Order Now Product Folder Support & Community Tools & Software Technical Documents LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 LMR33620 SIMPLE SWITCHER® 3.8-V to 36-V, 2-A Synchronous Step-Down Voltage Converter 1 Features 3 Description • The LMR33620 SIMPLE SWITCHER® regulator is an easy-to-use, synchronous, step-down DC/DC converter that delivers best-in-class efficiency for rugged industrial applications. The LMR33620 is capable of driving up to 2 A of load current from an input of up to 36 V. The LMR33620 provides high light load efficiency and output accuracy in a very small solution size. Features such as a power-good flag and precision enable provide both flexible and easy-to-use solutions for a wide range of applications. The LMR33620 automatically folds back frequency at light load to improve efficiency. Integration eliminates most external components and provides a pinout designed for simple PCB layout. Protection features include thermal shutdown, input undervoltage lockout, cycle-by-cycle current limit, and hiccup short-circuit protection. The LMR33620 is available in an 8-pin HSOIC package and in a 12-pin 3 mm × 2 mm VQFN package with wettable flanks. 1 • • • Configured for Rugged Industrial Applications – Input Voltage Range: 3.8 V to 36 V – Output Voltage Range: 1 V to 24 V – Output Current: 2 A – 75 mΩ/50 mΩ Low RDS-ON Power MOSFETs – Peak-Current-Mode Control – Short Minimum On-Time of 68 ns – Frequency: 400 kHz, 1.4 MHz, 2.1 MHz – Junction Temperature Range –40°C to +125°C – Integrated Synchronous Rectification – Integrated Compensation Network High Efficiency Solution – Peak Efficiency > 95% – Low Shutdown Quiescent Current of 5 µA – Low Operating Quiescent Current of 25 µA Flexible System Interface – Power-Good Flag and Precision Enable Create a Custom Design Using the LMR33620 with the WEBENCH® Power Designer • • PART NUMBER PACKAGE BODY SIZE (NOM) LMR33620 HSOIC (8) 5.00 mm × 4.00 mm LMR33620 VQFN (12) 3.00 mm × 2.00 mm (1) For all available packages, see the orderable addendum at the end of the data sheet. 2 Applications • Device Information(1) Motor Drive Systems: Drones, AC Inverters, VF Drives, Servos Factory and Building Automation Systems: PLC CPU, HVAC Control, Elevator Control General Purpose Wide VIN Power Supplies space space space space space Simplified Schematic Efficiency vs Output Current VOUT = 5 V, 400 kHz, VQFN BOOT VIN CIN 100 CBOOT EN SW L1 90 COUT PGND VCC 95 VOUT PG RFBT CVCC Efficiency (%) VIN 85 80 75 8V 70 FB AGND RFBB 12V 65 24V 60 36V 55 0.01 0.1 Output Current (A) 1 10 C024 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. LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Device Comparison Table..................................... Pin Configuration and Functions ......................... Specifications......................................................... 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 8 1 1 1 2 3 3 5 Absolute Maximum Ratings ...................................... 5 ESD Ratings.............................................................. 5 Recommended Operating Conditions ...................... 5 Thermal Information .................................................. 6 Electrical Characteristics........................................... 6 Timing Characteristics............................................... 8 System Characteristics ............................................. 9 Typical Characteristics ............................................ 10 Detailed Description ............................................ 11 8.1 Overview ................................................................. 11 8.2 Functional Block Diagram ....................................... 11 8.3 Feature Description................................................. 12 8.4 Device Functional Modes........................................ 16 9 Application and Implementation ........................ 19 9.1 Application Information............................................ 19 9.2 Typical Application .................................................. 19 9.3 Do's and Don'ts ....................................................... 31 10 Power Supply Recommendations ..................... 32 11 Layout................................................................... 33 11.1 Layout Guidelines ................................................. 33 11.2 Layout Example .................................................... 35 12 Device and Documentation Support ................. 37 12.1 12.2 12.3 12.4 12.5 12.6 12.7 Device Support .................................................... Documentation Support ........................................ Receiving Notification of Documentation Updates Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 37 37 37 37 38 38 38 13 Mechanical, Packaging, and Orderable Information ........................................................... 38 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Original (February 2018) to Revision A • 2 Page Added WSON information throughout data sheet .................................................................................................................. 1 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 5 Device Comparison Table DEVICE NUMBER PACKAGE FREQUENCY RATED CURRENT 400 kHz 2A 1400 kHz 2A LMR33620CDDA 2100 kHz 2A LMR33620ARNX 400 kHz 2A 1400 kHz 2A 2100 kHz 2A LMR33620ADDA LMR33620BDDA LMR33620BRNX DDA (8-pin HSOIC) 5.0 × 4.0 mm RNX (12-pin VQFN) 3.0 × 2.0 × 0.85 mm LMR33620CRNX OUTPUT VOLTAGE Adjustable Adjustable 6 Pin Configuration and Functions DDA Package 8-Pin HSOIC With PowerPAD™ Top View PGND 1 VIN 2 8 SW 7 BOOT THERMAL PAD EN 3 6 VCC PG 4 5 FB Not to scale RNX Package 12-Pin VQFN Top View SW 12 PGND 1 11 PGND VIN 2 10 VIN NC 3 9 EN BOOT 4 8 PG 5 VCC 6 7 AGND FB Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 3 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com Pin Functions PIN HSOIC TYPE DESCRIPTION VQFN NAME 1 1,11 PGND G Power ground terminal. Connect to system ground and AGND. Connect to CIN with short wide traces. 