CS5253B-1 CS5253B-1 3A LDO 5-Pin Adjustable Linear Regulator with Remote Sense Applications Features Description pin is less than 1mV for an output voltage of 2.5V with a load step of 10mA to 3A. This new very low dropout linear regulator reduces total power dissipation in the application. To achieve very low dropout, the internal pass transistor is powered separately from the control circuitry. Furthermore, with the control and power inputs tied together, this device can be used in single supply configuration and still offer a better dropout voltage than conventional PNP-NPN based LDO regulators. In this mode the dropout is determined by the minimum control voltage. The CS5253B-1 has a very fast transient loop response which can be adjusted using a small capacitor on the Adjust pin. The CS5253B-1 is offered in a fiveterminal D2PAK package, which allows for the implementation of a remote-sense pin permitting very accurate regulation of output voltage directly at the load, where it counts, rather than at the regulator. This remote sensing feature virtually eliminates output voltage variations due to load changes and resistive voltage drops. Typical load regulation measured at the sense ■ VOUT Range is 1.25V to 5V @ 3A ■ VPOWER Dropout < 0.40V @ 3A ■ VCONTROL Dropout < 1.05V @ 3A Internal protection circuitry provides for “bust-proof” operation, similar to three-terminal regulators. This circuitry, which includes overcurrent, short circuit, and over-temperature protection will self protect the regulator under all fault conditions. ■ 1% Trimmed Reference The CS5253B-1 is ideal for generating a 2.5V supply to power graphics controllers used on VGA cards. Its remote sense and low value capacitance requirements make this a low cost, high performance solution. The CS5253B-1 is optimized from the CS5253-1 to allow a lower value of output capacitor to be used at the expense of a slower transient response. ■ Drop-In Replacement for EZ1582 ■ Fast Transient Response ■ Remote Voltage Sensing ■ Thermal Shutdown ■ Current Limit ■ Short Circuit Protection ■ Backwards Compatible with 3-pin Regulators ■ Very Low Dropout Reduces Total Power Consumption Package Option Applications Diagram 5 Lead D2PAK RDIS +5V VCONTROL 2.5V @3A VOUT VSENSE CS5253B-1 +3.3V VPOWER 10µF 10V 124 Adjust 124 33µF 5V CLOAD (Optional) 100µF 5V 1 1. VSENSE 2. Adjust 3. VOUT 4. VCONTROL Gnd Gnd RDIS 5. VPOWER Tab = VOUT ON Semiconductor 2000 South County Trail, East Greenwich, RI 02818 Tel: (401)885–3600 Fax: (401)885–5786 N. American Technical Support: 800-282-9855 Web Site: www.cherry–semi.com December, 1999 - Rev. 1 1 CS5253B-1 Absolute Maximum Ratings VPOWER Input Voltage.......................................................................................................................................................................6V VCONTROL Input Voltage.................................................................................................................................................................13V Operating Junction Temperature Range ................................................................................................................0°C ≤ TJ ≤ 150°C Storage Temperature Range.....................................................................................................................................–65°C to +150°C Lead Temperature Soldering Reflow (SMD styles only) ......................................................................................60 sec. max above 183°C, 230°C peak ESD Damage Threshold............................................................................................................................................................2kV Electrical Characteristics: 0°C ≤ TA ≤ 70°C; 0°C ≤ TJ ≤ 150°C; VSENSE = VOUT and VAdj = 0V; unless otherwise specified. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 1.237 (–1%) 1.250 1.263 (+1%) V Reference Voltage VCONTROL = 2.75V to 12V, VPOWER = 2.05V to 5.5V, IOUT = 10mA to 3A Line Regulation VCONTROL = 2.5V to 12V, VPOWER = 1.75V to 5.5V, IOUT = 10mA .02 .20 % Load Regulation VCONTROL = 2.75V, VPOWER = 2.05V, IOUT = 10mA to 3A, with remote sense .04 .30 % Minimum Load Current (Note 1) VCONTROL = 5V, VPOWER = 3.3V, ∆VOUT = +1% 5 10 mA Control Pin Current (Note 2) Adjust Pin Current VCONTROL = 2.75V, VPOWER = 2.05V, IOUT = 100mA VCONTROL = 2.75V, VPOWER = 2.05V, IOUT = 3A VCONTROL = 2.75V, VPOWER = 2.05V, IOUT = 10mA 6 35 60 10 120 120 mA mA µA Current Limit VCONTROL = 2.75V, VPOWER = 2.05V, ∆VOUT = –4% 3.1 4.0 Short Circuit Current VCONTROL = 2.75V, VPOWER = 2.05V, VOUT = 0V 2.0 3.5 A Ripple