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19-1680; Rev 1; 2/03
12V, Ultra-Low IQ, Low-Dropout Linear Regulators
General Description
The MAX1725/MAX1726 are ultra-low supply current, low-dropout linear regulators intended for low-power applications that demand the longest possible battery life. Unlike inferior PNP-based designs, the MAX1725/ MAX1726s' PMOS pass elements maintain an ultra-low 2A supply current throughout their entire operating range and in dropout. Despite their ultra-low power consumption, the MAX1725/MAX1726 have tight output accuracy (1.5%) and require just 1F output capacitance to achieve good load-transient response. These regulators have a wide input voltage range (+2.5V to +12V), making them excellent choices for systems powered from two lithium-ion (Li+) cells and 9V batteries. Other features include reverse-battery protection, short-circuit protection, and thermal protection. The MAX1725 provides an adjustable 1.5V to 5V output using an external resistor-divider. The MAX1726 provides factory preset 1.8V, 2.5V, 3.3V, or 5V output voltages (see the Ordering Information). Both devices are available in a tiny 5-pin SOT23 package. o 2A Supply Current o Reverse-Battery Protection o +2.5V to +12V Input Voltage Range o Fixed 1.8V, 2.5V, 3.3V, and 5V Output Voltages (MAX1726) o Adjustable 1.5V to 5V Output Voltages (MAX1725) o 20mA Guaranteed Output Current o 1.5% Output Voltage Accuracy o Small 1F Output Capacitor o Short-Circuit Protection o Thermal Protection o Tiny 5-Pin SOT23 Package
Features
MAX1725/MAX1726
________________________Applications
Smoke Detectors Remote Transmitters Smart Battery Packs Industrial Control Systems Microcontroller Power Real-Time Clock Backup Power PDAs and Handy-Terminals Battery-Powered Alarms
PART MAX1725EUK-T MAX1726EUK25-T MAX1726EUK33-T MAX1726EUK5-T
Ordering Information
TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C PINPACKAGE 5 SOT23-5 5 SOT23-5 5 SOT23-5 5 SOT23-5 5 SOT23-5 TOP MARK ADNK ADNL ADNM ADNN ADNO
MAX1726EUK18-T -40C to +85C
Note: See the Selector Guide for the MAX1725/MAX1726 output options as they relate to the part number suffix.
Typical Operating Circuit
PART
VIN 2.5V TO 12V IN OUT OUTPUT 1.5V TO 5V
Selector Guide
OUTPUT VOLTAGE (V) Adj 1.5 to 5.0 Fixed 1.8 Fixed 2.5 Fixed 3.3 Fixed 5.0
MAX1725EUK-T MAX1726EUK18-T MAX1726EUK25-T MAX1726EUK33-T MAX1726EUK50-T
MAX1726
ON OFF SHDN GND
Pin Configuration appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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12V, Ultra-Low IQ, Low-Dropout Linear Regulators MAX1725/MAX1726
ABSOLUTE MAXIMUM RATINGS
IN to GND ................................................................-14V to +14V SHDN to GND ..............................................-0.3V to (VIN + 0.3V) (-0.3V to + 0.3V when VIN < 0V) OUT, FB (MAX1725 only) to GND...................-0.3V to +6V when VIN >5.7V; -0.3V to (VIN + 0.3V) when 0V < VIN < 5.7V; -0.3V to +0.3V when VIN < 0V OUT Continuous Current...................................................200mA OUT Short Circuit...........................................................Indefinite Continuous Power Dissipation (TA = +70C) 5-Pin SOT23-5 (derate 7.1mW/C above +70C) ........571mW JA ...............................................................................+140C/W Junction Temperature ......................................................+150C Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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.
