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SU1084
5A Low Dropout Positive
Elektronische Bauelemente
RoHS Compliant Product
Adjustable or Fixed-Mode Regulator
Description
The SU1084 is a low dropout at positive adjustable or fixed-mode regulator with min. of 5A output current capability. The product is specifically designed to provide well-regulated supply for low voltage IC applications such as high-speed bus termination and low current 3.3V logic supply. SU1084 is also well suited for other applications such as VGA cards. SU1084 is guaranteed to have lower than 1.5V dropout at full load current making it ideal to provide well regulated outputs of 1.25V to 3.3V with 4.7 to 12V input supply.
Features
* 1.5V Max. Dropout At Full Load Current
* Adjustable Output Voltage or Fixed 1.5V,1.8V,2.5V,3.3V,5.0V * Output Current Limiting * Good Noise Rejection * Fast Transient Response * Built-in Thermal Shutdown
REF. A b L4 c L3 L1 E Millimeter REF. Min. Max. 4.40 4.80 c2 0.76 1.00 b2 0.00 0.30 B D 0.36 0.5 e 1.50 REF. L 2.29 2.79 9.80 10.4 L2 Millimeter Min. Max. 1.25 1.45 1.17 1.47 8.6 9.0 2.54 REF. 14.6 15.8 0 8 1.27 REF.
Block Diagram
Typical Circuit
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Any changing of specification will not be informed individual
01-Jun-2002 Rev. A
Page 1 of 4
SU1084
Elektronische Bauelemente
5A Low Dropout Positive Adjustable or Fixed-Mode Regulator
Pin Descriptions
Name Adj (GND) Vout O I/O PIN# 1 2 Adjustable (Ground only for fixed mode) The output of the regulator. A minimum of 10uF capacitor must be connected from this pin to ground to insure stability. The input pin of regulator .Typically a large storage capacitor is connected from this pin to ground ge not sag minimum dropout voltage during load to insure that the input voltage doesnot sag below the minimum dropout voltage during thetheload s not sag below theminimum dropout voltage during the load transient response .This pin must always be 1.5Vhigher than Vout in inorder for the device to higher Vout order the device to VV higher thanVout inorder for for the device to regulate properly. FUNCTION
Vin
I
3
Absolute Maximum Ratings
Parameter
DC Supply Voltage Power Dissipation Storage Temperature Range Operating Juction Temperature Range
Symbol
VIN PD TST TOP
Ratings
-0.3 to 12
Internally Limited -65~+150 0~+150
Unit
V
o o
C
C
Electrical Characteristics
Symbol VREF Parameter SU1084ADJ SU1084-1.5 SU1084-1.8 Output Voltage SU1084-2.5 SU1084-3.3 SU1084-5.0 Line Regulation SU1084XXX SU1084ADJ SU1084-1.5 Load Regulation SU1084-1.8 SU1084-2.5 SU1084-3.3 SU1084-5.0 Vo ILIM IMIN IADJ IQ Dropout Voltage Current Limit Minimum Load Current Adjust Pin Current Quiescent Current Temperature Stability JA JC Thermal Resistance Junction-to-Ambient(No heat sink ;No air flow) Thermal Resistance Junction-to-Case Conditions(Notes) Io=10mA, Tj=25 : , (Vin-Vout )=1.5V Io=10mA, Tj=25 : , 3.0V Vin 12V Io=10mA, Tj=25 : , 3.3V Vin 12V Io=10mA, Tj=25 : , 4.0V Vin 12V Io=10mA, Tj=25 : , 4.8V Vin 12V Io=10mA, Tj=25 : , 6.5V Vin 12V Io=10mA, Vout+1.5VNote 1: See thermal regulation specifications for changes in output voltage due to heating effects. Line and load regulation are measured at a constant junction Temperature by low duty cycle pulse testing .Load regulation is measured at the output lead =1/18" from the package. Note 2: Line and load regulation are guaranteed up to the maximum power dissipation of 15W. Power dissipation is determined by the difference between input and output and the output current .Guaranteed maximum power dissipation will not be available over the full input/output range.
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Any changing of specification will not be informed individual
01-Jun-2002 Rev. A
Page 2 of 4
SU1084
Elektronische Bauelemente
5A Low Dropout Positive Adjustable or Fixed-Mode Regulator
Functional Description
Introduction The SU1084 adjustable Low Dropout (LDO) regulator is a 3 terminal device that can easily be programmed with the addition of two external resistors to any voltages within the range of 1.25V to 2.5V. The SU1084 only needs 1.5V differential between Vin and Vout to maintain output regulation, the output voltage tolerances are also extremely tight and they include the transient response as port of the specification. For example, Intel VRE specification calls for a total of +/-100mV including initial tolerance, load regulation and 0 to 5.0A load step. The SU1084 is specifically designed to meet the fast current transient needs as well as providing an accurate initial voltage, reducing the overall system cost with the need for fewer output capacitors. Output Voltage Setting The SU1084 can be programmed to any voltages in the range of 1.25V to 5V with the addition of R1 and R2 external resistors According to the following formula:
SU1084
The SU1084 keeps a constant 1.25V between the output pin and the adjust pin. By placing a resistor R1 across these two pins a constant current flows through R1, adding to the Iadj current requirement of the SU1084 is 10mA, R1 is typically selected to be 121 resistor so that It automatically satisfies the minimum current requirement .Notice that since Iadj is typically in the range of 55uA it only adds a small error to the output voltage and should only be considered when a very precise output voltage setting is required. For example, in a typical 3.3V application where R1=121 and R2=200 the error due to Iadj is only 0.3% of the nominal set point. Load Regulation Since the SU1084 is only a 3 terminal device, it is not possible to provide true remote sensing of the output voltage at the load. The best load Regulation is achieved when the bottom side of R2 is connected to the load and the top-side of R1 resistor is connected directly to the case or the Vout pin of the regulator and not to the load. It is important to note that for high current applications, this can re-present a significant percentage of the overall load regulation and one must keep the path from the regulator to the load as short as possible to minimize this effect. Stability The SU1084 requires the use of an output capacitor as part of the frequency compensation in order to make the regulator stable. For most applications a minimum of 10uF aluminum electrolytic capacitor insures both stability and good transient response. Thermal Design The SU1084 incorporates an internal shutdown that protects the device when the junction temperature exceeds the maximum allowable junction temperatures. Although this device can operate with junction temperatures in the range of 150 , it is recommended that the selected heat sink be chosen such that during maximum continuous load operation the junction temperature is kept below the temperature. Layout Consideration The output capacitors must be located as close to the Vout terminal of the device as possible .It is recommended to use a section of a layer of the PC board as a plane to connect the Vout pin to the output capacitors to prevent any high frequency oscillation that may result due to excessive trace inductance.
h tp://www.SeCoSGmbH.com/
Any changing of specification will not be informed individual
01-Jun-2002 Rev. A
Page 3 of 4
SU1084
Elektronische Bauelemente
5A Low Dropout Positive Adjustable or Fixed-Mode Regulator
Performance Characteristics
h tp://www.SeCoSGmbH.com/
Any changing of specification will not be informed individual
01-Jun-2002 Rev. A
Page 4 of 4

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