Rejection (Note 3) VCONTROL = VPOWER = 3.25V, VRIPPLE = 1VP-P@120Hz, IOUT = 3A, CADJ = 0.1µF 60 80 dB Thermal Regulation 30ms Pulse, TA = 25°C 0.002 %/W VCONTROL Dropout Voltage (Minimum VCONTROL-VOUT) (Note 4) VPOWER = 2.05V, IOUT = 100mA VPOWER = 2.05V, IOUT = 1A VPOWER = 2.05V, IOUT = 3A 0.90 1.00 1.05 1.15 1.15 1.30 V V V VPOWER Dropout Voltage (Minimum VPOWER-VOUT) (Note 4) VCONTROL = 2.75V, IOUT = 100mA VCONTROL = 2.75V, IOUT = 1A VCONTROL = 2.75V, IOUT = 3A .05 .15 .40 .15 .25 .60 V V V RMS Output Noise Freq = 10Hz to 10kHz, TA = 25°C 0.003 Temperature Stability 0.5 Thermal Shutdown (Note 5) 150 Thermal Shutdown Hysteresis VCONTROL = 13V, VPOWER not connected, VADJUST = VOUT = VSENSE = 0V VPOWER Supply Only Output Current VPOWER = 6V, VCONTROL not connected, VADJUST = VOUT = VSENSE = 0V Note 2: Note 3: Note 4: Note 5: %VOUT % 180 210 °C 50 mA 1.0 mA 25 VCONTROL Supply Only Output Current Note 1: A 0.1 °C 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 current requirement. The VCONTROL pin current is the drive current required for the output transistor. This current will track output current with roughly a 1:100 ratio. The minimum value is equal to the quiescent current of the device. This parameter is guaranteed by design and is not 100% production tested. Dropout is defined as either the minimum control voltage, (VCONTROL) or minimum power voltage (VPOWER) to output voltage differential required to maintain 1% regulation at a particular load current. This parameter is guaranteed by design, but not parametrically tested in production. However, a 100% thermal shutdown functional test is performed on each part. 2 CS5253B-1 Package Pin Description PACKAGE PIN # PIN SYMBOL FUNCTION 5Lead D2 PAK 1 VSENSE This Kelvin sense pin allows for remote sensing of the output voltage at the load for improved regulation. It is internally connected to the positive input of the voltage sensing error amplifier. 2 Adjust This pin is connected to the low side of the internally trimmed 1% bandgap reference voltage and carries a bias current of about 50µA. A resistor divider from Adj to VOUT and from Adj to ground sets the output voltage. Also, transient response can be improved by adding a small bypass capacitor from this pin to ground. 3 VOUT This pin is connected to the emitter of the power pass transistor and provides a regulated voltage capable of sourcing 3A of current. 4 VCONTROL This is the supply voltage for the regulator control circuitry. For the device to regulate, this voltage should be between 0.9V and 1.3V (depending on the output current) greater than the output voltage. The control pin current will be about 1% of the output current. 5 VPOWER This is the power input voltage. The pin is physically connected to the collector of the power pass transistor. For the device to regulate, this voltage should be between 0.1V and 0.6V greater than the output voltage, depending on output current. The output load current of 3A is supplied through this pin. Block Diagram VPOWER VCONTROL BIAS and TSD VREF − + EA IA + − VOUT VSENSE Adjust 3 CS5253B-1 Typical Performance Characteristics Load Regulation vs Output Current 1.253 0.12 1.252 0.10 Load Regulation (%) Reference Voltage (V) Reference Voltage vs Junction Temperature 1.251 1.250 1.249 1.248 0.08 TJ = 120°C 0.06 TJ = 20°C 0.04 TJ = 0°C 0.02 1.247 0 20 40 60 80 100 0 120 0 0.5 1.0 Junction Temperature (C) Transient Response 2.0 2.5 3.0 Output Current vs VPOWER-VOUT 5.0 Measured at ∆VOUT = -1% 4.5 VOUT CS5253-1 COUT = 330µF 4.0 3.5 Output Current (A) VCONTROL = 5V VPOWER =3.3V VOUT = 2.5V CCONTROL = 10µF CADJ = 0.1µF VOUT CS5253B-1 COUT = 33µF 80A/µs 15A/µs 1.5 Output Current (A) ILOAD 10mA to 3A 3.0 2.5 2.0 1.5 1.0 0.5 Transient Response Comparison between CS5253-1 and CS5253B-1 0 0 1 2 3 4 5 6 VPOWER - VOUT (V) Minimum Load Current vs VCONTROL-VOUT Adjust Pin Current vs Junction Temperature 85 1200 VPOWER =3.3V ∆ VOUT=+1% 1150 Minimum Load Current (µA) IADJ (µA) 80 75 70 65 1100 1050 1000 950 900 850 60 800 0 20 40 60 80 100 120 140 Junction Temperature (C) 4 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 VCONTROL-VOUT (V) 9.0 10.0 11.0 CS5253B-1 Typical Performance Characteristics Short Circuit Output Current vs Junction Temperature Ripple Rejection vs Frequency 90.0 VCONTROL = 5V VPOWER = 3.3V 80.0 3.8 Ripple Rejection (dB) Short Circuit Output Current Limit (A) 3.9 3.7 3.6 3.5 70.0 60.0 50.0 40.00 VIN – VOUT = 2V IOUT = 3A VRIPPLE = 1VP-P COUT = 22µF CADJ = 0.1µF 30.0 3.4 20.0 10.0 3.3 0 20 40 60 80 100 120 101 140 102 103 Junction Temperature (C) 105 104 106 Frequency (Hz) VCONTROL Only Output Current