MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter General Description The MAX16961 is a high-efficiency, synchronous stepdown converter that operates with a 2.7V to 5.5V input voltage range and provides a 0.8V to 3.6V output voltage range. The wide input/output voltage range and the ability to provide up to 3A to load current make this device ideal for on-board point-of-load and post-regulation applications. The device achieves -3.7%/+2.6% output error over load, line, and temperature ranges. The device features a 2.2MHz fixed-frequency PWM mode for better noise immunity and load transient response, and a pulse-frequency modulation mode (skip) for increased efficiency during light-load operation. The 2.2MHz frequency operation allows for the use of allceramic capacitors and minimizes external components. The optional spread-spectrum frequency modulation minimizes radiated electromagnetic emissions. Integrated low RDSON switches improve efficiency at heavy loads and make the layout a much simpler task with respect to discrete solutions. The device is offered with factory-preset output voltages or with an adjustable output voltage. (See the Selector Guide for options). Factory-preset output-voltage versions allow customers to achieve -3.7%/+2.6% output-voltage accuracy without using external resistors, while the adjustable output-voltage version provides the flexibility to set the output voltage to any desired value between 0.8V to 3.6V using an external resistive divider. Benefits and Features S Small External Components 2.2MHz Operating Frequency S Ideal for Point-of-Load Applications 3A Maximum Load Current Adjustable Output Voltage: 0.8V to 3.6V 2.7V to 5.5V Operating Supply Voltage S High Efficiency at Light Load 26µA Skip Mode Quiescent Current S Minimizes Electromagnetic Interference Programmable SYNC I/O Pin Operates Above AM-Radio Band Available Spread Spectrum S Low Power Mode Saves Energy 1µA Shutdown Current S Open-Drain Power-Good Output S Limits Inrush Current During Startup Soft-Start S Overtemperature and Short-Circuit Protections S 16-Pin TSSOP-EP and 16-Pin (4mm x 4mm) TQFN-EP Packages S -40°C to 125°C Operating Temperature Range Applications Automotive Infotainment Point-of-Load Applications Additional features include 8ms soft-start, 16ms powergood output delay, overcurrent, and overtemperature protections. The MAX16961 is available in thermally enhanced 16-pin TSSOP-EP and 16-pin (4mm x 4mm) TQFNEP packages, and is specified for operation over the -40NC to +125NC automotive temperature range. Industrial/Military Typical Application Circuit VPV1 PV1 4.7µF OUTS 0.47µH PV2 Ordering Information appears at end of data sheet. EN LX2 PGND1 For related parts and recommended products to use with this part, refer to www.maximintegrated.com/MAX16961.related. VPV PGND2 10Ω PV 1µF GND VOUT1 LX1 MAX16961 EP 47µF VOUT1 20kΩ PG For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com. 19-6520; Rev 3; 5/14 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter ABSOLUTE MAXIMUM RATINGS PV, PV1, PV2 to GND...............................................-0.3V to +6V EN, PG to GND........................................................-0.3V to +6V PGND1 and PGND2 to GND ...............................-0.3V to +0.3V LX1, LX2 Continuous RMS Current (LX1 connected in Parallel with LX2)....................................4A LX Current (LX1 connected in Parallel with LX2).....Q6A (Note 5) All Other Pins Voltages to GND... (VPV + 0.3V) to (VGND - 0.3V) Output Short-Circuit Duration.....................................Continuous Continuous Power Dissipation (TA = +70NC) TQFN (derate 25mW/NC above +70NC)................... 