Analogic AAT3258ITS-2.8-R-T1 300ma ldo linear regulator with up reset Datasheet

AAT3258
300mA LDO Linear Regulator with µP Reset
General Description
Features
The AAT3258 combines a high performance, low
noise, 300mA low dropout (LDO) linear regulator
with a microprocessor reset monitor. The 300mA
output capability of the LDO regulator makes this
device ideal for use with microprocessors and DSP
cores in portable products. The microprocessor
reset monitor section has very low quiescent current consumption and has an active low reset output. The AAT3258 has separate input pins for the
reset monitor and LDO regulator so they may be
operated from independent sources for increased
design flexibility. This device features very low quiescent current, typically less than 71µA.
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The LDO regulator has low dropout voltage, typically 400mV at the full output current level, making it
ideal for portable applications where extended battery life is critical. The AAT3258 LDO regulator section has complete over-current/short-circuit and
over-temperature protection circuits to guard against
extreme operating conditions. The device also has
an active output pull down function when disabled.
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The AAT3258 is available in a space-saving 8-pin
TSOPJW package. This device is capable of operation over a -40°C to +85°C temperature range.
PowerLinear™
Integrated LDO Regulator with µP Reset
300mA Output LDO Regulator
Low Dropout Regulator, 400mV at 300mA
High LDO Output Voltage Accuracy, Typically
1.5%
Very Low Noise and High Power Supply
Rejection Ratio (PSRR) LDO
Low Quiescent Current at 71µA
LDO Over-Current/Short-Circuit Protection
LDO Over-Temperature Protection
LDO Power Saving Shutdown Mode
Independent Device Power Inputs
High Accuracy Reset Monitor Threshold: ±1.5%
Active Low Push-Pull Monitor Reset Output
<2.0µA of Shutdown Current
Uses Low Equivalent Series Resistance
(ESR) Ceramic Capacitors
-40°C to +85°C Temperature Range
8-Pin TSOPJW Package
Applications
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Cellular Phones
Digital Cameras
Handheld Instrumentation
Microprocessor/DSP Core/IO Power
Notebook Computers
PDAs and Handheld Computers
Portable Communication Devices
Typical Application
100k
VIN
VDET
VIN
µP Reset
Manual Reset
1µF
LDO Shutdown
RESET
RESET OUT
VOUT
LDO VOUT
AAT3258
MR
GND
SHDN
BYP
2.2µF
10nF
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AAT3258
300mA LDO Linear Regulator with µP Reset
Pin Descriptions
Pin #
Symbol
Function
1
VIN
2
SHDN
LDO voltage regulator shutdown pin. This pin should not be left floating.
When connected low, all the internal circuitry is powered down. When high, it
is in normal operation.
3
VDET
Microprocessor reset input power supply pin. It may be connected to VIN.
4
MR
5
RESET
6
GND
Ground connection pin.
7
BYP
LDO voltage regulator bypass capacitor connection. To improve AC ripple
rejection and decrease LDO regulator self noise, connect a 10nF ceramic
capacitor between this pin and GND.
8
OUT
LDO voltage regulator output pin; should be decoupled with a 2.2µF or
greater value low ESR ceramic capacitor.
LDO voltage regulator input pin. This pin should be decoupled with 1µF or
greater capacitor. See application information.
Manual reset active low input. A logic low signal on MR asserts a reset condition. Asserted reset continues as long as MR is low and for a minimum of
150ms after MR returns high.
Reset output remains low while VDET is below the reset threshold and remains
so for a minimum of 150ms after VDET rises above the reset threshold.
Pin Configuration
TSOPJW-8
(Top View)
2
VIN
1
8
OUT
SHDN
2
7
BYP
VDET
3
6
GND
MR
4
5
RESET
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AAT3258
300mA LDO Linear Regulator with µP Reset
Absolute Maximum Ratings1
TA = 25°C, unless otherwise noted.
