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US1260CT の電気的特性と機能

US1260CTのメーカーはUNISEMです、この部品の機能は「DUAL 6A AND 1A LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR」です。


製品の詳細 ( Datasheet PDF )

部品番号 US1260CT
部品説明 DUAL 6A AND 1A LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR
メーカ UNISEM
ロゴ UNISEM ロゴ 




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US1260CT Datasheet, US1260CT PDF,ピン配置, 機能
US1260
DUAL 6A AND 1A LOW DROPOUT
POSITIVE ADJUSTABLE REGULATOR
FEATURES
Guaranteed <1.3V Dropout at 6A (output #2)
Guaranteed <0.6V Dropout at 1A (output #1)
Fast Transient Response
1% Voltage Reference Initial Accuracy
Built in Thermal Shutdown
APPLICATIONS
Providing a single package solution for GTL+
and High Speed Bus Termination
Dual supply P55Capplications
DESCRIPTION
The US1260 product using a proprietary process com-
bines a dual low drop out adjustable output regulators in
a single package with one output having a minimum of
6A and the other one having a 1A output current capabil-
ity. This product is specifically designed to provide well
regulated supplies for low voltage ICs such as 3.3V to
1.5V and 2.5V supplies for the GTL+ termination
and the new clock for Pentium II applications.Other
applications include low cost dual supply for proces-
sors such as Intel P55Cwhere 2.8V and 3.3 V are
needed for the Core and the I/O supplies from the
5V input.
TYPICAL APPLICATION
1260app7-1.0
3.3V
C1
U1
US1260
Vout1 7
Vin 6
Vout2 5
Gnd 4
Vfb2 3
Vfb1 2
Vctrl 1
5V
C4
R5
C5
R1
R2
R3
R4
2.5V / 1A
C2
1.5V / 6A
C3
Typical application of US1260 in the Pentium ΙΙ™ design with the 1.5V output providing for GTL+ termination
while 2.5V supplies the clock chip.
Notes: Pentium ΙΙ is trade mark of Intel Corp.
Notes: P55C is trade mark of Intel Corp.
PACKAGE ORDER INFORMATION
Tj (°C)
0 TO 150
7 PIN PLASTIC
TO220(T)
US1260CT
7 PIN PLASTIC
TO263(M)
US1260CM
7 PIN PLASTIC
POWER FLEX(P)
US1260CP
Rev. 1.9
3/22/99
3-1

1 Page





US1260CT pdf, ピン配列
US1260
PIN DESCRIPTIONS
PIN #
3
2
5
7
6
PIN SYMBOL
Vfb2
Vfb1
Vout2
Vout1
Vin
4 Gnd
1 Vctrl
PIN DESCRIPTION
A resistor divider from this pin to the Vout #2 pin and ground sets the output
voltage. See application ckt for the divider setting for 1.5V output.
A resistor divider from this pin to Vout #1 pin and ground sets the output
voltage.See application ckt for the divider setting for 2.5V output.
The output #2 (high current) of the regulator. A minimum of 100uF capacitor
must be connected from this pin to ground to insure stability.
The output #1 (low current) of the regulator. A minimum of 100uF capacitor
must be connected from this pin to ground to insure stability.
The power input pin of the regulator. Typically a large storage capacitor is
connected from this pin to ground to insure that the input voltage does not sag
below the minimum drop out voltage during the load transient response. This
pin must always be higher than both Vout pins by the amount of the dropout
voltage(see datasheet) in order for the device to regulate properly.
This pin is connected to GND. It is also the TAB of the package.
The control input pin of the regulator. This pin via a 10resistor is connected
to the 5V supply to provide the base current for the pass transistor of both
regulators. This allows the regulator to have very low dropout voltage
which allows one to generate a well regulated 2.5V supply from the 3.3V input.
A high frequency, 1 uF capacitor is connected between this pin and Vin pin to
insure stability.
BLOCK DIAGRAM
Vin 6
Vctrl 1
7 Vout1
2 Vfb1
THERMAL
SHUTDOWN
1.20V +
4 Gnd
1260blk1-1.1
3 Vfb2
5 Vout2
Figure 1 - Simplified block diagram of the US1260
Rev. 1.9
3/22/99
3-3


3Pages


US1260CT 電子部品, 半導体
US1260
Example # 2 :
Assuming the following specifications :
VIN = 3.3V
VOUT 2 = 1.5 V
VOUT 1 = 2.5 V
IOUT 2 MAX = 1.5A
IOUT 1 MAX = 0.2 A
TA = 35° C
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 = IOUT1 × VIN VOUT1 + IOUT2 × VIN VOUT2
PD = 0.2 × (3.3 2.5) + 1.5 × (3.3 1.5) = 2.86 W
2) Assuming a TO-263 surface mount package, the junc-
tion to ambient thermal resistance of the package is:
θJA = 30° C / W for 1" square pad area
In this application, the US1260 is used on the VGA card
to convert 3.3V supply to 2.7V to power the Intel 740
chip rather than the conventional LDO which due to its
1.5V minimum dropout spec must use the 5V supply to
achieve the same result. The difference is a substantial
decrease in the power dissipation as shown below.
The maximum power dissipation of 740 chip is 5.8W,
which at 2.7V results in Io=5.8/2.7=2.15A
a) Using standard LDO, the power dissipated in the de-
vice is;
Pd=(Vin - Vo)*Io=(5-2.7)*2.15=4.94W
Using surface mount TO263 package with 25° C/W junc-
tion to air thermal resistance results in:
Tj=Pd*θja + Ta=(4.94)(25) + 25=148 ° C
This is very close to the thermal shutdown of the IC.
b) Using 1260, the power dissipated in the device is dras-
tically reduced by using 3.3V supply instead of 5V
Pd=(Vin - Vo)*Io=(3.3-2.7)*2.15=1.3W
Using surface mount TO263 package with 25° C/W junc-
tion to air thermal resistance results in:
Tj=Pd*θja + Ta=(1.3)(25) + 25=57 ° C
A reduction of 91° C in junction temperature.
3) The maximum junction temperature of the device is
calculated using the equation below :
TJ = TA + PD × θJA
TJ = 35 + 2.86 × 30 = 121 ° C
Since this is lower than our selected 135°C maximum
junction temperature (150°C is the thermal shutdown of
the device), TO-263 package is a suitable package for
our application.
Layout Consideration
The US1260 like all other high speed linear regulators
need to be properly laid out to insure stable operation.
The most important component is the output capaci-
tor, which needs to be placed close to the output
pin and connected to this pin using a plane con-
nection with a low inductance path.
US1260 in Ultra LDO, Single Output Application
The US1260 can also be used in single supply applica-
tions where the difference between input and output is
much lower than the standard 1.5V dropout that is ob-
tainable with standard LDO devices. The schematic in
figure 6 shows the application of the US1260 in a single
supply with the second LDO being disabled.
3-6
Rev. 1.9
3/22/99

6 Page



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部品番号部品説明メーカ
US1260CM

DUAL 6A AND 1A LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR

UNISEM
UNISEM
US1260CP

DUAL 6A AND 1A LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR

UNISEM
UNISEM
US1260CT

DUAL 6A AND 1A LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR

UNISEM
UNISEM


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