19-2532; Rev 6; 2/11
KIT
ATION
EVALU
E
L
B
AVAILA
300mA LDO Linear Regulators with
Internal Microprocessor Reset Circuit
The MAX6469–MAX6484 are low-dropout linear regulators with a fully integrated microprocessor reset circuit.
Each is available with preset output voltages from +1.5V
to +3.3V in 100mV increments and delivers up to 300mA
of load current. These devices consume only 82µA of
supply current. The low supply current, low dropout voltage, and integrated reset functionality make these
devices ideal for battery-powered portable equipment.
The MAX6469–MAX6484 include a reset output that indicates when the regulator output drops below standard
microprocessor supply tolerances (-7.5% or -12.5% of
nominal output voltage). This eliminates the need for an
external microprocessor supervisor, while ensuring that
supply voltages and clock oscillators have stabilized
before processor activity is enabled. Push-pull and opendrain active-low reset outputs are available, with reset
timeout periods of 2.5ms, 20ms, 150ms, or 1200ms (min).
The MAX6469/MAX6470/MAX6473–MAX6478/MAX6481–
MAX6484 also have a shutdown feature that reduces the
supply current to 0.1µA (typ). The MAX6471–MAX6474/
MAX6479–MAX6482 offer a manual reset input to assert a
microprocessor reset while the regulator output is within
specification. The MAX6475/MAX6476/MAX6483/
MAX6484 feature a remote feedback sense pin for use
with an external NPN transistor for higher-current applications. The MAX6469–MAX6476 are available in 6-pin
SOT23 and 8-pin TDFN packages. The MAX6477–
MAX6484 are available in a 3 × 3 chip-scale package
(UCSP™). All devices are specified for operation from
-40°C to +85°C.
Applications
Handheld Instruments (PDAs, Palmtops)
PCMCIA Cards/USB Devices
Cellular/Cordless Telephones
CD/DVD Drives
Notebook Computers
Digital Cameras
Bluetooth Modules/Wireless LAN
UCSP is a trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
Typical Operating Circuits appear at end of data sheet.
Features
o 3 3 UCSP, 6-Pin SOT23, and 8-Pin TDFN
Packages
o Preset +1.5V to +3.3V Output (100mV Increments)
o SET Pin for Adjustable Output Voltage
o 75µVRMS LDO Output Voltage Noise
(MAX6477–MAX6484)
o ±2.0% Accuracy Over Temperature
o Guaranteed 300mA Output Current
o Low Dropout Voltage
55mV at 150mA
114mV at 300mA
o 82µA Supply Current, 0.1µA Shutdown Current
o Input Reverse Current, Thermal and Short-Circuit
Protection
o Microprocessor Reset with Four Timeout Options
o Push-Pull or Open-Drain RESET
o Manual Reset Input
o Remote Feedback Sense
Ordering Information
TEMP RANGE
PINPACKAGE
MAX6469UT_ _ _D_-T
-40°C to +85°C
6 SOT23-6
MAX6469TA_ _ _D_-T**
-40°C to +85°C
8 TDFN-EP***
MAX6470UT_ _ _D_-T
-40°C to +85°C
6 SOT23-6
MAX6470TA_ _ _D_-T**
-40°C to +85°C
8 TDFN-EP***
PART*
Ordering Information continued at end of data sheet.
*Devices are also available in a lead(Pb)-free/RoHS-compliant
packages. Specify lead(Pb)-free by substituting a +T instead of
a -T when ordering.
**Future product—contact factory for availability.
***EP = Exposed pad.
Note: The first “_ _” are placeholders for the output voltage levels of the devices. Desired output voltages are set by the suffix
found in the Output Voltage Suffix Guide (Table 1). The third “_”
is a placeholder for the reset threshold accuracy. Desired reset
threshold accuracy is set by the suffix found in the Reset
Threshold Accuracy Guide (Table 2). The “_” following the D is
a placeholder for the reset timeout delay time. Desired reset
timeout delay time is set by the suffix found in the Reset
Timeout Delay Guide (Table 3). For example, the
MAX6481BL30BD4-T has a 3.0V output voltage, 12.5% reset
threshold tolerance, and a 1200ms (min) reset timeout delay.
