TPS74801 www.ti.com SBVS074 - JANUARY 2007 1.5A LDO Linear Regulator with Programmable Soft-Start FEATURES * * * * * * * * * Ultra-Low VIN and VOUT Range: 0.8V to 5.5V VBIAS Range 2.7V to 5.5V Low Dropout: 60mV typ at 1.5A, VBIAS = 5V Power Good (PG) Output Allows Supply Monitoring or Provides a Sequencing Signal for Other Supplies 2% Accuracy Over Line/Load/Temperature Programmable Soft-Start Provides Linear Voltage Startup VBIAS Permits Low VIN Operation with Good Transient Response Stable with Any Output Capacitor 2.2F Available in a Small 3mm x 3mm x 1mm SON-10 Package APPLICATIONS * * * * * FPGA Applications DSP Core and I/O Voltages Post-Regulation Applications Applications With Special Start-Up Time or Sequencing Requirements Hot-Swap and Inrush Controls DESCRIPTION The TPS74801 low-dropout (LDO) linear regulator provides an easy-to-use robust power management solution for a wide variety of applications. User-programmable soft-start minimizes stress on the input power source by reducing capacitive inrush current on start-up. The soft-start is monotonic and well-suited for powering many different types of processors and ASICs. The enable input and power-good output allow easy sequencing with external regulators. This complete flexibility permits the user to configure a solution that meets the sequencing requirements of FPGAs, DSPs, and other applications with special start-up requirements. A precision reference and error amplifier deliver 2% accuracy over load, line, temperature, and process. The device is stable with any output capacitor type, and is fully specified from -40C to +125C. The TPS74801 is offered in a small 3mm x 3mm SON-10 package, yielding a highly compact, total solution size. CSS = 0nF CSS = 1nF 0.5V/div VOUT CSS = 2.2nF VIN IN CIN PG R3 BIAS EN VBIAS TPS74801 R1 SS GND CBIAS CSS 3.8V VEN VOUT OUT FB 1V/div 1.8V COUT R2 Time (1ms/div) Figure 2. Turn-On Response Figure 1. Typical Application Circuit (Adjustable) Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright (c) 2007, Texas Instruments Incorporated TPS74801 www.ti.com SBVS074 - JANUARY 2007 This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. ORDERING INFORMATION (1) VOUT (2) PRODUCT TPS748xxyyyz (1) XX is nominal output voltage (for example, 12 = 1.2V, 15 = 1.5V, 01 = Adjustable). (3) YYY is package designator. Z is package quantity. For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the TI website at www.ti.com. Fixed output voltages from 0.8V to 3.3V are available; minimum order quantities may apply. Contact factory for details and availability. For fixed 0.8V operation, tie FB to OUT. (2) (3) ABSOLUTE MAXIMUM RATINGS (1) At TJ = -40C to +125C, unless otherwise noted. All voltages are with respect to GND. TPS74801 UNIT VIN, VBIAS Input voltage range -0.3 to +6 V VEN Enable voltage range -0.3 to +6 V VPG Power-good voltage range -0.3 to +6 V VSS Soft-start voltage range -0.3 to +6 V VFB Feedback voltage range -0.3 to +6 V VOUT Output voltage range -0.3 to VIN + 0.3 V IOUT Maximum output current Internally limited Output short-circuit duration Indefinite PDISS Continuous total power dissipation TJ Operating junction temperature range -40 to +125 C TSTG Storage junction temperature range -55 to +150 C (1) See Dissipation Ratings Table Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. DISSIPATION RATINGS (1) (2) 2 PACKAGE JA JC TA < +25C POWER RATING DERATING FACTOR ABOVE TA = +25C DRC (SON) High-K (1) (2) 52 48 1.92 W 19 mW/C The JEDEC High-K (2s2p) board design used to derive this data was a 3 inch x 3 inch multilayer board with 1-ounce internal power and ground planes and 2-ounce copper traces on the top and bottom of the board See the Layout Recommendations and Power Dissipation section for additional