Sipex AS1582U-X 3a ultra low dropout voltage regulator fast response, adjustable & fixed Datasheet

AS1582
3A Ultra Low Dropout Voltage Regulator
Fast Response, Adjustable & Fixed
FEATURES
APPLICATIONS
• Low Dropout Voltage 500mV at 3A Full Load Current
• Fixed Output Voltages of 3.3V, 2.8V & 2.5V
• Adjustable Output Down to 1.2V from ATX Power Supply
• Extremely Tight Voltage and Line Regulation
• Standard 5-Terminal Low Cost TO-220 & TO-263
• 3.3V to 2.8V ATX Power Supplies
• 3.3V to 2.9V for Portable PENTIUM
 Processor
• 5V to 3.5V VRE Supply
• High Efficiency “Green” Computer Systems
PRODUCT DESCRIPTION
The AS1582 is a 3A Low Dropout Regulator with extremely low dropout voltage. The adjustable version requires only two external
resistors to set the output voltage. The fixed version has a preset output of 3.3V, 2.8V or 2.5V and does not require any external
resistors. The AS1582 features a low dropout of less than 400mV(typ.) and offers fast transient response. This device is suitable for
Pentium applications requiring 2.8V or 2.5V from 3.3V ATX power supplies, where a low current input voltage 1V greater than
the output voltage is needed. With an external sense pin the load regulation is less than 1mV. This device is an excellent choice for
the use in powering low voltage microprocessors that require a lower dropout, fast transient response to regulate from 3.3V and 5V
supplies. The AS1582 is also an excellent choice as a post regulator for switching supplies applications.
The AS1582 offers full protection against over-current faults, reversed input polarity, over temperature operation and positive and
negative transient voltage.
The AS1582 is offered in a 5 pin TO-220 and TO-263 compatible with industry standard 5-terminal regulators. For 7A, 5A and 1.5A
ultra low dropout versions refer to AS1580, AS1581 and AS1583 data sheets respectively.
ORDERING INFORMATION
TO-22O
5-PIN
AS1582U
AS1582U-X
TO-263
5-PIN
AS1582T
AS1582T-X
OUTPUT
Adjustable
Fixed
Consult with factory for other fixed output voltages.
X= Output Voltage (3.3V, 2.8V or 2.5V)
PIN CONNECTIONS
TO-220-5 (U)
TO-263-5 (T)
AS1582
1 2 3 4 5
1.
2.
3.
4.
5.
SENSE
ADJ or FIXED
VOUT
VCTRL
VIN
AS1582
1 2 3 4 5
1. SENSE
2. ADJ or FIXED
3. V OUT
4. V CTRL
5. V IN
Top View
Front View
Rev. 10/2/00
AS1582
ABSOLUTE MAXIMUM RATINGS
Power Dissipation.................................................... Internally Limited
Lead Temp (soldering, 10 seconds)........................................... 300°C
Storage Temperature Range ...................................... -65ºC to +150ºC
Operating Junction Temperature Range
AS1582 Control Section................................................0ºC to +125ºC
AS1582 Power Transistor .............................................0ºC to +150ºC
Input Supply Voltage ..........................................................6V
VCTRL Input Voltage ..........................................................13V
ELECTRICAL CHARACTERISTICS at VS =14V, Ta=25°C, Io=10mA, C2=100µF, unless otherwise specified. (Note 1)
(Boldface applies over full temperature range).
Parameters
Conditions
Min
AS1582
Typ
Units
Max
2.5V Version
Output Voltage
VCTRL=6.0V to 12V, VIN=3.0V to 5.0V, IO=10mA
IO=10mA to
3A
2.450
2.400
2.500
2.550
2.600
V
VCTRL=6.3V to 12V, VIN=3.3V to 12V, IO=10mA
IO=10mA to
3A
2.744
2.688
2.800
2.856
2.912
V
VCTRL=6.3V to 12V, VIN=3.3V to 12V, IO=10mA
IO=10mA to 3A
3.234
3.168
3.300
3.366
3.432
V
VCTRL=2.75V, VIN=2.00V, IO=10mA
VCTRL=2.7V to 12V, VIN=2.05V to 5.5V, IO=10mA to
3A
VCTRL=2.5V to 12V, VIN=1.75V to 5.5V, IO=10mA
VADJ=0V
1.238
1.250
1.263
V
1.0
3.0
mV
2.8V Version
Output Voltage
3.3V Version
Output Voltage
All Voltage Options
Reference Voltage
Line Regulation
Load Regulation (Note1)
VCTRL=2.75V, VIN=2.1V, IO=10mA to 3A,VADJ=0V
1.0
5.0
mV
Dropout Voltage Minimum VCTRL (Note2)
(VCTRL – VOUT)
VADJ=0V
VIN=2.05V, IO=1A
1.05
1.18
V
Dropout Voltage Minimum VIN(Note2)
(VIN - VOUT)
VADJ=0V
VIN=2.75V, IO=3A
0.40
0.50
V
Current Limit
VCTRL=2.75V, VIN=2.05V,dVO=100mV,VADJ=0V
Minimum Load Current
VCTRL=5V, VIN=3.3V,VADJ=0V
Thermal Regulation
30ms Pulse
Ripple Rejection
Adjustable Pin Current
VCTRL=3.75V VIN=3.75V, IO=2.3A,VADJ=0V
TJ=25, VRIPPLE=1Vpp at 120Hz
VADJ=0V
VCTRL =2.75V, VIN=2.05V, IO=3A
VCTRL=2.75V, VIN=2.05V,VADJ=0V IO=10mA
Thermal Resistance
TO-220-5
TO-263-5
Control Pin Current
A
3.1
60
5
10
mA
0.002
0.02
%W
80
dB
60
120
50
120
mA
µA
Junction to Case (θJC)
3
°C/W
Junction to Ambient
(θJA)
Junction to Case (θJC)
50
°C/W
3
°C/W
Junction to Ambient
(θJA)
60
°C/W
The Bold specifications applying to the over full operating temperature range.