Sample stock is generally available on standard versions only
(Table 4). Standard versions require a minimum order increment of 2.5k units. Nonstandard versions must be ordered in
10k-unit increments. Contact factory for availability.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
MAX6469–MAX6484
General Description
MAX6469–MAX6484
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.)
IN, SHDN, OUT, FB ..................................................-0.3V to +7V
MR, SET .......................................................-0.3V to (VIN + 0.3V)
RESET (push-pull) ...................................-0.3V to (VOUT + 0.3V)
RESET (open drain)..................................................-0.3V to +7V
OUT Short Circuit .......................................................Continuous
Input/Output Current (all pins except IN and OUT) ............20mA
Continuous Power Dissipation (TA = +70°C)
3 x 3 UCSP (derate 10.5mW/°C above +70°C) ............840mW
6-Pin SOT23 (derate 9.1mW/°C above +70°C).............727mW
8-Pin TDFN (derate 24.4mW/°C above +70°C) ..........1951mW
Operating Temperature Range ..........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow)
Lead(Pb)-free packages...............................................+260°C
Packages containing lead(Pb)......................................+240°C
Note 1: The MAX6477–MAX6484 are constructed using a unique set of packaging techniques that impose a limit on the thermal profile the devices can be exposed to during board-level solder attach and rework. This limit permits only the use of the solder
profiles recommended in the industry-standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and
Convection reflow. Pre-heating is required. Hand or wave soldering is not allowed.
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 = (VOUT + 0.5V) or +2.5V, whichever is greater, COUT = 3.3µF, TA = -40°C to +85°C. Typical specifications are at TA = +25°C,
unless otherwise noted.) (Note 2)
PARAMETER
Input Voltage Range
Input Undervoltage Lockout
Supply Current (Ground Current)
Shutdown Supply Current
SYMBOL
CONDITIONS
VIN
VUVLO
IQ
ISHDN
VIN falling
IOUT = 0A
IOUT = 300mA
Output Voltage Accuracy (Fixed
Output Voltage Operation,
Table 1) MAX6477–MAX6484
Adjustable Output Voltage Range
SET Reference Voltage
SET Dual ModeTM Threshold
SET Input Leakage Current
82
96
0.1
UNITS
5.5
2.47
136
V
V
1
300
-1.3
-2.3
+1.3
+2.3
1mA ≤ IOUT ≤ 300mA, TA = -40°C to +85°C
-2.7
+2.7
2mA ≤ IOUT ≤ 100mA, TA = +25°C
-1.1
+1.1
2mA ≤ IOUT ≤ 100mA, TA = -40°C to +85°C
-2.0
+2.0
2mA ≤ IOUT ≤ 300mA, TA = -40°C to +85°C
(Note 3)
-2.5
+2.5
VSET
1.200
VSET = 0V, +1.2V (Note 3)
µA
µA
mA
1.229
185
±20
Dual Mode is a trademark of Maxim Integrated Products, Inc.
