TPS5410-EP www.ti.com ......................................................................................................................................................................................... SLVS910 – SEPTEMBER 2009 1-A WIDE INPUT RANGE STEP-DOWN SWIFT™ CONVERTER Check for Samples: TPS5410-EP FEATURES APPLICATIONS • • • • • • 1 2 • • • • • • • • • Wide Input Voltage Range: 5.5 V to 36 V Up to 1-A Continuous (1.2-A Peak) Output Current High Efficiency up to 95% Enabled by 110-mΩ Integrated MOSFET Switch Wide Output Voltage Range: Adjustable Down to 1.22 V with 1.5% Initial Accuracy Internal Compensation Minimizes External Parts Count Fixed 500-kHz Switching Frequency for Small Filter Size Improved Line Regulation and Transient Response by Input Voltage Feed Forward System Protected by Over Current Limiting, Over Voltage Protection and Thermal Shutdown –55°C to 125°C Operating Junction Temperature Range Available in Small 8-Pin SOIC Package For SWIFT Documentation, Application Notes and Design Software, See the TI Website at www.ti.com/swift SUPPORTS DEFENSE, AEROSPACE, AND MEDICAL APPLICATIONS • • • • • • • (1) Controlled Baseline One Assembly/Test Site One Fabrication Site Available in Military (–55°C/125°C) Temperature Range (1) Extended Product Life Cycle Extended Product-Change Notification Product Traceability Consumer: Set-top Box, DVD, LCD Displays Industrial and Car Audio Power Supplies Battery Chargers, High Power LED Supply 12-V/24-V Distributed Power Systems DESCRIPTION As a member of the SWIFT™ family of DC/DC regulators, the TPS5410 is a high-output-current PWM converter that integrates a low resistance high side N-channel MOSFET. Included on the substrate with the listed features is a high performance voltage error amplifier that provides tight voltage regulation accuracy under transient conditions; an undervoltage-lockout circuit to prevent start-up until the input voltage reaches 5.5 V; an internally set slow-start circuit to limit inrush currents; and a voltage feed-forward circuit to improve the transient response. Using the ENA pin, shutdown supply current is reduced to 18 μA typically. Other features include an active high enable, overcurrent limiting, overvoltage protection and thermal shutdown. To reduce design complexity and external component count, the TPS5410 feedback loop is internally compensated. The TPS5410 device is available in an easy to use 8-pin SOIC package. TI provides evaluation modules and software tools to aid in quickly achieving high-performance power supply designs to meet aggressive equipment development cycles. Additional temperature ranges are available - contact factory 1 2 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. SWIFT is a trademark of Texas Instruments. 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 © 2009, Texas Instruments Incorporated TPS5410-EP SLVS910 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com Efficiency vs Output Current Simplified Schematic 100 VIN VIN VOUT PH TPS5410 95 Efficiency − % BOOT NC NC ENA VSENSE 90 85 VI = 20 V VO = 12 V fs = 500 kHz o TA = 25 C GND 80 75 0 0.2 0.4 0.6 0.8 1 1.2 IO - Output Current - A 1.4 These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. ORDERING INFORMATION (1) TJ INPUT VOLTAGE OUTPUT VOLTAGE PACKAGE –55°C to 125°C 5.5 V to 36 V Adjustable to 1.22 V SOIC (D) (1) PART NUMBER TPS5410MDREP For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI web site at www.ti.com. ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range (unless otherwise noted) (1) (2) VALUE BOOT –0.3 to 50 PH (steady-state) VI Input voltage range UNIT –0.3 to 40 (3) VIN –0.6 to 40 (3) EN –0.3 to 7 VSENSE –0.3 to 3 BOOT-PH V 10 PH (transient < 10 ns) –1.2 IO Source current PH Ilkg Leakage current PH 10 μA TJ Operating virtual junction temperature range –55 to 150 °C Tstg Storage temperature –65 to 150 °C (1) (2) (3) 2 Internally Limited 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 or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. All voltage values are with respect to network ground terminal. Approaching the absolute maximum rating for the VIN pin may cause the voltage on the PH pin to exceed the absolute maximum rating. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP TPS5410-EP www.ti.com ......................................................................................................................................................................................... SLVS910 – SEPTEMBER 2009 DISSIPATION RATINGS (1) (2) THERMAL IMPEDANCE JUNCTION-TO-AMBIENT PACKAGE 8 Pin D (1) (2) (3) (3) 75°C/W Maximum power dissipation may be limited by overcurrent protection. Power rating at a specific ambient temperature TA should be determined with a junction temperature of 125°C. This is the point where distortion starts to substantially increase. Thermal management of the final PCB should strive to keep the junction temperature at or below 125°C for best performance and long-term reliability. See Thermal Calculations in applications section of this data sheet