thermal information. Submit Documentation Feedback TPS74801 www.ti.com SBVS074 - JANUARY 2007 ELECTRICAL CHARACTERISTICS At VEN = 1.1V, VIN = VOUT + 0.3V, CBIAS = 0.1F, CIN = COUT = 10F, CNR = , IOUT = 50mA, VBIAS = 5.0V, and TJ = -40C to +125C, unless otherwise noted. Typical values are at TJ = +25C. TPS74801 PARAMETER TEST CONDITIONS MAX UNIT VIN Input voltage range VOUT + VDO 5.5 V VBIAS Bias pin voltage range 2.7 5.5 V 0.804 V 3.6 V 2 % VREF Internal reference (Adj.) VOUT MIN TJ = +25C 0.796 Output voltage range VIN = 5V, IOUT = 1.5A VREF Accuracy (1) 2.97V VBIAS 5.5V, 50mA IOUT 1.5A -2 VOUT/VIN Line regulation VOUT/IOUT Load regulation VDO VIN dropout voltage (2) ICL Current limit VOUT (NOM) + 0.3 VIN 5.5V 50mA IOUT 1.5A Shutdown supply current (IGND) PSRR Power-supply rejection (VBIAS to VOUT) Noise Output noise voltage tSTR Minimum startup time ISS Soft-start charging current VEN, LO Enable input low level HYS Enable pin hysteresis VIT PG trip threshold IPG, LKG PG leakage current (1) (2) TJ Operating junction temperature TSD Thermal shutdown temperature %/A 165 mV 1.6 V VOUT = 80% x VOUT (NOM) 2.0 VEN 0.4V -1 5.5 A 1 2 mA 1 50 A 150 1 A 1kHz, IOUT = 1.5A, VIN = 1.8V, VOUT = 1.5V 60 300kHz, IOUT = 1.5A, VIN = 1.8V, VOUT = 1.5V 30 1kHz, IOUT = 1.5A, VIN = 1.8V, VOUT = 1.5V 50 300kHz, IOUT = 1.5A, VIN = 1.8V, VOUT = 1.5V 30 100Hz to 100kHz, IOUT = 1.5A, CSS = 0.001F 25 x VOUT VRMS RLOAD for IOUT = 1.0A, CSS = open 200 s dB dB VSS = 0.4V 440 nA 1.1 5.5 V 0 0.4 V 50 mV s 20 VEN = 5V VOUT decreasing 85 VHYS PG trip hysteresis VPG, LO PG output low voltage %/V 0.09 60 VEN, DG Enable pin deglitch time IEN Enable pin current 0.03 1.31 VEN, HI Enable input high level VEN, 0.5 IOUT = 1.5A, VIN = VBIAS IFB Feedback pin current Power-supply rejection (VIN to VOUT) 0.8 IOUT = 1.5A, VBIAS - VOUT (NOM) 3.25V IBIAS Bias pin current ISHDN TYP 0.1 1 A 90 94 %VOUT 3 IPG = 1mA (sinking), VOUT < VIT VPG = 5.25V, VOUT > VIT 0.1 -40 Shutdown, temperature increasing +165 Reset, temperature decreasing +140 %VOUT 0.3 V 1 A +125 C C Adjustable devices tested at 0.8V; resistor tolerance is not taken into account. Dropout is defined as the voltage from VIN to VOUT when VOUT is 3% below nominal. Submit Documentation Feedback 3 TPS74801 www.ti.com SBVS074 - JANUARY 2007 BLOCK DIAGRAM IN Current Limit BIAS UVLO OUT Thermal Limit 0.44mA VOUT R1 SS CSS Soft-Start Discharge 0.8V Reference FB PG EN Hysteresis and Deglitch R2 0.9V VREF GND Table 1. Standard 1% Resistor Values for Programming the Output Voltage (1) (1) R1 (k) R2 (k) VOUT (V) Short Open 0.8 0.619 4.99 0.9 1.13 4.53 1.0 1.37 4.42 1.05 1.87 4.99 1.1 2.49 4.99 1.2 4.12 4.75 1.5 3.57 2.87 1.8 3.57 1.69 2.5 3.57 1.15 3.3 VOUT = 0.8 x (1 + R1/R2) Table 2. Standard Capacitor Values for Programming the Soft-Start Time (1) (1) 4 tSS(s) = 0.8 x CSS(F)/4.4 x CSS SOFT-START TIME Open 0.1ms 270pF 0.5ms 560pF 1ms 2.7nF 5ms 5.6nF 10ms 0.01F 18ms 10-7 Submit Documentation Feedback TPS74801 www.ti.com SBVS074 - JANUARY 2007 DEVICE INFORMATION DRC PACKAGE 3mm x 3mm QFN (TOP VIEW) IN 1 IN 2 PG 3 BIAS 4 Thermal Pad EN 5 10 OUT 9 OUT 8 FB 7 SS 6 GND PIN DESCRIPTIONS NAME DRC (SON) IN 1, 2 DESCRIPTION EN 5 SS 7 Soft-Start pin. A capacitor connected on this pin to ground sets the start-up time. If this pin is left unconnected, the regulator output soft-start ramp time is typically 200s. BIAS 4 Bias input voltage for error amplifier, reference, and internal control circuits. PG 3 Power-Good pin. An open-drain, active-high output that indicates the status of VOUT. When VOUT exceeds the PG trip threshold, the PG pin goes into a high-impedance state. When VOUT is below this threshold the pin is driven to a low-impedance state. A pull-up resistor from 10k to 1M should be connected from this pin to a