MAX8873R, MAX8873S, MAX8873T, MAX8874R, MAX8874S, MAX8874T

MAX8873R, MAX8873S, MAX8873T, MAX8874R, MAX8874S, MAX8874T
19-1257; Rev 1; 3/98
Low-Dropout, 120mA Linear Regulators
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
____________________________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
______________Ordering Information
TEMP. RANGE
PINPACKAGE
SOT TOP
MARK
MAX8873TEUK-T -40°C to +85°C
5 SOT23-5
ABZH
-40°C to +85°C
5 SOT23-5
ABZI
MAX8873REUK-T -40°C to +85°C
5 SOT23-5
ABZL
PART
MAX8873SEUK-T
Modems
PCS Telephones
Hand-Held Instruments
MAX8874TEUK-T -40°C to +85°C
5 SOT23-5
ABZJ
Cellular Telephones
Palmtop Computers
MAX8874SEUK-T
-40°C to +85°C
5 SOT23-5
ABZK
PCMCIA Cards
Electronic Planners
MAX8874REUK-T -40°C to +85°C
5 SOT23-5
ABZM
__________Typical Operating Circuit
__________________Pin Configuration
TOP VIEW
IN 1
OUT
IN
BATTERY
CIN
1µF
MAX8873
MAX8874
SHDN
GND
5 OUT
OUTPUT
VOLTAGE
COUT
1µF
SET
GND 2
MAX8873
MAX8874
SHDN 3
4 SET
SOT23-5
Dual Mode is a trademark of Maxim Integrated Products.
________________________________________________________________ Maxim Integrated Products
1
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
_______________General Description
The MAX8873T/S/R and MAX8874T/S/R low-dropout linear regulators operate from a +2.5V to +6.5V input
range and deliver up to 120mA. A PMOS pass transistor allows the low, 82µA supply current to remain independent 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 output 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.
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
ABSOLUTE MAXIMUM RATINGS
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
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
(VIN = +3.6V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
Input Voltage (Note 2)
Output Voltage
Adjustable Output Voltage
Range (Note 3)
SYMBOL
CONDITIONS
MIN
VIN
VOUT
0mA ≤ IOUT ≤ 50mA,
SET = GND
Ground Pin Current
MAX
UNITS
6.5
V
MAX887_T
3.05
3.15
3.25
MAX887_S
2.75
2.84
2.93
MAX887_R
2.70
2.80
2.88
VOUT
VSET
Maximum Output Current
Current Limit (Note 4)
TYP
2.5
6.5
120
ILIM
IQ
Dropout Voltage (Note 5)
IOUT = 0mA
73
IOUT = 50mA
82
150
1.1
IOUT = 50mA
55
120
0
0.15
SET = GND
0.011
0.030
SET tied to OUT
0.006
∆VLNR
VIN = 2.5V to 6.5V, SET tied to OUT,
IOUT = 1mA
Load Regulation
∆VLDR
IOUT = 0mA to 50mA
Output Voltage Noise
mA
IOUT = 1mA
Line Regulation
10Hz to 1MHz
-0.15
V
mA
280
SET = GND
V
COUT = 1µF
350
COUT = 100µF
220
µA
mV
%/V
%/mA
µVRMS
SHUTDOWN
SHDN Input Threshold
VIH
SHDN Input Bias Current
ISHDN
Shutdown Supply Current
IQSHDN
Shutdown Discharge
Resistance (MAX8874)
2
2.0
VIL
0.4
V SHDN = VIN
VOUT = 0V
TA = +25°C
0
TA = TMAX
0.05
TA = +25°C
0.0001
TA = TMAX
0.02
300
_______________________________________________________________________________________
100
1
V
nA
µA
Ω
Low-Dropout, 120mA Linear Regulators
(VIN = +3.6V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
TA = +25°C
1.225
1.25
1.275
TA = TMIN to TMAX
1.215
1.25
1.285
TA = +25°C
0.015
2.5
TA = TMAX
0.5
UNITS
SET INPUT
SET Reference Voltage (Note 3)
VSET
VIN = 2.5V to 6.5V,
IOUT = 1mA
SET Input Leakage Current
(Note 3)
ISET
VSET = 1.3V
V
nA
THERMAL PROTECTION
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
TSHDN
170
°C
∆TSHDN
20
°C
Note 1: Limits are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed through correlation 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.
