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| eorex Features (Preliminary) EP1084 5A Low Dropout Linear Regulator Description EP1084 is a low dropout positive adjustable or fixed-mode regulator with minimum of 5.0A 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. EP1084 is also well suited for other applications such as VGA cards. EP1084 is guaranteed to have lower than 1.4V dropout at full load current making it ideal to provide well-regulated outputs of 1.25 to 3.3V with 4.7 to 12V input supply. * Output current limiting * Adjustable output voltage or fixed 1.5V, 1.8V, 2.5V, 3.3V, 5.0V * Good noise rejection * 1.4V maximum dropout at full load current * Built-in thermal shutdown * Fast transient response * Packages: TO252, TO263 Applications * PC peripheral * Low Voltage Logic Supplies * Post Regulator for Switching Power Supply Typical Application Fixed Mode Regulator 5.0V to 2.5V Adjustable Regulator VOUT= VREF x 1 + R2 R1 VREF =1.25V R1100~200 Jul. 2006 1/8 www.eorex.com eorex Pin Assignment EP1084 Ordering Information Pin Description Pin 1 2 Name FB (GND) VOUT Function Adjustable (Ground only for fixed mode) A resistor divider from this pin to the VOUT pin and ground sets the output voltage. (Ground only for Fixed-Mode) The output of the regulator. A minimum of 10uF (0.15 ESR 20) capacitor must be connected from this pin to ground to insure stability. The input pin of regulator. Typically a large storage capacitor (0.15 ESR 20) is connected from this pin to ground to insure that the input voltage does not sag below the minimum dropout voltage during the load transient response. This pin must always be 1.4V (1.3V) higher than VOUT in order for the device to regulate properly. 3 VIN Absolute Maximum Rating Symbol VI PD TSTG TOP DC Supply Voltage Power Dissipation Storage Temperature Range Operating Junction Temperature Range Item Rating (Note 2) Units V C C 15 Internally Limited -65 ~ +150 0 ~ +150 Jul. 2006 2/8 www.eorex.com eorex Electrical Characteristics (Under operating conditions) Symbol VREF Parameter Reference Voltage EP1084-adj EP1084-15 EP1084-18 EP1084-25 EP1084-33 EP1084-50 EP1084-adj EP1084-15 EP1084-18 EP1084-25 EP1084-33 EP1084-50 VD ILIMIT IO TS Dropout Voltage Current Limit Minimum Load Current Temperature Stability Thermal Resistance Thermal Resistance TO-252 TO-263 TO-252 TO-263 IOUT=10mA Junction-to-Ambient (No heat sink ;No air flow) Junction-to-Case (Control circuitry/Power transistor) Conditions TJ=25C, IOUT=10mA, (VIN -VOUT) =1.5V TJ=25C, IOUT=10mA, VOUT +1.5V Max. 1.275 0.2 1.530 1.836 2.550 3.365 5.100 1 15 18 25 33 50 1.4 10 Units V % REGLINE Line Regulation V % REGLOAD Load Regulation mV V A mA % C/W JA JC C/W Note 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. Jul. 2006 3/8 www.eorex.com eorex Typical Performance Characteristics EP1084 Jul. 2006 4/8 www.eorex.com eorex Functional Block Diagram VIN EP1084 VOUT + + Current Limit Thermal Shutdown 1.25V + - FB Introduction The EP1084 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 VIN -1.4V. The EP1084 only needs 1.4V differential between VIN and VOUT to maintain output regulation. In addition, the output voltage tolerances are also extremely tight and they include the transient response as part 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 EP1084 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 EP1084 can be programmed to any voltages in the range of 1.25V to VIN -1.4V with the addition of R1 and R2 external resistors according to the following formula: The EP1084 keeps a constant 1.25V between the output pin and the FB pin. By placing a resistor R1 across these two pins a constant current flows through R1, adding to the IFB current and into the R2 resistor producing a voltage equal to the (1.25/R1)*R2+IFB*R2 which will be added to the 1.25V to set the output voltage. This is summarized in the above equation. Since the minimum load current requirement of the EP1084 is 10mA, R1 is typically selected to be 121 resistor so that it automatically satisfies the minimum current requirement. Notice that since IFB 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 IFB is only 0.3% of the nominal set point. Jul. 2006 5/8 www.eorex.com eorex EP1084 VOUT= VREF x 1 + R2 R1 +IFBR2 Load Regulation Since the EP1084 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 EP1084 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 EP1084 incorporates an internal thermal shutdown that protects the device when the junction temperature exceeds the maximum allowable junction temperature. Although this device can operate with junction temperatures in the range of 150C, 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. Jul. 2006 6/8 www.eorex.com eorex Package Description TO-252 D b L2 EP1084 E L1 e e1 c Seating Plane c1 b1 A1 L H A DIM A A1 b b1 c c1 D E e e1 H L L1 L2 MILLIMETERS MIN. 2.18 0.89 5.20 0.45 0.45 6.35 5.40 NOM. 2.29 - 5.35 0.61 TYP. 0.52 0.52 6.58 5.57 2.28 REF. 4.57 REF. 9.00 0.51 0.64 0.88 9.70 - 0.83 - 10.40 - 1.02 1.27 0.354 0.020 0.025 0.035 0.58 0.58 6.80 6.20 0.018 0.018 0.250 0.213 MAX. 2.40 1.14 5.50 MIN. 0.086 0.035 0.205 INCHES NOM. 0.090 - 0.211 0.024 TYP. 0.020 0.020 0.259 0.219 0.090 REF. 0.180 REF. 0.382 - 0.033 - 0.409 - 0.040 0.050 0.023 0.023 0.268 0.244 MAX. 0.094 0.045 0.217 Jul. 2006 7/8 www.eorex.com eorex Package Description (Continued) TO-263 EP1084 D L2 E L L1 e b b1 c c1 A L3 DIM A b b1 c c1 D E e L L1 L2 L3 MILLIMETERS MIN. 4.06 0.51 1.14 1.14 9.65 8.65 14.61 1.27 - 2.28 NOM. 4.45 0.75 1.27 0.38 TYP. 1.27 9.97 9.15 2.54 BSC. 15.24 1.52 1.30 2.54 15.88 1.78 2.92 2.80 0.575 0.050 - 0.090 1.40 10.29 9.65 0.045 0.380 0.341 MAX. 4.83 0.99 1.40 MIN. 0.160 0.020 0.045 INCHES NOM. 0.175 0.030 0.050 0.015 TYP. 0.050 0.393 0.360 0.100 BSC. 0.600 0.060 0.051 0.100 0.625 0.070 0.115 0.110 0.055 0.405 0.380 MAX. 0.190 0.039 0.055 Jul. 2006 8/8 www.eorex.com |
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