_______________General Description
The MAX8873T/S/R and MAX8874T/S/R low-dropout lin-
ear regulators operate from a +2.5V to +6.5V input
range and deliver up to 120mA. A PMOS pass transis-
tor allows the low, 82µA supply current to remain inde-
pendent of load, making these devices ideal for
battery-operated portable equipment such as cellular
phones and cordless phones.
The devices feature Dual Mode™ operation: their out-
put voltage is preset (at 3.15V for the T versions, 2.84V
for the S versions, or 2.80V for the R versions) or can be
adjusted with an external resistor divider. Total error on
the output is ±3.5%. Output voltages are set on the low
side of popular ranges so that power drain is minimized
for longer battery life. Other features include low-power
shutdown, short-circuit protection, thermal shutdown
protection, and reverse battery protection. The
MAX8874 also includes an auto-discharge function,
which actively discharges the output voltage to ground
when the device is placed in shutdown mode. Both
devices come in a miniature 5-pin SOT23 package.
For dual versions, refer to the MAX8865/MAX8866 data
sheet. For low-noise versions with 30µVRMS output
noise, refer to the MAX8877/MAX8878.
________________________Applications
Cordless Telephones Modems
PCS Telephones Hand-Held Instruments
Cellular Telephones Palmtop Computers
PCMCIA Cards Electronic Planners
____________________________Features
♦LP2980 Pin-Compatible SOT23 Package
♦Low, 55mV Dropout Voltage at 50mA IOUT
(130mV at 120mA)
♦Low, 73µA No-Load Supply Current
Low, 82µA Operating Supply Current (even in
dropout)
♦Miniature External Components
♦Thermal Overload Protection
♦Output Current Limit
♦Reverse Battery Protection
♦Dual Mode Operation: Fixed or Adjustable
(1.25V to 6.5V) Output
♦Low-Power Shutdown
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
________________________________________________________________
Maxim Integrated Products
1
SOT23-5
TOP VIEW
GND
SET
SHDN
15OUT
IN
MAX8873
MAX8874
2
34
__________________Pin Configuration
MAX8873
MAX8874
OUT
GND SET
IN
SHDN COUT
1µF
CIN
1µF
BATTERY
OUTPUT
VOLTAGE
__________Typical Operating Circuit
19-1257; Rev 1; 3/98
PART
MAX8873TEUK-T
MAX8873SEUK-T
MAX8874TEUK-T -40°C to +85°C
-40°C to +85°C
-40°C to +85°C
TEMP. RANGE PIN-
PACKAGE
5 SOT23-5
5 SOT23-5
5 SOT23-5
______________Ordering Information
SOT TOP
MARK
ABZH
ABZI
ABZJ
MAX8874SEUK-T -40°C to +85°C 5 SOT23-5 ABZK
Dual Mode is a trademark of Maxim Integrated Products.
MAX8873REUK-T -40°C to +85°C 5 SOT23-5 ABZL
MAX8874REUK-T -40°C to +85°C 5 SOT23-5 ABZM
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN = +3.6V, TA= TMIN to TMAX, 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.
