va ALPHA {| SEMICONDUCTOR a Excellence in Analog Power Products _ ay AS2850 FEATURES Adjustable Output Down To 1.2V Fixed Output Voltages 1.5V, 2.5V, 3.3V & 5.0V Output Current Of 5A Low Dropout Voltage 1.1V Typ @ 5A. Extremely Tight Load And Line Regulation Current & Thermal Limiting Standard 3-Terminal Low Cost TO-220 & TO-263 e Similar To Industry Standard LT1085/LT1585 5A Low Dropout Voltage Regulator Adjustable & Fixed Output, Fast Response APPLICATIONS Powering VGA & Sound Card Power PCSupplies SMPS Post-Regulator High Efficiency Green Computer Systems High Efficiency Linear Power Supplies Portable Instrumentation Constant Current Regulators e Adjustable Power Supplies Battery charger PRODUCT DESCRIPTION The ALPHA Semiconductor AS2850 are low power 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 AS2850 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 +2.5V to 3.8V supplies and as a post regulator for switching supplies applications. The AS2850 features low dropout of a maximum 1.2 volts. The AS2850 offers full protection against over-current faults, reversed input polarity, reversed load insertion, and positive and negative transient voltage. On-Chip trimming adjusts the reference voltage to 1%. The Ig of this device flows into the load, which increases efficiency. The AS2850 are offered in a 3-pin TO-220 and TO-263 package compatible with other 3 terminal regulators. For a 8A low dropout regulator refer to the AS2880 data sheet. ORDERING INFORMATION TO-220 DD PLASTIC OPER.TEMP. 3-PIN 3-PIN RANGE AS2850YU-X AS2850YT-X -45 to +125C Consult with factory for other fixed output voltages X= Output Voltage (X = 1.5V, 2.5V, 3.3V, 5.0V or Blank for Adjustable). Y= Output Tolerance (Y= A or Blank) PIN CONNECTIONS Plastic TO-263 Package Plastic TO-220 Package < __ ._1V OW] =& Eev qn ouT << | _J apex Front View Front View Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94566 Tel: (925) 417-1391 Fax: (925) 417-1390 Rev.12/3/98AS2850 ABSOLUTE MAXIMUM RATINGS Lead Temp. (Soldering, 10 Seconds) ... Input Voltage ............:cccccsesseceeesseeeee Storage Temperature Range ..........ceeeeseceeee Input to Output Voltage Differential Operating Junction Temperature Range AS2850 Control Section... eeeeeeeee -45C +125C AS2850 Power Transistor...............::ceeee -45C +150C ELECTRICAL CHARACTERISTICS core 1) at Iour= 10mA, T,=25C, unless otherwise specified. PARAMETER CONDITIONS Typ AS2850A AS82850 UNITS Min Max Min Max 1.5V Version Output Voltage (Note 2) AS2850-1.5V, 0 <Iout <5A, 3.3V<Vin<10V 1.5 1.485 1.515 1.47 1.53 Vv 1.47 1.53 1.455 1.545 2.5V Version Output Voltage (Note 2) AS2850-2.5V, 0 <Iout <5A, 4.0V<Vin<10V 2.5 2.475 2.525 2.45 2.55 Vv 2.45 2.55 2.425 2.575 3.3V Version Output Voltage (Note 2) AS2850-3.3V, 0 <Iout <5A, 4.8V<Vin<10V 3.3 3.267 3.333 3.234 3.366 Vv 3.234 3.366 3.069 3.399 5.0V Version Output Voltage (Note 2) AS2850-5.0V, 0 <Tout <5A, 6.5VSVin<12V 5 4.950 5.050 49 5.1 Vv 4.900 5.100 4.65 5.15 All Voltage Options Reference Voltage (Vref) Vins 7V, P< Pax 1.250 1.225 1.270 1.225 1.270 Vv 1.5V< (Vin -Vout)<5.75V, 10mA<Iout<5A Min. Load Current (Note 3) 1.5V< (Vin Vout)<5.75V 5 10 10 Vv Line Regulation (AVref(Vin)) 2.75V<Vin <7V, Iout=10mA, Tj=25C 0.005 0.2 0.2 % (Note 3) Vin <7V, Iout=OmA, TI=25C (Note 2) 0.005 0.2 0.2 Load Regulation(AVref(Iout)) 10mA<Iout <5A, (Vin-Vout)=3V, Tj=25C (Note 3) 0.05 0.3 0.3 % O<Iout <5A, Vin=7V, Tj=25C (Note 2) 0.05 0.3 0.3 Dropout Voltage AVREF=1% Iout = 5A (Note 3) 11 1.2 1.2 Tout < 5A (Note 2) Current Limit Vin=7V 6 5.2 5.2 A Tout(MAX) - 1.4V < (Vin - Vout) (Note3) (Long Term Stability Ta=125C, 1000 Hrs. 0.3 1 1 % (Note 2) Thermal Regulation Ta=25C, 20 ms pulse 0.01 0.020 0.020 %IW (AVout(Pwr)) Temperature Stability 0.25 % (AVout(T)) Output Noise, RMS 10Hz to 10khz =TA=25C 0.003 % Vo Thermal Resistance TO-220 Junction to Tab 3.0 3.0 C/W Junction to Ambient 60 60 DD Package Junction to Tab 3.0 3.0 Junction to Ambient 60 60 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 Version Only Note 3: Adjustable Version Only Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94566 Tel: (925) 417-1391 Fax: (925) 417-1390 Rev. 12/3/98APPLICATION HINTS The ALPHA Semiconductor AS2850 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. Stability The output capacitor is part of the regulators frequency compensation system. Either a 22uF aluminum electrolytic capacitor or a 10uUF 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 ADJ pin and ground. When ADJ pin bypassing is used, the value of the output capacitor