2 2,10 VIN P Input supply to regulator. Connect a high-quality bypass capacitor(s) directly to this pin and PGND. 3 9 EN A Enable input to regulator. High = ON, low = OFF. Can be connected directly to VIN; DO NOT FLOAT. 4 8 PG A Open drain power-good flag output. Connect to suitable voltage supply through a current limiting resistor. High = power OK, low = power bad. Flag pulls low when EN = Low. Can be open or grounded when not used. 5 7 FB A Feedback input to regulator. Connect to tap point of feedback voltage divider. DO NOT FLOAT. DO NOT GROUND. 6 5 VCC P Internal 5-V LDO output. Used as supply to internal control circuits. Do not connect to external loads. Can be used as logic supply for power-good flag. Connect a high quality 1-µF capacitor from this pin to GND. 7 4 BOOT P Boot-strap supply voltage for internal high-side driver. Connect a high-quality 100-nF capacitor from this pin to the SW pin. On the VQFN package connect the SW pin to NC on the PCB. This simplifies the connection from the CBOOT capacitor to the SW pin. 8 12 SW P Regulator switch node. Connect to power inductor. On the VQFN package connect the SW pin to NC on the PCB. This simplifies the connection from the CBOOT capacitor to the SW pin. THERMAL PAD 6 AGND G Analog ground for regulator and system. Ground reference for internal references and logic. All electrical parameters are measured with respect to this pin. Connect to system ground on PCB. For the HSOIC package, the pad on the bottom of the device serves as both the AGND connection and a thermal connection to the heat sink ground plane. This pad must be soldered to a ground plane to achieve good electrical and thermal performance. — 3 NC — On the VQFN package the SW pin must be connected to NC on the PCB. This simplifies the connection from the CBOOT capacitor to the SW pin. This pin has no internal connection to the regulator. A = Analog, P = Power, G = Ground 4 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 7 Specifications 7.1 Absolute Maximum Ratings Over the recommended operating junction temperature range (1) MIN MAX VIN to PGND PARAMETER –0.3 38 EN to AGND (2) –0.3 VIN + 0.3 FB to AGND –0.3 5.5 PG to AGND (2) 0 22 AGND to PGND –0.3 0.3 SW to PGND –0.3 VIN + 0.3 SW to PGND less than 100-ns transients –3.5 38 BOOT to SW –0.3 5.5 VCC to AGND (3) –0.3 5.5 TJ Junction temperature (4) –40 150 °C Tstg Storage temperature –55 150 °C Voltages (1) (2) (3) (4) UNIT V V 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. The voltage on this pin must not exceed the voltage on the VIN pin by more than 0.3 V Under some operating conditions the VCC LDO voltage may increase beyond 5.5V. Operating at junction temperatures greater than 125°C, although possible, degrades the lifetime of the device. 7.2 ESD Ratings VALUE V(ESD) (1) (2) Electrostatic discharge Human-body model (HBM) (1) UNIT ±2500 Charged-device model (CDM) (2) V ±750 JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. 7.3 Recommended Operating Conditions Over the recommended operating junction temperature range of –40 °C to 125 °C (unless otherwise noted) VIN to PGND Input voltage EN (2) PG (2) (3) Adjustable output voltage VOUT Output current IOUT Temperature Operating junction temperature, TJ (1) (2) (3) (4) (4) (1) MIN MAX 3.8 36 UNIT 0 VIN 0 18 1 24 0 2 A –40 125 °C V V Recommended operating conditions indicate conditions for which the device is intended to be functional, but do not ensure specific performance limits. For ensured specifications, see Electrical Characteristics. The voltage on this pin must not exceed the voltage on the VIN pin by more than 0.3 V. The maximum output voltage can be extended to 95% of VIN; contact TI for details. Under no conditions should the output voltage be allowed to fall below zero volts. Operating at junction temperatures greater than 125℃, although possible, degrades the lifetime of the device. Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 5 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com 7.4 Thermal Information LMR336x0 THERMAL METRIC (1) (2) DDA (HSOIC) RNX (VQFN) 8 PINS 12 PINS UNIT 42.9 72.5 °C/W RθJA Junction-to-ambient thermal resistance RθJC(top) Junction-to-case (top) thermal resistance 54 35.9 °C/W RθJB Junction-to-board thermal resistance 13.6 23.3 °C/W ψJT Junction-to-top characterization parameter 4.3 0.8 °C/W ψJB Junction-to-board characterization parameter 13.8 23.5 °C/W RθJC(bot) Junction-to-case (bottom) thermal resistance 4.3 N/A °C/W (1) (2) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report. The value of RθJA given in this table is only valid for comparison with other packages and can not be used for design purposes. These values were calculated in accordance with JESD 51-7, and simulated on a 4-layer JEDEC board. They do not represent the performance obtained in an actual application. For design information see Maximum Ambient Temperature. 7.5 Electrical Characteristics Limits apply over the recommended operating junction temperature (TJ) range of –40°C to +125°C, unless otherwise stated. Minimum and maximum limits are specified through test, design or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Unless otherwise stated, the following conditions apply: VIN = 12 V, VEN = 4 V. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT SUPPLY VOLTAGE VIN Minimum operating input voltage IQ Non-switching input current; measured at VIN pin (1) VFB = 1.2 V ISD Shutdown quiescent current; measured at VIN pin EN = 0 VEN-VCC-H EN input level required to turn on internal LDO Rising threshold VEN-VCC-L EN input level required to turn off internal LDO Falling threshold 0.3 VEN-H EN input level required to start switching Rising threshold 1.2 VEN-HYS Hysteresis below VEN-H Hysteresis below VEN-H; falling 100 mV ILKG-EN Enable input leakage current VEN = 3.3 V 0.2 nA 3.8 V 24 34 µA 5 10 µA 1 V ENABLE V 1.231 1.26 V INTERNAL SUPPLIES VCC Internal LDO output voltage appearing at the VCC pin VBOOT-UVLO Bootstrap voltage undervoltage lock-out threshold (2) 6 V ≤ VIN ≤ 36 V 4.75 5 5.25 2.2 V V VOLTAGE REFERENCE (FB PIN) VFB Feedback voltage IFB Current into FB pin 0.985 FB = 1 V 1 1.015 V 0.2 50 nA 3.5 4 A CURRENT LIMITS (3) ISC (1) (2) (3) 6 High-side current limit LMR33620 2.9 This is the current used by the device open loop. It does not represent the total input current of the system when in regulation. When the voltage across the CBOOT capacitor falls below this voltage, the low side MOSFET is turned on to recharge CBOOT. The current limit values in this table are tested, open loop, in production. They may differ from those found in a closed loop application. Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 Electrical Characteristics (continued) Limits apply over the recommended operating junction temperature (TJ) range of –40°C to +125°C, unless otherwise stated. Minimum and maximum limits are specified through test, design or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Unless otherwise stated, the following conditions apply: VIN = 12 V, VEN = 4 V. PARAMETER TEST CONDITIONS ILIMIT Low-side current limit LMR33620 IPEAK-MIN Minimum peak inductor current LMR33620 IZC Zero current detector threshold MIN TYP MAX 1.95 2.45 2.9 UNIT A 0.65 A 0.01 A SOFT START tSS Internal soft-start time 2.9 4 6 ms POWER GOOD (PG PIN) VPG-HIGH-UP Power-good upper threshold - rising % of FB voltage 105% 107% 110% VPG-HIGH-DN Power-good upper threshold - falling % of FB voltage 103% 105% 108% VPG-LOW-UP Power-good lower threshold - rising % of FB voltage 92% 94% 97% VPG-LOW-DN Power-good lower threshold - falling % of FB voltage 90% 92% 95% tPG Power-good glitch filter delay (4) RPG Power-good flag RDSON VIN-PG Minimum input voltage for proper PG function 50-µA, EN = 0 V VPG PG logic low output 50-µA, EN = 0 V, VIN = 2V ƒSW Switching frequency "A" Version 340 400 460 kHz ƒSW Switching frequency "B" Version 1.2 1.4 1.6 MHz ƒSW Switching frequency "C" Version, DDA package 1.8 2.1 2.4 MHz ƒSW Switching frequency "C" Version, RNX package 1.8 2.1 2.3 MHz 60 170 VIN = 12 V, VEN = 4 V 76 150 VEN = 0 V 35 60 µs Ω 2 V 0.2 V OSCILLATOR (4) See Power-Good Flag Output for details. Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 7 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com Electrical Characteristics (continued) Limits apply over the recommended operating junction temperature (TJ) range of –40°C to +125°C, unless otherwise stated. Minimum and maximum limits are specified through test, design or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Unless otherwise stated, the following conditions apply: VIN = 12 V, VEN = 4 V. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT MOSFETS RDS-ON-HS High-side MOSFET ONresistance RNX package 75 145 mΩ RDS-ON-HS High-side MOSFET ONresistance DDA package 95 160 mΩ RDS-ON-LS Low-side MOSFET ONresistance RNX package 50 95 mΩ RDS-ON-LS Low-side MOSFET ONresistance DDA package 66 110 mΩ 7.6 Timing Characteristics Limits apply over the recommended operating junction temperature (TJ) range of –40°C to +125°C, unless otherwise stated. Minimum and maximum limits are specified through test, design or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Unless otherwise stated, the following conditions apply: VIN = 12 V, VEN = 4 V. NOM MAX tON-MIN Minimum switch on-time RNX package MIN 68 80 ns tON-MIN Minimum switch on-time DDA package 75 108 ns tOFF-MIN Minimum switch off-time RNX package 52 70 ns tOFF-MIN Minimum switch off-time DDA package 50 85 ns tON-MAX Maximum switch on-time 7 9 µs 8 Submit Documentation Feedback UNIT Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 7.7 System Characteristics The following specifications apply to a typical applications circuit, with nominal component values. Specifications in the typical (TYP) column apply to TJ = 25°C only. Specifications in the minimum (MIN) and maximum (MAX) columns apply to the case of typical components over the temperature range of TJ = –40°C to 125°C. These specifications are not ensured by production testing. PARAMETER VIN Operating input voltage range Output voltage regulation for VOUT = 5 V (1) VOUT Output voltage regulation for VOUT = 3.3 V (1) TEST CONDITIONS VOUT = 3.3 V, IOUT= 0 A MIN TYP MAX 3.8 36 VOUT = 5 V, VIN = 7 V to 36 V, IOUT = 0 A to max. load –1.5% 2.5% VOUT = 5 V, VIN = 7 V to 36 V, IOUT = 1 A to max. load –1.5% 1.5% VOUT = 3.3 V, VIN = 3.8 V to 36 V, IOUT = 0 A to max. load –1.5% 2.5% VOUT = 3.3 V, VIN = 3.8 V to 36 V, IOUT = 1 A to max. load –1.5% 1.5% UNIT V ISUPPLY Input supply current when in regulation VIN = 12 V, VOUT = 3.3 V, IOUT = 0 A, RFBT = 1 MΩ VDROP Dropout voltage; (VIN – VOUT) DMAX Maximum switch duty cycle (2) VHC FB pin voltage required to trip shortcircuit hiccup mode 0.4 V tHC Time between current-limit hiccup burst 94 ms tD Switch voltage dead time TSD (1) (2) Thermal shutdown temperature 25 µA VOUT = 5 V, IOUT = 1A Dropout at –1% of regulation, ƒSW = 140 kHz 150 mV VIN = VOUT = 12 V, IOUT = 1 A 98% 2 ns Shutdown temperature 165 °C Recovery temperature 148 °C Deviation is with respect to VIN =12 V, IOUT = 1 A. In dropout the switching frequency drops to increase the effective duty cycle. The lowest frequency is clamped at approximately: ƒMIN = 1 / (tON-MAX + tOFF-MIN). DMAX = tON-MAX /(tON-MAX + tOFF-MIN). Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 9 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com 7.8 Typical Characteristics Unless otherwise specified the following conditions apply: TA = 25°C and VIN = 12 V 36 12 11 10 Shutdown Current (µA) Quiescent Current (µA) 34 32 30 28 26 -40C 24 25C 22 5 10 15 20 25 30 35 Input Voltage (V) 8 7 6 5 4 3 -40C 2 25C 1 125C 20 0 9 0 0 40 15 20 25 30 35 40 Input Voltage (V) C003 EN = 0 V Figure 1. Non-Switching Input Supply Current Figure 2. Shutdown Supply Current 600 1.35 590 1.30 EN Threshold Voltage (V) 580 Output Current (A) 10 C005 VFB = 1.2 V 570 560 550 540 530 -40C 520 25C 510 500 0 125C 5 1.25 1.20 1.15 1.10 UP 1.05 125C DN 1.00 5 10 15 20 25 30 35 Input Voltage (V) VOUT = 0 V ƒS = 400 kHz 40 ±40 ±20 0 20 40 60 80 100 120 140 Temperature (C) C007 C006 See Figure 47 Figure 3. Short-Circuit Output Current Figure 4. Precision Enable Thresholds DN Peak Inductor Current (mA) OUTPUT VOLTAGE (0.8V/Div) 700 UP 650 600 550 500 -40C 450 125C 400 0 0 INPUT VOLTAGE (1V/Div) IOUT = 1 mA 5 10 15 20 25 Input Voltage (V) See Figure 47 IOUT = 0 A ƒSW = 400 kHz VOUT = 5 V 30 35 40 C008 See Figure 47 Figure 6. IPEAK-MIN Figure 5. UVLO Thresholds 10 25C Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 8 Detailed Description 8.1 Overview The LMR33620 is a synchronous peak-current-mode buck regulator designed for a wide variety of industrial applications. The regulator automatically switches modes between PFM and PWM depending on load. At heavy load, the device operates in PWM at a constant switching frequency. At light loads the mode changes to PFM, with diode emulation allowing DCM. This reduces the input supply current and keeps efficiency high. The device features internal loop compensation which reduces design time and requires fewer external components than externally compensated regulators. 8.2 Functional Block Diagram VIN VCC INT. REG. BIAS OSCILLATOR EN ENABLE LOGIC BOOT HS CURRENT SENSE 1.0V Reference PWM COMP. ERROR AMPLIFIER FB + - + - PG CONTROL LOGIC PFM MODE CONTROL SW DRIVER LS CURRENT SENSE POWER GOOD CONTROL AGND PGND Copyright © 2017, Texas Instruments Incorporated Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 11 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com 8.3 Feature Description 8.3.1 Power-Good Flag Output The power-good flag function (PG output pin) of the LMR33620 can be used to reset a system microprocessor whenever the output voltage is out of regulation. This open-drain output goes low under fault conditions, such as current limit and thermal shutdown, as well as during normal start-up. A glitch filter prevents false flag operation for short excursions of the output voltage, such as during line and load transients. The timing parameters of the glitch filter are found in the Electrical Characteristics table. Output voltage excursions lasting less than tPG do not trip the power-good flag. Power-good operation can best be understood by reference to Figure 7 and Figure 8. Note that during initial power-up a delay of about 4 ms (typical) is inserted from the time that EN is asserted to the time that the power-good flag goes high. This delay only occurs during start-up and is not encountered during normal operation of the power-good function. The power-good output consists of an open drain NMOS; requiring an external pull up resistor to a suitable logic supply. It can also be pulled up to either VCC or VOUT, through a 100-kΩ resistor, as desired. If this function is not needed, the PG pin should be left floating. When EN is pulled low, the flag output is also forced low. With EN low, power good remains valid as long as the input voltage is ≥ 2 V (typical). Limit the current into the powergood flag pin to less than 5 mA D.C. The maximum current is internally limited to about 35 mA when the device is enabled and about 65 mA when the device is disabled. The internal current limit protects the device from any transient currents that may occur when discharging a filter capacitor connected to this output. VOUT VPG-HIGH_UP (107%) VPG-HIGH-DN (105%) VPG-LOW-UP (95%) VPG-LOW-DN (93%) PG High = Power Good Low = Fault Figure 7. Static Power-Good Operation 12 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 Feature Description (continued) Glitches do not cause false operation nor reset timer VOUT VPG-LOW-UP (95%) VPG-LOW-DN (93%) < tPG PG tPG tPG tPG Figure 8. Power-Good-Timing Behavior 8.3.2 Enable and Start-up Start-up and shutdown are controlled by the EN input. This input features precision thresholds, allowing the use of an external voltage divider to provide an adjustable input UVLO (see the External UVLO section). Applying a voltage of ≥ VEN-VCC_H causes the device to enter standby mode, powering the internal VCC, but not producing an output voltage. Increasing the EN voltage to VEN-H fully enables the device, allowing it to enter start-up mode and beginning the soft-start period. When the EN input is brought below VEN-H by VEN-HYS, the regulator stops running and enters standby mode. Further decrease in the EN voltage to below VEN-VCC-L completely shuts down the device. This behavior is shown in Figure 9. The EN input may be connected directly to VIN if this feature is not needed. This input must not be allowed to float. The values for the various EN thresholds can be found in the Electrical Characteristics table. The LMR33620 utilizes a reference-based soft start that prevents output voltage overshoots and large inrush currents as the regulator is starting up. A typical start-up waveform is shown in Figure 10 along with typical timings. The rise time of the output voltage is about 4 ms (see Electrical Characteristics). Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 13 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com Feature Description (continued) EN VEN-H VEN-H ± VEN-HYS VEN-VCC-H VEN-VCC-L VCC 5V 0 VOUT VOUT 0 Figure 9. Precision Enable Behavior 14 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 Feature Description (continued) EN, 4V/Div VOUT, 2V/Div PG, 5V/Div Inductor Current, 2A/Div 2ms/Div Figure 10. Typical Start-up Behavior VIN = 12 V, VOUT = 5 V, IOUT = 2 A 8.3.3 Current Limit and Short Circuit The LMR33620 incorporates valley current limit for normal overloads and for short-circuit protection. In addition the high-side power MOSFET is protected from excessive current by a peak current limit circuit. Cycle-by-cycle current limit is used for overloads, while hiccup mode is used for short circuits. Finally, a zero current detector is used on the low-side power MOSFET to implement DEM at light loads (see Glossary). The typical value of this current limit is found under IZC in the Electrical Characteristics. During overloads the low-side current limit, ILIMIT, (see Electrical Characteristics table) determines the maximum load current that the LMR33620 can supply. When the low-side switch turns on, the inductor current begins to ramp down. If the current does not fall below ILIMIT before the next turn-on cycle, then that cycle is skipped, and the low-side MOSFET is left on until the current falls below ILIMIT. This is somewhat different than the more typical peak current limit and results in Equation 1 for the maximum load current. IOUT max ILIMIT VIN VOUT VOUT ˜ 2 ˜ fSW ˜ L VIN where • • fSW = Switching frequency L = Inductor value (1) If, during current limit, the voltage on the FB input falls below about 0.4 V, due to a short circuit, the device enters into hiccup mode. In this mode the device stops switching for tHC (see System Characteristics), or about 94 ms and then goes through a normal re-start with soft start. If the short-circuit condition remains, the device runs in current limit for about 20 ms (typical) and then shuts down again. This cycle repeats, as shown in as long as the short-circuit-condition persists. This mode of operation helps to reduce the temperature rise of the device during a hard short on the output. The output current is greatly reduced during hiccup mode (see Typical Characteristics). Once the output short is removed, and the hiccup delay is passed, the output voltage recovers normally as shown in The high-side-current limit trips when the peak inductor current reaches ISC (see Electrical Characteristics table). This is a cycle-by-cycle current limit and does not produce any frequency or load current fold back. It is meant to protect the high-side MOSFET from excessive current. Under some conditions, such as high input voltages, this current limit may trip before the low-side protection. Under this condition, ISC determines the maximum output current. Note that ISC varies with duty cycle. Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 15 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com Feature Description (continued) Short Applied Short Removed VOUT, 2V/Div Inductor Current, 1A/Div 50ms/Div Inductor Current, 1A/Div 50ms/Div Figure 11. Inductor Current Burst in Short-Circuit Mode Figure 12. Short-Circuit Transient and Recovery 8.3.4 Undervoltage Lockout and Thermal Shutdown The LMR33620 incorporates an undervoltage-lockout feature on the output of the internal LDO (at the VCC pin). When VCC reaches about 3.7 V the device is ready to receive an EN signal and start up. When VCC falls below about 3 V the device shuts down, regardless of EN status. Since the LDO is in dropout during these transitions, the above values roughly represent the input voltage levels during the transitions. Thermal shutdown is provided to protect the regulator from excessive junction temperature. When the junction temperature reaches about 165°C the device shuts down; re-start occurs when the temperature falls to about 148°C . 8.4 Device Functional Modes 8.4.1 Auto Mode In auto mode the device moves between PWM and PFM as the load changes. At light loads the regulator operates in PFM. At higher loads the mode changes to PWM. The load current for which the device moves from PFM to PWM can be found in the Application Curves. The output current at which the device changes modes depends somewhat on the input voltage, inductor value and the nominal switching frequency. For output currents above the curve, the device is in PWM mode. For currents below the curve, the device is in PFM. The curves apply for a nominal switching frequency of 400 kHz and the BOM shown in Table 4. At higher switching frequencies the load at which the mode change occurs will be greater. For applications where the switching frequency must be known for a given condition, the above mentioned effects must be carefully tested before the design is finalized. In PWM the regulator operates as a constant frequency, current mode, full synchronous converter using PWM to regulate the output voltage. While operating in this mode the output voltage is regulated by switching at a constant frequency and modulating the duty cycle to control the power to the load. This provides excellent line and load regulation and low output voltage ripple. In PFM the high-side MOSFET is turned on in a burst of one or more pulses to provide energy to the load. The duration of the burst depends on how long it takes the inductor current to reach IPEAK-MIN. The frequency of these bursts is adjusted to regulate the output, while diode emulation (DEM) is used to maximize efficiency (see Glossary). This mode provides high light-load efficiency by reducing the amount of input supply current required to regulate the output voltage at small loads. This trades off very good light-load efficiency for larger output voltage ripple and variable switching frequency. Also, a small increase in output voltage occurs at light loads. The actual switching frequency and output voltage ripple depends on the input voltage, output voltage, and load. Typical switching waveforms in PFM and PWM are shown in Figure 13 and Figure 14. See the Application Curves for output voltage variation with load in auto mode. 16 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 Device Functional Modes (continued) SW, 5V/Div SW, 5V/Div VOUT, 10mV/Div VOUT, 10mV/Div Inductor Current, 1A/Div Inductor Current, 0.5A/Div 2µs/Div 50µs/Div Figure 14. Typical PWM Switching Waveforms VIN = 12 V, VOUT = 5 V, IOUT = 2 A, ƒS = 400 kHz Figure 13. Typical PFM Switching