Fairchild Semiconductor FAN1537B Datasheet
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
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
V
IN
= 5V
22µF
V
IN
+
GND
NC
V1
V2
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 temperature 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.
3.3V at 1.0A
3.3V at 1.0A
2.5V at 1.0A
2.5V at 1.0A
+
+
22µF
22µF
+
+
22µF
22µF
FAN1537B
V
IN
= 5V
22µF
V
IN
+
V1
V2
GND FB
V2 = V
(1 + R1/R2)
REF
R1
54.9Ω
R2
124Ω
+
+
22µF
22µF
+
+
22µF
22µF
3.3V at 1.0A
3.3V at 1.0A
1.8V at 1.0A
REV. 1.1.1 3/20/02
FAN1537 PRODUCT SPECIFICATION
Pin Assignments
V
NC
1
IN
2
V1
3
V2
4
8-Lead Plastic SO-8
TOP VIEW
Θ
=25°C/W
JC
FAN1537PA
FAN1537PC
FRONT VIEW
GND
8
GND
7
GND
6
GND
5
12345
IN
V
5-Lead SPAK
Θ
JC
NC
GND
=2°C/W
V1
V2
FAN1537PB
FRONT VIEW
12345
IN
FB
GND
=2°C/W
V2
V
5-Lead SPAK
Θ
JC
V1
FAN1537DA
FAN1537DC
FRONT VIEW
12345 12345
IN
V
V1
NC
GND
5-Lead Plastic TO-252 DPAK
=3°C/W Tab is GND
Θ
JC
Pin Descriptions
SPAK
Pin Name SO-8
V
IN
1 1 Input supply voltage
NC/FB 2 2 For V2 fixed, no connect. For V2 adjustable, feedback voltage.
V1 3 4/5 Output #1
V2 4 5/4 Output #2
GND 5, 6, 7, 8 3 Ground
DPAK Pin Function
V2
FAN1537DB
FRONT VIEW
IN
FB
V
GND
V2
V1
Absolute Maximum Ratings
Parameter Min. Max. Unit
V
IN
Operating Junction Temperature Range 0 150 °C
Storage Temperature Range -65 150 °C
Lead Temperature (Soldering, 10 sec.) 300 °C
10 V
2
REV. 1.1.1 3/20/02
≤
≤
≤
•
≥
≤
≤
•
≤
•
≤
•
∆
•
•
≤
•
•
PRODUCT SPECIFICATION FAN1537
Electrical Characteristics
(Operating Conditions: V
IN
7V, T
=25°C unless otherwise specified.)
J
The • denotes specifications which apply over the specified operating temperature range of 0°C to 125°C junction temperature.
Parameter Conditions Min. Typ. Max. Units
Output Voltages 10mA ≤ I
4.75V ≤ V
Output Voltage 3.3V Output, V
Time to Output Voltages Valid From V
Reference Voltage, V
REF
10mA ≤ I
IN
4.75V ≤ V
Line Regulation
1,2
4.75V ≤ V
1A
OUT
IN
7V
= 4.5V, I
IN
OUT
= 1A
•
•
•
1.764
1.742
2.450
2.420
3.234
3.200
1.8
1.8
2.500
2.500
3.300
3.300
3.2 V
1.836
1.858
2.550
2.580
3.366
3.400
4.75V 5 msec
OUT
IN
IN
1A
7V
7V, I
OUT
= 10mA
1.225
1.210
1.250
1.250
1.275
1.290
0.005 0.5 %
V
V
(both outputs)
Load Regulation
1,2
V
= 4.75V, 10mA ≤ I
IN
OUT
1A
0.05 0.5 %
(both outputs)
Dropout Voltage
V
OUT
= 1%, I
OUT
= 1A
1.100 1.300 V
(3.3V output)
Current Limit
V
IN
= 5V
1.3 1.5 A
(both outputs)
Minimum Load Current
4.75V ≤ V
IN
7V
10 mA
(both outputs)
Quiescent Current V
Ripple Rejection
3
(both outputs)
Long-Term Stability T
RMS Output Noise (% of V
OUT
Thermal Resistance, Junction to
Case
Thermal Shutdown
Thermal Shutdown Hysteresis Junction Temperature
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
(1 + R1/R2)
REF
= 7V
IN
f = 120Hz, C
V
= 5V, I
IN
= 125°C, 1000 hrs.
A
)T
= 25°C, 10Hz ≤ f ≤ 10kHz
A
OUT
OUT
= 1A
SO-8
= 22µF Tantalum,
615mA
60 dB
0.03 1.0 %
0.003 %
50 °C/W
TO-252 DPAK 3 °C/W
SPAK
2 °C/W
155 °C
10 °C
REV. 1.1.1 3/20/02
3
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