FEATURES
•Precision Positive Series Pass Voltage Regulation
•0.45V Dropout at3A
节圆•50mV Dropout at10mA •Quiescent Current Under
650µA Irrespective of Load •Adjustable(5Lead)Output Voltage Version
•Fixed(3Lead)Versions for 3.3V and5V Outputs •Logic Shutdown Capability •Short Circuit Power Limit of 3%•V IN•I SHORT
•Low V OUT to V IN Rever Leakage
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•Thermal Shutdown DESCRIPTION
The UCC283-3/-5/-ADJ family of positive linear ries pass regulators are tailored for low drop out applications where low quiescent power is important.Fabricated with a BiCMOS technology ideally suit
ed for low input to output differential applica-tions,the UCC283-5will pass3A while requiring only0.45V of typical input voltage headroom(guaranteed0.6V dropout).The regulators include rever voltage nsing that prevents current in the rever direction.Quiescent current is always less than650µA.The devices have been internally compensated in such a man-ner that the need for a minimum output capacitor has been eliminated.
UCC283-3and UCC283-5versions are in3lead packages and have pret outputs at3.3V and5.0V respectively.The output voltage is regulated to1.5%at room tem-perature.The UCC283-ADJ version,in a5lead package,regulates the output volt-age programmed by an external resistor ratio.
Short circuit current is internally limited.The device responds to a sustained over-current condition by turning off after a T ON delay.The device then stays off for a pe-riod,T OFF,that is32times the T ON delay.The device then begins pulsing on and off at the T ON/(T ON+T OFF)duty cycle of3%.This drastically reduces the power dissipa-tion during short circuit and means heat sinks need only accommodate normal op-eration.On the3leaded versions of the device T ON is fixed at750µs,on the adjustable5leaded versions an external capacitor ts the on time—the off time is always32times T ON.The external timing control pin,CT,on the five leaded ver-sions also rves as a shutdown input when pulled low.
Internal power dissipation is further controlled with thermal overload protection cir-cuitry.Thermal shutdown occurs if the junction temperature exceeds165°C.The chip will remain off until the temperature has dropped20°C.
The UCC283ries is specified for operation over the industrial range of−40°C to +85°C,and the UCC383ries is specified from0°C to+70°C.The devices are available in3and5pin TO-220and TO-263power packages.
UCC383-3/-5/-ADJ
Low Dropout3Ampere Linear Regulator Family
BLOCK DIAGRAM
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ABSOLUTE MAXIMUM −0.−0.3to9V −65°C to+150°C −55°C to+150°C Lead Temperature(Soldering,10c.).............+300°C Currents are positive into,negative out of the specifie
d termi-nal.Consult Packaging Section of Databook for thermal limita-tions and considerations of packages.All voltages are referenced to GND.CONNECTION
DIAGRAMS
ELECTRICAL CHARACTERISTICS:Unless otherwi stated,the specifications hold for T A=0°C to70°C for the UCC383-X ries,−40°C to+85°C for the UCC283-X,V VIN=V VOUT+1.5V,I OUT=10mA,C IN=10µF,C OUT=22µF.For the
英文搜索引擎283-ADJ,V VIN=6.5V,CT=750pF,T J=T A.
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS UCC283-5Fixed5V,3A Family
Output Voltage T J=25°C 4.9255 5.075V
Over Temperature 4.875 5.125V Line Regulation V VIN=5.15V to9V210mV Load Regulation I OUT=10mA to3A1020mV Dropout Voltage,V DROPOUT=V VIN−V VOUT I OUT=3A,VOUT=4.85V0.40.6V
I OUT=1.5A,VOUT=4.85V0.20.45V
I OUT=10mA,VOUT=4.85V50150mV
Peak Current Limit V VOUT=0V45 6.5A Overcurrent Threshold34 5.5A Current Limit Duty Cycle V VOUT=0V35% Overcurrent Time Out,T ON V VOUT=0V4007501400µs Quiescent Current No load400650µA Rever Leakage Current0V<V VIN<V VOUT,V VOUT≤5.1V,at V VOUT075m A UVLO VIN where VOUT pass current 2.6 2.83V Note1:Tab=GND
ELECTRICAL CHARACTERISTICS:Unless otherwi stated,the specifications hold for T A=0°C to70°C for the UCC383-X ries,−40°C to+85°C for the UCC283-X,V VIN=V VOUT+1.5V,I OUT=10mA,C IN=10µF,C OUT=22µF.For the
283-ADJ,V VIN=6.5V,CT=750pF,T J=T A.
