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PDF LT1585 Data sheet ( Hoja de datos )
| Número de pieza | LT1585 | |
| Descripción | 7A/ 4.6A/ 3A Low Dropout Fast Response Positive Regulators Adjustable and Fixed | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LT1585 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
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LT1584/LT1585/LT1587
7A, 4.6A, 3A Low Dropout
Fast Response
Positive Regulators
Adjustable and Fixed
FEATURES
s Fast Transient Response
s Guaranteed Dropout Voltage at Multiple Currents
s Load Regulation: 0.05% Typical
s Trimmed Current Limit
s On-Chip Thermal Limiting
s Standard 3-Pin Power Package
U
APPLICATIO S
s PentiumTM Processor Supplies
s PowerPCTM Supplies
s Other 2.5V to 3.6V Microprocessor Supplies
s Low Voltage Logic Supplies
s Battery-Powered Circuitry
s Post Regulator for Switching Supply
LT1585/7CM, LT1584/5/7CT
LT1585/7CM-3.3, LT1584/5/7CT-3.3
LT1585CM-3.38, LT1584/5CT-3.38
LT1585/7CM-3.45, LT1584/5/7CT-3.45
LT1585/7CM-3.6, LT1584/5/7CT-3.6
Adjustable
3.3V Fixed
3.38V Fixed
3.45V Fixed
3.6V Fixed
DESCRIPTIO
The LT®1584/LT1585/LT1587 are low dropout three-
terminal regulators with 7A, 4.6A and 3A output current
capability, respectively. Design has been optimized for low
voltage applications where transient response and mini-
mum input voltage are critical. Similar to the LT1083/4/5
family, it has lower dropout voltage and faster transient
response. These improvements make it ideal for low volt-
age microprocessor applications requiring a regulated
2.5V to 3.6V output with an input supply below 7V.
Current limit is trimmed to ensure specified output current
and controlled short-circuit current. On-chip thermal lim-
iting provides protection against any combination of over-
load that would create excessive junction temperatures.
The LT1585/LT1587 are available in both the through-hole
and surface mount versions of the industry standard 3-pin
TO-220 power package. The LT1584 is available in the
through-hole 3-pin TO-220 power package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a trademark of Intel Corporation. PowerPC is a trademark of IBM Corporation.
TYPICAL APPLICATIO
3.3V, 7A, 4.6A, 3A Regulator
VIN ≥ 4.75V
+ C1
10µF
LT1584-3.3
LT1585-3.3
LT1587-3.3
3.3V
7A, 4.6A, 3A
+ C2*
SOLID
TANTALUM
* REQUIRED FOR STABILITY
LT1584: C2 = 22µF,
LT1585/LT1587: C2 = 10µF
1585 TA01
NOTE: MICROPROCESSOR APPLICATIONS WITH LOAD TRANSIENTS OF 3.8A REQUIRE
OUTPUT DECOUPLING CAPACITANCE > 1300µF ON FIXED VOLTAGE PARTS TO ACHIEVE
< 50mV OF DEVIATION FROM NOMINAL OUTPUT. CONSULT FACTORY FOR DETAILS
Dropout Voltage vs Output Current
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0
OUTPUT CURRENT (A)
IFULL LOAD
1585 TA02
158457a
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1 page  
LT1584/LT1585/LT1587
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
CONDITIONS
MIN TYP MAX
Thermal Regulation
Temperature Stability
LT1584/5/7
TA = 25°C, 30ms pulse
LT1584/5/7-3.3 TA = 25°C, 30ms pulse
LT1584/5-3.38 TA = 25°C, 30ms pulse
LT1584/5/7-3.45 TA = 25°C, 30ms pulse
LT1584/5/7-3.6 TA = 25°C, 30ms pulse
0.004 0.02
q 0.5
Long-Term Stability
RMS Output Noise
(% of VOUT)
Thermal Resistance
Junction to Case
LT1584
LT1585
LT1585
LT1587
LT1587
TA = 125°C, 1000 Hrs.
TA = 25°C, 10Hz ≤ f ≤ 10kHz
T Package: Control Circuitry/Power Transistor
T Package: Control Circuitry/Power Transistor
M Package: Control Circuitry/Power Transistor
T Package: Control Circuitry/Power Transistor
M Package: Control Circuitry/Power Transistor
0.03
0.003
1.0
0.65/2.7
0.7/3.0
0.7/3.0
0.7/3.0
0.7/3.0
UNITS
%/W
%
%
%
°C/W
°C/W
°C/W
°C/W
°C/W
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: See thermal regulation specifications for changes in output voltage
due to heating effects. Load and line regulation are measured at a constant
junction temperature by low duty cycle pulse testing.
