Sample & Buy Product Folder Support & Community Tools & Software Technical Documents LP8728D-Q1 SNVSA72 – FEBRUARY 2015 LP8728D-Q1 Quad-Output Step-Down DC-DC Converter 1 Features 3 Description • The LP8728D-Q1 is a quad-output Power Management Unit (PMU), optimized for low-power FPGAs, microprocessors, and DSPs for automotive applications. This device integrates four highly efficient step-down DC-DC converters into one package. Each converter has high current capability and separate controls which allows flexibility to use the device in multiple applications. All the converters operate above the AM band with a fixed 3.2-MHz switching frequency. The high-side switch turn-on time of each converter is phase shifted to minimize input current spikes. 1 • • • • • • LP8728D-Q1 is an Automotive Grade Product that is AECQ-100 Grade 1 Qualified Four High Efficiency Step-Down DC-DC Converters: – 93% Peak Efficiency (VIN = 5 V, VOUT = 3.3 V) – Max Output Current 1 A – Forced PWM Operation – Soft-Start Control – VOUT1 = 3.3 V – VOUT2 = 1.25 V – VOUT3 = 1.8 V or 2.65 V (pin selectable) – VOUT4 = 1.8 V Separate Enable Inputs for each Converter Control Separate Power Good Outputs for each Converter Output Overcurrent and Input Overvoltage Protection Overtemperature Protection Undervoltage Lockout (UVLO) 2 Applications • • • • • Protection features include output short-circuit protection, switch current limits, input overvoltage protection, input undervoltage lockout, and thermal shutdown functions. During start-up, the device controls the output slew rate to minimize output voltage overshoot and the input inrush current. Device Information(1) PART NUMBER LP8728D-Q1 PACKAGE BODY SIZE (NOM) WQFN (28) 5.00 mm x 5.00 mm (1) For all available packages, see the orderable addendum at the end of the datasheet. space FPGA, DSP Core Power Processor Power for Mobile Devices Peripheral I/O Power Automotive Safety Cameras Automotive Infotainment space space space space space Simplified Schematic VIN Efficiency VIN 10 µF VIN_B1 AVDD 1 µF 100 1.5 µH VIN 10 µF VIN_B2 VDDIO 1.5 µH VOUT2 10 µF SW_B2 FB_B2 LP8728 PG_B1 PG_B3 Micro Controller VIN 10 µF VIN_B3 PG_B2 1.5 µH PG_B4 SW_B3 EN_B1 FB_B3 VOUT3 10 µF VIN_B4 VIN EN_B2 EN_B3 10 µF GND_B3 GND_B4 GND_B2 AGND DEFSEL GND_B1 EN_B4 1.5 µH SW_B4 FB_B4 VOUT4 80 EFFICIENCY (%) FB_B1 1 µF 90 VOUT1 10 µF SW_B1 BYP 70 60 50 40 3.3V 30 2.65V 20 1.8V 10 1.25V 0 0 100 200 300 400 500 600 700 OUTPUT CURRENT (mA) 800 900 1000 C000 10 µF 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LP8728D-Q1 SNVSA72 – FEBRUARY 2015 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 5 6.1 6.2 6.3 6.4 6.5 6.6 6.7 5 5 5 6 6 7 8 Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics........................................... System Characteristics ............................................. Typical Characteristics .............................................. 7.3 Feature Description................................................. 11 7.4 Device Functional Modes........................................ 13 8 Application and Implementation ........................ 15 8.1 Application Information............................................ 15 8.2 Typical Application ................................................. 15 9 Power Supply Recommendations...................... 17 10 Layout................................................................... 18 10.1 Layout Guidelines ................................................. 18 10.2 Layout Example .................................................... 18 11 Device and Documentation Support ................. 19 11.1 11.2 11.3 11.4 11.5 Detailed Description ............................................ 10 7.1 Overview ................................................................. 10 7.2 Functional Block Diagram ....................................... 10 Device Support .................................................... Related Documentation......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 19 19 19 19 19 12 Mechanical, Packaging, and Orderable Information ........................................................... 19 4 Revision History 2 DATE REVISION NOTES February 2015 * Initial release. Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 LP8728D-Q1 www.ti.com SNVSA72 – FEBRUARY 2015 5 Pin Configuration and Functions WQFN (RSG) Package 28 Pins VIN_B2 SW_B2 GND_B2 GND_B1 SW_B1 VIN_B1 EN_B1 TOP VIEW 7 6 5 4 3 2 1 PIN 1 ID FB_B2 8 28 FB_B1 EN_B2 9 27 PG_B1 PG_B2 10 26 AVDD DEFSEL 11 25 BYP PG_B3 12 24 AGND EN_B3 13 23 PG_B4 FB_B3 14 22 FB_B4 18 19 20 21 SW_B4 VIN_B4 EN_B4 SW_B3 17 GND_B4 16 GND_B3 15 VIN_B3 DAP Pin Functions PIN NUMBER (1) NAME TYPE (1) DESCRIPTION 1 EN_B1 D/I 2 VIN_B1 P Enable Buck 1 Positive power supply input for Buck 1 3 SW_B1 P Switch node for Buck 1 4 GND_B1 G Power ground for Buck 1 5 GND_B2 G Power ground for Buck 2 6 SW_B2 P Switch node for Buck 2 7 VIN_B2 P Positive power supply input for Buck 2 Feedback pin for Buck 2. Referenced against AGND. 8 FB_B2 A 9 EN_B2 D/I Enable Buck 2 10 PG_B2 D/O Open-drain Power Good output for Buck 2 11 DEFSEL D/I Buck 3 output voltage selection pin 12 PG_B3 D/O Open-drain Power Good output for Buck 3 13 EN_B3 D/I Enable Buck 3 14 FB_B3 A Feedback pin for Buck 3. Referenced against AGND. 15 VIN_B3 P Positive power supply input for Buck 3 16 SW_B3 P Switch node for Buck 3 17 GND_B3 G Power ground for Buck 3 18 GND_B4 G Power ground for Buck 4 19 SW_B4 P Switch node for Buck 4 A: Analog Pin, G: Ground Pin, P: Power Pin, O: Output Pin, D/I: Digital Input, D/O: Digital Output. Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 3 LP8728D-Q1 SNVSA72 – FEBRUARY 2015 www.ti.com Pin Functions (continued) PIN 4 TYPE (1) DESCRIPTION NUMBER NAME 20 VIN_B4 P 21 EN_B4 D/I 22 FB_B4 A 23 PG_B4 D/O 24 AGND G Analog ground 25 BYP A Internal 1.8-V supply voltage capacitor pin. A ceramic low-ESR 1-μF capacitor should be connected from this pin to AGND. The BYP voltage is generated internally, do not supply or load this pin externally. Positive power supply input for Buck 4 Enable Buck 4 Feedback pin for Buck 4. Referenced against AGND. Open-drain Power Good output for Buck 4 26 AVDD P Analog positive power supply pin (VIN level) 27 PG_B1 D/O Open-drain Power Good output for Buck 1 28 FB_B1 A DAP Die Attachment Pad Feedback pin for Buck 1. Referenced against AGND. Exposed die attachment pad should to be connected to GND plane with thermal vias to improve the thermal performance of the system. Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 LP8728D-Q1 www.ti.com SNVSA72 – FEBRUARY 2015 6 Specifications 6.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) (1) VIN Voltage on power pins (AVDD, VIN_Bx) VFB Voltage on feedback pins (FB_Bx) VSW Voltage on buck converter switch pins (SW_Bx) VDIG Voltage on digital pins (PG_Bx, EN_Bx, DEFSEL) VBYP Voltage on BYP pin TJ(MAX) Maximum operating junction temperature (2) MIN MAX UNIT –0.3 6 V –0.3 6 V (GND_Bx – 0.2 V) to (VIN_Bx + 0.2 V) with 6 V max V (AGND – 0.2V) to (AVDD + 0.2 V) with 6 V max V –0.3 (1) (2) (3) V °C 150 °C See (3) Maximum lead temperature (Soldering) Tstg 2 150 Storage temperature –65 Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ = 150°C (typical) and disengages at TJ = 130°C (typical). For detailed soldering specifications and information, please refer to Texas Instruments Application Note Leadless Leadframe Package (LLP) SNOA401. 6.2 ESD Ratings VALUE V(ESD) (1) Electrostatic discharge Human-body model (HBM), per AEC Q100-002 (1) UNIT ±2000 Charged-device model (CDM), per AEC Q100-011 V ±750 AEC Q100-002 indicates that HBM stressing shall be in accordance with the ANSI/ESDA/JEDEC JS-001 specification. 6.3 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) (1) MIN NOM MAX VIN Input voltage on AVDD, VIN_B1, VIN_B2, VIN_B3 and VIN_B4 pins 4.5 5 5.5 V TA Operating ambient temperature (2) –40 125 °C COUT Effective output capacitance during operation. Min value over TA –40°C to 125°C. 12 µF CIN Effective input capacitance during operation. 