VIN to GND ..................................................................-7V to +7V
Output Short-Circuit Duration ............................................Infinite
SET to GND..............................................................-0.3V to +7V
SHDN to GND..............................................................-7V to +7V
SHDN to IN .................................................................-7V to 0.3V
OUT to GND ................................................-0.3V to (VIN + 0.3V)
Continuous Power Dissipation (TA= +70°C)
SOT23-5 (derate 7.1mW/°C above +70°C).................571mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
θJA..................................................................................140°C/W
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
Ω
300
Shutdown Discharge
Resistance (MAX8874)
0.05
0 100
ISHDN
SHDN Input Bias Current
V
0.4VIL
SHDN Input Threshold 2.0VIH
µVRMS
220
Output Voltage Noise 350
%/mA
0.011 0.030
%/V-0.15 0 0.15∆VLNR
Line Regulation
mV
55 120
Dropout Voltage (Note 5)
V2.5 6.5VIN
Input Voltage (Note 2)
1.1
µA
73 150
IQ
Ground Pin Current
3.05 3.15 3.25
VOUT
Output Voltage
VVSET 6.5VOUT
Adjustable Output Voltage
Range (Note 3)
mA120Maximum Output Current
UNITSMIN TYP MAXSYMBOLPARAMETER
VSHDN = VIN
COUT = 100µF
IOUT = 0mA
VIN = 2.5V to 6.5V, SET tied to OUT,
IOUT = 1mA
0mA ≤IOUT ≤50mA,
SET = GND
IOUT = 50mA
CONDITIONS
mA280ILIM
Current Limit (Note 4)
V
MAX887_T
10Hz to 1MHz
IOUT = 1mA
SET = GND
COUT = 1µF
MAX887_S 2.75 2.84 2.93
IOUT = 50mA 82
0.02 µA
0.0001 1
IQSHDN
Shutdown Supply Current VOUT = 0V TA= TMAX
TA= +25°C
TA= TMAX
TA= +25°C nA
MAX887_R 2.70 2.80 2.88
IOUT = 0mA to 50mA 0.006
∆VLDR
Load Regulation SET tied to OUT
SET = GND
SHUTDOWN
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
_______________________________________________________________________________________
3
__________________________________________Typical Operating Characteristics
(VIN = +3.6V, CIN = 1µF, COUT = 1µF, MAX887_T, TA= +25°C, unless otherwise noted.)
UNITSMIN TYP MAXSYMBOLPARAMETER CONDITIONS
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +3.6V, TA= TMIN to TMAX, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
Note 1: Limits are 100% production tested at TA= +25°C. Limits over the operating temperature range are guaranteed through cor-
relation using Statistical Quality Control (SQC) methods.
Note 2: Guaranteed by line-regulation test.
Note 3: Adjustable mode only.
Note 4: For design purposes, the current limit should be considered 120mA minimum to 420mA maximum.
Note 5: The dropout voltage is defined as (VIN - VOUT) when VOUT is 100mV below the value of VOUT for VIN = VOUT + 2V.
TSHDN °CThermal Shutdown Temperature 170
∆TSHDN °CThermal Shutdown Hysteresis 20
SET Input Leakage Current
(Note 3) nA
0.015 2.5
ISET VSET = 1.3V
SET Reference Voltage (Note 3) V
1.225 1.25 1.275
VSET VIN = 2.5V to 6.5V,
IOUT = 1mA
SET INPUT
THERMAL PROTECTION
TA= +25°C
TA= +25°C
TA= TMIN to TMAX
TA= TMAX 0.5
1.215 1.25 1.285
3.00
3.05
3.10
3.15
3.20
3.25
3.30
0 20 60 100 120
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX8873/74-01
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
40 80
100
50 0 20 60 120
100
SUPPLY CURRENT
vs. LOAD CURRENT
60
90
MAX8873/74-02
LOAD CURRENT (mA)
SUPPLY CURRENT (µA)
40 80
80
70
95
55
85
75
65
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 1 2 4 6 7
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
MAX8873/74-03
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3 5
NO LOAD
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
4 _______________________________________________________________________________________
____________________________Typical Operating Characteristics (continued)
(VIN = +3.6V, CIN = 1µF, COUT = 1µF, MAX887_T, TA= +25°C, unless otherwise noted.)
