19-4488; Rev 0; 3/09 1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input The MAX15027/MAX15028 low-dropout linear regulators operate from input voltages as low as 1.425V and deliver up to 1A of continuous output current with a typical dropout voltage of only 75mV. The output voltage is adjustable from 0.5V to VIN and is ±2% accurate over load and line variations, from -40°C to +125°C. The MAX15028 features a BIAS input of 3V to 5.5V from an always-on power supply. The BIAS input current is reduced down to less than 2µA during shutdown. These regulators use small, 1µF ceramic input capacitors and 4.7µF ceramic output capacitors to deliver 1A output current. High bandwidth provides excellent transient response and limits the output voltage deviation to 15mV for a 500mA load step, with only a 4.7µF ceramic output capacitor, and the voltage deviations can be reduced further by increasing the output capacitor. These devices offer a logic-controlled shutdown input to reduce input current (IIN) consumption down to less than 5.5µA in standby mode. Other features include a soft-start to reduce inrush current, short-circuit protection, and thermal-overload protection. The MAX15028 features a BIAS input allowing a secondary supply to keep the LDO’s internal circuitry alive if the voltage on IN goes to 0V. Both devices are fully specified from -40°C to +125°C and are available in a 10-pin thermally enhanced TDFN package (3mm x 3mm) that includes an exposed pad for optimal power dissipation. For a 500mA version of these LDOs, refer to the MAX15029/MAX15030 data sheet. Features o 1.425V to 3.6V Input Voltage Range o Output Voltage Programmable from 0.5V to VIN o Guaranteed Maximum 225mV Dropout at 1A Output Current o ±2% Output Accuracy Over Load, Line, and Temperature o Stable with Ceramic Capacitors o Fast Transient Response o 60µA Operating Bias Supply Current (MAX15028) o 1.2µA Shutdown Bias Supply Current (MAX15028) o Short-Circuit and Thermal Protection o -40°C to +125°C Operating Temperature Range o Soft-Start Limits Inrush Current o Thermally Enhanced 3mm x 3mm TDFN Package Ordering Information PART TEMP RANGE PINPACKAGE TOP MARK MAX15027ATB+T -40°C to +125°C 10 TDFN-EP* +AUD MAX15028ATB+T -40°C to +125°C 10 TDFN-EP* +AUE +Denotes a lead(Pb)-free and RoHS-compliant package. For tape-and-reel orders, add a “T” after the “+”. *EP = Exposed pad. Applications Pin Configurations Automotive (Dead-Man LDO) Servers TOP VIEW Storage Networking IN 1 IN 2 IN 3 I.C. EN + 10 OUT 9 OUT 8 GND 4 7 FB 5 6 SS Base Stations Optical Modules ATE Typical Operating Circuits appear at end of data sheet. MAX15027 TDFN (3mm x 3mm) Pin Configurations continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX15027/MAX15028 General Description MAX15027/MAX15028 1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input ABSOLUTE MAXIMUM RATINGS IN, FB, SS, I.C. to GND..........................................-0.3V to +4.0V BIAS to GND.............................................................-0.3V to +6V EN to GND ................-0.3V to the lower of (VBIAS + 0.3V) or +6V OUT to GND ................................................-0.3V to (VIN + 0.3V) Output Short-Circuit Duration.....................................Continuous Continuous Power Dissipation (TA = +70°C) 10-Pin TDFN, Multilayer Board (derate 24.4mW/°C above +70°C) ..............................1951mW Junction-to-Case Thermal Resistance, θJC .......................9°C/W Junction-to-Ambient Thermal Resistance, θJA (Note 1)...41°C/W Operating Junction Temperature Range ...........-40°C to +125°C Maximum Junction Temperature .....................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial. 