Typical Size (6,3 mm x 6,4 mm) TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 3-V TO 6-V INPUT, 3-A OUTPUT SYNCHRONOUS-BUCK PWM SWITCHER WITH INTEGRATED FETs (SWIFT) FEATURES D 60-mΩ MOSFET Switches for High Efficiency D D D D D D DESCRIPTION As members of the SWIFT family of dc/dc regulators, the TPS54311, TPS54312, TPS54313, TPS54314, TPS54315 and TPS54316 low-input-voltage high-outputcurrent synchronous-buck PWM converters integrate all required active components. Included on the substrate with the listed features are a true, high performance, voltage error amplifier that provides high performance under transient conditions; an undervoltage-lockout circuit to prevent start-up until the input voltage reaches 3 V; an internally and externally set slow-start circuit to limit in-rush currents; and a power good output useful for processor/logic reset, fault signaling, and supply sequencing. at 3-A Continuous Output Source or Sink Current 0.9-V, 1.2-V, 1.5-V, 1.8-V, 2.5-V and 3.3-V Fixed Output Voltage Devices With 1% Initial Accuracy Internally Compensated for Low Parts Count Fast Transient Response Wide PWM Frequency: Fixed 350 kHz, 550 kHz, or Adjustable 280 kHz to 700 kHz Load Protected by Peak Current Limit and Thermal Shutdown Integrated Solution Reduces Board Area and Total Cost The TPS54311, TPS54312, TPS54313, TPS54314, TPS54315 and TPS54316 devices are available in a thermally enhanced 20-pin TSSOP (PWP) PowerPAD package, which eliminates bulky heatsinks. TI provides evaluation modules and the SWIFT designer software tool to aid in quickly achieving high-performance power supply designs to meet aggressive equipment development cycles. APPLICATIONS D Low-Voltage, High-Density Systems With Power Distributed at 5 V or 3.3 V D Point of Load Regulation for High D D Performance DSPs, FPGAs, ASICs, and Microprocessors Broadband, Networking and Optical Communications Infrastructure Portable Computing/Notebook PCs EFFICIENCY vs LOAD CURRENT Simplified Schematic Input VIN PH 96 94 Output 92 BOOT PGND VBIAS VSENSE GND Efficiency – % TPS54316 90 88 86 84 TA = 25°C VI = 5 V VO = 3.3 V 82 80 0 0.5 1 1.5 2 2.5 3 Load Current – A 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. PowerPAD and SWIFT are trademarks of Texas Instruments. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright 2002 – 2003, Texas Instruments Incorporated TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 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 OUTPUT VOLTAGE TA –40°C –40 C to 85 85°C C PACKAGED DEVICES PLASTIC HTSSOP (PWP)(1) 0.9 V TPS54311PWP 1.2 V TPS54312PWP TA –40°C –40 C to 85 85°C C OUTPUT VOLTAGE PACKAGED DEVICES PLASTIC HTSSOP (PWP)(1) 1.8 V TPS54314PWP 2.5 V TPS54315PWP 1.5 V TPS54313PWP 3.3 V TPS54316PWP (1) The PWP package is also available taped and reeled. Add an R suffix to the device type (i.e., TPS54316PWPR). See application section of data sheet for PowerPAD drawing and layout information. ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range unless otherwise noted(1) TPS54310 Input voltage range, VI Output voltage range, VO Source current, IO VIN, SS/ENA, SYNC –0.3 V to 7 V RT –0.3 V to 6 V VSENSE –0.3 V to 4 V BOOT –0.3 V to 17 V VBIAS, PWRGD, COMP –0.3 V to 7 V PH –0.6 V to 10 V PH Internally Limited COMP, VBIAS 6 mA PH Sink current Voltage differential 6A COMP 6 mA SS/ENA,PWRGD 10 mA ±0.3 V AGND to PGND Operating virtual junction temperature range, TJ –40°C to 125°C Storage temperature, Tstg –65°C to 150°C Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 300°C (1) 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. RECOMMENDED OPERATING CONDITIONS MIN Input voltage range, VI Operating junction temperature, TJ NOM MAX UNIT 3 6 V –40 125 °C PACKAGE DISSIPATION RATINGS(1) (2) PACKAGE THERMAL IMPEDANCE JUNCTION-TO-AMBIENT TA = 25°C POWER RATING TA = 70°C POWER RATING TA = 85°C POWER RATING 20-Pin PWP with solder 26.0°C/W 3.85 W(3) 2.12 W 1.54 W 20-Pin PWP without solder 57.5°C/W 1.73 W 0.96 W 0.69 W (1) For more information on the PWP package, refer to TI technical brief (SLMA002). (2) Test board conditions: 1. 