CS5201-1 CS5201-1 1A Adjustable Linear Regulator Description The CS5201-1 linear regulator provides 1A with an output voltage accuracy of ±1%. The device uses two external resistors to set the output voltage within a 1.25V to 5.5V range. This 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 voltages less than 1.2V at 1A output current. Device protection includes overcurrent and thermal shutdown. The CS5201 is pin compatible with the LT1086 family of linear regulators. The regulator is available in TO-220, surface mount D2, and SOT-223 packages. ■ Output Current to 1A ■ Output Accuracy to ±1% over Temperature ■ Dropout Voltage (typical) 1.0V @ 1A ■ Fast Transient Response ■ Fault Protection Current Limit Thermal Shutdown Package Options Application Diagram 5V 3L TO-220 3L D2PAK Tab (VOUT) Tab (VOUT) VOUT VIN 3.3V @ 1A CS5201-1 1 124W 1% Adj 3L SOT-223 Tab (VOUT) 1 22mF 5V 10mF 5V 0.1mF 5V Tant 200W 1% CS5201 -1 1 Adj 2 VOUT(Tab) 3 VIN 1 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. 2/16/98 1 A ¨ Company CS5201-1 Absolute Maximum Ratings Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7V 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 ESD Damage Threshold (Human Body Model) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kV 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 = 1A. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT Reference Voltage (Notes 1 and 2) VINÐVOUT=1.5V; VAdj = 0V 10mA²IOUT²1A 1.241 (-1%) 1.254 1.266 (+1%) V Line Regulation 1.5V²VINÐVOUT²5.75V; IOUT=10mA 0.02 0.20 % Load Regulation (Notes 1 and 2) VINÐVOUT=1.5V; 10mA²IOUT²1A 0.04 0.4 % Dropout Voltage (Note 3) IOUT=1A 1.0 1.2 V Current Limit VINÐVOUT=3V; TJ ³ 25¡C ■ Adjustable Output Voltage 1.1 3.1 A Minimum Load Current (Note 4) VIN=7V ; VAdj=0 0.6 2.0 mA Adjust Pin Current VINÐVOUT=3V; IOUT=10mA 50 100 µA Thermal Regulation (Note 5) 30ms pulse; TA=25¡C 0.002 0.020 %/W Ripple Rejection (Note 5) f=120Hz; IOUT=1A; VINÐVOUT=3V; VRIPPLE=1VPP 80 Thermal Shutdown (Note 6) 150 Thermal Shutdown Hysteresis (Note 6) 180 dB 210 25 ¡C ¡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: The minimum load current is the minimum current required to maintain regulation. Normally the current in the resistor divider used to set the output voltage is selected to meet the minimum load requirement. Note 5: Guaranteed by design, not 100% tested in production. Note 6: Thermal shutdown is 100% functionally tested in production. Package Pin Description PACKAGE PIN # PIN SYMBOL FUNCTION D2PAK TO-220 SOT-223 1 1 1 Adj Adjust pin (low side of the internal reference). 2 2 2 VOUT Regulated output voltage (case). 3 3 3 VIN Input voltage. 2 CS5201-1 Block Diagram V OUT V IN Output Current Limit Thermal Shutdown - + Error Amplifier Bandgap Reference Adj Typical Performance Characteristics 1.00 TCASE 0.10 = 0°C 0.08 Output Voltage Deviation (%) 0.95 TCASE = 25°C VDropout (V) 0.90 0.85 TCASE = 125°C 0.80 0.06 0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 -0.10 0.75 -0.12 0 200 400 600 800 1000 0 10 20 30 40 50 IOUT (mA) 70 80 90 100 110 120 130 Reference Voltage vs. Temperature Dropout Voltage vs. Output Current 0.100 0.65 Minimum Load Current (mA) Output Voltage Deviation (%) 60 TJ (°C) 0.075 0.050 TCASE = 125°C TCASE = 25°C 0.025 0.60 TCASE = 0°C 0.55 TCASE = 125°C TCASE = 25°C 0.50 0.45 CIN =COUT =22mF Tantalum TCASE = 0°C 0.000 0.40 0 1 Output Current (A) 2 1 Load Regulation vs. Output Current 2 3 4 VIN – VOUT (V) Minimum Load Current vs VIN-VOUT 3 5 6 7 CS5201-1 Typical Performance Characteristics: continued 70.0 85 IO = 10mA 75 Ripple Rejection (dB) Adjust Pin Current (mA) 65.0 60.0 55.0 50.0 65 55 TCASE = 25°C IOUT = 1A (VIN Ð VOUT) = 3V VRIPPLE = 1.0VPP CAdj = 0.1mF 45 35 45.0 25 15 40.0 0 10 20 30 40 50 60 70 80 101 90 100 110 120 130 102 103 Temperature (°C) 106 Ripple Rejection vs. Frequency 3.5 200 3.3 3.1 100 2.9 0 2.7 -100 VOUT = 3.3V COUT= CIN = 22mF Tantalum CAdj= 0.1mF -200 ISC(A) Voltage Deviation (mV) 105 Frequency (Hz) Adjust Pin Current vs. Temperature Load Step (mA) 104 2.5 2.3 1000 2.1 500 1.9 1.7 0 0 1 2 3 4 5 6 7 8 9 10 1.5 Time mS 1.0 1.5 2.0 2.5 3.0 3.5 4.0 VIN - VOUT (V) Transient Response Short Circuit Current vs. VIN - VOUT Applications Information The CS5201-1 linear regulator provides adjustable voltages at currents up to 1A. The regulator is protected against overcurrent conditions and includes thermal shutdown. The CS5201-1 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. 