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS UCC283-3Fixed3.3V,3A Family
Output Voltage T J=25°C 3.25 3.3 3.35V
Over Temperature 3.22 3.38V Line Regulation V VIN=3.45V to9V27mV Load Regulation I OUT=10
mA to3A715mV Dropout Voltage,V DROPOUT=V VIN-V VOUT I OUT=3A,VOUT=3.15V0.51V
I OUT=1.5A,VOUT=3.15V0.250.6V
I OUT=10mA,VOUT=3.15V50150mV
Peak Current Limit V VOUT=0V45 6.5A Overcurrent Threshold34 5.5A Current Limit Duty Cycle V VOUT=0V35% Overcurrent Time Out,T ON V VOUT=0V4007501400µs Quiescent Current No load400650µA Rever Leakage Current0V<V VIN<V VOUT,V VOUT≤3.35V,at V VOUT075m A UVLO VIN where VOUT pass current 2.6 2.83V UCC283-ADJ Adjustable Output,3A Family
Regulating Voltage at ADJ Pin T J=25°C 1.23 1.25 1.27V
Over Temperature 1.22 1.28V Line Regulation,at ADJ Input V VIN=V VOUT+150mV to9V13mV Load Regulation,at ADJ Input I OUT=10mA to3A25mV Dropout Voltage,V DROPOUT=VIN−VOUT V VIN>4V,I OUT=3A0.40.6V
V VIN>3V,I OUT=1.5A0.20.45V
V VIN>3V,I OUT=10mA50150mV Peak Current Limit V VOUT=0V,VIN=6.5V45 6.5A Overcurrent Th
reshold V VIN=6.5V34 5.5A Current Limit Duty Cycle V VOUT=0V35% Overcurrent Time Out,T ON V VOUT=0V,CT=1500pF750µs Rever Leakage Current0V<V VIN<V VOUT,V VOUT≤9V,at V VOUT0100m A Bias current at ADJ Input100250nA Quiescent Current No load400650µA Shutdown Threshold At CT Input0.250.45V Quiescent Current in Shutdown V VIN=10V4075µA UVLO VIN where VOUT pass current 2.6 2.83V麻醉学专业
PIN DESCRIPTIONS
ADJ:Adjust pin for the UCC283-ADJ version only.Feed-back pin for the linear regulator.Program the output volt-age with R1connected from ADJ to GND and R2connected from VOUT to ADJ.Output voltage is given by:
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VOUT V R R R =
·+125121
.CT:Short circuit timing capacitor and shutdown input for the UCC283-ADJ version.Pulling CT below 0.25V turns off the regulator and places it in a low quiescent current mode.A timing capacitor,C,from
CT to GND programs the duration of the puld short circuit on-time.On-time,T ON ,is approximately given by:T ON =500k ·C .
GND:Reference ground.
VIN:Input voltage,This pin must be bypasd with a low ESL/ESR 1µF or larger capacitor to GND.VIN can range from (VOUT +V DROPOUT )to 9V .If VIN is reduced to zero while VOUT is held high,the rever leakage from VOUT to VIN is less than 75µA.
VOUT:Regulated output voltage.A bypass capacitor is not required at VOUT,but may be desired for good tran-sient respon.The bypass capacitor must not exceed a maximum value in order to insure the regulator can
start.
