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
2µA 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 1µF 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 protec-
tion, short-circuit protection, and thermal protection.
The MAX1725 provides an adjustable 1.5V to 5V output
using an external resistor-divider. The MAX1726 pro-
vides factory preset 1.8V, 2.5V, 3.3V, or 5V output volt-
ages (see the Ordering Information). Both devices are
available in a tiny 5-pin SOT23 package.
________________________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
Features
♦2µA Supply Current
♦Reverse-Battery Protection
♦+2.5V to +12V Input Voltage Range
♦Fixed 1.8V, 2.5V, 3.3V, and 5V Output Voltages
(MAX1726)
♦Adjustable 1.5V to 5V Output Voltages (MAX1725)
♦20mA Guaranteed Output Current
♦1.5% Output Voltage Accuracy
♦Small 1µF Output Capacitor
♦Short-Circuit Protection
♦Thermal Protection
♦Tiny 5-Pin SOT23 Package
MAX1725/MAX1726
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
________________________________________________________________ Maxim Integrated Products 1
VIN
2.5V TO 12V
OUTPUT
1.5V TO 5V
MAX1726
OFF
ON
IN OUT
SHDN GND
Typical Operating Circuit
19-1680; Rev 1; 2/03
Ordering Information
Selector Guide
Pin Configuration appears at end of data sheet.
Note: See the Selector Guide for the MAX1725/MAX1726 output
options as they relate to the part number suffix.
5 SOT23-5
PIN-
PACKAGE
TEMP RANGE
-40°C to +85°C
MAX1725EUK-T
PART
5 SOT23-5-40°C to +85°C
MAX1726EUK18-T
5 SOT23-5-40°C to +85°CMAX1726EUK25-T
5 SOT23-5-40°C to +85°CMAX1726EUK33-T
5 SOT23-5-40°C to +85°CMAX1726EUK5-T
ADNK
TOP
MARK
ADNL
ADNM
ADNN
ADNO
OUTPUT VOLTAGE
(V)
PART
Adj 1.5 to 5.0MAX1725EUK-T
Fixed 1.8MAX1726EUK18-T
Fixed 2.5MAX1726EUK25-T
Fixed 3.3MAX1726EUK33-T
Fixed 5.0MAX1726EUK50-T
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX1725/MAX1726
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VIN = VOUT + 1V, SHDN = IN, IOUT = 1mA, TA= -40°C to +85°C, unless otherwise noted. Typical values are at
TA= +25°C.) (Note 1)
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.
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= +70°C)
5-Pin SOT23-5 (derate 7.1mW/°C above +70°C) ........571mW
θJA ...............................................................................+140°C/W
Junction Temperature......................................................+150°C
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
SHDN = 0V, VIN = 12V, VOUT = 0V
VIN = 12V
(Note 2)
VIN = -12V, VSHDN = 0V
VIN = 2.5V to 12V
VIN = 12V, VOUT = 0V
VFB = 1.25V
IOUT = 20mA for VOUT ≥2.5V, IOUT = 10mA for
VOUT < 2.5V, not applicable for VOUT < 1.9V
VIN = (VOUT + 1V) or 3V (Note 4)
MAX1725 only
VIN = 2.5V or (VOUT + 0.5V) to 12V
IOUT = 1mA to 20mA, VIN = (VOUT + 1V)
or 3V (min)
VSHDN = 0V to 12V
CONDITIONS
°C15Thermal-Shutdown Hysteresis
µA0.01 10IN Reverse Leakage Current
1.5 nA
-20 2 +20
IFB
FB Input Bias Current
(MAX1725 only)
0.1 nA
-50 +50