(Circuit of Figure 1, VIN = VOUT + 1V, SHDN = IN, IOUT = 1mA, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Input Voltage Range Supply Current Shutdown Supply Current OUT Voltage Range FB Voltage OUT Voltage Accuracy (Note 3) Line Regulation Load Regulation Maximum OUT Current Dropout Voltage (Note 4) Foldback Current Limit SHDN Input Threshold SHDN Input Bias Current FB Input Bias Current (MAX1725 only) IN Reverse Leakage Current Thermal-Shutdown Threshold Thermal-Shutdown Hysteresis VLNR VLDR IOUT VDO ISC VIH VIL I SHDN IFB SYMBOL VIN IIN IIN(SHDN) VOUT VFB (Note 2) VIN = 12V SHDN = 0V, VIN = 12V, VOUT = 0V MAX1725 only MAX1725 only (Note 3) TA = +25C TA = 0C to +85C TA = -40C to +85C VIN = 2.5V or (VOUT + 0.5V) to 12V IOUT = 1mA to 20mA, VIN = (VOUT + 1V) or 3V (min) VIN = (VOUT + 1V) or 3V (Note 4) IOUT = 20mA for VOUT 2.5V, IOUT = 10mA for VOUT < 2.5V, not applicable for VOUT < 1.9V VIN = 12V, VOUT = 0V VIN = 2.5V to 12V V SHDN = 0V to 12V VFB = 1.25V VIN = -12V, V SHDN = 0V Temperature rising TA = +25C TA = +85C TA = +25C TA = +85C -20 2 0.5 -50 0.1 2 1.5 0.01 150 15 10 +20 +50 20 -1.5 -2 -3 0.01 0.015 80 300 40 600 1.5 1.245 1.5 +2 +3 0.3 0.15 %/V %/mA mA mV mA V nA nA A C C % CONDITIONS MIN 2.5 2 0.7 TYP MAX 12 4.5 2 5 UNITS V A A V V
ELECTRICAL CHARACTERISTICS
2
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12V, Ultra-Low IQ, Low-Dropout Linear Regulators
ELECTRICAL CHARACTERISTICS (continued)
PARAMETER OUT Line-Transient Overshoot/Undershoot OUT Load-Transient Overshoot/Undershoot OUT Noise Note 1: Note 2: Note 3: Note 4: en SYMBOL
MAX1725/MAX1726
(Circuit of Figure 1, VIN = VOUT + 1V, SHDN = IN, IOUT = 1mA, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) CONDITIONS VIN = 0.25V, tR = tF = 5s IOUT from 1mA to 10mA, tR = tF = 1s f = 10Hz to 100kHz MIN TYP 15 200 350 MAX UNITS mV mV VRMS
Limits are 100% production tested at +25C. All temperature limits are guaranteed by design. Guaranteed by OUT line-regulation testing. OUT accuracy from nominal voltage. The MAX1725 is tested at VOUT = 1.5V, 2.5V, and 5V. When VOUT falls to 4% below its value at VIN = VOUT + 1V.
Typical Operating Characteristics
(VOUT = +3.3V, IOUT = 1mA, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. INPUT VOLTAGE
MAX1725/26 toc01
SUPPLY CURRENT vs. LOAD CURRENT
MAX1725/26 toc02
SUPPLY CURRENT vs. TEMPERATURE
VIN = 5V
MAX1725/26 toc03
5
5
VIN = 5V
5
4 SUPPLY CURRENT (A)
4 SUPPLY CURRENT (A)
4 SUPPLY CURRENT (A)
3
3
3
2
2
2
1
1
1
0 4 5 6 7 8 9 10 11 12 INPUT VOLTAGE (V)
0 0 5 10 LOAD CURRENT (mA) 15 20
0 -40 -20 0 20 40 60 80 TEMPERATURE (C)
OUTPUT VOLTAGE vs. INPUT VOLTAGE
NOMINAL OUTPUT = 3.3V OUTPUT VOLTAGE (%DEVIATION) -0.2 -0.4 -0.6 -0.8 -1.0 ILOAD = 20mA -1.2 -1.4 4 5 6 7 8 9 10 11 12 INPUT VOLTAGE (V) ILOAD = 1mA
MAX1725/26 toc04
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1725/26 toc05
NORMALIZED OUTPUT VOLTAGE vs. TEMPERATURE
NORMALIZED OUTPUT VOLTAGE (%)
MAX1725/26 toc06
0
0.8 OUTPUT VOLTAGE (% DEVIATION) 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 0 2 4 6 8 NOMINAL OUTPUT = 3.3V VIN = 4.5V
0.30 0.20 0.10 IOUT = 1mA 0 -0.10 -0.20 -0.30
10 12 14 16 18 20
-40
-20
0
20
40
60
80
LOAD CURRENT (mA)
TEMPERATURE (C)
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12V, Ultra-Low IQ, Low-Dropout Linear Regulators MAX1725/MAX1726
Typical Operating Characteristics (continued)
(VOUT = +3.3V, IOUT = 1mA, TA = +25C, unless otherwise noted.)