Note 3: Line and load regulation are guaranteed up to the maximum power
dissipation (25W for the LT1584 in T package, 26.5W for the LT1585 in T
package, 18W for the LT1587 in T package). Power dissipation is
determined by input/output differential and the output current. Guaranteed
maximum output power will not be available over the full input/output
voltage range.
Note 4: IFULL LOAD is defined as the maximum value of output load current
as a function of input-to-output voltage. IFULL LOAD is equal to 7A for the
LT1584, 4.6A at TJ ≥ 25°C and 4A at TJ < 25°C for the LT1585/LT1585-3.3
and 3A for the LT1587. The remaining LT1585 fixed voltage versions are
4A. The LT1585 and LT1587 have constant current limit with changes in
input-to-output voltage. The LT1584 has variable current limit which
decreases about 4A as input-to-output voltage increases from 3V to 7V.
158457a
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5 Page 
LT1584/LT1585/LT1587
APPLICATIONS INFORMATION
Overload Recovery
The LT1584 devices have safe-area protection similar to
the LT1083/LT1084/LT1085. The safe-area protection de-
creases current limit as input-to-output voltage increases.
This behavior keeps the power transistor inside a safe
operating region for all values of input-to-output voltage.
The LT1584 protection circuitry provides some output
current at all values of input-to-output voltage up to the 7V
maximum supply voltage. When power is first applied, the
input voltage rises and the output voltage follows the input.
The input-to-output voltage remains small and the regula-
tor can supply large output currents. This action permits
the regulator to start-up into very heavy loads.
With higher input voltages, a problem can occur where the
removal of an output short does not permit the output
voltage to recover. This problem is not unique to the
LT1584 devices and is present on the LT1083/LT1084/
LT1085 family and older generation linear regulators. The
problem occurs with a heavy output load, a high input
voltage, and a low output voltage. An example is immedi-
ately after the removal of a short circuit. The load line of
such a load may intersect the output current curve at two
points. If this happens, two stable output operating points
exist for the regulator. With this double intersection, the
power supply may require cycling down to zero and back up
again to make the output recover. This situation does not
occur with the LT1585/LT1587 because no foldback cir-
cuitry is required to provide safe-area protection.
Ripple Rejection
The typical curve for ripple rejection reflects values for the
LT1584/LT1585/LT1587 fixed output voltage parts be-
tween 3.3V and 3.6V. In applications that require improved
ripple rejection, use the adjustable devices. A bypass
capacitor from the adjust pin to ground reduces the output
ripple by the ratio of VOUT/1.25V. The impedance of the
adjust pin capacitor at the ripple frequency should be less
than the value of R1 (typically in the range of 100Ω to
120Ω) in the feedback divider network in Figure 2. There-
fore, the value of the required adjust pin capacitor is a
function of the input ripple frequency. For example, if R1
equals 100Ω and the ripple frequency equals 120Hz, the
adjust pin capacitor should be 22µF. At 10kHz, only 0.22µF
is needed.
Output Voltage
The LT1584/LT1585/LT1587 adjustable regulators develop
a 1.25V reference voltage between the output pin and the
adjust pin (see Figure 3). Placing a resistor R1 between
these two terminals causes a constant current to flow
through R1 and down through R2 to set the overall output
voltage. Normally, this current is the specified minimum
load current of 10mA. The current out of the adjust pin adds
to the current from R1 and is typically 55µA. Its output
voltage contribution is small and only needs consideration
when very precise output voltage setting is required.
LT1584
VIN
+
C1
10µF
IN
OUT
ADJ
VREF
R1
+
VOUT
C2
22µF
IADJ
55µA
VOUT = VREF (1 + R2/R1) + IADJ (R2)
R2
LT1585 • F03
Figure 3. Basic Adjustable Regulator
Load Regulation
It is not possible to provide true remote load sensing
because the LT1584/LT1585/LT1587 are three-terminal
devices. Load regulation is limited by the resistance of the
wire connecting the regulators to the load. Load regulation
per the data sheet specification is measured at the bottom
of the package.
For fixed voltage devices, negative side sensing is a true
Kelvin connection with the ground pin of the device re-
turned to the negative side of the load. This is illustrated in
Figure 4.
RP
PARASITIC
LT1584-3.3
LINE RESISTANCE
VIN IN
OUT
GND
RL
LT1585 • F04
Figure 4. Connection for Best Load Regulation
158457a
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LT1585.PDF ] | |
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