ISHDN
SHDN Input Bias Current
µA0.7 2IIN(SHDN)
Shutdown Supply Current
µA2 4.5IIN
V2.5 12VIN
Input Voltage Range
Supply Current
V
2VIH
mA40ISC
Foldback Current Limit
mV300 600
∆VDO
Dropout Voltage (Note 4)
mA20 80IOUT
Maximum OUT Current
V1.5 5VOUT
OUT Voltage Range
%
-1.5 1.5
OUT Voltage Accuracy (Note 3)
%/V0.01 0.3
∆VLNR
Line Regulation
%/mA0.015 0.15
∆VLDR
Load Regulation
UNITSMIN TYP MAXSYMBOLPARAMETER
TA= +25°C
TA= +85°C
TA= +25°C
TA= +85°C
MAX1725 only (Note 3) V1.245VFB
FB Voltage
-2 +2
-3 +3
TA= +25°C
TA= 0°C to +85°C
TA= -40°C to +85°C
0.5VIL
SHDN Input Threshold
Temperature rising °C150Thermal-Shutdown Threshold
MAX1725/MAX1726
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
_______________________________________________________________________________________ 3
0
1
3
2
4
5
4675 8 9 101112
SUPPLY CURRENT vs. INPUT VOLTAGE
MAX1725/26 toc01
INPUT VOLTAGE (V)
SUPPLY CURRENT (µA)
0
1
3
2
4
5
SUPPLY CURRENT vs. LOAD CURRENT
MAX1725/26 toc02
LOAD CURRENT (mA)
SUPPLY CURRENT (µA)
01051520
VIN = 5V
0
3
2
1
4
5
-40 0 20-20 40 60 80
SUPPLY CURRENT vs. TEMPERATURE
MAX1725/26 toc03
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
VIN = 5V
-1.4
-1.0
-0.4
-0.6
-0.2
0
4675 8 9 101112
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1725/26 toc04
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (%DEVIATION)
-0.8
-1.2
ILOAD = 20mA
ILOAD = 1mA
NOMINAL OUTPUT = 3.3V
-0.8
-0.4
0.2
-0.2
0.6
0.8
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1725/26 toc05
LOAD CURRENT (mA)
OUTPUT VOLTAGE (% DEVIATION)
0426 20
0.4
0
-0.6
8101214
16 18
NOMINAL OUTPUT = 3.3V
VIN = 4.5V
-0.30
-0.10
0.10
0
0.20
0.30
-40 0-20 20 40 60 80
NORMALIZED OUTPUT VOLTAGE
vs. TEMPERATURE
MAX1725/26 toc06
TEMPERATURE (°C)
NORMALIZED OUTPUT VOLTAGE (%)
-0.20
IOUT = 1mA
Typical Operating Characteristics
(VOUT = +3.3V, IOUT = 1mA, TA= +25°C, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = VOUT + 1V, SHDN = IN, IOUT = 1mA, TA= -40°C to +85°C, unless otherwise noted. Typical values are at
TA= +25°C.) (Note 1)
Note 1: Limits are 100% production tested at +25°C. All temperature limits are guaranteed by design.
Note 2: Guaranteed by OUT line-regulation testing.
Note 3: OUT accuracy from nominal voltage. The MAX1725 is tested at VOUT = 1.5V, 2.5V, and 5V.
Note 4: When VOUT falls to 4% below its value at VIN = VOUT + 1V.
IOUT from 1mA to 10mA, tR= tF= 1µs
∆VIN = ±0.25V, tR= tF= 5µs
f = 10Hz to 100kHz
CONDITIONS
mV200
OUT Load-Transient
Overshoot/Undershoot
mV15
OUT Line-Transient
Overshoot/Undershoot
µVRMS
350en
OUT Noise
UNITSMIN TYP MAXSYMBOLPARAMETER
Detailed Description
The MAX1725/MAX1726 are low-dropout, low-quiescent-
current linear regulators designed primarily for battery-
powered 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).
MAX1725/MAX1726
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
4 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VOUT = +3.3V, IOUT = 1mA, TA= +25°C, unless otherwise noted.)