2
MAX
1mA ≤ IOUT ≤ 150mA, TA = +25°C
1mA ≤ IOUT ≤ 150mA, TA = -40°C to +85°C
VSET
ISET
TYP
2.5
2.25
TA = +25°C
REGULATOR CIRCUIT
Output Current
Output Voltage Accuracy (Fixed
Output Voltage Operation,
Table 1) MAX6469–MAX6476
MIN
_______________________________________________________________________________________
5.0
1.258
±100
%
%
V
V
mV
nA
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
(VIN = (VOUT + 0.5V) or +2.5V, whichever is greater, COUT = 3.3µF, TA = -40°C to +85°C. Typical specifications are at TA = +25°C,
unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
VOUT = +3.3V
(fixed output operation)
VOUT = +3.0V
(fixed output operation)
Dropout Voltage
(Notes 3, 4)
∆VDO
VOUT = +2.8V
(fixed output operation)
VOUT = +2.5V
(fixed output operation)
Output Current Limit
VIN ≥ 2.5V (Note 3)
Input Reverse Leakage Current
(OUT to IN Leakage Current)
VIN = 4V, VOUT = 5.5V, SHDN deasserted
Startup Time Response
Rising edge of VIN or SHDN to VOUT
within specification, RL = 68Ω, SET = GND,
IOUT = 10mA
SHDN Input Low Voltage
VIL
SHDN Input High Voltage
VIH
SHDN Input Current
Thermal-Shutdown Temperature
Thermal-Shutdown Hysteresis
MIN
IOUT = 50mA
IOUT = 150mA
IOUT = 300mA
IOUT = 50mA
IOUT = 150mA
IOUT = 300mA
IOUT = 50mA
IOUT = 150mA
IOUT = 300mA
IOUT = 50mA
IOUT = 150mA
IOUT = 300mA
TYP
MAX
UNITS
23
55
114
25
61
114
26
65
137
30
75
158
32
90
180
40
100
190
50
110
210
60
150
250
mV
450
mA
0.01
1.5
20
µs
0.3 × VIN
V
+1
µA
0.7 × VIN
VSHDN = VIN or VGND
-1
TSHDN
∆TSHDN
µA
V
0.1
180
°C
20
°C
Line Regulation
VOUT = 1.5V, 2.5V ≤ VIN ≤ 5.5V,
IOUT = 10mA
0.09
%/V
Load Regulation
VOUT = 1.5V, VIN = 2.5V, 1mA ≤ IOUT ≤
150mA
0.2
%
Output Voltage Noise
10Hz to 100kHz,
CIN = 0.1µF,
IOUT = 100mA,
VOUT = 1.5V
MAX6469–MAX6476
150
MAX6477–MAX6484
75
µVRMS
RESET CIRCUIT
VOUT Reset Threshold
(VFB for MAX6475/MAX6476/
MAX6483/MAX6484) (Note 5)
VTHOUT
MAX64_ _ _ _ _ _ A
90
92.5
95
MAX64_ _ _ _ _ _ B
85
87.5
90
VOUT to Reset Delay
(VFB for MAX6475/MAX6476/
MAX6483/MAX6484)
Reset Timeout Period
(Note 6)
35
tRP
%VOUT
µs
D1
2.5
3.75
D2
20
30
5.0
40
D3
150
225
300
D4
1200
1800
2400
ms
_______________________________________________________________________________________
3
MAX6469–MAX6484
ELECTRICAL CHARACTERISTICS (continued)
ELECTRICAL CHARACTERISTICS (continued)
(VIN = (VOUT + 0.5V) or +2.5V, whichever is greater, COUT = 3.3µF, TA = -40°C to +85°C. Typical specifications are at TA = +25°C,
unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
MR Input Low Voltage
VIL
MR Input High Voltage
VIH
CONDITIONS
MIN
TYP
MAX
UNITS
0.3 ×
VOUT
V
0.7 ×
VOUT
(Note 3)
MR Minimum Input Pulse
V
1
µs
MR Glitch Rejection
120
ns
MR to Reset Delay
200
ns
MR Pullup Resistance
MR to OUT
RESET Output Voltage
(Open Drain)
VOL
VOUT ≥ 1.0V, ISINK = 50µA, RESET asserted
0.3
VOUT ≥ 1.5V, ISINK = 3.2mA, RESET asserted
0.4
Open-Drain Reset Output
Leakage Current
ILKG
40
70
V
µA
0.3
VOUT ≥ 1.5V, ISINK = 3.2mA, RESET asserted
0.4
VOUT ≥ 2.0V, ISOURCE = 500µA, RESET
deasserted
VOH
kΩ
1
VOUT ≥ 1.0V, ISINK = 50µA, RESET asserted
RESET Output Voltage Push-Pull
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
25
(Note 3)
VOL
0.8 ×
VOUT
V
All devices are 100% production tested at +25°C and are guaranteed by correlation for TA = TMIN to TMAX.
Guaranteed by design.
Dropout voltage is defined as (VIN - VOUT) when VOUT is 2% below the value of VOUT for VIN = VOUT(NOM) + 1V.