supply of up to 5.5V. The supply can be higher than the input voltage. Alternatively, the PG pin can be left unconnected if output monitoring is not necessary. FB 8 Feedback pin. The feedback connection to the center tap of an external resistor divider network that sets the output voltage. This pin must not be left floating. Input to the device. Enable pin. Driving this pin high enables the regulator. Driving this pin low puts the regulator into shutdown mode. This pin must not be left unconnected. OUT 9, 10 GND 6 Regulated output voltage. No capacitor is required on this pin for stability. Ground Thermal Pad -- Should be soldered to the ground plane for increased thermal performance. Submit Documentation Feedback 5 TPS74801 www.ti.com SBVS074 - JANUARY 2007 TYPICAL CHARACTERISTICS At TJ = +25C, VIN = VOUT(TYP) + 0.3V, VBIAS = 5V, IOUT = 50mA, VEN = VIN, CIN = 1F, CBIAS = 4.7F, and COUT = 10F, unless otherwise noted. VBIAS LINE REGULATION 0.5 0.15 0.4 0.3 0.10 Change in VOUT (%) Change in VOUT (%) VIN LINE REGULATION 0.20 -40C 0.05 0 +25C +125C -0.05 0.2 -40C 0.1 0 -0.1 +125C +25C -0.2 -0.01 -0.3 -0.15 -0.4 -0.20 -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 0.5 5.0 1.0 1.5 2.0 VIN - VOUT (V) 2.5 3.0 3.5 4.0 VBIAS - VOUT (V) Figure 3. Figure 4. LOAD REGULATION LOAD REGULATION 1.2 0.5 0.4 0.3 Change in VOUT (%) Change in VOUT (%) 1.0 0.8 0.6 0.4 0.2 +125C 0.1 0 -40C +25C -0.1 -0.2 -0.3 0.2 -0.4 0 10 20 30 40 0.5 1.0 1.5 IOUT (mA) IOUT (A) Figure 5. Figure 6. VIN DROPOUT VOLTAGE vs IOUT AND TEMPERATURE (TJ) VIN DROPOUT VOLTAGE vs (VBIAS - VOUT) AND TEMPERATURE (TJ) 100 200 90 180 80 +125C 70 60 50 40 +25C 30 20 IOUT = 1.5A 160 140 120 +125C 100 +25C 80 60 40 -40C 10 -40C 20 0 0 0 6 -0.5 0.05 50 VDO (VIN - VOUT) (mV) VDO (VIN - VOUT) (mV) 0 0.5 1.0 1.5 1.0 1.5 2.0 2.5 3.0 IOUT (A) VBIAS - VOUT (V) Figure 7. Figure 8. Submit Documentation Feedback 3.5 4.0 4.5 TPS74801 www.ti.com SBVS074 - JANUARY 2007 TYPICAL CHARACTERISTICS (continued) At TJ = +25C, VIN = VOUT(TYP) + 0.3V, VBIAS = 5V, IOUT = 50mA, VEN = VIN, CIN = 1F, CBIAS = 4.7F, and COUT = 10F, unless otherwise noted. VIN DROPOUT VOLTAGE vs (VBIAS - VOUT) AND TEMPERATURE (TJ) 200 2200 IOUT = 0.5A 180 2000 160 VDO (VBIAS - VOUT) (mV) VDO (VIN - VOUT) (mV) VBIAS DROPOUT VOLTAGE vs IOUT AND TEMPERATURE (TJ) 140 120 100 +25C 80 +125C 60 40 -40C 1800 1600 +125C 1400 1200 +25C 1000 -40C 800 20 600 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 4.5 0.5 VBIAS - VOUT (V) Figure 10. VBIAS PSRR vs FREQUENCY VIN PSRR vs FREQUENCY 90 80 IOUT = 0.1A IOUT = 1.5A 70 60 50 40 IOUT = 0.5A 30 VIN = 1.8V VOUT = 1.2V VBIAS = 5V CSS = 1nF 20 10 0 10 Power-Supply Rejection Ratio (dB) 90 Power-Supply Rejection Ratio (dB) 1.5 IOUT (A) Figure 9. 80 70 IOUT = 100mA 60 50 40 30 20 VIN = 1.8V VOUT = 1.2V CSS = 1nF 10 0 100 1k 10k 100k 1M 10 10M 100 Figure 12. 1kHz 10kHz 50 40 100kHz 30 20 500kHz 10 0 0.25 0.50 0.75 1.00 1.25 1.50 100k 1M 10M NOISE SPECTRAL DENSITY 60 0 10k Figure 11. 1.75 2.00 2.25 Output Spectral Noise Density (mV/OHz) 70 1k Frequency (Hz) VOUT = 1.2V IOUT = 1.5A CSS = 1nF 80 IOUT = 1.5A Frequency (Hz) VIN PSRR vs (VIN - VOUT) 90 Power-Supply Rejection Ratio (dB) 1.0 1 IOUT = 100mA VOUT = 1.2V CSS = 0nF 0.1 CSS = 10nF CSS = 1nF 0.01 100 VIN - VOUT (V) 1k 10k 100k Frequency (Hz) Figure 13. Figure 14. Submit Documentation Feedback 7 TPS74801 www.ti.com SBVS074 - JANUARY 2007 TYPICAL CHARACTERISTICS (continued) At TJ = +25C, VIN = VOUT(TYP) + 0.3V, VBIAS = 5V, IOUT = 50mA, VEN = VIN, CIN = 1F, CBIAS = 4.7F, and COUT = 10F, unless otherwise noted. VBIAS LINE TRANSIENT (1A) VIN LINE TRANSIENT CSS = 1nF COUT = 10mF (Ceramic) COUT = 10mF (Ceramic) 100mV/div 100mV/div COUT = 2.2mF (Ceramic) 100mV/div CSS = 1nF 3.8V 5.0V 1V/div 1V/div 1V/ms 3.3V 1V/ms 1.8V Time (50ms/div) Time (50ms/div) Figure 15. Figure 16. OUTPUT LOAD TRANSIENT RESPONSE TURN-ON RESPONSE COUT = 470mF (OSCON) CSS = 0nF 100mV/div COUT = 10mF (Ceramic) 100mV/div CSS = 1nF 0.5V/div VOUT CSS = 2.2nF COUT = 2.2mF (Ceramic) 100mV/div 3.8V CSS = 1nF 1A/div VEN 1.8V 1V/div 1A/ms 50mA Time (50ms/div) Time (1ms/div) Figure 17. Figure 18. POWER-UP/POWER-DOWN BIAS PIN CURRENT vs IOUT AND TEMPERATURE (TJ) 2.0 1.8 +125C 1.6 VIN = VBIAS = VEN 1.4 1V/div IBIAS (mA) VPG (500mV/div) VOUT 1.2 1.0 0.8 -40C 0.6 +25C 0.4 0.2 0 Time (20ms/div) 0 0.2 0.4 0.6 0.8 1.0 IOUT (A) Figure 19. 8 Figure 20. Submit Documentation Feedback 1.2 1.4 1.6 TPS74801 www.ti.com SBVS074 - JANUARY 2007 TYPICAL CHARACTERISTICS (continued) At TJ = +25C, VIN = VOUT(TYP) + 0.3V, VBIAS = 5V, IOUT = 50mA, VEN = VIN, CIN = 1F, CBIAS = 4.7F, and COUT = 10F, unless otherwise noted. BIAS PIN CURRENT vs VBIAS AND TEMPERATURE (TJ) SOFT-START CHARGING CURRENT (ISS) vs TEMPERATURE (TJ) 2.0 500 1.8 475 +125C 1.6 450 1.2 ISS (nA) IBIAS (mA) 1.4 +25C 1.0 0.8 425 400 375 0.6 -40C 350 0.4 325 0.2 300 0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 -50 25 50 75 VBIAS (V) Junction Temperature (C) Figure 21. Figure 22. LOW-LEVEL PG VOLTAGE vs CURRENT 100 125 CURRENT LIMIT vs (VBIAS - VOUT) 1.0 4.0 0.9 3.8 0.8 3.6 0.7 3.4 Current Limit (A) VOL Low-Level PG Voltage (V) 0 -25 0.6 0.5 0.4 0.3 3.2 3.0 -40C 2.8 +25C 2.6 0.2 2.4 0.1 2.2 0 VOUT = 0.8V +125C 2.0 0 2 4 6 8 10 12 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 VBIAS - VOUT (V) PG Current (mA) Figure 23. Figure 24. Submit Documentation Feedback 9 TPS74801 www.ti.com SBVS074 - JANUARY 2007 APPLICATION INFORMATION The TPS74801 belongs to a family of low dropout regulators that feature soft-start capability. These regulators use a low current bias input to power all internal control circuitry, allowing the NMOS pass transistor to regulate very low input and output voltages. The use of an NMOS-pass FET offers several critical advantages for many applications. Unlike a PMOS topology device, the output capacitor has little effect on loop stability. This architecture allows the TPS74801 to be stable with any capacitor type of value 2.2F or greater. Transient response is also superior to PMOS topologies, particularly for low VIN applications. The TPS74801 features a programmable voltage-controlled soft-start circuit that provides a smooth, monotonic start-up and limits startup inrush currents that may be caused by large capacitive loads. A power-good (PG) output is available to allow supply monitoring and sequencing of other supplies. An enable (EN) pin with hysteresis and deglitch allows slow-ramping signals to be used for sequencing the device. The low VIN and VOUT capability allows for inexpensive, easy-to-design, and efficient linear regulation between the multiple supply voltages often present in processor intensive systems. Figure 25 illustrates the typical application circuit for the TPS74801 adjustable input device. VIN IN CIN 1mF PG R3 BIAS EN VBIAS TPS74801 R1 SS CBIAS 1mF VOUT OUT FB GND CSS COUT 10mF R2 ( VOUT = 0.8 1 + R1 R2 ) 1.193 INPUT, OUTPUT, AND BIAS CAPACITOR REQUIREMENTS The device is designed to be stable for all available types and values of output capacitors 2.2F. The device is also stable with multiple capacitors in parallel, which can be of any type or value. The capacitance required on the IN and BIAS pins is strongly dependent on the input supply source impedance. To counteract any inductance in the input, the minimum recommended capacitor for VIN and VBIAS is 1F. If VIN and VBIAS are connected to the same supply, the recommended minimum capacitor for VBIAS is 4.7F. Good quality, low ESR capacitors should be used on the input; ceramic X5R and X7R capacitors are preferred. These