MAX20003CATPD/V+T

EVALUATION KIT AVAILABLE Click here to ask about the production status of specific part numbers. MAX20002/MAX20003 General Description The MAX20002/MAX20003 are small, synchronous buck converters with integrated high-side and low-side MOSFETs. Each device is designed to deliver up to 2A/3A with input voltages from 3.5V to 36V, while using only 15µA quiescent current at no load. Voltage quality can be monitored by observing the PGOOD signal. The devices can operate in dropout by running at 98% duty cycle, making them ideal for automotive applications. The devices offer fixed output voltages of 5V/3.3V, along with the ability to program the output voltage between 1V to 10V. Frequency can be programmed using a resistor to ground on the FOSC pin from 220kHz to 2.2MHz. The devices offer a forced fixed-frequency mode and skip mode with ultra-low quiescent current of 15µA. They have a pin that can be programmed to turn on/off the spread spectrum, further helping systems designers with better EMC management. The MAX20002/MAX20003 are available in a small 5mm x 5mm 20-pin TQFN package with exposed pad and use very few external components. Applications ● Point-of-Load Applications in Automotive ● Distributed DC Power Systems ● Navigation and Radio Head Units 19-7311; Rev 17; 7/20 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Benefits and Features ● Synchronous DC-DC Converter with Integrated FETs • MAX20002 = 2A • MAX20003 = 3A • 15µA Quiescent Current When in Skip Mode ● Small Solution Size Saves Space • 220kHz to 2.2MHz Adjustable Frequency • Programmable 1V to 10V Output for the Buck or Fixed 5V/3.3V Options Available • Fixed 8ms Internal Soft-Start • Fixed Output Voltage with ±2% Output Accuracy (5V/3.3V) or Externally Resistor Adjustable (1V to 10V) with ±1% FB Accuracy ● PGOOD Output and High-Voltage EN Input Simplify Power Sequencing ● Protection Features and Operating Range Ideal for Automotive Applications • Operating VIN Range of 3.5V to 36V • 42V Load-Dump Protection • 99% Duty-Cycle Operation with Low Dropout • -40°C to +125°C Automotive Temperature Range • AEC-Q100 Qualified • Fast and Accurate Overvoltage Protection Enables Fast Recovery from Automotive Transients (MAX20002C/E and MAX20003C/E) Ordering Information appears at end of data sheet. MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Typical Application Circuit/Block Diagram 2.2µH 2 x 22µF LX LX LX N.C. FSYNC 0.1µF VOUT = 3.3V/5V AT 3A, 2.2MHz FOSC BST OUT PGND 12kΩ MAX20002 MAX20003 FB PGND SPS COMP 20.0kΩ 4.7µF www.maximintegrated.com SUPSW SUPSW EN EP AGND 1,000pF SUP PGOOD BIAS 2.2µF 2.2µF VBAT Maxim Integrated │  2 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Absolute Maximum Ratings SUP, SUPSW, LX, EN to PGND............................-0.3V to +42V SUP to SUPSW.....................................................-0.3V to +0.3V BIAS to AGND..........................................................-0.3V to +6V SPS, FOSC, COMP to AGND.................-0.3V to (VBIAS + 0.3V) FSYNC, PGOOD, FB to AGND...............-0.3V to (VBIAS + 0.3V) OUT to PGND........................................................-0.3V to +12V BST to LX.................................................................-0.3V to +6V AGND to PGND.....................................................