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PDF MAX6475 Data sheet ( Hoja de datos )
| Número de pieza | MAX6475 | |
| Descripción | 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit | |
| Fabricantes | Maxim Integrated | |
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19-2532; Rev 2; 6/03
EVAALVUAAILTAIOBNLEKIT
300mA LDO Linear Regulators with
Internal Microprocessor Reset Circuit
General Description
The MAX6469–MAX6484 are low-dropout linear regula-
tors 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 volt-
age, and integrated reset functionality make these
devices ideal for battery-powered portable equipment.
The MAX6469–MAX6484 include a reset output that indi-
cates 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 open-
drain 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 applica-
tions. The MAX6469–MAX6476 are available in 6-pin
SOT23 and 8-pin thin QFN 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
Hand-Held 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 QFN 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
PART
TEMP RANGE
PIN-
PACKAGE
MAX6469UT_ _ _D_-T -40°C to +85°C 6 SOT23-6
MAX6469TA_ _ _D_*
-40°C to +85°C 8 Thin QFN
MAX6470UT_ _ _D_-T -40°C to +85°C 6 SOT23-6
MAX6470TA_ _ _D_*
-40°C to +85°C 8 Thin QFN
*Future product—contact factory for availability.
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 avail-
able 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.
Ordering Information continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
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 page  
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
Typical Operating Characteristics (continued)
(VIN = 5V, VOUT = 3.3V, COUT = 3.3µF, TA = +25°C, unless otherwise noted.)
DROPOUT VOLTAGE vs. LOAD CURRENT
125
VOUT = 3.3V
COUT = 3.3µF
100
75
50
25
0
0 50 100 150 200 250 300
LOAD CURRENT (mA)
PSRR vs. FREQUENCY
0
VOUT = 3.3V
COUT = 3.3µF
-10 ILOAD = 30mA
-20
-30
-40
-50
-60
0.01
0.1 1 10 100
FREQUENCY (kHz)
1000
REGION OF STABLE COUT ESR
vs. LOAD CURRENT
5
4
3
COUT = 4.7µF
2
COUT = 3.3µF
1
STABLE REGION
0
0 50 100 150 200
LOAD CURRENT (mA)
250
300
OUTPUT NOISE
VIN = 4.5V
VOUT = 3.3V
ILOAD = 100mA
MAX6469 toc07
OUTPUT NOISE vs. FREQUENCY
100
VIN = 2.5V
VOUT = 1.5V
80 IOUT = 100mA
100µV/div
60
40
20
500µs/div
0
10
100 1k
10k
FREQUENCY (Hz)
100k
STARTUP RESPONSE
MAX6469 toc10
VIN
2V/div
LOAD-TRANSIENT RESPONSE
MAX6469 toc11
SHUTDOWN RESPONSE
MAX6469 toc09
VSHDN
5V/div
ILOAD = 50mA
20ms/div
VOUT
2V/div
LOAD-TRANSIENT RESPONSE
NEAR DROPOUT
MAX6469 toc12
VIN = 5V
VOUT = 3.3V
ILOAD = 100mA
VOUT
2V/div
VOUT
20mV/div
VOUT
5mV/div
10µs/div
100µs/div
10µs/div
_______________________________________________________________________________________ 5
5 Page 
300mA LDO Linear Regulators with Internal
Microprocessor Reset Circuit
cool. The thermal sensor turns the pass transistor on
again after the IC’s junction temperature cools by 20°C,
resulting in a pulsed output during continuous thermal
overload conditions. Thermal overload protection is
designed to protect the MAX6469–MAX6484 in the
event of fault conditions. For continuous operation, do
not exceed the absolute maximum junction temperature
rating of TJMAX = +150°C.
Operating Region and Power Dissipation
The MAX6469–MAX6484’s maximum power dissipation
depends on the thermal resistance of the case and cir-
cuit 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 ther-
mal resistance through the PC board, copper traces,
and other materials to the surrounding air. The
MAX6469–MAX6476 QFN package ØJC = 41°C/W, and
the MAX6469–MAX6476 SOT package ØJC = 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
Output Voltage Selection
The MAX6469–MAX6484 feature dual-mode operation:
they operate in either a preset output voltage mode
or an adjustable mode. In preset voltage mode, internal
feedback resistors set the MAX6469–MAX6484’s output
from +1.5V to +3.3V (Table 1). Select this mode by con-
necting SET to ground (MAX6469–MAX6472/
MAX6477–MAX6480). In adjustable mode, select an
output between 1.25V and 5.5V using two external
resistors connected as a voltage-divider to SET (Figure
1). The output voltage is set by the following equation:
VOUT = VSET (1 + R1 / R2)
where VSET = 1.23V. To simplify resistor selection:
R1 = R2 (VOUT / VSET - 1)
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, con-
nect SET directly to ground.
Low-Noise UCSP Output
MAX6477–MAX6484 UCSP products include internal fil-
tering 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
VOUT = 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 <0.2Ω. To
reduce noise and improve load transient response, sta-
bility, and power-supply rejection, use large output
capacitor values such as 10µF.
Note that some ceramic capacitors exhibit large capac-
itance and ESR variation with temperature. With capaci-
tor dielectrics such as Z5U and Y5V, use 4.7µF or more
to ensure stability over temperature. With X7R or X5R
capacitor dielectrics, 3.3µF should be sufficient at all
operating temperatures. Higher ESR capacitors require
more capacitance to maintain stability. A graph of the
Region of Stable ESR vs. Load Current is shown in the
Typical Operating Characteristics.
To improve power-supply rejection and transient
response, use a 1µF capacitor between IN and GND.
The MAX6469–MAX6484 remain stable with purely
resistive loads or current loads up to 300mA.
Reset Transient Immunity
The reset circuit is relatively immune to short-duration,
falling VOUT transients. The Typical Operating
Characteristics section shows a graph of the Maximum
Transient Duration vs. Reset Threshold Overdrive for
which reset is not asserted. The graph was produced
using falling VOUT transients starting at VOUT and end-
ing below the reset threshold by the magnitude indicat-
ed (reset threshold overdrive). The graph shows the
maximum pulse width that a falling VOUT transient can
typically have without triggering a reset pulse. As the
amplitude of the transient increases (i.e., goes further
below the reset threshold), the maximum allowable
pulse width decreases. Typically, a VOUT transient that
goes only 10mV below the reset threshold and lasts for
75µs does not trigger a reset pulse.
______________________________________________________________________________________ 11
11 Page | ||
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| PDF Descargar | [ Datasheet MAX6475.PDF ] | |
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