CS5203 -1 CS5203-1 3A Adjustable Linear Regulator Description The CS5203-1 linear regulator provides 3A at adjustable output voltages with an accuracy of ±1.5%. The device uses two external resistors to set the output voltage within a 1.25V to 5.5V 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. Features The circuit is designed to operate with dropout voltage less than 1.4V at 3A output current. Device protection includes overcurrent and thermal shutdown. The CS5203-1 is pin compatible with the LT1085 family of linear regulators but has lower dropout voltage. The regulator is available in TO-220 and surface mount D2 packages. ■ Output Current to 3A ■ Output Accuracy to ± 1.5% Over Temperature ■ Dropout Voltage (typical) 1.2V @ 3A ■ Fast Transient Response ■ Fault Protection Current Limit Thermal Shutdown Application Diagram Package Options 5.0V 3L TO-220 3L D2PAK Tab (VOUT) Tab (VOUT) VOUT VIN CS5203-1 3.3V @ 3A 1 124W 1% Adj 10mF 5V 22mF 5V 0.1mF 5V 200W 1% 1 CS5203 -1 1 Adj 2 VOUT (Tab) 3 VIN Consult factory for fixed output voltage versions. 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. 9/17/97 1 A ¨ Company CS5203 -1 Absolute Maximum Ratings Supply Voltage, VIN .....................................................................................................................................................................7V Operating Temperature Range................................................................................................................................-40¡C to 70¡C Junction Temperature ............................................................................................................................................................150¡C Storage Temperature Range ..................................................................................................................................-60¡C to 150¡C ESD Damage Threshold............................................................................................................................................................2kV 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, VOUT + VDROPOUT < VIN < 7V, 0¡C ² TA ² 70¡C, TJ ² +150¡C, unless otherwise specified, Ifull load = 3A. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 1.235 (-1.5%) 1.254 1.273 (+1.5%) V ■ Adjustable Output Voltage (CS5203-1) Reference Voltage (Notes 1 and 2) VINÐVOUT=1.5V; VAdj = 0V 10mA²IOUT²3A Line Regulation 2V²VINÐVOUT²5.75V; IOUT=10mA 0.02 0.20 % Load Regulation (Notes 1 and 2) VINÐVOUT=2V; 10mA²IOUT²3A 0.04 0.4 % Dropout Voltage (Note 3) IOUT=3A 1.15 1.40 V Current Limit VINÐVOUT=3V; TJ ³ 25¡C 0.6 2.0 mA 50 100 µA 0.020 3.1 Minimum Load Current (Note 4) VIN=7V; Vadj=0 VINÐVOUT=3V; IOUT=10mA Adjust Pin Current 4.6 Thermal Regulation (Note 5) 30ms pulse; TA=25¡C 0.002 Ripple Rejection (Note 5) f=120Hz; IOUT=3A; VINÐVOUT=3V; VRIPPLE=1VPP 80 Thermal Shutdown (Note 6) 150 180 Thermal Shutdown Hysteresis (Note 6) A %/W dB 210 ¡C 25 ¡C 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 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. Note 4: Minimum load current is defined as the minimum output current required to maintain regulation. The reference resistor in the output divider is usually sized to fulfill the minimum load current requirement. Note5: Guaranteed by design, not 100% functionally tested in production. Note 6: Guaranteed by design, not 100% parametrically tested in production. However, every part is subject to functional testing for thermal shutdown. Package Pin Description PACKAGE PIN # PIN SYMBOL FUNCTION D2PAK TO-220 1 1 Adj Adjust pin (low side of the internal reference). 2 2 VOUT Regulated output voltage (case) 3 3 VIN Input voltage. 