for more information. Test board conditions: (a) 3 in x 3 in, 2 layers, thickness: 0.062 inch. (b) 2 oz. copper traces located on the top and bottom of the PCB. RECOMMENDED OPERATING CONDITIONS MIN NOM MAX UNIT VI Input voltage range, VIN 5.5 36 V TJ Operating junction temperature –55 125 °C TYP MAX UNIT 3 4.4 mA 18 50 μA ELECTRICAL CHARACTERISTICS TJ = –55°C to 125°C, VIN = 5.5 V to 36 V (unless otherwise noted) PARAMETER TEST CONDITIONS MIN SUPPLY VOLTAGE (VIN PIN) IQ Quiescent current VSENSE = 2 V, Not switching, PH pin open Shutdown, ENA = 0 V UNDERVOLTAGE LOCK OUT (UVLO) Start threshold voltage, UVLO 5.3 V Hysteresis voltage, UVLO 330 mV VOLTAGE REFERENCE Voltage reference accuracy TJ = 25°C 1.202 1.221 1.239 IO = 0 A – 1 A 1.192 1.221 1.245 TJ = 25°C 400 500 600 TJ = Full range 380 V OSCILLATOR Internally set free-running frequency Minimum controllable on time 600 150 Maximum duty cycle 87% kHz 210 ns 1.3 V 89% ENABLE (ENA PIN) Start threshold voltage, ENA Stop threshold voltage, ENA 0.5 Hysteresis voltage, ENA V 450 Internal slow-start time (0 ~ 100%) mV 5.35 8 10 1.2 1.5 1.8 ms CURRENT LIMIT Current limit TJ = 25°C TJ = Full range Current limit hiccup time 0.45 4.6 22.5 A 13 16 ms 135 162 °C 14 °C THERMAL SHUTDOWN Thermal shutdown trip point Thermal shutdown hysteresis OUTPUT MOSFET rDS(on) High side power MOSFET switch VIN = 5.5 V 150 VIN = 10 V - 36 V 110 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP mΩ 3 TPS5410-EP SLVS910 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com PIN ASSIGNMENTS D PACKAGE (TOP VIEW) BOOT 1 8 PH NC 2 7 VIN NC 3 6 GND VSENSE 4 5 ENA TERMINAL FUNCTIONS TERMINAL NAME DESCRIPTION NO. BOOT 1 NC 2, 3 Boost capacitor for the high-side FET gate driver. Connect 0.01 μF low ESR capacitor from BOOT pin to PH pin. Not connected internally. VSENSE 4 Feedback voltage for the regulator. Connect to output voltage divider. ENA 5 On/off control. Below 0.5 V, the device stops switching. Float the pin to enable. GND 6 Ground. VIN 7 Input supply voltage. Bypass VIN pin to GND pin close to device package with a high quality, low ESR ceramic capacitor. PH 8 Source of the high side power MOSFET. Connected to external inductor and diode. 4 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP TPS5410-EP www.ti.com ......................................................................................................................................................................................... SLVS910 – SEPTEMBER 2009 TYPICAL CHARACTERISTICS OSCILLATOR FREQUENCY vs JUNCTION TEMPERATURE OPERATING QUIESCENT CURRENT vs JUNCTION TEMPERATURE 530 f − Oscillator Frequency − kHz 510 500 490 480 470 460 -50 180 VI = 12 V 170 Minimum Controllable On Time − ns IQ − Operating Quiescent Current − mA 3.5 520 3.25 3 2.75 2.5 -25 0 50 25 75 100 -50 125 -25 0 25 50 75 100 160 150 140 130 120 -50 125 -25 0 50 25 o TJ − Junction Temperature − C o TJ − Junction Temperature − C 75 100 Figure 2. Figure 3. VOLTAGE REFERENCE vs JUNCTION TEMPERATURE ON STATE RESISTANCE vs JUNCTION TEMPERATURE INTERNAL SLOW START TIME vs JUNCTION TEMPERATURE 180 9 VI = 12 V 1.22 1.215 tSS − Internal Slow Start Time − ms rDS(on) − On-State Resistance − mW 170 1.225 125 o TJ − Junction Temperature − C Figure 1. 1.23 Vref − Voltage Reference − V MINIMUM CONTROLLABLE ON TIME vs JUNCTION TEMPERATURE 160 150 140 130 120 110 100 8.5 8 7.5 90 1.21 -50 -25 0 50 25 75 100 125 80 -50 -25 o TJ − Junction Temperature − C 0 25 50 75 -50 -25 0 50 25 75 100 125 o TJ − Junction Temperature − C Figure 5. Figure 6. SHUTDOWN QUIESCENT CURRENT vs INPUT VOLTAGE MINIMUM CONTROLLABLE DUTY RATIO vs JUNCTION TEMPERATURE 8 ENA = 0 V o TJ = 125 C 20 Minimum Duty Ratio − % ISD − Shutdown Current − mA 7 125 TJ − Junction Temperature − C Figure 4. 25 100 o TJ = 27oC 15 10 7.5 7.5 7.25 o TJ = -40 C 5 7 0 5 10 15 20 25 30 35 40 -50 VI − Input Voltage − V -25 0 25 50 75 100 125 o TJ − Junction Temperature − C Figure 7. Figure 8. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP 5 TPS5410-EP SLVS910 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com APPLICATION INFORMATION FUNCTIONAL BLOCK DIAGRAM VIN VIN 1.221 V Bandgap Reference UVLO VREF SHDN Slow Start Boot Regulator BOOT HICCUP 5 µA ENABLE ENA SHDN SHDN VSENSE Z1 Thermal Protection NC SHDN VIN Ramp Generator NC SHDN VSENSE PWM Comparator HICCUP Overcurrent Protection Oscillator OVP Z2 Feed Forward Gain = 25 SHDN GND Error Amplifier SHDN SHDN Gate Drive Control 112.5% VREF Gate Driver SHDN BOOT PH VOUT DETAILED DESCRIPTION Oscillator Frequency The internal free running oscillator sets the PWM switching frequency at 500 kHz. The 500-kHz switching frequency allows less output inductance for the same output ripple requirement resulting in a smaller output inductor. Voltage Reference The voltage reference system produces a precision reference signal by scaling the output of a temperature stable bandgap circuit. The bandgap and scaling circuits are trimmed during production testing to an output of 1.221 V at room temperature. Enable (ENA) and Internal Slow Start The ENA pin provides