-0.3V to +0.3V Output Short-Circuit Duration.....................................Continuous Continuous Power Dissipation (TA = +70°C) 20-Pin TQFN (derate 33.3mW/°C above +70°C) ...2666.7mW Operating Temperature Range.......................... -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 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 PACKAGE TYPE: 20 TQFN Package Code T2055+4C Outline Number 21-0140 Land Pattern Number 90-0009 PACKAGE TYPE: 20 SW TQFN Package Code T2055Y+4C Outline Number 21-100165 Land Pattern Number 90-100065 THERMAL RESISTANCE, FOUR-LAYER BOARD Junction to Ambient (θJA) 30°C/W Junction to Case (θJC) 2°C/W . For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial. Electrical Characteristics (VSUP = VSUPSW = 14V, VEN = 14V, L1 = 2.2µH, CIN = 4.7µF, COUT = 44µF, CBIAS = 2.2µF, CBST = 0.1µF, RFOSC = 12kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL Supply Voltage VSUP, VSUPSW Load-Dump Event Supply Voltage VSUP_LD Supply Current Shutdown Supply Current BIAS Regulator Voltage BIAS Undervoltage Lockout www.maximintegrated.com CONDITIONS MIN TYP 3.5 tLD < 1s MAX UNITS 36 V 42 V Skip mode, no load, VOUT = 3.3V, VFSYNC = 0V 15 30 µA Skip mode, no load, VOUT = 5V, VFSYNC = 0V 20 35 µA ISHDN VEN = 0V 5 10 µA VBIAS VSUP = VSUPSW = 6V to 42V, IBIAS = 0 to 10mA 4.7 5 5.4 V VBIAS rising 2.9 3.15 3.4 V ISUP VUVBIAS Maxim Integrated │  3 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Electrical Characteristics (continued) (VSUP = VSUPSW = 14V, VEN = 14V, L1 = 2.2µH, CIN = 4.7µF, COUT = 44µF, CBIAS = 2.2µF, CBST = 0.1µF, RFOSC = 12kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) TYP MAX UNITS BIAS Undervoltage-Lockout Hysteresis PARAMETER SYMBOL CONDITIONS MIN 400 500 mV Thermal-Shutdown Threshold 175 °C Thermal-Shutdown Threshold Hysteresis 15 °C OUTPUT VOLTAGE PWM-Mode Output Voltage (Note 1) Skip-Mode Output Voltage (Note 2) VOUT_5V VOUT_3.3V VOUT_ SKIP_5V VOUT_ VFB = VBIAS, 6V < VSUPSW < 36V, fixed-frequency mode 4.9 5 5.1 3.23 3.3 3.37 4.9 5 5.15 No load, VFB = VBIAS, skip mode V 3.23 SKIP_3.3V V 3.3 3.4 Load Regulation VFB = VBIAS, 30mA < ILOAD < 3A 0.5 % Line Regulation VFB = VBIAS, 6V < VSUPSW < 36V 0.02 %/V IBST_ON High-side MOSFET on, VBST - VLX = 5V 1.5 mA IBST_OFF High-side MOSFET off, VBST - VLX = 5V 1.5 µA BST Input Current LX Current Limit ILX MAX20003: MAX20003C/EATPA/V+, MAX20003C/EATPB/V+, LX Rise Time MAX20002, MAX20002C, MAX20002E MAX20003CATPC/V+, MAX20003CATPD/V+ VOUT = 5V, 3.3V Spread Spectrum Spread spectrum enabled High-Side Switch OnResistance RON_H High-Side Switch Leakage Current Low-Side Switch OnResistance RON_L Low-Side Switch Leakage Current FB Input Current FB Regulation Voltage www.maximintegrated.com IFB VFB 3.75 5 6.25 2.5 3.33 4.16 A 5 4 ns FOSC ±3% ILX = 0.5A, VBIAS = 5V 60 140 mΩ High-side MOSFET off, VSUP = 36V, VLX = 0V, TA = +25°C 1 5 µA ILX = 0.5A, VBIAS = 5V 35 70 mΩ Low-side MOSFET off, VSUP = 36V, VLX = 36V, TA = +25°C 1 5 µA TA = +25°C 20 100 nA 1 1.01 FB connected to an external resistive divider, 6V < VSUPSW < 36V 0.99 FB connected to an external resistive divider, 6V < VSUPSW < 36V (MAX20002C/E, MAX20003C/E) 0.985 V 1 1.015 Maxim Integrated │  4 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Electrical Characteristics (continued) (VSUP = VSUPSW = 14V, VEN = 14V, L1 = 2.2µH, CIN = 4.7µF, COUT = 44µF, CBIAS = 2.2µF, CBST = 0.1µF, RFOSC = 12kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER FB Line Regulation Transconductance (from FB to COMP) SYMBOL CONDITIONS MIN TYP MAX UNITS ∆VLINE 6V < VSUPSW < 36V 0.02 %/V gM VFB = 1V, VBIAS = 5V 700 µS Minimum On-Time tON_MIN Maximum Duty Cycle DCMAX 80 98 RFOSC = 73.2kΩ Oscillator Frequency RFOSC = 12kΩ 99 400 2.0 2.2 ns % kHz 2.4 MHz SYNC, EN, AND SPS LOGIC THRESHOLDS External Input Clock Acquisition Time tFSYNC External Input Clock Frequency 1 RFOSC = 12kΩ (Note 3) External Input Clock High Threshold VFSYNC_HI VFSYNC rising External Input Clock Low Threshold VFSYNC_LO VFSYNC falling FSYNC Leakage Current Soft-Start Time 1.8 tSS 5.6 2.4 Enable Input Low Threshold VEN_LO IEN Spread-Spectrum Input High Threshold VSPS_HI Spread-Spectrum Input Low Threshold VSPS_LO Spread-Spectrum Input Current ISPS 8 0.4 V 1 µA 12 ms V 0.6 VEN_HYS 0.2 TA = +25°C 0.1 V V 1 2.0 TA = +25°C MHz V TA = +25°C VEN_HI