Symbol
VIN
VRESET
VSHDNIN(MAX)
IOUT
IRESET
∆VDET/∆t
TJ
Description
Input Voltage
RESET to GND
Maximum SHDN to Input Voltage
LDO Regulator DC Output Current
Maximum Reset Output Current
Maximum Rate of VDET Rise
Operating Junction Temperature Range
Value
Units
6.0
-0.3 to VDET+0.3
0.3
PD/(VIN-VO)
20
100
-40 to 150
V
V
V
mA
mA
V/µs
°C
Value
Units
150
833
°C/W
mW
Value
Units
(VOUT+VDO) to 5.5
1.0 to 5.5
-40 to +85
V
V
°C
Thermal Information2
Symbol
θJA
PD
Description
Maximum Thermal Resistance (TSOPJW-8)
Maximum Power Dissipation (TSOPJW-8)
Recommended Operating Conditions
Symbol
VIN
VDET
T
Description
3
Input Voltage to LDO
Input Voltage to µP Reset (0° to 70°C)
Ambient Temperature Range
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on a demo board.
3. To calculate minimum input voltage, use the following equation: VIN(MIN) = VOUT(MAX) + VDO(MAX) as long as VIN ≥ 2.5V.
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AAT3258
300mA LDO Linear Regulator with µP Reset
Electrical Characteristics1
TJ = 25°C, unless otherwise noted.
Symbol
Description
Conditions
Min
IOUT = 1mA TA = 25°C
to 300mA
TA = -40°C to 85°C
VOUT > 1.2V
VOUT < 0.4V
VIN = 5V, No Load, SHDN = VIN
VIN = 5V, SHDN = 0V
VIN = VOUT + 1 to 5.0V
IOUT = 300mA, TR/TR = 2µs,
VIN = VOUT + 1V to VOUT + 2V
IOUT = 1mA to 300mA, TR < 5µs
BYP = Open
IOUT = 300mA
-1.5
-2.5
300
Typ
Max
Units
1.5
2.5
%
300mA LDO Regulator
VOUT
IOUT
ISC
IGND
ISHDN
∆VOUT/VOUT*∆VIN
Output Voltage
Output Current
Short-Circuit Current
Ground Current
Shutdown Current
Line Regulation
∆VOUT (line)
Dynamic Line Regulation
VOUT (load)
TENDLY
VDO
VIL
VIH
IIL
IIH
Dynamic Load Regulation
Enable Delay Time
Dropout Voltage2
Input Low Voltage
Input High Voltage
Input Low Current
Input High Current
PSRR
TSD
THYS
eN
TC
Power Supply Rejection Ratio
Over-Temperature Shutdown
Threshold
Over-Temperature Shutdown
Hysteresis
Output Noise
Output Voltage Temperature
Coefficient
600
70
125
1.0
0.09
2.5
mV
60
15
400
mV
µs
mV
V
V
µA
µA
600
0.6
1.5
1.0
1.0
1kHz
IOUT = 10mA,
10kHz
CBYP = 10nF
1MHz
mA
mA
µA
µA
%/V
67
47
45
dB
145
°C
12
°C
50
µVRMS
22
ppm/°C
1. The AAT3258 is guaranteed to meet performance specifications over the -40°C to 85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2. VDO is defined as VIN - VOUT when VOUT is 98% of nominal.
4
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AAT3258
300mA LDO Linear Regulator with µP Reset
Electrical Characteristics1
TA = 25°C, unless otherwise noted.
