°C above +70°C.) ...............................1951.2mW Output Short-Circuit Duration......................................Continuous Operating Temperature Range (Note 1) .............-40°C to +125°C Junction Temperature ....................................................... +150°C Storage Temperature Range ..............................-65°C to +150°C Lead Temperature (soldering, 10s)................................... +300°C Soldering Temperature (reflow) ........................................ +260°C Note 1: Junction temperature greater than +125°C degrades operating lifetimes. 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 Information 12 TDFN Package Code TD1233+1C Outline Number 21-0664 Land Pattern Number 90-0397 Thermal Resistance, Four-Layer Board: Junction to Ambient (θJA) 41°C/W Junction to Case (θJC) 8.5°C/W 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 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, EN/UVLO = unconnected, RRT/SYNC = 69.8kΩ (fSW = 400 kHz), VMODE = VPGND = VSGND = VEXTVCC = 0V, CVCC = 1μF, VFB = 1V, LX = SS = RESET = unconnected, TA = TJ = -40°C to 125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.) (Note 2 ) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 76 V 10 μA INPUT SUPPLY (VIN) Input Voltage Range Input Shutdown Current Input Quiescent Current VIN IIN-SH 4.5 VEN/UVLO = 0V (shutdown mode) 2.5 5 IQ_PFM MODE = Unconnected, VEXTVCC = 5V 75 μA IQ_PWM VFB = 0.75V, Normal switching mode 2.5 mA ENABLE/UVLO (EN/UVLO) EN/UVLO Threshold EN/UVLO Pullup Current www.maximintegrated.com VENR VEN/UVLO rising 1.19 1.215 1.24 VENF VEN/UVLO falling 1.09 1.115 1.14 V VENT VEN/UVLO falling, true shutdown 2.8 µA IEN/UVLO VEN/UVLO = 1.215V 19-100795 0.7 2.2 2.5 Maxim Integrated | 2 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Electrical Characteristics (continued) (VIN = 24V, EN/UVLO = unconnected, RRT/SYNC = 69.8kΩ (fSW = 400 kHz), VMODE = VPGND = VSGND = VEXTVCC = 0V, CVCC = 1μF, VFB = 1V, LX = SS = RESET = unconnected, TA = TJ = -40°C to 125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.) (Note 2 ) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 4.75 5 5.25 V 13 26 52 mA 0.27 V LINEAR REGULATOR (VCC) VCC Output Voltage Range VCC Current Limit VCC Dropout Voltage VCC UVLO VCC 6V ≤ VIN ≤ 76V, 0mA < IVCC < 5mA IVCC-MAX VCC = 4.3V, VIN = 12V VCC-DO VIN = 4.5V, IVCC = 5mA VCC-UVR VCC rising 4.05 4.2 4.35 VCC-UVF VCC falling 3.65 3.8 3.95 EXTVCC Operating Voltage Range 4.85 VEXTVCC rising EXTVCC Switchover Threshold EXTVCC Dropout Voltage EXTVCC Current Limit 4.65 Hysteresis EXTVCC-DO 24 4.74 4.85 0.3 VEXTVCC = 4.75V, IVCC = 5mA 13 V V V 0.1 V 21 34 mA IVCC-MAX VCC = 4.3V, VEXTVCC = 5V High-Side pMOS OnResistance RDS-ONH ILX = 0.15A, sourcing 1.8 3.6 Ω Low-Side nMOS OnResistance RDS-ONL ILX = 0.15A, sinking 0.55 1.1 Ω LX Leakage Current ILX-LKG +1 μA μA POWER MOSFETS VLX = (VPGND + 1V) to (VIN - 1V), TA = +25°C -1 SOFT-START (SS) Charging Current ISS 4.7 5 5.3 VMODE = 0V (PWM mode) 0.788 0.802 0.815 MODE = Unconnected (PFM mode) 0.788 0.813 0.827 TA = +25°C -100 FEEDBACK (FB) FB Regulation Voltage FB Input Leakage Current VFB-REG IFB V +100 nA mA CURRENT LIMIT Peak Current Limit Threshold IPEAK-LIMIT Negative Current Limit Threshold ISINK-LIMIT PFM Current Limit IPFM VMODE = 0V (PWM mode) 532 640 755 238 270 302 MODE = Unconnected (PFM mode) MODE = Unconnected 2.5 185 240 310 1 1.22 1.44 mA mA MODE PFM Mode Threshold VTH_PFM Rising Hysteresis 0.175 MODE Pullup Current at Power-Up www.maximintegrated.com 2.5 19-100795 V μA Maxim Integrated | 3 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Electrical Characteristics (continued) (VIN = 24V, EN/UVLO = unconnected, RRT/SYNC = 69.8kΩ (fSW = 400 kHz), VMODE = VPGND = VSGND = VEXTVCC = 0V, CVCC = 1μF, VFB = 1V, LX = SS = RESET = unconnected, TA = TJ = -40°C to 125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.) (Note 2 ) PARAMETER SYMBOL CONDITIONS MIN TYP MAX RRT/SYNC = 140kΩ 180 200 220 RRT/SYNC = 93.1kΩ 270 300 330 RRT/SYNC = 69.8kΩ 360 400 440 RRT/SYNC = 46.4kΩ 540 600 660 UNITS OSCILLATOR (RT/SYNC) Switching Frequency fSW Switching Frequency Adjustable Range Minimum On-Time