CS5205A-1 CS5205A-1 5A Adjustable Linear Regulator Description The CS5205A-1 linear regulator provides 5A at an adjustable voltage with an accuracy of ±1%. Two external resistors are used to set the output voltage within a 1.25V to 13V range. The regulator is intended for use as a post regulator and microprocessor supply. The fast loop response and low dropout voltage make this regulator ideal for applications where low voltage operation and good transient response are important. The circuit is designed to operate with dropout voltages as low as 1V Features depending on the output current level. The maximum quiescent current is only 10mA at full load. ■ Output Current to 5A The regulator is fully protected against overload conditions with protection circuitry for Safe Operating Area (SOA), overcurrent and thermal shutdown. ■ Dropout Voltage 1.15V @ 5A The CS5205A-1 is pin compatible with the LT1084 family of linear regulators but has lower dropout voltage. ■ Output Trimmed to +/- 1% ■ Fast Transient Response ■ Fault Protection Circuitry Thermal Shutdown Overcurrent Protection Safe Area Protection The regulator is available in TO-220 and surface mount D2 packages. Package Options Block Diagram 3L TO-220 3L D2PAK Tab (VOUT) V OUT V IN 1 1 2 3 Output Current Limit Thermal Shutdown - + Adj VOUT VIN 1 Error Amplifier Bandgap Adj Cherry Semiconductor Corporation 2000 South County Trail, East Greenwich, RI 02818 Tel: (401)885-3600 Fax: (401)885-5786 Email: [email protected] Web Site: www.cherry-semi.com Rev. 7/8/97 1 A ¨ Company CS5205A-1 Absolute Maximum Ratings Supply Voltage, VCC .....................................................................................................................................................................17V Operating Temperature Range ..................................................................................................................................-40¡C to 70¡C Junction Temperature ...............................................................................................................................................................150¡C Storage Temperature Range .....................................................................................................................................-60¡C to 150¡C Lead Temperature Soldering Wave Solder (through hole styles only) ........................................................................................10 sec. max, 260¡C peak Reflow (SMD styles only) .........................................................................................60 sec. max above 183¡C, 230¡C peak Electrical Characteristics: CIN = 10µF, COUT = 22µF Tantalum, VIN Ð VOUT=3V, VIN ² 15V, 0¡C ² TA ² 70¡C, TJ ² +150¡C, unless otherwise specified, Ifull load = 5A. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 1.241 (-1%) 1.254 1.266 (+1%) V ■ Adjustable Output Voltage Reference Voltage (Notes 1 and 2) VINÐVOUT=1.5V; VAdj = 0V 10mA²IOUT²5A Line Regulation 1.5V²VINÐVOUT²6V; IOUT=10mA 0.04 0.20 % Load Regulation (Notes 1 and 2) VINÐVOUT=1.5V; 10mA²IOUT²5A 0.08 0.4 % Dropout Voltage (Note 3) IOUT=5A; TJ ³ 25¡C 1.15 1.25 V Current Limit VINÐVOUT=3V; TJ ³ 25¡C VINÐVOUT=9V Minimum Load Current VINÐVOUT=7V 5.5 Adjust Pin Current Adjust Pin Current Change 1.5V²VINÐVOUT²4V; 10mA²IOUT²5A 8.5 1.0 A A 1.2 6 mA 50 100 µA 0.2 5.0 µA Thermal Regulation 30ms pulse; TA=25¡C 0.003 %W Ripple Rejection f=120Hz; CAdj=25µF; IOUT=5A 82 dB 0.5 % 0.003 %VOUT 180 ¡C 25 ¡C Temperature Stability 10Hz²f²10kHz; TA=25¡C RMS Output Noise Thermal Shutdown 150 Thermal Shutdown Hysteresis Note 1: Load regulation and output voltage are measured at a constant junction temperature by low duty cycle pulse testing. Changes in output voltage due to thermal gradients or temperature changes must be taken into account separately. Note 2: Specifications apply for an external Kelvin sense connection at a point on the output pin 1/4Ó from the bottom of the package. Note 3: Dropout voltage is a measurement of the minimum input/output differential at full load. Package Pin Description PACKAGE PIN # D2PAK 1 2 3 3L TO-220 1 2 3 PIN SYMBOL Adj VOUT VIN FUNCTION Adjust pin (low side of the internal reference). Regulated output voltage (case). Input voltage. 