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX1725/26 toc07 MAX1725/26 toc08
DROPOUT VOLTAGE vs. LOAD CURRENT
300 250 DROPOUT VOLTAGE (mV) 200 150 100 50 0 0 5 10 LOAD CURRENT (mA) 15 20 TA = -40C 10 0 0.01 TA = +85C 80 70 60 PSRR (dB) 50 40 30 20
LINE-TRANSIENT RESPONSE
COUT = 1F IOUT = 1mA
MAX1725/26 toc09
VIN = 5V VOUT = 3.3V RL = 3.3k COUT = 1F
TA = +25C
VIN 200mV/div
VOUT 20mV/div
0.1
1 FREQUENCY (kHz)
10
100
100s/div
LOAD TRANSIENT
MAX1725/26 toc10
TURN-ON/TURN-OFF RESPONSE
COUT = 1F IOUT = 1mA VSHDN 2V/div
MAX1725/26 toc11
COUT = 1F IOUT = 1mA - 20mA IOUT 20mA/div
VOUT 100mV/div
VOUT 1V/div
400s/div
4ms
Pin Description
PIN NAME MAX1725 MAX1726 1 2 3 4 -- 5 4 1 2 3 -- 4 5 IN GND OUT FB GND SHDN Supply Voltage Input Ground Voltage Output Feedback Voltage Input Ground Active-Low Shutdown Input FUNCTION
Detailed Description
The MAX1725/MAX1726 are low-dropout, low-quiescentcurrent linear regulators designed primarily for batterypowered applications (Figure 1). The MAX1725 provides an adjustable output voltage from 1.5V to 5V using an external resistor-divider. The MAX1726 supplies preset output voltages of 1.8V, 2.5V, 3.3V, or 5V. These devices consist of a +1.245V error amplifier, MOSFET driver, and P-channel pass transistor (Figure 2).
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12V, Ultra-Low IQ, Low-Dropout Linear Regulators
The error amplifier compares 1.245V to the selected feedback voltage and amplifies the difference. If the feedback voltage is lower than 1.245V, the pass-transistor gate is pulled lower, allowing more current to pass, and thus increasing the output voltage. If the feedback voltage is higher than 1.245V, the pass-transistor gate is driven higher, allowing less current to pass to the output. The output voltage is fed back through either an internal resistor voltage-divider connected to OUT (MAX1726) or an external resistor network connected to FB (MAX1725). Additional features include an output current limiter, reverse-battery protection, a thermal sensor, and shutdown logic.
MAX1725/MAX1726
Internal P-Channel Pass Transistor
The MAX1725/MAX1726 feature a P-channel MOSFET pass transistor. This provides advantages over similar designs using PNP pass transistors, including longer battery life. The P-channel MOSFET requires no base drive, which reduces quiescent current considerably. PNP-based regulators waste considerable current in dropout when the pass transistor saturates; they also use high base-drive currents under large loads. The MAX1725/MAX1726 do not suffer from these problems, and consume only 2A of quiescent current throughout their load range (see the Typical Operating Characteristics).
