MAX17578ATC+

Click here to ask about the production status of specific part numbers. MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters 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 MAX17577 and MAX17578 are high-efficiency, high-voltage, inverting, Himalaya synchronous DC-DC converters with integrated MOSFETs and internal compensation. The devices generate output voltages (VOUT) from -0.9V to -36V and can deliver up to 1A of load current from a wide 4.5V to (60V - |VOUT|) input-voltage range. ● Reduces External Components and Total Cost • Synchronous Operation • All-Ceramic Capacitors, Compact Layout • Internal Loop Compensation • System Ground Referenced I/O Pins (EN/UVLO, RESET) The devices feature peak current-mode control architecture. The MAX17577 operates in continuous conduction mode (CCM) at all loads; thus, providing a constant frequency operation. The MAX17578 operates in discontinuous conduction mode (DCM) for superior efficiency at light loads. Low minimum on-time allows higher switching frequencies and small solution sizes. The devices allow the EN/UVLO, RESET, and RT/SYNC pins to be driven by signals that are referenced to system ground, eliminating the need for external-level shifter circuits. The feedback-voltage regulation accuracy is ±1.3% over a wide -40°C to +125°C temperature range. The devices are available in a compact 12-pin (3mm x 3mm) TDFN package. Simulation models are available. Applications ● ● ● ● ● ● Industrial Control Power Supply General-Purpose Point-of-Load Gate-Drive Circuits Motion Control Wall-Transformer Regulation High-Voltage, Single-Board System ● Flexibility to Support Multiple Rails in a System • Adjustable Output Voltage Range from -0.9V to -36V • Wide 4.5V to (60V - |VOUT|) Input-Voltage Range • Up to 1A Output Current • 400kHz to 2.2MHz Adjustable Frequency with External Clock Synchronization ● Reduces Power Dissipation • 90.6% Peak Efficiency • DCM for Superior Light-Load Efficiency • 6.2μA Shutdown Current ● Operates Reliably in Adverse Industrial Environments • Hiccup-Mode Overload Protection • Adjustable Soft-Start • Monotonic Startup with Prebiased Output Voltage • Built-In Output-Voltage Monitoring with RESET • Programmable EN/UVLO Threshold • Overtemperature Protection • 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 IN RESET EN/UVLO BST MAX17577/ MAX17578 RT/SYNC LX VCC FB SS GND SOUT EP FB FB OUT VOUT 19-100840; Rev 0; 10/20 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Absolute Maximum Ratings IN, GND, EN/UVLO to OUT.................................... -0.3V to +65V IN to GND ............................................................... -0.3V to +65V EN/UVLO to GND...........................................-0.3V to VIN + 0.3V RESET to GND...................................................... -0.3V to +6.5V LX to OUT ................................................... -0.3V to (VIN + 0.3V) RESET, BST to OUT .............................................. -0.3V to +70V BST to LX .............................................................. -0.3V to +6.5V BST to VCC............................................................. -0.3V to +65V FB, SS, VCC to SOUT ........................................... -0.3V to +6.5V RT/SYNC to SOUT................................................... -2V to +6.5V OUT to SOUT ........................................................ -0.3V to +0.3V LX Total RMS Current............................................................1.6A Output Short-Circuit Duration......................................Continuous Continuous Power Dissipation (Multilayer Board) (TA = +70°C, derate 24.4mW/°C above +70°C) ................................1951.2mW 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 TDFN Package Code TD1233+1C Outline Number 21-0664 Land Pattern Number 90-0397 THERMAL RESISTANCE, FOUR-LAYER BOARD (Note 2) Junction-to-Ambient (θJA) 33ºC/W Junction-to-Case Thermal Resistance (θJC) 8.5ºC/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. Note 2: Package thermal resistance was obtained using the MAX17578 evaluation kit with no airflow Electrical Characteristics (VIN = VEN/UVLO = 24V, CVCC = 2.2μF, VFB = 1V, RT/SYNC = LX = SS = RESET = Open, VBST to VLX = 5V, VGND = VSOUT = VOUT = 0V, TA = -40°C to +125°C. Typical values are at TA = +25°C. All voltages are referenced to