3” × 3”, 2 layers, Thickness: 0.062” 2. 1.5 oz copper traces located on the top of the PCB 3. 1.5 oz copper ground plane on the bottom of the PCB 4. Ten thermal vias (see recommended land pattern in application section of this data sheet) (3) Maximum power dissipation may be limited by overcurrent protection. 2 TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 ELECTRICAL CHARACTERISTICS TJ = –40°C to 125°C, VIN = 3 V to 6 V (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX 6.2 9.6 8.4 12.8 1 1.4 2.95 3 UNIT SUPPLY VOLTAGE, VIN VIN input voltage range 3 Quiescent current fs = 350 kHz, fs = 550 kHz, Phase pin open FSEL = 0.8 V, RT open FSEL ≥ 2.5 V, RT open, Shutdown, SS/ENA = 0 V 6 V mA UNDER VOLTAGE LOCK OUT Start threshold voltage, UVLO V Stop threshold voltage, UVLO 2.70 2.80 Hysteresis voltage, UVLO 0.14 0.16 V 2.5 µs Rising and falling edge deglitch, UVLO(1) BIAS VOLTAGE Output voltage, VBIAS Output current, VBIAS(2) I(VBIAS) = 0 2.70 2.80 2.90 V 100 µA OUTPUT VOLTAGE VO TPS54311 TJ = 25°C, 3 ≤ VIN ≤ 6 V, VIN = 5 V TPS54312 TJ = 25°C, 3 ≤ VIN ≤ 6 V, VIN = 5 V TPS54313 TJ = 25°C, 3 ≤ VIN ≤ 6 V, VIN = 5 V TPS54314 TJ = 25°C, 3 ≤ VIN ≤ 6 V, VIN = 5 V TPS54315 TJ = 25°C, 3 ≤ VIN ≤ 6 V, VIN = 5 V TPS54316 TJ = 25°C, 3 ≤ VIN ≤ 6 V, VIN = 5 V Output voltage 0 ≤ IL ≤ 3 A, 0.9 V –40 ≤ TJ ≤ 125 –2.5% –40 ≤ TJ ≤ 125 –2.5% –40 ≤ TJ ≤ 125 –2.5% –40 ≤ TJ ≤ 125 –2.5% –40 ≤ TJ ≤ 125 –2.5% 0 ≤ IL ≤ 3 A, –40 ≤ TJ ≤ 125 –2.5% IL = 1.5 A, IL = 0 A to 3 A, 350 ≤ fs ≤ 550 kHz, TJ = 85°C TJ = 85°C FSEL ≤ 0.8 V, RT open 280 350 420 FSEL ≥ 2.5 V, RT open 440 550 660 RT = 180 kΩ (1% resistor to AGND)(1) 252 280 308 RT = 100 kΩ (1% resistor to AGND) RT = 68 kΩ (1% resistor to AGND)(1) 460 500 540 663 700 762 0 ≤ IL ≤ 3 A, 0 ≤ IL ≤ 3 A, 0 ≤ IL ≤ 3 A, 0 ≤ IL ≤ 3 A, 2.5% 1.2 V 2.5% 1.5 V 2.5% 1.8 V 2.5% 2.5 V 2.5% 3.3 V 2.5% REGULATION Line regulation(1) (3) Load regulation (1) (3) 350 ≤ fs ≤ 550 kHz, 0.21 %/V 0.21 %/A OSCILLATOR Internally set free-running frequency range Externally set free-running frequency range High-level threshold voltage at FSEL 2.5 Low-level threshold voltage at FSEL Ramp valley(1) 0.75 Maximum duty cycle (1) Specified by design (2) Static resistive loads only (3) Specified by the circuit used in Figure 10. V V 1 Minimum controllable on time(1) kHz V 0.8 Ramp amplitude (peak-to-peak)(1) kHz V 200 ns 90% 3 TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 ELECTRICAL CHARACTERISTICS (continued) TJ = –40°C to 125°C, VIN = 3 V to 6 V (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT ERROR AMPLIFIER Error amplifier open loop voltage gain(1) Error amplifier unity gain bandwidth(1) 3 26 dB 5 MHz PWM COMPARATOR PWM comparator propagation delay time, PWM comparator input to PH pin (excluding dead time) 10 mV overdrive(1) 70 85 ns 1.20 1.40 V SLOW-START/ENABLE Enable threshold voltage, SS/ENA 0.82 Enable hysteresis voltage, SS/ENA(1) Falling edge deglitch, SS/ENA(1) Internal slow-start time(1) 0.03 V 2.5 µs TPS54311 2.6 3.3 4.1 TPS54312 3.5 4.5 5.4 TPS54313 4.4 5.6 6.7 TPS54314 2.6 3.3 4.1 TPS54315 3.6 4.7 5.6 TPS54316 4.7 6.1 7.6 3 5 8 µA 1.5 2.3 4 mA Charge current, SS/ENA SS/ENA = 0 V Discharge current, SS/ENA SS/ENA = 0.2 V, VI = 1.5 V ms POWER GOOD Power good threshold voltage VSENSE falling 90 Power