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| www..com ISSUED DATE :2005/07/11 REVISED DATE :2006/03/29B G5E1286 The G5E1286 is 1.5A regulator with extremely low dropout voltage. This product is specifically designed to provide well regulated supply for applications requiring 2.8V or lower voltages from 3.3V ATX power supplies where high efficiency of the switch can be achieved without the cost and complexity associated with switching regulator. One such application is the new graphic chipsets that requires anywhere from 2.4V to 2.7V supply. 1.5A Ultra Low Dropout Positive Adjustable or Fixed-mode Regulator Description Features & maximum dropout voltage at 1.5A load current 0.5V Package Dimensions &Built-in thermal shutdown &Output current limiting &Adjustable or fixed output voltage 1.5V, 1.8V, 2.5V, 3.3V, 5.0V &Fast transient response &Good noise rejection REF. A b c D E L4 Millimeter Min. Max. 4.40 4.80 0.76 1.00 0.36 0.50 8.60 9.00 9.80 10.4 14.7 15.3 REF. L5 c1 L e L1 O Millimeter Min. Max. 6.20 6.60 1.25 1.45 13.25 14.25 1.70 REF. 2.60 2.89 3.71 3.96 Typical Application Block Diagram Pin Descriptions Name Adj (Gnd) Vsense Vin I I I/O Description A resistor divider from this pin to the Vout pin and ground sets the output voltage. (Gnd only for fixed mode) The pin is the positive side of the reference that allows remote load sensing to achieve excellent load regulation. 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 to insure that the input voltage does not sag below the minimum dropout voltage during the load transient response. This pin must always be higher than Vout in order for the device to regulate. This pin is the supply pin for the internal control circuit as well as the base drive for the pass transistor. This pin must always by higher than the Vout pin in order the device to regulate. A minimum of 100uF capacitor must be connected from this pin to ground to insure stability. The output of the regulator. A minimum of 100uF capacitor must be connected from this pin to ground to insure stability. Vctrl Vout I O G5E1286 Page: 1/4 ISSUED DATE :2005/07/11 REVISED DATE :2006/03/29B Absolute Maximum Ratings Symbol Vin Vctrl PD TST TOP Input Voltage Control Input Voltage Power Dissipation (with heat sink or amount of copper board needed.) Storage Temperature Range Operating Junction Temperature Range Parameter Ratings 16 18 2.4 ~ 4.4 -65 ~ + 150 0 ~ + 150 Unit V V W Electrical Characteristics Unless otherwise specified, these specifications apply over, Cin=1uF, Cout=10uF, and TJ =0 to 150 : . Typical value refer to TJ =25 : . Vout=Vsense Parameter Conditions MIN TYP MAX UNIT Reference Voltage G5E1286-ADJ G5E1286-15 G5E1286-18 Output Voltage G5E1286-25 G5E1286-33 G5E1286-50 Line Regulator G5E1286-XX G5E1286-ADJ G5E1286-15 Load Regulation G5E1286-18 G5E1286-25 G5E1286-33 G5E1286-50 Dropout Voltage (Vctrl-Vout) G5E1286-ADJ (fixed model) G5E1286-ADJ Dropout Voltage (Vin-Vout) G5E1286-15 G5E1286-18 G5E1286-25 G5E1286-33 G5E1286-50 Current Limit Minimum Load Current Thermal Regulation Ripple Rejection Vctrl=3.0V, Vin=2.05V, Vo=100mV, Vadj=0V Vctrl=5V, Vin=3.3V, Vadj=0V 30ms pulse Vctrl=5V, Vin=5V, Io=1.5A, Vadj=0V, TJ=25 : , Vripple=1Vpp at 120Hz G5E1286-ADJ G5E1286-15 Control Pin Current G5E1286-18 G5E1286-25 G5E1286-33 G5E1286-50 Adjust Pin Current JC hermal T Io=10mA, TJ =25 : Io=10mA, TJ =25 : Io=10mA, TJ =25 : Io=10mA, TJ =25 : Io=10mA, TJ =25 : Io=10mA, TJ =25 : Io=10mA, TJ =25 : , (Vin-Vout)=0.5V, Vctrl=Vin+1V , 2.0V Vin 12V, Vctrl=Vin+1V , 2.3V Vin 12V, Vctrl=Vin+1V , 3.0V Vin 12V, Vctrl=Vin+1V , 3.8V Vin 12V, Vctrl=Vin+1V , 5.5V Vin 12V, Vctrl=Vin+1V , Vout+0.5< Vin <12, Vctrl=Vin+1V 1.225 1.470 1.764 2.450 3.235 4.900 - 1.250 1.500 1.800 2.500 3.300 5.000 12 15 20 26 40 - 1.275 1.530 1.836 2.550 3.365 5.100 0.2 1 15 18 25 33 50 1.23 V V V V V V % % mV mV mV mV mV V (Vin-Vout)=2V, 0mA 0.26 0.38 V 1.6 60 5 0.01 70 10 0.02 - A mA %/W dB Vadj=0V, for all conditions below. Vctrl=2.75V, Vin=2.05V, Io=1.5A Vctrl=3.3V, Vin=2.3V, Io=1.5A Vctrl= Vout +1.5V, Vin= Vout +0.8V, Io=1.5A 6 25 mA Vctrl=2.75V, Vin=2.05V, Vadj=0 - 50 2.5 150 - uA /W Resistance Control Circuitry/Power Transistor Junction-to-Case Note 1: G5E1286-ADJ incorporates an internal thermal shutdown that protects the device where the junction temperature exceeds the allowable maximum junction temperature. G5E1286 Page: 2/4 ISSUED DATE :2005/07/11 REVISED DATE :2006/03/29B Functional Description Introduction