vs Junction Temperature VCONTROL Dropout Voltage vs Output Current 12 1100 Vcontrol Dropout Voltage (mV) VCONTROL = 13V, VOUT = 0V, Vpower not connected 10 8 Iout (mA) 6 4 2 TJ = 0°C 1000 TJ = 20°C TJ = 120°C 900 VPOWER = 2.05V 0 0 20 40 60 80 100 120 800 140 0.0 0.5 VPOWER Dropout Voltage vs Output Current 2.0 2.5 3.0 916.4 VCONTROL =5V ∆ VOUT=+1% 916.3 450 400 Minimum Load Current (µA) Vpower Dropout Voltage (V) 1.5 Minimum Load Current vs VPOWER-VOUT 500 TJ = 120°C 350 TJ = 20°C 300 TJ = 0°C 250 200 150 916.2 916.1 916.0 915.9 915.8 915.7 915.6 915.5 50 0 1.0 Output Current (A) Junction Temperature (C) 915.4 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Output Current (A) 5 0.50 1.50 2.50 VPOWER-VOUT (V) 3.50 4.50 CS5253B-1 Typical Performance Characteristics: Continued VPOWER Only Output Current vs Junction Temperature VCONTROL Supply Current vs Junction Temperature 40 30 VCONTROL = 2.75V VPOWER = 2.05V 35 VPOWER = 6V VOUT = 0V VCONTROL not connected 25 30 ICONTROL (mA) IOUT (uA) 20 15 10 IOUT = 3A 25 20 15 10 IOUT = 1A 5 5 0 0 20 40 60 80 100 120 0 140 IOUT = 100mA 0 20 40 80 100 120 140 Junction Temperature (C) Junction Temperature (C) Current Limit vs VOUT Stability vs ESR 6 5.0 VPOWER = 3.3V VCONTROL = 5.0V VOUT set for 2.5V TA = 25°C VPOWER = 3.3V VCONTROL = 5.0V ILOAD = 0 to 3A VOUT = 2.5V VOUT shorted to VSENSE TJ = 0° to 150°C 5 4.5 ESR (ohms) Current Limit (A) 60 4.0 4 Unstable 3 2 Stable Region 1 3.5 0.0 0.5 1.0 1.5 2.0 2.5 0 3.0 0 VOUT (V) 10 20 30 40 50 60 70 80 90 100 Capacitance (µF) Application Notes no supply sequencing problems. The output voltage will not turn on until both supplies are operating. If the control voltage comes up first, the output current will be limited to about three milliamperes until the power input voltage comes up. If the power input voltage comes up first, the output will not turn on at all until the control voltage comes up. The output can never come up unregulated. The CS5253B-1 can also be used as a single supply device with the control and power inputs tied together. In this mode, the dropout will be determined by the minimum control voltage. Theory of Operation The CS5253B-1 linear regulator provides adjustable voltages from 1.25V to 5V at currents up to 3A. The regulator is protected against short circuits, and includes a thermal shutdown circuit with hysteresis. The output, which is current limited, consists of a PNP-NPN transistor pair and requires an output capacitor for stability. A detailed procedure for selecting this capacitor is included in the Stability Considerations section. VPOWER Function The CS5253B-1 utilizes a two supply approach to maximize efficiency. The collector of the power device is brought out to the VPOWER pin to minimize internal power dissipation under high current loads. VCONTROL provides for the control circuitry and the drive for the output NPN transistor. VCONTROL should be at least 1V greater than the output voltage. Special care has been taken to ensure that there are Output Voltage Sensing The CS5253B-1 five terminal linear regulator includes a dedicated VSENSE function. This allows for true Kelvin sensing of the output voltage. This feature can virtually eliminate errors in the output voltage due to load regulation. Regulation will be optimized at the point where the sense pin is tied to the output. 6 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 of the same composition for best tracking over temperature. Design Guidelines Remote Sense Remote sense operation can be easily obtained with the CS5253B-1 but some care must be paid to the layout and positioning of the filter capacitors around the part. The ground side of the input capacitors on the +5V and +3.3V lines and the local VOUT-to-ground local output capacitor on the IC output must be tied close to the ground connected resistor voltage divider feedback network. The top resistor of the divider must be connected directly to the VSENSE pin of the regulator. This will establish the stability of the part. This capacitor-divider resistor connection may then be connected to ground remotely at the load, giving the ground portion remote sense operation. The VSENSE line can then be tied remotely at the load connection, giving the feedback remote sense operation. The remote sense lines should be Kelvin connected so as to eliminate the effect of load current voltage drop. An optional bypass capacitor may be used at the load to reduce the effect of load variations and spikes. VCONTROL +5V VPOWER +3.3V + + 10µF 100µF RDIS VOUT CS5253B-1 3.3V 2.5V @3A VPOWER VSENSE Adjust R1 R2 Figure 2: Typical application schematic. The