4.5 V ≤ VIN_Bx ≤ 5.5 V. Min value over TA –40°C to 125°C. L Effective inductance during operation Min value over TA –40°C to 125°C. (1) (2) 5 10 2.5 10 0.47 1.5 UNIT µF 2 µF All voltage values are with respect to network ground terminal. In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA(max)) is dependent on the maximum operating junction temperature (TJ(max)), the maximum power dissipation of the device in the application (PD(max)), and the junction-to-ambient thermal resistance of the part/package in the application (RθJA), as given by the following equation: TA(max) = TJ(max) – (RθJA × PD(max)) Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 5 LP8728D-Q1 SNVSA72 – FEBRUARY 2015 www.ti.com 6.4 Thermal Information LP8728-Q1 THERMAL METRIC (1) WQFN (RSG) UNIT 28 PINS RθJA Junction-to-ambient thermal resistance (2) 37.7 RθJCtop Junction-to-case (top) thermal resistance 24.5 RθJB Junction-to-board thermal resistance 10.8 ΨJT Junction-to-top characterization parameter 0.3 ΨJB Junction-to-board characterization parameter 10.8 RθJCbot Junction-to-case (bottom) thermal resistance 2.7 (1) (2) °C/W For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953. Calculated using 4-layer standard JEDEC thermal test board with 5 thermal vias between the die attach pad in the first copper layer and second copper layer. 6.5 Electrical Characteristics (1) (2) Unless otherwise noted, VIN = 5 V, typical values apply for TA = 25°C, and minimum/maximum limits apply over junction temperature range, TJ = –40°C to 125°C. PARAMETER TEST CONDITIONS ISHDN Shutdown supply current into power connections EN_Bx = 0 V IOP Operating current All buck-converters active, IOUT = 0 mA MIN TYP MAX 1 6 20 UNIT μA mA LOGIC INPUTS (EN_Bx, DEFSEL) VIL Input low level 0.4 V VIH Input high level 1.6 RPD_DI EN_Bx and DEFSEL internal pulldown resistance 300 TH_MIN Minimum EN_Bx high time 1 ms TL_MIN Minimum EN_Bx low time 10 µs V 520 820 kΩ LOGIC OUTPUTS (PG_Bx) VOL Output low level RPU Recommended pullup resistor ISINK = 3 mA 0.4 V 10 kΩ BUCK CONVERTERS VOUT1 Output voltage for Buck 1 Fixed voltage 3.3 V VOUT2 Output voltage for Buck 2 Fixed voltage 1.25 V DEFSEL = 1 2.65 DEFSEL = 0 1.8 VOUT3 Output voltage for Buck 3 VOUT4 Output voltage for Buck 4 VFB_Bx Output voltage accuracy Fixed voltage V 1.8 –3% V 3% Line regulation 4.5 V ≤ VIN_Bx ≤ 5.5 V, ILOAD = 10 mA 3 mV Load regulation VIN = 5 V, 100 mA ≤ ILOAD ≤ 900 mA 3 mV IOUT Output current DC load TA = 25°C fSW Switching frequency GBW Gain bandwidth ILIMITP High-side switch current limit ILIMITN Low-side switch current limit Reverse current 500 RDSONP Pin-pin resistance for PFET IOUT = 200 mA 210 300 mΩ RDSONN Pin-pin resistance for NFET IOUT = 200 mA 140 240 mΩ ΔVOUT (1) (2) 6 3.03 3.2 1200 1500 1000 mA 3.37 MHz 300 kHz 1800 mA mA All voltage values are with respect to network ground terminal. Minimum (Min) and Maximum (Max) limits are specified by design, test, or statistical analysis. Typical (Typ) numbers are not verified, but do represent the most likely norm. Unless otherwise specified, conditions for Typ specifications are: VIN = 5 V and TJ = 25°C. Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 LP8728D-Q1 www.ti.com SNVSA72 – FEBRUARY 2015 Electrical Characteristics(1)(2) (continued) Unless otherwise noted, VIN = 5 V, typical values apply for TA = 25°C, and minimum/maximum limits apply over junction temperature range, TJ = –40°C to 125°C. PARAMETER TEST CONDITIONS ILK_SW Switch pin leakage current VOUT = 1.8V RPD_FB Pulldown resistor from FB_Bx pin to GND Only active when converter disabled. All limits apply for TA = 25°C KRAMP Slew rate control DEFSEL from 0 to 1 TSTART Start-up time Time from first EN_Bx high to start of switching KSTART Soft-start VOUT slew rate MIN 40 TYP 70 MAX UNIT 1 µA 100 Ω 10 mV/µs 420 µs 18 mV/µs VOLTAGE MONITORING VPG Power good threshold voltage VOVP VUVLO Input overvoltage protection trigger point Input undervoltage lockout (UVLO) threshold. Power good threshold for voltage rising 93.5% 96% 98% Power good threshold for voltage falling 91% 93% 95% 5.5 5.7 5.9 Voltage monitored on AVDD Pin, voltage rising Hysteresis 80 Voltage monitored on AVDD Pin, voltage falling 2.7 Hysteresis 80 V mV V mV THERMAL SHUTDOWN AND MONITORING TSD Thermal shutdown Threshold, temperature rising 150 Hysteresis °C 20 6.6 System Characteristics (1) (2) (3) Typical values apply for TA = 25°C. Unless otherwise noted, VIN = 5 V. PARAMETER (1) (2) (3) TYP MAX UNIT mV IOUT 90% max load → 10% max load, 1µs load step 70 mV Line transient response VIN_Bx stepping 4.5 V ↔ 5.5 V, tRISE = tFALL = 10 µs, IOUT = 400 mA 20 mV Output voltage ripple COUT ESR = 10 