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 = 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 from the adjust pin to ground will improve ripple rejection and transient response. A 0.1µF tantalum capacitor is recommended for Òfirst cutÓ design. Type and value may be varied to obtain optimum performance vs. price. Adjustable Operation The CS5201-1 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 4 CS5201-1 Applications Information: continued EXTERNAL SUPPLY VIN VOUT VIN C1 CS5201-1 VOUT VREF R1 C2 Adj VIN VOUT IAdj CAdj VAdj R2 VOUT Figure 1. Resistor divider scheme. Short Circuit Protection The CS5201-1 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 voltages in excess of 7V. The main considerations in such a design are power-up and short circuit capability. 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. Figure 2. Short Circuit Protection Circuit for High Voltage Application. 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 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 CS5201 the transient response and stability improve with higher values of capacitance. 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: ÆV = ÆI ´ ESR 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. 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 CS5201-1 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. 5 CS5201-1 Applications Information: continued IN4002 VIN (optional) VOUT VIN C1 The thermal characteristics of an IC depend on the following four factors: 1. Maximum Ambient Temperature TA (¡C) VOUT 2. Power dissipation PD (Watts) CS5201-1 3. Maximum junction temperature TJ (¡C) R1 4. Thermal resistance junction to ambient RQJA (C/W) C2 Adj These four are related by the equation TJ = TA + PD ´ RQJA R2 CAdj 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. Figure 3. Protection diode for large output capacitors. The maximum power dissipation for a regulator is: Output Voltage Sensing PD(max)={VIN(max)ÐVOUT(min)}IOUT(max)+VIN(max)IQ Since the CS5201-1 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. ( 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. RC = conductor parasitic resistance VIN RC VOUT VIN CS5201-1 (2) where 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 (1) conductor parasitic resistance 1. Thermal Resistance of the junction to case, RQJC (¡C/W) 2. Thermal Resistance of the case to Heat Sink, RQCS (¡C/W) RLOAD R1 3. Thermal Resistance of the Heat Sink to the ambient air, RQSA (¡C/W) R2 These are connected by the equation: Adj RQJA = RQJC + RQCS + RQSA (3) The value for RQJA is calculated using equation (3) and the result can be substituted in equation (1). Figure 4. Grounding scheme for the adjustable output regulator to minimize parasitic resistance effects. The value for RQJC is 3.5ûC/W for a given package type based on an average die size. For a high current regulator such as the CS5201-1 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 CS5201-1 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. The case is connected to VOUT on the CS5201-1, and electrical isolation may be required for some applications. Thermal compound should always be used with high current regulators such as these. 6 CS5201-1 Package Specification PACKAGE THERMAL DATA PACKAGE DIMENSIONS IN mm (INCHES) 3 Lead TO-220 (T) Straight 4.83 (.190) 4.06 (.160) 10.54 (.415) 9.78 (.385) 6.55 (.258) 5.94 (.234) Thermal Data RQJC typ RQJA typ 3L D2PAK 3.5 10 - 50* 3L SOT-223 15 156 ûC/W ûC/W *Depending on thermal properties of substrate. RQJA = RQJC + RQCA 1.40 (.055) 1.14 (.045) 3.96 (.156) 3.71 (.146) 2.87 (.113) 2.62 (.103) 3 Lead SOT-223 (ST) 14.99 (.590) 14.22 (.560) 6.70 (.264) 6.30 (.248) 7.30 (.287) 6.70 (.264) 1.52 (.060) 1.14 (.045) 14.22 (.560) 13.72 (.540) 3L TO-220 3.5 50 3.15 (.124) 2.95 (.116) 6.17 (.243) REF 1.40 (.055) 1.14 (.045) 3.70 (.146) 3.30 (.130) 1.02 (.040) 0.63 (.025) 0.56 (.022) 0.38 (.014) 2.79 (.110) 2.29 (.090) 5.33 (.210) 4.83 (.190) 2.30 (.090) 2.92 (.115) 2.29 (.090) 0.35 (.014) 0.25 (.010) 1.70 (.067) 1.50 (.060) 0.10 (.004) 0.02 (.001) 3 Lead D2PAK (DP) 10.31 (.406) 10.05 (.396) 1.05 (.041) 0.85 (.033) 0.85 (.033) 0.65 (.026) 1.30 (.051) 1.10 (.043) 10° MAX 4.60 (.181) 1.40 (.055) 1.14 (.045) 1.68 (.066) 1.40 (.055) 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) Ordering Information Part Number CS5201-1GT3 CS5201-1GDP3 CS5201-1GDPR3 CS5201-1GST3 CS5201-1GSTR3 Rev. 2/16/98 Type 1A, adj. output 1A, adj. output 1A, adj. output 1A, adj. output 1A, adj. output Description 3 L TO-220 Straight 3 L D2PAK 3 L D2PAK (tape & reel) 3 L SOT-223 3 L SOT-223 (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. 7 © 1999 Cherry Semiconductor Corporation