CS5207-1 CS5207-1 7A Adjustable Linear Regulator Description The CS5207-1 linear regulator provides 7A at adjustable voltages with an accuracy of ±1.5%. Two external resistors are used to set the output voltage within a 1.25V to 13V range. The regulator is intended for use as 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. Features with dropout voltages as low as 1V depending on the output current level. The maximum quiescent current is only 10mA at full load. The regulator is fully protected against overload conditions with protection circuitry for Safe Operating Area (SOA), overcurrent and thermal shutdown. The regulator is available in a TO-220 package. A 3.3V, fixed version is also available. Please consult factory for more information. The circuit is designed to operate Block Diagram ■ Output Current to 7A ■ Output Trimmed to ±1.5% ■ Dropout Voltage 1.4V @ 7A ■ Fast Transient Response ■ Fault Protection Circuitry Thermal Shutdown Overcurrent Protection Safe Area Protection ■ 3.3V Fixed Version Available Package Options 3L TO-220 Tab (VOUT) V OUT V IN Output Current Limit Thermal Shutdown - + 1 2 3 Error Amplifier Adj VOUT VIN 1 Bandgap Adj A 3.3V fixed version is also available. *Consult factory. 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 CS5207 -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 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 = 7A. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 1.235 (-1.5%) 1.254 1.272 (+1.5%) V ■ Adjustable Output Voltage Reference Voltage (Notes 1 and 2) VINÐVOUT=1.6V; VAdj = 0V 10mA²IOUT²7A Line Regulation 1.6V²VINÐVOUT²6V; IOUT=10mA 0.04 0.20 % Load Regulation (Notes 1 and 2) VINÐVOUT=1.6V; 10mA²IOUT²7A 0.13 0.5 % Dropout Voltage (Note 3) IOUT=7A 1.4 1.55 V Current Limit VINÐVOUT=3V; TJ ³ 25¡C VINÐVOUT=9V Minimum Load Current VINÐVOUT=7V 7.1 Adjust Pin Current 8.5 1.0 A A 1.2 6 mA 50 100 µA 5.0 µA Adjust Pin Current Change 1.6V²VINÐVOUT²4V; 10mA²IOUT²7A 0.2 Thermal Regulation 30ms pulse; TA=25¡C 0.003 %W Ripple Rejection f=120Hz; CAdj=25µF; IOUT=7A 80 dB 0.5 % 10Hz²f²10kHz; TA=25¡C 0.003 %VOUT 180 ¡C 25 ¡C Temperature Stability 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 # PIN SYMBOL FUNCTION 3L TO-220 1 Adj Adjust pin (low side of the internal reference). 2 VOUT Regulated output voltage (case). 3 VIN Input voltage. 2 CS5207 -1 1.55 1.50 1.45 1.40 1.35 1.30 1.25 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 TCASE = 25°C 0.80 0.75 0.70 0 1 0.10 0.08 Output Voltage Deviation (%) Dropout Voltage (V) Typical Performance Characteristics TCASE = 0°C TCASE = 125°C 0.06 0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 -0.10 -0.12 2 3 4 Output Current (A) 5 6 7 0 10 20 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) Output Voltage Deviation (%) 0.175 0.150 0.125 TCASE = 125°C 0.100 0.075 TCASE = 25°C 0.050 TCASE = 0°C 0.025 2.175 1.850 TCASE = 0°C 1.525 1.200 TCASE = 125°C 0.875 TCASE = 25°C 0.000 0.550 0 1 2 3 4 5 6 7 1 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 = 7A (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 CS5207 -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 CS5207-1 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 CS5207-1 linear regulator provides adjustable voltages at currents up to 7A. 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 CS5207-1 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 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: ( 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 CS5207-1 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 Figure 2 is recommended. ) VOUT = 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 VOUT IN4002 C1 CS5207-1 VREF VIN R1 C2 VOUT VIN C1 Adj (optional) VOUT CS5207-1 R1 IAdj CAdj C2 Adj R2 CAdj R2 Figure 1. Resistor divider scheme for the adjustable version. Figure 2. Protection diode scheme for adjustable output regulator. Stability Considerations 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- Output Voltage Sensing Since the CS5207-1 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 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. 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 RC = conductor parasitic resistance VIN(max) is the maximum input voltage, VOUT(min) is the minimum output voltage, VIN RC VOUT VIN IOUT(max) is the maximum output current, for the application conductor parasitic resistance CS5207-1 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. RLOAD R1 Adj 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. R2 1. Thermal Resistance of the junction to case, RQJC (¡C/W) 2. Thermal Resistance of the case to Heat Sink, RQCS (¡C/W) Figure 3. Grounding scheme for the adjustable output regulator to minimize parasitics. 3. Thermal Resistance of the Heat Sink to the ambient air, RQSA (¡C/W) Calculating Power Dissipation and Heat Sink Requirements These are connected by the equation: The CS5207-1 linear regulator includes thermal shutdown and safe operating area circuitry to protect the device. High power regulators such as this 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. RQJA = RQJC + RQCS + RQSA 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 CS5207-1 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 The case is connected to VOUT on the CS5207-1, 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) 5 CS5207 -1 Applications Information: continued CS5207 -1 Package Specification PACKAGE DIMENSIONS IN mm(INCHES) PACKAGE THERMAL DATA Thermal Data RQJC RQJA typ typ 3L TO-220 1.6 50 ûC/W ûC/W 3 Lead TO-220 (T) Straight 4.83 (.190) 4.06 (.160) 10.54 (.415) 9.78 (.385) 6.55 (.258) 5.94 (.234) 1.40 (.055) 1.14 (.045) 3.96 (.156) 3.71 (.146) 2.87 (.113) 2.62 (.103) 14.99 (.590) 14.22 (.560) 1.52 (.060) 1.14 (.045) 14.22 (.560) 13.72 (.540) 6.17 (.243) REF 1.40 (.055) 1.14 (.045) 1.02 (.040) 0.63 (.025) 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 CS5207-1GT3 CS5207-3GT3 Rev. 7/8/97 Type 7A, adj. output 7A, fixed output Description 3 L TO-220 Straight 3L TO-220 Straight 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