__________________________________________Typical Operating Characteristics
(VIN = +3.6V, CIN = 1µF, COUT = 1µF, MAX887_T, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. LOAD CURRENT
3.5
MAX8873/74-02
3.25
95
3.0
3.20
3.15
3.10
OUTPUT VOLTAGE (V)
90
SUPPLY CURRENT (µA)
OUTPUT VOLTAGE (V)
100
MAX8873/74-01
3.30
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
MAX8873/74-03
OUTPUT VOLTAGE
vs. LOAD CURRENT
85
80
75
70
65
60
3.05
50
0
20
40
60
80
LOAD CURRENT (mA)
100
120
2.0
NO LOAD
1.5
1.0
0.5
55
3.00
2.5
0
0
20
40
60
80
LOAD CURRENT (mA)
100
120
0
1
2
3
4
5
6
7
INPUT VOLTAGE (V)
_______________________________________________________________________________________
3
MAX8873T/S/R, MAX8874T/S/R
ELECTRICAL CHARACTERISTICS (continued)
____________________________Typical Operating Characteristics (continued)
(VIN = +3.6V, CIN = 1µF, COUT = 1µF, MAX887_T, TA = +25°C, unless otherwise noted.)
OUTPUT VOLTAGE
vs. TEMPERATURE
70
ILOAD = 0mA
60
50
40
30
20
100
MAX8863/4-06
3.25
OUTPUT VOLTAGE (V)
ILOAD = 50mA
90
80
3.20
3.15
3.10
70
60
50
40
30
20
3.05
10
10
3.00
0
3
2
4
6
5
0
-40
7
-20
DROPOUT VOLTAGE
vs. LOAD CURRENT
70
MAX8873/74-07
TA = +85°C
80
60
100
PSRR (dB)
80
TA = -40°C
COUT = 10µF
40
30
COUT = 1µF
20
40
10
20
0
0
20
40
60
80
100
0
0.1
1
10
FREQUENCY (kHz)
100
100
COUT = 1µF
COUT = 100µF
0.10
1000
0.1
1
10
OUTPUT NOISE DC TO 1MHz
VOUT
STABLE REGION
0.1
0.01
0
20
40
60
80
LOAD CURRENT (mA)
4
100
100
1
EXTERNAL FEEDBACK
1
80
RL = 50Ω
INTERNAL FEEDBACK
10
60
10
MAX8873/74-8B
COUT = 1µF
40
FREQUENCY (kHz)
REGION OF STABLE COUT ESR
vs. LOAD CURRENT
1000
20
0.01
0.01
120
LOAD CURRENT (mA)
COUT ESR (Ω)
-20
OUTPUT SPECTRAL NOISE DENSITY
vs. FREQUENCY
50
TA = +25°C
0
-40
TEMPERATURE (°C)
VOUT = 3.15V
RL = 100Ω
60
120
60
40
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
160
100
20
TEMPERATURE (°C)
INPUT VOLTAGE (V)
140
0
OUTPUT SPECTRAL NOISE DENSITY (µV/√Hz)
1
MAX8873/74-08
0
MAX8873/74-8A
SUPPLY CURRENT (µA)
80
ILOAD = 50mA
SUPPLY CURRENT (µA)
ILOAD = 50mA
90
3.30
MAX8873/74-04
100
SUPPLY CURRENT
vs. TEMPERATURE
MAX8873/74-05
SUPPLY CURRENT
vs. INPUT VOLTAGE
DROPOUT VOLTAGE (mV)
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
120
1ms/div
ILOAD = 50mA, VOUT IS AC COUPLED
_______________________________________________________________________________________
100
1000
Low-Dropout, 120mA Linear Regulators
(VIN = +3.6V, CIN = 1µF, COUT = 1µF, MAX887_T, TA = +25°C, unless otherwise noted.)