MAX6473/MAX6474/MAX6481/MAX6482 are guaranteed by design for VOUT < 2.5V.
Select the reset timeout period using the Reset Timeout Delay Guide (Table 3). Insert the appropriate suffix in the part number
when ordering.
Typical Operating Characteristics
(VIN = 5V, VOUT = 3.3V, COUT = 3.3µF, TA = +25°C, unless otherwise noted.)
60
40
20
1
2
3
4
INPUT VOLTAGE (V)
5
6
150
MAX6469 toc02
80
60
+25°C
-40°C
40
125
RESET ASSERTS ABOVE
THIS LINE
100
75
50
25
0
0
4
+85°C
20
0
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
PULSE DURATION (µs)
-40°C
80
100
GROUND CURRENT (µA)
+85°C
+25°C
100
120
MAX6469 toc01
120
GROUND CURRENT vs. INPUT VOLTAGE
(300mA LOAD)
MAX6469 toc03
GROUND CURRENT vs. INPUT VOLTAGE
(NO LOAD)
GROUND CURRENT (µA)
MAX6469–MAX6484
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
0
0
1
2
3
4
INPUT VOLTAGE (V)
5
6
10
1
RESET THRESHOLD OVERDRIVE (mV)
_______________________________________________________________________________________
100
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
DROPOUT VOLTAGE vs. LOAD CURRENT
-10
VOUT = 3.3V
COUT = 3.3µF
ILOAD = 30mA
PSRR (dB)
50
4
COUT ESR (Ω)
-20
75
-30
MAX6469 toc06
100
5
MAX6469 toc05
VOUT = 3.3V
COUT = 3.3µF
3
COUT = 4.7µF
2
COUT = 3.3µF
-40
25
1
-50
STABLE REGION
0
0
-60
50
100
150
200
250
300
0.01
0.1
OUTPUT NOISE
MAX6469 toc07
100
1000
0
50
100
150
200
LOAD CURRENT (mA)
OUTPUT NOISE vs. FREQUENCY
SHUTDOWN RESPONSE
VIN = 2.5V
VOUT = 1.5V
IOUT = 100mA
80
100µV/div
10
250
300
MAX6469 toc09
100
VIN = 4.5V
VOUT = 3.3V
ILOAD = 100mA
1
FREQUENCY (kHz)
LOAD CURRENT (mA)
MAX6469 toc08
0
VRMS (µV)
DROPOUT VOLTAGE (mV)
0
MAX6469 toc04
125
REGION OF STABLE COUT ESR
vs. LOAD CURRENT
PSRR vs. FREQUENCY
MAX6469–MAX6484
Typical Operating Characteristics (continued)
(VIN = 5V, VOUT = 3.3V, COUT = 3.3µF, TA = +25°C, unless otherwise noted.)
VSHDN
5V/div
60
40
VOUT
2V/div
20
ILOAD = 50mA
0
10
500µs/div
100
1k
10k
100k
20ms/div
FREQUENCY (Hz)
STARTUP RESPONSE
MAX6469 toc10
MAX6469 toc12
MAX6469 toc11
VIN
2V/div
VIN = 5V
VOUT = 3.3V
ILOAD = 100mA
VIN = 5V
VOUT = 3.3V
ILOAD = 10mA TO 300mA
VOUT
5mV/div
VOUT
20mV/div
VOUT
2V/div
10µs/div
LOAD-TRANSIENT RESPONSE
NEAR DROPOUT
LOAD-TRANSIENT RESPONSE
100µs/div
10µs/div
_______________________________________________________________________________________
5
Typical Operating Characteristics (continued)
(VIN = 5V, VOUT = 3.3V, COUT = 3.3µF, TA = +25°C, unless otherwise noted.)