2 CS5203 -1 Block Diagram V OUT V IN Output Current Limit Thermal Shutdown - + Error Amplifier Bandgap Reference Adj Typical Performance Characteristics 1.20 +0.3 Reference Voltage Deviation (%) 1.15 Dropout Voltage (V) 1.10 1.05 TCASE 1.00 = 0°C 0.95 0.90 TCASE = 25°C TCASE = 125°C 0.85 +0.2 +0.1 0 -0.1 -0.2 0.80 -0.3 0.75 0.00 0.30 0.60 0.90 1.20 1.50 1.80 2.10 Output Current (A) 0 2.40 2.70 3.00 30 60 90 120 TJ (°C) Dropout Voltage vs. Output Current Bandgap Reference Voltage Deviation vs. Temperature 90.00 0.65 Minimum Load Current (mA) Ripple Rejection (dB) 80.00 70.00 60.00 50.00 40.00 30.00 0.60 TCASE = 0°C 0.55 TCASE = 25°C TCASE = 125°C 0.50 0.45 20.00 10.00 0.40 101 102 103 104 105 1.00 106 Frequency (Hz) 2.00 3.00 4.00 5.00 VIN – VOUT (V) Minimum Load Current vs VIN-VOUT Ripple Rejection vs. Frequency 3 6.00 7.00 8.00 CS5203 -1 Typical Performance Characteristics: continued 68.00 75 TCASE = 125°C Adjust Pin Current (mA) 65 IAdj (mA) Adjust Pin Current 66.00 55 64.00 62.00 60.00 TCASE = 25°C 58.00 56.00 54.00 1.00 45 0 30 60 120 90 TA(°C) TCASE = 0°C 2.00 3.00 4.00 5.00 6.00 7.00 8.00 VIN - VOUT (V) Adjust Pin Current vs. VIN -VOUT Adjust Pin Current vs. Temperature 70.00 68.50 +200 Adjust Pin Current (mA) 67.00 65.50 DVOUT 0 (mV) 64.00 -200 62.50 61.00 -200 59.50 58.00 VIN = 5V VOUT = 3.3V CIN = 100mF COUT = 10mF Tantalum 3 I(A) 56.50 1 55.00 0.0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 0 3.0 0 IOUT (A) Adjust Pin Current vs Output Current Transient Response 6.00 5.00 ISC(A) 4.00 3.00 2.00 1.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 VIN-VOUT (V) Short Circuit Current vs VIN-VOUT 4 5 Time (ms) 10 ages in excess of 7V. The main considerations in such a design are power-up and short circuit capability. The CS5203-1 linear regulator provides adjustable voltages at currents up to 3A. The regulator is protected against overcurrent conditions and includes thermal shutdown. The CS5203-1 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. In most applications, ramp-up of the power supply to VIN is fairly slow, typically on the order of several tens of milliseconds, while the regulator responds in less than one microsecond. In this case, the linear regulator begins charging the load as soon as the VIN to VOUT differential is large enough that the pass transistor conducts current. The load at this point is essentially at ground, and the supply voltage is on the order of several hundred millivolts, with the result that the pass transistor is in dropout. As the supply to VIN increases, the pass transistor will remain in dropout, and current is passed to the load until VOUT reaches the point at which the IC is in regulation. Further increase in the supply voltage brings the pass transistor out of dropout. The result is that the output voltage follows the power supply ramp-up, staying in dropout until the regulation point is reached. In this manner, any output voltage may be regulated. There is no theoretical limit to the regulated voltage as long as the VIN to VOUT differential of 7V is not exceeded. Adjustable Operation The CS5203-1 has an output voltage range of 1.25V to 5.5V. 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: ( However, the possibility of destroying the IC in a short circuit condition is very real for this type of design. Short circuit conditions will result in the immediate operation of the pass transistor outside of its safe operating area. Overvoltage stresses will then cause destruction of the pass transistor before overcurrent or thermal shutdown circuitry can become active. Additional circuitry may be required to clamp the VIN to VOUT differential to less than 7V if failsafe operation is required. One possible clamp circuit is illustrated in figure 2; however, the design of clamp circuitry must be done on an application by application basis. Care must be taken to ensure the clamp actually protects the design. Components used in the clamp design must be able to withstand the short circuit condition indefinitely while protecting the IC. ) 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 2mA. R1 and R2 should be the same type, e.g. metal film for best tracking over temperature. While not required, a bypass capacitor between the adjust pin and ground will improve ripple rejection and transient response. A 0.1µF tantalum capacitor is recommended for Òfirst cutÓ design. Type and value may then be varied to optimize performance vs. price. EXTERNAL SUPPLY VIN VIN VOUT VIN C1 VOUT VOUT VAdj CS5203-1 VREF R1 C2 VOUT Adj IAdj CAdj R2 Figure 2. Short Circuit Protection Circuit for High Voltage Application. Stability Considerations Figure 1. Resistor divider scheme. 