Page 1
US1050-33
5A LOW DROPOUT POSITIVE
FIXED 3.3V OUTPUT REGULATOR
FEATURESFEATURES
Guaranteed < 1.3V Dropout at Full Load
Current
Fast Transient Response
1% Voltage Reference Initial Accuracy
Output Current Limiting
Built-in Thermal Shutdown
APPLICATIONSAPPLICATIONS
Standard 3.3V Chip-Set and Logic Applications
TYPICAL APPLICATIONTYPICAL APPLICATION
DESCRIPTIONDESCRIPTION
The US1050-33 product is a low dropout three terminal
fixed 3.3V output regulator with minimum of 5A output
current capability. This product is specifically designed
to provide well regulated supply for low voltage IC applications requiring 3.3V output. The US 1050-33 is guar-
anteed to have <1.3V drop out at full load current
making it ideal to provide well regulated output with supply voltage as low as 4.6V input.
5V
C1
330uF
Vin
3
Vout
Gnd
2
1
US1050-33
1050-33app1-1.1
Typical application of US1050-33
Tj (°C) 3 PIN PLASTIC 3 PIN PLASTIC 2 PIN PLASTIC 3 PIN PLASTIC
TO220 (T) TO263 (M) POWER FLEX (P) TO252 (D)
0 TO 150 US1050-33CT US1050-33CM US1050-33CP US1050-33CD
3.3V / 5A
C2
330uF
Rev. 1.1
10/27/00
2-33
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US1050-33
ABSOLUTE MAXIMUM RATINGSABSOLUTE MAXIMUM RATINGS
Input Voltage (Vin) .................................................................. 7V
Power Dissipation ............................................ Internally Limited
Storage Temperature Range .............................. -65°C TO 150°C
Operating Junction Temperature Range .................. 0°C TO 150°C
PACKAGE INFORMATIONPACKAGE INFORMATION
3 PIN PLASTIC TO220 ( T ) 3 PIN PLASTIC TO263 ( M ) 2 PIN PLASTIC POWER FLEX ( P ) 3 PIN PLASTIC TO252 ( D )
Tab is
Vout
FRONT VIEW
FRONT VIEW
3
2
1
Vin
Vout
Gnd
Tab is
Vout
3
Vin
2
Vout
1
Gnd
Tab is
Vout
FRONT VIEW
4
3
Vin
1
Adj
θJT=2.7°C/W θJA=60°C/W θJA=35°C/W for 1" Square pad θJA=70°C/W for 1" Square pad θJA=70°C/W for 0.5" Sq pad
ELECTRICAL SPECIFICATIONSELECTRICAL SPECIFICATIONS
Unless otherwise specified ,these specifications apply over ,Cin=1uF,Cout=10uF,and Tj=0 to 150°C.Typical
values refer to Tj=25°C.
Tab is
Vout
FRONT VIEW
4
3
Vin
1
Gnd
PARAMETER SYM TEST CONDITION MIN TYP MAX UNITS
Output Voltage Vo Io=10mA,Tj=25°C,Vin=5V 3.267 3.300 3.330 V
Io=10mA, Vin=5V 3.234 3.300 3.366
Line Regulation Io=10mA,4.7V<Vin<7V 0.2 %
Load Regulation (note 1) Vin=5V,Vadj=0,10mA<Io<5A 0.4 %
Dropout Voltage
(note 2) ∆VO Note 2 , Io=5A 1.1 1.3 V
Current Limit Vin=5V,dVo=100mV 5.1 A
Minimum Load Current Vin=5V 5 10 mA
(note 3)
Thermal Regulation 30 mS PULSE,Vin-Vo=3V,Io=5A 0.01 0.02 %/W
Ripple Rejection f=120HZ ,Co=25uF Tan
Io=2.5A,Vin-Vo=3V 60 70 dB
Adjust Pin Current Change Io=10mA,Vin-Vo=1.5V,Tj=25 0.2 5 uA
Temperature Stability Vin=5V,Vadj=0V,Io=10mA 0.5 %
Long Term Stability Tj=125°C,1000 Hrs 0.3 1 %
RMS Output Noise Tj=25°C 10hz<f<10khz 0.003 %Vo
Note 1 : Low duty cycle pulse testing with Kelvin connections are required in order to maintain accurate data.
Note 2 : Drop-out voltage is defined as the minimum
differential voltage between Vin and Vout required to maintain regulation at Vout. It is measured when the output
Note 3 : Minimum load current is defined as the minimum current required at the output in order for the output voltage to maintain regulation. Typically the resistor
dividers are selected such that it automatically maintains this current.
voltage drops 1% below its nominal value.
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Rev. 1.1
10/27/00
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US1050-33
PIN DESCRIPTIONSPIN DESCRIPTIONS
PIN # PIN SYMBOL PIN DESCRIPTION
1 Gnd This pin must be connected to GND plane using a low inductance short connection.
2 Vout The output of the regulator. A minimum of 10uF capacitor must be connected
from this pin to ground to insure stability.
3 Vin The input pin of the regulator. Typically a large storage capacitor is connected
from this pin to ground to insure that the input voltage does not sag below the
minimum drop out voltage during the load transient response. This pin must
always be 1.3V higher than Vout in order for the device to regulate properly.
BLOCK DIAGRAMBLOCK DIAGRAM
Vin 3
+
CURRENT
LIMIT
THERMAL
SHUTDOWN
Figure 1 - Simplified block diagram of the US1050-33
APPLICATION INFORMATIONAPPLICATION INFORMATION
Stability
The US1050-33 requires the use of an output capacitor
as part of the frequency compensation in order to make
the regulator stable. Typical designs for microprocessor applications use standard electrolytic capacitors with
a typical ESR in the range of 50 to 100 mΩ and an
output capacitance of 500 to 1000uF. Fortunately as
the capacitance increases, the ESR decreases resulting in a fixed RC time constant. The US1050-33 takes
advantage of this phenomena in making the overall regulator loop stable.For most applications a minimum of
100uF aluminum electrolytic capacitor such as Sanyo
MVGX series ,Panasonic FA series as well as the
Nichicon PL series insures both stability and good transient response.
1050-33blk1-1.0
1.25V
2 Vout
+
1 Gnd
Rev. 1.1
10/27/00
2-35
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