capacitors should be placed as close the pins as possible for optimum performance. TRANSIENT RESPONSE The TPS74801 was designed to have excellent transient response within most applications with a small amount of output capacitance. In some cases, the transient response may be limited by the transient response of the input supply. This limitation is especially true in applications where the difference between the input and output is less than 300mV. In this case, adding additional input capacitance improves the transient response much more than just adding additional output capacitance would do. With a solid input supply, adding additional output capacitance reduces undershoot and overshoot during a transient event; refer to Figure 17 in the Typical Characteristics section. Because the TPS74801 is stable with output capacitors as low as 2.2F, many applications may then need very little capacitance at the LDO output. For these applications, local bypass capacitance for the powered device may be sufficient to meet the transient requirements of the application. This design reduces the total solution cost by avoiding the need to use expensive, high-value capacitors at the LDO output. Figure 25. Typical Application Circuit for the TPS74801 (Adjustable) R1 and R2 can be calculated for any output voltage using the formula shown in Figure 25. Refer to Table 1 for sample resistor values of common output voltages. In order to achieve the maximum accuracy specifications, R2 should be 4.99k. 10 Submit Documentation Feedback TPS74801 www.ti.com SBVS074 - JANUARY 2007 DROPOUT VOLTAGE VIN The TPS74801 offers very low dropout performance, making it well-suited for high-current, low VIN/low VOUT applications. The low dropout of the TPS74801 allows the device to be used in place of a DC/DC converter and still achieve good efficiency. This provides designers with the power architecture for their application to achieve the smallest, simplest, and lowest cost solution. There are two different specifications for dropout voltage with the TPS74801. The first specification (shown in Figure 26) is referred to as VIN Dropout and is used when an external bias voltage is applied to achieve low dropout. This specification assumes that VBIAS is at least 1.56V above VOUT, which is the case for VBIAS when powered by a 3.3V rail with 5% tolerance and with VOUT = 1.5V. If VBIAS is less than VOUT +1.56V, VIN dropout is less than specified. BIAS Reference IN BIAS Reference IN VBIAS = 3.3V 5% VIN = 3.3V 5V VOUT = 1.5V IOUT = 1.5A Efficiency = 45% OUT VOUT COUT FB Simplified Block Diagram Figure 27. Typical Application of the TPS74801 Without an Auxiliary Bias Rail PROGRAMMABLE SOFT-START VBIAS = 5V 5% VIN = 1.8V VOUT = 1.5V IOUT = 1.5A Efficiency = 83% OUT VOUT COUT FB Simplified Block Diagram Figure 26. Typical Application of the TPS74801 Using an Auxiliary Bias Rail The second specification (shown in Figure 27) is referred to as VBIAS Dropout and applies to applications where IN and BIAS are tied together. This option allows the device to be used in applications where an auxiliary bias voltage is not available or low dropout is not required. Dropout is limited by BIAS in these applications because VBIAS provides the gate drive to the pass FET; therefore, VBIAS must be 1.56V above VOUT. The TPS74801 features a programmable, monotonic, voltage-controlled soft-start that is set with an external capacitor (CSS). This feature is important for many applications because it eliminates power-up initialization problems when powering FPGAs, DSPs, or other processors. The controlled voltage ramp of the output also reduces peak inrush current during start-up, minimizing start-up transient events to the input power bus. To achieve a linear and monotonic