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 The 5203-1 linear regulator has an absolute maximum specification of 7V for the voltage difference between VIN and VOUT. However, the IC may be used to regulate volt- 5 CS5203 -1 Applications Information CS5203 -1 Applications Information: continued electrolytic capacitor is best, since a film or ceramic capacitor 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 manufacturersÕ data sheet provides this information. A 22µF tantalum capacitor will work for most applications, but with high current regulators such as the CS5203-1 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: Output Voltage Sensing Since the CS5203-1 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. For the adjustable regulator, the best load regulation occurs when R1 is connected directly to the output pin of the regulator as shown in Figure 4. 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 ÆV = ÆI ´ ESR ) RC = conductor parasitic resistance 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. VIN RC VOUT VIN conductor parasitic resistance CS5203-1 RLOAD R1 Adj 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 CS5203-1 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 Figure 3 is recommended. IN4002 VIN C1 Figure 4. Grounding scheme for the adjustable output regulator to minimize parasitic resistance effects. Calculating Power Dissipation and Heat Sink Requirements The CS5203-1 linear regulator includes thermal shutdown and current limit 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. (optional) VOUT VIN R2 VOUT CS-5203-1 R1 The case is connected to VOUT on the CS5203-1 , and electrical isolation may be required for some applications. Thermal compound should always be used with high current regulators such as these. C2 Adj CAdj The thermal characteristics of an IC depend on the following four factors: R2 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) Figure 3. Protection diode scheme for large output capacitors. These four are related by the equation 6 TJ = TA + PD ´ RQJA (1) 3. Thermal Resistance of the Heat Sink to the ambient air, RQSA (¡C/W) 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. These are connected by the equation: RQJA = RQJC + RQCS + RQSA The maximum power dissipation for a regulator is: (3) The value for RQJA is calculated using equation (3) and the result can be substituted in equation (1). PD(max)={VIN(max)ÐVOUT(min)}IOUT(max)+VIN(max)IQ The value for RQJC is 3.5û C/W as a single figure for a given package type based on an average die size. For a high current regulator such as the CS5203-1 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 (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 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. 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. 1. Thermal Resistance of the junction to case, RQJC (¡C/W) 2. Thermal Resistance of the case to Heat Sink, RQCS (¡C/W) 7 CS5203 -1 Applications Information: continued CS5203 -1 Package Specification PACKAGE DIMENSIONS IN mm (INCHES) PACKAGE THERMAL DATA 3 Lead D2PAK (DP) 10.31 (.406) 10.05 (.396) 3L TO-220 3.5 50 Thermal Data RQJC typ RQJA typ 1.40 (.055) 1.14 (.045) 1.68 (.066) 1.40 (.055) 3L D2PAK 3.5 10 - 50* ûC/W ûC/W *Depending on thermal properties of substrate. RQJA = RQJC + RQCA 8.53 (.336) 8.28 (.326) 15.75 (.620) 14.73 (.580) 2.74(.108) 2.49(.098) 1.40 (.055) 1.14 (.045) 2.79 (.110) 2.29 (.090) 0.91 (.036) 0.66 (.026) 2.54 (.100) REF 4.57 (.180) 4.31 (.170) .254 (.010) REF 0.10 (.004) 0.00 (.000) 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 CS5203-1GT3 CS5203-1GDP3 CS5203-1GDPR3 Rev. 9/17/97 Type 3A, adj. output 3A, adj. output 3A, adj. output Description 3 L TO-220 Straight 3 L D2PAK 3 L 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. 8 © 1999 Cherry Semiconductor Corporation