Symbol
Description
Conditions
Min
TA = 0°C to +70°C
TA = -40°C to +85°C
VCC = 5.5V
VCC = 3.0V
VDET = 3.0V
VDET > VTH
AAT3258xxx-x.x-R
TA = 25°C
AAT3258xxx-x.x-Y
1
1.2
Typ
Max
Units
Microprocessor Reset Monitor
VDET
IQ
Input Voltage Range
Quiescent Current
IDD
IDOFF
Operating Supply Current
Reset Leakage Current
VTH
Reset Threshold Voltage
∆VTH/°C
TP
TRDY
TMR
MRGI
RMR
VIH
VIL
RESET Threshold Tempco
Reset Propagation Delay
Reset Active Timeout Period
MR Minimum Pulse Width
MR Glitch Immunity
MR Pull-Up Resistance
MR to Reset Propagation
Delay
MR Input Threshold (high)
MR Input Threshold (low)
VOL
Reset Low Voltage
TMD
VOH
Reset High Voltage
1.05
0.85
0.85
2.59
2.41
VDET = VTH to (VTH - 100mV)
150
10
30
2.63
2.45
40
15
250
100
65
5.5
5.5
3.0
2.0
2.0
1.0
2.67
2.49
400
90
0.5
VDET = VTH(MAX)
0.7 × VDET
VDET = VTH(MAX)
ISINK = 1.2mA, VDET = VTH(MIN),
VTH ≤ 3.08V, Reset Asserted
ISINK = 3.2mA, VDET = VTH(MIN),
VTH > 3.08V, Reset Asserted
ISOURCE = 800µA, VDET > 3.08V,
VDET - 1.5
VDET > VTH(MAX)
ISOURCE = 500µA, VDET >
0.8 * VDET
VTH(MAX), VTH ≤ 3.08V
V
µA
µA
µA
V
ppm/°C
µs
ms
µs
ns
kΩ
µs
0.25 × VDET
V
V
0.3
V
0.4
V
1. The AAT3258 is guaranteed to meet performance specifications over the -40°C to 85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
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AAT3258
300mA LDO Linear Regulator with µP Reset
Typical Characteristics
Unless otherwise noted, VIN = 5V, TA = 25°C.
Dropout Voltage vs. Temperature
Dropout Characteristics
3.20
IL = 300mA
480
Output Voltage (V)
Dropout Voltage (mV)
540
420
360
300
IL = 100mA
IL = 150mA
240
180
120
IOUT = 0mA
3.00
2.80
IOUT = 300mA
IOUT = 150mA
2.60
2.40
2.20
60
IOUT = 10mA
IL = 50mA
0
-40 -30 -20 -10 0
2.00
2.70
10 20 30 40 50 60 70 80 90 100 110 120
2.80
IOUT = 100mA
IOUT = 50mA
2.90
Temperature (°C)
3.00
3.10
3.20
3.30
Input Voltage (V)
Ground Current vs. Input Voltage
Dropout Voltage vs. Output Current
90.00
500
80.00
Ground Current (µA)
Dropout Voltage (mV)
450
400
350
300
85°C
250
200
25°C
150
-40°C
100
50
IOUT = 300mA
50.00
IOUT = 150mA
IOUT = 50mA
40.00
IOUT = 0mA
30.00
IOUT = 10mA
20.00
0.00
0
50
100
150
200
250
2
300
2.5
3
3.5
4
4.5
Output Current (mA)
Input Voltage (V)
Quiescent Current vs. Temperature
Output Voltage vs. Temperature
5
1.203
100
90
1.202
80
Output Voltage (V)
Quiescent Current (µA)
60.00
10.00
0
70
60
50
40
30
20
10
0
-40 -30 -20 -10
0
10 20 30 40 50 60 70 80 90 100 110 120
Temperature (°C)
6
70.00
1.201
1.200
1.199
1.198
1.197
1.196
-40 -30 -20 -10
0
10 20
30
40
50 60
70 80
90 100
Temperature (°C)
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AAT3258
300mA LDO Linear Regulator with µP Reset
Typical Characteristics
Unless otherwise noted, VIN = 5V, TA = 25°C.
Initial Power-Up Response Time
Turn-Off Response Time
(CBYP = 10nF)
(CBYP = 10nF)
VSHDN (5V/div)
VSHDN (5V/div)
VOUT (1V/div)
VOUT (1V/div)
50µs/div
400µs/div
Line Transient Response
Turn-On Time From Enable (VIN present)
(CBYP = 10nF)
6
3.04
VSHDN (5V/div)
Input Voltage (V)
3.03
VIN
4
3.02
3
3.01
2
3.00
VOUT
1
2.99
VIN = 4V
VOUT = 1V/div
0
2.98
5µs/div
100µs/div
Load Transient Response 300mA
Load Transient Response
Output Voltage (V)
2.75
200
2.70
100
2.65
0
IOUT
2.60
-100
3.00
800
2.90
700
2.80
600
VOUT
2.70
500
2.60
400
2.50
300
2.40
200
2.30
100
IOUT
2.20
0
2.10
100µs/div
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Output Current (mA)
300
2.80
Output Current (mA)
400
VOUT
Output Voltage (V)
500
2.90
2.85
Output Voltage (V)
5
-100
10µs/div
7
AAT3258
300mA LDO Linear Regulator with µP Reset
Typical Characteristics
Unless otherwise noted, VIN = 5V, TA = 25°C.