good hysteresis voltage(1) Power good falling edge deglitch(1) Output saturation voltage, PWRGD Leakage current, PWRGD %Vref %Vref 3 µs 35 I(sink) = 2.5 mA VI = 5.5 V 0.18 0.30 V 1 µA CURRENT LIMIT Current limit trip point VI = 3 V, output shorted(1) VI = 6 V, output shorted(1) Current limit leading edge blanking time (1) 100 ns Current limit total response time (1) 200 ns 4 6.5 4.5 7.5 A THERMAL SHUTDOWN Thermal shutdown trip point(1) Thermal shutdown hysteresis(1) 135 150 165 °C °C 10 OUTPUT POWER MOSFETS rDS(on) Power MOSFET switches VI = 6 V(2) VI = 3 V(2) (1) Specified by design (2) Matched MOSFETs, low side rDS(on) production tested, high side rDS(on) specified by design 4 59 88 85 136 mΩ Ω TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 PIN ASSIGNMENTS PWP PACKAGE (TOP VIEW) AGND VSENSE NC PWRGD BOOT PH PH PH PH PH 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 RT FSEL SS/ENA VBIAS VIN VIN VIN PGND PGND PGND NC – No internal connection Terminal Functions TERMINAL NAME DESCRIPTION NO. AGND 1 Analog ground. Return for compensation network/output divider, slow-start capacitor, VBIAS capacitor, RT resistor and FSEL pin. Make PowerPAD connection to AGND. BOOT 5 Bootstrap input. 0.022-µF to 0.1-µF low-ESR capacitor connected from BOOT to PH generates floating drive for the high-side FET driver. FSEL 19 Frequency select input. Provides logic input to select between two internally set switching frequencies. 3 No connection NC PGND 11–13 Power ground. High current return for the low-side driver and power MOSFET. Connect PGND with large copper areas to the input and output supply returns, and negative terminals of the input and output capacitors. PH 6–10 Phase input/output. Junction of the internal high and low-side power MOSFETs, and output inductor. PWRGD 4 Power good open drain output. Hi-Z when VSENSE ≥ 90% Vref, otherwise PWRGD is low. Note that output is low when SS/ENA is low or internal shutdown signal active. RT 20 Frequency setting resistor input. Connect a resistor from RT to AGND to set the switching frequency, fs. SS/ENA 18 Slow-start/enableinput/output. Dual function pin which provides logic input to enable/disable device operation and capacitor input to externally set the start-up time. VBIAS 17 Internal bias regulator output. Supplies regulated voltage to internal circuitry. Bypass VBIAS pin to AGND pin with a high quality, low ESR 0.1-µF to 1.0-µF ceramic capacitor. 14–16 Input supply for the power MOSFET switches and internal bias regulator. Bypass VIN pins to PGND pins close to device package with a high quality, low ESR 1-µF to 10-µF ceramic capacitor. VIN VSENSE 2 Error amplifier inverting input. Connect directly to output voltage sense point. 5 TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 FUNCTIONAL BLOCK DIAGRAM AGND VBIAS VIN Enable 5 µA Comparator SS/ENA Falling Edge Deglitch 1.2 V Hysteresis: 0.03 V VIN UVLO Comparator VIN 2.95 V Hysteresis: 0.16 V VIN ILIM Comparator Thermal Shutdown 145°C 2.5 µs REG VBIAS SHUTDOWN VIN Leading Edge Blanking Falling and Rising Edge Deglitch 100 ns BOOT 2.5 µs SS_DIS SHUTDOWN Internal/External Slow-Start (Internal Slow-Start Time = 3.3 ms to 6.6 ms) VI PH + – 2 kΩ S 40 kΩ Error Amplifier VI Feed-Forward Compensation PWM Comparator 25 ns Adaptive Deadtime VIN OSC PGND Power good Comparator Reference/ DAC Falling Edge Deglitch VSENSE 0.90 Vref Hysteresis: 0.03 Vref TPS5431x VSENSE 6 CO Adaptive Dead-Time and Control Logic R Q LOUT RT FSEL SHUTDOWN 35 µs PWRGD VO TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 TYPICAL CHARACTERISTICS DRAIN-SOURCE ON-STATE RESISTANCE vs JUNCTION TEMPERATURE 100 IO = 3 A 80 60 40 20 VI = 5 V 0 25 85 IO = 3 A 80 60 