electrical on/off control of the regulator. Once the ENA pin voltage exceeds the threshold voltage, the regulator starts operation and the internal slow start begins to ramp. If the ENA pin voltage is pulled below the threshold voltage, the regulator stops switching and the internal slow start resets. Connecting the pin to ground or to any voltage less than 0.5 V disables the regulator and activate the shutdown mode. The quiescent current of the TPS5410 in shutdown mode is typically 18 μA. 6 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP TPS5410-EP www.ti.com ......................................................................................................................................................................................... SLVS910 – SEPTEMBER 2009 The ENA pin has an internal pullup current source, allowing the user to float the ENA pin. If an application requires controlling the ENA pin, use open drain or open collector output logic to interface with the pin. To limit the start-up inrush current, an internal slow start circuit is used to ramp up the reference voltage from 0 V to its final value linearly. The internal slow start time is 8 ms typically. Undervoltage Lockout (UVLO) The TPS5410 incorporates an undervoltage lockout circuit to keep the device disabled when VIN (the input voltage) is below the UVLO start voltage threshold. During power up, internal circuits are held inactive and the internal slow start is grouded until VIN exceeds the UVLO start threshold voltage. Once the UVLO start threshold voltage is reached, the internal slow start is released and device start-up begins. The device operates until VIN falls below the UVLO stop threshold voltage. The typical hysteresis in the UVLO comparator is 330 mV. Boost Capacitor (BOOT) Connect a 0.01-μF low-ESR ceramic capacitor between the BOOT pin and PH pin. This capacitor provides the gate drive voltage for the high-side MOSFET. X7R or X5R grade dielectrics are recommended due to their stable values over temperature. Output Feedback (VSENSE) The output voltage of the regulator is set by feeding back the center point voltage of an external resistor divider network to the VSENSE pin. In steady-state operation, the VSENSE pin voltage should be equal to the voltage reference 1.221 V. Internal Compensation The TPS5410 implements internal compensation to simplify the regulator design. Since the TPS5410 uses voltage mode control, a type 3 compensation network has been designed on chip to provide a high crossover frequency and a high phase margin for good stability. See the Internal Compensation Network in the applications section for more details. Voltage Feed Forward The internal voltage feed forward provides a constant DC power stage gain despite any variations with the input voltage. This greatly simplifies the stability analysis and improves the transient response. Voltage feed forward varies the peak ramp voltage inversely with the input voltage so that the modulator and power stage gain are constant at the feed forward gain, i.e. VIN Feed Forward Gain = Ramppk-pk (1) The typical feed forward gain of TPS5410 is 25. Pulse-Width-Modulation (PWM) Control The regulator employs a fixed frequency pulse-width-modulator (PWM) control method. First, the feedback voltage (VSENSE pin voltage) is compared to the constant voltage reference by the high gain error amplifier and compensation network to produce a error voltage. Then, the error voltage is compared to the ramp voltage by the PWM comparator. In this way, the error voltage magnitude is converted to a pulse width which is the duty cycle. Finally, the PWM output is fed into the gate drive circuit to control the on-time of the high-side MOSFET. Overcurrent Liming Overcurrent limiting is implemented by sensing the drain-to-source voltage across the high-side MOSFET. The drain to source voltage is then compared to a voltage level representing the overcurrent threshold limit. If the drain-to-source voltage exceeds the overcurrent threshold limit, the overcurrent indicator is set true. The system will ignore the overcurrent indicator for the leading edge blanking time at the beginning of each cycle to avoid any turn-on noise glitches. Once overcurrent indicator is set true, overcurrent limiting is triggered. The high-side MOSFET is turned off for the rest of the cycle after a propagation delay. The overcurrent limiting scheme is called cycle-by-cycle current limiting. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP 7 TPS5410-EP SLVS910 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com Sometimes under serious overload conditions such as short-circuit, the overcurrent runaway may still happen when using cycle-by-cycle current limiting. A second mode of current limiting is used, i.e. hiccup mode overcurrent limiting. During hiccup mode overcurrent limiting, the voltage reference is grounded and the high-side MOSFET is turned off for the hiccup time. Once the hiccup time duration is complete, the regulator restarts under control of the slow start circuit. Overvoltage Protection The TPS5410 has an overvoltage protection (OVP) circuit to minimize voltage overshoot when recovering from output fault conditions. The OVP circuit includes an overvoltage comparator to compare the VSENSE pin voltage and a threshold of 112.5% x VREF. Once the VSENSE pin voltage is higher than the threshold, the high-side MOSFET will be forced off. When the VSENSE pin voltage drops lower than the threshold, the high-side MOSFET will be enabled again. Thermal Shutdown The TPS5410 protects itself from overheating with an internal thermal shutdown circuit. If the junction temperature exceeds the thermal shutdown trip point, the voltage reference is grounded and the high-side MOSFET is turned off. The part is restarted under control of the slow start circuit automatically when the junction temperature drops 14°C below the thermal shutdown trip point. PCB Layout Connect a low ESR ceramic bypass capacitor to the VIN pin. Care should be taken to minimize the loop area formed by the bypass capacitor connections, the VIN pin, and the TPS5410 ground pin. The best way to do this is to extend the top side ground area from under the device adjacent to the VIN trace, and place the bypass capacitor as close as possible to the VIN pin. The minimum recommended bypass capacitance is 4.7 μF ceramic with a X5R or X7R dielectric. There should be a ground area on the top layer directly underneath the IC to connect the GND pin of the device and the anode of the catch diode. The GND pin should be tied to the PCB ground by connecting it to the ground area under the device as shown in Figure 9. The PH pin should be routed to the output inductor, catch diode and boot capacitor. Since the PH connection is the switching node, the inductor should be located close to the PH pin, and the area of the PCB conductor minimized to prevent excessive capacitive coupling. The catch diode should also be placed close to the device to minimize the output current loop area. Connect the boot capacitor between the phase node and the BOOT pin as shown. Keep the boot capacitor close to the IC and minimize the conductor trace lengths. The component placements and connections shown work well, but other connection routings may also be effective. Connect the output filter capacitor(s) as shown between the VOUT trace and GND. It is important to keep the loop formed by the PH pin, Lout, Cout and GND as small as is practical. Connect the VOUT trace to the VSENSE pin using the resistor divider network to set the output voltage. Do not route this trace too close to the PH trace. Due to the size of the IC package and the device pinout, the trace may need to be routed under the output capacitor. The routing may be done on an alternate layer if a trace under the output capacitor is not desired. If the grounding scheme shown is used via a connection to a different layer to route to the ENA pin. 8 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP TPS5410-EP www.ti.com ......................................................................................................................................................................................... SLVS910 – SEPTEMBER 2009 PH BOOT CAPACITOR OUTPUT INDUCTOR RESISTOR DIVIDER VOUT BOOT PH NC VIN NC GND VSENSE ENA OUTPUT FILTER CAPACITOR Route feedback trace under the output filter capacitor or on the other layer. CATCH DIODE INPUT INPUT BULK BYPASS CAPACITOR FILTER Vin TOPSIDE GROUND AREA VIA to Ground Plane Signal VIA Figure 9. Design Layout Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP 9 TPS5410-EP 0.050 SLVS910 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com 0.026 0.220 0.080 All dimensions in inches Figure 10. TPS5410 Land Pattern Application Circuits Figure 11 shows the schematic for a typical TPS5410 application. The TPS5410 can provide up to 1-A output current at a nominal output voltage of 12 V. U1 TPS5410D 14.5 V - 36 V 7 VIN ENA C1 4.7 mF VIN 5 ENA 2 NC 3 NC 6 GND BOOT L1 68 mH C2 0.01 mF 12 V 1 VOUT PH 8 VSNS 4 + D1 B340A C3 47 mF (See Note A) R1 10 kW R2 1.13 kW A. C3 = Tantalum AVX TPSE476M020R0150 Figure 11. Application Circuit, 14.5-V — 36 V to 12-V 10 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP TPS5410-EP www.ti.com ......................................................................................................................................................................................... SLVS910 – SEPTEMBER 2009 Design Procedure The following design procedure can be used to select component values for the TPS5410. Alternately, see the TI Web site at www.ti.com/swift for any available software tools to aid in the design process. This section presents a simplified discussion of the design process. To • • • • • • begin the design process, a few parameters must be determined. The designer must know the following: Input voltage range Output voltage Input ripple voltage Output ripple voltage Output current rating Operating frequency Design Parameters For this design example, use the following as the input parameters: DESIGN PARAMETER (1) EXAMPLE