www.fairchildsemi.com
FAN1581
5A Adjustable/Fixed Ultra Low Dropout Linear Regulator
Features
•
•
•
•
•
•
•
•
Ultra Low dropout voltage, 0.4V typical at 5A
1.2V Versions available for GTL termination
Remote sense operation
Fast transient response
Load regulation: 0.05% typical
0.5% typical initial accuracy
On-chip thermal limiting
TO-263, TO-252 and TO-220 packages
Description
The FAN1581, FAN1581-1.2, FAN1581-1.5, and FAN1581-
2.5 are ultra-low dropout regulators with 5A output current
capability. These devices have been optimized for low volt-
age applications including V
TT
bus termination, where tran-
sient response and minimum input voltage are critical. The
FAN1581 is ideal for low voltage microprocessor applica-
tions requiring a regulated output from 1.3V to 5.7V with a
power input supply of 1.75V to 6.5V. The FAN1581-1.5
offers fixed 1.5V with 5A current capabilities for GTL+ bus
V
TT
termination. Additionally, the FAN1581-1.2 offers fixed
1.2V output for CPU Bus termination. The FAN1581-2.5
offers fixed 2.5V with 5A current capability for logic IC
operation and processors while minimizing the overall
power dissipation.
Current limit ensures controlled short-circuit current. On-chip
thermal limiting provides protection against any combination
of overload and ambient temperature that would create exces-
sive junction temperatures.
The FAN1581 series regulators are available in the 5-pin
TO-263, TO-252 and TO-220 packages.
Applications
•
•
•
•
•
•
Support of GTL+ bus supply
Low voltage logic supply
Embedded Processor supplies
Split plane regulator
2.5V, and 1.8V Logic Families
DDR Termination Supply
Typical Applications
V
IN
= 3.3V
+
10μF
V
IN
= 3.3V
+
10μF
V
CNTL
= 5V
+
1μF
V
CNTL
= 5V
+
1μF
2.1V at 5A
+
124Ω
22μF
V
IN
= 5.75V
+
86.6Ω
10μF
V
CNTL
= 12V
+
V
IN
= 3.3V
+
10μF
V
CNTL
= 5V
+
1μF
V
IN
V
SENSE
1μF
V
IN
V
SENSE
V
IN
V
SENSE
FAN1581–2.5
V
OUT
V
CNTL
GND
2.5V at 5A
+
22μF
V
IN
V
SENSE
FAN1581
V
OUT
V
CNTL
Adj
FAN1581
V
OUT
V
CNTL
Adj
124Ω
+
22μF
5V at 5A
FAN1581-1.2
V
OUT
V
CNTL
Gnd
374Ω
1.2V at 5A
22μF
Pentium is a registered trademark of Intel Corporation. PowerPC is a trademark of IBM Corporation.
REV. 1.2.1 7/2/09
FAN1581
PRODUCT SPECIFICATION
Pin Assignments
FAN1581T
FAN1581M-1.2,
-1.5, -2.5
FRONT VIEW
FAN1581M
FRONT VIEW
FAN1581D
FRONT VIEW
FAN1581D-1.2,
-1.5, -2.5
FRONT VIEW
FRONT VIEW
1 2 3 4 5
1 2 3 4 5
1
2
3
4
5
1
2
3
4
5
1 2 3
4 5
S
ADJ
OUT
S
GND
OUT
CNTL
IN
S
ADJ
OUT
CNTL
IN
OUT
CNTL
GND
OUT
CNTL
ADJ
5-Lead Plastic TO-263
Θ
JC
=3°C/W*
Tab is out.
5-Lead TO-220
Θ
JC
=3°C/W* Tab is VOUT.
5-Lead Plastic TO-252 DPAK
Θ
JC
=3°C/W*
Tab is out.
*With package soldered to 0.5 square inch copper area over backside ground plane or internal power plane,
θ
JA
can vary from
30
°C/W
to more than 40
°C/W.
Other mounting techniques can provide a thermal resistance lower than 30
°C/W.
Pin Definitions
Pin
Number
1
Pin Name
VSense
ADJ/GND
VOUT
VCNTL
VIN
Pin Function Descrition
Remote Voltage Sense.
Connect this pin to the load to permit true remote sensing and
avoid trace drops.
Adjust or Ground.
On the FAN1581, this pin forms the feedback to determine the output
voltage. On the FAN1581-1.2, -1.5 and -2.5, connect this pin to ground.
Output Voltage.
This pin and the tab are output.
Control Voltage.
This pin draws small-signal power to control the FAN1581 circuitry.
Connect to a voltage higher than VIN, as shown in the applications circuits.
Input Voltage.
2
3
4
5
Internal Block Diagram
4
V
CNTL
, Control
5 Vin, Power
Thermal
Shutdown
Current
Limit
3 Output
1 Sense
2 Adj
Vref
Voltage Loop
Amplifier
2
REV. 1.2.1 7/2/09
CNTL
IN
S
IN
S
IN
PRODUCT SPECIFICATION
FAN1581
Absolute Maximum Ratings
Parameter
V
IN
V
CNTL
Operating Junction Temperature Range
Lead Temperature (Soldering, 10 sec.)
Storage Temperature Range
Min.
Max.
7
13.2
125
300
150
Unit
V
V
°C
°C
°C
0
-65
Electrical Characteristics
T
J
=25°C, V
OUT
= V
SENSE
, V
ADJ
= 0V unless otherwise specified.
The • denotes specifications which apply over the specified operating temperature range.