mΩ, IOUT = 200 mA 10 mVPP ΔVOUT η MIN 70 Load transient response VRIPPLE TEST CONDITIONS IOUT 10% max load → 90% max load, 1µs load step Efficiency VOUT = 3.3 V, IOUT = 300 mA 94% VOUT = 2.65 V, IOUT = 300 mA 92% VOUT = 1.8 V, IOUT = 300 mA 89% VOUT = 1.25 V, IOUT = 300 mA 85% All voltage values are with respect to network ground terminal. Minimum (Min) and Maximum (Max) limits are specified by design, test, or statistical analysis. Typical (Typ) numbers are not verified, but do represent the most likely norm. Unless otherwise specified, conditions for Typ specifications are: VIN = 5 V and TJ = 25°C. System Characteristics are highly dependent on external components and PCB layout. System Characteristics are verified using inductor type: TOKO MDT2520-CN1R5M, input and output capacitor type: MuRata GRM21BR71A106KE51L. Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 7 LP8728D-Q1 SNVSA72 – FEBRUARY 2015 www.ti.com 6.7 Typical Characteristics 100 3280 90 3260 80 3240 70 3220 60 3200 fSW (Hz) EFFICIENCY (%) Unless otherwise noted, VIN = 5 V, TA = 25°C, inductor type: TOKO MDT2520-CN1R5M, input and output capacitor type: MuRata GRM21BR71A106KE51L. 50 40 3.3V 30 2.65V 20 1.8V 10 1.25V 3180 3160 3140 3120 3100 3080 0 0 100 200 300 400 500 600 700 800 900 OUTPUT CURRENT (mA) 1000 3060 -60 -20 0 3.32 3.32 3.31 3.31 VOUT1 (V) 3.33 3.30 3.29 60 80 100 3.29 +125°C +25°C +25°C 3.27 3.26 -40°C 3.26 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 IOUT1 (A) 1.0 4.4 4.5 4.6 4.7 1.26 1.26 1.25 1.25 VOUT2 (V) 1.27 1.24 1.23 5.0 5.1 5.2 5.3 5.4 5.5 5.6 C007 1.24 1.23 1.22 +125°C +25°C 1.21 4.9 Figure 4. Buck1 Line Regulation 1.27 1.22 4.8 SUPPLY VOLTAGE (V) C006 Figure 3. Buck1 Load Regulation VOUT2 (V) 140 3.30 -40°C +125°C +25°C 1.21 -40°C -40°C 1.20 1.20 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 IOUT2 (A) 0.9 1.0 4.4 4.5 C008 Figure 5. Buck2 Load Regulation 8 120 C012 3.28 +125°C 3.27 40 Figure 2. Switching Frequency vs Temperature 3.33 3.28 20 TEMPERATURE (C) Figure 1. Efficiency vs Output Current VOUT1 (V) -40 C000 Submit Documentation Feedback 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 SUPPLY VOLTAGE (V) 5.4 5.5 5.6 C009 Figure 6. Buck2 Line Regulation Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 LP8728D-Q1 www.ti.com SNVSA72 – FEBRUARY 2015 Typical Characteristics (continued) Unless otherwise noted, VIN = 5 V, TA = 25°C, inductor type: TOKO MDT2520-CN1R5M, input and output capacitor type: MuRata GRM21BR71A106KE51L. 5.0 25 + 125°C 4.0 + 85°C 3.5 + 25°C 3.0 - 40°C 24 SUPPLY CURRENT (mA) ISHDN (A) 4.5 2.5 2.0 23 22 21 20 19 18 - 40°C 17 + 25°C 0.5 16 + 125°C 0.0 15 1.5 1.0 4.4 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 SUPPLY VOLTAGE (V) 5.5 5.6 4.4 4.5 Figure 7. Shutdown Current Consumption 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 SUPPLY VOLTAGE (V) C010 5.6 C011 Figure 8. Active Mode Current Consumption (All Bucks Active) Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 9 LP8728D-Q1 SNVSA72 – FEBRUARY 2015 www.ti.com 7 Detailed Description 7.1 Overview The LP8728D-Q1 has four integrated high-efficiency buck converters. Each buck converter has individual enable input and power good output pins. When the first enable pin is pulled high there is a 420-µs start-up delay when the device wakes up from the shutdown mode and all internal reference blocks are started up. Once reference blocks have settled, the corresponding buck converter turns on. Buck cores utilize the soft-start feature to limit the inrush current during start-up. Once a buck output reaches 96% (typical) of the desired output voltage, the power-good pin is pulled high (see Figure 9). When at least one buck core is active, the remaining buck converters will start up without any start-up delay. If the output voltage drops below 93% (typical) of desired voltage due to, for example, an overload condition, the corresponding power-good pin is pulled low. The power-good signal is always held low for at least 50 ms. When the enable pin is pulled low, the corresponding buck converter's power good signals are set low, and the buck converter is instantly shut down. An output capacitor is then discharged through an internal 70-Ω (typical) pulldown resistor. The