VALUE Input voltage range (1) 14.5 V to 36 V Output voltage 12 V Input ripple voltage 300 mV Output ripple voltage 50 mV Output current rating 1A Operating frequency 500 kHz As an additional constraint, the design is set up to be small size and low component height. Switching Frequency The switching frequency for the TPS5410 is internally set to 500 kHz. It is not possible to adjust the switching frequency. Input Capacitors The TPS5410 requires an input decoupling capacitor and, depending on the application, a bulk input capacitor. The minimum recommended value for the decoupling capacitor is 4.7 μF. A high quality ceramic type X5R or X7R is required. For some applications, a smaller value decoupling capacitor may be used, if the input voltage and current ripple ratings are not exceeded. The voltage rating must be greater than the maximum input voltage, including ripple. For this design, a 4.7-μF capacitor, C1 issued to allow for smaller 1812 case size to be used while maintaining a 50 V rating. This input ripple voltage can be approximated by Equation 2 : IOUT(MAX) x 0.25 + IOUT(MAX) x ESRMAX DVIN = CBULK x ƒSW ( ) (2) Where IOUT(MAX) is the maximum load current, f SW is the switching frequency, CI is the input capacitor value and ESRMAX is the maximum series resistance of the input capacitor. The maximum RMS ripple current also needs to be checked. For worst case conditions, this is approximated by Equation 3: I OUT(MAX) I + CIN 2 (3) In this example, the calculated input ripple voltage is 137 mV, and the RMS ripple current is 0.5 A. The maximum voltage across the input capacitors would be VIN max plus delta VIN/2. The chosen input decoupling capacitors are rated for 50 V, and the ripple current capacity for each is 3 A at 500 kHz, providing ample margin. The actual measured input ripple voltage may be larger than the calculated value due to the output impedance of the input voltage source, decrease in actual capacitance due to bias voltage and parasitics associated with the layout. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP 11 TPS5410-EP SLVS910 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com The maximum ratings for voltage and current are not to be exceeded under any circumstance. Additionally, some bulk capacitance may be needed, especially if the TPS5410 circuit is not located within approximately 2 inches from the input voltage source. The value for this capacitor is not critical but it should be rated to handle the maximum input voltage including ripple voltage and should filter the output so that input ripple voltage is acceptable. Output Filter Components Two components need to be selected for the output filter, L1 and C3. Since the TPS5410 is an internally compensated device, a limited range of filter component types and values can be supported. Inductor Selection To calculate the minimum value of the output inductor, use Equation 4: LMIN = ( VOUT x VIN(MAX) - VOUT ) VIN(max) x KIND x IOUT x FSW x 0.8 (4) KIND is a coefficient that represents the amount of inductor ripple current relative to the maximum output current. Three things need to be considered when determining the amount of ripple current in the inductor: the peak to peak ripple current affects the output ripple voltage amplitude, the ripple current affects the peak switch current, and the amount of ripple current determines at what point the circuit becomes discontinuous. For designs using the TPS5410, KIND of 0.2 to 0.3 yields good results. Low output ripple voltages is obtained when paired with the proper output capacitor, the peak switch current is below the current limit set point, and low load currents can be sourced before discontinuous operation. For this design example, use KIND = 0.3, and the minimum inductor value is 66 μH. The next highest standard value used in this design is 68 μH. For the output filter inductor, it is important that the RMS current and saturation current ratings not be exceeded. The RMS inductor current can be found from Equation 5: I L(RMS) + Ǹ I2 1 ) OUT(MAX) 12 ǒ V V OUT ǒVIN(MAX) * VOUTǓ L IN(MAX) OUT F SW 0.8 Ǔ 2 (5) and the peak inductor current can be determined using Equation 6: ( ) VOUT x VIN(MAX) - VOUT IL(PK) = IOUT(MAX) + 1.6 x VIN(MAX) x LOUT x FSW (6) For this design, the RMS inductor current is 1.004 A, and the peak inductor current is 1.147 A. The chosen inductor is a Coilcraft MSS1260-683 type. The nominal inductance is 68 μH. It has a saturation current rating of 2.3 A and a RMS current rating of 2.3 A, which meets the requirements. Inductor values for use with the TPS5410 are in the range of 10 μH to 100 μH. Capacitor Selection The important design factors for the output capacitor are dc voltage rating, ripple current rating, and equivalent series resistance (ESR). The dc voltage and ripple current ratings cannot be exceeded. The ESR is important because along with the inductor ripple current it determines the amount of output ripple voltage. The actual value of the output capacitor is not critical, but some practical limits do exist. Consider the