40 20 0 –40 0 –40 125 TJ – Junction Temperature – °C 0 25 125 600 RT = 100 k 500 400 RT = 180 k 300 0.893 0.891 0.889 0.887 –80 –120 Gain 20 –140 –160 0 –180 –20 –200 10 k 100 k 1 M 10 M 0 10 100 1k f – Frequency – Hz Figure 7 Internal Slow-Start Time – ms –40 –100 40 0.8890 f = 350 kHz 0.8870 0 25 85 3 125 4 5 VI – Input Voltage – V 6 Figure 6 DEVICE POWER LOSSES vs LOAD CURRENT 3.80 2.25 3.65 2 –20 –60 60 0.8910 INTERNAL SLOW-START TIME vs JUNCTION TEMPERATURE Phase – Degrees RL= 10 kΩ, CL = 160 pF, TA = 25°C 125 TA = 85°C Figure 5 0 140 85 0.8930 TJ – Junction Temperature – °C ERROR AMPLIFIER OPEN LOOP RESPONSE 25 0.8850 0.885 –40 125 Figure 4 Phase 0 0.8950 TJ – Junction Temperature – °C 80 250 –40 Device Power Losses – W 85 100 350 OUTPUT VOLTAGE REGULATION vs INPUT VOLTAGE VO – Output Voltage Regulation – V Vref – Voltage Reference – V 700 120 FSEL ≤ 0.8 V Figure 3 0.895 25 450 TJ – Junction Temperature – °C RT = 68 k 0 FSEL ≥ 2.5 V 550 VOLTAGE REFERENCE vs JUNCTION TEMPERATURE 800 200 –40 650 Figure 2 EXTERNALLY SET OSCILLATOR FREQUENCY vs JUNCTION TEMPERATURE f – Externally Set Oscillator Frequency – kHz 85 750 TJ – Junction Temperature – °C Figure 1 Gain – dB f – Internally Set Oscillator Frequency –kHz 100 Drain-Source On-State Resistance – Ω Drain-Source On-State Resistance – Ω 120 VI = 3.3 V INTERNALLY SET OSCILLATOR FREQUENCY vs JUNCTION TEMPERATURE DRAIN-SOURCE ON-STATE RESISTANCE vs JUNCTION TEMPERATURE 3.50 3.35 3.20 3.05 TJ – 125°C, fs = 700 kHz 1.75 1.5 VI = 3.3 V 1.25 1 VI = 5 V 0.75 0.5 2.90 0.25 2.75 –40 0 25 85 TJ – Junction Temperature – °C Figure 8 125 0 0 1 2 3 IL – Load Current – A 4 Figure 9 7 TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 APPLICATION INFORMATION Figure 10 shows the schematic diagram for a typical TPS54314 application. The TPS54314 (U1) can provide up to 3 A of output current at a nominal output voltage of J1 VI 2 + 1 GND C2 R1 10 kΩ 1 PWRGD L1 5.2 µH J3 2 GND C11 1000 pF 1 C7 0.047 µF 1 VO 1.8 V. For proper thermal performance, the PowerPAD underneath the TPS54314 integrated circuit needs to be soldered to the printed circuit board. + C9 470 µF 4V U1 TPS54314PWP 1 AGND RT 2 VSENSE FSEL 3 SS/ENA NC 4 PWRGD VBIAS 5 BOOT VIN 6 PH VIN 7 PH VIN 8 PH PGND 9 PGND PH 10 PH PGND PwrPAD 20 R7 19 71.5 kΩ 18 17 16 15 14 13 C8 10 µF C3 0.1 µF 12 11 Optional Figure 10. TPS54314 Schematic INPUT VOLTAGE The input to the circuit is a nominal 5 VDC, applied at J1. The optional input filter (C2) is a 220-µF POSCAP capacitor, with a maximum allowable ripple current of 3 A. C8 is the decoupling capacitor for the TPS54314 and must be located as close to the device as possible. FEEDBACK CIRCUIT The output voltage of the converter is fed directly into the VSENSE pin of the TPS54314. The TPS54314 is internally compensated to provide stability of the output under varying line and load conditions. OPERATING FREQUENCY In the application circuit, a 700 kHz operating frequency is selected by leaving FSEL open and connecting a 71.5 kΩ resistor between the RT pin and AGND. Different operating frequencies may be selected by varying the value of R3 using equation 1: R+ 500 kHz Switching Frequency 100 kW (1) Alternately, preset operating frequencies of 350 kHz or 550 kHz my be selected by leaving RT open and connecting the FSEL pin to AGND or VIN respectively. OUTPUT FILTER The output filter is composed of a 5.2-µH inductor and 470-µF capacitor. The inductor is a low dc resistance (16-mΩ) type, Sumida CDRH104R–5R2. The capacitor used is a 4-V POSCAP with a maximum ESR of 40 mΩ. 8 The output filter components work with the internal compensation network to provide a stable closed loop response for the converter. GROUNDING