pulldown resistor is connected between buck feedback pin and ground and is only active when the enable pin is set low. When all enable signals are pulled low, the LP8728D-Q1 enters a low current shutdown mode. 7.2 Functional Block Diagram VIN AVDD 1 µF VIN_B1 VIN BYP 10 µF LDO 1 µF Buck1 (Active Pulldown) Oscillator FB_B1 SW_B1 1.5 µH VOUT1 UVLO 10 µF Reference Voltage VIN_B2 Thermal Shutdown VIN 10 µF OTP Buck2 (Active Pulldown) PG_B1 FB_B2 SW_B2 1.5 µH VOUT2 10 µF PG_B2 PG_B3 VIN_B3 VIN 10 µF PG_B4 Buck3 (Active Pulldown) DEFSEL Control Logic FB_B3 SW_B3 EN_B1 1.5 µH VOUT3 10 µF EN_B2 VIN_B4 EN_B3 VIN 10 µF Buck4 (Active Pulldown) EN_B4 FB_B4 SW_B4 1.5 µH VOUT4 10 GND_B4 GND_B3 GND_B2 GND_B1 AGND 10 µF Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 LP8728D-Q1 www.ti.com SNVSA72 – FEBRUARY 2015 7.3 Feature Description 7.3.1 Buck Information The buck converters are operated in a forced PWM mode. Even with light load a minimum switching pulse is generated with every switching cycle. Each buck converter's high-side switch turn-on time is phase shifted to minimize the input current ripple (see Figure 20). 7.3.1.1 Features The following features are supported for all converters: • • • • • • Synchronous rectification Current mode feedback loop with PI compensator Forced PWM operation Soft start Power-good output Overvoltage comparator In addition to the aforementioned features, Buck3 output voltage can be selected with the DEFSEL pin. If the DEFSEL pin is pulled low, VOUT3 is set to 1.8 V. If DEFSEL is pulled high, VOUT3 is set to 2.65 V. 96% 93% Active pulldown VOUTx Overload condition 5% EN_Bx PG_Bx TSTART 50ms TRAMP Figure 9. Buck Converter Start-up And Shutdown 7.3.2 Thermal Shutdown (TSD) Thermal shutdown function shuts down all buck regulators if the device's junction temperature TJ rises above 150°C (typ.). All power-good signals are pulled low 5 ms before the buck regulators are shut down. Once TJ falls below 130°C (typical), the LP8728 will automatically start up the buck regulators. There is a 2-second safety delay included in the restart function. Buck regulators are not restarted until 2 seconds have elapsed after TJ falls below 130°C (typical). To minimize the inrush current during restarting, regulators are started in a Buck1 → Buck2 → Buck3 → Buck4 sequence. A 500-µs delay is included between each buck start-up. 150°C Junction Temperature TJ 130°C TSD (Internal Signal) PG_B1 PG_B2 PG_B3 PG_B4 VOUT1 VOUT3 VOUT4 VOUT2 5 ms 2s 500us 500us 500us Figure 10. TSD Timing Diagram Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 11 LP8728D-Q1 SNVSA72 – FEBRUARY 2015 www.ti.com Feature Description (continued) 7.3.3 Undervoltage Lockout (UVLO) If input voltage drops below 2.7 V (typ.) the PG_Bx pins are pulled low and the buck converters are shut down. (Figure 11). The PG_Bx pins are always held low for at least 50 ms. The buck converters are restarted once the input voltage rises above UVLO level. If a UVLO condition has lasted less than 50 ms, the PG_Bx pins are released high once 50 ms has elapsed and corresponding output voltage has settled. If an overvoltage condition has lasted more than 50 ms, the PG_Bx pins are released high once corresponding output voltage has settled. Regulators are always restarted in a Buck1 → Buck2 → Buck3 → Buck4 sequence. A 500-µs delay is included between each buck start-up. 5.0V VIN 3.3V 2.7V UVLO PG_B1 PG_B2 PG_B3 PG_B4 VOUT1 VOUT3 VOUT4 VOUT2 Figure 11. UVLO Operation 7.3.4 Overvoltage Protection (OVP) Overvoltage protection protects the device in case of an overvoltage condition. If input voltage exceeds 5.7 V (typical), all PG_Bx pins are pulled low. the PG_Bx pins are always held low for at least 50 ms. Once the PG_Bx pins are pulled low, the system has 5 ms time to power down. After an overvoltage condition has lasted for 5 ms, all buck converters are shut down. The buck converters are restarted once input voltage falls below 5.62 V (typical). The buck converters are started in a Buck1 → Buck2 → Buck3 → Buck4 sequence. A 500-µs delay is included between each buck start-up. If an overvoltage condition lasted more than 5 ms, but less than 50 ms, the PG_Bx pins are released high once 50 ms has elapsed and the