LINE-TRANSIENT RESPONSE
RESET RESPONSE TO MR
RESET DELAY RESPONSE
MAX6469 toc13
MAX6469 toc15
MAX6469 toc14
5V
4.5V
VIN
500mV/div
VIN
1V TO 4V
2V/div
MR
2V/div
RESET
2V/div
RESET
2V/div
VOUT
20mV/div
AC-COUPLED
VOUT = 3.3V
ILOAD = 10mA
100µs/div
200ns/div
200ms/div
MAX6469 toc16
1.012
RESET
2V/div
VOUT
2V/div
VIN
5V/div
MAX6469 toc17
NORMALIZED OUTPUT VOLTAGE
vs. TEMPERATURE
RESET RESPONSE TO VIN RISING
NORMALIZED OUTPUT VOLTAGE
MAX6469–MAX6484
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
NORMALIZED TO +25°C
1.006
ILOAD = 10mA
1.000
0.994
ILOAD = 150mA
ILOAD = 300mA
0.988
200ms/div
-40
-15
10
35
60
TEMPERATURE (°C)
6
_______________________________________________________________________________________
85
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
PIN
BUMP
MAX6469/MAX6470
MAX6477/MAX6478
SOT23
TDFN-EP
UCSP
1
1, 2
A1
NAME
IN
FUNCTION
Regulator Input. Bypass IN to GND with a 0.1µF capacitor.
2
3
A2
GND
Ground. This pin also functions as a heatsink. Solder to large pads or
the circuit-board ground plane to maximize thermal dissipation.
3
4
A3
SHDN
Active-Low Shutdown Input. Connect SHDN to VIN for normal operation.
4
5
C3
RESET
Active-Low Reset Output. RESET remains low while VOUT is below the
reset threshold. RESET remains low for the duration of the reset timeout
period after the reset conditions are terminated. RESET is available in
open-drain and push-pull configurations.
5
6
C2
SET
Feedback Input for Externally Setting the Output Voltage. Connect SET
to GND to select the preset output voltage. Connect SET to an external
resistor-divider network for adjustable output operation.
6
7, 8
C1
OUT
Regulator Output. Bypass OUT to GND with a minimum 3.3µF low-ESR
capacitor.
—
—
—
EP
Exposed Paddle (TDFN Only). EP is internally connected to GND.
Connect EP to the ground plane to provide a low thermal-resistance
path from the IC junction to the PCB. Do not use as the electrical
connection to GND.
MAX6471/MAX6472/MAX6479/MAX6480 Pin Description
PIN
BUMP
MAX6471/MAX6472
MAX6479/MAX6480
SOT23
TDFN-EP
UCSP
1
1, 2
A1
2
3
3
4
A2
A3
NAME
IN
GND
MR
Active-Low Reset Output. RESET remains low while VOUT is below the
reset threshold or while MR is held low. RESET remains low for the
duration of the reset timeout period after the reset conditions are
terminated. RESET is available in open-drain and push-pull
configurations.
5
C3
RESET
5
6
C2
SET
6
7, 8
C1
OUT
—
—
Regulator Input. Bypass IN to GND with a 0.1µF capacitor.
Ground. This pin also functions as a heatsink. Solder to large pads or
the circuit-board ground plane to maximize thermal dissipation.
Active-Low Manual Reset Input. The reset output is asserted while MR
is pulled low and remains asserted for the duration of the reset timeout
period after MR transitions from low to high. Leave MR unconnected or
connect to VOUT if not used. MR has an internal pullup resistor of 40kΩ
(typ) to VOUT.
4
—
FUNCTION
EP
Feedback Input for Externally Setting the Output Voltage. Connect SET
to GND to select the preset output voltage. Connect SET to an external
resistor-divider network for adjustable output operation.
Regulator Output. Bypass OUT to GND with a minimum 3.3µF low-ESR
capacitor.
Exposed Paddle (TDFN Only). EP is internally connected to GND.
Connect EP to the ground plane to provide a low thermal-resistance
path from the IC junction to the PCB. Do not use as the electrical
connection to GND.
_______________________________________________________________________________________
7
MAX6469–MAX6484
MAX6469/MAX6470/MAX6477/MAX6478 Pin Description
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
MAX6469–MAX6484
MAX6473/MAX6474/MAX6481/MAX6482 Pin Description
PIN
BUMP
MAX6473/MAX6474
MAX6481/MAX6482
NAME
FUNCTION
SOT23
TDFN-EP
UCSP
1
1, 2
A1
IN
2
3
A2
GND
Ground. This pin also functions as a heatsink. Solder to large pads or
the circuit-board ground plane to maximize thermal dissipation.