Over-Current Protection
AAT3258 Self Noise
1200
Output Current (mA)
Noise Amplitude (µV/rtHz)
(COUT = 10µF, ceramic)
10
1
0.1
Band Power:
300Hz to 50kHz = 44.6µVrms/rtHz
100Hz to 100kHz = 56.3µVrms/rtHz
0.01
0.001
0.01
1000
800
600
400
200
0
-200
0.1
1
10
100
1000
Time (20ms/div)
10000
Frequency (kHz)
Normalized Reset Threshold
vs. Temperature
LDO SHDN VIH and V IL vs. VIN
1.250
VIH
1.175
1.150
1.125
VIL
1.100
1.075
1.050
2.5
3.0
3.5
1.003
Normalized Threshold
1.225
1.200
4.0
4.5
5.0
1.002
1.001
1.000
0.999
0.998
0.997
-40
5.5
-20
0
Power-Up Reset
Timeout (ms)
300
280
260
240
220
200
180
160
20
40
60
Temperature (°C)
8
80
100
Reset Propagation Delay (µs)
320
0
60
80
Power-Down Reset Propagation
Delay vs. Temperature
Power-Up Reset Timeout
vs. Temperature
-20
40
Temperature (°C)
Input Voltage (V)
-40
20
30
25
VDO = 10mV
20
15
10
VDO = 100mV
5
0
-40
-20
0
20
40
60
80
Temperature (°C)
3258.2005.04.1.5
AAT3258
300mA LDO Linear Regulator with µP Reset
Typical Characteristics
Unless otherwise noted, VIN = 5V, TA = 25°C.
Maximum Transient Duration
vs. Reset Threshold Overdrive
Maximum Transient
Duration (µS)
400
350
300
250
200
150
100
50
0
1
10
100
1000
Reset Threshold Overdrive,
VTH-VCC (mV)
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AAT3258
300mA LDO Linear Regulator with µP Reset
Functional Block Diagram
OUT
VIN
Over-Current
Protection
OverTemperature
Protection
+
Error
Amplifier
-
Voltage
Reference
BYP
SHDN
VDET
MR
+
Reset Generator
and Timer
RESET
-
Voltage
Reference
Oscillator
GND
Functional Description
The AAT3258 is intended for LDO regulator applications where output current load requirements range
from no load to 300mA.
The advanced circuit design of the AAT3258 has
been specifically optimized for very fast start-up and
shutdown timing. This proprietary CMOS LDO has
also been tailored for superior transient response
characteristics. These traits are particularly important for applications that require fast power supply
timing, such as GSM cellular telephone handsets.
The high-speed turn-on capability is enabled
through the implementation of a fast start control circuit, which accelerates the power-up behavior of
fundamental control and feedback circuits within the
LDO regulator.
Fast turn-off response time is achieved by an active
output pull-down circuit, which is enabled when the
LDO regulator is placed in the shutdown mode. This
active fast shutdown circuit has no adverse effect on
normal device operation.
The AAT3258 has very fast transient response characteristics, which is an important feature for applications where fast line and load transient response is
10
required. This rapid transient response behavior is
accomplished through the implementation of an
active error amplifier feedback control. This proprietary circuit design is unique to this MicroPower
LDO regulator.
The LDO regulator output has been specifically optimized to function with low-cost, low-ESR ceramic
capacitors; however, the design will allow for operation over a wide range of capacitor types.
A bypass pin has been provided to allow the addition
of an optional voltage reference bypass capacitor to
reduce output self noise and increase power supply
ripple rejection. Device self noise and PSRR will be
improved by the addition of a small ceramic capacitor in this pin. However, increased values of CBYPASS
may slow down the LDO regulator turn-on time.