corresponding output voltage has settled (Figure 12). VIN 5.7V OVP PG_B1 PG_B2 PG_B3 PG_B4 VOUT1 VOUT3 VOUT4 VOUT2 5 ms 500μs 500μs 500μs 50 ms Figure 12. OVP Duration Less Than 50 ms 12 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 LP8728D-Q1 www.ti.com SNVSA72 – FEBRUARY 2015 Feature Description (continued) If an overvoltage condition has lasted more than 50 ms, the power-good signals are released high once the corresponding output voltage has settled. Regulators are started in a buck1 → buck2 → buck3 → buck4 sequence. A 500-µs delay is included between each buck start-up (Figure 13). If an overvoltage condition has lasted less than 5 ms, the buck converters are not shut down. Even in this case the PG_Bx pins are held low for 50 ms. NOTE Since the regulators are allowed to operate for 5 ms during overvoltage condition it is the system designer’s responsibility to verify that input voltage doesn’t exceed limits stated in Absolute Maximum Ratings. Exceeding these limits may cause permanent damage to the device. VIN 5.7V OVP PG_B1 PG_B2 PG_B3 PG_B4 VOUT1 VOUT3 VOUT4 VOUT2 5 ms 50 ms 500μs 500μs 500μs Figure 13. OVP Duration More Than 50 ms 7.4 Device Functional Modes 7.4.1 Shutdown Mode When all EN_Bx inputs are low, the device is in a Shutdown mode. This is a low-power mode when all buckregulators and all internal blocks are disabled. 7.4.2 Active Mode When the first enable pin is pulled high there is a 420-µs start-up delay when the device wakes up from the Shutdown; mode and all internal reference blocks are started up. Once the reference blocks have settled, the corresponding buck converter turns on. Buck cores utilize the soft-start feature to limit the inrush current during start-up. Once a buck output reaches 96% (typical) of the desired output voltage, the power-good pin is pulled high. When at least one buck converter is active device is in a Active mode. When device is in Active mode, the remaining buck converters will start up without any start-up delay when EN_Bx pin is pulled high. When EN_Bx pin is set low the corresponding buck converter will shut down. When all EN_Bx pins are set low the device shuts down all internal reference blocks and enters Shutdown mode. If output voltage of a buck regulator falls below 93% (typical) of desired voltage due to, for example, an overload condition, the corresponding power good pin is pulled low. Once the output voltage rises back above 96% (typical) of desired voltage power good pin is set back high. Power good signal is held low for at least 50 ms. Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 13 LP8728D-Q1 SNVSA72 – FEBRUARY 2015 www.ti.com Device Functional Modes (continued) If OVP, or TSD fault occurs during normal operation, all power good pins are pulled low. Once fault condition has lasted for 5 ms all buck converters are shut down. In case of UVLO fault buck regulators are instantly shut down. Once fault condition has ended buck converters are restarted in a Buck1 → Buck2 → Buck3 → Buck4 power-up sequence. A 500-µs delay is included between each buck start-up. In case of TSD fault there is a 2-second safety delay before power-up sequence. Shutdown Mode EN_Bx = HIGH & VIN > UVLO Reference Startup (420 µs typ) Reference Shutdown Normal Operation All EN_Bx pins are LOW Buck_X Startup Buck_X Shutdown EN_Bx = HIGH All EN_Bx pins not LOW EN_Bx = LOW Power-up Sequence Active Mode Fault > 5 ms Fault < 5 ms Fault UVLO, OVP or TSD Fault VOUTX falls below power good threshold PG_Bx is pulled low Figure 14. Device Functional Modes 14 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 LP8728D-Q1 www.ti.com SNVSA72 – FEBRUARY 2015 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information The LP8728D-Q1 is a quad-output Power Management Unit (PMU), optimized for low-power FPGAs, microprocessors, and DSPs. 8.2 Typical Application Figure 15 shows an example of a typical application. A microcontroller controls each buck converter with separate enable signals. All four power good signals are connected to a microcontroller with dedicated pullup resistors. If only one master power good signal is required all power good signals can be connected in parallel and pulled up with a single pullup resistor. VOUT3 