required increases to its Maximum (220uF for an aluminum electrolytic capacitor, or 47uF for a solid tantalum capacitor). If the ADJ pin is not bypass, the value of the output capacitor can be lowered to 10uF for an electrolytic aluminum capacitor or 4.7HF for a solid tantalum capacitor. However the value of the ADJ-bypass capacitor should be chosen with respect to the following equation: Where C= value of the capacitor in Farads (select an equal or larger standard value), Fa =ripple frequency in Hz, R, =value of resistor R; in Ohms. If an ADJ-bypass capacitor is use, the amplitude of the output ripple will be independent of the output voltage. If an ADJ- bypass capacitor is not used, the output ripple will be proportional to the ratio of the output voltage to the reference voltage: M = Vour/ Vrer Where M~ = multiplier for the ripple seen when the ADJ pin is optimally bypassed. Vrer = Reference Voltage AS2850 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. Thermal Consideration Although the AS2850 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: Vin = TV, Vout = 5V, lour = 5A, Ta = 90C, OcasE= 1C/W (no external heat sink, no wind) Power dissipation under these conditions Pp = (Vin Vour) * Tour = 15W Junction Temperature Ty = Ta + Pp * (Ocaset O1c) For the Control Section Ty = 90C + 15W*(1C/W + 0.6C/W) = 114C 114C < Tyuncrion max for the control section. For the Power Section Ty = 90C + 15W*(1C/W + 1.6C/W) = 129C 129C < Tyuncrion max for the power transistor. In both case reliable operation is insured by adequate junction temperature. Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94566 Tel: (925) 417-1391 Fax: (925) 417-1390 Rev.12/3/98Basic Adjustable Regulator Vv ALPHA IN AS82850 our ADJ = I ARs Al Ry Vour= Vrze* (1 + R/R) + Tap; * RB, Fig.2 Basic Adjustable Regulator Output Voltage Consider Figure 2. The resistance R, generates a constant current flow, normally the specified load current of 10mA. This current will go through the resistance R to set the overall output voltage. The current I,p; is very small and constant. Therefore its contribution to the overall output voltage is very small and can generally be ignored Ry Parasitic Line ALPHA RRA Your AS2850 VIN Connect R , to Case of Regulator ADI Ri > < > R S$ SL < Connect R. , to Load Fig.3 Basic Adjustable Regulator AS2850 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 R; resistance from the resistor divider to the case, and not to the load. For the same reason, it is best to connect the resistor R to the Negative side of the load. Vour 3.3V Cl Basic Fixed Regulator ALPHA AS2850 Output Voltage The fixed voltage LDO voltage regulators are simple to use regulators since the Vour 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. Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94566 Tel: (925) 417-1391 Fax: (925) 417-1390 Rev.12/4/98AS2850 Note A: V4, in = (Intended V 45.) +CV ppopout (MAX) ) TYPICAL APPLICATIONS Vv, | ALPHA IN IN AS2850 OUT | ALPHA Vy Ves IN| AS2850 or ADJ 1 -_ Ri LOAD Vout = Vrer(1 + Ro) + Taps Ro Re L R Fig 5. Typical Adjustable Regulator Fig.4 5A Current Output Regulator (Note A) SV T_ IN ie i ouT 2 V ALPHA our . 5v ADI Ri ADI 1219 1219 , 1% =k 1% aR 10uF Looe = 150uF T : : 1 TIL ik *C1 improves ripple rejection. X . Output) 2N3904 should be ~ R1 at ripple frequency. Ry +L C1 $650 3652. T 10uF* 1k lo 1% = Note A: V yy qn) = (Intended V our) +(V propouraaxy ) Fig.6 Improving Ripple Rejection Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94566 Tel: (925) 417-1391 Fax: (925) 417-1390 Fig.7 5V Regulator with Shutdown Rev.12/4/98AS2850 TYPICAL CHARACTERISTICS 0.10 0.05 0.05 -0.10 OUTPUT VOLTAGE DEVIATION (%) 0.15 0.20 90 80 70 60 50 40 30 20 ADJUSTMENT PIN CURRENT (yA) TYPICAL PERFORMANCE CHARACTERISTICS LOAD REGULATION SHORT CIRCUIT CURRENT 10 9 =z 8 57 5 3 = 3 2 2 1 leu Loan 50-25 0 2 50 75 100 125 150 5 1 15 20 25 30 35 TEMPERATURE (C) INPUT/OUTPUT DIFFERENTIAL (V) ADJUSTMENT PIN CURRENT DROPOUT VOLTAGE nm * INDICATES GUARANTEED TEST POINT -65C < T,s 150C OCs T= 125C MINIMUM INPUT/OUTPUT DIFFERENTIAL (V) 0 50-2 0 2% 50 75 100 125 150 09 1 2 3 4 5 6 TEMPERATURE (C) OUTPUT CURRENT (A) TEMPERATURE STABILITY 1.270 1.260 a V 1.250 REFERENCE VOLTAGE 1.240 1.230 MINIMUM OPERATING CURRENT 10 9 8 7 T= 150C T= 25C MINIMUM OPERATING CURRENT (mA) nm wo _ on = 55C -50 25 0 2 SO 75 TEMPERATURE (C) 100 125 150 5 10. 15 20. 25 INPUT/QUTPUT DIFFERENTIAL (V) 30.35 Alpha Semiconductor Inc. 1031 Serpentine Lane. Pleasanton, CA 94566 Tel: (925) 417-1391 Fax: (925) 417-1390 Rev.12/4/98