Maximum Duty Cycle Hiccup Timeout Period 200 tON-MIN DMAX 88 tHIC-TOUT SYNC Threshold 600 kHz 70 110 ns 93 97 % 51 SYNC Frequency Capture Range 1.15 x fSW (typ) VIH kHz ms 1.4 x fSW (typ) 2.1 VIL 0.8 V RESET RESET Output Level Low IRESET = 10mA RESET Output Leakage Current TA = +25°C 0.4 V 1 µA FB Threshold for RESET Deassertion VFB-OKR VFB rising 95 % FB Threshold for RESET Assertion VFB-OKF VFB falling 92 % 2.1 ms RESET Delay after FB Reaches 95% Regulation THERMAL SHUTDOWN Thermal Shutdown Threshold Temperature rising 160 Hysteresis 20 °C Note 2: Electrical specifications are production tested at TA = +25ºC. Specifications over the entire operating temperature range are guaranteed by design and characterization. www.maximintegrated.com 19-100795 Maxim Integrated | 4 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (VIN = 24V, VSGND = VPGND = 0V, CVCC = 1μF, EN/UVLO = unconnected, CSS = 5600pF, TA = +25°C, unless otherwise noted. All voltages are referenced to SGND, unless otherwise noted.) www.maximintegrated.com 19-100795 Maxim Integrated | 5 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) (VIN = 24V, VSGND = VPGND = 0V, CVCC = 1μF, EN/UVLO = unconnected, CSS = 5600pF, TA = +25°C, unless otherwise noted. All voltages are referenced to SGND, unless otherwise noted.) www.maximintegrated.com 19-100795 Maxim Integrated | 6 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) (VIN = 24V, VSGND = VPGND = 0V, CVCC = 1μF, EN/UVLO = unconnected, CSS = 5600pF, TA = +25°C, unless otherwise noted. All voltages are referenced to SGND, unless otherwise noted.) www.maximintegrated.com 19-100795 Maxim Integrated | 7 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) (VIN = 24V, VSGND = VPGND = 0V, CVCC = 1μF, EN/UVLO = unconnected, CSS = 5600pF, TA = +25°C, unless otherwise noted. All voltages are referenced to SGND, unless otherwise noted.) www.maximintegrated.com 19-100795 Maxim Integrated | 8 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Pin Configuration TOP VIEW 1 PGND 2 VCC 3 EN/UVLO 4 RESET 5 RT/SYNC 6 + VIN 12 LX 11 SGND 10 MODE MA MAX X17760 EP 9 SS 8 FB 7 EXTVCC TDFN (3mm x 3mm 3mm)) Pin Description PIN NAME FUNCTION 1 VIN Power Supply Input Pin. 4.5V to 76V input-supply range. Decouple to PGND with a 1μF capacitor. Place the capacitor close to the VIN and PGND pins. 2 PGND 3 VCC 4 EN/UVLO 5 RESET Open-Drain RESET Output. The RESET output is driven low when FB drops below 92% of its set value. RESET goes high 2.1ms after FB rises above 95% of its set value. 6 RT/SYNC Programmable Switching Frequency and External Clock Synchronization Input. Connect a resistor from RT/SYNC to SGND to set the converter's switching frequency between 200kHz and 600kHz. An external clock can be connected to the RT/SYNC to synchronize the device with an external clock in PWM mode. See the Switching Frequency Selection and External Clock Synchronization (RT/SYNC) section for more details. 7 EXTVCC External Power Supply Input for the EXT-LDO. Connect EXTVCC to the buck converter output for an output voltage between 5V and 24V. When EXTVCC is not used, connect it to SGND. See the Linear Regulator (VCC and EXTVCC) section for more details. 8 FB Feedback Input. Connect FB to the center node of an external resistor-divider from the output to SGND to set the output voltage. See the Adjusting Output Voltage section for more details. 9 SS Soft-Start Input. Connect a capacitor from SS to SGND to set the soft-start time. 10 MODE MODE Selection. The MODE pin configures the device to operate either in PWM or PFM mode of operation. Leave MODE unconnected for PFM operation. Connect MODE to SGND for constantfrequency PWM operation at all loads. 11 SGND Signal Ground. 12 LX Switching Node. Connect LX pin to the switching-side of the inductor. — EP Exposed Pad. Connect EP to SGND. Refer to the MAX17760 EV kit data sheet for the recommended method of PCB layout, routing, and thermal vias. www.maximintegrated.com Power Ground. Refer to the MAX17760 EV kit data sheet for the recommended PCB layout and routing. 