SOUT, unless otherwise noted.) (Note 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 60 |VOUT| V 10 μA INPUT SUPPLY (IN) Input-Voltage Range Input-Shutdown Current No-Load Input Current VIN_GND IIN-SH INO_LOAD (Referred to GND) 4.5 VEN/UVLO = 0V (referred to GND), shutdown mode 6.2 MAX17577, Normal Switching Mode 6.3 MAX17578 1.5 2 mA ENABLE/UNDERVOLTAGE LOCKOUT (EN/UVLO) EN/UVLO Threshold EN/UVLO InputLeakage Current www.maximintegrated.com VENR VEN/UVLO rising (referred to GND) 1.165 1.229 1.275 VENF VEN/UVLO falling (referred to GND) 1.04 1.09 1.14 VEN/UVLO = GND, TA = +25°C -50 0 +50 IENLKG V nA Maxim Integrated | 2 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Electrical Characteristics (continued) (VIN = VEN/UVLO = 24V, CVCC = 2.2μF, VFB = 1V, RT/SYNC = LX = SS = RESET = Open, VBST to VLX = 5V, VGND = VSOUT = VOUT = 0V, TA = -40°C to +125°C. Typical values are at TA = +25°C. All voltages are referenced to SOUT, unless otherwise noted.) (Note 3) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 1mA < IVCC < 15mA 4.75 5 5.25 6V ≤ VIN ≤ 60V; IVCC = 1mA 4.75 5 5.25 25 60 UNITS LDO (VCC) VCC Output Voltage VCC Current Limit VCC Dropout VCC UVLO VCC IVCC_MAX VCC = 4.3V, VIN = 6.5V VCC_DO VIN = 4.5V, IVCC=15mA VCC_UVR VCC rising 4.05 4.2 4.3 VCC_UVF VCC falling 3.65 3.8 3.9 V 100 mA 0.35 V V HIGH-SIDE AND LOW-SIDE MOSFETS High-Side nMOSFET On-Resistance RDS-ONH ILX = 0.3A, Sourcing 330 660 mΩ Low-Side nMOSFET On-Resistance RDS-ONL ILX = 0.3A,Sinking 163 325 mΩ LX Leakage Current ILXLKG +2 μA VLX = (VOUT + 1V) to (VIN - 1V), TA = +25°C -2 VSS = 0.5V 4.7 5 5.3 μA 0.888 0.9 0.912 V +50 nA SOFT-START (SS) Charging Current ISS FEEDBACK (FB) FB Regulation Voltage VFB-REG FB Input-Bias Current IFB 0 ≤ VFB ≤ 1V, TA = +25°C -50 CURRENT LIMIT Peak Current-Limit Threshold Runaway Current-Limit Threshold Sink Current-Limit Threshold IPEAK-LIMIT 2.15 2.4 2.65 A IRUNAWAY- 2.3 2.65 3 A LIMIT ISINK-LIMIT MAX17577 -0.9 MAX17578 0 A SWITCHING FREQUENCY AND EXTERNAL CLOCK SYNCHRONIZATION (RT/SYNC) Switching Frequency fSW Minimum On-Time tON_MIN Minimum Off-Time tOFF_MIN LX Dead Time VFB Hiccup Threshold SYNC FrequencyCapture Range www.maximintegrated.com 525 600 675 RRT/SYNC = 6.81kΩ 365 400 425 RRT/SYNC = 10.5kΩ 565 600 635 RRT/SYNC = 43.2kΩ 1980 2200 2420 60 80 ns 140 150 160 ns 0.55 0.58 tLX-DT VFB-HICF Hiccup Timeout Bias Current RRT/SYNC = Open 5 VFB Falling (Note 4) IRT_BIAS fSW set by RRT/SYNC 1.1 x fSW kHz ns 0.61 V 32768 cycles 60 μA 1.4 x fSW kHz Maxim Integrated | 3 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Electrical Characteristics (continued) (VIN = VEN/UVLO = 24V, CVCC = 2.2μF, VFB = 1V, RT/SYNC = LX = SS = RESET = Open, VBST to VLX = 5V, VGND = VSOUT = VOUT = 0V, TA = -40°C to +125°C. Typical values are at TA = +25°C. All voltages are referenced to SOUT, unless otherwise noted.) (Note 3) PARAMETER SYNC Pulse-Width SYMBOL CONDITIONS tSYNC VIH SYNC Duty-Cycle Range TYP MAX 100 At RT/SYNC Pin (Note 5) UNITS ns VRT/ SYNC + 0.2 SYNC Threshold VIL MIN VRT/ At RT/SYNC Pin (Note 5) V SYNC - 0.2 DSYNC 10 90 % SYSTEM GROUND (GND) GND Current IGND Sourcing 10 μA RESET (REFERRED TO GND) RESET Output Level Low RESET Output-Leakage Current VRESETL IRESETLKG IRESET = 10mA (Referred to GND) TA = TJ = +25°C, VRESET = 5.5V -0.1 0.4 V +0.1 μA FB Threshold for RESET Deassertion VFB-OKR VFB Rising 93.8 95 97.8 % FB Threshold for RESET Assertion VFB-OKF VFB Falling 90.5 92 94.6 % RESET Delay after FB reaches 95% regulation 1024 Cycles THERMAL SHUTDOWN Thermal Shutdown Rising Threshold TSHDNR 165 °C Thermal Shutdown Hysteresis TSHDNHY 10 °C Note 3: Electrical specifications are production tested at TA = +25ºC. Specifications over the entire operating temperature range are guaranteed by design and characterization. Note 4: See the Overcurrent Protection (OCP)/Hiccup Mode section for more details Note 5: VRT/SYNC = IRT_BIAS × RRT/SYNC. See the Switching Frequency and External Clock Synchronization (RT/SYNC) section for more details. www.maximintegrated.com Maxim Integrated | 4 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Typical Operating Characteristics (VGND = 0V, CVCC = 2.2μF, CBST = 0.1μF, CSS = 5600pF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to GND, unless otherwise noted.) www.maximintegrated.com Maxim Integrated | 5 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Typical