The G5E1286 regulator is 5-terminal device designed specifically to provide extremely low dropout voltage comparable to the PNP type without the disadvantage of the extra power dissipation due to the base current associated with PNP regulators. This is done by bringing out the control pin of the regulator that provides the base current to the power NPN and connecting it to a voltage that is greater than the voltage present at the Vin pin. This flexibility makes the G5E1286 ideal for applications where dual inputs are available such as a computer motherboard with an ATX style power supply that provides 5V and 3.3V to the board. One such application is the new graphic chip sets that require anywhere from 2.4V to 2.7V supply. The G5E1286-ADJ can easily be programmed with the addition of two external resistors to any voltages within the range of 1.25V to 15.5V. Another major requirement of these graphic chips is the need to switch the load current from zero to several amps in tens of nanoseconds at the processor pins, which translates to an approximately 300 to 500ns of current step at the regulator. In addition, the output voltage tolerances are also extremely tight and they include the transient response as part of the specification. The G5E1286 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 number of output capacitors. Another feature of the device is its true remote sensing capability that allows accurate voltage setting at the load rather than at the device. Output Voltage Setting The G5E1286-ADJ can be programmed to any voltage in the range of 1.25V to 15.5V with the addition of R1 and R2 external resistors according to the following formula: G5E1286-ADJ The G5E1286-ADJ keeps a constant 1.25V between the Vsense pin and the Adj pin. By placing a resistor R1 across these two pins and connecting the Vsense and Vout pin together, a constant current flows through R1, adding to the Iadj current and into the R2 resistor producing a voltage equal to the (1.25/R1)*R2+Iadj*R2. This voltage is then 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 G5E1286-ADJ is 10mA, R1 is typically selected to be 121 resistor so that it automatically satisfies this condition. Notice that since Iadj is typically in the range of 50uA it only adds a small error to the output voltage and should only be considered when a very precise output voltage setting is required. Load Regulation Since the G5E1286 has separate pins for the output (Vout) and the sense (Vsense), it is ideal for providing true remote sensing of output voltage at the load. This means that the voltage drops due to parasitic resistance such PCB traces between the regulator and the load are compensated for using remote sensing. Figure following shows a typical application of the G5E1286-ADJ with remote sensing. G5E1286-ADJ G5E1286 Page: 3/4 ISSUED DATE :2005/07/11 REVISED DATE :2006/03/29B Stability The G5E1286-XX requires the use of an output capacitor as part of the frequency compensation in order to make the regulator stable. Typical designs for the microprocessor application use standard electrolytic with typical ESR in the range of 50 to 100m and an output capacitance of 100uF to 1000uF. Fortunately as the capacitance increases, the ESR decreases resulting in a fixed RC time constant. The G5E1286-XX takes advantage of the phenomena in making the overall regulator loop stable. For most applications a minimum of 100uF aluminum electrolytic capacitor insures both stability and good transient response. Thermal Design The G5E1286-XX incorporates an internal thermal 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 this number. Important Notice: All rights are reserved. Reproduction in whole or in part is prohibited without the prior written approval of GTM. GTM reserves the right to make changes to its products without notice. GTM semiconductor products are not warranted to be suitable for use in life-support Applications, or systems. GTM assumes no liability for any consequence of customer product design, infringement of patents, or application assistance. Head Office And Factory: Taiwan: No. 17-1 Tatung Rd. Fu Kou Hsin-Chu Industrial Park, Hsin-Chu, Taiwan, R. O. C. TEL : 886-3-597-7061 FAX : 886-3-597-9220, 597-0785 China: (201203) No.255, Jang-Jiang Tsai-Lueng RD. , Pu-Dung-Hsin District, Shang-Hai City, China TEL : 86-21-5895-7671 ~ 4 FAX : 86-21-38950165 G5E1286 Page: 4/4 |
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