5V LDO Output. Bypass VCC with a 1μF ceramic capacitor to PGND. LDO doesn't support external loading on VCC. Enable/Undervoltage Lockout Pin. Drive EN/UVLO high to enable the output. Connect to the center of a resistor-divider between VIN and SGND to set the input voltage at which the device turns on. Leave the pin unconnected for always-on operation. 19-100795 Maxim Integrated | 9 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Functional Block Diagram M A X 17760 EXTVCC EXT-LDO VIN INT-LDO VCC BIAS SELECT VIN POK 2.5μA EN/UVLO PEAK-LIMIT CHIPEN CURRENTSENSE LOGIC 1.215V CS CURRENTSENSE AMPLIFIER PFM THERMAL SHUTDOWN DH CLK RT/SYNC OSCILLATOR SLOPE VCC HIGH-SIDE DRIVER LX PFM/PWM CONTROL LOGIC DL LOW-SIDE DRIVER 2.5μA *S1 PGND MODE MODE SELECT *S2 1.22V CS FB SS EXTERNAL SOFT-START CONTROL ISINK-LIMIT SLOPE 20kΩ ++ NEGATIVE CURRENT LIMIT RESET PWM ERROR AMPLIFIER CHIPEN 0.76V RESET LOGIC FB CLK www.maximintegrated.com *S1 – CLOSE, S2 – OPEN when CHIPEN = 0 *S1 – OPEN, S2 – CLOSE when CHIPEN = 1 19-100795 Maxim Integrated | 10 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Detailed Description The MAX17760 is a high-efficiency, high voltage, synchronous step-down DC-DC converter with integrated MOSFETs operating over an input-voltage range of 4.5V to 76V. The device can deliver up to 300mA current. Output voltage is programmable from 0.8V up to 88% of VIN. Built-in control loop compensation eliminates the need for external components. The feedback-voltage regulation accuracy over -40°C to +125°C is +1.6% to -1.7%. 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 high-side currentsense amplifier, and a slope-compensation generator. At each rising edge of the clock, the high-side 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 on-time, the inductor current ramps up. During the rest of the switching cycle, the highside 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. The internal low RDSON pMOS/nMOS switches ensure high efficiency at full load. The MAX17760 features a MODE pin that can be used to program the device in PWM or PFM control schemes. The device also features adjustable-input undervoltage lockout (EN/UVLO), adjustable soft-start (SS), open-drain RESET, and external clock synchronization (RT/SYNC) features. The MAX17760 offers a low minimum on-time that allows to operate for a wide range of input supply at a given switching frequency. Mode Selection The MAX17760 supports PWM and PFM mode of operation. The device detects the MODE pin status at power-up and latches the MODE of operation. Leave the MODE pin unconnected for PFM operation. At power-up the MAX17760 pullup the MODE pin with a 2.5μA current. If the MODE pin exceeds the PFM mode threshold (VTH_PFM), the part latches PFM mode and pulls down MODE with a 20kΩ internal resistor. Connect MODE to SGND for constant-frequency forced PWM operation at all loads. The mode of operation cannot be changed on-the-fly after power-up. In PWM mode, the inductor current is allowed to go negative. PWM operation provides constant frequency operation irrespective of loading, and is useful in applications sensitive to switching frequency. PFM mode provides high efficiency at light load conditions by disabling negative inductor current and additionally skipping pulses. In PFM mode, the inductor current is forced to a fixed peak of IPFM (240mA typ) every clock cycle until the output rises to 102.3% of the set nominal output voltage. Once the output reaches 102.3% of the set nominal output voltage, both the high-side and low-side FETs are turned off and the device enters hibernation until the load discharges the output to 101.1% of the set nominal output voltage. Most of the internal blocks are turned off in hibernate operation to reduce quiescent current. After the output falls below 101.1% of the set nominal output voltage, the device comes out of hibernate operation, 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 set nominal output voltage. The advantage of PFM mode is higher efficiency at light loads because of lower quiescent current drawn from supply. However, the output voltage ripple is higher compared to PWM mode of operation and switching frequency is not constant at light loads. www.maximintegrated.com 19-100795 Maxim Integrated | 