2000mW* TSSOP (derate 26.1mW/NC above +70NC)........... 2088.8mW* Operating Temperature Range......................... -40NC to +125NC Junction Temperature......................................................+150NC Storage Temperature Range............................. -65NC to +150NC Lead Temperature (soldering, 10s).................................+300NC Soldering Temperature (reflow).......................................+260NC *As per JEDEC51 Standard (multilayer board). Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. PACKAGE THERMAL CHARACTERISTICS (Note 1) TQFN Junction-to-Ambient Thermal Resistance (BJA)...........40NC/W Junction-to-Case Thermal Resistance (BJC)..................6NC/W TSSOP Junction-to-Ambient Thermal Resistance (BJA).....38.3NC/W Junction-to-Case Thermal Resistance (BJC)...............3NC/W Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial. ELECTRICAL CHARACTERISTICS (VPV = VPV1 = VPV2 = 5V, VEN = 5V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2) PARAMETER Supply Voltage Range Supply Current Shutdown Supply Current SYMBOL CONDITIONS MIN VPV Normal operation 2.7 IPV No load, VPWM = 0V 12 ISHDN Undervoltage-Lockout Threshold Low VUVLO_L Undervoltage-Lockout Threshold High VUVLO_H VEN = 0V, TA = +25°C TYP MAX UNITS 5.5 V 26 45 FA 1 5 FA 2.37 V 2.6 Undervoltage-Lockout Hysteresis V 0.07 V 800 mV SYNCHRONOUS STEP-DOWN DC-DC CONVERTER FB Regulation Voltage VOUTS Feedback Set-Point Accuracy VOUTS ILOAD = 4A -3 0 +3 ILOAD = 0A -0.5 +2 +3 % pMOS On-Resistance RDSON_P VPV1 = 5V, ILX_ = 0.4A, LX1 in parallel with LX2 34 55 mI nMOS On-Resistance RDSON_N VPV1 = 5V, ILX_ = 0.8A, LX1 in parallel with LX2 25 45 mI 5.1 6.3 A Maximum pMOS Current-Limit Threshold Maxim Integrated ILIMP1 LX1 and LX2 shorted together 3.9 2 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter ELECTRICAL CHARACTERISTICS (continued) (VPV = VPV1 = VPV2 = 5V, VEN = 5V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2) PARAMETER Maximum Output Current SYMBOL IOUT OUTS Bias Current IB_OUTS LX_ Leakage Current ILX_LEAK Minimum On-Time tON_MIN LX Discharge Resistance RLX CONDITIONS (VOUT + 0.5V P VPV1 P 5.5V) (Note 3) MIN TYP MAX 3.3 UNITS A Fixed output voltage variants 1 Adjustable output version -1 2 +1 5 VPV_ = 5V, LX_ = PGND_ or PV_, TA = +25°C -1 +1 VEN = 0V, through the OUTS pin 15 60 24 Maximum Short-Circuit Current FA FA ns 55 I 7.8 A 2.4 MHz 2.4 MHz OSCILLATOR Oscillator Frequency Spread Spectrum SYNC Input Frequency Range fSW Internally generated Df/f Spread spectrum enabled fSYNC 50% duty cycle (Note 4) 2.0 2.2 +6 1.7 % THERMAL OVERLOAD Thermal-Shutdown Threshold +165 °C Thermal-Shutdown Hysteresis 15 °C POWER-GOOD OUTPUT (PG) PG Overvoltage Threshold PGOVTH Percentage of nominal output 106 110 114 % PG Undervoltage Threshold PGUVTH Percentage of nominal output 90 92 94 % PG Timeout Period 16 ms Undervoltage-/OvervoltagePropagation Delay 28 Fs Output High Leakage Current PG Output Low Voltage TA = +25°C 0.2 ISINK = 3mA 0.4 VPV = 1.2V, ISINK = 100FA 0.4 FA V ENABLE INPUTS (EN) Input Voltage High VINH Input rising Input Voltage Low VINL Input falling 2.4 Input Hysteresis V 0.5 V 0.85 V Input Current VEN = high 0.1 1.0 2 FA Pulldown Resistor VEN = low 50 100 200 kI DIGITAL INPUTS (PWM, SYNC AS INPUT) Input Voltage High VINH Input Voltage Low VINL 1.8 0.4 Input Voltage Hysteresis Pulldown Resistor Maxim Integrated V 50 50 100 V mV 200 kI 3 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter ELECTRICAL CHARACTERISTICS (continued) (VPV = VPV1 = VPV2 = 5V, VEN = 