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PDF LP38513 Data sheet ( Hoja de datos )
| Número de pieza | LP38513 | |
| Descripción | 3A Fast Response Ultra Low Dropout Linear Regulator | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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July 2007
LP38513
3A Fast Response Ultra Low Dropout Linear Regulator
General Description
The LP38513 fast response ultra low dropout linear regulator
operates from a +2.25V to +5.50V input supply. This ultra low
dropout linear regulator responds very quickly to step
changes in line or load conditions, which makes it suitable for
low voltage microprocessor applications. Developed on a
CMOS process, with a PMOS pass transistor, the LP38513
has low quiescent current operation that is independent of the
output load current.
Ground Pin Current: Typically 12 mA at 3A load current.
Disable Mode: Typically 60 µA quiescent current when the
Enable pin is pulled low.
ERROR Flag: The ERROR Flag goes low if VOUT falls more
than typically 15% below the nominal value.
Precision Output Voltage: A guaranteed VOUT accuracy of
±2.6% with TJ from 0°C to 125°C.
Features
■ Conversions from 2.5V rail to 1.8V
■ Stable with ceramic capacitors
■ Low ground pin current
■ Load regulation of 0.1% for 10 mA to 3A load current
■ 60 μA typical quiescent current in shutdown mode
■ Guaranteed output current of 3A
■ Available in TO220-5 and TO263-5 packages
■ Guaranteed VOUT accuracy of ±2.6% with TJ from 0°C to
+125°C
■ ERROR flag indicates VOUT status
■ Over-Temperature and Over-Current protection
■ −40°C to +125°C operating TJ range
Applications
■ Microprocessor power supplies
■ GTL, GTL+, BTL, and SSTL bus terminators
■ Power supplies for DSPs
■ SCSI terminator
■ Post regulators
■ Battery chargers
■ Other battery powered applications
Typical Application Circuit
20146801
© 2007 National Semiconductor Corporation 201468
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1 page  
Typical Performance Characteristics Unless otherwise specified: TJ = 25°C, VIN = 2.5V, VEN = 2.0V,
CIN = 10 µF, COUT = 10 µF, IOUT = 10 mA.
VOUT vs Temperature
VOUT vs VIN
20146811
Ground Pin Current (IGND) vs VIN
20146837
Ground Pin Current (IGND) vs Temperature
20146812
Ground Pin Current(IGND) vs Temperature
20146813
Enable Threshold vs Temperature
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5
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5 Page 
FIGURE 2. ERROR Flag Operation, biased from VIN
20146834
POWER DISSIPATION/HEAT-SINKING
A heat-sink may be required depending on the maximum
power dissipation (PD(MAX)), maximum ambient temperature
(TA(MAX))of the application, and the thermal resistance (θJA) of
the package. Under all possible conditions, the junction tem-
perature (TJ) must be within the range specified in the Oper-
ating Ratings. The total power dissipation of the device is
given by:
PD = ( (VIN−VOUT) x IOUT) + ((VIN) x IGND)
(1)
where IGND is the operating ground current of the device
(specified under Electrical Characteristics).
The maximum allowable junction temperature rise (ΔTJ) de-
pends on the maximum expected ambient temperature (TA
(MAX)) of the application, and the maximum allowable junction
temperature (TJ(MAX)):
ΔTJ = TJ(MAX)− TA(MAX)
(2)
The maximum allowable value for junction to ambient Ther-
mal Resistance, θJA, can be calculated using the formula:
If a copper plane is to be used, the values of θJA will be the
same as shown in the next section for the TO263 package.
The heatsink to be used in the application should have a heat-
sink to ambient thermal resistance,
θHA ≤ θJA − θCH − θJC
(4)
In this equation, θCH is the thermal resistance from the case
to the surface of the heat sink and θJC is the thermal resis-
tance from the junction to the surface of the case. The rated
θJC is about 3°C/W for a TO220–5 package. The value for
θCH depends on method of attachment, insulator, etc. θCH
varies between 1.5°C/W to 2.5°C/W. If the exact value is un-
known, 2°C/W can be assumed.
HEAT-SINKING THE TO-263 PACKAGE
The TO-263 package uses the copper plane on the PCB as
a heat-sink. The tab of this package is soldered to the copper
plane for heat sinking. Figure 3 shows a curve for the θJA of
TO-263 package for different copper area sizes, using a typ-
ical PCB with 1 ounce copper and no solder mask over the
copper area for heat sinking.
θJA = ΔTJ / PD(MAX)
(3)
LP38513 is available in TO-220 and TO-263 packages. The
thermal resistance depends on amount of copper area or heat
sink, and on air flow. If the maximum allowable value of θJA
calculated above is ≥ 60 °C/W for TO-220 package and ≥ 60
°C/W for TO-263 package no heat-sink is needed since the
package can dissipate enough heat to satisfy these require-
ments. If the value for allowable θJA falls below these limits,
a heat sink is required.
HEAT-SINKING THE TO-220 PACKAGE
The thermal resistance of a TO-220 package can be reduced
by attaching it to a heat-sink or a copper plane on a PC board.
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| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet LP38513.PDF ] | |
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