11 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Linear Regulator (VCC and EXTVCC) The MAX17760 integrates two internal low-dropout (LDO) linear regulators INT-LDO and EXT-LDO that power VCC. INTLDO is powered from VIN and turns on when VEN/UVLO > VENT (0.7V typ). EXT-LDO is powered from EXTVCC. At any time, only one of these two linear regulators operates, depending on the EXTVCC voltage. If EXTVCC is greater than 4.74V (typ), VCC is powered from the EXTVCC. If EXTVCC is lower than 4.44V (typ), VCC is powered from VIN. Powering VCC from EXTVCC increases efficiency at higher input voltages. Typical VCC output voltage is 5V. Bypass VCC to SGND with a 1µF low-ESR ceramic capacitor. VCC powers the internal blocks and both low-side and high-side MOSFET drivers. The MAX17760 employs an undervoltage-lockout circuit that forces the converter off when VCC voltage falls below VCCUVF (3.8V typ). The buck converter enables when the VCC voltage rises above VCC-UVR (4.2 typ). EXTVCC should be connected to the output capacitor with an R-C filter as shown in Figure 4. Without this R-C filter, the absolute maximum rating of EXTVCC (-0.3V) can be exceeded under short-circuit conditions, due to oscillations between the ceramic output capacitor and the inductance of the short-circuit path. In general, parasitic board or wiring inductance should be minimized and the output voltage under short-circuit operation should be verified to ensure that the absolute maximum rating of EXTVCC is not exceeded. Switching Frequency Selection and External Clock Synchronization (RT/SYNC) The MAX17760 can be programmed to one of the four discrete switching frequencies 200KHz, 300kHz, 400kHz, and 600kHz, by connecting a resistor from RT/SYNC to SGND. Table 1 provides resistor values for different switching frequencies. The MAX17760 can be synchronized to an external clock coupled to the RT/SYNC pin through a 22pF capacitor as shown in Figure 1. The external clock must be applied after RESET is asserted high for proper configuration of the internal loop compensation. If the external clock frequency is within the allowed SYNC frequency range (1.15 to 1.4 times the nominal internal clock frequency fSW), the internal clock synchronizes to the external clock within 1 clock cycle. The allowed external clock duty cycle range is 10% to 80%. Table 1. Switching Frequency vs. RT/SYNC Resistor SWITCHING FREQUENCY (kHz) RRT/SYNC (kΩ) 200 140 300 93.1 400 69.8 600 46.4 22pF RT/SYNC EXTERNAL CLOCK SOURCE RRT/SYNC M A X 17760 SGND Figure 1. External Clock Synchronization www.maximintegrated.com 19-100795 Maxim Integrated | 12 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Operating Input Voltage Range The minimum and maximum operating input voltages for a given output-voltage setting should be calculated as follows: VIN(MIN) = ( ( VOUT + IOUT MAX × RDCR(MAX) + RDS-ONL(MAX) ( ) DMAX )) + (I OUT(MAX) × (RDS-ONH(MAX)-RDS-ONL(MAX))) VOUT VIN(MAX) = f SW(MAX) × tON-MIN(MAX) where: VOUT = Steady-state output voltage IOUT(MAX) = Maximum load current RDCR(MAX) = Worst-case DC resistance of the inductor fSW(MAX) = Maximum switching frequency DMAX = Minimum specification of maximum duty ratio (0.88) tON-MIN(MAX) = Worst-case minimum switch on-time (110 ns) RDS-ONL(MAX) and RDS-ONH(MAX) = Worst-case on-state resistances of low-side and high-side internal MOSFETs, respectively. Overcurrent Protection/Hiccup Mode The device features a hysteretic peak current-limit protection scheme to protect the internal FETs and inductor under output short-circuit conditions. When the inductor peak current exceeds IPEAK-LIMIT, the high-side switch is turned off and the low-side switch is turned on. After the current is reduced to 290mA (typ), the high-side switch is turned on at the rising edge of the next clock pulse. The device enters a hiccup timeout period tHIC_TOUT (51ms typ) if 16 consecutive peak current limit events are detected. After the hiccup time-out period has elapsed, the device restarts. If the overcurrent condition persists, the device remains in hiccup current limit mode until the overcurrent fault is removed. RESET Output The device features a RESET