resistor divider sets VOUT, with the internal 1.260V reference dropped across R1. While not required, a bypass capacitor connected between the adjust pin and ground will improve transient response and ripple rejection. A 0.1µF tantalum capacitor is recommended for “first cut” design. Value and type may be varied to optimize performance vs. price. +Load VOUT VCONTROL 5V VSENSE 124 CS5253B-1 + Adjust Local Connections 33µF Remote Connections Other Adjustable Operation Considerations The CS5253B-1 linear regulator has an absolute maximum specification of 6V for the voltage difference between VPOWER and VOUT. However, the IC may be used to regulate voltages in excess of 6V. The two main considerations in such a design are the sequencing of power supplies and short circuit capability. Power supply sequencing should be such that the VCONTROL supply is brought up coincidentally with or before the VPOWER supply. This allows the IC to begin charging the output capacitor as soon as the VPOWER to VOUT differential is large enough that the pass transistor conducts. As VPOWER increases, the pass transistor will remain in dropout, and current is passed to the load until VOUT is in regulation. Further increase in the supply voltage brings the pass transistor out of dropout. In this manner, any output voltage less than 13V may be regulated, provided the VPOWER to VOUT differential is less than 6V. In the case where VCONTROL and VPOWER are shorted, there is no theoretical limit to the regulated voltage as long as the VPOWER to VOUT differential of 6V is not exceeded. There is a possibility of damaging the IC when VPOWERVOUT is greater than 6V if a short circuit occurs. 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 circuit- + Optional 124 RDIS –Load Gnd Figure 2. Remote Sense Adjustable Operation This LDO adjustable regulator has an output voltage range of 1.25V to 5V. An external resistor divider sets the output voltage as shown in Figure 2. The regulator’s voltage sensing error amplifier maintains a fixed 1.25V 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 = 1.25V × R1+R2 R1 + R2 × IADJ 7 CS5253B-1 Application Notes: continued CS5253B-1 Application Notes: continued ry can become active. Additional circuitry may be required to clamp the VPOWER to VOUT differential to less than 6V if fail safe operation is required. One possible clamp circuit is illustrated in Figure 3; 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. There is then an additional drop in output voltage given by: ∆V = ∆I × T/C where T is the time for the regulation loop to begin to respond. The very fast transient response time of the CS5253B-1 allows the ESR effect to dominate. 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 transient load conditions. The output capacitor network should be as close to the load as possible for the best transient response. External Supply External Supply VControl 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 VCONTROL drops. In the CS5253B-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 4 is recommended. VSENSE VPower VAdjust VOUT Figure 3: This circuit is an example of how the CS5253B-1 can be shortcircuit-protected when operating with VOUT > 6V. Stability Considerations The output compensation capacitor helps determine three main characteristics of a linear regulator: loop stability, start-up delay, and load transient response. Different capacitor types vary widely in tolerance, ESR (equivalent series resistance), ESL (equivalent series inductance), and variation over temperature. Tantalum and aluminum electrolytic capacitors work best, with electrolytic capacitors being less expensive in general, but varying more in capacitor value and ESR over temperature. The CS5253B-1 requires an output capacitor to guarantee loop stability. The Stability vs ESR graph in the typical performance section shows the minimum ESR needed to guarantee stability, but under ideal conditions. These include: having VOUT connected to VSENSE directly at the IC pins; the compensation capacitor located right at the pins with a minimum lead length; the adjust feedback resistor divider ground, (bottom of R2 in Figure 2), connected right at the capacitor ground; and with power supply decoupling capacitors located close to the IC pins. The actual performance will vary greatly with board layout for each application. In particular, the use of the remote sensing feature will require a larger capacitor with less ESR. For most applications, a minimum of 33µF tantalum or 150µF aluminum electrolytic, with an ESR less than 1Ω over temperature, is recommended. Larger