AND PowerPAD LAYOUT The TPS54311–16 have two internal grounds (analog and power). Inside the TPS54311–16, the analog ground ties to all of the noise sensitive signals, while the power ground ties to the noisier power signals. The PowerPAD must be connected directly to AGND. Noise injected between the two grounds can degrade the performance of the TPS54311–16, particularly at higher output currents. However, ground noise on an analog ground plane can also cause problems with some of the control and bias signals. For these reasons, separate analog and power ground planes are recommended. These two planes should tie together directly at the IC to reduce noise between the two grounds. The only components that should tie directly to the power ground plane are the input capacitor, the output capacitor, the input voltage decoupling capacitor, and the PGND pins of the TPS54311–16. The layout of the TPS54314 evaluation module is representative of a recommended layout for a 4-layer board. Documentation for the TPS54314 evaluation module can be found on the Texas Instruments web site under the TPS54314 product folder and in the application note, TI literature number SLVA111. LAYOUT CONSIDERATIONS FOR THERMAL PERFORMANCE For operation at full rated load current, the analog ground plane must provide adequate heat dissipating area. A 3 inch by 3 inch plane of 1 ounce copper is recommended, TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 though not mandatory, depending on ambient temperature and airflow. Most applications have larger areas of internal ground plane available, and the PowerPAD should be connected to the largest area available. Additional areas on the top or bottom layers also help dissipate heat, and any area available should be used when 3 A or greater operation is desired. Connection from the exposed area of the PowerPAD to the analog ground plane layer should be 6 PL ∅ 0.0130 4 PL ∅ 0.0180 Connect Pin 1 to Analog Ground Plane in This Area for Optimum Performance 0.0227 0.0600 0.0400 0.2560 0.2454 0.0400 0.0600 Minimum Recommended Top Side Analog Ground Area made using 0.013 inch diameter vias to avoid solder wicking through the vias. Six vias should be in the PowerPAD area with four additional vias located under the device package. The size of the vias under the package, but not in the exposed thermal pad area, can be increased to 0.018. Additional vias beyond the ten recommended that enhance thermal performance should be included in areas not under the device package. Minimum Recommended Thermal Vias: 6 × .013 dia. Inside Powerpad Area 4 × .018 dia. Under Device as Shown. Additional .018 dia. Vias May be Used if Top Side Analog Ground Area is Extended. ÓÓÓ ÓÓÓ ÓÓÓ ÓÓÓ ÓÓÓ ÓÓÓ 0.0150 0.06 0.1010 0.0256 0.1700 0.1340 0.0620 0.0400 Minimum Recommended Exposed Copper Area For Powerpad. 5mm Stencils may Require 10 Percent Larger Area Figure 11. Recommended Land Pattern for 20-Pin PWP PowerPAD 9 TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 PERFORMANCE GRAPHS OUTPUT VOLTAGE vs LOAD CURRENT EFFICIENCY vs LOAD CURRENT LOOP RESPONSE 60 1.9 100 180 Efficiency at 700 kHz 135 45 80 70 1.85 90 30 3.3 VI 1.8 5 VI 45 Gain 15 0 0 1.75 –45 –15 60 1.7 50 1 2 3 4 0 5 1 2 4 5 –30 100 Figure 12 LOAD TRANSIENT RESPONSE Load Transient Response – mV VO (AC) 10 mV/div VI = 5 V IO = 3 A 400 ns/div VO 50 mV/div IO 2 A/div VI = 5 V Time – 100 µs/div Time – 10 µs/div Figure 15 Figure 16 10 k 100 k START-UP WAVEFORMS VI 2 V/div VO 2 V/div VPWRGD 5 V/div Time – 2 ms/div Figure 17 AMBIENT TEMPERATURE vs LOAD CURRENT 125 T A – Ambient Temperature – ° C 115 105 † Safe operating area is applicable to the test board conditions listed in the Dissipation Rating Table section of this data sheet. 