This LDO regulator has complete short-circuit and
thermal protection. The integral combination of
these two internal protection circuits gives the
AAT3258 a comprehensive safety system to guard
against extreme adverse operating conditions.
Device power dissipation is limited to the package
type and thermal dissipation properties. Refer to the
Thermal Considerations section of this datasheet for
details on device operation at maximum output current loads.
3258.2005.04.1.5
AAT3258
300mA LDO Linear Regulator with µP Reset
The microprocessor reset section monitors the supply
voltage to a microprocessor and asserts a reset signal whenever the VDET voltage falls below a factoryprogrammed threshold. This threshold is accurate
within +/-1.5% at 25°C. The reset signal remains
VTH
asserted for a minimum of 150ms after VDET has risen
above the threshold, as shown in Figure 1.
To assure the maximum possible performance is
obtained from the AAT3258, please refer to the following application recommendations.
VTH
VTH
VDET
RESET
tRDY
tRDY
Figure 1: Reset Signal Assertion.
LDO Regulator Applications
Input Capacitor
Typically, a 1µF or larger capacitor is recommended for CIN in most applications. A CIN capacitor is
not required for basic LDO regulator operation.
However, if the AAT3258 is physically located more
than three centimeters from an input power source,
a CIN capacitor will be needed for stable operation.
CIN should be located as closely to the device VIN
pin as practically possible. CIN values greater than
1µF will offer superior input line transient response
and will assist in maximizing the highest possible
power supply ripple rejection.
Ceramic, tantalum, or aluminum electrolytic capacitors may be selected for CIN. There is no specific
capacitor ESR requirement for CIN. However, for
300mA LDO regulator output operation, ceramic
capacitors are recommended for CIN due to their
inherent capability over tantalum capacitors to withstand input current surges from low impedance
sources such as batteries in portable devices.
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Output Capacitor
For proper load voltage regulation and operational
stability, a capacitor is required between pins VOUT
and GND. The COUT capacitor connection to
the LDO regulator ground pin should be made as
direct as practically possible for maximum device
performance.
The AAT3258 has been specifically designed to function with very low ESR ceramic capacitors. For best
performance, ceramic capacitors are recommended.
Typical output capacitor values for maximum output
current conditions range from 1µF to 10µF.
Applications utilizing the exceptionally low output
noise and optimum power supply ripple rejection
characteristics of the AAT3258 should use 2.2µF or
greater for COUT. If desired, COUT may be increased
without limit.
In low output current applications where output
load is less than 10mA, the minimum value for
COUT can be as low as 0.47µF.
11
AAT3258
300mA LDO Linear Regulator with µP Reset
Bypass Capacitor and Low Noise
Applications
A bypass capacitor pin is provided to enhance the
low noise characteristics of the AAT3258 LDO regulator. The bypass capacitor is not necessary for
operation. However, for best device performance, a
small ceramic capacitor should be placed between
the bypass pin (BYP) and the device ground pin
(GND). The value of CBYP may range from 470pF
to 10nF. For lowest noise and best possible power
supply ripple rejection performance, a 10nF capacitor should be used. To practically realize the highest power supply ripple rejection and lowest output
noise performance, it is critical that the capacitor
connection between the BYP pin and GND pin be
direct and PCB traces should be as short as possible. Refer to the Evaluation Board Layout section
of this document for examples.
There is a relationship between the bypass capacitor value and the LDO regulator turn-on and turnoff time. In applications where fast device turn-on
and turn-off time are desired, the value of CBYP
should be reduced.
In applications where low noise performance and/
or ripple rejection are less of a concern, the bypass
capacitor may be omitted. The fastest device turnon time will be realized when no bypass capacitor
is used.
DC leakage on this pin can affect the LDO regulator output noise and voltage regulation performance. For this reason, the use of a low leakage,
high quality, ceramic (NPO or C0G type) or film
capacitor is highly recommended.
Capacitor Characteristics
Ceramic composition capacitors are highly recommended over all other types of capacitors.
Ceramic capacitors offer many advantages over
their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low
ESR, is lower cost, has a smaller PCB footprint,
and is non-polarized. Line and load transient
response of the LDO regulator is improved by
using low ESR ceramic capacitors. Since ceramic
capacitors are non-polarized, they are not prone to
incorrect connection damage.
