MAX17662BATE+

EVALUATION KIT AVAILABLE Click here for production status of specific part numbers. MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter General Description Benefits and Features The MAX17662 is a high-efficiency, synchronous stepdown DC-DC converter with integrated MOSFETs operating over an input-voltage range of 3.5V to 36V. It can deliver up to 2A current. Output voltage is programmable from 0.6V up to 90% of VIN. Built-in compensation across the output-voltage range eliminates the need for external compensation components. ● Reduces External Components and Total Cost • No Schottky—Synchronous Operation • Internal Compensation Components • All-Ceramic Capacitors, Compact Layout ● Reduces Number of DC-DC Regulators to Stock • Wide 3.5V to 36V Input • Adjustable Output Voltage Range from 0.6V up to 90% of VIN • Delivers Up to 2A Over the Temperature Range • 400kHz to 2.2MHz Adjustable Frequency • Available in a 16-pin, 3mm x 3mm TQFN Package The MAX17662 features a peak-current-mode control architecture. The MAX17662 can be operated in forced pulse-width modulation (PWM), or discontinuous-conduction mode (DCM) to enable high efficiency under full-load and light-load conditions. The MAX17662 offers a low minimum on-time that allows high switching frequencies and a smaller solution size. ● Reduces Power Dissipation • Peak Efficiency of 95% • DCM Mode Enable Enhanced Light-Load Efficiency • Wide 2.4V to 12V Bootstrap Bias Input (EXTVCC) for Improved Efficiency • 6.5μA Shutdown Current The feedback-voltage regulation accuracy over -40°C to +125°C is ±1.33%. The device is available in a 16-pin (3mm x 3mm) TQFN package. Simulation models are available. ● Operates Reliably in Adverse Industrial Environments • Hiccup-Mode Overload Protection • Adjustable and Monotonic Startup with Prebiased Output Voltage • Built-in Output-Voltage Monitoring with RESET • Programmable EN/UVLO Threshold • Overtemperature Protection • High Industrial -40°C to +125°C Ambient Operating Temperature Range/-40°C to +150°C Junction Temperature Range 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 Ordering Information appears at end of data sheet. Typical Application Circuit VIN 6.5V TO 36V C1 4.7µF RT EN/UVLO MODE C3 2.2µF C2 6800pF VCC MAX17662 SGND BST SS EXTVCC PGND RESET C5 0.1µF LX FB EP 19-100525; Rev 0; 7/19 VIN L1 8.2µH FB R3 4.7Ω C6 0.1µF VOUT C4 22µF FB VOUT 5V,2A R1 232kΩ R2 31.6kΩ fSW : 500kHz C1: 4.7µF/50V/X7R/1206 (GRM31CR71H475KA12) L1: 8.2µH (XAL5050-822ME) C4: 22µF/25V/X7R/1210 (GRM32ER71E226ME15) MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Absolute Maximum Ratings VIN to PGND........................................................... -0.3V to +40V EN/UVLO to SGND ................................................ -0.3V to +40V LX to PGND ................................................. -0.3V to (VIN + 0.3V) EXTVCC to SGND.................................................. -0.3V to +14V BST to PGND ......................................................... -0.3V to +42V BST to LX .............................................................. -0.3V to +2.2V BST to VCC............................................................. -0.3V to +40V FB, SS, VCC, RT to SGND .................................... -0.3V to +2.2V MODE, RESET to SGND ......................................... -0.3V to +6V PGND to SGND ..................................................... -0.3V to +0.3V LX total RMS current............................................................