www.fairchildsemi.com
FAN1537
Dual 1A Adjustable/Fixed Low Dropout
Linear Regulators
Features
•
•
•
•
•
•
Low dropout voltage
Load regulation: 0.05% typical
On-chip thermal limiting
SO-8 and 5-lead SPAK and TO-252 DPAK packages
Fixed 3.3V, and adjustable or 2.5V or 1.8V fixed
Stable with low ESR output capacitors
Description
The FAN1537 provides 2 output voltages: 3.3V, and either
adjustable or 2.5V or 1.8V fixed with 1.0A each output
current capability. These devices have been optimized for
low voltage where transient response and minimum input
voltage are critical.
Current limit features protect the outputs against short circuit
currents. On-chip thermal limiting provides protection
against any combination of overload and ambient tempera-
ture that would create excessive junction temperatures.
The FAN1537 series regulators are available in SO-8 and
5-lead SPAK and TO-252 DPAK power packages.
Applications
•
•
•
•
•
•
Hard Disk Drives, CD-ROMs, DVDs
High efficiency linear regulators
Post regulators for switching supplies
ADSL and Cable Modems
5V to 3.3V and 2.5V linear regulators
Motherboard with multiple supplies
Typical Applications
FAN1537A
V1
V
IN
= 5V
+
22µF
NC GND
V
IN
V2
+
22µF
+
22µF
2.5V at 1.0A
3.3V at 1.0A
FAN1537B
V1
V
IN
= 5V
+
22µF
GND
FB
R1
54.9Ω
R2
124Ω
V
IN
V2
+
22µF
+
3.3V at 1.0A
1.8V at 1.0A
22µF
V2 = V
REF
(1 + R1/R2)
REV. 1.1.1 3/20/02
FAN1537
PRODUCT SPECIFICATION
Pin Assignments
FAN1537PA
FAN1537PC
FRONT VIEW
8
7
6
5
GND
GND
GND
GND
1 2 3
4 5
1 2 3
4 5
1
2
3
4
5
1
2
3
4
5
FAN1537PB
FRONT VIEW
FAN1537DA
FAN1537DC
FRONT VIEW
FAN1537DB
FRONT VIEW
TOP VIEW
V
IN
NC
V1
V2
1
2
3
4
V1
V1
V1
FB
GND
GND
NC
GND
GND
V2
V2
V2
V2
NC
V
IN
V
IN
V
IN
V
IN
8-Lead Plastic SO-8
Θ
JC
=25°C/W
5-Lead SPAK
Θ
JC
=2°C/W
5-Lead SPAK
Θ
JC
=2°C/W
5-Lead Plastic TO-252 DPAK
Θ
JC
=3°C/W Tab is GND
Pin Descriptions
Pin Name
V
IN
NC/FB
V1
V2
GND
SO-8
1
2
3
4
5, 6, 7, 8
SPAK
DPAK
1
2
4/5
5/4
3
Pin Function
Input supply voltage
For V2 fixed, no connect. For V2 adjustable, feedback voltage.
Output #1
Output #2
Ground
Absolute Maximum Ratings
Parameter
V
IN
Operating Junction Temperature Range
Storage Temperature Range
Lead Temperature (Soldering, 10 sec.)
0
-65
Min.
Max.
10
150
150
300
Unit
V
°C
°C
°C
2
REV. 1.1.1 3/20/02
FB
V1
PRODUCT SPECIFICATION
FAN1537
Electrical Characteristics
(Operating Conditions: V
IN
≤
7V, T
J
=25°C unless otherwise specified.)
The • denotes specifications which apply over the specified operating temperature range of 0°C to 125°C junction temperature.