2 CS5205A-1 Typical Performance Characteristics 0.10 1.20 0.08 Dropout Voltage (V) 1.15 Output Voltage Deviation (%) 1.25 TCASE = 0°C 1.10 1.05 1.00 0.95 TCASE = 125°C 0.90 TCASE = 25°C 0.85 0.80 0.75 0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 -0.10 0.70 -0.12 0 1 2 3 Output Current (A) 4 5 0 20 10 30 40 50 60 70 80 90 100 110 120 130 TJ (°C) Reference Voltage vs. Temperature Dropout Voltage vs. Output Current 2.500 0.200 Minimum Load Current (mA) 0.175 Output Voltage Deviation (%) 0.06 0.150 0.125 0.100 TCASE = 25°C 0.075 TCASE = 125°C 0.050 2.175 1.850 TCASE = 0°C 1.525 1.200 TCASE = 125°C 0.875 TCASE = 25°C 0.025 TCASE = 0°C 0.550 0.000 0 1 2 3 4 1 5 2 Output Current (A) Load Regulation vs. Output Current Minimum Load Current 100.0 Ripple Rejection (dB) 90.0 80.0 70.0 60.0 50.0 TCASE = 25°C IOUT = 5A (VIN Ð VOUT) = 3V VRIPPLE = 1.6VPP CAdj = 25mF 40.0 30.0 20.0 10.0 0.0 101 102 103 104 105 Frequency (Hz) Ripple Rejection vs. Frequency 3 3 4 5 VIN – VOUT (V) 6 7 8 9 CS5205A-1 Applications Information tor with almost zero ESR, can cause instability. The aluminum electrolytic capacitor is the least expensive solution. However, when the circuit operates at low temperatures, both the value and ESR of the capacitor will vary considerably. The capacitor manufacturers data sheet provides this information. A 22µF tantalum capacitor will work for most applications, but with high current regulators such as the CS5205A-1 the transient response and stability improve with higher values of capacitor. The majority of applications for this regulator involve large changes in load current so the output capacitor must supply the instantaneous load current. The ESR of the output capacitor causes an immediate drop in output voltage given by: The CS5205A-1 linear regulator provides an adjustable voltage at currents up to 5A. The regulator is protected against short circuit, and include thermal shutdown and safe area protection (SOA) circuitry. The SOA protection circuitry decreases the maximum available output current as the input-output differential voltage increases. The CS5205A-1 has a composite PNP-NPN output transistor and requires an output capacitor for stability. A detailed procedure for selecting this capacitor is included in the Stability Considerations section. Adjustable Operation The adjustable regulator (CS5205A-1) has an output voltage range of 1.25V to 13V. An external resistor divider sets the output voltage as shown in Figure 1. The regulator maintains a fixed 1.25V (typical) reference between the output pin and the adjust pin. A resistor divider network R1 and R2 causes a fixed current to flow to ground. This current creates a voltage across R2 that adds to the 1.25V across R1 and sets the overall output voltage. The adjust pin current (typically 50µA) also flows through R2 and adds a small error that should be taken into account if precise adjustment of VOUT is necessary. The output voltage is set according to the formula: VOUT ( ÆV = ÆI ´ ESR For microprocessor applications it is customary to use an output capacitor network consisting of several tantalum and ceramic capacitors in parallel. This reduces the overall ESR and reduces the instantaneous output voltage drop under load transient conditions. The output capacitor network should be as close as possible to the load for the best results. Protection Diodes When large external capacitors are used with a linear regulator it is sometimes necessary to add protection diodes. If the input voltage of the regulator gets shorted, the output capacitor will discharge into the output of the regulator. The discharge current depends on the value of the capacitor, the output voltage and the rate at which VIN drops. In the CS5205A-1 linear regulator, the discharge path is through a large junction and protection diodes are not usually needed. If the regulator is used with large values of output capacitance and the input voltage is instantaneously shorted to ground, damage can occur. In this case, a diode connected as shown in Figure2 is recommended. ) = VREF ´ R1 + R2 + IAdj ´ R2 R1 The term IAdj ´ R2 represents the error added by the adjust pin current. R1 is chosen so that the minimum load current is at least 10mA. R1 and R2 should be the same type, e.g. metal film for best tracking over temperature. The adjust pin is bypassed to improve the transient response and ripple rejection of the regulator. VIN VOUT VIN C1 IN4002 VOUT VIN CS5205A-1 R1 C1 C2 VOUT VIN VREF (optional) VOUT CS5205A-1 Adj R1 C2 Adj IAdj CAdj R2 CAdj Figure 1. Resistor divider scheme for the adjustable version. R2 Figure 2. Protection diode scheme for adjustable output regulator. Stability Considerations Output Voltage Sensing The output or compensation capacitor helps determine three main characteristics of a linear regulator: start-up delay, load transient response and loop stability. The capacitor value and type is based on cost, availability, size and temperature constraints. A tantalum or aluminum electrolytic capacitor is best, since a film or ceramic capaci- Since the CS5205A-1 is a three terminal regulator, it is not possible to provide true remote load sensing. Load regulation is limited by the resistance of the conductors connecting the regulator to the load. 4 Best load