95 85 Safe Operating Area† 75 65 55 45 35 25 0 1 2 IL – Load Current – A Figure 18 10 3 4 –90 1M Figure 14 Figure 13 OUTPUT RIPPLE VOLTAGE 1k f – Frequency – Hz IL – Load Current – A Load Current – A Amplitude – 10 mV/div 3 Start Up Waveforms – V 0 Phase – Degrees 3.3 VI Phase Gain – dB 5 VI VO – Output Voltage – % Efficiency – % 90 TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 The actual slow-start is likely to be less than the above approximation due to the brief ramp-up at the internal rate. DETAILED DESCRIPTION Under Voltage Lock Out (UVLO) The TPS54311 – 16 incorporates an under voltage lockout circuit to keep the device disabled when the input voltage (VIN) is insufficient. During power up, internal circuits are held inactive until VIN exceeds the nominal UVLO threshold voltage of 2.95 V. Once the UVLO start threshold is reached, device start-up begins. The device operates until VIN falls below the nominal UVLO stop threshold of 2.8 V. Hysteresis in the UVLO comparator, and a 2.5-µs rising and falling edge deglitch circuit reduce the likelihood of shutting the device down due to noise on VIN. Slow-Start/Enable (SS/ENA) The slow-start/enable pin provides two functions; first, the pin acts as an enable (shutdown) control by keeping the device turned off until the voltage exceeds the start threshold voltage of approximately 1.2 V. When SS/ENA exceeds the enable threshold, device start up begins. The reference voltage fed to the error amplifier is linearly ramped up from 0 V to 0.891 V in 3.35 ms. Similarly, the converter output voltage reaches regulation in approximately 3.35 ms. Voltage hysteresis and a 2.5-µs falling edge deglitch circuit reduce the likelihood of triggering the enable due to noise. OUTPUT VOLTAGE SLOW-START TPS54311 0.9 V 3.3 ms TPS54312 1.2 V 4.5 ms TPS54313 1.5 V 5.6 ms TPS54314 1.8 V 3.3 ms TPS54315 2.5 V 4.7 ms TPS54316 3.3 V 6.1 ms DEVICE 1.2 V 5 mA (SS) +C (SS) (2) 0.7 V 5 mA Voltage Reference The voltage reference system produces a precise Vref signal by scaling the output of a temperature stable bandgap circuit. During manufacture, the bandgap and scaling circuits are trimmed to produce 0.891 V at the output of the error amplifier, with the amplifier connected as a voltage follower. The trim procedure adds to the high precision regulation of the TPS54311 – 16, since it cancels offset errors in the scale and error amplifier circuits. The oscillator frequency can be set to internally fixed values of 350 kHz or 550 kHz using the FSEL pin as a static digital input. If a different frequency of operation is required for the application, the oscillator frequency can be externally adjusted from 280 kHz to 700 kHz by connecting a resistor to the RT pin to ground and floating the FSEL pin. The switching frequency is approximated by the following equation, where R is the resistance from RT to AGND: Second, as the output becomes active, a brief ramp-up at the internal slow-start rate may be observed before the externally set slow-start rate takes control and the output rises at a rate proportional to the slow-start capacitor. The slow-start time set by the capacitor is approximately: t The VBIAS regulator provides internal analog and digital blocks with a stable supply voltage over variations in junction temperature and input voltage. A high quality, low-ESR, ceramic bypass capacitor is required on the VBIAS pin. X7R or X5R grade dielectrics are recommended because their values are more stable over temperature. The bypass capacitor should be placed close to the VBIAS pin and returned to AGND. External loading on VBIAS is allowed, with the caution