5V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.4 V DIGITAL OUTPUT (SYNC AS OUTPUT) Output-Voltage Low VOL ISINK = 3mA Output-Voltage High VOH VPV = 5V, ISOURCE = 3mA Note Note Note Note 2: 3: 4: 5: 4.2 V All limits are 100% production tested at +25°C. Limits over temperature are guaranteed by design. Calculated value based on an assumed inductor current ripple of 30%. For SYNC frequency outside (1.7, 2.4) MHz, contact factory. LX_ has internal clamp diodes to PGND_ and IN_. Applications that forward bias these diodes should take care not to exceed the IC’s package power dissipation limits. Typical Operating Characteristics (VPV = VPV1 = 5V, VEN = 5V, TA = +25°C, unless otherwise noted.) VOUT = 2.5V 60 VOUT = 1.8V 40 30 50 40 VOUT = 1.8V 30 VOUT = 1.2V 20 VOUT = 3.3V 60 0.1000 1.0000 0 0.0010 10.0000 0.0100 VOUT = 1.2V VOUT = 2.5V 40 30 VIN = 3.3V 0.0010 0.0100 0.1000 LOAD CURRENT (A) Maxim Integrated 1.0000 MAX16961 toc03 VIN = 5V 0 10.0000 0.001 -0.50 -1.50 TA = -40°C -2.50 1.0000 10.0000 1.000 10.000 1 VIN = 5V VOUT = 3.3V 0 -1 -2 -3 TA = -40°C -4 TA = +25°C -3.50 0.100 VOUT LOAD REGULATION (SKIP) -1.00 -2.00 0.010 LOAD CURRENT (A) VIN = 5V VOUT = 3.3V -3.00 20 0 0.0001 0.1000 0 REGULATION (%) EFFICIENCY (%) 80 10 10 0.50 MAX16961 toc04 90 50 VOUT = 1.2V VOUT LOAD REGULATION (PWM) EFFICIENCY vs. LOAD CURRENT (SKIP) 60 40 LOAD CURRENT (A) 100 VOUT = 1.8V VOUT = 1.8V 50 0 ILOAD (A) 70 60 20 VOUT = 1.2V 10 0.0100 VOUT = 3.3V 70 30 20 10 0 0.0010 80 REGULATION (%) 50 70 90 MAX16961 toc05 70 80 EFFICIENCY (%) EFFICIENCY (%) 80 VIN = 5V 90 EFFICIENCY (%) VIN = 3.3V 100 MAX16961 toc02 MAX16961 toc01 90 EFFICIENCY vs. LOAD CURRENT (SKIP) EFFICIENCY vs. LOAD CURRENT (PWM) 100 TA = +25°C -5 TA = +125°C -4.00 MAX16961 toc06 EFFICIENCY vs. LOAD CURRENT (PWM) 100 TA = +125°C -6 0 0.5 1.0 1.5 ILOAD (A) 2.0 2.5 3.0 0 0.5 1.0 1.5 2.0 2.5 3.0 ILOAD (A) 4 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) VOUT vs. VPV (PWM) IPV vs. VPV (SKIP) 1.83 TA = -40°C 1.81 30 TA = +25°C 1.80 1.79 1.77 1.75 34 3.1 3.5 3.9 4.3 4.7 5.1 5.5 TA = -40°C 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VPV (V) VPV (V) IPV vs. TEMPERATURE (SKIP) LOAD-TRANSIENT RESPONSE (PWM) MAX16961 toc10 MAX16961 toc09 VPV = 5V VPWM = 0V VEN1 = VPV VOUT = 0.9V VIN = 3.3V 3.0A 32 IPV (µA) TA = +25°C 10 2.7 36 25 15 TA = +125°C 1.76 38 TA = +125°C 20 1.78 40 VPWM = 0V VEN1 = VEN2 = VPV VOUT1 = VOUT2 = 0.8V 35 IPV (µA) VOUT (V) 1.82 MAX16961 toc08 ILOAD = 0A 1.84 40 MAX16961 toc07 1.85 0.30A 0A ILOAD 30 28 VOUT AC-COUPLED 26 50mV/div 24 22 20 100µs/div -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) SHDN CURRENT vs. VPV fSW vs. TEMPERATURE VIN = 5V PWM MODE 2.16 100 TA = +125°C 10 2.12 SHDN (nA) fSW (MHz) 2.14 2.10 2.08 1 0.1 2.06 2.04 TA = +25°C 0.01 2.02 TA = -40°C 0.001 2.00 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) Maxim Integrated MAX16961 toc12 2.18 1000 MAX16961 toc11 2.20 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VPV (V) 5 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter SYNC PWM GND TOP VIEW PV Pin Configurations 12 11 10 9 TOP VIEW 8 GND 13 7 GND 14 PG OUTS MAX16961 GND 15 EP 2 3 4 LX1 LX2 1 5 PGND1 + PGND2 PV2 16 6 EN PV1 GND 1 PV2 + 16 GND 2 15 GND LX2 3 14 PV PGND2 4 13 SYNC PGND1 5 LX1 6 PV1 7 EN 8 MAX16961 EP 12 PWM 11 GND 10 PG 9 OUTS TSSOP TQFN (4mm x 4mm) Pin Descriptions PIN NAME FUNCTION TQFN TSSOP 1 3 LX2 2 4 PGND2 Power Ground 2 3 5 PGND1 Power Ground 1 4 6 LX1 Switching Node 1. LX1 is high impedance when the converter is off. 5 7 PV1 Input Supply 1. Bypass PV1 with at least a 4.7FF ceramic capacitor to PGND1. Connect PV1 to PV2 for normal operation. 