Enable Input Current 2.6 1.4 Enable Input High Threshold Enable Threshold Voltage Hysteresis Cycle µA V 0.4 V 0.1 1 µA POWER-GOOD AND OVERVOLTAGE-PROTECTION THRESOLDS PGOOD Switching Level VRISING VFB rising, VPGOOD = high 93 95 97 VFALLING VFB falling, VPGOOD = low 90 92.5 95 PGOOD Debounce Time 25 PGOOD Output Low Voltage ISINK = 5mA PGOOD Leakage Current VOUT in regulation, TA = +25°C Overvoltage-Protection Threshold VOUT rising (monitor FB pin) 107 VOUT falling (monitor FB pin) 104 %VFB µs 0.4 V 1 µA % Note 1: Device not in dropout condition. Note 2: Guaranteed by design; not production tested. Note 3: Contact the factory for SYNC frequency outside the specified range. www.maximintegrated.com Maxim Integrated │  5 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Typical Operating Characteristics (VSUP = VSUPSW = 14V, VEN = 14V, VOUT = 5V, VFSYNC = 0V, RFOSC = 12kΩ, TA = +25°C, unless otherwise noted.) 80 80 70 3.3V 60 3.3V 50 5V 5V 40 SKIP MODE 30 0 0.0001 COILCRAFT XAL5030-222MEB 10 0.001 0.01 0.1 1 SKIP MODE LOAD REGULATION 0.001 SWITCHING FREQUENCY (MHz) VOUT (V) 5.00 4.95 400kHz 4.90 4.85 4.80 0.0 0.5 1.0 1.5 2.0 2.5 2.26 2.24 0.5 1.0 toc05 VIN = 14V, FPWM MODE toc07 2.20 2.18 2.16 2.14 VOUT = 3.3V 2.08 2.04 0.0 0.5 1.0 1.5 2.0 2.5 TEMPERATURE (°C) www.maximintegrated.com toc06 410 VOUT = 3.3V 405 400 395 390 385 0.0 0.5 1.0 1.5 2.0 2.5 3.0 ILOAD (A) SWITCHING FREQUENCY vs. RFOSC toc08 SUPPLY CURRENT vs. SUPPLY VOLTAGE 50 2.25 1.75 1.50 1.25 1.00 0.75 toc09 3.3V/2.2MHz SKIP MODE 45 2.00 40 35 30 25 20 0.50 0.00 3.0 415 375 3.0 15 0.25 -40 -25 -10 5 20 35 50 65 80 95 110 125 2.5 380 2.50 VOUT = 5V 2.0 VIN = 14V, FPWM MODE 420 SUPPLY CURRENT (µA) fSW vs. TEMPERATURE 1.5 fSW vs. LOAD CURRENT 425 ILOAD (A) 2.12 2.00 0.0 ILOAD (A) VOUT = 3.3V 2.22 2.10 3.0 2.20 2.16 4.80 10 2.12 SWITCHING FREQUENCY (MHz) SWITCHING FREQUENCY (MHz) 2.24 1 VIN = 14V, FPWM MODE ILOAD (A) 2.28 0.1 fSW vs. LOAD CURRENT 2.30 5.15 5.05 0.01 LOAD CURRENT (A) toc04 2.2MHz 400kHz 4.85 2.28 5.10 5.00 4.90 0 0.0001 10 2.2MHz 5.05 4.95 20 LOAD CURRENT (A) 5.20 FPWM MODE 5V 40 5.10 3.3V toc03 VOUT = 5V, VIN = 14V, SKIP MODE 5.15 3.3V 50 30 20 10 60 LOAD REGULATION 5.20 5V 70 FPWM MODE toc02 fSW = 400kHz, VIN =14V 90 EFFICIENCY (%) EFFICIENCY (%) 100 fSW = 2.2MHz VIN = 14V 90 EFFICIENCY vs. LOAD CURRENT VOUT (V) 100 toc01 SWITCHING FREQUENCY (MHz) EFFICIENCY vs. LOAD CURRENT 12 42 72 RFOSC (kΩ) 102 132 10 6 12 18 24 30 36 SUPPLY VOLTAGE (V) Maxim Integrated │  6 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Typical Operating Characteristics (continued) (VSUP = VSUPSW = 14V, VEN = 14V, VOUT = 5V, VFSYNC = 0V, RFOSC = 12kΩ, TA = +25°C, unless otherwise noted.) SHUTDOWN CURRENT vs. SUPPLY VOLTAGE 10 toc10 3.3V/2.2MHz SKIP MODE 9 SUPPLY CURRENT (µA) SHUTDOWN CURRENT (µA) 7 6 5 4 3 40 35 30 25 20 2 15 1 6 12 18 24 30 10 36 -40 -25 -10 5 20 35 50 65 80 95 110 125 SUPPLY VOLTAGE (V) TEMPERATURE (°C) SHUTDOWN CURRENT vs. TEMPERATURE 10 toc12 5.06 7 5.04 6 VBIAS (V) 5.02 5 5.00 4 4.98 3 2 4.96 1 4.94 4.92 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) TEMPERATURE (°C) VOUT vs. VIN 5.20 toc14 VOUT vs. VIN 5.20 5V/2.2MHz, ILOAD = 0A, FPWM MODE 5.15 5.05 VOUT (V) VOUT (V) 5.10 5.05 5.00 4.95 toc15 5V/2.2MHz PWM MODE ILOAD = 0A 5.15 5.10 5.00 4.95 4.90 4.90 4.85 4.85 4.80 toc13 VIN = 14V, ILOAD = 0A, FPWM MODE 5.08 8 SHUTDOWN CURRENT (µA) BIAS VOLTAGE vs. TEMPERATURE 5.10 3.3V/2.2MHz SKIP MODE 9 0 toc11 3.3V/2.2MHz SKIP MODE 45 8 0 SUPPLY CURRENT vs. TEMPERATURE 50 6 12 18 24 VIN (V) www.maximintegrated.com 30 36 4.80 6 12 18 24 30 VIN (V) 36 42 Maxim Integrated │  7 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Typical Operating Characteristics (continued) (VSUP = VSUPSW = 14V, VEN = 14V, VOUT = 5V, VFSYNC = 0V, RFOSC = 12kΩ, TA = +25°C, unless otherwise