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19-4488; Rev 0; 3/09
1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input
General 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 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 -40C to +125C. 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 2A during shutdown. These regulators use small, 1F ceramic input capacitors and 4.7F 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 4.7F 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 5.5A 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 -40C to +125C 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. 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 60A Operating Bias Supply Current (MAX15028) o 1.2A Shutdown Bias Supply Current (MAX15028) o Short-Circuit and Thermal Protection o -40C to +125C Operating Temperature Range o Soft-Start Limits Inrush Current o Thermally Enhanced 3mm x 3mm TDFN Package
Features
MAX15027/MAX15028
Ordering Information
PART MAX15027ATB+T MAX15028ATB+T TEMP RANGE PINPACKAGE TOP MARK +AUD +AUE
-40C to +125C 10 TDFN-EP* -40C to +125C 10 TDFN-EP*
+Denotes a lead(Pb)-free and RoHS-compliant package. For tape-and-reel orders, add a "T" after the "+". *EP = Exposed pad.
Applications
Automotive (Dead-Man LDO) Servers Storage Networking Base Stations Optical Modules ATE
IN IN I.C. EN 2 3 4 5 9 OUT GND FB SS 8 7 6
Pin Configurations
TOP VIEW
IN 1
+
10
OUT
MAX15027
Typical Operating Circuits appear at end of data sheet.
TDFN (3mm x 3mm)
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
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.
1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input MAX15027/MAX15028
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 = +70C) 10-Pin TDFN, Multilayer Board (derate 24.4mW/C above +70C) ..............................1951mW Junction-to-Case Thermal Resistance, JC .......................9C/W Junction-to-Ambient Thermal Resistance, JA (Note 1)...41C/W Operating Junction Temperature Range ...........-40C to +125C Maximum Junction Temperature .....................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 = -40C to +125C. Typical values are at TA = +25C, unless otherwise noted.) (Note 2)
PARAMETER IN MAX15027 Input Voltage Range VIN MAX15028 VIN rising, IOUT = 2mA VBIAS = 3V to 5.5V BIAS = IN MAX15027 MAX15028 1.425 1.425 3.000 1.275 1.04 1.325 1.106 50 VIN = 1.425V to 3.6V, VOUT = 1.2V, IOUT = 1mA, VBIAS = 3.3V VIN = 3.6V, VOUT = 3.3V, IOUT = 100mA VIN = 3.3V, VOUT = 3.3V, IOUT = 500mA Input Supply Current in Shutdown BIAS (MAX15028) Input Voltage Range Undervoltage Lockout Undervoltage Lockout Hysteresis Quiescent Input Supply Current IBIAS VBIAS VBIAS_UVLO VBIAS rising, IOUT = 2mA IOUT = 2mA VEN = VBIAS VIN = 0, VOUT = 0, VBIAS = 3.3V Input Supply Current in Shutdown IBIAS_SD EN = GND VIN = 3.3V, VOUT = 0, VBIAS = 3.3V VIN = 3.3V, VOUT = 0, VBIAS = 5V 20 3 2.3 2.5 110 60 1.2 1.2 1.5 120 2 2 3 A 5.5 2.7 V V mV A IIN_SD VEN = 0, TA = -40C to +85C 160 180 170 275 275 315 0.1 410 560 470 5.5 A A 3.600 3.600 3.600 1.375 1.14 V mV V SYMBOL CONDITIONS MIN TYP MAX UNITS
Undervoltage Lockout Undervoltage Lockout Hysteresis
VUVLO VUVLO_HYST
Quiescent GND Current
IGND
2
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1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1; VIN = 1.8V, VOUT = 1.2V, EN = IN for MAX15027, EN = BIAS for MAX15028, IOUT = 100mA, TA = TJ = -40C to +125C. Typical values are at TA = +25C, unless otherwise noted.) (Note 2)
PARAMETER OUT Output Voltage Range Load Regulation Line Regulation Dropout Voltage (VIN - VOUT) Output Current Limit FB Threshold Accuracy Input Current EN/SOFT-START Enable Input Threshold (MAX15028) Enable Input Threshold (MAX15027) Soft-Start Charging Current Soft-Start Reference Voltage THERMAL SHUTDOWN Thermal-Shutdown Threshold Thermal-Shutdown Hysteresis TJ rising 165 15 C C VIH VIL VIH VIL ISS VSS VBIAS = 5V VIN = 1.8V 1.05 0.4 1.05 0.4 5 0.499 V V A V VFB IFB VOUT = 0.5V to 3.3V, VIN = (VOUT + 0.3V) to 3.6V, IOUT = 1mA to 1A VFB = 0.688V 0.489 0.499 0.1 0.509 0.2 mV A VDO ILIM VOUT IOUT = 1mA to 1A VIN = 1.425V to 3.6V, IOUT = 1mA IOUT = 1A, VIN = 1.5V VFB = 300mV 1.4 0.5 0.01 4 75 1.7 225 2.0 3.3 V mV/mA mV mV A SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX15027/MAX15028
Note 2: All devices are 100% production tested at TA = +25C. Limits over the operating temperature range are guaranteed by design and characterization.
