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PDF US1075CP Data sheet ( Hoja de datos )
| Número de pieza | US1075CP | |
| Descripción | 7.5A LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR | |
| Fabricantes | UNISEM | |
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Hay una vista previa y un enlace de descarga de US1075CP (archivo pdf) en la parte inferior de esta página. Total 5 Páginas | ||
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FEATURES
1V Dropout at Full Load Current
Fast Transient Response
1% Voltage Reference Initial Accuracy
Output Current Limiting
Built-in Thermal Shutdown
APPLICATIONS
Low Voltage Processor Applications such as :
P54C™,P55C™,Cyrix M2™,
POWER PC™,AMD
GTL+ Termination
PENTIUM PRO™, KLAMATH™
Low Voltage Memory Termination Applications
Standard 3.3V Chip-Set and Logic Applications
US1075
7.5A LOW DROPOUT POSITIVE
ADJUSTABLE REGULATOR
DESCRIPTION
The US1075 product is a low dropout three terminal ad-
justable regulator with minimum of 7.5A output current
capability. This product is specifically designed to pro-
vide well regulated supply for low voltage IC applications
such as Pentium™ P54C™,P55C™ as well as GTL+
termination for Pentium Pro™ and Klamath™ pro-
cessor applications . The US1075 is also well suited for
other processors such as Cyrix™,AMD and Power
PC™applications. The US 1075 is guaranteed to have
<1.2V drop out at full load current making it ideal to
provide well regulated outputs such as 3.3V with input
supply voltage as low as 4.5V minimum.
TYPICAL APPLICATION
5V
C1
1500uF
Vin 3
1075app1-1.0
US1075 Vout 2
Adj 1
R1
121
R2
200
Typical Application of US1075 in a 5V to 3.3V regulator
3.3V
C2
2x 1500uF
Notes: Pentium P54C,P55C ,Klamath,Pentium Pro,VRE,are trade marks of Intel Corp.Cyrix M2 is trade mark of Cyrix Corp.
Power PC is trade mark of IBM Corp.
PACKAGE ORDER INFORMATION
Tj (°C)
0 TO 150
3 PIN PLASTIC
TO220 (T)
US1075CT
3 PIN PLASTIC
TO263 (M)
US1075CM
3 PIN PLASTIC
POWER FLEX (P)
US1075CP
Rev. 1.0
9/14/99
2-33
1 page  
US1075
Thermal Design
∆T=Temperature Rise Above Ambient
The US1075 incorporates an internal thermal shutdown
that protects the device when the junction temperature
exceeds the maximum allowable junction temperature.
Although this device can operate with junction tempera-
tures in the range of 150°C ,it is recommended that the
selected heat sink be chosen such that during maxi-
mum continuous load operation the junction tempera-
ture is kept below this number. The example below
shows the steps in selecting the proper Regulator heat
sink for the worst case current consumption using Intel
200MHz microprocessor as the load .
Assuming the following specifications :
θSA = ∆T
PD
θSA = 81 =11.7 ° C/W
6.9
5) Next , a heat sink with lower θsa than the one calcu-
lated in step 4 must be selected. One way to do this is
to simply look at the graphs of the “Heat Sink Temp
Rise Above the Ambient” vs. the “Power Dissipation” and
select a heat sink that results in lower temperature rise
than the one calculated in previous step. The following
heat sinks from AAVID and Thermaloy meet this crite-
ria.
VIN =5V
VO =3.5V
IOUTMAX =4.6A
TA =35° C
Thermalloy
AAVID
0
6021PB
534202B
Air Flow (LFM)
100 200
300
6021PB 6073PB 6109PB
534202B 507302 575002
400
7141D
576802B
The steps for selecting a proper heat sink to keep the
junction temperature below 135°C is given as :
1) Calculate the maximum power dissipation using :
( )PD = IO UT× VIN−VO UT
PD =4.6×(5−3.5) =6.9 W
2) Select a package from the Regulator data sheet
and record its junction to case (or Tab) thermal
resistance.
Selecting TO220 package gives us :
θJC =2.7° C/W
3) Assuming that the heat sink is Black Anodized, cal-
culate the maximum Heat sink temperature allowed :
Assume , θcs=0.05°C/W (Heat sink to Case thermal
resistance for Black Anodized)
( )TS=TJ−PD × θJC + θCS
TS =135−6.9×(2.7+0.05) =116 ° C
4) With the maximum heat sink temperature calcu-
lated in the previous step, the Heat Sink to Air thermal
resistance (θsa) is calculated by first calculating the
temperature rise above the ambient as follows :
∆T = TS − TA =116−35=81 ° C
Rev. 1.0
9/14/99
2-37
5 Page | ||
| Páginas | Total 5 Páginas | |
| PDF Descargar | [ Datasheet US1075CP.PDF ] | |
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