soft-start, the TPS74801 error amplifier tracks the voltage ramp of the external soft-start capacitor until the voltage exceeds the internal reference. The soft-start ramp time is dependant on the soft-start charging current (ISS), soft-start capacitance (CSS), and the internal reference voltage (VREF), and can be calculated using Equation 1: (VREF CSS) tSS = ISS (1) If large output capacitors are used, the device current limit (ICL) and the output capacitor may set the start-up time. In this case, the start-up time is given by Equation 2: (VOUT(NOM) COUT) tSSCL = ICL(MIN) (2) where: VOUT(NOM) is the nominal output voltage, COUT is the output capacitance, and ICL(MIN) is the minimum current limit for the device. In applications where monotonic startup is required, the soft-start time given by Equation 1 should be set greater than Equation 2. Submit Documentation Feedback 11 TPS74801 www.ti.com SBVS074 - JANUARY 2007 The maximum recommended soft-start capacitor is 0.015F. Larger soft-start capacitors can be used and will not damage the device; however, the soft-start capacitor discharge circuit may not be able to fully discharge the soft-start capacitor when enabled. Soft-start capacitors larger than 0.015F could be a problem in applications where it is necessary to rapidly pulse the enable pin and still require the device to soft-start from ground. CSS must be low-leakage; X7R, X5R, or C0G dielectric materials are preferred. Refer to Table 2 for suggested soft-start capacitor values. reduced by half and is typically 30VRMS for a 1.2V output (10Hz to 100kHz). Further increasing CSS has little effect on noise. Because most of the output noise is generated by the internal reference, the noise is a function of the set output voltage. The RMS noise with a 0.001F soft-start capacitor is given in Equation 3: ( VN(mVRMS) = 25 mVRMS V )x V OUT(V) (3) The low output noise of the TPS74801 makes it a good choice for powering transceivers, PLLs, or other noise-sensitive circuitry. SEQUENCING REQUIREMENTS VIN, VBIAS, and VEN can be sequenced in any order without causing damage to the device. However, for the soft-start function to work as intended, certain sequencing rules must be applied. Connecting EN to IN is acceptable for most applications, as long as VIN is greater than 1.1V and the ramp rate of VIN and VBIAS is faster than the set soft-start ramp rate. If the ramp rate of the input sources is slower than the set soft-start time, the output tracks the slower supply minus the dropout voltage until it reaches the set output voltage. If EN is connected to BIAS, the device will soft-start as programmed, provided that VIN is present before VBIAS. If VBIAS and VEN are present before VIN is applied and the set soft-start time has expired, then VOUT tracks VIN. If the soft-start time has not expired, the output tracks VIN until VOUT reaches the value set by the charging soft-start capacitor. Figure 28 shows the use of an RC-delay circuit to hold off VEN until VBIAS has ramped. This technique can also be used to drive EN from VIN. An external control signal can also be used to enable the device after VIN and VBIAS are present. VIN IN VOUT OUT R1 CIN BIAS TPS74801 FB EN CBIAS C GND The enable threshold is typically 0.8V and varies with temperature and process variations. Temperature variation is approximately -1mV/C; process variation accounts for most of the rest of the variation to the 0.4V and 1.1V limits. If precise turn-on timing is required, a fast rise-time signal must be used to enable the TPS74801. If not used, EN can be connected to either IN or BIAS. If EN is connected to IN, it should be connected as close as possible to the largest capacitance on the input to prevent voltage droops on that line from triggering