that internal circuits require a minimum VBIAS of 2.70 V, and external loads on VBIAS with ac or digital switching noise may degrade performance. The VBIAS pin may be useful as a reference voltage for external circuits. Oscillator and PWM Ramp The second function of the SS/ENA pin provides an external means of extending the slow-start time with a low-value capacitor connected between SS/ENA and AGND. Adding a capacitor to the SS/ENA pin has two effects on start-up. First, a delay occurs between release of the SS/ENA pin and start up of the output. The delay is proportional to the slow-start capacitor value and lasts until the SS/ENA pin reaches the enable threshold. The start-up delay is approximately: t +C d (SS) VBIAS Regulator (VBIAS) (3) SWITCHING FREQUENCY + 100 kW R 500 kHz (4) Table 1. Summary of the Frequency Selection Configurations SWITCHING FREQUENCY FSEL PIN RT PIN 350 kHz, internally set Float or AGND Float 550 kHz, internally set ≥ 2.5 V Float Externally set 280 kHz to 700 kHz Float R = 68 k to 180 k Error Amplifier The high performance, wide bandwidth, voltage error amplifier is gain limited to provide internal compensation of the control loop. The user is given limited flexibility in choosing output L and C filter components. Inductance 11 TPS54311, TPS54312 TPS54313, TPS54314 TPS54315, TPS54316 www.ti.com SLVS416A – FEBRUARY 2002 – JULY 2003 values of 4.7 µH to 10 µH are typical and available from several vendors. The resulting designs exhibit good noise and ripple characteristics, along with exceptional transient response. Transient recovery times are typically in the range of 10 to 20 µs. PWM Control Signals from the error amplifier output, oscillator, and current limit circuit are processed by the PWM control logic. Referring to the internal block diagram, the control logic includes the PWM comparator, OR gate, PWM latch, and portions of the adaptive dead-time and control logic block. During steady-state operation below the current limit threshold, the PWM comparator output and oscillator pulse train alternately reset and set the PWM latch. Once the PWM latch is set, the low-side FET remains on for a minimum duration set by the oscillator pulse duration. During this period, the PWM ramp discharges rapidly to its valley voltage. When the ramp begins to charge back up, the low-side FET turns off and high-side FET turns on. As the PWM ramp voltage exceeds the error amplifier output voltage, the PWM comparator resets the latch, thus turning off the high-side FET and turning on the low-side FET. The low-side FET remains on until the next oscillator pulse discharges the PWM ramp. During transient conditions, the error amplifier output could be below the PWM ramp valley voltage or above the PWM peak voltage. If the error amplifier is high, the PWM latch is never reset and the high-side FET remains on until the oscillator pulse signals the control logic to turn the high-side FET off and the low-side FET on. The device operates at its maximum duty cycle until the output voltage rises to the regulation set-point, setting VSENSE to approximately the same voltage as Vref. If the error amplifier output is low, the PWM latch is continually reset and the high-side FET does not turn on. The low-side FET remains on until the VSENSE voltage decreases to a range that allows the PWM comparator to change states. The TPS54311 – 16 is capable of sinking current continuously until the output reaches the regulation set-point. If the current limit comparator trips for longer than 100 ns, the PWM latch resets before the PWM ramp exceeds the error amplifier output. The high-side FET turns off and low-side FET turns on to decrease the