comparator to monitor the output voltage. The open-drain RESET output requires an external pullup resistor. RESET goes high 2.1ms 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 the low-side switches are turned off so that the converter does not sink current from the output. High-side 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. Thermal-Shutdown Protection Thermal shutdown protection limits junction temperature of the device. When the junction temperature of the device exceeds +160°C, an on-chip thermal sensor shuts down the device, allowing the device to cool. The thermal sensor turns the device on with soft-start after the junction temperature cools by 20°C. Carefully evaluate the total power dissipation (see the Power Dissipation section) to avoid unwanted triggering of the thermal shutdown protection in normal operation. www.maximintegrated.com 19-100795 Maxim Integrated | 13 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter 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 switching. The input capacitor RMS current requirement (IRMS) is defined by the following equation: IRMS= IOUT(MAX)× √VOUT × (VIN − VOUT) VIN 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 +10°C temperature rise at the RMS input current for optimal longterm 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: CIN = ( IOUT MAX × D × 1 − D ( ) η × fSW × ∆ VIN ) where: D = VOUT/VIN and is the duty ratio of the controller fSW = Switching frequency ΔVIN = Allowable input-voltage ripple η = Efficiency In applications where the source is located distant from the device input, an appropriate 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. Inductor Selection 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 and output voltage determine the inductor value as follows: L= 4 × VOUT fSW where VOUT = Output voltage fSW = Switching frequency 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. www.maximintegrated.com 19-100795 Maxim Integrated | 14 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Output Capacitor Selection X7R ceramic output capacitors are preferred due to their stability over temperature in industrial applications. The output capacitors are 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. The minimum required output capacitance can be calculated as follows: 1 COUT = 2 × ISTEP × tRESPONSE ∆ VOUT 0.35 tRESPONSE ≅ f C where: ISTEP = Load current step tRESPONSE = Response time of the controller ΔVOUT = Allowable output-voltage deviation fC = Target closed-loop crossover frequency fSW = Switching frequency. Select fC to be the minimum of 1/10th of fSW and 30kHz. Actual derating of ceramic capacitors with DC-bias voltage must be considered while selecting the output capacitor. Derating curves are available from all major ceramic capacitor manufacturers. 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: CSS ≥ 30 × 10 − 6 × CSEL × VOUT The soft-start time (tSS) is related to the capacitor connected at SS (CSS) by the following equation: tSS = CSS 6.25 × 10 − 6 For example, to program a 0.9ms soft-start time, a 5.6nF capacitor should be connected from the SS pin to SGND. Note that, during startup, the device operates at half the programmed switching frequency until the output voltage reaches 80% of set output nominal voltage. www.maximintegrated.com 19-100795 Maxim Integrated | 15 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Setting the Input Undervoltage-Lockout Level Drive EN/UVLO high to enable the output. Leave the pin unconnected for always-on operation. Set the voltage at which each converter turns on with a resistive voltage-divider connected from VIN to SGND (see Figure 2). Connect the center node of the divider to EN/UVLO pin. Choose R1 as follows: R1 ≤ (110000 × VINU) where VINU is the input voltage at which the MAX17760 is required to turn on and R1 is in Ω. Calculate the value of R2 as follows: R2 = R1 × 1.215 (VINU − 1.215 + (2.5μ × R1)) VIN R1 EN/UVLO R2 SGND Figure 2. Setting the Input Undervoltage Lockout Level www.maximintegrated.com 19-100795 Maxim Integrated | 16 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Adjusting Output Voltage Set the