the enable circuit. POWER-GOOD SS CSS Figure 28. Soft-Start Delay Using an RC Circuit to Enable the Device OUTPUT NOISE The TPS74801 provides low output noise when a soft-start capacitor is used. When the device reaches the end of the soft-start cycle, the soft-start capacitor serves as a filter for the internal reference. By using a 0.001F soft-start capacitor, the output noise is 12 The enable (EN) pin is active high and is compatible with standard digital signaling levels. VEN below 0.4V turns the regulator off, while VEN above 1.1V turns the regulator on. Unlike many regulators, the enable circuitry has hysteresis and deglitching for use with relatively slowly ramping analog signals. This configuration allows the TPS74801 to be enabled by connecting the output of another supply to the EN pin. The enable circuitry typically has 50mV of hysteresis and a deglitch circuit to help avoid on-off cycling as a result of small glitches in the VEN signal. COUT R2 R VBIAS ENABLE/SHUTDOWN The power-good (PG) pin is an open-drain output and can be connected to any 5.5V or lower rail through an external pull-up resistor. This pin requires at least 1.1V on VBIAS in order to have a valid output. The PG output is high-impedance when VOUT is greater than VIT + VHYS. If VOUT drops below VIT or if VBIAS drops below 1.9V, the open-drain output turns on and pulls the PG output low. The PG pin also asserts when the device is disabled. The pull-up resistor for PG should be in the range of 10k to 1M. Submit Documentation Feedback TPS74801 www.ti.com SBVS074 - JANUARY 2007 INTERNAL CURRENT LIMIT The TPS74801 features a factory-trimmed, accurate current limit that is flat over temperature and supply voltage. The current limit allows the device to supply surges of up to 2A and maintain regulation. The current limit responds in about 10s to reduce the current during a short-circuit fault. The internal current limit protection circuitry of the TPS74801 is designed to protect against overload conditions. It is not intended to allow operation above the rated current of the device. Continuously running the TPS74801 above the rated current degrades device reliability. THERMAL PROTECTION Thermal protection disables the output when the junction temperature rises to approximately +160C, allowing the device to cool. When the junction temperature cools to approximately +140C, the output circuitry is enabled. Depending on power dissipation, thermal resistance, and ambient temperature the thermal protection circuit may cycle on and off. This cycling limits the dissipation of the regulator, protecting it from damage as a result of overheating. Activation of the thermal protection circuit indicates excessive power dissipation or inadequate heatsinking. For reliable operation, junction temperature should be limited to +125C maximum. To estimate the margin of safety in a complete design (including heatsink), increase the ambient temperature until thermal protection is triggered; use worst-case loads and signal conditions. For good reliability, thermal protection should trigger at least +40C above the maximum expected ambient condition of the application. This condition produces a worst-case junction temperature of +125C at the highest expected ambient temperature and worst-case load. The internal protection circuitry of the TPS74801 is designed to protect against overload conditions. It is not intended to replace proper heatsinking. Continuously running the TPS74801 into thermal shutdown degrades device reliability. LAYOUT RECOMMENDATIONS AND POWER DISSIPATION An optimal layout can greatly improve transient performance, PSRR, and noise. To minimize the voltage drop on the input of the device during load transients, the capacitance on IN and BIAS