relationship between the desired closed loop crossover frequency of the design and LC corner frequency of the output filter. Due to the design of the internal compensation, it is recommended to keep the closed loop crossover frequency in the range 3 kHz to 30 kHz as this frequency range has adequate phase boost to allow for stable operation. For this design example, the intended closed loop crossover frequency is between 2590 Hz and 24 kHz, and below the ESR zero of the output capacitor. Under these conditions, the closed loop crossover frequency is related to the LC corner frequency as: 12 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP TPS5410-EP www.ti.com ......................................................................................................................................................................................... SLVS910 – SEPTEMBER 2009 f CO + f LC 2 85 VOUT (7) and the desired output capacitor value for the output filter to: 1 C OUT + 3357 L OUT f CO V OUT (8) For a desired crossover of 10 kHz and a 68-μH inductor, the calculated value for the output capacitor is 36.5 μF. The capacitor type should be chosen so that the ESR zero is above the loop crossover. The maximum ESR is: 1 ESR MAX + 2p C OUT f CO (9) The maximum ESR of the output capacitor also determines the amount of output ripple as specified in the initial design parameters. The output ripple voltage is the inductor ripple current times the ESR of the output filter. Check that the maximum specified ESR as listed in the capacitor data sheet results in an acceptable output ripple voltage: VPP(MAX) = ( ) ESRMAX x VOUT x VIN(MAX) - VOUT NC x VIN(MAX) x LOUT x FSW x 0.8 (10) Where: ΔVPP is the desired peak-to-peak output ripple. NC is the number of parallel output capacitors. FSW is the switching frequency. The minimum ESR of the output capacitor should also be considered. For a good phase margin, if the ESR is zero when the ESR is at its minimum, it should not be above the internal compensation poles at 24 kHz and 54 kHz. The selected output capacitor must also be rated for a voltage greater than the desired output voltage plus one half the ripple voltage. Any derating amount must also be included. The maximum RMS ripple current in the output capacitor is given by Equation 11: ICOUT(RMS) = 1 Ö12 x [ ( VOUT x VIN(MAX) - VOUT ) VIN(MAX) x LOUT - FSW x 0.8 x NC ] (11) Where: NC is the number of output capacitors in parallel. FSW is the switching frequency. For this design example, a single 47-μF output capacitor is chosen for C3. This value is close to the calculated value of 36.5 μF and yields an actual closed loop cross over frequency of 10.05 kHz. The calculated RMS ripple current is 84.9 mA and the maximum ESR required is 339 mΩ. A capacitor that meets these requirements is a AVX TPSE476M020R0150, rated at 20 V with a maximum ESR of 150 mΩ and a ripple current rating of 1.369 A. This capacitor results in a peak-to-peak output ripple of 44 mV using equation 10. An additional small 0.1-μF ceramic bypass capacitor may also used, but is not included in this design. Other capacitor types can be used with the TPS5410, depending on the needs of the application. Output Voltage Setpoint The output voltage of the TPS5410 is set by a resistor divider (R1 and R2) from the output to the VSENSE pin. Calculate the R2 resistor value for the output voltage of 12 V using Equation 12: Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP 13 TPS5410-EP SLVS910 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com R2 + R1 V OUT 1.221 * 1.221 (12) For any TPS5410 design, start with an R1 value of 10 kΩ. R2 is then 1.13 kΩ. Boot Capacitor The boot capacitor should be 0.01 μF. Catch Diode The TPS5410 is designed to operate using an external catch diode between PH and GND. The selected diode must meet the absolute maximum ratings for the application: Reverse voltage must be higher than the maximum voltage at the PH pin, which is VINMAX + 0.5 V. Peak current must be greater than IOUTMAX plus on half the peak-to-peak inductor current. Forward voltage drop should be small for higher efficiencies. It is important to note that the catch diode conduction time is typically longer than the high-side FET on time; therefore, the diode parameters improve the overall efficiency. Additionally, check that the device chosen is capable of dissipating the power losses. For this design, a Diodes, Inc. B340A is chosen, with a reverse voltage of 40 V, forward current of 3 A, and a forward voltage drop of 0.5 V. Additional Circuits Figure 12 shows an application circuit using all ceramic capacitors for the input and output filters. The design procedure is similar to those given for the design example, except for the selection of the output filter capacitor values and the design of the additional compensation components required to stabilize the circuit. U1 TPS5410D 7 V - 36 V VIN 7 ENA C1 4.7 mF C2 0.01 mF VIN 5 ENA 2 NC 3 NC 6 GND BOOT L1 68 mH 5V 1 VOUT PH 8 VSNS 4 D1 B340A C3 47 mF C4 47 mF (Note A) (Note A) R1 10 kW C6 2700 pF R3 1.78 kW C5 150 pF A. R2 3.24 kW C7 0.056 mF C3, C4 = Ceramic TDKC4532X5R1A476MT Figure 12. 