NAME
MAX1725 MAX1726
1 1 IN
2 2 GND
3 3 OUT
— 4 GND
4 — FB
Pin Description
FUNCTION
Supply Voltage Input
Ground
Voltage Output
Ground
Feedback Voltage Input
5 5 SHDN Active-Low Shutdown Input
PIN
IOUT
20mA/div
VOUT
100mV/div
400µs/div
LOAD TRANSIENT
MAX1725/26 toc10
COUT = 1µF
IOUT = 1mA - 20mA
VSHDN
2V/div
VOUT
1V/div
4ms
TURN-ON/TURN-OFF RESPONSE
MAX1725/26 toc11
COUT = 1µF
IOUT = 1mA
0
100
50
200
150
250
300
01051520
DROPOUT VOLTAGE vs. LOAD CURRENT
MAX1725/26 toc07
LOAD CURRENT (mA)
DROPOUT VOLTAGE (mV)
TA = +85°C
TA = +25°C
TA = -40°C
80
70
60
50
40
30
20
10
0
0.01 1 100.1 100
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX1725/26 toc08
FREQUENCY (kHz)
PSRR (dB)
VIN = 5V
VOUT = 3.3V
RL = 3.3kΩ
COUT = 1µF
VIN
200mV/div
VOUT
20mV/div
100µs/div
LINE-TRANSIENT RESPONSE
MAX1725/26 toc09
COUT = 1µF
IOUT = 1mA
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-tran-
sistor 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-tran-
sistor 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 con-
nected to OUT (MAX1726) or an external resistor net-
work connected to FB (MAX1725). Additional features
include an output current limiter, reverse-battery protec-
tion, a thermal sensor, and shutdown logic.
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 prob-
lems, and consume only 2µA of quiescent current
throughout their load range (see the Typical Operating
Characteristics).
Shutdown
To enter shutdown, drive the SHDN pin below 0.5V.
When the MAX1725/MAX1726 are shut down, the output
MAX1725/MAX1726
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
_______________________________________________________________________________________ 5
INPUT
2.5V TO 12V
OUTPUT
1.5V TO 5V
MAX1725
OFF
ON
IN OUT
FB
SHDN GND
R1
R2
1.2MΩ
COUT
1µF
CIN
1µF
IN OUT
FB (MAX1725 ONLY)
(MAX1726 ONLY)
SHDN
BIAS
CIRCUITRY
THERMAL
SHUTDOWN
GND
1.245V
MAX1725
MAX1726
Figure 1. Typical Application Circuit
Figure 2. Functional Diagram
MAX1725/MAX1726
pass transistor shuts off, the output falls to ground, and
supply current drops from 2µA to 0.7µA. Connect SHDN
to IN for normal operation. If reverse-battery protection
is needed, drive SHDN through a 100kΩresistor.
Thermal-Overload Protection
Thermal-overload protection limits total power dissipa-
tion in the MAX1725/MAX1726. When the junction tem-
perature exceeds TJ= +150°C, 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 tem-
perature cools by 15°C, 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= +150°C.
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.
Reverse-Battery Protection
The MAX1725/MAX1726 have a unique protection
scheme that limits the reverse supply current to less
than 10µA when VIN is forced below ground. The cir-
cuitry 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
100kΩresistor.
Applications Information
Capacitor Selection and
Regulator Stability
For general purposes, use a 1µF capacitor on the
MAX1725/MAX1726 input and output. Larger input
capacitor values and lower ESR provide better supply-
noise rejection and transient response. A higher-value
input capacitor (10µF) may be necessary if large, fast
transients are anticipated and the device is located sev-
eral inches from the power source. For stable operation
over the full temperature range, use a minimum of 1µF
on the output.
Output Voltage Selection
For fixed 1.8V, 2.5V, 3.3V, or 5V output voltages, use
the MAX1726.
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 = 1.2MΩ. The output
voltage is set by the following equation:
where typically VFB = 1.245V. To simplify resistor selec-
tion:
Choose R2 = 1.2MΩfor best accuracy.
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 battery-
powered systems. Power-supply rejection is 60dB at low
frequencies and rolls off above 100Hz. At high frequen-
cies, 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 capaci-
tors, and by using passive filtering techniques (see the
Supply and Load Transient Response graph in the
Typical Operating Characteristics).
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
6 _______________________________________________________________________________________
Chip Information
TRANSISTOR COUNT: 112
GND
FB (GND)OUT
15SHDNIN
MAX1725
MAX1726
SOT23-5
TOP VIEW
2
34
( ) ARE FOR MAX1726 ONLY.
Pin Configuration
VV R
R
OUT FB
=+
11
2
RR
V
V
OUT
FB
12 1 =
−
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
© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
MAX1725/MAX1726
SOT5L.EPS
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.)