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3
1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input MAX15027/MAX15028
Typical Operating Characteristics
(Circuit of Figure 1, VIN = 1.8V, VOUT = 1.5V, IOUT = 1A, TA = +25C, unless otherwise noted.)
MAX15028 OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX15027 toc01
MAX15028 OUTPUT VOLTAGE vs. OUTPUT CURRENT
VBIAS = 3.3V 1.515 OUTPUT VOLTAGE (V) 1.510 1.505 1.500 1.495 1.490
MAX15027 toc02
INPUT CURRENT (IIN) vs. INPUT VOLTAGE (VIN)
MAX15027 toc03
1.6 1.4 OUTPUT VOLTAGE (V) 1.2 1.0 0.8 0.6 0.4 0.2 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 IOUT = 0 VBIAS = 3.3V
1.520
0.4
INTPUT CURRENT (mA)
0.3
0.2
0.1 VBIAS = 3.3V 0 0 100 200 300 400 500 600 700 800 900 1000 OUTPUT CURRENT (mA) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 INPUT VOLTAGE (V)
1.485 1.480 4.0
INPUT VOLTAGE (V)
MAX15028 BIAS CURRENT (IBIAS) vs. BIAS VOLTAGE (VBIAS)
MAX15027 toc04
MAX15028 BIAS CURRENT (IBIAS) vs. OUTPUT CURRENT
54 53 BIAS CURRENT (A) 52 51 50 49 48 47 VBIAS = 5.5V
MAX15027 toc05
GROUND CURRENT vs. OUTPUT CURRENT
MAX15027 toc06
60 50 BIAS CURRENT (A) 40 30 20 10 IOUT = 0 0 0 1 2 3 4 5 6 BIAS VOLTAGE (V)
55
0.35
0.34 GROUND CURRENT (mA)
0.33
VBIAS = 3.3V
0.32
0.31 VBIAS = 3.3V 0.30 0 100 200 300 400 500 600 700 800 900 1000 OUTPUT CURRENT (mA) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 LOAD CURRENT (A)
46 45
MAX15028 DROPOUT VOLTAGE vs. OUTPUT CURRENT
MAX15027 toc07
MAX15028 DROPOUT VOLTAGE vs. OUTPUT CURRENT
180 DROPOUT VOLTAGE (mV) 160 140 120 100 80 60 40 20 0 VIN = 1.4V VBIAS = 3.3V
MAX15027 toc07
200 180 DROPOUT VOLTAGE (mV) 160 140 120 100 80 60 40 20 0 VIN = 1.4V VBIAS = 3.3V
200
0 100 200 300 400 500 600 700 800 900 1000 OUTPUT CURRENT (mA)
0 100 200 300 400 500 600 700 800 900 1000 OUTPUT CURRENT (mA)
4
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1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 1.8V, VOUT = 1.5V, IOUT = 1A, TA = +25C, unless otherwise noted.)
MAX15027/MAX15028
POWER-UP RESPONSE
MAX15027 toc09a
POWER-DOWN RESPONSE
MAX15027 toc09b
VOUT
1V/div
VOUT
1V/div
VIN IOUT = 500mA 2ms/div
2V/div
VIN IOUT = 500mA 10s/div
2V/div
TURN-ON VIA ENABLE RESPONSE
MAX15027 toc10a
TURN-OFF VIA ENABLE RESPONSE
MAX15027 toc10b
1V/div VOUT 1V/div VOUT
2V/div VEN IOUT = 500mA 20s/div 4s/div 2V/div VEN IOUT = 500mA
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
50dB
MAX15027 toc11
MAX15028 FB VOLTAGE (VFB) vs. TEMPERATURE
0.508
MAX15027 toc12
0.510
10dB/div FB VOLTAGE (VFB) (V)
0.506 0.504 0.502 0.500 0.498 0.496 0.494 0.492 VBIAS = 3.3V -40 -20 0 20 40 60
100Hz
1MHz
0.490 80 100 120 140 TEMPERATURE (C)
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5
1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input MAX15027/MAX15028
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 1.8V, VOUT = 1.5V, IOUT = 1A, TA = +25C, unless otherwise noted.)