should be connected as close as possible to the device. This capacitance also minimizes the effects of parasitic inductance and resistance of the input source and can, therefore, improve stability. To achieve optimal transient performance and accuracy, the top side of R1 in Figure 25 should be connected as close as possible to the load. If BIAS is connected to IN, it is recommended to connect BIAS as close to the sense point of the input supply as possible. This connection minimizes the voltage drop on BIAS during transient conditions and can improve the turn-on response. Knowing the device power dissipation and proper sizing of the thermal plane that is connected to the thermal pad is critical to avoiding thermal shutdown and ensuring reliable operation. Power dissipation of the device depends on input voltage and load conditions and can be calculated using Equation 4: PD = (VIN - VOUT) IOUT (4) Power dissipation can be minimized and greater efficiency can be achieved by using the lowest possible input voltage necessary to achieve the required output voltage regulation. On the SON (DRC) package, the primary conduction path for heat is through the exposed pad to the printed circuit board (PCB). The pad can be connected to ground or be left floating; however, it should be attached to an appropriate amount of copper PCB area to ensure the device will not overheat. The maximum junction to ambient thermal resistance depends on the maximum ambient temperature, maximum device junction temperature, and power dissipation of the device, and can be calculated using Equation 5: (+125C - TA) RqJA = PD (5) Knowing the maximum RJA and system air flow, the minimum amount of PCB copper area needed for appropriate heatsinking can be calculated using Figure 29 through Figure 31. Submit Documentation Feedback 13 TPS74801 www.ti.com SBVS074 - JANUARY 2007 PCB Top View PCB Cross Section TJ RqJC TC RqCS 0.062" TS 0.5 in2 RqSA 4-layer, 0.062" FR4. Vias are 0.012" diameter, plated. Top/Bottom layers are 2oz. copper. Inner layers are 1oz. copper. 1.0 in2 TA 2.0 in2 RqJA = RqJC + RqCS + RqSA 90 85 0 LFM 80 qJA (C/W) 75 150 LFM 70 65 250 LFM 60 55 50 45 40 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 2 Area (in ) Figure 29. PCB Layout and Corresponding RJA Data, No Vias Under Thermal Pad 14 Submit Documentation Feedback TPS74801 www.ti.com SBVS074 - JANUARY 2007 PCB Top View PCB Cross Section TJ RqJC TC RqCS 0.062" TS 0.5 in2 RqSA 4-layer, 0.062" FR4. Vias are 0.012" diameter, plated. Top/Bottom layers are 2oz. copper. Inner layers are 1oz. copper. 1.0 in2 TA 2.0 in2 RqJA = RqJC + RqCS + RqSA 90 85 80 qJA (C/W) 75 70 65 0 LFM 60 150 LFM 55 50 45 250 LFM 40 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Area (in2) Figure 30. PCB Layout and Corresponding RJA Data, Vias Under Thermal Pad Submit Documentation Feedback 15 TPS74801 www.ti.com SBVS074 - JANUARY 2007 PCB Top View PCB Cross Section TJ RqJC TC RqCS 0.062" TS RqSA 4-layer, 0.062" FR4. Vias are 0.012" diameter, plated. Top/Bottom layers are 2oz. copper. Inner layers are 1oz. copper. 0.5 in2 TA 1.0 in2 RqJA = RqJC + RqCS + RqSA 2.0 in2 90 85 80 qJA (C/W) 75 0 LFM 70 65 60 150 LFM 55 250 LFM 50 45 40 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 2 Area (in ) Figure 31. PCB Layout and Corresponding RJA Data, Top Layer Only 16 Submit Documentation Feedback PACKAGE OPTION ADDENDUM www.ti.com 6-Feb-2007 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TPS74801DRCR ACTIVE SON DRC 10 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS74801DRCT ACTIVE SON DRC 10 250 CU NIPDAU Level-2-260C-1 YEAR Green (RoHS & no Sb/Br) Lead/Ball Finish MSL Peak Temp (3) (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. 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