±3.8A Output Short-Circuit duration ......................................Continuous Continuous Power Dissipation (TA = +70°C) TQFN Multilayer Board (derate 23.1mW/°C above +70°C) ......................................................................1847.6mW 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 TQFN Package Code T1633+5C Outline Number 21-0136 Land Pattern Number 90-0032 Thermal Resistance, Four-Layer Board (Note 2) Junction-to-Ambient (θJA) 38°C/W Junction-to-Case Thermal Resistance (θJC) 4°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. Note 2: Package thermal resistances were obtained using the MAX17662 Evaluation Kit with no airflow. www.maximintegrated.com Maxim Integrated | 2 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Electrical Characteristics (VIN = VEN/UVLO = 24V, RT = Unconnected (fSW = 500kHz), CVCC = 2.2uF, VMODE = VEXTVCC = VSGND = VPGND = 0, VFB = 0.64V, LX = SS = RESET = Open, VBST to VLX = 1.8V, 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 3)) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 36 V 24 μA INPUT SUPPLY (VIN) Input Voltage Range VIN Input Shutdown Current Input Quiescent Current Input UVLO 3.5 IIN_SH VEN/UVLO = 0V (Shutdown mode) IQ_DCM DCM mode, VLX = 0.1V IQ_PWM Normal Switching mode, VFB = 0.58V VIN_UVLO_R VIN rising VIN_HYS Hysteresis 6.5 2 mA 8.2 2.95 3.26 0.246 V ENABLE/UVLO (EN/UVLO) VENR EN/UVLO Threshold VEN_HYS VEN_TRUESD EN/UVLO Input Leakage Current IEN VEN/UVLO rising 1.194 1.25 Hysteresis 0.1 VEN/UVLO falling, true shutdown 0.75 1.303 V VEN/UVLO = 0V, TA = +25°C -50 0 +50 3.5V < VIN < 36V, IVCC = 1mA 1.74 1.80 1.86 1mA < IVCC < 25mA 1.70 1.80 1.86 VCC_UVR VCC rising 1.605 1.640 1.683 VCC_HYS Hysteresis nA VCC (LDO) VCC Output Voltage Range VCC UVLO VCC 0.065 V V EXTVCC (EXT LDO) EXTVCC Operating Voltage Range 2.448 EXTVCC rising EXTVCC Switchover Threshold 2.348 Hysteresis EXTVCC Shutdown Current 12 2.400 2.448 0.09 VEN/UVLO = 0, EXTVCC = 12V V V 19 μA POWER MOSFETS High-Side nMOS OnResistance RDS_ONH ILX = 0.3A, sourcing 130 250 mΩ Low-Side nMOS OnResistance RDS_ONL ILX = 0.3A, sinking 90 170 mΩ LX Leakage Current ILX_LKG +2 μA μA VIN = 36V, TA = +25°C, VLX = (VPGND + 1)V to (VIN -1)V, VEN/UVLO = 0V -2 VSS = 0.3V 4.7 5 5.3 VMODE = VSGND 0.592 0.600 0.608 VMODE = VCC 0.592 0.600 0.608 SOFT-START (SS) Charging Current ISS FEEDBACK (FB) FB Regulation Voltage VFB_REG FB Input Bias Current IFB www.maximintegrated.com VFB = 1V, TA = +25°C -50 +50 V nA Maxim Integrated | 3 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Electrical Characteristics (continued) (VIN = VEN/UVLO = 24V, RT = Unconnected (fSW = 500kHz), CVCC = 2.2uF, VMODE = VEXTVCC = VSGND = VPGND = 0, VFB = 0.64V, LX = SS = RESET = Open, VBST to VLX = 1.8V, 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 3)) PARAMETER SYMBOL CONDITIONS MIN VM_DCM VMODE = VCC (DCM mode) 1.22 VM_PWM VMODE = VSGND (PWM mode) TYP MAX UNITS MODE MODE Threshold 0.66 V CURRENT LIMIT Peak Current-Limit Threshold IPEAK_LIMIT Valley Current-Limit Threshold IVALLEY_LIMIT VMODE = VCC 2.8 3.4 4.1 -0.1 0 +0.1 VMODE = VSGND -1.8 A A TIMING (RT) Switching Frequency VFB Undervoltage Trip Level to Cause Hiccup fSW RRT = 51.1kΩ 375 400 425 RRT = 8.25kΩ 1980 2200 2420 RRT = Open 475 500 525 0.375 0.390 0.405 VFB_HICF HICCUP Timeout (Note 4) Minimum On-Time tON_MIN Minimum Off-Time tOFF_MIN 32768 60 126 kHz V Cycles 90 ns 176 ns 0.4 V +0.1 μA RESET RESET Output Level Low RESET Output Leakage Current VRESETL IRESET = 10mA IRESETLKG TA = TJ = +25°C -0.1 FB Threshold for RESET Deassertion VFB_OKR VFB rising 93.1 95.0 97.0 % of VFB_REG FB Threshold for RESET Assertion VFB_OKF VFB falling 89.8 92.0 93.2 % of VFB_REG RESET Delay After FB Reaches 95% Regulation 1024 Cycles 155 °C 20 °C THERMAL SHUTDOWN (TEMP) Thermal-Shutdown Threshold Thermal-Shutdown Hysteresis Temperature rising Note 3: Electrical specifications are production tested at TA = +25°C. Specifications over the entire operating temperature range are guaranteed by design and characterization. Note 4: See Overcurrent Protection/Hiccup Mode section for more details. www.maximintegrated.com Maxim Integrated | 4 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics ((VEN/UVLO = VIN = 24V, VSGND = VPGND = 0V, CVCC = 2.2μF, CBST = 0.1μF, CSS = 6800pF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)) www.maximintegrated.com Maxim Integrated | 5 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) ((VEN/UVLO = VIN = 24V, VSGND = VPGND = 0V, CVCC = 2.2μF, CBST = 0.1μF, CSS = 6800pF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)) www.maximintegrated.com Maxim Integrated | 6 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) ((VEN/UVLO = VIN = 24V, VSGND = VPGND = 0V, CVCC = 2.2μF, CBST = 0.1μF, CSS = 6800pF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)) www.maximintegrated.com Maxim Integrated | 7 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) ((VEN/UVLO = VIN = 24V, VSGND = VPGND = 0V, CVCC = 2.2μF, CBST = 0.1μF, CSS = 6800pF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)) www.maximintegrated.com Maxim Integrated | 8 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (continued) ((VEN/UVLO = VIN = 24V, VSGND = VPGND = 0V, CVCC = 2.2μF, CBST = 0.1μF, CSS = 6800pF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)) www.maximintegrated.com Maxim Integrated | 9 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Pin Configuration LX LX BST EXTVCC 16 TQFN 12 11 10 9 TOP VIEW PGND 13 PGND 14 8 RESET 7 RT 6 FB 5 SS MAX MAX17662 17662 VIN 15 VIN 16 2 3 4 SGND MODE EN/UVLO 1 VCC *EP 3mm x 3mm Pin Description PIN NAME FUNCTION Enable/Undervoltage Lockout Pin. Drive EN/UVLO high to enable the output. Connect to the center of the resistor-divider between VIN and SGND to set the input voltage at which the part turns on. Connect to VIN pins for always-on operation. Pull low (lower than VEN_TRUESD) for disabling the device. 1 EN/UVLO 2 VCC 3 SGND Signal Ground 4 MODE The MODE pin configures the device to operate in either PWM or DCM modes of operation. Connect MODE to SGND for constant-frequency PWM operation at all loads. Connect MODE to VCC for DCM operation (at light loads). See the Mode Selection (MODE) section for more details. 5 SS Soft-Start Input. Connect a capacitor from SS to SGND to set the soft-start time. 6 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. 7 RT Programmable Switching Frequency Input. Connect a resistor from RT to SGND to set the regulator’s switching frequency between 400kHz and 2.2MHz. Leave RT pin open for the default 500kHz frequency. See the Setting the Switching Frequency (RT) section for more details. 8 RESET Open-Drain RESET Output. The RESET output is driven low if FB drops below VFB_OKF. RESET goes high 1024 cycles after FB rises above VFB_OKR. 9 EXTVCC External Power Supply Input. Applying a voltage between 2.448V and 12V at EXTVCC will bypass the internal LDO and improve overall converter efficiency. Connect a buck regulator output to EXTVCC through an RC filter (4.7Ω, 0.1μF) to protect the EXTVCC pin from reaching its absolute maximum rating (-0.3V) during an output short-circuit condition. When EXTVCC is not used, connect it to SGND. 10 BST www.maximintegrated.com 1.8V LDO Output. Bypass VCC with a 2.2μF ceramic capacitance to SGND. LDO does not support the external loading on VCC Boost Flying Capacitor. Connect a 0.1μF ceramic capacitor between BST and LX. Maxim Integrated | 10 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Pin Description (continued) PIN NAME 11, 12 LX 13, 14 PGND 15, 16 VIN Power-Supply Input Pins. 3.5V to 36V input-supply range. Decouple to PGND with a minimum 2.2µF capacitor; place the capacitor close to the VIN and PGND pins. See Input Capacitor Selection for more details. — EP Exposed Pad. Always connect EP to the SGND pin of the IC. Also, connect EP to a large plane with several thermal vias for best thermal performance. Refer to the MAX17662 Evaluation Kit data sheet for an example of the correct method for EP connection and thermal vias. www.maximintegrated.com