12
Equivalent Series Resistance: ESR is a very
important characteristic to consider when selecting a
capacitor. ESR is the internal series resistance
associated with a capacitor that includes lead resistance, internal connections, size and area, material
composition, and ambient temperature. Typically,
capacitor ESR is measured in milliohms for ceramic
capacitors and can range to more than several ohms
for tantalum or aluminum electrolytic capacitors.
Ceramic Capacitor Materials: Ceramic capacitors
less than 0.1µF are typically made from NPO or
C0G materials. NPO and C0G materials are typically tight tolerance and are very stable over temperature. Larger capacitor values are typically composed of X7R, X5R, Z5U, and Y5V dielectric materials. Large ceramic capacitors, typically greater
than 2.2µF, are often available in the low-cost Y5V
and Z5U dielectrics. These two material types are
not recommended for use with LDO regulators
since the capacitor tolerance can vary more than
±50% over the operating temperature range of the
device. A 2.2µF Y5V capacitor could be reduced to
1µF over temperature; this could cause problems
for circuit operation. X7R and X5R dielectrics are
much more desirable. The temperature tolerance
of X7R dielectric is better than ±15%.
Capacitor area is another contributor to ESR.
Capacitors that are physically large in size will have
a lower ESR when compared to a smaller sized
capacitor of an equivalent material and capacitance value. These larger devices can improve circuit transient response when compared to an equal
value capacitor in a smaller package size.
Consult capacitor vendor data sheets carefully
when selecting capacitors for LDO regulators.
Shutdown Function
The shutdown pin is designed to turn off the LDO
regulator when the device is not in use. This pin is
active high and is compatible with CMOS logic. To
assure the LDO regulator will switch on, the SHDN
turn-on control level must be greater than 1.5 volts.
The LDO regulator will go into the disable shutdown mode when the voltage falls below 0.6 volts.
If the shutdown function is not needed in a specific
application, it may be tied to VIN to keep the LDO
regulator in a continuously on state.
3258.2005.04.1.5
AAT3258
300mA LDO Linear Regulator with µP Reset
When the LDO regulator is in the shutdown mode,
an internal 1.5kΩ resistor is connected between
VOUT and GND. This is intended to discharge COUT
when the LDO regulator is disabled. The internal
1.5kΩ has no adverse effect on device turn-on time.
Short-Circuit Protection
The LDO regulator section contains an internal
short-circuit protection circuit that will trigger when
the output load current exceeds the internal
threshold limit. Under short-circuit conditions, the
output of the LDO regulator will be current limited
until the short-circuit condition is removed from the
output or the LDO regulator package power dissipation exceeds the device thermal limit.
avoided since this would forward bias the internal
parasitic diode and allow excessive current flow into
the VOUT pin, possibly damaging the LDO regulator.
In applications where there is a possibility of VOUT
exceeding VIN for brief amounts of time during normal operation, the use of a larger value CIN capacitor is highly recommended. A larger value of CIN
with respect to COUT will effect a slower CIN decay
rate during shutdown, thus preventing VOUT from
exceeding VIN. In applications where there is a
greater danger of VOUT exceeding VIN for extended
periods of time, it is recommended to place a
Schottky diode across VIN to VOUT (connecting the
cathode to VIN and anode to VOUT). The Schottky
diode forward voltage should be less than 0.45 volts.
Thermal Protection
The AAT3258 has an internal thermal protection circuit which will turn on when the device die temperature exceeds 145°C. The internal thermal protection circuit will actively turn off the LDO regulator
output pass device to prevent the possibility of overtemperature damage. The LDO regulator output
will remain in a shutdown state until the internal die
temperature falls back below the 145°C trip point.
The combination and interaction between the shortcircuit and thermal protection systems allows the
LDO regulator to withstand indefinite short-circuit
conditions without sustaining permanent damage.
No-Load Stability
The LDO regulator is designed to maintain output
voltage regulation and stability under operational
no-load conditions. This is an important characteristic for applications where the output current may
drop to zero.