noted.) FULL-LOAD STARTUP BEHAVIOR SLOW VIN RAMP BEHAVIOR toc16 10V/div 0 VIN 100V/div 5V/div VOUT 0 1V/div 1A/div ILOAD 0 5V/div VPGOOD 0 VIN 0 5V/div 0 VOUT 1V/div 0 5V/div 2A/div 0 5V/div 0 ILOAD VPGOOD COLD CRANK toc19 10V/div VFSYNC 0 200ns 5V/2.2MHz VIN LOAD DUMP toc20 toc21 2V/div 0 5V/div VOUT 0 VLX 10V/div VIN VPGOOD 5V/div 2V/div VPGOOD 400ms LOAD TRANSIENT (PWM MODE) SHORT CIRCUIT (PWM MODE) toc22 LOAD TRANSIENT RESPONSE (MAX20003CATPD) toc24 toc23 5A 2V/div 500mV/div (ACCOUPLED) 0 5A/div ILX www.maximintegrated.com IOUT 2A 2A ILX 2A/div 2A/div 20V/div VLX 0 5V/div VPGOOD 0 0 100ms VOUT 100µs 5V/div 0 0 1A/div VOUT 5V/div 10ms VOUT 10V/div 0 VOUT 0 IOUT 10V/div VLX 4s VIN toc18 10V/div 100nF 2ms DIPS AND DROPS SYNC FUNCTION toc17 0 20ms VOUT ACRIPPLE 100mV/div 1ms Maxim Integrated │  8 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current BST PGND PGND SPS PGOOD Pin Configuration 15 14 13 12 11 LX 16 LX 17 MAX20002 MAX20003 LX 18 N.C. 19 FSYNC 20 2 3 4 OUT FB COMP SUP 9 SUPSW 8 SUPSW 7 EN 6 AGND 5 BIAS 1 FOSC EP* 10 TQFN (5mm x 5mm) *EP = EXPOSED PAD Pin Description PIN NAME 1 FOSC Resistor-Programmable Switching-Frequency-Setting Control Input. Connect a resistor from FOSC to AGND to set the switching frequency. 2 OUT Switching-Regulator Output. OUT also provides power to the internal circuitry when the output voltage of the converter is set between 3V to 5V during skip mode at very light load conditions after BIAS is switched over to buck output. 3 FB Feedback Input. Connect an external resistive divider from OUT to FB and AGND to set the output voltage. Connect to BIAS to set the output voltage to 5V or 3.3V. 4 COMP Error-Amplifier Output. Connect an RC network from COMP to AGND for stable operation. See the Compensation Network section for more details. 5 BIAS 6 AGND 7 EN SUP Voltage-Compatible Enable Input. Drive EN low to disable the devices. Drive EN high to enable the devices. 8, 9 SUPSW Internal High-Side Switch Supply Input. SUPSW provides power to the internal switch. Bypass SUPSW to PGND with a 0.1µF and 4.7µF ceramic capacitors. 10 SUP Voltage-Supply Input. SUP powers up the internal linear regulator. Bypass SUP to PGND with a 2.2µF ceramic capacitor. www.maximintegrated.com FUNCTION Linear Regulator Output. BIAS powers up the internal circuitry. Bypass with a minimum of 2.2µF ceramic capacitor to ground. Analog Ground Maxim Integrated │  9 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Pin Description (continued) PIN NAME FUNCTION 11 PGOOD Open-Drain, PGOOD Output. PGOOD asserts when VOUT is above 95% regulation point. PGOOD goes low when VOUT is below 92% regulation point. 12 SPS 13,14 PGND 15 BST 16–18 LX 19 N.C. 20 FSYNC — EP www.maximintegrated.com Spread-Spectrum Pin. Pull high for spread spectrum on and low for spread spectrum off. Power Ground High-Side Driver Supply. Connect a 0.1µF capacitor between LX and BST for proper operation. Inductor Switching Node No Connection Synchronization Input. The devices synchronize to an external signal applied to FSYNC. Connect FSYNC to AGND to enable skip mode operation. Connect to BIAS or to an external clock to enable fixed-frequency, forced-PWM mode operation. Do not leave the FSYNC pin unconnected. Exposed Pad. Connect EP to a large-area contiguous copper ground plane for effective power dissipation. Do not use as the only IC ground connection. EP must be connected to PGND. Maxim Integrated │  10 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current MAX20002 MAX20003 PGOOD OUT PGOOD HIGH LEVEL PGOOD LOW LEVEL PGOOD COMPARATOR BIAS SUP INTERNAL BIAS REGULATOR SWITCHOVER LOGIC FEEDBACK SELECT LOGIC FB EN PV SUPSW PV BST AGND INTERNAL SOFT-START PWM VREF = 1V CONTROL LOGIC EAMP LX PV COMP SPS PGND CLK FOSC SPREAD SPECTRUM ON/OFF FSYNC FSYNC SELECT LOGIC OSCILLATOR