FUNCTION Switching Node Pins. Connect LX pins to the switching side of the inductor. Power Ground Pins of the Converter. Connect externally to the power ground plane. Refer to the MAX17662 Evaluation Kit data sheet for a layout example. Maxim Integrated | 11 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Block Diagram MAX17662 EXTVCC EXT LDO INTERNAL LDO SGND VCC BIAS SELECT BST 1.8V VCC VIN VIN POK HICCUP VCC_UVR VIN EN/UVLO VIN_UVLO_R VCCOK INOK ENOK PWM/DCM/ HICCUP LOGIC CHIPEN VENR LX THERMAL SHUTDOWN RT OSCILLATOR PGND CURRENT- SENSE LOGIC FB MODE SELECTION LOGIC ERROR AMPLIFIER/ LOOP COMPENSATION MODE SWITCHOVER LOGIC VCC SS SLOPE COMPENSATION RESET 5μA HICCUP www.maximintegrated.com CHIPEN FB RESET LOGIC Maxim Integrated | 12 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Detailed Description The MAX17662 is a high-efficiency, synchronous step-down DC-DC converter with integrated MOSFETs. It can deliver up to 2A over an input voltage range of 3.5V to 36V. Built-in compensation across the output-voltage range eliminates the need for external compensation components. The feedback-voltage regulation accuracy over -40°C to +125°C is ±1.33%. 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’s on-time, the inductor current ramps up. During the second half of the switching cycle, the high-side MOSFET turns off and the low-side MOSFET turns on. The inductor releases the stored energy as its current ramps down and provides current to the output. The device features a MODE pin that can be used to operate the device in PWM or DCM mode. The device also features adjustable-input undervoltage lockout, adjustable soft-start, and output voltage monitoring with open-drain RESET. The MAX17662 offers a low minimum on time that allows high switching frequencies and a smaller solution size. Mode Selection (MODE) The MAX17662 supports forced PWM and DCM mode of operation. The device enters the required mode of operation based on the setting of the MODE pin as detected during power-up after VIN, VCC, and EN/UVLO voltages exceed their respective UVLO rising thresholds (VIN_UVLO_R, VCC_UVR, VENR). If the state of the MODE pin is high (> VM_DCM), the device operates in DCM mode at light loads. If the state of the MODE pin is low (< VM_PWM), the device operates in constant-frequency PWM mode at all loads. See the MODE section in the Electrical Characteristics table for details. PWM Mode Operation In PWM mode, the inductor current is allowed to go negative. PWM operation provides constant frequency operation at all loads and is useful in applications sensitive to switching frequency. However, the PWM mode of operation gives lower efficiency at light loads compared to the DCM mode of operation. DCM Mode Operation In DCM mode of operation, the inductor current can be discontinuous at light loads. The inductor current is not allowed to go negative. Switching pulses are skipped when the buck converter is operated close to no-load condition. DCM operation offers better efficiency performance compared to PWM at light loads. The steady-state output voltage ripple in DCM mode is comparable to PWM mode. Linear Regulator (VCC and EXTVCC) The MAX17662 has two built-in low dropout (LDO) linear regulators that power VCC. One LDO is powered from VIN (internal LDO), while the other LDO is powered from EXTVCC (EXT LDO). The internal LDO is enabled either during power-up or when voltage on EN/UVLO pin is recycled. Only one of the two LDOs is in operation at a time, depending on the voltage present at EXTVCC. If EXTVCC is greater than 2.4V (typ), VCC is powered by EXT LDO. Powering VCC from EXTVCC increases efficiency at higher input voltages. The typical VCC output voltage is 1.8V. Bypass VCC to SGND with a 2.2μF low-ESR ceramic capacitor. VCC powers the internal blocks and the low-side MOSFET driver. VCC also recharges