MAX1725, MAX1726
19-1680; Rev 1; 2/03
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
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
Ordering Information
________________________Applications
Smoke Detectors
PART
Remote Transmitters
TEMP RANGE
PINPACKAGE
TOP
MARK
ADNK
Smart Battery Packs
MAX1725EUK-T
-40°C to +85°C
5 SOT23-5
Industrial Control Systems
MAX1726EUK18-T -40°C to +85°C
5 SOT23-5
ADNL
MAX1726EUK25-T
-40°C to +85°C
5 SOT23-5
ADNM
MAX1726EUK33-T
-40°C to +85°C
5 SOT23-5
ADNN
MAX1726EUK5-T
-40°C to +85°C
5 SOT23-5
ADNO
Microcontroller Power
Real-Time Clock Backup Power
PDAs and Handy-Terminals
Note: See the Selector Guide for the MAX1725/MAX1726 output
options as they relate to the part number suffix.
Battery-Powered Alarms
Typical Operating Circuit
VIN
2.5V TO 12V
IN
OUT
MAX1726
ON
OFF
SHDN
GND
OUTPUT
1.5V TO 5V
Selector Guide
PART
OUTPUT VOLTAGE
(V)
MAX1725EUK-T
Adj 1.5 to 5.0
MAX1726EUK18-T
Fixed 1.8
MAX1726EUK25-T
Fixed 2.5
MAX1726EUK33-T
Fixed 3.3
MAX1726EUK50-T
Fixed 5.0
Pin Configuration appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products
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.
1
MAX1725/MAX1726
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 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.
MAX1725/MAX1726
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
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 = +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
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 = VOUT + 1V, SHDN = IN, IOUT = 1mA, TA = -40°C to +85°C, unless otherwise noted. Typical values are at
TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
Input Voltage Range
VIN
(Note 2)
Supply Current
IIN
VIN = 12V
Shutdown Supply Current
OUT Voltage Range
FB Voltage
IIN(SHDN)
VOUT
VFB
TYP
MAX
12
V
2
4.5
µA
0.7
2
µA
5
V
2.5
SHDN = 0V, VIN = 12V, VOUT = 0V
MAX1725 only
1.5
MAX1725 only (Note 3)
1.245
TA = +25°C
OUT Voltage Accuracy (Note 3)
MIN
UNITS
V
-1.5
1.5
TA = 0°C to +85°C
-2
+2
TA = -40°C to +85°C
-3
+3
%
Line Regulation
∆VLNR
VIN = 2.5V or (VOUT + 0.5V) to 12V
0.01
0.3
%/V
Load Regulation
∆VLDR
IOUT = 1mA to 20mA, VIN = (VOUT + 1V)
or 3V (min)
0.015
0.15
%/mA
Maximum OUT Current
IOUT
VIN = (VOUT + 1V) or 3V (Note 4)
Dropout Voltage (Note 4)
∆VDO
IOUT = 20mA for VOUT ≥ 2.5V, IOUT = 10mA for
VOUT < 2.5V, not applicable for VOUT < 1.9V
300
VIN = 12V, VOUT = 0V
40
Foldback Current Limit
SHDN Input Threshold
SHDN Input Bias Current
FB Input Bias Current
(MAX1725 only)
ISC
VIH
VIL
I SHDN
IFB
VFB = 1.25V
80
mA
600
0.5
TA = +25°C
-50
TA = +85°C
TA = +25°C
TA = +85°C
+50
0.1
-20
2
mV
mA
2
VIN = 2.5V to 12V
V SHDN = 0V to 12V
20
+20
1.5
nA
nA
IN Reverse Leakage Current
VIN = -12V, V SHDN = 0V
0.01
Thermal-Shutdown Threshold
Temperature rising
150
°C
15
°C
Thermal-Shutdown Hysteresis
2
_______________________________________________________________________________________
10
V
µA
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
(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)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
OUT Line-Transient
Overshoot/Undershoot
∆VIN = ±0.25V, tR = tF = 5µs
15
mV
OUT Load-Transient
Overshoot/Undershoot
IOUT from 1mA to 10mA, tR = tF = 1µs
200
mV
f = 10Hz to 100kHz
350
µVRMS
OUT Noise
Note 1:
Note 2:
Note 3:
Note 4:
en
Limits are 100% production tested at +25°C. 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 = +25°C, unless otherwise noted.)
2
3
2
5
6
7
8
9
10
11
2
0
0
12
3
1
0
4
VIN = 5V
4
1
0
MAX1725/26 toc03
MAX1725/26 toc02
4
1
5
10
15
-40
20
-20
0
20
40
60
TEMPERATURE (°C)
OUTPUT VOLTAGE vs. INPUT VOLTAGE
OUTPUT VOLTAGE vs. LOAD CURRENT
NORMALIZED OUTPUT VOLTAGE
vs. TEMPERATURE
-0.4
ILOAD = 1mA
-0.6
-0.8
-1.0
ILOAD = 20mA
-1.2
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.4
4
5
6
7
8
9
INPUT VOLTAGE (V)
10
11
12
0.30
80
MAX1725/26 toc06
NOMINAL OUTPUT = 3.3V
VIN = 4.5V