Operating Characteristics (continued) (VGND = 0V, CVCC = 2.2μF, CBST = 0.1μF, CSS = 5600pF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to GND, unless otherwise noted.) www.maximintegrated.com Maxim Integrated | 6 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Typical Operating Characteristics (continued) (VGND = 0V, CVCC = 2.2μF, CBST = 0.1μF, CSS = 5600pF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to GND, unless otherwise noted.) www.maximintegrated.com Maxim Integrated | 7 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Typical Operating Characteristics (continued) (VGND = 0V, CVCC = 2.2μF, CBST = 0.1μF, CSS = 5600pF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to GND, unless otherwise noted.) www.maximintegrated.com Maxim Integrated | 8 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Typical Operating Characteristics (continued) (VGND = 0V, CVCC = 2.2μF, CBST = 0.1μF, CSS = 5600pF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to GND, unless otherwise noted.) www.maximintegrated.com Maxim Integrated | 9 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Pin Configuration MAX17577, MAX17578 TOP VIEW 1 EN/UVLO 2 RESET 3 SS 4 VCC 5 RT/SYNC 6 12 OUT + IN 11 LX 10 BST MAX MAX17577 17577// MAX MAX17578 17578 EP 9 GND 8 SOUT 7 FB TDFN-EP 3mm x 3mm Pin Description PIN 1 NAME IN FUNCTION Power Supply Input Pin. Decouple the IN pin to GND with a minimum of 2.2μF X7R ceramic capacitor. Place the capacitor close to the IN and GND pins. Enable/Undervoltage-Lockout Input Pin. Drive EN/UVLO high to enable the converter. Connect to the midpoint of a resistor divider connected between the IN and GND pins to set the input voltage above which the device turns on. Connect to the IN pin for always on operation. Pull low to GND to disable the device. 2 EN/UVLO 3 RESET Active-Low Open-Drain Status Output Pin. The RESET output is driven low to GND if the output voltage drops below 92% of its set value. RESET goes high 1024 cycles after the output voltage rises above 95% of its set value. Connect a pullup resistor of 10kΩ from the RESET pin to an external power supply for monitoring the output voltage status. 4 SS Soft-Start Input Pin. Connect a capacitor from the SS pin to SOUT pin to set the soft-start time. 5 VCC 5V Internal LDO Output Pin. Bypass VCC with a 2.2μF ceramic capacitor to SOUT. LDO does not support the external loading on VCC. 6 RT/SYNC Switching Frequency Programming Input/External Clock Synchronization Input Pin. Connect a resistor from RT/SYNC to SOUT to set the internal clock frequency between 400kHz and 2.2MHz. Leave RT/SYNC open for the default 600kHz switching frequency. The RT/SYNC pin can also be used to synchronize the converter to an external clock. See the Switching Frequency and External Clock Synchronization section for more details. 7 FB 8 SOUT Reference Node for Internal Control Circuitry. Connect SOUT to an output capacitor with a Kelvin connection. Refer to the MAX17577 or MAX17578 evaluation kit data sheets for a layout example. 9 GND System Ground Pin. Connect GND to the power ground plane. Connect all the circuit ground connections together at a single point. Refer to the MAX17577 or MAX17578 evaluation kit data sheets for a layout example. 10 BST Bootstrap Capacitor Pin. Connect a minimum of 0.1μF ceramic capacitor between the BST and LX pins. 11 LX www.maximintegrated.com Feedback Input Pin. Connect FB to the center node of a resistor divider between the GND node and output-voltage node. See the Adjusting Output Voltage section for details. Switching Node. Connect the LX pin to the switching side of the inductor. LX is high-impedance when the device is shut down. Maxim Integrated | 10 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Pin Description (continued) PIN NAME FUNCTION 12 OUT Negative Output Node. Switching current path for low-side nMOSFET. Connect the output capacitor from the OUT pin to system ground. Refer to the MAX17577 or MAX17578 evaluation kit data sheets for a layout example. EP Exposed Pad. Connect to the SOUT pin. Connect EP to a large copper plane with several thermal vias below the device to improve the heat dissipation capability. Refer to the MAX17577 or MAX17578 evaluation kit data sheets for an example of the correct method for EP connection and thermal vias. — www.maximintegrated.com Maxim Integrated | 11 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Functional Diagrams MAX17577/MAX17578 Block Diagram MAX17577/MAX17578 VCC IN INTERNAL LDO REGULATOR SOUT BST VCC UVLO EN/UVLO LEVEL SHIFTER CURRENTSENSE LOGIC CHIPEN VENR THERMAL SHUTDOWN OSCILLATOR CURRENTSENSE AMPLIFIER HIGH-SIDE DRIVER DH CLK RT/SYNC CS LX CCM/DCM/ HICCUP LOGIC AND DRIVERS LOW-SIDE DRIVER DL SLOPE OUT SLOPE CS FB SS SOFT-START CONTROL ++ PWM ISINK-LIMIT ERROR AMPLIFIER RESET CHIPEN FB LEVEL-SHIFTED RESET LOGIC GND www.maximintegrated.com Maxim Integrated | 12 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Detailed Description The MAX17577 and MAX17578 are high-efficiency, high-voltage, inverting, Himalaya synchronous inverting DC-DC converters with integrated MOSFETs operating over a wide 4.5V to (60V - |VOUT|) input-voltage range. The devices can deliver up to 1A current and generate output voltages ranging from -0.9V to -36V. The feedback-voltage regulation accuracy is ±1.3% over a wide -40°C to +125°C temperature range. The devices feature a peak current-mode control architecture with internal loop compensation. At the rising edge of each clock, the high-side MOSFET turns on and the inductor current ramps up. An internal error amplifier compares a fraction of the output voltage at the FB pin to an internal reference. To program the duty cycle of the converter, the output of the error amplifier sets the peak current in the inductor at which the high-side MOSFET turns off, and the low-side MOSFET turns on. During the rest of the switching cycle, stored energy in the inductor is released to the output as its current ramps down. An adjustable input enable/undervoltage-lockout (EN/UVLO) pin programs the desired input voltage at which the converter turns on/off. The soft-start (SS) pin can be used to reduce inrush currents during startup. An open-drain status output (RESET) pin monitors the output voltage and pulls high to indicate that the output voltage is in regulation. The devices feature a RT/SYNC pin that can be used to program the switching frequency or to synchronize the device to an external clock. Low minimum on-time allows high switching frequencies and small solution sizes. The MAX17577 operate in continuous conduction mode (CCM) at all loads; thus, providing a constant frequency operation. The MAX17578 operates in discontinuous conduction mode (DCM) for superior efficiency at light loads. In CCM mode, the inductor current is allowed to go negative. CCM operation provides constant frequency operation at all loads and is useful in applications sensitive to switching frequency. DCM mode of operation offers superior efficiency at light loads by disabling any negative inductor current. Switching Frequency and External Clock Synchronization The switching frequency of the MAX17577 and MAX17578 can be programmed from 400kHz to 2.2MHz with a resistor connected from the RT/SYNC pin to the SOUT pin. Calculate the value of the resistor at the RT/SYNC pin (RRT/SYNC) for a desired switching frequency (fSW) using the following equation. RRT/SYNC = 340 ( ) 20000 −1 fSW Where RRT/SYNC is in kΩ and fSW is in kHz. Leave the RT/SYNC pin open for a default fSW of 600kHz. See Table 1 for RRT/SYNC resistor values for a few common switching frequencies. Table 1. Switching Frequency vs. RRT/SYNC Resistor SWITCHING FREQUENCY (kHz) RRT/SYNC RESISTOR (kΩ) 600 Open 600 10.5 400 6.81 2200 43.2 The RT/SYNC pin can be used to synchronize the internal oscillator of the device to an external clock as shown in Figure 1. When the external clock synchronization feature is used, always connect the RRT/SYNC resistor. The external clock frequency must be between 1.1 x fSW and 1.4 x fSW, where fSW is the switching frequency programmed by the resistor connected at the RT/SYNC pin. When an external clock is applied to the RT/SYNC pin, the internal oscillator frequency changes to an external clock frequency after 16 internal oscillator cycles if at least 8 external clock cycles are applied. The external clock source can either be referenced to the GND or SOUT node. The external clock pulse-width should be more than 100ns (tSYNC) and the allowable duty cycle (DSYNC) range is 10% to 90%. The external clock signal is AC-coupled onto the RT/SYNC pin. The amplitude of the external clock (VSYNCPK_PK) should be chosen based on the following equation. VSYNCPK_PK > 1.3V for 20% ≤ DSYNC ≤ 80% www.maximintegrated.com Maxim Integrated | 13 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters 0.26 VSYNCPK_PK > D for 10% ≤ DSYNC < 20% SYNC 0.26 VSYNCPK_PK > 1 − D for 80% < DSYNC ≤ 90% SYNC The value of CSYNC can be calculated using the following equation. CSYNC = 45 (VSYNCPK_PK) − 1 where CSYNC is in pF. MAX17577/ MAX17578 CSYNC RT/SYNC CLOCK SOURCE RRT/SYNC SOUT GND Figure 1. Synchronization to an External Clock Linear Regulator (VCC) The MAX17577 and MAX17578 have an internal low dropout (LDO) regulator that is referenced to SOUT and powers VCC. This LDO is enabled during power-up or when EN/UVLO is above 0.8V (typ) with respect to GND. VCC powers internal control circuitry. Bypass VCC to SOUT with a 2.2μF low-ESR ceramic capacitor. The MAX17577 and MAX17578 commence operation when VCC > VCC-UVR (4.2V) and turns OFF when VCC < VCC-UVF (3.8V). Operating Input-Voltage Range The minimum operating-input voltage (VIN(MIN)) for a given output-voltage setting is calculated using the following equation. VIN(MIN) = |VOUT| × (1 − DMAX) + DMAX ( 1.5A R + 1 − DMAX × RDS − ONL(MAX) + DMAX × RDS − ONH(MAX) DMAX DCR(MAX) ( ) ) VIN(MIN) cannot be less than 4.5V. To comply with internal device ratings, the maximum operating-input voltage (VIN(MAX)) for a given output-voltage setting is limited to 60V - |VOUT|. For example, the maximum permissible input voltage for a -12V output specification would be 48V. Thus, the value of the VIN(MAX) is given by the following equation. VIN(MAX) = Lower of (60V - |VOUT|) or |VOUT|× (1 - tON_MIN(MAX)×fSW) tON_MIN(MAX)×fSW where: VOUT = Steady-state output voltage RDCR(MAX) = Worst-case DC-resistance of the inductor RDS-ONH(MAX) = Worst-case on-state resistance of the high-side internal MOSFET RDS-ONL(MAX) = Worst-case on-state resistance of the low-side internal MOSFET DMAX = Maximum duty cycle of the converter www.maximintegrated.com Maxim Integrated | 14 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters DMAX = 1 − tOFF_MIN(MAX) × fSW tOFF_MIN(MAX) = Worst-case minimum switch off-time (160ns) tON_MIN(MAX) = Worst-case minimum switch on-time (80ns) fSW = Operating switching frequency. Overcurrent Protection (OCP)/Hiccup Mode The MAX17577 and MAX17578 are provided with a robust overcurrent protection (OCP) scheme that protects the converter under overload and output short-circuit conditions. A cycle-by-cycle peak current limit turns off the high-side MOSFET when the high-side switch current exceeds an internal limit of IPEAK-LIMIT (2.4A). A runaway current limit on the high-side switch current at IRUNAWAY-LIMIT (2.65A) protects the device under output short-circuit conditions at high input voltages when there is insufficient output voltage available to restore the inductor current built up during the on period of the step-down converter. One occurrence of the runaway current limit triggers a hiccup mode. Additionally, if the feedback voltage drops below VFB-HICF any time after soft-start is complete, hiccup mode is triggered. In hiccup mode, the converter is protected by suspending switching for a hiccup timeout period of 32,768 clock cycles at half the programmed switching frequency. Once the hiccup timeout period expires, soft-start is attempted again. Note that when soft-start is attempted under an overload condition, if feedback voltage does not exceed VFB-HICF, the device switches at half the programmed switching frequency for the time duration of the programmed soft-start time and the subsequent 1024 clock cycles. Hiccup mode of operation ensures low power dissipation under output short-circuit conditions. RESET Output The MAX17577 and MAX17578 include a RESET comparator to monitor the output voltage. The open-drain RESET output requires an external pullup resistor. RESET goes high (high impedance) 1024 switching cycles after the regulator output increases above 95% of the designed nominal regulated voltage. RESET goes low when the regulator output voltage drops to below 92% of the nominal regulated voltage. RESET also goes low during thermal shutdown or when the EN/UVLO pin goes below VENF. Prebiased Output When the MAX17577 and MAX17578 start into a prebiased output, both the high-side and low-side nMOSFETs are turned off so that the converter does not sink current from the output. The switching of the nMOSFETs