the external bootstrap capacitor. The MAX17662 employs an undervoltage-lockout circuit that forces the buck converter off when VCC falls below the falling threshold (VCC_UVR - VCC_HYS). The buck converter can be immediately enabled again when VCC > VCC_UVR. The 65mV (typ) UVLO hysteresis prevents chattering on power-up/power-down. If the buck converter output is shorted to ground in applications where the converter output is connected to the EXTVCC pin, then the transfer from EXT LDO to the internal LDO happens seamlessly, without any impact to normal functionality. Add a local bypass capacitor of 0.1μF on the EXTVCC pin to SGND, and a 4.7Ω resistor from the buck regulator output www.maximintegrated.com Maxim Integrated | 13 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter node to the EXTVCC pin, to protect the EXTVCC pin from reaching its absolute maximum rating (-0.3V) during output short-circuit conditions. Connect EXTVCC pin to SGND when not in use. Setting the Switching Frequency (RT) The switching frequency of the device can be programmed between 400kHz and 2.2MHz by using a resistor connected from the RT pin to SGND. The switching frequency (fSW) is related to the resistor connected at the RT pin (RRT) by the following equation: 20625 RRT = f −1 SW where, RRT is in kΩ and fSW is in kHz. Leaving the RT pin open makes the device operate at the default switching frequency of 500kHz. See Table 1 for RT resistor values for a few common switching frequencies. Table 1. Switching Frequency vs. RT Resistor SWITCHING FREQUENCY (kHz) RT RESISTOR (kΩ) 400 51.1 500 Open 500 40.2 2200 8.25 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) ( ) ( 1 − fSW MAX × tOFF_MIN MAX ( ) ( ) ) )) + (I OUT(MAX) × (RDS_ONH(MAX)-RDS_ONL(MAX))) VOUT VIN(MAX) = f SW(MAX) × tON_MIN(MAX) where: VOUT = Programmed steady-state output voltage IOUT(MAX) = Maximum load current RDCR(MAX) = Worst-case DC resistance of the inductor fSW(MAX) = Maximum switching frequency tOFF_MIN(MAX) = Worst-case minimum switch off-time (176ns) tON_MIN(MAX) = Worst-case minimum switch on-time (90ns) RDS_ONL(MAX) and RDS_ONH(MAX) = Worst-case on-state resistances of low-side and high-side internal MOSFETs, respectively. The minimum input voltage (VIN_SU) for startup/restart of the buck converter should be as follows: VIN_SU≥ VOUT_BIAS+ 1.8 where: VOUT_BIAS = Prebias voltage on output node. The maximum slew rate that can be applied on input voltage is 30V/µsec. www.maximintegrated.com Maxim Integrated | 14 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Overcurrent Protection (OCP)/Hiccup Mode The device is provided with a robust overcurrent-protection (OCP) scheme that protects the device under overload and output short-circuit conditions. A cycle-by-cycle peak current limit turns off the high-side MOSFET whenever the highside switch current exceeds an internal limit of IPEAK_LIMIT (3.4A (typ)). The short-circuit protection scheme protects the device by using an hysteretic control of the current during the soft start and by using the feedback under voltage fault in steady state. In hysteretic control, the positive current limit is triggered when the peak value of the inductor current hits a fixed threshold (IPEAK_LIMIT - 3.4A, typ). At this point, the high-side switch is turned off and the low-side switch is turned on. The low-side switch is kept on until the inductor current reduces below 0.7 x IPEAK_LIMIT. If the feedback voltage drops below VFB_HICF due to a fault condition any time after soft-start is completed, then the hiccup mode is activated. In hiccup mode, the converter is protected by suspending switching for a hiccup timeout period of 32,768 clock cycles of the switching frequency. Once the hiccup timeout period expires, soft-start is attempted again. Note that when soft-start is attempted under overload condition, if feedback