output voltage with a resistive voltage-divider connected from the output voltage node (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: R3 = 15 × VOUT 0.8 where R3 is in kΩ. Calculate resistor R4 from the FB pin to SGND as follows: R4 = R3 × 0.8 (VOUT- 0.8) R4 is in kΩ. VOUT R3 FB R4 SGND Figure 3. Adjusting Output Voltage Power Dissipation At a particular operating condition, the power losses that lead to a temperature rise of the device are estimated as follows: ( ( 1 )) ( PLOSS = POUT × η − 1 − IOUT2 × RDCR POUT = VOUT × IOUT ) where: POUT = Output power η = Efficiency of the converter RDCR = DC resistance of the inductor (see the Typical Operating Characteristics for more information on efficiency at typical operating conditions). For a typical multilayer board, the thermal performance metrics for the package are given below: θJA = 41ºC/W θJC = 8.5ºC/W The junction temperature of the device can be estimated at any given maximum ambient temperature (TA(MAX)) from the following equation: TJ(MAX) = TA(MAX) + (θJA × PLOSS) www.maximintegrated.com 19-100795 Maxim Integrated | 17 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter 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: TJ(MAX) = TEP(MAX) + (θJC × PLOSS) Note: Junction temperatures greater than +125°C 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 currentcarrying 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. 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 minimum. 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 throughputs that connect to a large ground plane should be provided under the exposed pad of the device for efficient heat dissipation. For a sample layout that ensures first pass success, refer to the MAX17760 EV Kit layout available at www.maximintegrated.com. Typical Application Circuits VIN (7V TO 76V) C1 1μF LX EN/UVLO SS 56μH PGND M A X 17760 R5 69.8kΩ C2 1μF VCC C5 0.1μF MODE EP R3 95.3kΩ VOUT R6 EXTVCC SGND C4 10μF FB RT/SYNC C3 5600pF VOUT 5V, 300mA L1 VIN 22Ω R4 18.2kΩ fSW = 400kHz: L1 = 56µH/4.8mm x 4.8mm, 0.7A (WURTH 74408943560) C1 = 1µF/100V/X7R/1206 (TDK C3216X7R2A105K160AA) C4 = 10µF/16V/X7R/0805 (MURATA GRM21BZ71C106KE15) MODE: 1. CONNECT TO SGND FOR PWM MODE 2. LEAVE UNCONNECTED FOR PFM MODE RESET Figure 4. 5V Output with 400kHz Switching Frequency www.maximintegrated.com 19-100795 Maxim Integrated | 18 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Application Circuits (continued) VIN (5V TO 76V) C1 1μF VOUT 3.3V, 300mA L1 VIN LX EN/UVLO SS 33μH PGND M A X 17760 C4 22μF R3 59.0kΩ FB RT/SYNC C3 5600pF R5 69.8kΩ C2 1μF EXTVCC R4 18.7kΩ VCC fSW = 400kHz: L1 = 33µH/4.8mm x 4.8mm, 0.9A (WURTH 74408943330) C1 = 1µF/100V/X7R/1206 (TDK C3216X7R2A105K160AA) C4 = 22µF/6.3V/X7R/0805 (MURATA GRM21BZ70J226ME44) MODE: 1. CONNECT TO SGND FOR PWM MODE 2. LEAVE UNCONNECTED FOR PFM MODE MODE EP SGND RESET Figure 5. 3.3V Output with 400kHz Switching Frequency VIN (16V TO 76V) C1 1μF LX EN/UVLO SS 100μH PGND M A X 17760 R5 69.8kΩ C2 1μF VCC C5 0.1μF MODE EP R3 226kΩ VOUT R6 EXTVCC SGND C4 4.7μF FB RT/SYNC C3 5600pF VOUT 12V, 300mA L1 VIN 22Ω R4 16.2kΩ fSW = 400kHz: L1 = 100µH/4.8mm x 4.8mm, 0.52A (WURTH 74408943101) C1 = 1µF/100V/X7R/1206 (TDK C3216X7R2A105K160AA) C4 = 4.7µF/35V/X7R/1206 (TDK C3216X7R1V475K160AB) MODE: 1. CONNECT TO SGND FOR PWM MODE 2. LEAVE UNCONNECTED FOR PFM MODE RESET Figure 6. 12V Output with 400kHz Switching Frequency www.maximintegrated.com 19-100795 Maxim Integrated | 19 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Ordering Information TEMP. RANGE PIN-PACKAGE MAX17760ATC+ PART NUMBER -40°C to +125°C 12 TDFN - EP* (3mm x 3mm) MAX17760ATC+T -40°C to +125°C 12 TDFN - EP* (3mm x 3mm) +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. T = Tape and reel. www.maximintegrated.com 19-100795 Maxim Integrated | 20 MAX17760 4.5V to 76V, 300mA, High-Efficiency, Synchronous Step-Down DC-DC Converter Revision History REVISION NUMBER REVISION DATE 0 4/20 DESCRIPTION Initial release PAGES CHANGED — For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html. 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. 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