commence only after the voltage at the SS pin (VSS) crosses the voltage at the feedback pin (VFB). VFB then smoothly ramps up to VFBREG in alignment with the VSS and the output voltage reaches its target value. Thermal-Shutdown Protection The MAX17577 and MAX17578 offer thermal shutdown protection to limit the junction temperature.When the junction temperature of the device exceeds +165ºC, 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 10ºC. Soft-start is deasserted during thermal shutdown and initiates the start-up operation when the device recovers from thermal shutdown. Carefully evaluate the total power dissipation (see the Power Dissipation section) to avoid undesired triggering of the thermal shutdown during normal operation. www.maximintegrated.com Maxim Integrated | 15 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Applications Information 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). Calculate the inductor value for a given output voltage and switching frequency using the following equation. L= |VOUT| × 1.1 fSW where VOUT and fSW are nominal values and fSW is in Hz. Select an inductor whose value is nearest to the value calculated by the above formula. Select a low-loss inductor 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 occurs only above the peak current limit threshold (IPEAK-LIMIT). Load Current Capability (IOUT(MAX)) The deliverable load current (IOUT(MAX)) depends on converter operating parameters and maximum operating duty cycle (DMAX_OP), which in turn depends on the designed minimum operating-input voltage (VIN(MIN)_OP). IOUT(MAX) in A is given by the following equation: IOUT(MAX) = 1.5A × (1 − DMAX_OP) where, DMAX_OP = |VOUT| + 1.5A×(RDCR(MAX)+RDS-ONL(MAX)) VIN(MIN)_OP+|VOUT|-1.5A×(RDS-ONH(MAX)-RDS-ONL(MAX)) VIN(MIN)_OP = Designed minimum operating-input voltage, which is ≥ VIN(MIN) (calculated in the Operating Input-Voltage Range section). Input Capacitor Selection The input filter capacitor connected between the IN and GND pins reduces peak currents drawn from the power source and reduces noise and voltage ripple on the input caused by the converter switching. The input capacitor RMS current requirement (IRMS) is defined by the following equation: IRMS= IOUT(MAX) × √ DMAX_OP 1 − DMAX_OP IRMS has a maximum value at maximum duty cycle. Choose an input capacitor that exhibits less than +10°C temperature rise at the maximum RMS input current for optimal long-term reliability. Use low-ESR ceramic capacitors with high-ripple-current capability at the input. X7R capacitors are recommended in industrial applications for their temperature stability. Calculate the input capacitance using the following equation. CIN = IOUT MAX × DMAX_OP ( ) η × fSW × ∆ VIN where: 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 www.maximintegrated.com Maxim Integrated | 16 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters inductance of the longer input cables and the input ceramic capacitor. Actual derating of ceramic capacitors with DCbias voltage must be considered while selecting the input capacitor. Derating curves are available from all major ceramic capacitor manufacturers. Output-Capacitor Selection X7R ceramic output capacitors are preferred due to their stability over temperature in industrial applications. The output capacitors are usually sized to support a step load of 50% of the maximum output current in the application, so the outputvoltage deviation is contained to 3% of the output voltage. The procedure to calculate output capacitance (COUT) in F starts by calculating the right-half plane zero fRHPZ. |VOUT| × (1 − DMAX_OP)2 fRHPZ = 2 × π × L × D MAX_OP × IOUT where IOUT is the load current which is ≤ IOUT(MAX). For a given step-load current (ISTEP) and required output voltage deviation during the step load (ΔVOUT) and target loop crossover frequency (fC), the required output capacitance can be calculated as follows: 1 COUT = 2 × ISTEP × tRESPONSE ∆ VOUT where tRESPONSE, is the response time of the controller. tRESPONSE can be approximated by the following equation: 0.35 tRESPONSE ≅ f C Select the target crossover frequency (fC) to be the lower of fRHPZ / 4 or fSW / 14 and 50kHz. Actual derating of ceramic capacitors with DC-voltage must be considered while selecting the output capacitor. Derating curves are available from all major ceramic