1 10
MAX8873/74-08
FREQUENCY (kHz)
PSRR (dB)
70
60
50
40
30
20
10
0100 1000
0.10.01
VOUT = 3.15V
RL = 100Ω
COUT = 10µF
COUT = 1µF
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
10
0.01 0.1 10 1001 1000
OUTPUT SPECTRAL NOISE DENSITY
vs. FREQUENCY
0.10
MAX8873/74-8A
FREQUENCY (kHz)
OUTPUT SPECTRAL NOISE DENSITY (µV/√Hz)
1
RL = 50Ω
COUT = 1µF
COUT = 100µF
1000
0.01 0 60 8020 40 100 120
REGION OF STABLE COUT ESR
vs. LOAD CURRENT
0.1
MAX8873/74-8B
LOAD CURRENT (mA)
COUT ESR (Ω)
1
10
100
INTERNAL FEEDBACK
STABLE REGION
COUT = 1µF
EXTERNAL FEEDBACK
ILOAD = 50mA, VOUT IS AC COUPLED
OUTPUT NOISE DC TO 1MHz
VOUT
1ms/div
0
10
20
30
40
60
50
70
80
90
100
0 1 2 5 7
SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX8873/74-04
INPUT VOLTAGE (V)
3 4 6
SUPPLY CURRENT (µA)
ILOAD = 0mA
ILOAD = 50mA
3.00
3.05
3.10
3.15
3.20
3.25
3.30
0 20-20 60 100
OUTPUT VOLTAGE
vs. TEMPERATURE
MAX8873/74-05
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
40-40 80
ILOAD = 50mA
0
10
20
30
40
50
60
70
80
90
100
100806040200-20-40
SUPPLY CURRENT
vs. TEMPERATURE
MAX8863/4-06
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
ILOAD = 50mA
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
_______________________________________________________________________________________ 5
ILOAD = 0mA to 50mA, CIN = 10µF, VOUT IS AC COUPLED
LOAD-TRANSIENT RESPONSE
3.16V
VOUT 3.15V
3.14V
ILOAD
50mA
0mA
10µs/div
VIN = VOUT + 0.2V, ILOAD = 0mA to 50mA, CIN = 10µF,
VOUT IS AC COUPLED
LOAD-TRANSIENT RESPONSE
ILOAD
3.16V
VOUT 3.15V
3.14V
50mA
0mA
10µs/div
____________________________Typical Operating Characteristics (continued)
(VIN = +3.6V, CIN = 1µF, COUT = 1µF, MAX887_T, TA= +25°C, unless otherwise noted.)
ILOAD = 50mA, VOUT IS AC COUPLED
LINE-TRANSIENT RESPONSE
3.16V
VOUT 3.15V
3.14V
4.6V
3.6V
VIN
50µs/div
VIN = VOUT + 0.1V, ILOAD = 0mA to 50mA, CIN = 10µF,
VOUT IS AC COUPLED
LOAD-TRANSIENT RESPONSE
0mA
50mA
10µs/div
3.16V
VOUT 3.15V
3.14V
ILOAD
NO LOAD
MAX8874 SHUTDOWN (NO LOAD)
0V
VSHDN
4V
VOUT
0V
2V
2V
500µs/div
ILOAD = 50mA
MAX8874 SHUTDOWN
0V
VSHDN
VOUT
4V
2V
0V
2V
200µs/div
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
6 _______________________________________________________________________________________
_______________Detailed Description
The MAX8873/MAX8874 are low-dropout, low-quiescent-
current linear regulators designed primarily for battery-
powered applications. They supply an adjustable 1.25V to
6.5V output or a preselected 2.80V (MAX887_R), 2.84V
(MAX887_S), or 3.15V (MAX887_T) output for load currents
up to 120mA. These devices consist of a 1.25V reference,
error amplifier, MOSFET driver, P-channel pass transistor,
dual-mode comparator, and internal feedback voltage
divider (Figure 1).
The 1.25V bandgap reference is connected to the error
amplifier’s inverting input. The error amplifier compares this
reference with the selected feedback voltage and amplifies
the difference. The MOSFET driver reads the error signal
and applies the appropriate drive to the P-channel pass
transistor. If the feedback voltage is lower than the refer-
ence, the pass-transistor gate is pulled lower, allowing more
current to pass and increasing the output voltage. If the
feedback voltage is too high, the pass-transistor gate is
pulled up, allowing less current to pass to the output.
The output voltage is fed back through either an internal
resistor voltage divider connected to the OUT pin, or an
external resistor network connected to the SET pin. The
dual-mode comparator examines the SET voltage and
selects the feedback path. If SET is below 60mV, internal
feedback is used and the output voltage is regulated to the
preset output voltage. Additional blocks include a current
limiter, reverse battery protection, thermal sensor, and shut -
down logic.
SHUTDOWN
LOGIC
ERROR
AMP
1.25V
REF
P
N
*SET
OUT
DUAL-MODE
COMPARATOR 60mV
* AUTO-DISCHARGE, MAX8874 ONLY
GND
IN
SHDN
MAX8873
MAX8874
MOS DRIVER
WITH ILIMIT
THERMAL
SENSOR
REVERSE
BATTERY
PROTECTION
______________________________________________________________Pin Description
Figure 1. Functional Diagram
OUT
GND2 Ground. This pin also functions as a heatsink. Solder to large pads or the circuit board ground plane to max-
imize thermal dissipation.