6 8 EN Enable Input. Drive EN high to enable the converter. Drive EN low to disable the converter. 7 9 OUTS Feedback Input (Adjustable Output Option Only). Connect an external resistive divider from VOUT to OUTS and GND to set the output voltage. See Figure 2. 8 10 PG 9, 13–15 1, 11, 15, 16 GND Ground 10 12 PWM PWM Control Input. Drive PWM high to put the converters in forced-PWM mode. Drive PWM low to put the converters in skip mode. 11 13 SYNC Factory-Set Sync Input or Output. As an input, SYNC accepts a 1.7MHz to 2.4MHz external clock signal. As an output, SYNC outputs a 90° phase-shifted signal with respect to internal oscillator. Maxim Integrated Switching Node 2. LX2 is high impedance when the converter is off. Power-Good Output. Open-drain output. PG asserts when VOUT drops below 8% or rises above 10% of the nominal output voltage. Connect to a 20kI pullup resistor. 6 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter Pin Descriptions (continued) PIN NAME FUNCTION 14 PV Device Supply Voltage Input. Bypass with at least a 1FF ceramic capacitor to GND. In addition, connect a 10I decoupling resistor between PV and the bypass capacitor. 16 2 PV2 Input Supply 2. Bypass PV2 with at least a 4.7FF ceramic capacitor to PGND2. Connect PV2 to PV1 for normal operation. — — EP Exposed Pad. Connect EP to a large-area contiguous copper ground plane for effective power dissipation. Do not use EP as the only IC ground connection. EP must be connected to GND. TQFN TSSOP 12 Detailed Description The MAX16961 is a high-efficiency, synchronous stepdown converter that operates with a 2.7V to 5.5V input voltage range and provides a 0.8V to 3.6V output voltage range. The device delivers up to 3A of load current and achieves -3.7%/+2.6% output error over load, line, and temperature ranges. The PWM input forces the device into either a fixedfrequency, 2.2MHz PWM mode or a low-power pulsefrequency modulation mode (skip). Optional spreadspectrum frequency modulation minimizes radiated electromagnetic emissions due to the switching frequency. The factory-programmable synchronization I/O (SYNC) enables system synchronization. Integrated low RDSON switches help improve efficiency at heavy loads and make the layout a much simpler task with respect to discrete solutions. The device is offered with factory-preset output voltages that achieve -3.7%/+2.6% output-voltage accuracy without using external resistors. In addition, the output voltage can be set to any desired values between 0.8V to 3.6V using an external resistive divider wth the adjustable option. Additional features include 8ms soft-start, 16ms powergood delay output, overcurrent, and overtemperature protections. See Figure 1. Power-Good Output (PG) The device features an open-drain power-good output that asserts when the output voltage drops 8% below or rises 10% above the regulated voltage. PG remains asserted for a fixed 16ms timeout period after the output rises up to its regulated voltage. Connect PG to OUTS with a 20kI resistor. Maxim Integrated Soft-Start The device includes an 8ms fixed soft-start time. Soft-start time limits startup inrush current by forcing the output voltage to ramp up over time towards its regulation point. Spread-Spectrum Option The device featuring spread-spectrum (SS) operation varies the internal operating frequency up by SS = 6% relative to the internally generated operating frequency of 2.2MHz (typ). This function does not apply to externally applied oscillation frequency. The internal oscillator is frequency modulated with a 6% frequency deviation. See the Selector Guide for available