Waveforms VIN = 12 V, VOUT = 5 V, IOUT = 10 mA 8.4.2 Dropout 6 0.3 5.5 0.25 Drop-out Voltage (V) Output Voltage (V) The dropout performance of any buck regulator is affected by the RDSON of the power MOSFETs, the DC resistance of the inductor, and the maximum duty cycle that the controller can achieve. As the input voltage is reduced to near the output voltage, the off-time of the high side MOSFET starts to approach the minimum value (see Timing Characteristics). Beyond this point the switching may become erratic, and/or the output voltage falls out of regulation. To avoid this problem the LMR33620 automatically reduces the switching frequency to increase the effective duty cycle and maintain regulation. In this data sheet the dropout voltage is defined as the difference between the input and output voltage when the output has dropped by 1% of its nominal value. Under this condition the switching frequency has dropped to its minimum value of about 140 kHz. Note that the 0.4 V short circuit detection threshold is not activated when in dropout mode. Typical drop-out characteristics can be found in Figure 15 and Figure 16. 5 4.5 4 0A 3.5 5 5.5 6 6.5 Input Voltage (V) 0.1 3.3V 5V 2A 0 3 4.5 0.15 0.05 1A 4 0.2 7 0 Figure 15. Overall Dropout Characteristic VOUT = 5 V 0.5 1 1.5 2 Output Current (A) C002 2.5 C001 Figure 16. Typical Drop-out Voltage vs Output Current ƒSW = 140 kHz Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 17 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com Device Functional Modes (continued) 8.4.3 Minimum Switch On-Time Every switching regulator has a minimum controllable on-time dictated by the inherent delays and blanking times associated with the control circuits. This imposes a minimum switch duty cycle and therefore a minimum conversion ratio. The constraint is encountered at high input voltages and low output voltages. To help extend the minimum controllable duty cycle, the LMR33620 automatically reduces the switching frequency when the minimum on-time limit is reached. In this way the converter can regulate the lowest programmable output voltage at the maximum input voltage. An estimate for the approximate input voltage, for a given output voltage, before frequency fold-back occurs is found in Equation 2. The values of tON and fSW can be found in the Electrical Characteristics table. As the input voltage is increased, the switch on-time (duty-cycle) reduces to regulate the output voltage. When the on-time reaches the limit, the switching frequency drops, while the on-time remains fixed. This relationship is highlighted in Figure 17 for a nominal switching frequency of 2.1 MHz. VOUT VIN d t ON ˜ fSW (2) Switching Frequency (MHz) 2.4 2.2 2 1.8 1.6 1.4 1.2 3.3V 1 10 15 20 25 30 Input Voltage (V) 35 40 C017 Figure 17. Switching Frequency vs Input Voltage VOUT = 3.3 V, IOUT = 1 A 18 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 9 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. NOTE In this data sheet the effective value of capacitance is defined as the actual capacitance under D.C. bias and temperature; not the rated or nameplate values. Use high-quality, low-ESR, ceramic capacitors with an X5R or better dielectric throughout. All high value ceramic capacitors have a large voltage coefficient in addition to normal tolerances and temperature effects. Under D.C. bias the capacitance drops considerably. Large case sizes and/or higher voltage ratings are better in this regard. To help mitigate these effects, multiple capacitors can be used in parallel to bring the minimum effective capacitance up to the required value. This can also ease the RMS current requirements on a single capacitor. A careful study of bias and temperature variation of any capacitor bank should be made in order to ensure that the minimum value of effective capacitance is provided. 9.1 Application Information The LMR33620 step-down DC-to-DC converter is typically used to convert a higher DC voltage to a lower DC voltage with a maximum output current of 2 A. The following design procedure can be used to select components for the LMR33620. Alternately, the WEBENCH® Design Tool may be used to generate a complete design. This tool utilizes an iterative design procedure and has access to a comprehensive database of components. This allows the tool to create an optimized design and allows the user to experiment with various options. 9.2 Typical Application shows a typical application circuit for the LMR33620. This device is designed to function over a wide range of external components and system parameters. However, the internal compensation is optimized for a certain range of external inductance and output capacitance. As a quick start guide, Table 2 provides typical component values for a range of the most common output voltages. The values given in the table are typical. Other values may be used to enhance certain performance criterion as required by the application. L VIN 6 V to 36 V CIN 10 µF VOUT SW VIN 5V 2A 10 µH CHF CBOOT 220 nF COUT BOOT EN 4x 22 µF 0.1 µF RFBT CFF PG 100 NŸ PG 100 NŸ VCC CVCC 1 µF FB PGND AGND RFBB 24.9 NŸ Figure 18. Example Application Circuit (400 kHz) Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 19 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com Typical Application (continued) 9.2.1 Design Requirements Table 1 provides the parameters for our detailed design procedure example: Table 1. Detailed Design Parameters DESIGN PARAMETER EXAMPLE VALUE Input voltage 12 V (6 V to 36 V) Output voltage 5V Maximum output current 0 A to 2 A Switching frequency 400 kHz Table 2. Typical External Component Values ƒSW (kHz) VOUT (V) L (µH) COUT (rated capacitance) RFBT (Ω) RFBB (Ω) CIN + CHF CBOOT CVCC CFF 400 3.3 10 4 × 22 µF 100 k 43.2 k 10 µF + 220 nF 100 nF 1 µF open 1400 3.3 2.2 2 × 22 µF 100 k 43.2 k 10 µF + 220 nF 100 nF 1 µF open 2100 3.3 1.2 2 × 22 µF 100 k 43.2 k 10 µF + 220 nF 100 nF 1 µF open 400 5 10 4 × 22 µF 100 k 24.9 k 10 µF + 220 nF 100 nF 1 µF open 1400 5 2.2 2 × 22 µF 100 k 24.9 k 10 µF + 220 nF 100 nF 1 µF open 2100 5 1.5 2 × 22 µF 100 k 24.9 k 10 µF + 220 nF 100 nF 1 µF open 400 12 27 4 × 22 µF 100 k 9.09 k 10 µF + 220 nF 100 nF 1 µF open 1400 12 4.7 4 × 10 µF 100 k 9.09 k 10 µF + 220 nF 100 nF 1 µF open 2100 12 3.3 4 × 10 µF 100 k 9.09 k 10 µF + 220 nF 100 nF 1 µF open 9.2.2 Detailed Design Procedure The following design procedure applies to Figure 18 and Table 1. 