3
4
A3
SHDN
Active-Low Shutdown Input. Connect SHDN to VIN for normal operation.
RESET
Active-Low Reset Output. RESET remains low while VOUT is below the
reset threshold or while MR is held low. RESET remains low for the
duration of the reset timeout period after the reset conditions are
terminated. RESET is available in open-drain and push-pull
configurations.
Active-Low Manual Reset Input. The reset output is asserted while MR
is pulled low and remains asserted for the duration of the reset timeout
period after MR transitions from low to high. Leave MR unconnected or
connect to VOUT if not used. MR has an internal pullup resistor of 40kΩ
(typ) to VOUT.
4
5
C3
Regulator Input. Bypass IN to GND with a 0.1µF capacitor.
5
6
C2
MR
6
7, 8
C1
OUT
Regulator Output. Bypass OUT to GND with a minimum 3.3µF (min)
low-ESR capacitor.
EP
Exposed Paddle (TDFN Only). EP is internally connected to GND.
Connect EP to the ground plane to provide a low thermal-resistance
path from the IC junction to the PCB. Do not use as the electrical
connection to GND.
—
—
—
MAX6475/MAX6476/MAX6483/MAX6484 Pin Description
PIN
BUMP
MAX6475/MAX6476
MAX6483/MAX6484
FUNCTION
TDFN-EP
UCSP
1
1, 2
A1
IN
2
3
A2
GND
Ground. This pin also functions as a heatsink. Solder to large pads or
the circuit-board ground plane to maximize thermal dissipation.
3
4
A3
SHDN
Active-Low Shutdown Input. Connect SHDN to VIN for normal operation.
Regulator Input. Bypass IN to GND with a 0.1µF capacitor.
4
5
C3
RESET
Active-Low Reset Output. RESET remains low while FB is below the
reset threshold. RESET remains low for the duration of the reset timeout
period after the reset conditions are terminated. RESET is available in
open-drain and push-pull configurations.
5
6
C2
FB
Feedback Input for Linear Regulator Controller or Remote Sense
Applications. Connect FB to the external load (VCC) to obtain the fixed
output voltage.
6
7, 8
C1
OUT
Regulator Output. Bypass OUT to GND with a minimum 3.3µF low-ESR
capacitor.
—
8
NAME
SOT23
—
—
EP
Exposed Paddle (TDFN Only). EP is internally connected to GND.
Connect EP to the ground plane to provide a low thermal-resistance path
from the IC junction to the PCB. Do not use as the electrical connection
to GND.
_______________________________________________________________________________________
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
2.5V TO 5.5V
IN
OUT
MAX6469–MAX6472
MAX6477–MAX6480
SET
(MR)
MANUAL
RESET
R1
COUT
GND
R2
Regulator
The regulator core operates with +2.5V to +5.5V input
voltage range. The output voltage is offered in 100mV
increments between +1.5V and +3.3V (contact factory
for other output voltage options). The MAX6469–
MAX6472/MAX6477–MAX6480 offer an adjustable output voltage implemented with an external resistordivider network between OUT, SET, and GND (Figure
1). SET must be connected to either GND for fixed
VOUT or to an external divider for adjustable VOUT. The
MAX6469–MAX6472/MAX6477–MAX6480 automatically
determine the feedback path depending on the connection of SET. The Typical Operating Circuit shows a
typical connection for the MAX6469. OUT is an internally regulated low-dropout (LDO) linear regulator that
powers a microprocessor.
Reset Circuit
The reset supervisor circuit is fully integrated in the
MAX6469–MAX6484 and uses the same reference voltage as the regulator. Two supply tolerance reset
thresholds, -7.5% and -12.5%, are provided for each
type of device.
-7.5% Reset: Reset does not assert until the regulator
output voltage is at least -5% out of tolerance and
always asserts before the regulator output voltage is
-10% out of tolerance.
-12.5% Reset: Reset does not assert until the regulator
output voltage is at least -10% out of tolerance and
always asserts before the regulator output voltage is
-15% out of tolerance.
