www.fairchildsemi.com
FAN1537
Dual 1A Adjustable/Fixed Low Dropout
Linear Regulators
Features
Description
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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.
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
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.
Applications
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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
The FAN1537 series regulators are available in SO-8 and
5-lead SPAK and TO-252 DPAK power packages.
Typical Applications
FAN1537A
V1
VIN = 5V
+
3.3V at 1.0A
VIN
22µF
NC GND
2.5V at 1.0A
V2
+
+
22µF
22µF
FAN1537B
V1
VIN = 5V
+
VIN
3.3V at 1.0A
1.8V at 1.0A
V2
+
22µF
GND
FB
R1
54.9Ω
22µF
+
22µF
R2
124Ω
V2 = VREF (1 + R1/R2)
REV. 1.1.1 3/20/02
PRODUCT SPECIFICATION
FAN1537
Electrical Characteristics (Operating Conditions: VIN ≤ 7V, TJ=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
Conditions
Output Voltages
Min.
Typ.
Max.
10mA ≤ IOUT ≤ 1A
4.75V ≤ VIN ≤ 7V
•
1.764
1.742
2.450
2.420
3.234
3.200
1.8
1.8
2.500
2.500
3.300
3.300
1.836
1.858
2.550
2.580
3.366
3.400
•
3.2
1.225
1.210
V
•
•
Output Voltage
3.3V Output, VIN = 4.5V, IOUT = 1A
Units
Time to Output Voltages Valid
From VIN ≥ 4.75V
Reference Voltage, VREF
10mA ≤ IOUT ≤ 1A
4.75V ≤ VIN ≤ 7V
•
Line Regulation1,2
(both outputs)
4.75V ≤ VIN ≤ 7V, IOUT = 10mA
Load Regulation1,2
(both outputs)
V
5
msec
1.250
1.250
1.275
1.290
V
•
0.005
0.5
%
VIN = 4.75V, 10mA ≤ IOUT ≤ 1A
•
0.05
0.5
%
Dropout Voltage
(3.3V output)
∆VOUT = 1%, IOUT = 1A
•
1.100
1.300
V
Current Limit
(both outputs)
VIN = 5V
•
Minimum Load Current
(both outputs)
4.75V ≤ VIN ≤ 7V
•
Quiescent Current
VIN = 7V
•
Rejection3
Ripple
(both outputs)
f = 120Hz, COUT = 22µF Tantalum,
VIN = 5V, IOUT = 1A
Long-Term Stability
TA = 125°C, 1000 hrs.
RMS Output Noise (% of VOUT) TA = 25°C, 10Hz ≤ f ≤ 10kHz
1.5
A
10
mA
6
15
60
mA
dB
0.03
1.0
%
SPAK
Thermal Shutdown
Junction Temperature
0.003
%
50
°C/W
3
°C/W
2
°C/W
155
Thermal Resistance, Junction to SO-8
Case
TO-252 DPAK
Thermal Shutdown Hysteresis
1.3
°C
10
°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. 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 = 0.2Ω.
4. For adjust only, VOUT = VREF (1 + R1/R2)
REV. 1.1.1 3/20/02
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