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. ELECTRICAL CHARACTERISTICS (Circuit of Figure 1; VIN = 1.8V, VOUT = 1.2V, EN = IN for MAX15027, EN = BIAS for MAX15028, IOUT = 100mA, TA = TJ = -40°C to +125°C. Typical values are at TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS IN MAX15027 Input Voltage Range Undervoltage Lockout Undervoltage Lockout Hysteresis VIN VUVLO MAX15028 VIN rising, IOUT = 2mA 1.425 3.600 VBIAS = 3V to 5.5V 1.425 3.600 BIAS = IN 3.000 MAX15027 1.275 1.325 1.375 MAX15028 1.04 1.106 1.14 VUVLO_HYST Quiescent GND Current IGND Input Supply Current in Shutdown IIN_SD V 3.600 50 V mV VIN = 1.425V to 3.6V, VOUT = 1.2V, IOUT = 1mA, VBIAS = 3.3V 160 275 410 VIN = 3.6V, VOUT = 3.3V, IOUT = 100mA 180 275 560 VIN = 3.3V, VOUT = 3.3V, IOUT = 500mA 170 315 470 0.1 5.5 µA 5.5 V VEN = 0, TA = -40°C to +85°C µA BIAS (MAX15028) Input Voltage Range Undervoltage Lockout VBIAS VBIAS_UVLO VBIAS rising, IOUT = 2mA Undervoltage Lockout Hysteresis Quiescent Input Supply Current Input Supply Current in Shutdown 2 3 2.3 IOUT = 2mA IBIAS IBIAS_SD VEN = VBIAS EN = GND 2.5 2.7 110 20 60 120 VIN = 0, VOUT = 0, VBIAS = 3.3V 1.2 2 VIN = 3.3V, VOUT = 0, VBIAS = 3.3V 1.2 2 VIN = 3.3V, VOUT = 0, VBIAS = 5V 1.5 3 _______________________________________________________________________________________ V mV µA µA 1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input (Circuit of Figure 1; VIN = 1.8V, VOUT = 1.2V, EN = IN for MAX15027, EN = BIAS for MAX15028, IOUT = 100mA, TA = TJ = -40°C to +125°C. Typical values are at TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS OUT Output Voltage Range VOUT Load Regulation 0.5 IOUT = 1mA to 1A Line Regulation 3.3 0.01 V mV/mA VIN = 1.425V to 3.6V, IOUT = 1mA 4 Dropout Voltage (VIN - VOUT) VDO IOUT = 1A, VIN = 1.5V 75 225 mV mV Output Current Limit ILIM VFB = 300mV 1.4 1.7 2.0 A Threshold Accuracy VFB VOUT = 0.5V to 3.3V, VIN = (VOUT + 0.3V) to 3.6V, IOUT = 1mA to 1A 0.489 0.499 0.509 mV Input Current IFB VFB = 0.688V 0.1 0.2 µA FB EN/SOFT-START Enable Input Threshold (MAX15028) VIH Enable Input Threshold (MAX15027) VIH VIL VIL VBIAS = 5V VIN = 1.8V 1.05 V 0.4 1.05 V 0.4 Soft-Start Charging Current ISS 5 µA Soft-Start Reference Voltage VSS 0.499 V THERMAL SHUTDOWN Thermal-Shutdown Threshold Thermal-Shutdown Hysteresis TJ rising 165 °C 15 °C Note 2: All devices are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design and characterization. _______________________________________________________________________________________ 3 MAX15027/MAX15028 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (Circuit of Figure 1, VIN = 1.8V, VOUT = 1.5V, IOUT = 1A, TA = +25°C, unless otherwise noted.) 0.8 0.6 1.510 INTPUT CURRENT (mA) 1.0 1.505 1.500 1.495 IOUT = 0 VBIAS = 3.3V 0.2 VBIAS = 3.3V 0 1.480 0.5 1.0 1.5 2.0 2.5 3.0 0.5 1.0 1.5 2.0 2.5 3.0 INPUT VOLTAGE (V) OUTPUT CURRENT (mA) INPUT VOLTAGE (V) MAX15028 BIAS CURRENT (IBIAS) vs. BIAS VOLTAGE (VBIAS) MAX15028 BIAS CURRENT (IBIAS) vs. OUTPUT CURRENT GROUND CURRENT vs. OUTPUT CURRENT 40 30 20 52 51 VBIAS = 5.5V 50 49 VBIAS = 3.3V 48 VBIAS = 3.3V 0.30 45 3 4 5 6 MAX15028 DROPOUT VOLTAGE vs. OUTPUT CURRENT VBIAS = 3.3V 160 140 120 100 80 60 40 VIN = 1.4V 200 180 DROPOUT VOLTAGE (mV) DROPOUT VOLTAGE (mV) MAX15027 toc07 200 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 LOAD CURRENT (A) OUTPUT CURRENT (mA) MAX15028 DROPOUT VOLTAGE vs. OUTPUT CURRENT 180 0 0 100 200 300 400 500 600 700 800 900 1000 BIAS VOLTAGE (V) MAX15027 toc07 IOUT = 0 2 0.32 46 0 1 0.33 0.31 47 10 0.34 GROUND CURRENT (mA) 53 VBIAS = 3.3V 160 140 120 100 80 60 40 VIN = 1.4V 20 20 0 0 0 100 200 300 400 500 600 700 800 900 1000 OUTPUT CURRENT (mA) 4.0 MAX15027 toc06 54 BIAS CURRENT (µA) 50 3.5 0.35 MAX15027 toc05 55 MAX15027 toc04 60 0 0 0 100 200 300 400 500 600 700 800 900 1000 4.0 3.5 0.2 1.485 0 0 0.3 0.1 1.490 0.4 4 0.4 MAX15027 toc03 1.515 OUTPUT VOLTAGE (V) 1.2 VBIAS = 3.3V MAX15027 toc02 1.4 OUTPUT VOLTAGE (V) 1.520 MAX15027 toc01 1.6 INPUT CURRENT (IIN) vs. INPUT VOLTAGE (VIN) MAX15028 OUTPUT VOLTAGE vs. OUTPUT CURRENT