7-V — 36-V Input to 5-V Output Application Circuit with Ceramic Capacitors Output Filter Capacitor Selection When using ceramic output filer capacitors, the recommended LC resonant frequency should be no more than 7 kHz. Since the output inductor is already selected at 68 μH, this limits the minimum output capacitor value to: 1 CO (MIN) ³ 2 (2p x 7000) x LO (13) The minimum capacitor value is calculated to be 7.6 μF. For this circuit a larger value of capacitor will yield better transient response. Two output capacitors are used for C3 and C4 with a value of 47 uF each. It is important to note that the actual capacitance of ceramic capacitors decreases with applied voltage. In this case the effective value used for the calculations is approximately 70 % of the rated value or 70 μF. 14 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP TPS5410-EP www.ti.com ......................................................................................................................................................................................... SLVS910 – SEPTEMBER 2009 External Compensation Network When using ceramic output capacitors, additional circuitry is required to stabilize the closed loop system. For this circuit the external components are R3, C5, C6 and C7. To determine the value of these components, first calculate the LC resonant frequency of the output filter: 1 FLC = 2p Ö LO x CO (EFF) (14) For this example the effective resonant frequency is calculated as 2306 Hz The network composed of R1, R2, R3, C5, C6 and C7 has two poles and two zeros that are used to tailor the overall response of the feedback network to accommodate the use of the ceramic output capacitors. The pole and zero locations are given by the following equations: VO Fp1 = 500000 x FLC (15) Fz1 = 0.7 x FLC (16) Fz2 = 2.5 x FLC (17) The final pole is located at a frequency too high to be of concern. The values for R1 and R2 are fixed by the 5-V output voltage as calculated using Equation 12. Now the values of R3, C5, C6 and C7 are determined using Equation 18, Equation 19, and Equation 20: 1 C7 = 2p x Fp1 x (R1 || R2) (18) 1 2p x Fz1 x C7 1 C6 = 2p x Fz2 x R1 R3 = (19) (20) For this design, using the closest standard values, C7 is 0.056 μF, R3 is 1.76 kΩ and C6 is 2700 pF. C5 is added to improve load regulation performance. It is effectively in parallel with C6 in the location of the second pole frequency, so it should be small in relationship to C6. C5 should be less the 1/10 the value of C6. For this example, 150 pF works well. For additional information on external compensation of the TPS5410 or other wide voltage range SWIFT devices, see SLVA237 Using TPS5410/20/30/31 With Aluminum/Ceramic Output Capacitors. Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP 15 TPS5410-EP SLVS910 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com ADVANCED INFORMATION Output Voltage Limitations Due to the internal design of the TPS5410, there are both upper and lower output voltage limits for any given input voltage. The upper limit of the output voltage set point is constrained by the maximum duty cycle of 87% and is given by: V OUTMAX + 0.87 ǒǒVINMIN * I OMAX Ǔ Ǔ ǒ 0.230 ) VD * I OMAX Ǔ RL * VD (21) Where: VINMIN = minimum input voltage IOMAX = maximum load current VD = catch diode forward voltage. RL= output inductor series resistance. This equation assumes maximum on resistance for the internal high side FET. The lower limit is constrained by the minimum controllable on time which may be as high as 200 ns. The approximate minimum output voltage for a given input voltage and minimum load current is given by: V OUTMIN + 0.12 ǒǒVINMAX * I OMIN Ǔ Ǔ ǒ 0.110 ) VD * I OMIN Ǔ RL * VD (22) Where: VINMAX = maximum input voltage IOMIN = minimum load current VD = catch diode forward voltage. RL= output inductor series resistance. This equation assumes nominal on resistance for the high side FET and accounts for worst case variation of operating frequency set point. Any design operating near the operational limits of the device should be checked to assure proper functionality. Internal Compensation Network The design equations given in the example circuit can be used to generate circuits using the TPS5410. These designs are based on certain assumptions, and always select output capacitors within a limited range of ESR values. If a different capacitor type is desired, it may be possible to fit one to the internal compensation of the TPS5410. Equation 23 gives the nominal frequency response of the internal voltage-mode type III compensation network: s s 1) 1) 2p Fz1 2p Fz2 H(s) + s s s s 1) 1) 1) 2p Fp1 2p Fp2 2p Fp3 2p Fp0 (23) ǒ ǒ Ǔ ǒ Ǔ ǒ Ǔ ǒ Ǔ Ǔ ǒ Ǔ Where Fp0 = 2165 Hz, Fz1 = 2170 Hz, Fz2 = 2590 Hz Fp1 = 24 kHz, Fp2 = 54 kHz, Fp3 = 440 kHz Fp3 represents the non-ideal parasitics effect. Using this information along with the desired output voltage, feed forward gain and output filter characteristics, the closed loop transfer function can be derived. 