EXTERNAL CLOCK CONNECTED HI (PWM MODE) CONNECTED LO (SKIP MODE) SLOPE COMP LOGIC CURRENT-LIMIT THRESHOLD ZEROCROSSING COMPARATOR LX Figure 1. Internal Block Diagram www.maximintegrated.com Maxim Integrated │  11 MAX20002/MAX20003 Detailed Description The MAX20002/MAX20003 are 2A/3A current-mode stepdown converters with integrated high-side and lowside MOSFETs. The low-side MOSFET enables fixedfrequency, forced-PWM operation in light-load applications. The devices operate with input voltages from 3.5V to 36V while using only 15µA quiescent current at no load. The switching frequency is resistor programmable from 220kHz to 2.2MHz and can be synchronized to an external clock. The devices’ output voltage is available as 5V/3.3V fixed or adjustable from 1V to 10V. The wide input voltage range, along with its ability to operate at 99% duty cycle during undervoltage transients, makes the devices ideal for automotive applications. In light-load applications, a logic input (FSYNC) allows the devices to operate either in skip mode for reduced current consumption, or fixed-frequency, forced-PWM mode to eliminate frequency variation and help minimize EMI. Protection features include cycle-by-cycle current limit, and thermal shutdown with automatic recovery. See Figure 1 for an internal block diagram. Wide Input Voltage Range The devices include two separate supply inputs (SUP and SUPSW) specified for a wide 3.5V to 36V input voltage range. VSUP provides power to the device and VSUPSW provides power to the internal switch. When the device is operating with a 3.5V input supply, conditions such as cold crank can cause the voltage at the SUP and SUPSW pins to drop below the programmed output voltage. Under such conditions, the devices operate in a high duty-cycle mode to facilitate minimum dropout from input to output. The MAX20002E/MAX20003E provide additional filtering on the input inside the IC and are more robust against poor PCB layout; however, to get the best performance out of any version of the MAX20002/MAX20003, proper layout guidelines must be followed. Maximum Duty-Cycle Operation The devices have a maximum duty cycle of 98% (typ). The IC monitors the off-time (time for which the low-side FET is on) in both PWM and skip modes every switching cycle. Once the off time of 100ns (typ) is detected continuously for 12µs, the low-side FET is forced on for 150ns (typ) every 12µs. The input voltage at which the devices enter dropout changes depending on the input voltage, output voltage, switching frequency, load current, and the efficiency of the design. www.maximintegrated.com 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current The input voltage at which the devices enter dropout can be approximated as: VSUP = VOUT + (I OUT × R ON_H ) 0.98 Note: The previous equation does not take into account the efficiency and switching frequency but is a good firstorder approximation. Use the RON_H number from the maximum column in the Electrical Characteristics table. Linear Regulator Output (BIAS) The devices include a 5V linear regulator (VBIAS) that provides power to the internal circuit blocks. Connect a 2.2µF ceramic capacitor from BIAS to AGND. Power-Good Output (PGOOD) The devices feature an open-drain power-good output (PGOOD). PGOOD asserts when VOUT rises above 95% of its regulation voltage. PGOOD deasserts when VOUT drops below 92.5% of its regulation voltage. Connect PGOOD to BIAS with a 10kΩ resistor. Synchronization Input (FSYNC) FSYNC is a logic-level input useful for operating-mode selection and frequency control. Connecting FSYNC to BIAS or to an external clock enables fixed-frequency, forced-PWM operation. Connecting FSYNC to AGND enables skip-mode operation. The external clock frequency at FSYNC can be higher or lower than the internal clock by 20%. If