capacitor vendors. The output capacitor RMS current requirement (IRMS) is defined by the following equation. √ DMAX_OP IRMS = IOUT × 1 − D MAX_OP Choose an output capacitor that exhibits less than +10°C temperature rise at the maximum RMS output current for optimal long-term reliability. Use low-ESR ceramic capacitors with high-ripple-current capability at the output. Soft-Start Capacitor Selection The MAX17577 and MAX17578 implement adjustable soft-start operation to reduce inrush current. A capacitor connected from the SS pin to the SOUT pin programs the soft-start time. The selected output capacitance (COUT_SEL) in F and the output voltage (VOUT) determine the minimum required soft-start capacitance in F as follows: CSS ≥ 28 × 10 − 6 × COUT_SEL × | VOUT| The soft-start time (tSS) is related to the capacitor connected at SS (CSS) by the following equation: tSS = CSS 5.55 × 10 − 6 For example, to program a 1ms soft-start time, a 5.6nF capacitor should be connected from the SS pin to the SOUT pin. Note that during startup, the device operates at half the programmed switching frequency until the feedback (FB) voltage reaches VFB-HICF (0.58V). Adjusting Output Voltage Set the output voltage using a resistive voltage-divider connected from the GND node to the output-voltage node (VOUT) as shown in Figure 2. Connect the center node of the divider to the FB pin. Use the following procedure to choose the resistive voltage-divider values. Calculate the resistor RFB_TOP from the GND node to the FB pin as follows: www.maximintegrated.com Maxim Integrated | 17 MAX17577, MAX17578 RFB_TOP = ( 111 × 1 − DMAX_OP 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters ) (fCx COUT_SEL) where: RFB_TOP is in kΩ fC = Crossover frequency in Hz COUT_SEL = Actual capacitance of output capacitor at DC-bias voltage in F. The minimum allowable value of RFB_TOP is (5.6 x |VOUT|), where RFB_TOP is in kΩ. If the value of RFB_TOP calculated using the above equation is less than (5.6 x |VOUT|), increase the value of RFB_TOP to at least (5.6 x |VOUT|). Calculate the resistor RFB_BOT from the FB pin to the VOUT node as follows: RFB_BOT = RFB_TOP × 0.9 ( | VOUT| − 0.9) where RFB_BOT is in kΩ. GND MAX17577/ MAX17578 RFB_TOP FB SOUT RFB_BOT VOUT Figure 2. Setting the Output Voltage Setting the Input Undervoltage-Lockout Level The MAX17577 and MAX17578 offer an adjustable input undervoltage-lockout level. Set the voltage above which the device turns on with a resistive voltage-divider connected from IN to GND as shown in Figure 3. Connect the center node of the divider to the EN/UVLO pin. Choose RUVL_TOP to be 3.32MΩ and then calculate RUVL_BOT as follows: RUVL_BOT = RUVL_TOP × 1.229 (VINU − 1.229) where VINU is the input-voltage level at which the device is required to turn on. Choose a minimum of 4.45V for VINU. If the EN/UVLO pin is driven from an external signal source, a series resistance of 1kΩ (min) is recommended to be placed between the output pin of the signal source and the EN/UVLO pin to reduce voltage ringing on the line. www.maximintegrated.com Maxim Integrated | 18 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters VIN IN MAX17577/ MAX17578 RUVL_TOP EN/UVLO RUVL_BOT GND Figure 3. Setting the Input Undervoltage-Lockout Inductive Output Short-Circuit Protection In applications where an inductive short-circuit at the output terminals is expected, it is recommended to use a resistor (RGND) and a Schottky diode (DGND) as shown in Figure 4. In a typical application, the high inductance (LSH) and low resistance (RSH) in the short-circuit path can cause the VOUT to swing positive above the system ground. This could forward bias the internal protection diode (DINT) and likely damage the device. To prevent the damage, connect RGND = 50Ω between the GND pin and the system ground, and DGND across SOUT and GND pins. It is recommended to keep the parasitic board or wiring inductance to a minimum value. L LX MAX17577/ MAX17578 RGND RSH COUT GND LSH DGND INDUCTIVE OUTPUT SHORT-CIRCUIT PATH DINT SOUT OUT VOUT Figure 4. Inductive Output Short-Circuit Protection Power Dissipation At a given operating condition, the power losses that lead to a temperature rise of the part are estimated as follows: ( ( )) 1 IOUT 2 PLOSS = POUT × η − 1 − ( 1 − D ) × RDCR POUT = | VOUT| × IOUT where: POUT = Output power η = Efficiency of the