Reverse Output-to-Input Voltage
Conditions and Protection
Under normal operating conditions, a parasitic diode
exists between the output and input of the LDO regulator. The input voltage should always remain
greater than the output load voltage, maintaining a
reverse bias on the internal parasitic diode.
Conditions where VOUT might exceed VIN should be
3258.2005.04.1.5
MicroPower Supervisory Circuit
Applications
Reset Output Options
The reset pin is an active low push-pull output. In
the event of a power down or brown-out condition,
the reset signal remains valid until the VDET drops
below 1.2V.
Manual Reset Input
A logic low signal on MR asserts a reset condition.
Reset continues to be asserted as long as MR is low
and for a minimum of 150ms after MR returns high.
This input is internally pulled up to VCC via a 20kΩ
resistor, so leaving the pin unconnected is acceptable if a manual reset function is not needed. The
MR input is internally debounced, which allows use
of a mechanical switch. It should be a normallyopen momentary switch connected from MR to
GND. Additionally, the MR pin can be driven from
TTL, CMOS, or open drain logic outputs.
Supply Voltage Transient Behavior
In some cases, fast negative transients of short
duration can appear on the VCC power supply. The
AAT3258 series device provides some immunity to
line transients which can generate invalid reset
13
AAT3258
300mA LDO Linear Regulator with µP Reset
pulses. Figure 2 shows typical behavior of short
duration pulses versus RESET comparator overdrive. As shown in the Maximum Transient
Duration vs. Reset Threshold Overdrive graph,
when the transient voltage becomes larger, the
time allowed before asserting a reset becomes
shorter (e.g., typically a transient of 100mV below
the reset threshold would have to be present for
more than 50µs to cause a reset). Immunity can be
increased by the addition of a small bypass capacitor of 0.1µF connected as closely to the VCC pin as
possible.
VCC
VCC
VDET
0.1µF
RESET
MR
GND
RESET
uP
INPUT
GND
Figure 2: Typical Behavior of Short Duration Pulses vs. RESET Comparator Overdrive.
14
3258.2005.04.1.5
AAT3258
300mA LDO Linear Regulator with µP Reset
Evaluation Board Layout
The AAT3258 evaluation layout (Figures 3, 4, and
5) follows the recommend printed circuit board lay-
Figure 3: Evaluation Board
Component Side Layout.
out procedures and can be used as an example for
good application layouts.
Note: Board layout shown is not to scale.
Figure 4: Evaluation Board
Solder Side Layout.
Figure 5: Evaluation Board Top Side
Silk Screen Layout / Assembly Drawing.
3258.2005.04.1.5
15
AAT3258
300mA LDO Linear Regulator with µP Reset
Ordering Information
Package
Reset Threshold Voltage1
LDO Regulator
Marking2
Part Number (Tape and Reel)3
TSOPJW-8
2.63V
2.80V
IIXYY
AAT3258ITS-2.8-R-T1
TSOPJW-8
2.45V
2.80V
IHXYY
AAT3258ITS-2.8-Y-T1
TSOPJW-8
2.63V
3.0V
MEXYY
AAT3258ITS-3.0-R-T1
TSOPJW-8
2.63V
3.3V
MXXYY
AAT3258ITS-3.3-R-T1
Package Information
TSOPJW-8
2.40 ± 0.10
2.85 ± 0.20
0.325 ± 0.075
0.65 BSC 0.65 BSC 0.65 BSC
7°
0.055 ± 0.045
0.04 REF
0.15 ± 0.05
1.0175 ± 0.0925
0.9625 ± 0.0375
3.025 ± 0.075
0.010
0.45 ± 0.15
2.75 ± 0.25
All dimensions in millimeters.
1. Consult the factory for any additional reset or low dropout voltages.
2. XYY = assembly and date code.
3. Sample stock is generally held on part numbers listed in BOLD.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work
rights, or other intellectual property rights are implied.
AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice, and advise customers to obtain the latest
version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale
supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability.
AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech’s standard warranty. Testing and
other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily
performed.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
16
3258.2005.04.1.5
Form#: FOR001 Rev. D
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