voltage does not exceed VFB_HICF, the device continues to switch in hysteretic control for the duration of the programmed soft-start time and 2048 clock cycles. Hiccup mode of operation ensures low average power dissipation under output short-circuit conditions. RESET Output The device includes a RESET comparator to monitor the status of the output voltage. The open-drain RESET output requires an external pullup resistor. RESET goes high (high impedance) 1024 switching cycles after the FB voltage increases above VFB_OKR. RESET goes low when the FB voltage drops to below VFB_OKF. RESET also goes low during thermal shutdown or when the EN/UVLO pin goes below EN/UVLO falling threshold (VENR - VEN_HYS). Prebiased Output When the device starts into a prebiased output, the minimum input voltage (VIN_SU) to enable buck converter startup should be calculated as follows: VIN_SU≥ VOUT_BIAS+ 1.8 where: VOUT_BIAS = Prebias voltage on output node. In a prebiased output condition, 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 +155ºC, an on-chip thermal sensor shuts down the device, allowing the device to cool. The device turns on with soft-start after the junction temperature reduces by 20ºC. Carefully evaluate the total power dissipation (see the Power Dissipation section) to avoid unwanted triggering of thermal shutdown during normal operation. www.maximintegrated.com Maxim Integrated | 15 MAX17662 3.5V to 36V, 2A, 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’s 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 is the duty ratio of the converter 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: VOUT L = 1.25 × f SW 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 previous formula. Select a low-loss inductor closest to the calculated value with acceptable dimensions and having the lowest possible DC resistance. The saturation current rating (ISAT) of the inductor must be high enough to ensure that saturation can occur only above the peak current-limit value of IPEAK_LIMIT. www.maximintegrated.com Maxim Integrated | 16 MAX17662 3.5V to 36V, 2A, 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 usually sized to support a step load of 50% of the maximum output current in the application, so outputvoltage 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 0.33 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 1/9th of fSW if the switching frequency is less than or equal to 900kHz. If the switching frequency is more than 900kHz, select fC to be 100kHz. 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 ≥ 28 × 10 − 6 × CSEL × VOUT The soft-start time (tSS) is related to the capacitor connected at SS (CSS) by the following equation: tSS = CSS 8.325 × 10 − 6 For example, to program a 0.82ms soft-start time, a 6.8nF 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 65% of set output nominal voltage. www.maximintegrated.com Maxim Integrated | 17 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Setting the Input Undervoltage-Lockout Level The device offers an adjustable input undervoltage-lockout level. Set the voltage at which the device turns on with a resistive voltage-divider connected from VIN to SGND (See Figure 1). Connect the center node of the divider to EN/ UVLO. Choose R1 to be 3.3MΩ and then calculate R2 as follows: R2 = R1 × 1.25 ( VINU − 1.25 ) where VINU is the input-voltage level at which the device is required to turn on. Ensure that VINU is higher than 0.8 x VOUT to avoid hiccup during slow power-up (slower than soft-start)/power-down. If the EN/UVLO pin is driven from an external signal source, a series resistance of minimum 1kΩ is recommended to be placed between the output pin of signal source and the EN/UVLO pin, to reduce voltage ringing on the line. VIN R1 EN/UVLO R2 SGND Figure 1. Setting the Input Undervoltage Lockout Adjusting Output Voltage The