3Active-Low Shutdown Input. A logic low reduces the supply current to 0.1nA. On the MAX8874, a logic low
also causes the output voltage to discharge to GND. Connect to IN for normal operation.
SET4 Feedback Input for Setting the Output Voltage. Connect to GND to set the output voltage to the preset 2.80V
(MAX887_R), 2.84V (MAX887_S), or 3.15V (MAX887_T). Connect to an external resistor divider for
adjustable-output operation. DO NOT LEAVE THIS PIN UNCONNECTED.
5Regulator Output. Fixed or adjustable from 1.25V to 6.5V. Sources up to 120mA. Bypass with a 1µF, <0.2Ω
typical ESR capacitor to GND.
SHDN
Regulator Input. Supply voltage can range from 2.5V to 6.5V. Bypass with 1µF to GND (see
Capacitor
Selection and Regulator Stability
).
IN1
PIN FUNCTIONNAME
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
_______________________________________________________________________________________ 7
Internal P-Channel Pass Transistor
The MAX8873/MAX8874 feature a 1.1Ωtypical P-chan-
nel MOSFET pass transistor. This provides several
advantages over similar designs using PNP pass tran-
sistors, including longer battery life.
The P-channel MOSFET requires no base drive current,
which reduces quiescent current considerably. PNP-
based regulators waste considerable amounts of cur-
rent in dropout when the pass transistor saturates. They
also use high base-drive currents under large loads.
The MAX8873/MAX8874 do not suffer from these prob-
lems, and consume only 82µA of quiescent current,
whether in dropout, light load, or heavy load applica-
tions (see
Typical Operating Characteristics
).
Output Voltage Selection
The MAX8873/MAX8874 feature Dual Mode operation:
they operate in either a preset voltage mode or an
adjustable mode.
In preset voltage mode, internal, trimmed feedback
resistors set the MAX887_R output to 2.80V, the
MAX887_S output to 2.84V, and the MAX887_T output to
3.15V. Select this mode by connecting SET to ground.
In adjustable mode, select an output between 1.25V
and 6.5V using two external resistors connected as a
voltage divider to SET (Figure 2). The output voltage is
set by the following equation:
VOUT = VSET (1 + R1 / R2)
where VSET = 1.25V. To simplify resistor selection:
Choose R2 = 100kΩto optimize power consumption,
accuracy, and high-frequency power-supply rejection.
The total current through the external resistive feedback
and load resistors should not be less than 10µA. Since
the VSET tolerance is typically less than ±25mV, the out-
put can be set using fixed resistors instead of trim pots.
Connect a 10pF to 25pF capacitor across R1 to com-
pensate for layout-induced parasitic capacitances.
In preset voltage mode, impedances between SET and
ground should be less than 100kΩ. Otherwise, spurious
conditions could cause the voltage at SET to exceed
the 60mV dual-mode threshold.
Shutdown
A low input on the SHDN pin shuts down the
MAX8873/MAX8874. In shutdown mode, the pass tran-
sistor, control circuit, reference, and all biases are
turned off, reducing the supply current to typically
0.1nA. Connect SHDN to IN for normal operation. The
MAX8874 output voltage is actively discharged to
ground when the part is placed in shutdown (see
Typical Operating Characteristics
).
Current Limit
The MAX8873/MAX8874 include a current limiter that
monitors and controls the pass transistor’s gate volt-
age, estimating the output current and limiting it to
about 280mA. For design purposes, the current limit
should be considered 120mA to 420mA. The output
can be shorted to ground for an indefinite time period
without damaging the part.
Thermal Overload Protection
Thermal overload protection limits total power dissipa-
tion in the MAX8873/MAX8874. When the junction tem-
perature exceeds TJ= +170°C, the thermal sensor
sends a signal to 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 typically cools by 20°C, resulting
in a pulsed output during continuous thermal overload
conditions.
Thermal overload protection is designed to protect the
MAX8873/MAX8874 in the event of fault conditions.