Note 1: Low duty cycle pulse testing with Kelvin connections are required to order to maintain accurate data.
Note 2: Dropout voltage is defined as the minimum differential between VIN and VOUT or VCTRL and VOUT required to maintain regulation at VOUT
99% Nominal VOUT.
Note 3: VREF is measured across Adjust pin to Sense pin.
Rev. 10/2/00
AS1582
PIN DESCRIPTION
1.
2.
3.
4.
5.
Sense = Allows Kelvin sense of VOUT at the load. (Positive side of the reference voltage of the
device).
ADJ = Negative side of the reference voltage for the device. Adding a small bypass capacitor
from the ADJ pin to ground will improve the transient response.
VOUT = Power output of the device.
VCTRL = Supply pin for the control circuitry of the device. The current flow into this pin will be
about 1% of the output current. VCTRL must be between 1.0V and 1.3V greater than the output
voltage for the device to regulate.
VIN = Output load current is supplied through this pin. VIN must be between 0.1V and 0.8V
greater than the output voltage for the device to regulate.
BLOCK DIAGRAM
(4) VCTRL
VIN (5)
S.O.A
CURRENT
LIMIT
AMPLIFIER
LIMIT
VOUT (3)
SENSE
THERMAL OVERLOAD
SENSE (1)
VOLTAGE
REGULATION
AMPLIFIER
VREF
ADJ (2)
APPLICATIONS NOTES
The AS1582 is designed as a high performance and low cost
solution for application requiring a lower dropout than
traditional NPN regulators.
The AS1582 uses a separate input voltage VCTRL (VCTRL ≥
VOUT+ 1.3V) to minimize the dropout voltage. This allows the
2.5V power for the load to come from a 3.3V system supply.
As added benefit this will reduce the heat dissipation, and
lower heatsink and cooling fan cost. A typical application
would use 5V for Vin and 3.3V for VCTRL from a motherboard
power supply to provide a nominal 2.5V output. Using the
sense pin allows to Kelvin measure the output, reducing
resistive-associated errors.
The AS1582 can power the 2.5V core voltage for
microprocessors such as Pentium, P55C, AMD5k86
and K6 and the IBM PowerPC 603EV and 604EV
processors.
*The reduction of heat dissipation is a result of the increase of the regulator
efficiency (efficiency = VOUT / VIN).
Adjustable Regulator Design
1.25V reference voltage is being developed between the
SENSE pin and the ADJ pin of the AS1582. Adding two
external resistors (see fig 1.) will allow setting the output
voltage from 1.25V to 6V. R1 is chosen so that this current is
specified minimum load current of 10mA. R2 is given by the
formula: VOUT = VREF (1+ R2/R1) + IADJ (R2). The current
flowing from the ADJ pin is typically 50µA. This ADJ pin
contributes to the final VOUT but is usually neglected.
Connecting the sense pin to the top of the resistor divider will
improve load regulation.
Lowering Noise
Using the SENSE pin to Kelvin the load will increase accuracy
of the output voltage during load regulation. For the fixed
voltage devices, adding a capacitor at the GND pin will
improve transient response. This capacitor is chosen in the
range of 1µF to 0.1µF and will depend on the amount of
output capacitance in the system.
Rev. 10/2/00
AS1582
TYPICAL APPLICATION
Fig. 1 Adjustable Regulator
3.3V
VIN
5V
VCTRL
VIN
VOUT
C1
330uF
2.5V
VOUT
AS1582
VCTRL
SENSE
ADJ
R1
124 Ω
C2
10uF
C4
2 X 330uF
R2
124 Ω
C3
.033uF
(1) V CTRL needed when VIN < 5V.
(2) V OUT = V REF (1 + R2/ R1) + I ADJ R2.
(3) V REF is measured across adjust to sense.
Fig.2 Typical Fixed Regulator
3.3V
VIN
VIN
C1
5V
VCTRL
VOUT
2.5V
VOUT
AS1582
330uF
VCTRL
SENSE
GND
C4
2 X 330uF
C2
10uF
(1) VCTRL is needed when VIN <5V.
Rev. 10/2/00
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