options. Synchronization (SYNC) SYNC is a factory-programmable I/O. See the Selector Guide for available options. When SYNC is configured as an input, a logic-high on PWM enables SYNC to accept signal frequency in the range of 1.7MHz < fSYNC < 2.4MHz. When SYNC is configured as an output, a logic-high on PWM enables SYNC to output a 90N phaseshifted signal with respect to internal oscillator. Current-Limit/Short-Circuit Protection The device features current limit that protects the device against short-circuit and overload conditions at the output. In the event of a short-circuit or overload condition, the high-side MOSFET remains on until the inductor current reaches the high-side MOSFET’s current-limit threshold. The converter then turns on the low-side MOSFET to allow the inductor current to ramp down. Once the inductor current crosses the low-side MOSFET current-limit threshold, the converter turns on the highside MOSFET for minimum on-time period. This cycle repeats until the short or overload condition is removed. 7 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter CURRENT-SENSE AMP PV PV1 MAX16961 SKIP CURRENT COMP PV2 PV1 CLK PEAK CURRENT COMP RAMP GENERATOR CONTROL LOGIC STEP-DOWN Σ PGND LX1 LX2 PV PMW COMP PWM PGND PGND2 VREF SOFT-START GENERATOR ERROR AMP ZERO-CROSSING COMP FPWM CLK PGND1 CURRENT LIM COMP OUTS OSC. SYNC POWER-GOOD COMP P1-OK FEEDBACK DRIVER CLK FPWM OTP VOLTAGE REFERENCE TH-SD P1-OK EN TRIM BITS VREF PG MAIN CONTROL LOGIC GND Figure 1. Internal Block Diagram FPWM/Skip Modes The device features an input (PWM) that puts the converter either in skip mode or forced-PWM (FPWM) mode of operation. See the Pin Descriptions section for mode details. In FPWM mode, the converter switches at a constant frequency with variable on-time. In skip mode, the converter’s switching frequency is load-dependent until the output load reaches the skip threshold. At higher load current, the switching frequency does not change and the operating mode is similar to the FPWM mode. Skip mode helps improve efficiency in light-load applications by allowing the converters to turn on Maxim Integrated the high-side switch only when needed to maintain regulation. As such, the converter does not switch MOSFETs on and off as often as is the case in the FPWM mode. Consequently, the gate charge and switching losses are much lower in skip mode. Overtemperature Protection Thermal overload protection limits the total power dissipation in the device. When the junction temperature exceeds +165°C (typ), an internal thermal sensor shuts down the internal bias regulator and the step-down controller, allowing the IC to cool. The thermal sensor turns on the IC again after the junction temperature cools by 15°C. 8 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter Table 1. Inductor Values vs. (VIN - VOUT) VIN - VOUT (V) 5.0 to 3.3 5.0 to 2.5 5.0 to 1.5 3.3 to 0.8 INDUCTOR (µH) 0.8 0.6 0.47 0.33 inductor saturation current (ISAT), and DC resistance (RDCR). Use the following formulas to determine the minimum inductor value: VOUT R1 C1 MAX16962 OUTS R2 Figure 2. Adjustable Output Voltage Setting V 3 L MIN = )× (VIN − VOUT_ ) × ( OUT_ VIN fOP × 3A where fOP is the operating frequency. This value is 2.2MHz unless externally synchronized to a different frequency. The next equation ensures that the inductor current downslope is less than the internal slope compensation. For this to be the case, the following equation needs to be satisfied: −m ≥ Applications Information Setting the Output Voltage Connect OUTS to VOUT for factory-programmed output voltage (see the Selector