NORMALIZED OUTPUT VOLTAGE (%)
-0.2
0.8
OUTPUT VOLTAGE (% DEVIATION)
NOMINAL OUTPUT = 3.3V
MAX1725/26 toc05
LOAD CURRENT (mA)
MAX1725/26 toc04
INPUT VOLTAGE (V)
0
OUTPUT VOLTAGE (%DEVIATION)
VIN = 5V
5
SUPPLY CURRENT (µA)
3
5
SUPPLY CURRENT (µA)
MAX1725/26 toc01
SUPPLY CURRENT (µA)
4
SUPPLY CURRENT vs. TEMPERATURE
SUPPLY CURRENT vs. LOAD CURRENT
SUPPLY CURRENT vs. INPUT VOLTAGE
5
0.20
0.10
IOUT = 1mA
0
-0.10
-0.20
-0.30
0
2
4
6
8
10 12 14 16 18 20
LOAD CURRENT (mA)
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
_______________________________________________________________________________________
3
MAX1725/MAX1726
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics (continued)
(VOUT = +3.3V, IOUT = 1mA, TA = +25°C, unless otherwise noted.)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
200
VIN = 5V
VOUT = 3.3V
RL = 3.3kΩ
COUT = 1µF
70
60
PSRR (dB)
TA = +25°C
150
LINE-TRANSIENT RESPONSE
VIN
200mV/div
50
40
30
100
VOUT
20mV/div
20
TA = -40°C
50
10
0
0
5
10
15
20
0.01
0.1
LOAD CURRENT (mA)
1
10
100µs/div
100
FREQUENCY (kHz)
LOAD TRANSIENT
IOUT
20mA/div
TURN-ON/TURN-OFF RESPONSE
MAX1725/26 toc10
COUT = 1µF
IOUT = 1mA - 20mA
MAX1725/26 toc11
0
COUT = 1µF
IOUT = 1mA
VSHDN
2V/div
VOUT
100mV/div
VOUT
1V/div
400µs/div
Pin Description
PIN
NAME
FUNCTION
MAX1725 MAX1726
4
COUT = 1µF
IOUT = 1mA
1
1
IN
Supply Voltage Input
2
2
GND
Ground
3
3
OUT
Voltage Output
4
—
FB
—
4
GND
Ground
5
5
SHDN
Active-Low Shutdown Input
4ms
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).
Feedback Voltage Input
_______________________________________________________________________________________
MAX1725/26 toc09
TA = +85°C
250
80
MAX1725/26 toc07
300
MAX1725/26 toc08
DROPOUT VOLTAGE vs. LOAD CURRENT
DROPOUT VOLTAGE (mV)
MAX1725/MAX1726
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
INPUT
2.5V TO 12V
CIN
1µF
OUTPUT
1.5V TO 5V
IN
OUT
R1
MAX1725
ON
SHDN
OFF
COUT
1µF
FB
GND
R2
1.2MΩ
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.
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 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
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
_______________________________________________________________________________________
5
MAX1725/MAX1726
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
MAX1725/MAX1726
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
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 100kΩ resistor.
Thermal-Overload Protection
Thermal-overload protection limits total power dissipation in the MAX1725/MAX1726. When the junction temperature exceeds T J = +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 temperature 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 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
100kΩ resistor.
Applications Information
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:
R1 

VOUT = VFB 1 +


R2 
where typically VFB = 1.245V. To simplify resistor selection:
V

R1 = R2  OUT − 1
 VFB

Choose R2 = 1.2MΩ for 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 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).
Chip Information
TRANSISTOR COUNT: 112
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 supplynoise rejection and transient response. A higher-value
input capacitor (10µF) 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 1µF
on the output.
Output Voltage Selection
For fixed 1.8V, 2.5V, 3.3V, or 5V output voltages, use
the MAX1726.
6
Pin Configuration
TOP VIEW
IN 1
GND 2
SHDN
4
FB (GND)
MAX1725
MAX1726
OUT 3
( ) ARE FOR MAX1726 ONLY.
5
SOT23-5
_______________________________________________________________________________________
12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
SOT5L.EPS
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.
MAX1725/MAX1726
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.)
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