Parameter
Output Voltages
Conditions
10mA
≤
I
OUT
≤
1A
4.75V
≤
V
IN
≤
7V
•
•
•
Output Voltage
Time to Output Voltages Valid
Reference Voltage, V
REF
Line Regulation
1,2
(both outputs)
Load Regulation
1,2
(both outputs)
Dropout Voltage
(3.3V output)
Current Limit
(both outputs)
Minimum Load Current
(both outputs)
Quiescent Current
Ripple Rejection
3
(both outputs)
Long-Term Stability
3.3V Output, V
IN
= 4.5V, I
OUT
= 1A
From V
IN
≥
4.75V
10mA
≤
I
OUT
≤
1A
4.75V
≤
V
IN
≤
7V
4.75V
≤
V
IN
≤
7V, I
OUT
= 10mA
V
IN
= 4.75V, 10mA
≤
I
OUT
≤
1A
∆
V
OUT
= 1%, I
OUT
= 1A
V
IN
= 5V
4.75V
≤
V
IN
≤
7V
V
IN
= 7V
f = 120Hz, C
OUT
= 22µF Tantalum,
V
IN
= 5V, I
OUT
= 1A
T
A
= 125°C, 1000 hrs.
•
•
•
•
•
•
•
60
0.03
0.003
50
3
2
155
Junction Temperature
10
1.0
1.3
10
6
15
1.225
1.210
1.250
1.250
0.005
0.05
1.100
1.5
•
Min.
1.764
1.742
2.450
2.420
3.234
3.200
3.2
5
1.275
1.290
0.5
0.5
1.300
Typ.
1.8
1.8
2.500
2.500
3.300
3.300
Max.
1.836
1.858
2.550
2.580
3.366
3.400
V
msec
V
%
%
V
A
mA
mA
dB
%
%
°C/W
°C/W
°C/W
°C
°C
Units
V
RMS Output Noise (% of V
OUT
) T
A
= 25°C, 10Hz
≤
f
≤
10kHz
Thermal Resistance, Junction to SO-8
Case
TO-252 DPAK
SPAK
Thermal Shutdown
Thermal Shutdown Hysteresis
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. 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. ESR = 0.2
Ω
.
4. For adjust only, V
OUT
= V
REF
(1 + R1/R2)
REV. 1.1.1 3/20/02
3
FAN1537
PRODUCT SPECIFICATION
Application Hints
External Capacitors
Like any low-dropout regulator, the FAN1537 requires
external capacitors for stability.
Input Capacitor
A Tantalum input capacitor of 22µF is recommended. This
capacitor must be located at a distance of no more than 0.5"
from the input pin of the device and returned to a clean ana-
log ground.
Output Capacitor
The FAN1537 is designed to work with Ceramic or Tantalum
load capacitors.
A value of 22µF is recommended on each output, but the
value can be reduced to 10µF to save space.
Additional capacitance can be added without limit for better
performance, e.g. improved transient response and lower
noise.
When a Ceramic multilayer capacitor is used, the X7R
dielectric is recommended which holds the capacitance
within ±15%. The output capacitor should be located not
more than 0.5" from the output pins of the device and
returned to a clean analog ground.
4
REV. 1.1.1 3/20/02
PRODUCT SPECIFICATION
FAN1537
Mechanical Dimensions
8-Lead SOIC Package
Notes:
Notes
1. Dimensioning and tolerancing per ANSI Y14.5M-1982.
2. "D" and "E" do not include mold flash. Mold flash or
protrusions shall not exceed .010 inch (0.25mm).
3. "L" is the length of terminal for soldering to a substrate.
4. Terminal numbers are shown for reference only.
5
2
2
5. "C" dimension does not include solder finish thickness.
6. Symbol "N" is the maximum number of terminals.
Symbol
A
A1
B
C
D
E
e
H
h
L
N
α
ccc
Inches
Min.
.053
.004
.013
.0075
.189
Max.
.069
.010
.020
.010
.197
Millimeters
Min.
1.35
0.10
0.33
0.20
4.80
Max.
1.75
0.25
0.51
0.25
5.00
.150
.158
.050 BSC
.228
.010
.016
8
0°
—
8°
.004
.244
.020
.050
3.81
4.01
1.27 BSC
5.79
0.25
0.40
8
0°
—
8°
0.10
6.20
0.50
1.27
3
6
8
5
E
H
1
4
D
A1
A
SEATING
PLANE
B
–C–
LEAD COPLANARITY
ccc C
α
h x 45°
C
e
L
REV. 1.1.1 3/20/02
5
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