16 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP TPS5410-EP www.ti.com ......................................................................................................................................................................................... SLVS910 – SEPTEMBER 2009 Thermal Calculations The following formulas show how to estimate the device power dissipation under continuous conduction mode operations. They should not be used if the device is working at light loads in the discontinuous conduction mode. Conduction Loss: Pcon = IOUT 2 x Rds(on) x VOUT / VIN Switching Loss: Psw = VIN x IOUT x 0.01 Quiescent Current Loss: Pq = VIN x 0.01 Total Loss: Ptot = Pcon + Psw + Pq Given TA => Estimated Junction Temperature: TJ = TA + Rth x Ptot Given TJMAX = 125°C => Estimated Maximum Ambient Temperature: TAMAX = TJMAX – Rth x Ptot PERFORMANCE GRAPHS The performance graphs in Figure 13 - Figure 20 are applicable to the circuit in Figure 11. TA = 25 °C. unless otherwise specified. 0.03 100 VI = 14.5 V VI = 20 V 0.03 VI = 14.5 V 0.02 0.02 90 VI = 30 V VI = 35 V 85 VI = 25 V 80 VI = 20 V 0.01 Output Voltage Regulation - % Output Voltage Regulation - % Efficiency - % 95 VI = 25 V 0 VI = 30 V -0.01 VI = 36 V 0 0.2 0.4 0.6 0.8 1 IO - Output Current - A 1.2 1.4 Figure 13. Efficiency vs. Output Current VIN = 100 mV/div (AC Coupled) AC Coupled 20 MHz BWL -0.03 0 IO = 0 A 0 -0.01 IO = 1 A -0.02 -0.02 75 IO = 0.5 A 0.01 0.2 0.4 0.6 0.8 1 1.2 -0.03 14 16 18 Figure 14. Output Voltage Regulation % vs. Output Current VIN = 20 mV/div (AC Coupled) 20 22 24 26 28 30 32 34 36 VI - Input Voltage - V IO - Output Current - A Figure 15. Output Voltage Regulation % vs. Input Voltage AC Coupled 20 MHz BWL AC Coupled 20 MHz BWL VO = 100 mV/div V(PH) = 10 V/div V(PH) = 10 V/div IO = 500 mA/div t - Time - 1 ms / Div Figure 16. Input Voltage Ripple and PH Node, IO = 1 A t - Time - 1 ms / Div Figure 17. Output Voltage Ripple and PH Node, IO = 1 A t - Time - 200 ms / Div Figure 18. Transient Response, IO Step 0.25 to 0.75 A Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP 17 TPS5410-EP SLVS910 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com VI = 10 V/div ENA = 2 V/div VO = 5 V/div VO = 5 V/div t - Time - 5 ms / Div t - Time - 5 ms / Div Figure 19. Startup Waveform, VI and VO Figure 20. Startup Waveform, ENA and VO PERFORMANCE GRAPHS The performance graphs in Figure 21 - Figure 26 are applicable to the circuit in Figure 12. TA = 25 °C. unless otherwise specified. 0.1 100 0.08 VI = 15 V Efficiency - % 95 90 85 VI = 30 V 80 VI = 35 V 0.2 0.4 0.6 0.8 1 IO - Output Current - A 1.2 1.4 Figure 21. Efficiency vs. Output Current 18 0.04 VI = 7 V 0.02 0 -0.02 VI = 25 V -0.04 VI = 30 V VI = 36 V -0.06 IO = 0.5 A 0.01 IO = 0 A 0 -0.01 IO = 1 A -0.02 -0.08 VI = 20 V 0 0.02 VI = 15 V 0.06 VI = 20 V VI = 25 V 75 0.03 VI = 10 V Output Voltage Regulation - % VI = 10 V Output Voltage Regulation - % VI = 7 V -0.1 0 0.2 0.4 0.6 0.8 1 1.2 IO - Output Current - A Figure 22. Output Voltage Regulation % vs. Output Current Submit Documentation Feedback -0.03 14 16 18 20 22 24 26 28 30 32 34 36 VI - Input Voltage - V Figure 23. Output Voltage Regulation % vs. Input Voltage Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP TPS5410-EP www.ti.com ......................................................................................................................................................................................... SLVS910 – SEPTEMBER 2009 VIN = 100 mV/div (AC Coupled) AC Coupled 20 MHz BWL VIN = 20 mV/div (AC Coupled) AC Coupled 20 MHz BWL AC Coupled 20 MHz BWL VO = 100 mV/div V(PH) = 10 V/div V(PH) = 10 V/div IO = 500 mA/div t - Time - 1 ms / Div Figure 24. Input Voltage Ripple and PH Node, IO = 1 A t - Time - 1 ms / Div Figure 25. Output Voltage Ripple and PH Node, IO = 1 A t - Time - 200 ms / Div Figure 26. Transient Response, IO Step 0.25 to 0.75 A Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated Product Folder Link(s): TPS5410-EP 19 PACKAGE OPTION ADDENDUM www.ti.com 1-Oct-2009 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TPS5410MDREP ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR V62/09645-01XE ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR 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. 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OTHER QUALIFIED VERSIONS OF TPS5410-EP : • Catalog: TPS5410 NOTE: Qualified Version Definitions: • Catalog - TI's standard catalog product Addendum-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 26-Sep-2009 TAPE AND REEL INFORMATION *All dimensions are nominal Device TPS5410MDREP Package Package Pins Type Drawing SOIC D 8 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2500 330.0 12.4 Pack Materials-Page 1 6.4 B0 (mm) K0 (mm) P1 (mm) 5.2 2.1 8.0 W Pin1 (mm) Quadrant 12.0 Q1 PACKAGE MATERIALS INFORMATION www.ti.com 26-Sep-2009 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) TPS5410MDREP SOIC D 8 2500 346.0 346.0 29.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. 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