RESET Output
A µP’s reset input starts the µP in a known state. The
MAX6469–MAX6484 µP supervisory circuits assert
RESET during power-up, power-down, and brownout
conditions. RESET asserts when the input voltage is
below the undervoltage lockout threshold. RESET
asserts when VOUT is below the reset threshold and
remains asserted for at least the minimum selected reset
timeout period (tRP, Table 3) after VIN rises above the
undervoltage lockout threshold and VOUT rises above
( ) ARE FOR MAX6471/MAX6472/MAX6479/MAX6480 ONLY
Figure 1. Adjustable Output Voltage Configuration
the reset threshold. RESET asserts when MR is pulled
low (MAX6471–MAX6474/MAX6479–MAX6482). RESET
asserts when SHDN is pulled low (MAX6469/
MAX6470/MAX6473–MAX6478/MAX6481–MAX6484).
Shutdown
(MAX6469/MAX6470/MAX6473–MAX6478/MAX6481–
MAX6484 only)
SHDN allows the regulator to shut down, thereby reducing the total IIN consumption of the device. SHDN provides a digitally controlled active-low shutdown. In
shutdown mode, the pass transistor, control circuit, and
reference turn off to reduce the supply current to below
0.1µA. Connect SHDN to IN for normal operation.
Manual Reset Input
(MAX6471–MAX6474/MAX6479–MAX6482 only)
Many µP-based products require manual reset capability, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. A logic low on MR
asserts reset while the regulator output voltage is still
within tolerance.
Reset remains asserted while MR is low and for the
reset timeout period (tRP) after MR returns high. The
MR input has an internal pullup of 40kΩ (typ) to OUT.
MR can be driven with TTL/CMOS logic levels or with
open-drain/collector outputs. Connect a normally open
switch from MR to GND to create a manual reset function; external debounce circuitry is not required. If MR
is driven from long cables or the device is used in a
noisy environment, connect a 0.1µF capacitor from MR
to GND to provide additional noise immunity.
Feedback Input
(MAX6475/MAX6476/MAX6483/MAX6484 only)
The feedback input (FB) connects to an internal resistordivider network (Functional Diagram). FB is not internally
connected to VOUT, and as a result can be used to
_______________________________________________________________________________________
9
MAX6469–MAX6484
Detailed Description
The MAX6469–MAX6484 are ultra-low, quiescent current, low-dropout linear regulators with an integrated
microprocessor reset circuit. These devices guarantee
300mA (min) drive capabilities and are available with
preset output voltages in 100mV increments between
+1.5V and +3.3V. The internal reset circuit monitors the
regulator output voltage and asserts the reset output
when the regulator output is below the microprocessor
supply tolerance.
MAX6469–MAX6484
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
remotely sense the output voltage of the device. Using
FB with an external npn transistor, the current drive capability can be increased according to the following equation (Figure 2):
IOUT(TOTAL) = IOUT (β+1)
The external npn pass transistor must meet specifications for current gain, power dissipation, and collector
current. The beta influences the maximum output current the circuit can deliver. The largest guaranteed output current is given by ILOAD (max) = 300mA × beta
(min). The transistor’s rated power dissipation must
exceed the actual power dissipated in the transistor.
The power dissipated (PD) equals the maximum load
current (ILOAD (max)) times the maximum input-to-output voltage differential: PD = ILOAD (max) × (VIN (max) V OUT ). The rated transistor collector current must
exceed the maximum load current.
Reverse Leakage Protection
Reverse OUT to IN Current
An internal circuit monitors the MAX6469–MAX6484
input and output voltages. When the output voltage is
greater than the input voltage, the internal IN-to-OUT
pass transistor and parasitic diode turn off. An external
voltage applied to OUT does not reverse charge a battery or power source applied to IN (the leakage path
from OUT to IN is 0.01µA typ). When the output voltage
exceeds the input voltage, OUT powers the device and
shutdown must be logic high (greater than 0.7 VOUT).
RESET asserts until IN exceeds OUT and OUT is above
the specified VTHOUT threshold (based on the selected
or adjusted regulator OUT nominal voltage).