the external clock frequency is greater than 120% of the internal clock, contact the factory applications team to verify the design. The devices synchronize to the external clock in two cycles. When the external clock signal at FSYNC is absent for more than two clock cycles, the devices use the internal clock. System Enable (EN) An enable control input (EN) activates the devices from their low-power shutdown mode. EN is compatible with inputs from automotive battery level down to 3.5V. The high-voltage compatibility allows EN to be connected to SUP, KEY/KL30, or the inhibit pin (INH) of a CAN transceiver. EN turns on the internal regulator. Once VBIAS is above the internal lockout threshold, VUVBIAS = 3.15V (typ), the converter activates and the output voltage ramps up within 8ms. Maxim Integrated │  12 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current A logic-low at EN shuts down the device. During shutdown, the internal linear regulator and gate drivers turn off. Shutdown is the lowest power state and reduces the quiescent current to 5µA (typ). Drive EN high to bring the devices out of shutdown. automotive conditions. Contact the Maxim Applications team to determine if the MAX20002C/E or MAX20003C/E are needed for your application. Spread-Spectrum Option Setting the Output Voltage The spread spectrum can be enabled on the device using a pin. When the SPS pin is pulled high the spread spectrum is enabled and the operating frequency is varied ±3% centered on FOSC. The modulation signal is a triangular wave with a period of 110μs at 2.2MHz. Therefore, FOSC ramps down 3% and back to 2.2MHz in 110μs and also ramps up 3% and back to 2.2MHz in 110μs. The cycle repeats. For operations at FOSC values other than 2.2MHz, the modulation signal scales proportionally (e.g., at 400kHz, the 110μs modulation period increases to 110μs x 2.2MHz/0.4MHz = 550μs). The internal spread spectrum is disabled if the devices are synchronized to an external clock. However, the devices do not filter the input clock on the FSYNC pin and pass any modulation (including spread spectrum) present on the driving external clock. Internal Oscillator (FOSC) The switching frequency (fSW) is set by a resistor (RFOSC) connected from FOSC to AGND. For example, a 400kHz switching frequency is set with RFOSC = 73.2kΩ. Higher frequencies allow designs with lower inductor values and less output capacitance. Consequently, peak currents and I2R losses are lower at higher switching frequencies, but core losses, gate-charge currents, and switching losses increase. Applications Information Connect FB to BIAS for a fixed +5V/3.3V output voltage. To set the output to other voltages between 1V and 10V, connect a resistive divider from output (OUT) to FB to AGND (Figure 2). Select RFB2 (FB to AGND resistor) less than or equal to 500kΩ. Calculate RFB1 (OUT to FB resistor) with the following equation:  V   R FB1 = R FB2  OUT  - 1  VFB   where VFB = 1V (see the Electrical Characteristics table). Forced-PWM and Skip Modes In PWM mode of operation, the devices switch at a constant frequency with variable on-time. In skip mode of operation, the converter’s switching frequency is load dependent. At higher load current, the switching frequency does not change and the operating mode is similar to the PWM mode. Skip mode helps improve efficiency in light-load applications by allowing the converters to turn on the high-side switch only when the output voltage falls below a set threshold. As such, the converters do not switch MOSFETs on and off as often as in the PWM mode. Consequently, the gate charge and switching losses are much lower in skip mode. VOUT Overtemperature Protection Thermal overload protection limits the total power dissipation in the device. When the junction temperature exceeds 175°C (typ), an internal thermal sensor shuts down the internal bias regulator and the step-down converter, allowing the IC to cool. The thermal sensor turns on the IC again after the junction temperature cools by 15°C. Overvoltage Protection (OVP) If the output voltage reaches the OVP threshold, the high-side switch is forced off and the low-side switch is forced on until the negative-current limit is reached. After negative-current limit is reached, both the high-side and low-side switches are turned off. The MAX20002C/E and MAX20003C/E feature an additional clamp and lower OVP threshold to limit the output-voltage overshoot for www.maximintegrated.com RFB1 MAX20002 MAX20003 FB RFB2 Figure 2. Adjustable Output-Voltage Setting Maxim Integrated │  13 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Inductor Selection Three key inductor parameters must be specified for operation with the devices: inductance value (L), inductor saturation current (ISAT), and DC resistance (RDCR). To select inductor value, the ratio of inductor peak-to-peak AC current to DC average current (LIR) must be selected first. A good compromise between size and loss is a 30% peak-to-peak ripple current to average-current ratio (LIR = 0.3). The switching frequency, input voltage, output voltage, and selected LIR then determine the inductor value as follows: L= (VSUP − VOUT ) × VOUT VSUP × f SW × I OUT × LIR where VSUP, VOUT, and IOUT are typical values (so that efficiency is optimum for typical conditions). The switching frequency is set by RFOSC (see TOC 8 in the Typical Operating Characteristics section). Input Capacitor 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 ILOAD(MAX) × VOUT x(VSUP - VOUT ) VSUP IRMS has a maximum value when the input voltage equals twice the output voltage: VSUP= 2 × VOUT therefore: IRMS = ILOAD(MAX) 2 Choose an input capacitor that exhibits less than +10°C self-heating temperature rise at the RMS input current for optimal long-term reliability. The input-voltage ripple is comprised of ΔVQ (caused by the capacitor discharge) and ΔVESR (caused by the ESR of the capacitor). Use low-ESR ceramic capacitors with high ripple-current capability at the input. Assume the contribution from the ESR and capacitor discharge equal to 50%. Calculate the input capacitance and ESR required for a specified input voltage ripple using the following equations: www.maximintegrated.com ESR IN = ∆VESR ∆I I OUT + L 2 where: (V - VOUT ) × VOUT ∆IL = SUP VSUP × f SW × L and: I × D(1- D) C IN = OUT ∆VQ × f SW D= VOUT VSUPSW where: IOUT is the maximum output current and D is the duty cycle. Output Capacitor The output filter capacitor must have low enough equivalent series resistance (ESR) to meet output-ripple and load-transient requirements. The output capacitance must be high enough to absorb the inductor energy while transitioning from full-load to no-load conditions without tripping the overvoltage-fault protection. When using high-capacitance, low-ESR capacitors, the filter capacitor’s ESR dominates the output-voltage ripple, so the size of the output capacitor depends on the maximum ESR required to meet the output-voltage ripple (VRIPPLE(P-P)) specifications: VRIPPLE(P-P) = ESR × ILOAD(MAX) × LIR The actual capacitance value required relates to the physical size needed to achieve low ESR, as well as to the chemistry of the capacitor technology. Thus, the capacitor is usually selected by ESR and voltage rating rather than by capacitance value. When using low-capacity filter capacitors, such as ceramic capacitors, size is usually determined by the capacity needed to prevent voltage droop and voltage rise from causing problems during load transients. Generally, once enough capacitance is added to meet the overshoot requirement, undershoot at the rising load edge is no