energy in the output inductor and consequently the output current. This process is repeated each cycle in which the current limit comparator is tripped. Dead-Time Control and MOSFET Drivers Adaptive dead-time control prevents shoot-through current from flowing in both N-channel power MOSFETs during the switching transitions by actively controlling the 12 turn-on times of the MOSFET drivers. The high-side driver does not turn on until the gate drive voltage to the low-side FET is below 2 V. The low-side driver does not turn on until the voltage at the gate of the high-side MOSFETs is below 2 V. The high-side and low-side drivers are designed with 300-mA source and sink capability to quickly drive the power MOSFETs gates. The low-side driver is supplied from VIN, while the high-side drive is supplied from the BOOT pin. A bootstrap circuit uses an external BOOT capacitor and an internal 2.5-Ω bootstrap switch connected between the VIN and BOOT pins. The integrated bootstrap switch improves drive efficiency and reduces external component count. Overcurrent Protection The cycle by cycle current limiting is achieved by sensing the current flowing through the high-side MOSFET and differential amplifier and comparing it to the preset overcurrent threshold. The high-side MOSFET is turned off within 200 ns of reaching the current limit threshold. A 100-ns leading edge blanking circuit prevents false tripping of the current limit. Current limit detection occurs only when current flows from VIN to PH when sourcing current to the output filter. Load protection during current sink operation is provided by thermal shutdown. Thermal Shutdown The device uses the thermal shutdown to turn off the power MOSFETs and disable the controller if the junction temperature exceeds 150°C. The device is released from shutdown when the junction temperature decreases to 10°C below the thermal shutdown trip point and starts up under control of the slow-start circuit. Thermal shutdown provides protection when an overload condition is sustained for several milliseconds. With a persistent fault condition, the device cycles continuously; starting up by control of the soft-start circuit, heating up due to the fault, and then shutting down upon reaching the thermal shutdown point. Power Good (PWRGD) The power good circuit monitors for under voltage conditions on VSENSE. If the voltage on VSENSE is 10% below the reference voltage, the open-drain PWRGD output is pulled low. PWRGD is also pulled low if VIN is less than the UVLO threshold, or SS/ENA is low, or thermal shutdown is asserted. When VIN = UVLO threshold, SS/ENA = enable threshold, and VSENSE > 90% of Vref, the open drain output of the PWRGD pin is high. A hysteresis voltage equal to 3% of Vref and a 35-µs falling edge deglitch circuit prevent tripping of the power good comparator due to high frequency noise. THERMAL PAD MECHANICAL DATA PowerPAD™ PLASTIC SMALL-OUTLINE PWP (R-PDSO-G20) www.ti.com 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. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Amplifiers Applications amplifier.ti.com Audio www.ti.com/audio Data Converters dataconverter.ti.com Automotive www.ti.com/automotive DSP dsp.ti.com Broadband www.ti.com/broadband Interface interface.ti.com Digital Control www.ti.com/digitalcontrol Logic logic.ti.com Military www.ti.com/military Power Mgmt power.ti.com Optical Networking www.ti.com/opticalnetwork Microcontrollers microcontroller.ti.com Security www.ti.com/security Telephony www.ti.com/telephony Video & Imaging www.ti.com/video Wireless www.ti.com/wireless Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright 2003, Texas Instruments Incorporated