www.fairchildsemi.com
FAN1950/FAN1951
1.5A Low-Voltage Low-Dropout Regulator
Features
• 1.5A minimum guaranteed output current
• 500mV maximum dropout at 1.5A
Ideal for 2.5V to 1.8V or 1.65V conversion
Ideal for 3.0V to 2.5V conversion
• Current Limiting and Thermal shutdown
• External Shut-down control (FAN1951 only)
• Error flag output (FAN1951 only)
• Fast transient response
• Low ground current
General Description
The FAN1950 and FAN1951 are 1.5A low-dropout linear
regulators that provide a low voltage, high current output
with a minimum of external components. Both of these
devices use a PNP output pass element achieving a maxi-
mum 500mV dropout at 1.5A load current. In addition these
devices offer overcurrent limit and thermal shutdown
features to ensure full protection.
The FAN1951 offers a logic level enable pin and an error
flag output to indicate undervoltage and over-current condi-
tions. 1.8V and 2.5V fixed output versions are available.
3.3V, 1.65V and 1.5V options are available upon request.
Applications
• General purpose conversion for low-voltage CPUs,
DSP and FPGAs
• SMPS post regulator
• Cable/Satellite set-top boxes
• PCI Graphics adapter cards
Typical Application
FAN1950-2.5V
3.0V
IN
OUT
GND
2.5V
10µF
100KΩ
Error Output
On/Off
FLAG
EN
GND
FAN1951-1.8V
2.5V
IN OUT
1.8V
10µF
REV. 0.1.6 8/30/04
FAN1950/FAN1951
Pin Assignments
FAN1950Dx
FRONT VIEW
FAN1951Dx
FRONT VIEW
1
2
3
1
2
3
4
5
GND (TAB)
GND (TAB)
OUT
EN
OUT
IN
IN
3-Lead Plastic
TO-252 (DPAK)
5-Lead Plastic
TO-252 (DPAK)
Pin Descriptions
Pin Number
FAN1950
NA
1
2
3
NA
FAN1951
1
2
3
4
5
Pin Name
EN
IN
GND
OUT
FLAG
Pin Function Description
Enable (Input) – TTL/CMOS compatible input.
Logic HIGH enables
the output
Input Supply Voltage
Ground.
This pin and TAB are ground.
Output Voltage
Error Flag (Output).
Open-collector output. Active-low indicates an
output fault condition.
2
FLAG
REV. 0.1.6 8/30/04
FAN1950/FAN1951
Absolute Maximum Ratings
Absolute maximum ratings are the values beyond which the device may be damaged or have its useful life impaired.
Functional operation under these conditions is not implied.
Parameter
Supply Voltage: IN
Enable Voltage: EN
FLAG voltage: FLAG
Junction Temperature (T
J
)
Storage Temperature
Lead Soldering Temperature, 10 seconds
Power Dissipation (P
D
)
Min.
-0.2
-0.2
-0.2
–55
–65
Typ.
Max.
15
15
15
150
150
300
Internally
Limited
Units
V
V
V
°C
°C
°C
W
Recommended Operating Conditions
Parameter
Supply Voltage
Package Thermal Resistance (
θ
JC
)
Junction Operating Temperature
TO-252
-40
Conditions
Min.
2.25
3
125
Typ.
Max.
14
Units
V
°
C/W
°
C
Electrical Specifications
(V
IN
= V
OUT
+ 1V, V
EN
= 2.5V, T
j
= +25°C unless specified otherwise)
The • denotes specifications which apply over the full operating temperature range.
Parameter
Output Voltage (V
OUT
) Tolerance
Conditions
10mA
≤
I
OUT
≤
1.0A,
10mA
≤
I
OUT
≤
1.5A,
V
OUT
+ 1V
≤
V
IN
≤
8V
I
OUT
= 10mA, V
OUT
+ 1V
≤
V
IN
≤
14V
V
IN
= V
OUT
+ 1V,
10mA
≤
I
OUT
≤
1.5A
I
OUT
= 1.5A,
∆
V
OUT
= -1%
•
Ground Current
Minimum Load Current
Current Limit
EN Input Voltage (FAN1951 only)
EN Input Current (FAN1951 only)
FLAG Threshold Voltage
(FAN1951 only)
FLAG Output Leakage Current
4
(FAN1951 only)
FLAG Output-Low Voltage
(FAN1951 only)
I
OUT
= 750mA
I
OUT
= 1.5A
V
OUT
+ 1V
≤
V
IN
≤
8V
V
OUT
= 0V, V
IN
= V
OUT
+ 1V
V
IH
(On)
V
IL
(Off)
I
IH
, V
EN
= 2.25V
I
IL
, V
EN
= 0.8V
Low threshold, % V
OUT
High threshold, % V
OUT
Hysteresis
V
FLAG
= 14V
I
OL
= 250µA
•
•
•
•
•
•
•
•
•
93
99.2
1
2
400
2.25
0.8
30
4
10
20
5
2.5
•
•
Min.
-2
-2.5
.06
0.2
350
500
20
10
mA
mA
mA
A
V
V
µA
µA
%
%
%
µA
mV
Typ.
Max.
2
2.5
0.5
1
Units
%
Line Regulation
1,2
Load Regulation
1,2
Dropout Voltage
3
%
%
mV
REV. 0.1.6 8/30/04
3
FAN1950/FAN1951
Parameter
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
Shutdown output current
Conditions
Min.
Typ.
150
10
Max.
Units
°C
°C
V
EN
≤
0.8V, V
IN
≤
8V, V
OUT
= 0V
•
20
µA
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. 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. Dropout voltage = V
IN
– V
OUT
when V
OUT
decreases to 98% of its nominal output voltage with V
IN
= V
OUT
+ 1V. For output
voltages below 2.25V, dropout voltage is the input-to-output voltage differential with the minimum input voltage being 2.25V.
Minimum input operating voltage is 2.25V.
4. Flag output cannot be pulled to a voltage higher than V
IN
.
4
REV. 0.1.6 8/30/04
FAN1950/FAN1951
Typical Performance Characteristics
Dropout Voltage vs. Output Current
0.6
0.5
Dropout (V)
0.4
-40°C
+125°C
0.6
0.5
Dropout (V)
+75°C
Dropout Voltage vs. Temperature
IL = 1.5A
0.4
IL = 1A
0.3
-10°C
0.3
0.2
0.1
0.2
+25°C
0.1
0
0.5
0.7
0.9
1.1
1.3
1.5
0
-50
Load Current (A)
50
100
Tj
Vout = 2.5V, 1.8V, Iout = 1A, 1.5A
0
150
Ground Current vs. Load Current
Vin = Vout + 1V, 25°C
25.00
20.00
15.00
I gnd (mA)
10.00
5.00
0.00
0
500
1000
1500
2000
Load Current (mA)
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0
Ground Current vs. Supply Voltage
Vin = Vout + 1V, 25°C
Ground Current (mA) (V)
Ground Current (mA)
5
10
Vin (V)
Iout = 10mA
15
20
REV. 0.1.6 8/30/04
5
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