AS A Low Dropout Voltage Regulator Adjustable & Fixed Output, Fast Response

Transcription

1 1.5A Low Dropout oltage Regulator Adjustable & Fixed Output, Fast Response FEATURES Adjustable Output Down To 1.2 Fixed Output oltages 1.5, 2.5, 3.3, 5.0 Output Current of 1.5A Low Dropout oltage 1.1 Typ. Extremely Tight Load And Line Regulation Current & Thermal Limiting Standard 3-Terminal Low Cost TO-220, TO-263 & TO-252 Similar To Industry Standard LT1086/LT1586 APPLICATIONS Powering GA & Sound Card Power PC Supplies SMPS Post-Regulator High Efficiency Green Computer Systems High Efficiency Linear Power Supplies Portable Instrumentation Constant Current Regulators Adjustable Power Supplies Battery charger PRODUCT DESCRIPTION The is a low power 1.5A adjustable and fixed voltage regulators that are very easy to use. It requires only 2 external resistors to set the output voltage for adjustable version. The are designed for low voltage applications that offers lower dropout voltage and faster transient response. This device is an excellent choice for use in powering low voltage microprocessor that require a lower dropout, faster transient response to regulate from +2.5 to 3.8 supplies and as a post regulator for switching supplies applications. The features low dropout of a maximum 1.2. The offers over current limit and protection against over-current faults, reversed input polarity, reversed load insertion, and positive and negative transient voltage. The I Q of this device flows into the load, which increases efficiency. The are offered in a 3-pin TO-220, TO-263 & TO-252 packages compatible with other 3 terminal regulators. For a 3A low dropout regulator refer to the AS2830 data sheet. ORDERING INFORMATION TO-220 DD PLASTIC TO-252 OPERERATING JUNCTION 3-PIN 3-PIN DPAK TEMP RANGE YU-X YT-X YR-X -45 to +125 C X = Output oltage (i.e. 1.5 for 1.5, 2.5 for 2.5 etc.). Y = Output Tolerance, Y= A for 1% or Blank for 2% Consult with factory for other fixed output voltages TO (T) PIN CONNECTIONS TO (U) TO-252 (R) /GND /GND Front iew Top iew /GND Front iew

2 ABSOLUTE MAXIMUM RATINGS Lead Temp. (Soldering, 10 Seconds) C Storage Temperature Range to +150 C Operating Junction Temperature Range... Control Section C +125 C Power Transistor C +150 C Maximum Input Supply oltage Input to Output oltage Differential ELECTRICAL CHARACTERISTICS (NOTE 1) at I OUT = 10mA, T a=25 C, unless otherwise specified. PARAMETER CONDITIONS Typ A 1.5 ersion Output oltage (Note 2) -1.5, 0 I OUT 1.5A, ersion Output oltage (Note 2) -2.5,0 I OUT 1.5A, ersion Output oltage (Note 2) -3.3, 0 I OUT 1.5A, ersion Output oltage (Note 2) -5.0, 0 I OUT 1.5A, All oltage Options Reference oltage ( REF ) 7, P P MAX Min Max Min Max 1.5 ( -) 5.75, 10mA I OUT 1.5A Min. Load Current (Note 3) 1.5 ( -) ma Line Regulation ( REF ( )) , I OUT=10mA, T J=25 C (Note 3) % , I OUT=0mA, T J=25 C (Note 2) % Units Load Regulation( REF (I OUT )) 10mA I OUT 1.5A, (-)=3, T J=25 C (Note 3) % 0 I OUT 1.5A, =7, T J=25 C (Note 2) % Dropout oltage REF=1% I OUT =1.5A (Note 3) I OUT 1.5A (Note 2) Current Limit =7 A I OUT ( MAX ) 1.4 (- ) (Note3) Long Term Stability T A=125 C, 1000 Hrs % (Note 2) Thermal Regulation T A=25 C, 20 ms pulse %/W ( (Pwr)) Temperature Stability 0.25 % ( (T)) Output Noise, RMS 10Hz to 10khz T A =25 C % O Thermal Resistance TO-220 Junction to Tab Junction to Ambient C/W DD Package Junction to Tab Junction to Ambient C/W The Bold specifications apply to the full operating temperature range. Note 1: Changes in output voltage due to heating effects are covered under the specification for thermal regulation. Note 2: Fixed ersion Only Note 3: Adjustable ersion Only