Guide). To set the output to other voltages between 0.8V and 3.6V, connect a resistive divider from output (VOUT) to OUTS to GND (Figure 2). Select R2 (OUTS to GND resistor) less than or equal to 100kI. Calculate R1 (VOUT to OUTS resistor) with the following equation: V R1 R2 OUT − 1 = V OUTS where VOUTS = 800mV (see the Electrical Characteristics table). The external feedback resistive divider must be frequency compensated for proper operation. Place a capacitor across each resistor in the resistive-divider network. Use the following equation to determine the value of the capacitors: R2 C1 = 10pF R1 Inductor Selection Three key inductor parameters must be specified for operation with the MAX16961: inductance value (L), Maxim Integrated m2 2 where m2 is the inductor current downslope: VOUT L and -m is the slope compensation: 0.8 xIMAX µs Solving for L: L MIN2 = VOUT × µs 1.6 × 3A The equation that provides the bigger inductor value must be chosen for proper operation: LMIN = max(LMIN1, LMIN2) The maximum inductor value recommended is twice the chosen value from the above formula. LMAX = 2 x LMIN The maximum inductor value must not exceed the calculated value from the above formula. This ensures that the current feedback loop receives the correct amount of current ripple for proper operation. 9 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter Input Capacitor small footprint be placed close to PV. Using a small footprint such as 0805 or smaller helps to reduce the total parasitic inductance. The input capacitor RMS current requirement (IRMS) is defined by the following equation: The minimum capacitor required depends on output voltage, maximum device current capability, and the error-amplifier voltage gain. Use the following formula to determine the required output capacitor value: 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. IRMS = ILOAD(MAX) VOUT (VPV1 − VOUT ) VPV1 Output Capacitor 3A × G EAMP 3A × 40 C OUT(MIN) = IRMS has a maximum value when the input voltage = 2π × fCO × VOUT 2π × 250kHz × VOUT equals twice the output voltage (VPV1 = 2VOUT), so IRMS(MAX) = ILOAD(MAX)/2. where fCO, the target crossover frequency, is 250kHz, Choose an input capacitor that exhibits less than +10NC and GEAMP, the error-amplifier voltage gain, is 40V/V. self-heating temperature rise at the RMS input current for Table 2 lists some of the inductor values for 3A output optimal long-term reliability. current and several output voltages. For proper functionThe input-voltage ripple is composed of DVQ (caused ality, ceramic capacitors must be used. Make sure that by the capacitor discharge) and DVESR (caused by the the self-resonance of the ceramic capacitors at the conESR of the capacitor). Use low-ESR ceramic capacitors verter output is above 1MHz to avoid converter instability. with high ripple-current capability at the input. Assume PCB Layout Guidelines the contribution from the ESR and capacitor discharge Careful PCB layout is critical to achieve low switching equal to 50%. Calculate the input capacitance and ESR losses and clean, stable operation. Use a multilayer required for a specified input voltage ripple using the board whenever possible for better noise immunity and following equations: power dissipation. Follow these guidelines for good PCB ∆VESR ESRIN = layout: ∆I I OUT + L 1) Use a large contiguous copper plane under the 2 device package. Ensure that all heat-dissipating where: components have adequate cooling. The bottom (VPV1 − VOUT ) × VOUT ∆IL = pad of the device must be soldered down to this VPV1 × fSW × L copper plane for effective heat dissipation