regulation occurs when R1 is connected directly to the output pin of the regulator as shown in Figure 3. If R1 is connected to the load, RC is multiplied by the divider ratio and the effective resistance between the regulator and the load becomes ( RC ´ R1 + R2 R1 The maximum power dissipation for a regulator is: PD(max)={VIN(max)ÐVOUT(min)}IOUT(max)+VIN(max)IQ (2) where VIN(max) is the maximum input voltage, ) VOUT(min) is the minimum output voltage, IOUT(max) is the maximum output current, for the application RC = conductor parasitic resistance IQ is the maximum quiescent current at IOUT(max). A heat sink effectively increases the surface area of the package to improve the flow of heat away from the IC and into the surrounding air. RC VOUT VIN Each material in the heat flow path between the IC and the outside environment has a thermal resistance. Like series electrical resistances, these resistances are summed to determine RQJA, the total thermal resistance between the junction and the surrounding air. conductor parasitic resistance CS5205A-1 RLOAD R1 1. Thermal Resistance of the junction to case, RQJC (¡C/W) Adj 2. Thermal Resistance of the case to Heat Sink, RQCS (¡C/W) R2 3. Thermal Resistance of the Heat Sink to the ambient air, RQSA (¡C/W) These are connected by the equation: RQJA = RQJC + RQCS + RQSA Figure 3. Grounding scheme for the adjustable output regulator to minimize parasitics. The value for RQJA is calculated using equation (3) and the result can be substituted in equation (1). The value for RQJC is normally quoted as a single figure for a given package type based on an average die size. For a high current regulator such as the CS5205A-1 the majority of the heat is generated in the power transistor section. The value for RQSA depends on the heat sink type, while RQCS depends on factors such as package type, heat sink interface (is an insulator and thermal grease used?), and the contact area between the heat sink and the package. Once these calculations are complete, the maximum permissible value of RQJA can be calculated and the proper heat sink selected. For further discussion on heat sink selection, see application note ÒThermal Management for Linear Regulators.Ó Calculating Power Dissipation and Heat Sink Requirements The CS5205A-1 linear regulator includes thermal shutdown and safe operating area circuitry to protect the device. High power regulators such as these usually operate at high junction temperatures so it is important to calculate the power dissipation and junction temperatures accurately to ensure that an adequate heat sink is used. The case is connected to VOUT on the CS5205A-1, electrical isolation may be required for some applications. Thermal compound should always be used with high current regulators such as these. The thermal characteristics of an IC depend on the following four factors: 1. Maximum Ambient Temperature TA (¡C) 2. Power dissipation PD (Watts) 3. Maximum junction temperature TJ (¡C) 4. Thermal resistance junction to ambient RQJA (C/W) These four are related by the equation TJ = TA + PD ´ RQJA (3) (1) The maximum ambient temperature and the power dissipation are determined by the design while the maximum junction temperature and the thermal resistance depend on the manufacturer and the package type. 5 CS5205A-1 Applications Information: continued CS5205A-1 Package Specification PACKAGE DIMENSIONS IN mm(INCHES) PACKAGE THERMAL DATA Thermal Data RQJC RQJA 3L TO-220 1.6 50 typ typ 3L D2PAK 1.6 10 - 50* ûC/W ûC/W *Depending on thermal properties of substrate. RQJA = RQJC + RQCA 3 Lead TO-220 (T) Straight 3 Lead D2PAK (DP) 10.31 (.406) 10.05 (.396) 4.83 (.190) 4.06 (.160) 10.54 (.415) 9.78 (.385) 6.55 (.258) 5.94 (.234) 1.40 (.055) 1.14 (.045) 1.40 (.055) 1.14 (.045) 20° typ 3.96 (.156) 3.71 (.146) 2.87 (.113) 2.62 (.103) 1.88 (.066) 1.40 (.055) 6° 4° 8.53 (.336) 8.28 (.326) B 14.99 (.590) 14.22 (.560) 15.75 (.620) 14.73 (.580) 2.74(.108) 2.49(.098) EÐPIN 6° 4° 0.10(.004) 0.00(.000) 1.40 (.055) 1.14 (.045) 1.52 (.060) 1.14 (.045) 14.22 (.560) 13.72 (.540) 2.79 (.110) 2.29 (.090) 0.91 (.036) 0.66 (.026) 6.17 (.243) REF 2.54 (.100) REF A 3° 0° 1.40 (.055) 1.14 (.045) 6° 4° (Both Sides) B 4.57 (.180) 4.31 (.170) 1.02 (.040) 0.63 (.025) C 0.56 (.022) 0.38 (.014) 2.79 (.110) 2.29 (.090) 5.33 (.210) 4.83 (.190) 2.92 (.115) 2.29 (.090) Ordering Information Part Number Type CS5205A-1GT3 5A, adj. output CS5205A-1GDP3 5A, adj. output CS5205A-1GDPR3 5A, adj. output Rev. 7/8/97 Description 3L TO-220 Straight 3L D2PAK 3L D2PAK (tape & reel) Cherry Semiconductor Corporation reserves the right to make changes to the specifications without notice. Please contact Cherry Semiconductor Corporation for the latest available information. 6 © 1999 Cherry Semiconductor Corporation