Stressing the device with high load currents and high
input-output differential voltages (which result in die tem-
peratures above +125°C) may cause a momentary over-
shoot (2% to 8% for 200ms) when the load is completely
removed. This can be remedied by raising the minimum
load current from 0µA (+125°C) to 100µA (+150°C). For
continuous operation, do not exceed the absolute maxi-
mum junction temperature rating of TJ= +150°C.
MAX8873
MAX8874
OUT
SET
GND
IN
15
4
2
3SHDN COUT
1µF
CIN
1µF
BATTERY
OUTPUT
VOLTAGE
R1 20pF
R2
RL
Figure 2. Adjustable Output Using External Feedback
Resistors
R1 R2 V
V1
OUT
SET
= −
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
Operating Region and Power Dissipation
Maximum power dissipation of the MAX8873/MAX8874
depends on the thermal resistance of the case and cir-
cuit board, the temperature difference between the die
junction and ambient air, and the rate of air flow. The
power dissipation across the device is P = IOUT (VIN -
VOUT). The resulting maximum power dissipation is:
PMAX = (TJ- TA) / θJA
where (TJ- TA) is the temperature difference between
the MAX8873/MAX8874 die junction and the surround-
ing air, and θJA is the thermal resistance of the chosen
package to the surrounding air.
The GND pin of the MAX8873/MAX8874 performs the
dual function of providing an electrical connection to
ground and channeling heat away. Connect the GND
pin to ground using a large pad or ground plane.
Reverse Battery Protection
The MAX8873/MAX8874 have a unique protection
scheme that limits the reverse supply current to less
than 1mA when either VIN or VSHDN falls below ground.
The circuitry monitors the polarity of these two pins, dis-
connecting the internal circuitry and parasitic diodes
when the battery is reversed. This feature prevents the
device from overheating and damaging the battery.
V
IN
> 5.5V Minimum Load Current
When operating the MAX8873/MAX8874 with an input
voltage above 5.5V, a minimum load current of 20µA is
required to maintain regulation in preset voltage mode.
When setting the output with external resistors, the min-
imum current through the external feedback resistors
and load must be 30µA.
__________Applications Information
Capacitor Selection and
Regulator Stability
Normally, use a 1µF capacitor on the input and a 1µF
capacitor on the output of the MAX8873/MAX8874.
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 several inches from the power source. Improve
load-transient response, stability, and power-supply
rejection by using large output capacitors. For stable
operation over the full temperature range, with load cur-
rents up to 120mA, a minimum of 1µF is recommended.
Noise
The MAX8873/MAX8874 exhibit 350µVRMS noise during
normal operation. When using the MAX8873/MAX8874
in applications that include analog-to-digital converters
(ADCs) of greater than 12 bits, consider the ADC’s
power-supply rejection specifications (see the Output
Noise DC to 1MHz photo in the
Typical Operating
Characteristics
). For devices with lower output noise,
refer to the MAX8877/MAX8878.
Power-Supply Rejection and Operation
from Sources Other than Batteries
The MAX8873/MAX8874 are designed to deliver low
dropout voltages and low quiescent currents in battery-
powered systems. Power-supply rejection is 62dB at
low frequencies and rolls off above 300Hz. As the fre-
quency increases above 20kHz, 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 values of the input and output capac-
itors, and by using passive filtering techniques (see the
supply and load-transient responses in the
Typical
Operating Characteristics
).
Load-Transient Considerations
The MAX8873/MAX8874 load-transient response
graphs (see
Typical Operating Characteristics
) show
two components of the output response: a DC shift of
the output voltage due to the different load currents
and the transient response. Typical overshoot for step
changes in the load current from 0mA to 50mA is
14mV. Increasing the output capacitor’s value and
decreasing its ESR attenuates transient spikes.
Input-Output (Dropout) Voltage
A regulator’s minimum input-output voltage differential
(or dropout voltage) determines the lowest usable sup-
ply voltage. In battery-powered systems, this will deter-
mine the useful end-of-life battery voltage. Because the
MAX8873/MAX8874 use a P-channel MOSFET pass
transistor, their dropout voltage is a function of RDS(ON)
multiplied by the load current (see
Electrical
Characteristics
).
___________________Chip Information
TRANSISTOR COUNT: 148
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.
8
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