Parameter
Reference Voltage
3
Conditions
2.05V
≤
V
IN
≤
5.5V,
2.7V
≤
V
CNTL
≤
12V,
10mA
≤
I
OUT
≤
5A
3V
≤
V
IN
≤
7V (function of Vout),
10mA
≤
I
OUT
≤
5A
3V
≤
V
IN
≤
7V, 10mA
≤
I
OUT
≤
5A
4V
≤
V
IN
≤
7V, 10mA
≤
I
OUT
≤
5A
2.7V
≤
V
IN
≤
7V, 10mA
≤
I
OUT
≤
5A
1.75V
≤
V
IN
≤
5.5V, 2.5V
≤
V
CNTL
≤
12V,
I
OUT
= 10mA
V
IN
= 2.1V, V
CNTL
= 2.75V,
10mA
≤
I
OUT
≤
5A
V
IN
= 2.05V,
ΔV
REF
= 1%, I
OUT
= 5A
V
CNTL
= 2.75V,
ΔV
REF
= 1%,
I
OUT
= 5A
V
CNTL
= 2.75V,
ΔV
REF
= 1%,
I
OUT
= 5A
V
IN
= 2.05V, V
CNTL
= 2.75V
V
IN
= 2.05V, V
CNTL
= 2.75V,
I
OUT
= 10mA
V
IN
= 2.05V, V
CNTL
= 2.75V
V
IN
= 3.3V, V
CNTL
= 5V
V
IN
= 3.75V, V
CNTL
= 3.75V, f = 120Hz,
C
OUT
= 22µF Tantalum, I
OUT
= 2.5A
TO-263
SPAK
T
A
= 25°C, 30ms pulse
•
Min.
1.237
Typ.
1.250
Max.
1.263
Units
V
Adjustable Output Voltage
Output Voltage
4
Output Voltage
5
Output Voltage
6
Line Regulation
1,2
Load Regulation
1,2
Dropout Voltage Minimum
(V
CNTL
–V
OUT
)
Dropout Voltage Minimum
(V
IN
–V
OUT
)
Dropout Voltage Minimum V
IN
Current Limit
Control Pin Current
Adjust Pin Current
3
Minimum Load Current
Ripple Rejection
Thermal Resistance, Junction to
Case
Thermal Regulation
Thermal Shutdown
•
•
•
•
•
•
•
Vref
1.47
2.474
1.176
1.5
1.5
2.5
1.200
1
1
1.05
0.4
5.7
1.53
2.526
1.224
3
5
1.18
0.5
0.6
V
V
V
V
mV
mV
V
V
V
A
mA
µA
mA
dB
°C/W
•
•
•
•
•
60
5.2
0.5
3
50
5.0
80
3
2
0.002
150
6
120
10
0.02
%/W
°C
Notes:
1. See thermal regulation specifications for changes in output voltage due to heating effects. Load and line regulation are
measured at a constant junction temperature by low duty cycle pulse testing.
2. Line and load regulation are guaranteed up to the maximum power dissipation (18W). Power dissipation is determined by
input/output differential and the output current. Guaranteed maximum output power will not be available over the full input/
output voltage range.
3. FAN1581 only.
4. FAN1581-1.5 only.
5. FAN1581-2.5 only.
6. FAN1581-1.2 only.
REV. 1.2.1 7/2/09
3
FAN1581
PRODUCT SPECIFICATION
Typical Perfomance Characteristics
0.8
0.7
DROPOUT VOLTAGE (V)
OUTPUT VOLTAGE DEVIATION (%)
0.10
DI=5A
0.05
0
-0.05
-0.10
-0.15
-0.20
-50
-25
0
25
50
75
100
JUNCTION TEMPERATURE (C)
Load Regulation vs. Temperature
125
150
0.6
0.5
0.4
0.3
0.2
0.1
0.0
T=25C
T=0C
T=125C
0
1
2
3
4
5
6
OUTPUT CURRENT (A)
Dropout Voltage vs. Output Current
1.30
REFERENCE VOLTAGE
2.60
2.5V
OUTPUT VOLTAGE (V)
1.28
1.26
1.24
1.22
1.20
-75 -50 -25
2.35
2.10
1.85
1.60
1.5V
1.35
1.2V
1.10
-75 -50
0
25
50 75
TJ (C)
100 125 150 175
-25
0
25 50
TJ (C)
75 100 125 150 175
Reference Voltage vs. Temperature
Output Voltage vs. Temperature
MINIMUM LOAD CURRENT (mA)
10
8
6
4
2
0
-75 -50 -25 0
25 50 75 100 125 150 175
JUNCTION TEMPERATURE (C)
Mimimum Load Current vs. Temperature
ADJUST PIN CURRENT (A)
70
60
50
40
30
20
10
0
-75 -50
-25 0
25 50
75 100 125 150 175
JUNCTION TEMPERATURE (C)
Adjust Pin Current vs. Temperature
4
REV. 1.2.1 7/2/09
PRODUCT SPECIFICATION
FAN1581
Typical Perfomance Characteristics (continued)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
-75 -50 -25 0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (C)
Control Pin Current vs. Temperature
SHORT-CIRCUIT CURRENT (A)
CONTROL PIN CURRENT (mA)
11
10mA Load
9
7
5
3
-75 -50 -25 0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (C)
Short-Circuit Current vs.Temeperature
90
80
RIPPLE REJECTIONS (dB)
70
POWER (W)
(V
IN
—V
OUT
) 3V
0.5V V
RIPPLE
2V
I
OUT
= 5A
10
100
1K
10K
FREQUENCY (HZ)
100K
60
50
40
30
20
10
0
20
15
10
5
0
25
45
65
85
105
CASE TEMPERATURE
Maximum Power Dissipation
125
Ripple Rejection vs. Frequency
1.4
MAX. ACCEPTABLE ESR, OHM
1.2
1.0
0.8
0.6
0.4
0.2
0
0
1
2
3
LOAD CURRENT, A
FAN1581 Stability
4
5
REV. 1.2.1 7/2/09
5
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