longer a problem. However, low-capacity filter capacitors typically have highESR zeros that can affect the overall stability. Maxim Integrated │  14 MAX20002/MAX20003 36V, 220kHz to 2.2MHz, 2A/3A Fully Integrated Step-Down Converters with 15μA Operating Current Compensation Network The devices use an internal transconductance error amplifier with its inverting input and its output available to the user for external frequency compensation. The output capacitor and compensation network determine the loop stability. The inductor and the output capacitor are chosen based on performance, size, and cost. Additionally, the compensation network optimizes the control-loop stability. The converter uses a current-mode control scheme that regulates the output voltage by forcing the required current through the external inductor. The devices use the voltage drop across the high-side MOSFET to sense inductor current. Current-mode control eliminates the double pole in the feedback loop caused by the inductor and output capacitor, resulting in a smaller phase shift and requiring less elaborate error-amplifier compensation than voltage-mode control. Only a simple single series resistor (RC) and capacitor (CC) are required to have a stable, high-bandwidth loop in applications where ceramic capacitors are used for output filtering (see Figure 3). For other types of capacitors, due to the higher capacitance and ESR, the frequency of the zero created by the capacitance and ESR is lower than the desired closed-loop crossover frequency. To stabilize a nonceramic output-capacitor loop, add another compensation capacitor (CF) from COMP to ground to cancel this ESR zero. The basic regulator loop is modeled as a power modulator, output feedback divider, and an error amplifier. The power modulator has a DC gain set by gm × RLOAD, with a pole and zero pair set by RLOAD, the output capacitor (COUT), and its ESR. The following equations help to approximate the value for the gain of the power modulator (GAINMOD(dc)), neglecting the effect of the ramp stabilization. Ramp stabilization is necessary when the duty cycle is above 50% and is internally done for the devices: GAINMOD(dc) = g mc × R LOAD where RLOAD = VOUT/IOUT(MAX) in Ω and gmc = 3S. In a current-mode step-down converter, the output capacitor, its ESR, and the load resistance introduce a pole at the following frequency: f pMOD = 1 2π × ESR × C OUT When COUT is composed of “n” identical capacitors in parallel, the resulting COUT = n × COUT(EACH), and ESR = ESR(EACH)/n. Note that the capacitor zero for a parallel combination of alike capacitors is the same as for an individual capacitor. R1 gm COMP R2 2π × C OUT × R LOAD The output capacitor and its ESR also introduce a zero at: f zMOD = VOUT 1 REF RC CF The feedback voltage-divider has a gain of GAINFB = VFB/VOUT, where VFB is 1V (typ). The transconductance error amplifier has a DC gain of GAINEA(DC) = gm_EA × ROUT_EA, where gm_EA is the error amplifier transconductance, which is 700µS (typ), and ROUT_EA is the output resistance of the error amplifier (50MΩ). CC Figure 3. Compensation Network www.maximintegrated.com Maxim Integrated │  15 MAX20002/MAX20003 A dominant pole (fdpEA) is set by the compensation capacitor (CC) and the amplifier output resistance (ROUT_EA). A zero (fZEA) is set by the compensation resistor (RC) and the compensation capacitor (CC). There is an optional pole (fPEA) set by CF and RC to cancel the output capacitor ESR zero if it occurs near the crossover frequency (fC, where the loop gain equals 1 (0dB)). Thus: f zEA = f pdEA = 1 2π × C C × R C 1 2π × C C × (R OUT,EA + R C ) 1 f pEA = 2π × C F × R C The loop-gain crossover frequency (fC) should be set below 1/10 of the switching frequency and much higher than the power-modulator pole (fpMOD) f f pMOD