MAX15028 OUTPUT VOLTAGE vs. INPUT VOLTAGE BIAS CURRENT (µA) MAX15027/MAX15028 1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input 0 100 200 300 400 500 600 700 800 900 1000 OUTPUT CURRENT (mA) _______________________________________________________________________________________ 1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input POWER-DOWN RESPONSE POWER-UP RESPONSE MAX15027 toc09b MAX15027 toc09a VOUT 1V/div VOUT 1V/div VIN 2V/div VIN 2V/div IOUT = 500mA IOUT = 500mA 10µs/div 2ms/div TURN-OFF VIA ENABLE RESPONSE TURN-ON VIA ENABLE RESPONSE MAX15027 toc10b MAX15027 toc10a 1V/div VOUT 1V/div VOUT VEN 2V/div VEN 2V/div IOUT = 500mA IOUT = 500mA 20µs/div 4µs/div POWER-SUPPLY REJECTION RATIO vs. FREQUENCY MAX15028 FB VOLTAGE (VFB) vs. TEMPERATURE MAX15027 toc11 0.510 MAX15027 toc12 50dB 0.508 0.506 FB VOLTAGE (VFB) (V) 10dB/div 0.504 0.502 0.500 0.498 0.496 0.494 0.492 100Hz 1MHz VBIAS = 3.3V 0.490 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX15027/MAX15028 Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = 1.8V, VOUT = 1.5V, IOUT = 1A, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = 1.8V, VOUT = 1.5V, IOUT = 1A, TA = +25°C, unless otherwise noted.) OVERCURRENT THRESHOLD vs. TEMPERATURE CASE TEMPERATURE RISE vs. POWER DISSIPATION 1.76 1.74 1.72 1.70 1.68 1.66 1.64 1.62 80 MAX15027 toc14 1.78 70 CASE TEMPERATURE RISE (°C) MAX15027 toc13 1.80 OVERCURRENT THRESHOLD (A) MAX15027/MAX15028 1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input 60 50 40 30 20 10 VBIAS = 3.3V 1.60 0 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) 0 0.5 1.0 1.5 2.0 2.5 POWER DISSIPATION (W) Pin Description PIN 6 NAME FUNCTION MAX15027 MAX15028 1, 2, 3 1, 2 IN Regulator Input. 1.425V to 3.6V voltage range. Bypass to GND with at least 1µF of ceramic capacitance. IN is high impedance when the LDO is shut down. — 3 BIAS Internal Circuitry Supply Input. BIAS supplies the power for the internal circuitry. 3V to 5.5V voltage range. 4 4 I.C. Internally Connected. Connect I.C. directly to GND. 5 5 EN LDO Enable. Drive EN high to enable the LDO or connect to IN (BIAS for MAX15028) for always-on operation. Drive EN low to disable the LDO and place the IC in low-power shutdown mode. 6 6 SS Soft-Start Input. For typical operation, connect a 0.1µF capacitor from SS to GND. The soft-start timing is dependent on the value of this capacitor. See the Soft-Start section. 7 7 FB Feedback Input. Connect FB to the center of a resistor-divider connected between OUT and GND to set the output voltage. See the Programming the Output Voltage section. 8 8 GND Ground Regulator Output. Bypass OUT to GND with at least 4.7µF of ceramic capacitance for 1A load operation. 9, 10 9, 10 OUT — — EP Exposed Paddle. Connect EP to GND and a large copper ground plane to facilitate package power dissipation. _______________________________________________________________________________________ 1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input IN MAX15027 ONLY MAX15028 ONLY REF BIAS MAX15027 MAX15028 INTERNAL SUPPLY GENERATOR IN UVLO BIAS UVLO REF CONTROL LOGIC ERROR AMPLIFIER WITH SOFT-START EN MOS DRIVER WITH ILIMIT P OUT OVERTEMPERATURE PROTECTION SS FB GND Detailed Description The MAX15027/MAX15028 low-dropout linear regulators operate from input voltages as low as 1.425V and deliver up to 1A of continuous output current with a maximum dropout voltage of only 225mV. The MAX15028 operates with an input voltage as low as 1.425V if the bias voltage (VBIAS) of 3V to 5.5V is available. The power is applied at IN while the control is provided through BIAS input. The current drawn by BIAS is negligible when the LDO goes into shutdown. This feature is especially useful in automotive applica- tions where the BIAS input is derived from an alwayson LDO that expects to provide minimal power during the key-off condition. The pMOS output