LINE-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
3.16V
3.16V
VOUT 3.15V
VOUT 3.15V
3.14V
3.14V
VIN
50mA
4.6V
ILOAD
0mA
3.6V
50µs/div
ILOAD = 50mA, VOUT IS AC COUPLED
10µs/div
ILOAD = 0mA to 50mA, CIN = 10µF, VOUT IS AC COUPLED
LOAD-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
3.16V
3.16V
VOUT 3.15V
VOUT 3.15V
3.14V
3.14V
50mA
ILOAD
0mA
50mA
ILOAD
0mA
10µs/div
10µs/div
VIN = VOUT + 0.2V, ILOAD = 0mA to 50mA, CIN = 10µF,
VOUT IS AC COUPLED
VIN = VOUT + 0.1V, ILOAD = 0mA to 50mA, CIN = 10µF,
VOUT IS AC COUPLED
MAX8874 SHUTDOWN (NO LOAD)
MAX8874 SHUTDOWN
4V
VOUT
4V
2V
VOUT
0V
VSHDN
2V
0V
2V
VSHDN
0V
2V
0V
500µs/div
NO LOAD
200µs/div
ILOAD = 50mA
_______________________________________________________________________________________
5
MAX8873T/S/R, MAX8874T/S/R
____________________________Typical Operating Characteristics (continued)
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
______________________________________________________________Pin Description
PIN
NAME
FUNCTION
1
IN
2
GND
Ground. This pin also functions as a heatsink. Solder to large pads or the circuit board ground plane to maximize thermal dissipation.
3
SHDN
Active-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.
4
SET
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.
5
OUT
Regulator 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.
Regulator Input. Supply voltage can range from 2.5V to 6.5V. Bypass with 1µF to GND (see Capacitor
Selection and Regulator Stability).
_______________Detailed Description
The MAX8873/MAX8874 are low-dropout, low-quiescentcurrent linear regulators designed primarily for batterypowered 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
IN
SHDN
and applies the appropriate drive to the P-channel pass
transistor. If the feedback voltage is lower than the reference, 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 shutdown logic.
REVERSE
BATTERY
PROTECTION
ERROR
AMP
MAX8873
MAX8874
MOS DRIVER
WITH ILIMIT
P
OUT
SHUTDOWN
LOGIC
N
*
THERMAL
SENSOR
1.25V
REF
DUAL-MODE
COMPARATOR
60mV
GND
* AUTO-DISCHARGE, MAX8874 ONLY
Figure 1. Functional Diagram
6
_______________________________________________________________________________________
SET
Low-Dropout, 120mA Linear Regulators
3
CIN
BATTERY 1µF
OUT
IN
MAX8873
MAX8874
SHDN
OUTPUT
VOLTAGE
5
R1 20pF
SET
4
COUT
1µF
RL
GND
2
R2
Shutdown
Figure 2. Adjustable Output Using External Feedback
Resistors
Internal P-Channel Pass Transistor
The MAX8873/MAX8874 feature a 1.1Ω typical P-channel MOSFET pass transistor. This provides several
advantages over similar designs using PNP pass transistors, including longer battery life.
The P-channel MOSFET requires no base drive current,
which reduces quiescent current considerably. PNPbased regulators waste considerable amounts of current 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 problems, and consume only 82µA of quiescent current,
whether in dropout, light load, or heavy load applications (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:
V
R1 = R2  OUT
 VSET


− 1


A low input on the SHDN pin shuts down the
MAX8873/MAX8874. In shutdown mode, the pass transistor, 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 voltage, 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 dissipation in the MAX8873/MAX8874. When the junction temperature exceeds T J = +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 temperatures above +125°C) may cause a momentary overshoot (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 maximum junction temperature rating of TJ = +150°C.
_______________________________________________________________________________________
7
MAX8873T/S/R, MAX8874T/S/R
1
Choose R2 = 100kΩ to 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 output can be set using fixed resistors instead of trim pots.
Connect a 10pF to 25pF capacitor across R1 to compensate 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.
MAX8873T/S/R, MAX8874T/S/R
Low-Dropout, 120mA Linear Regulators
Operating Region and Power Dissipation
Noise
Maximum power dissipation of the MAX8873/MAX8874
depends on the thermal resistance of the case and circuit 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
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.
where (TJ - TA) is the temperature difference between
the MAX8873/MAX8874 die junction and the surrounding 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 V SHDN falls below ground.
The circuitry monitors the polarity of these two pins, disconnecting the internal circuitry and parasitic diodes
when the battery is reversed. This feature prevents the
device from overheating and damaging the battery.
VIN > 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 minimum 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 currents up to 120mA, a minimum of 1µF is recommended.
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 batterypowered systems. Power-supply rejection is 62dB at
low frequencies and rolls off above 300Hz. As the frequency 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 capacitors, 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 supply voltage. In battery-powered systems, this will determine 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 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1998 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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