INPUT 2.5V TO 12V CIN 1F IN OUT
OUTPUT 1.5V TO 5V COUT 1F R1
MAX1725
ON OFF SHDN GND FB
R2 1.2M
Shutdown
To enter shutdown, drive the SHDN pin below 0.5V. When the MAX1725/MAX1726 are shut down, the output
Figure 1. Typical Application Circuit
IN
OUT
MAX1725 MAX1726
BIAS CIRCUITRY THERMAL SHUTDOWN 1.245V (MAX1726 ONLY)
SHDN
FB (MAX1725 ONLY)
GND
Figure 2. Functional Diagram
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12V, Ultra-Low IQ, Low-Dropout Linear Regulators MAX1725/MAX1726
pass transistor shuts off, the output falls to ground, and supply current drops from 2A to 0.7A. Connect SHDN to IN for normal operation. If reverse-battery protection is needed, drive SHDN through a 100k resistor. The MAX1725 features an adjustable output voltage from 1.5V to 5V, using two external resistors connected as a voltage-divider to FB (Figure 1). The MAX1725 is optimized for operation with R2 = 1.2M. The output voltage is set by the following equation: R1 VOUT = VFB 1 + R2 where typically VFB = 1.245V. To simplify resistor selection: V R1 = R2 OUT - 1 VFB Choose R2 = 1.2M for best accuracy.
Thermal-Overload Protection
Thermal-overload protection limits total power dissipation in the MAX1725/MAX1726. When the junction temperature exceeds T J = +150C, the thermal sensor signals the shutdown logic, turning off the pass transistor and allowing the IC to cool. The thermal sensor turns the pass transistor on again after the IC's junction temperature cools by 15C, resulting in a pulsed output during continuous thermal-overload conditions. Thermal-overload protection is designed to protect the devices in the event of fault conditions. For continuous operation, do not exceed the absolute maximum junction temperature rating of TJ = +150C.
Foldback Current Limiting
The MAX1725/MAX1726 also include a foldback current limiter. When the output is shorted to ground, the output PMOS drive is limited so that the output current does not exceed 40mA (typ). The output can be shorted to ground indefinitely without damaging the part.
Power-Supply Rejection and Operation from Sources Other than Batteries
The MAX1725/MAX1726 are designed to deliver low dropout voltages and low quiescent currents in batterypowered systems. Power-supply rejection is 60dB at low frequencies and rolls off above 100Hz. At high frequencies, the output capacitor is the major contributor to the rejection of power-supply noise (see the Power-Supply Rejection Ratio vs. Frequency graph in the Typical Operating Characteristics). When operating from sources other than batteries, improve supply-noise rejection and transient response by increasing the value of the input and output capacitors, and by using passive filtering techniques (see the Supply and Load Transient Response graph in the Typical Operating Characteristics).
Reverse-Battery Protection
The MAX1725/MAX1726 have a unique protection scheme that limits the reverse supply current to less than 10A when VIN is forced below ground. The circuitry monitors the polarity of the input, disconnecting the internal circuitry and parasitic diodes when the battery is reversed. This feature prevents the device, battery, and load from overheating and electrical stress. For reverse-battery protection, drive SHDN through a 100k resistor.
Applications Information
Capacitor Selection and Regulator Stability
For general purposes, use a 1F capacitor on the MAX1725/MAX1726 input and output. Larger input capacitor values and lower ESR provide better supplynoise rejection and transient response. A higher-value input capacitor (10F) may be necessary if large, fast transients are anticipated and the device is located several inches from the power source. For stable operation over the full temperature range, use a minimum of 1F on the output.
Chip Information
TRANSISTOR COUNT: 112
Pin Configuration
TOP VIEW
IN 1 5 SHDN
GND 2
MAX1725 MAX1726
4 FB (GND)
Output Voltage Selection
For fixed 1.8V, 2.5V, 3.3V, or 5V output voltages, use the MAX1726.
OUT 3
( ) ARE FOR MAX1726 ONLY.
SOT23-5
6
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12V, Ultra-Low IQ, Low-Dropout Linear Regulators
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
SOT5L.EPS
MAX1725/MAX1726
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________7 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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