stage can be driven from input voltages down to +1.425V without sacrificing stability or transient performance. The output voltage of all the regulators is adjustable from 0.5V to VIN and is ±2% accurate over load and line variations, from -40°C to +125°C. Since these regulators have a pMOS output device, supply current is not a significant function of load or input headroom. _______________________________________________________________________________________ 7 MAX15027/MAX15028 Functional Diagram MAX15027/MAX15028 1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input Internal p-Channel Pass Transistor Shutdown Mode The MAX15027/MAX15028 feature a 75mΩ (typ) p-channel MOSFET pass transistor. Unlike similar designs using pnp pass transistors, p-channel MOSFETs require no base drive, reducing quiescent current. pnp-based regulators also waste considerable current in dropout when the pass transistor saturates and use high base-drive currents under large loads. The MAX15027/MAX15028 do not suffer from these problems and consume only 275µA (typ) of quiescent current under heavy loads, as well as in dropout. The MAX15027/MAX15028 include an enable input. To shut down the IC, drive EN low. In shutdown mode, the current drawn by BIAS is less than 2µA. This feature is extremely useful in an automotive application where the BIAS input is derived from an always-on LDO expecting to provide minimal dark current. For normal operation, drive EN high or connect EN to IN (BIAS for MAX15028) for continuous on operation. During shutdown, an internal 10kΩ resistor is connected between OUT and GND. Short-Circuit/ Thermal Fault Protection The MAX15027/MAX15028 are fully protected from a short circuit at the output through current limiting and thermal-overload circuitry. In the fault condition when the output is shorted to ground, the output current is limited to a maximum of 2A. Under these conditions, the device quickly heats up. When the junction temperature reaches +165°C (typ), the thermal-overload circuitry turns off the output, allowing the part to cool down. When the junction temperature cools to +150°C (typ), the output turns back on and reestablishes regulation. Current limiting and thermal protection continue until the fault is removed. For continuous operation, do not exceed the absolute maximum junction-temperature rating of TJ = +150°C. Applications Information Programming the Output Voltage The MAX15027/MAX15028 feature an adjustable output voltage from 0.5V to VIN using two external resistors connected as a voltage-divider to FB as shown in Figure 1. The output voltage is set by the following equation: R1 ⎞ ⎛ VOUT = VFB ⎜1 + ⎟ ⎝ R2 ⎠ where typically VFB = 0.5V. Choose R2 to be 10kΩ. Or, to optimize load-transient response for no load to full load transients, use the resistor-divider as a minimum load and choose R2 to be 500Ω. To simplify resistor selection: ⎛V ⎞ R1 = R2⎜ OUT − 1⎟ ⎝ VFB ⎠ Soft-Start The MAX15027/MAX15028 feature a soft-start function that slowly ramps up the output voltage of the regulator based on the value of the capacitor (CSS) connected from SS to GND. Upon power-up, CSS is charged with a 5µA (typ) current source through SS. The voltage at SS is compared to the internal 0.5V reference (VREF). The feedback voltage for regulation (VREG) is the lower of VSS or VREF. As VSS rises, the regulation voltage (VREG) rises at the same rate. Once VSS reaches and rises above VREF, the regulation voltage then tracks the reference voltage since it is the lower of VSS and VREF. The value of CSS determines the length of the soft-start time, tSS. Use the following formula to determine CSS. CSS = 10-5 x tSS where CSS is in farads and tSS is in seconds. ALWAYS-ON INPUT 3V TO 5.5V BIAS INPUT 1.2V TO 3.6V IN OUTPUT OUT R1 1µF MAX15028 ENABLE FB I.C. EN SHUTDOWN GND SS 0.1uF Figure 1. MAX15028 Typical Application Circuit 