and and: maximizing the full power out of the device. Use I × D(1 − D) V CIN = OUT and D = OUT multiple vias or a single large via in this plane for ∆VQ × fSW VPV1 heat dissipation. where IOUT is the maximum output current, and D is the duty cycle. It is strongly recommended that a 4.7FF small footprint be placed close to PV1 and PV2 and a minimum of 100nF 2) Isolate the power components and high-current path from the sensitive analog circuitry. This is essential to prevent any noise coupling into the analog signals. Table 2. Output Capacitor Values vs. VOUT Setting VOUT (V) 3.3 2.5 1.5 0.8 COUT (µF), IMAX = 3.0A ≥ 23 ≥ 31 ≥ 51 ≥ 95 Maxim Integrated 10 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter 3) Add small footprint blocking capacitors with low selfresonance frequency close to PV1, PV2, and PV. 4) Keep the high-current paths short, especially at the ground terminals. This practice is essential for stable, jitter-free operation. The high-current path composed of input capacitors at PV1, PV2, inductor, and the output capacitor should be as short as possible. 5) Keep the power traces and load connections short. This practice is essential for high efficiency. Use thick copper PCBs (2oz vs. 1oz) to enhance full-load efficiency. 6) OUTS is sensitive to noise for devices with external feedback option. The resistive network (R1 and R2) and the capacitive network (C1 and C2) must be placed close to OUTS and far away from the LX_ node and high switching current paths. The ground node of R2 and C2 must be close to GND. 7) The ground connection for the analog and power section should be close to the IC. This keeps the ground current loops to a minimum. In cases where only one ground is used enough isolation between analog return signals and high power signals must be maintained. Ordering Information TEMP RANGE LOAD CURRENT CAPABILITY (A) MAX16961_ATE_/V+ PART -40°C to +125°C 4 PIN-PACKAGE 16 TQFN-EP* MAX16961_AUE_/V+ -40°C to +125°C 4 16 TSSOP-EP* Note: “_” is a package suffix placeholder for either “R” or “S”, as shown in the Selector Guide. The 2nd “_” is in the option suffix. /V denotes an automotive qualified part. +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. Selector Guide PACKAGE SUFFIX OPTION SUFFIX OUTPUT VOLTAGE SPREAD SPECTRUM SYNC IN/OUT MAX16961 RAUE A/V+ Ext. Adj. Disabled In MAX16961 MAX16961 MAX16961 SAUE RATE SATE A/V+ A/V+ A/V+ Ext. Adj. Ext. Adj. Ext. Adj. Enabled Disabled Enabled In In In ROOT PART Note: Contact the factory for variants with different output-voltage, spread-spectrum, and power-good delay time settings. Chip Information PROCESS: BiCMOS Maxim Integrated Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 16 TQFN-EP T1644+4 21-0139 90-0070 16 TSSOP-EP U16E+3 21-0108 90-0120 11 MAX16961 3A, 2.2MHz, Synchronous Step-Down DC-DC Converter Revision History REVISION NUMBER REVISION DATE 0 11/12 Initial release — 1 4/13 Added non-automotive parts to Selector Guide 11 2 9/13 Updated input voltage high min spec and input voltage low max spec, Figure 2, equation, step 6 in the PCB Layout Guidelines section, and the Ordering Information 3–5, 10, 11 3 5/14 Added FB regulation voltage specifications and updated VPV condition in Electrical Characteristics table; corrected equations and updated Table 2 in the Inductor Selection and Output Capacitor sections; updated Ordering Information 2, 3, 9–11 DESCRIPTION PAGES CHANGED 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 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 © 2014 Maxim Integrated Products, Inc. 12 Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.