converter D = Operating duty cycle RDCR = DC resistance of the inductor See the Typical Operating Characteristics section for more information on efficiency at typical operating conditions. www.maximintegrated.com Maxim Integrated | 19 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters The junction temperature of the device can be estimated at any given maximum ambient temperature (TA) from the following equation: TJ = TA + (θJA × PLOSS) PCB Layout Guidelines Use the following guidelines for a good PCB layout: ● ● ● ● ● ● ● ● ● Place the input capacitor as close as possible to the IN pin. Place the output capacitor as close as possible to the OUT pin. Minimize the length and area of the trace connection from the LX pin to the inductor. Place the GND terminals of the input capacitor, output capacitor, and the inductor as close as possible and connect them to the GND plane. Place the BST capacitor close to the BST and LX pins. Connect the VCC bypass capacitor close to the VCC pin and connect the other terminal to the SOUT plane. Place the RT/SYNC resistor and feedback resistor divider as close as possible to their respective pins. Connect their other terminals to the SOUT plane. Keep all the power connections and load connections short. Connect the SOUT and OUT nodes at a point where the switching activity is at its minimum. Refer to the MAX17577/MAX17578 EV kit data sheet for recommended PCB layout and routing. Typical Application Circuits -5V Typical Application Circuits R1 3.32MΩ VIN 16V TO 55V EN/UVLO BST GND VCC C4 0.1µF MAX17577/ LX MAX17578 SS C2 2.2µF C3 5.6nF L1 = XEL5050-103ME (5.3mm x 5.5mm) C1 = C3225X7R2A225K230AB (2.2µF/100V/1210/X7R) C2 = GRM188R71A225KE15 (2.2µF/10V/0603/X7R) C5 = GRM32ER71E226ME15 (22µF/25V/1210/X7R) R2 294kΩ IN C1 2.2µF fSW = 600kHz FB RT/SYNC SOUT EP RESET OUT L1 10µH R3 121kΩ FB C5 22µF FB R4 26.7kΩ VOUT -5V, 1A Figure 5. MAX17577 and MAX17578 -5V Output Application Circuit Compatible with 24V Input Bus Voltage www.maximintegrated.com Maxim Integrated | 20 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Typical Application Circuits (continued) R1 3.32MΩ VIN 4.5V TO 55V EN/UVLO BST C1 2 x 4.7µF MAX17577 LX L1 10µH VCC SS C3 5.6nF L1 = XEL5050-103ME (5.3mm x 5.5mm) C1 = GRM31CZ72A475KE11 (2 x 4.7µF/100V/1206/X7R) C2 = GRM188R71A225KE15 (2.2µF/10V/0603/X7R) C5 = GRM32ER71E226ME15 (22µF/25V/1210/X7R) C4 0.1µF GND C2 2.2µF fSW = 600kHz R2 1.33MΩ IN FB RT/SYNC SOUT EP R3 226kΩ FB C5 22µF RESET OUT FB R4 49.9kΩ VOUT -5V, 0.5A Figure 6. MAX17577 -5V Output Application Circuit Compatible with 5V Input Bus Voltage -12V Typical Application Circuit R1 3.32MΩ VIN 16V TO 48V EN/UVLO BST C4 0.1µF GND MAX17577/ VCC MAX17578 SS C2 2.2µF C3 5.6nF L1 = XEL5050-223ME (5.3mm x 5.5mm) C1 = GRM31CZ72A475KE11 (4.7µF/100V/1206/X7R) C2 = GRM188R71A225KE15 (2.2µF/10V/0603/X7R) C5 = GRM32ER71E226ME15 (22µF/25V/1210/X7R) R2 294kΩ IN C1 4.7µF fSW = 600kHz LX FB RT/SYNC SOUT EP RESET OUT L1 22µH R3 340kΩ FB C5 22µF FB R4 27.4kΩ VOUT -12V, 0.8A Figure 7. MAX17577 and MAX17578 -12V Output Application Circuit Compatible with 24V Input Bus Voltage www.maximintegrated.com Maxim Integrated | 21 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Typical Application Circuits (continued) R1 3.32MΩ VIN 4.5V TO 48V fSW = 600kHz EN/UVLO BST C1 2 x 4.7µF C4 0.1µF GND MAX17577 LX L1 22µH VCC SS C2 2.2µF C3 5.6nF L1 = XEL5050-223ME (5.3mm x 5.5mm) C1 = GRM31CZ72A475KE11 (2 x 4.7µF/100V/1206/X7R) C2 = GRM188R71A225KE15 (2.2µF/10V/0603/X7R) C5 = GRM32ER71E226ME15 (22µF/25V/1210/X7R) R2 1.33MΩ IN FB RT/SYNC SOUT EP R3 487kΩ FB RESET OUT C5 22µF FB R4 39.2kΩ VOUT -12V, 0.3A Figure 8. MAX17577 -12V Output Application Circuit Compatible with 5V Input Bus Voltage Ordering Information MODE OF OPERATION PIN-PACKAGE MAX17577ATC+ PART NUMBER CCM 12 TDFN 3mm x 3mm MAX17577ATC+T CCM 12 TDFN 3mm x 3mm MAX17578ATC+ DCM 12 TDFN 3mm x 3mm MAX17578ATC+T DCM 12 TDFN 3mm x 3mm + Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape-and-reel. www.maximintegrated.com Maxim Integrated | 22 MAX17577, MAX17578 4.5V to 60V, 1A High-Efficiency, Synchronous, Inverting Output DC-DC Converters Revision History REVISION NUMBER REVISION DATE 0 10/20 DESCRIPTION Release for Market Intro 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. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2020 Maxim Integrated Products, Inc.