8 _______________________________________________________________________________________ 4.7µF R2 1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input Capacitors are required at the MAX15027/MAX15028’s inputs and outputs for stable operation over the full temperature range and with load currents up to 1A. Connect a 1µF capacitor between IN and ground and a 4.7µF capacitor with low equivalent series resistance (ESR) between OUT and ground for 1A output current. The input capacitor (CIN) lowers the source impedance of the input supply. If input supply source impedance is high, place a larger input capacitor close to IN to prevent VIN sagging due to load transients. Smaller output capacitors can be used for output currents less than 1A. Calculate the minimum COUT as follows: ⎛ 1µF ⎞ COUT = IOUT(MAX) × ⎜ ⎟ ⎝ 0.25A ⎠ Operating Region and Power Dissipation The maximum power dissipation depends on the thermal resistance of the IC package and circuit board, the temperature difference between the die junction and ambient air, and the rate of airflow. The power dissipated in the device is P DISS = I OUT (V IN - V OUT). The package features an exposed thermal pad on its underside. This pad lowers the thermal resistance of the package by providing a direct heat conduction path from the die to the PCB. Connect the exposed backside pad and GND to the system ground using a large pad or ground plane and multiple vias to the ground plane layer. Noise, PSRR, and Transient Response The MAX15027/MAX15028 are designed to operate with low-dropout voltages and low quiescent currents while still maintaining good noise performance, transient response, and AC rejection (see the Typical Operating Characteristics for a plot of Power-Supply Rejection Ratio (PSRR) vs. Frequency). When operating from noisy sources, improved supply-noise rejection and transient response can be achieved by increasing the values of the input and output bypass capacitors and through passive filtering techniques. The MAX15027/MAX15028 load-transient response graphs (see the Typical Operating Characteristics) show two components of the output response: a DC shift from the output impedance due to the load current change, and the transient response. A typical transient overshoot for a step change in the load current from 300mA to 800mA is 15mV. Use ceramic output capacitors greater than 4.7µF (up to 100µF) to attenuate the overshoot. Layout Guidelines The TDFN package has an exposed thermal pad on its underside. This pad provides a low thermal resistance path for heat transfer into the PCB. This low thermally resistive path carries a majority of the heat away from the IC. The PCB is effectively a heatsink for the IC. The exposed pad should be connected to a large ground plane for proper thermal and electrical performance. The minimum size of the ground plane is dependent upon many system variables. To create an efficient path, the exposed pad should be soldered to a thermal landing, which is connected to the ground plane by thermal vias. The thermal landing should be at least as large as the exposed pad. _______________________________________________________________________________________ 9 MAX15027/MAX15028 Capacitor Selection and Regulator Stability MAX15027/MAX15028 1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input Typical Operating Circuits OUTPUT 0.5V TO VIN OUT INPUT 1.425V TO 3.6V ALWAYS-ON INPUT 3V TO 5.5V INPUT 1.425V TO 3.6V 1µF IN 1µF MAX15027 FB BIAS OUT IN MAX15028 4.7µF EN OUTPUT 0.5V TO VIN FB 4.7µF EN SS GND SS GND Chip Information Pin Configurations (continued) PROCESS: BiCMOS TOP VIEW IN 1 IN 2 BIAS 3 I.C. 4 EN + MAX15028 5 10 OUT 9 OUT Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. 8 GND 7 FB PACKAGE TYPE PACKAGE CODE DOCUMENT NO. SS 10 TDFN T1033-1 21-0137 6 TDFN (3mm x 3mm) Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.