output voltage can be selected with a DEFSEL input. If VOUT3 output voltage control is not required during operation, output voltage can be selected by connecting DEFSEL pin to VDDIO or to GND. VIN VIN 10 µF VIN_B1 AVDD 1 µF 1.5 µH VOUT1 10 µF SW_B1 BYP FB_B1 1 µF VIN 10 µF VIN_B2 VDDIO 1.5 µH VOUT2 10 µF SW_B2 FB_B2 LP8728 PG_B1 PG_B3 Micro Controller VIN 10 µF VIN_B3 PG_B2 1.5 µH PG_B4 SW_B3 EN_B1 FB_B3 VOUT3 10 µF EN_B2 VIN VIN_B4 EN_B3 10 µF GND_B3 GND_B4 GND_B2 AGND DEFSEL GND_B1 EN_B4 1.5 µH VOUT4 SW_B4 10 µF FB_B4 Figure 15. LP8728D-Q1 Typical Application Schematic Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 15 LP8728D-Q1 SNVSA72 – FEBRUARY 2015 www.ti.com Typical Application (continued) 8.2.1 Design Requirements DESIGN PARAMETER EXAMPLE VALUE Input voltage range (VIN) 4.5 V to 5.5 V Buck converter output current 1 A maximum Buck converter input capacitance 10 µF, 6.3 V Buck converter output capacitance 10 µF, 6.3 V Buck converter inductor 1.5 µH, 1.5 A AVDD pin bypass capacitor 1 µF, 6.3 V BYP pin bypass capacitor 1 µF, 6.3 V 8.2.2 Detailed Design Procedure 8.2.2.1 Inductor The four converters operate with 1.5-µH inductors. The inductor has to be selected based on the DC resistance and saturation current. The DC resistance of the inductor directly effects the efficiency of the converter. Therefore, an inductor with the lowest possible DC resistance should be selected for good efficiency. The inductor should have a saturation current rating equal or higher than the high-side switch current limit (1500 mA). To minimize radiated noise shielded inductor should be used. The inductor should be placed as close to the LP8728D-Q1 as possible, and the trace from the inductor to the buck converter switch pin needs to be wide enough to withstand the high switching currents. 8.2.2.2 Input and Output Capacitors Because buck converters have a discontinuous input current, a low equivalent series resistance (ESR) input capacitor is required for the best input-voltage filtering and to minimize interference with other circuits caused by high input voltage spikes. Each DC-DC converter requires a 10-µF ceramic input capacitor on its input pin VIN_Bx. The input capacitor capacitance can be increased without any limit for better input voltage filtering. Voltage rating of the capacitors should be at least 10V. A small 100-nF capacitor can be used in parallel to minimize high-frequency interferences. Input capacitors should be placed as close to the VIN_Bx pins as possible. Routing from input capacitor to VIN_Bx pins should be done on top layer without using any vias. An output capacitor with a typical value of 10 µF is recommended for each converter. Ceramic capacitors with low ESR value have lowest output voltage ripple and are recommended. Some ceramic capacitors, especially those in small packages, exhibit a strong capacitance reduction with the increased applied DC voltage (DC bias effect). The capacitance value can fall below half of the nominal capacitance. This needs to be taken into consideration and, if necessary, use a capacitor with higher value or higher voltage rating. Table 1. Recommended External Components COMPONENT DESCRIPTION VALUE TYPE EXAMPLE CIN_B1,2,3,4 Buck regulator input capacitor 10 µF Ceramic, 10 V, X7R MuRata, GRM21BR71A106KE51L COUT_B1,2,3,4 Buck regulator output capacitor 10 µF Ceramic, 10 V, X7R MuRata, GRM21BR71A106KE51L CAVDD AVDD pin input capacitor 1 µF Ceramic, 10 V, X7R MuRata, GRM188R71A105KA61D CBYP Internal LDO bypass capacitor 1 µF Ceramic, 10 V, X7R MuRata, GRM188R71A105KA61D Buck regulator inductor 1.5 µH ISAT >1.5 A, DCR < 100 mΩ TOKO MDT2520-CN1R5M LSW1,2,3 16 4 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 LP8728D-Q1 www.ti.com SNVSA72 – FEBRUARY 2015 8.2.3 Application Performance Plots Unless otherwise noted, VIN = 5 V, TA = 25°C, inductor type: TOKO MDT2520-CN1R5M, input and output capacitor type: MuRata GRM21BR71A106KE51L. EN_B1 VOUT1 100mV/div PG_B1 SW_B1 5V/div Inductor current 500mA/div VOUT1 1V/div 200s/div 100s/div C001 C012 Figure 16. Short-Circuit Waveforms Figure 17. Start-up Delay VOUT1 50mV/div VOUT1 50mV/div VIN 1V/div IOUT 500mA/div 10s/div 40s/div C013 C014 IOUT from 0 mA to 1A, tRISE = tFALL = 1 µs VIN from 4.5 V To 5.5 V, tRISE = tFALL = 10 µs Figure 18. Load Transient Response Figure 19. Line Transient Response SW1 SW2 SW3 SW4 80ns/div C013 Figure 20. Switch Turn-on Phase Shifting 9 Power Supply Recommendations The LP8728D-Q1 is designed to operate from an input voltage supply range between 4.5 V and 5.5 V. This input supply must be well regulated and capable to supply the required input current. If the input supply is located far from the device, additional bulk capacitance may be required in addition to the ceramic bypass capacitors. Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 17 LP8728D-Q1 SNVSA72 – FEBRUARY 2015 www.ti.com 10 Layout 10.1 Layout Guidelines • • • • • • • • AVDD and BYP pins must be bypassed to ground. 1-µF ceramic capacitor is recommended. Place the capacitors close to the AVDD, BYP, and AGND pins. AGND pin must be tied to the PCB ground plane. Use multiple vias to minimize the inductance. AVDD pin must be connected to PCB VIN plane. Use multiple vias to minimize the inductance. Place the buck converter input capacitors as close to the buck input voltage and buck ground pins as possible. Place the buck converter output capacitors and inductors so that the buck converter switching loops can be routed on top layer. Try to minimize the area of the switching loops. Keep the trace width from switch pin to inductor wide enough to withstand the switching currents. Avoid any excess copper on the switch node to minimize parasitic switch node capacitance. Connect the exposed thermal pad to ground plane with multiple thermal vias. Avoid routing digital signals directly under the switching loops to avoid interferences. 10.2 Layout Example L2 VOUT2 Vias to VIN plane L1 Vias to GND plane COUT2 COUT1 CIN2 CIN1 VOUT1 Vias to VIN plane EN_B1 VIN_B1 SW_B1 GND_B1 GND_B2 DEFSEL BYP PG_B3 AGND EN_B3 PG_B4 FB_B3 FB_B4 Connect thermal pad to GND plane using multiple vias Vias to VIN plane CBYP CIN EN_B4 AVDD VIN_B4 PG_B2 SW_B4 PG_B1 GND_B4 EN_B2 GND_B3 FB_B1 SW_B3 FB_B2 VIN_B3 Route to controller SW_B2 VIN_B2 Route to Controller on internal layers CIN3 CIN4 COUT3 COUT4 Route to Controller on internal layers Vias to VIN plane VOUT3 VOUT4 L3 Vias to GND plane L4 Figure 21. LP8728D-Q1 Layout Example 18 Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 LP8728D-Q1 www.ti.com SNVSA72 – FEBRUARY 2015 11 Device and Documentation Support 11.1 Device Support 11.1.1 Third-Party Products Disclaimer TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE. 11.2 Related Documentation For related documentation see the following: Texas Instruments Application Note 1187 Leadless Leadframe Package (LLP) (SNOA401). See Using the LP8728EVM Evaluation Module (SNVU231) for more information about LP8728 evaluation module. 11.3 Trademarks All trademarks are the property of their respective owners. 11.4 Electrostatic Discharge Caution 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. 11.5 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. Submit Documentation Feedback Copyright © 2015, Texas Instruments Incorporated Product Folder Links: LP8728D-Q1 19 PACKAGE OPTION ADDENDUM www.ti.com 15-Feb-2015 PACKAGING INFORMATION Orderable Device Status (1) LP8728QSQX-D/NOPB ACTIVE Package Type Package Pins Package Drawing Qty WQFN RSG 28 4500 Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM Op Temp (°C) Device Marking (4/5) -40 to 125 8728Q-D (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. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. 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Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 15-Feb-2015 Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 14-Feb-2015 TAPE AND REEL INFORMATION *All dimensions are nominal Device LP8728QSQX-D/NOPB Package Package Pins Type Drawing WQFN RSG 28 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 4500 330.0 12.4 Pack Materials-Page 1 5.3 B0 (mm) K0 (mm) P1 (mm) 5.3 1.3 8.0 W Pin1 (mm) Quadrant 12.0 Q1 PACKAGE MATERIALS INFORMATION www.ti.com 14-Feb-2015 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LP8728QSQX-D/NOPB WQFN RSG 28 4500 367.0 367.0 35.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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