OUT-to-GND current through the LDO is 40µA (typ). The
regulator output can be held up with an external super
capacitor or backup battery at OUT until the IN battery is
replaced. The RESET output is asserted while the IN battery is removed to place the system in a low-power
mode. Volatile memory content is maintained until the
super capacitor or battery voltage drops below RAM
standby specifications. RESET deasserts when the IN
battery has been replaced and OUT exceeds the
desired reset threshold. For nonrechargeable backup
battery applications, place a reverse diode between
OUT and the backup battery (to prevent battery charging). The external diode does not affect the regulator’s
dropout voltage because it is not between the LDO output and the processor/memory VCC supply. The diode
can be replaced with a current-limiting resistor for
rechargeable backup battery applications.
Current Limit
The MAX6469–MAX6484 include an internal currentlimit circuit that monitors and controls the pass transistor’s gate voltage, limiting the output current to 450mA
(min). The output can be shorted to ground indefinitely
without damaging the part.
Thermal Shutdown
When the junction temperature (TJ) exceeds +180°C
(typ), the thermal sensor signals the shutdown logic,
turning off the pass transistor and allowing the IC to
REMOVABLE
LITHIUM ION OR
3-CELL
ALKALINE
IN
Reverse OUT to Ground Current
The MAX6469–MAX6484 maintain a low OUT-to-GND
reverse-current flow when the IN power source is
removed. When IN floats (input battery removed) and
SHDN is pulled up to VOUT (by an external diode), the
OUT
MAX6469–
MAX6484
3.3µF
3.0V
LITHIUM
µP
MEMORY
µP
MEMORY
SHDN
5.0V
1A TOTAL CURRENT
IN
VCC = 3.3V
REMOVABLE
LITHIUM ION OR
3-CELL
ALKALINE
OUT
IN
OUT
MAX6475/MAX6476
MAX6483/MAX6484
330Ω
3.3µF
0.1µF
MAX6469–
MAX6484
RPULLUP
FB
µP
3.3µF
SUPERCAP
SHDN
GND
RESET
Figure 2. High-Current, External Transistor Application
10
Figure 3. Battery Backup
______________________________________________________________________________________
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
Operating Region and Power Dissipation
The MAX6469–MAX6484’s maximum power dissipation
depends on the thermal resistance of the case and circuit board, the temperature difference between the die
junction and the ambient air, and the rate of airflow. The
power dissipation across the device is:
P = IOUT (VIN - VOUT)
The maximum power dissipation is:
PMAX = (TJ - TA) / (ØJB + ØBA)
where TJ - TA is the temperature difference between the
die junction and the surrounding air, ØJB (or ØJC) is the
thermal resistance of the package, and ØBA is the thermal resistance through the PC board, copper traces,
and other materials to the surrounding air. The
MAX6469–MAX6476 TDFN package ØJC = 41°C/W,
and the MAX6469–MAX6476 SOT package Ø JC =
110°C/W.
The MAX6469–MAX6484’s ground pin (GND) performs
the dual function of providing an electrical connection
to the system ground and channeling heat away.
Connect GND to the system ground using a large pad
or ground plane. For continuous operation, do not
exceed the absolute maximum junction temperature
rating of TJMAX = +150°C.
Applications Information
Choose R2 = 50kΩ to maintain stability, accuracy and
high-frequency power-supply rejection. Avoid selecting
resistor values greater than 100kΩ. In preset voltage
mode, the impedance between SET and ground should
always be less than 50kΩ. In most applications, connect SET directly to ground.
Low-Noise UCSP Output
MAX6477–MAX6484 UCSP products include internal filtering to yield low output noise without an additional
external bypass capacitor. The devices yield 75µVRMS
(typ) output noise (for VOUT = 3.0V) and 150µVRMS (for
V OUT = 3.3V). This low-noise feature makes the
MAX6477–MAX6484 ideal for audio applications.
Capacitor Selection and Regulator
Stability
For stable operation over the full temperature range
and with load currents up to 300mA, use a 3.3µF (min)
ceramic output capacitor with an ESR
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