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PDF LM1085 Data sheet ( Hoja de datos )
| Número de pieza | LM1085 | |
| Descripción | 3A Low Dropout Positive Voltage Regulator | |
| Fabricantes | CYStech Electronics | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LM1085 (archivo pdf) en la parte inferior de esta página. Total 9 Páginas | ||
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Spec. No. : C540J3
CYStech Electronics Corp. Issued Date : 2003.06.25
Revised Date :2013.09.11
Page No. : 1/9
3A Low Dropout Positive Voltage Regulator
LM1085-XXXJ3
TO-252AB
TO-252AA
Features
Dropout Voltage 1.4V at 3A Output Current.
Fast Transient Response.
Extremely Tight Line and Load Regulation.
Built-in Thermal Shutdown Protection.
Adjustable Output Voltage or Fixed 1.5V, 1.8V, 2.5V, 3.3V, 5.0V.
Output Current Limiting.
Adj/G O I
Adj/G O I
Description
The LM1085-XXXJ3 is a low dropout three terminal regulator with 3A output current capability. The output voltage is
adjustable with the use of a resistor divider or fixed 1.5V, 1.8V, 2.5V, 3.3V and 5.0V. Dropout voltage is guaranteed to be at
maximum of 1.4V with the maximum output current. Its low dropout voltage and fast transient response make it ideal for
low voltage microprocessor applications. Current limit and thermal protection provide protection against any overload
condition that would create excessive junction temperatures.
Applications
Mother Board I/O Power Supplies.
Microprocessor Power Supplies.
High Current Regulator.
Post Regulator for Switching Supply.
Ordering Information
Device
LM1085-XXXJ3-0-T3-G
Package
TO-252
(Pb-free lead plating and halogen-free package)
Shipping
2500 pcs / tape & reel
Environment friendly grade : S for RoHS compliant products, G for RoHS compliant and
green compound products
Packing spec, T3 : 2500 pcs / tape & reel, 13” reel
Product rank, zero for no rank products
Product name
LM1085-XXXJ3
CYStek Product Specification
1 page  
Spec. No. : C540J3
CYStech Electronics Corp. Issued Date : 2003.06.25
Revised Date :2013.09.11
Page No. : 5/9
Stability
The LM1085 requires the use of an output capacitor as part of the frequency compensation in order to make the
regulator stable. For most applications, the addition of 150μF aluminum electrolytic capacitor or a 22μF solid
tantalum on the output will ensure stability for all operating conditions.
When the adjustment terminal is bypassed with a capacitor to improve the ripple rejection, the requirement for an
output capacitor increases. The value of 22μF tantalum or 150μF aluminum covers all cases of bypassing the
adjustment terminal. Without bypassing the adjustment terminal smaller capacitors can be used with equally good
results. To ensure good transient response with heavy load current changes capacitor values on the order of 100μF
are used in the output of many regulators. To further improve stability and transient response of these devices larger
values of output capacitor can be used.
Protection Diodes
Unlike older regulators, the LM1085 family does not need any protection diodes between the adjustment pin and the
output and from the output to the input to prevent over-stressing the die.
Internal resistors are limiting the internal current paths on the adjustment pin, therefore even with capacitors on the
adjustment pin, no protection diode is needed to ensure device safety under short-circuit conditions.
If high value output capacitors are used, such as 1000μF to 5000μF, and the input pin is instantaneously shorted to
ground, damage can occur. A diode from output to input is recommended, when a crowbar circuit at the input of the
LM1085 is used. Normal power supply cycling or even plugging and unplugging in the system will not generate
current large enough to do any damage.
Thermal Design
The LM1085 incorporates an internal power and thermal limiting circuitry designed to protect the device under
overload conditions. However maximum junction temperature ratings should not be exceeded under continuous
normal load conditions.
Careful consideration must be given to all sources of thermal resistance from junction to ambient, including junction-
to-case, case to heat sink interface and heat sink resistance itself. To ensure safe operating temperatures and reflect
more accurately the device temperature, new thermal resistance specifications have been developed.
Junction-to-case thermal resistance is specified from the IC junction to the bottom of the case directly below the die.
This is the lowest resistance path for the heat flow. In order to ensure the best possible thermal flow from this area
of the package to the heat sink, proper mounting is required. Thermal compound at the case-to-heat sink interface is
recommended. A thermally conductive spacer can be used, if the case of the device must be electrically isolated, but
its added contribution to thermal resistance has to be considered.
Layout Consideration
The output capacitors must be located as close to the Vout terminal of the device as possible. It is recommended to
use a section of a layer of the PC board as a plane to connect the Vout pin to the output capacitors to prevent any high
frequency oscillation that may result due to excess trace inductance.
LM1085-XXXJ3
CYStek Product Specification
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet LM1085.PDF ] | |
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