ORDERING INFORMATION
Temperature
Range Package Output Voltage
2:–40°C to +85°C T:TO-2203: 3.3V 3:0°C to +70°C
TD:TO-263
5:5V ADJ:Adjustable
Table I.Package Information
Overview
The UCC383family of low dropout linear (LDO)regula-tors provide a regulated output voltage for applications with up to 3A of load current.The regulators feature a low dropout voltage and short circuit protection,making their u ideal for demanding high current applications requiring fault protection.Short Circuit Protection
The UCC383provides unique short circuit protection circuitry that reduces power dissipation during a fault.When an overload situation is detected,the device enters a puld mode of operation at 3%duty
cycle reducing the heat sink requirements during a fault.The UCC383has two current thresholds that determine its behavior during a fault as shown in Figure 1.When the regulator current exceeds the overcurrent threshold for a period longer than T ON ,the UCC383shuts off for a period (T OFF )which is 32times T ON .During an overload,the regulator actively limits the maximum current to the peak current limit value.The peak current limit is nominally 1Amp greater than the overcurrent threshold.The regulator will continue in puld mode until the fault is cleared as illustrated in Figure 1.Short Circuit Protection
A capacitive load on the regulator’s output will appear as a short circuit during start-up.If the capacitance is too
large,the output voltage will not come into regulation during the initial T ON period and the UCC383will enter puld mode operation.The peak current limit,T ON period,and load characteristics determine the maximum value of output capacitor that can be charged.For a constant current load the maximum output capacitance is given as follows:
()C I I T V Farads OUT CL LOAD ON
OUT
(max)=-·
(1)
For worst ca calculations the minimum values of on time (T ON )and peak current limit (I CL )should be ud.The adjustable version allows the T ON time to be adjusted with a capacitor on the CT pin:
T C Farad ON ADJ (),()=·500000m microconds (2)
()
T C Farads ON (c),m m =·500000For a resistive load (R LOAD )the maximum output capacitor can be estimated from:
C T R n V I R OUT ON LOA
D OUT
CL LOAD (max)(c)
=
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(3)APPLICATION INFORMATION
Dropout Performance
Referring to the Block Diagram,the dropout voltage of the UCC383is equal to the minimum voltage drop(V IN to V OUT)across the N-Channel MOSFET.The dropout voltage is dependent on operating conditions such as load current,input and load voltages,as well as temperature.The UCC383achieves a low RDS(ON) through the u of an internal charge-pump(V PUMP)that drives t
he MOSFET gate.Figure2depicts typical dropout voltages versus load current for the3.3V and5V versions of the part,as well as the adjustable version programmed to3.0V.
Figure3.depicts the typical dropout performance of the adjustable version with various output voltages and load currents.
Operating temperatures also effect the RDS(ON)and dropout voltage of the UCC383.Figure 4.graphs the typical dropout for the3.3V and5V versions with a3A load over
temperature.
APPLICATION INFORMATION(cont.)
OUT VOUT
Voltage Programming and Shutdown Feature for Adjustable Version
A typical application circuit bad on the UCC383adjust-able version is shown in Figure5.The output voltage is externally programmed through a resistive divider at the ADJ pin.
V R
R
volts
OUT =·+
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The maximum programmed output voltage is constrained by the9V absolute rating of the IC(this includes the charge pump voltage)and its ability to enhance the N-Channel MOSFET.Unless the load current is below the 3A rating of the device,output voltages above7V are not recommended.The minimum output voltage can be pro-grammed down to1.25V,however,the input voltage must always be greater than the UVLO of the part.
The adjustable version includes a shutdown feature,lim-iting quiescent current to40uA typical.The UCC383is shutdown by pulling the CT pin to below0.25V.As shown in Figure4,a small logic level MO
SFET or BJT transistor in parallel with the timing capacitor can be driven with a digital signal,putting the device in shutdown.If the CT pin is not pulled low,the IC will internally pull up on the pin enabling the regulator.The CT pin should not be forced high,as this will interfere with the short circuit pro-tection feature.Selection of the timing capacitor is ex-plained in Short Circuit Protection.
The adjustable version can be ud in applications re-quiring remote voltage itoring a voltage other than or not directly tied to the VOUT pin).This is possible since the inverting input of the voltage amplifier (e Block Diagram)is brought out to the ADJ pin.Thermal Design
The Packing Information ction of the data book con-tains reference material for the thermal ratings of various packages.The ction also includes an excellent article Thermal Characteristics of Surface Mount Packages,that is the basis of the following discussion.
Thermal design for the UCC383includes two modes of operation,normal and puld mode.In normal opera-tion,the linear regulator and heat sink must dissipate power equal to the maximum forward voltage drop multi-plied by the maximum load current.Assuming a constant current load,the expected heat ri at the regulator’s junction can be calculated as follows:
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T P
RISE DISS jc ca
()q q q
=·+°C(5)
Where theta,(θ)is thermal resistance and P DISS is the power dissipated.The thermal resistance of both the TO-220and TO-263packages(junction to ca)is3de-grees Celsius per Watt.In order to prevent the regulator from going into thermal shutdown,the ca to ambient theta must keep the junction temperature below150°C. If the LDO is mounted on a5square inch pad of1ounce copper,for example,the thermal resistance from junction to ambient becomes60degrees Celsius per Watt.If a lower thermal resistance is required by the application, the device heat sinking would need to be improved.
temperature with a
3A load version.