output voltage of the buck converter can be programmed between 0.6V to 90% of VIN. However, for the output voltage setting range between 0.6V and 1.8V, the minimum load should be 100μA for output voltage regulation. Set the output voltage with a resistive voltage-divider connected from the output-voltage node (VOUT) to SGND (see 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 resistor RTOP from the output to the FB pin as follows: RTOP = 203 ( fCx COUT_SEL ) where: RTOP is in kΩ fC = Crossover frequency in Hz COUT_SEL = Actual capacitance of selected output capacitor at DC-bias voltage in F. Calculate resistor RBOT from the FB pin to SGND as follows: RBOT = RTOP × 0.6 (VOUT − 0.6) RBOT is in kΩ. www.maximintegrated.com Maxim Integrated | 18 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter VOUT RTOP FB RBOT SGND Figure 2. Setting the Output Voltage Power Dissipation At a particular operating condition, the power losses that lead to temperature rise of the part are estimated as follows: ( ( 1 )) ( PLOSS = POUT × 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 = 38°C/W θJC = 4°C/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) 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 degrade operating lifetimes. www.maximintegrated.com Maxim Integrated | 19 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter 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 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 to keep the signal ground quiet. The power 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 or vias that connect to a large 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 MAX17662 evaluation kit layout available at www.maximintegrated.com. www.maximintegrated.com Maxim Integrated | 20 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Application Circuits Typical Application Circuit—5V Output with 500kHz Switching Frequency VIN 6.5V TO 36V C1 4.7μF VIN EN/UVLO VIN RT BST C5 0.1μF MODE LX VCC C3 2.2μF L1 8.2μH C1: 4.7μF/50V/X7R/1206 (GRM31CR71H475KA12) L1: 8.2μH (XAL5050-822ME) C4: 22μF/25V/X7R/1210 (GRM32ER71E226ME15) fSW: 500kHz PWM MODE: CONNECT MODE WITH SGND DCM MODE: CONNECT MODE WITH VCC VOUT 5V, 2A M A X 17662 SGND LX RESET FB PGND SS PGND C2 6800pF EXTVCC C4 22μF R1 232kΩ R2 31.6kΩ R3 4.7Ω VOUT EP C6 0.1μF Typical Application Circuit—3.3V Output with 500kHz Switching Frequency VIN 4.5V TO 36V C1 4.7μF EN/UVLO VIN RT VIN BST C5 0.1μF MODE LX VCC C3 2.2μF C2 6800pF www.maximintegrated.com VOUT 3.3V, 2A M A X 17662 SGND LX RESET FB SS L1 5.6μH C1: 4.7μF/50V/X7R/1206 (GRM31CR71H475KA12) L1: 5.6μH (XAL5050-562ME) C4: 47μF/10V/X7R/1210 (GRM32ER71A476KE15L) fSW: 500kHz PWM MODE: CONNECT MODE WITH SGND DCM MODE: CONNECT MODE WITH VCC PGND PGND EXTVCC C4 47μF R3 4.7Ω R1 120kΩ R2 26.7kΩ VOUT EP C6 0.1μF Maxim Integrated | 21 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Typical Application Circuits (continued) Typical Application Circuit—5V Output with 1MHz Switching Frequency VIN 7V TO 36V C1 2.2μF VIN EN/UVLO RT R4 19.6kΩ VIN BST C5 0.1μF MODE LX VCC C3 2.2μF VOUT 5V, 2A M A X 17662 SGND LX RESET FB SS L1 4.7μH C1: 2.2μF/50V/X7R/1206 (C3216X7R1H225K160AE) L1: 4.7μH (XAL4030-472ME; 4.3mm x 4.3mm) C4: 10μF/16V/X7R/1206 (C3216X7R1C106K160AC) fSW: 1MHz PWM MODE: CONNECT MODE WITH SGND DCM MODE: CONNECT MODE WITH VCC PGND PGND C2 6800pF EXTVCC C4 10μF R3 4.7Ω R1 232kΩ R2 31.6kΩ VOUT EP C6 0.1μF Ordering Information PART NUMBER MODE OF OPERATION PIN-PACKAGE MAX17662BATE+ PWM, DCM 16 TQFN + Denotes a lead(Pb)-free/RoHS-compliant package. www.maximintegrated.com Maxim Integrated | 22 MAX17662 3.5V to 36V, 2A, High-Efficiency, Synchronous Step-Down DC-DC Converter Revision History REVISION NUMBER REVISION DATE 0 7/19 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. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2020 Maxim Integrated Products, Inc.