3 APPLICATION HINTS The incorporates protection against over-current faults, reversed load insertion, over temperature operation, and positive and negative transient voltage. However, the use of an output capacitor is required in order to insure the stability and the performances. Reducing parasitic resistance and inductance One solution to minimize parasitic resistance and inductance is to connect in parallel capacitors. This arrangement will improve the transient response of the power supply if your system requires rapidly changing current load condition. Stability The output capacitor is part of the regulator s frequency compensation system. Either a 22µF aluminum electrolytic capacitor or a 10µF solid tantalum capacitor between the output terminal and ground guarantees stable operation for all operating conditions. However, in order to minimize overshoot and undershoot, and therefore optimize the design, please refer to the section Ripple Rejection. Ripple Rejection Ripple rejection can be improved by adding a capacitor between the pin and ground. When pin bypassing is used, the value of the output capacitor required increases to its maximum (22µF for an aluminum electrolytic capacitor, or 10µF for a solid tantalum capacitor). If the pin is not bypass, the value of the output capacitor can be lowered to 100µF for an electrolytic aluminum capacitor or 4.7µF for a solid tantalum capacitor. However the value of the -bypass capacitor should be chosen with respect to the following equation: C = 1 / ( 6.28 * F R * ) Where C = value of the capacitor in Farads (select an equal or larger standard value), F R = ripple frequency in Hz, = value of resistor in Ohms. If an -bypass capacitor is use, the amplitude of the output ripple will be independent of the output voltage. If an bypass capacitor is not used, the output ripple will be proportional to the ratio of the output voltage to the reference voltage: M = / REF Where M = multiplier for the ripple seen when the pin is optimally bypassed. REF = Reference oltage Thermal Consideration Although the offers some limiting circuitry for overload conditions, it is necessary not to exceed the maximum junction temperature, and therefore to be careful about thermal resistance. The heat flow will follow the lowest resistance path, which is the Junction-to-case thermal resistance. In order to insure the best thermal flow of the component, a proper mounting is required. Note that the case of the device is electrically connected to the output. In case the case has to be electrically isolated, a thermally conductive spacer can be used. However do not forget to consider its contribution to thermal resistance. Assuming: = 10, = 5, I OUT = 1.5A, T A = 50 C/W, θ Heatsink Case = 6 C/W, θ Heatsink Case = 0.5 C/W, θ JC = 3 C/W Power dissipation under this condition P D = ( ) * I OUT = 7.5W Junction Temperature T J = T A + P D * (θ Case HS + θ HS + θ JC ) For Control & Power Sections T J = *(0.5+6=3) = C C < T J (max) for Control & Power Sections. In both case reliable operation is insured by adequate junction temperature.

4 Basic Adjustable Regulator I REF 5 C1 10uF OUT 3.3 C1 10uF 50µA = REF * ( 1 + / ) + I * Basic Fixed Regulator Fig.2 Basic Adjustable Regulator Output oltage Consider Figure 2. The resistance generates a constant current flow, normally the specified load current of 10mA. This current will go through the resistance to set the overall output voltage. The current I is very small and constant. Therefore its contribution to the overall output voltage is very small and can generally be ignored. Output oltage The fixed voltage LDO voltage regulators are simple to use regulators since the is preset to the specifications. It is important however, to provide the proper output capacitance for stability and improvement. For most operating conditions a capacitance of 22uF tantalum or 100uF electrolytic will ensure stability and prevent oscillation. Load Regulation Parasitic line resistance can degrade load regulation. In order not to affect the behavior of the regulator, it is best to connect directly the resistance from the resistor divider to the case, and not to the load. For the same reason, it is best to connect the resistor to the Negative side of the load. R P Parasitic Line Resistance Connect to Case of Regulator R L Connect to Load Fig.3 Basic Adjustable Regulator Rev.10/11/00

5 TYPICAL APPLICATIONS C 1 IN OUT IN OUT C 1 C 2 LOAD = REF (1 + ) + I Fig A Current output Regulator Fig. 5 Typical Adjustable Regulator (Note A) + 10µF Note A: (MIN) = (Intended ) + ( DROPOUT (MAX) ) IN *C 1 improves ripple rejection. Xc should be ~ at ripple frequency. OUT 5 121Ω 1% 150µF + C 365Ω 1 10µF* 1% (Note A) TTL Input + 10µF 1k IN 1k OUT 2N Ω 1% 365Ω 1% Note A: (MIN) = (Intended ) + ( DROPOUT (MAX) ) µF Fig. 6 Improving Ripple Rejection Fig.7 5 Regulator with Shutdown

6 TYPICAL CHARACTERISTICS

7 PACKAGE DRAWING TO-263-3L (T) ± (1.397) ( ± 0.127) 0.176± (4.470 ± 0.127) ± (1.270 ± 0.051) ± (9.042 ± 0.127) (15.24 ± 0.635) BSC (1.270) (2.616) ( ) ( ) ± (2.540 ± 0.254)

8 PACKAGE DRAWING TO-220-3L (U) 0.151D ± (3.835 D ± 0.051) ± (4.572 ± 0.127) ± (10.36 ± 0.33) ± (1.270 ± 0.051) ± (2.794 ± 0.254) ± (6.350 ± 0.254) Tapered 1 o 2 Sides ± (8.636 ± 0.254) SEATING PLANE ± ( ± 0.381) MIN (3.81 MIN) (10.41) 7 o Typ ± ( ± 0.381) TYP (1.27 TYP) ± (5.080 ± 0.254) ± (2.540 ± 0.254) ± (0.813 ± 0.127) ± 0.010/ (0.381± 0.254/-0.051) ± 0.010/ (2.667± 0.254/-0.381)

9 PACKAGE DRAWING TO252-3L (R) E b 2 -A- L 2 A A 1 C 1 -B- A -C D L 3 L 1 SEATING PLANE L H b 3 PLCS.010 M A M C e1 e b 1 c 8 A D 1 NOTES 1. Refer To Applicable Symbol List. 2. Dimensions And Tolerancing Per Ansi Y14.5m Lead Dimension Uncontrolled in L 3. TERM 4 E 1 4. Tab Contour Optional Within Dim. b 2 & L 2 And E 1 & D 1 5. D1 & E1 Establishes A Minimum Mounting Surface for Terminal L is the Termal Length for Soldering. 7. Controlling Dimension: Inch 8. 2 Mils Suggested For Postive Contact At Mounting. BACK IEW A-A S Y M B O L INCHES MM MIN MAX MIN MAX N O T E A A b b b c c D D ,5 E E ,5 e e H L L L L