OVERCURRENT THRESHOLD vs. TEMPERATURE
MAX15027 toc13
CASE TEMPERATURE RISE vs. POWER DISSIPATION
70 CASE TEMPERATURE RISE (C) 60 50 40 30 20 10 0 0 0.5 1.0 1.5 2.0 2.5
MAX15027 toc14
1.80 1.78 OVERCURRENT THRESHOLD (A) 1.76 1.74 1.72 1.70 1.68 1.66 1.64 1.62 1.60 -40 -20 0 20 40 60 VBIAS = 3.3V
80
80 100 120 140
TEMPERATURE (C)
POWER DISSIPATION (W)
Pin Description
PIN MAX15027 1, 2, 3 -- 4 5 MAX15028 1, 2 3 4 5 NAME IN BIAS I.C. EN FUNCTION Regulator Input. 1.425V to 3.6V voltage range. Bypass to GND with at least 1F of ceramic capacitance. IN is high impedance when the LDO is shut down. Internal Circuitry Supply Input. BIAS supplies the power for the internal circuitry. 3V to 5.5V voltage range. Internally Connected. Connect I.C. directly to GND. 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. Soft-Start Input. For typical operation, connect a 0.1F capacitor from SS to GND. The soft-start timing is dependent on the value of this capacitor. See the Soft-Start section. 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. Ground Regulator Output. Bypass OUT to GND with at least 4.7F of ceramic capacitance for 1A load operation. Exposed Paddle. Connect EP to GND and a large copper ground plane to facilitate package power dissipation.
6
6
SS
7 8 9, 10 --
7 8 9, 10 --
FB GND OUT EP
6
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1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input
Functional Diagram
MAX15027/MAX15028
IN MAX15027 ONLY MAX15028 ONLY BIAS REF
MAX15027 MAX15028
INTERNAL SUPPLY GENERATOR BIAS UVLO IN UVLO
REF CONTROL LOGIC ERROR AMPLIFIER WITH SOFT-START
EN OVERTEMPERATURE PROTECTION
MOS DRIVER WITH ILIMIT
P OUT 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 -40C to +125C. Since these regulators have a pMOS output device, supply current is not a significant function of load or input headroom.
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7
1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input MAX15027/MAX15028
Internal p-Channel Pass Transistor
The MAX15027/MAX15028 feature a 75m (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 275A (typ) of quiescent current under heavy loads, as well as in dropout.
Shutdown Mode
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 2A. 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 10k resistor is connected between OUT and GND.
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 10k. 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 500. To simplify resistor selection: V R1 = R2 OUT - 1 VFB
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 +165C (typ), the thermal-overload circuitry turns off the output, allowing the part to cool down. When the junction temperature cools to +150C (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 = +150C.
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 5A (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 INPUT 1.2V TO 3.6V 1F
BIAS
OUTPUT OUT R1 FB I.C. R2
IN
MAX15028
ENABLE EN SHUTDOWN SS 0.1uF
4.7F
GND
Figure 1. MAX15028 Typical Application Circuit
8
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1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input
Capacitor Selection and Regulator Stability
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 1F capacitor between IN and ground and a 4.7F 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: 1F COUT = IOUT(MAX) x 0.25A
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 4.7F (up to 100F) to attenuate the overshoot.
MAX15027/MAX15028
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.
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.
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9
1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS Input MAX15027/MAX15028
Typical Operating Circuits
OUTPUT 0.5V TO VIN OUTPUT 0.5V TO VIN
OUT INPUT 1.425V TO 3.6V 1F IN
ALWAYS-ON INPUT 3V TO 5.5V INPUT 1.425V TO 3.6V 1F
BIAS IN
OUT
MAX15027
FB
4.7F
MAX15028
FB
4.7F
EN SS GND
EN SS GND
Pin Configurations (continued)
PROCESS: BiCMOS
TOP VIEW
IN IN BIAS I.C. EN 1 2 3 4 5
Chip Information
+
10 9
OUT OUT GND FB SS
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 10 TDFN PACKAGE CODE T1033-1 DOCUMENT NO. 21-0137
MAX15028
8 7 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 (c) 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

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