capacitors and lower ESR will improve stability. The load transient response, during the time it takes the regulator to respond, is also determined by the output capacitor. For large changes in load current, the ESR of the output capacitor causes an immediate drop in output voltage given by: ∆V = ∆I × ESR VCONTROL VOUT CS5253B-1 VPOWER VSENSE Adjust Figure 4: Diode protection circuit. A rule of thumb useful in determining if a protection diode is required is to solve for current: I= C×V , T where I is the current flow out of the load capacitance when VCONTROL is shorted, C V T is the value of load capacitance is the output voltage, and is the time duration required for VCONTROL to transition from high to being shorted. If the calculated current is greater than or equal to the typi- 8 cal short circuit current value provided in the specifications, serious thought should be given to the use of a protection diode. 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. The maximum power dissipation for a regulator is: Current Limit The internal current limit circuit limits the output current under excessive load conditions. PD(max) = (VIN(max) -VOUT(min))IOUT(max) + VIN(max) × IIN(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 which is measured in degrees per watt. Like series electrical resistances, these thermal resistances are summed to determine the total thermal resistance between the die junction and the surrounding air, RΘJA. This total thermal resistance is comprised of three components. These resistive terms are measured from junction to case (RΘJC), case to heat sink (RΘCS), and heat sink to ambient air (RΘSA). The equation is: Short Circuit Protection The device includes short circuit protection circuitry that clamps the output current at approximately 500mA less than its current limit value. This provides for a current foldback function, which reduces power dissipation under a direct shorted load. Thermal Shutdown The thermal shutdown circuitry is guaranteed by design to activate above a die junction temperature of approximately 150°C and to shut down the regulator output. This circuitry has 25°C of typical hysteresis, thereby allowing the regulator to recover from a thermal fault automatically. RΘJA = RΘJC + RΘCS + RΘSA The value for RΘJC is 2.5°C/watt for the CS5253B-1 in the D2PAK package. For a high current regulator such as the CS5253B-1 the majority of heat is generated in the power transistor section. The value for RΘSA depends on the heat sink type, while the RΘCS 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 RΘJA can be calculated and the proper heat sink selected. For further discussion on heat sink selection, see our ON application note “Thermal Management for Linear Regulators.” Calculating Power Dissipation and Heat Sink Requirements High power regulators such as the CS5253B-1 usually operate at high junction temperatures. Therefore, it is important to calculate the power dissipation and junction temperatures accurately to ensure that an adequate heat sink is used. Since the package tab is connected to VOUT on the CS5253B-1, electrical isolation may be required for some applications. Also, as with all high power packages, thermal compound in necessary to ensure proper heat flow. For added safety, this high current LDO includes an internal thermal shutdown circuit The thermal characteristics of an IC depend on the following four factors: junction temperature, ambient temperature, die power dissipation, and the thermal resistance from the die junction to ambient air. The maximum junction temperature can be determined by: TJ(max) = TA(max) + PD(max) × RΘJA 9 CS5253B-1 Application Notes: continued CS5253B-1 Package Specification PACKAGE DIMENSIONS IN mm (INCHES) PACKAGE THERMAL DATA Thermal Data RΘJC RΘJA typ typ 5Lead D2PAK 2.5 10-50* °C/W °C/W *Depending on thermal properties of substrate. RΘJA = RΘJC + RΘCA 5 Lead D2PAK (DP) 10.31 (.406) 10.05 (.396) 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) 0.91 (.036) 0.66 (.026) 2.79 (.110) 2.29 (.090) 1.70 (.067) REF .254 (.010) REF 0.10 (.004) 0.00 (.000) 4.57 (.180) 4.31 (.170) ON Semiconductor and the ON Logo are trademarks of Semiconductor Components Industries, LLC (SCILLC). ON Semiconductor reserves the right to make changes without further notice to any products herein. For additional information and the latest available information, please contact your local ON Semiconductor representative. Ordering Information Part Number CS5253B-1GDP5 CS5253B-1GDPR5 Description 5 Lead D2PAK 5 Lead D2PAK (tape & reel) 10 © Semiconductor Components Industries, LLC, 2000 Notes Notes