9.2.2.1 Custom Design With WEBENCH® Tools Click here to create a custom design using the LMR33620 device with the WEBENCH® Power Designer. 1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements. 2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial. 3. Compare the generated design with other possible solutions from Texas Instruments. The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time pricing and component availability. In most cases, these actions are available: • Run electrical simulations to see important waveforms and circuit performance • Run thermal simulations to understand board thermal performance • Export customized schematic and layout into popular CAD formats • Print PDF reports for the design, and share the design with colleagues Get more information about WEBENCH tools at www.ti.com/WEBENCH. 9.2.2.2 Choosing the Switching Frequency The choice of switching frequency is a compromise between conversion efficiency and overall solution size. Lower switching frequency implies reduced switching losses and usually results in higher system efficiency. However, higher switching frequency allows the use of smaller inductors and output capacitors, and hence a more compact design. For this example we choose 400 kHz. 20 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 9.2.2.3 Setting the Output Voltage The output voltage of LMR33620 is externally adjustable using a resistor divider network. The range of recommended output voltage is found in the Recommended Operating Conditions table. The divider network is comprised of RFBT and RFBB, and closes the loop between the output voltage and the converter. The converter regulates the output voltage by holding the voltage on the FB pin equal to the internal reference voltage, VREF. The resistance of the divider is a compromise between excessive noise pick-up and excessive loading of the output. Smaller values of resistance reduce noise sensitivity but also reduce the light-load efficiency. The recommended value for RFBT is 100 kΩ; with a maximum value of 1 MΩ. If a 1 MΩ is selected for RFBT, then a feed-forward capacitor must be used across this resistor to provide adequate loop phase margin (see CFF Selection). Once RFBT is selected, Equation 3 is used to select RFBB. VREF is nominally 1 V (see Electrical Characteristics for limits). RFBT RFBB ª VOUT º 1» « ¬ VREF ¼ (3) For this 5-V example, RFBT = 100 kΩ and RFBB = 24.9 kΩ are chosen. 9.2.2.4 Inductor Selection The parameters for selecting the inductor are the inductance and saturation current. The inductance is based on the desired peak-to-peak ripple current and is normally chosen to be in the range of 20% to 40% of the maximum output current. Experience shows that the best value for inductor ripple current is 30% of the maximum load current. Note that when selecting the ripple current for applications with much smaller maximum load than the maximum available from the device, the maximum device current should be used. Equation 4 can be used to determine the value of inductance. The constant K is the percentage of inductor current ripple. For this example we choose K = 0.3 and find an inductance ; we select the next standard value of 10 µH. L VIN VOUT V ˜ OUT fSW ˜ K ˜ IOUT max VIN (4) Ideally, the saturation current rating of the inductor should be at least as large as the high-side switch current limit, ISC (see Electrical Characteristics ). This ensures that the inductor does not saturate even during a short circuit on the output. When the inductor core material saturates, the inductance falls to a very low value, causing the inductor current to rise very rapidly. Although the valley current limit, ILIMIT, is designed to reduce the risk of current run-away, a saturated inductor can cause the current to rise to high values very rapidly. This may lead to component damage; do not allow the inductor to saturate! Inductors with a ferrite core material have very hard saturation characteristics, but usually have lower core losses than powdered iron cores. Powered iron cores exhibit a soft saturation, allowing some relaxation in the current rating of the inductor. However, they have more core losses at frequencies above about 1 MHz. In any case the inductor saturation current should not be less than the device low-side current limit, ILIMIT (see Electrical Characteristics). In order to avoid sub-harmonic oscillation, the inductance value should not be less than that given in Equation 5 The maximum inductance is limited by the minimum current ripple required for the current mode control to perform correctly. As a rule-ofthumb, the minimum inductor ripple current should be no less than about 10% of the device maximum rated current under nominal conditions. V LMIN t 0.36 ˜ OUT fSW (5) Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 21 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com 9.2.2.5 Output Capacitor Selection The value of the output capacitor, and its ESR, determine the output voltage ripple and load transient performance. The output capacitor bank is usually limited by the load transient requirements, rather than the output voltage ripple. Equation 6 can be used to estimate a lower bound on the total output capacitance, and an upper bound on the ESR, required to meet a specified load transient. º ª 'IOUT K2 COUT t ˜«1 D ˜ 1 K ˜ 2 D» 12 fSW ˜ 'VOUT ˜ K ¬« ¼» ESR d D 2 K ˜ 'VOUT ª 2 ˜ 'IOUT «1 K ¬« K2 12 § 1 ·º ¸¸» ˜ ¨¨1 © (1 D) ¹¼» VOUT VIN where • • • ΔVOUT = output voltage transient ΔIOUT = output current transient K = Ripple factor from Inductor Selection (6) Once the output capacitor and ESR have been calculated, Equation 7 can be used to check the peak-to-peak output voltage ripple; Vr. Vr # 'IL ˜ ESR 2 1 8 ˜ fSW ˜ COUT 2 (7) The output capacitor and ESR can then be adjusted to meet both the load transient and output ripple requirements. For this example we require a ΔVOUT of ≤ 250 mV for an output current step of ΔIOUT = 2 A. Equation 6 gives a minimum value of 45 µF and a maximum ESR of 0.11 Ω. Assuming a 20% tolerance and a 10% bias de-rating, we arrive at a minimum capacitance of 63 µF. This can be achieved with a bank of 4 × 22-µF, 16-V, ceramic capacitors in the 1210 case size. More output capacitance can be used to improve the load transient response. Ceramic capacitors can easily meet the minimum ESR requirements. In some cases an aluminum electrolytic capacitor can be placed in parallel with the ceramics to help build up the required value of capacitance. In general use a capacitor of at least 10 V for output voltages of 3.3 V or less, while a capacitor of 16 V or more should be used for output voltages of 5 V and above. In practice the output capacitor has the most influence on the transient response and loop phase margin. Load transient testing and Bode plots are the best way to validate any given design and should always be completed before the application goes into production. In addition to the required output capacitance, a small ceramic placed on the output can help to reduce high frequency noise. Small case size ceramic capacitors in the range of 1 nF to 100 nF can be very helpful in reducing spikes on the output caused by inductor and board parasitics. The maximum value of total output capacitance should be limited to about 10 times the design value, or 1000 µF, whichever is smaller. Large values of output capacitance can adversely affect the start-up behavior of the regulator as well as the loop stability. If values larger than noted here must be used, then a careful study of startup at full load and loop stability must be performed. 9.2.2.6 Input Capacitor Selection The ceramic input capacitors provide a low impedance source to the regulator in addition to supplying the ripple current and isolating switching noise from other circuits. A minimum of 10 µF of ceramic capacitance is required on the input of the LMR33620. This must be rated for at least the maximum input voltage that the application requires; preferably twice the maximum input voltage. This capacitance can be increased to help reduce input voltage ripple and/or maintain the input voltage during load transients. In addition a small case size 220-nF ceramic capacitor must be used at the input, as close a possible to the regulator. This provides a high frequency 22 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 bypass for the control circuits internal to the device. For this example a 10-µF, 50-V, X7R (or better) ceramic capacitor is chosen. The 220 nF must also be rated at 50 V with an X7R dielectric. The VQFN (RNX) package provides two input voltage pins and two power ground pins on opposite sides of the package. This allows the input capacitors to be split, and placed optimally with respect to the internal power MOSFETs, thus improving the effectiveness of the input bypassing. In this example, place two 4.7-µF and two 100-nF ceramic capacitors at each VIN/PGND location. A single 10-µF can also be used on one side of the package. Many times it is desirable to use an electrolytic capacitor on the input in parallel with the ceramics. This is especially true if long leads/traces are used to connect the input supply to the regulator. The moderate ESR of this capacitor can help damp any ringing on the input supply caused by the long power leads. The use of this additional capacitor also helps with voltage dips caused by input supplies with unusually high impedance. Most of the input switching current passes through the ceramic input capacitor(s). The approximate RMS value of this current can be calculated from Equation 8 and should be checked against the manufacturers' maximum ratings. I IRMS # OUT 2 (8) 9.2.2.7 CBOOT The LMR33620 requires a boot-strap capacitor connected between the BOOT pin and the SW pin. This capacitor stores energy that is used to supply the gate drivers for the power MOSFETs. A high-quality ceramic capacitor of 100 nF and at least 10 V is required. 9.2.2.8 VCC The VCC pin is the output of the internal LDO used to supply the control circuits of the regulator. This output requires a 1-µF, 16-V ceramic capacitor connected from VCC to GND for proper operation. In general avoid loading this output with any external circuitry. However, this output can be used to supply the pullup for the power-good function (see Power-Good Flag Output). A value of 100 kΩ is a good choice in this case. The nominal output voltage on VCC is 5 V; see Electrical Characteristics for limits. Do not short this output to ground or any other external voltage. 9.2.2.9 CFF Selection In some cases a feed-forward capacitor can be used across RFBT to improve the load transient response or improve the loop-phase margin. This is especially true when values of RFBT > 100 kΩ are used. Large values of RFBT, in combination with the parasitic capacitance at the FB pin, can create a small signal pole that interferes with the loop stability. A CFF can help to mitigate this effect. Equation 9 can be used to estimate the value of CFF. The value found with Equation 9 is a starting point; use lower values to determine if any advantage is gained by the use of a CFF capacitor. The application report Optimizing Transient Response of Internally Compensated DCDC Converters with Feed-forward Capacitor is helpful when experimenting with a feed-forward capacitor. VOUT ˜ COUT CFF VREF 120 ˜ RFBT ˜ VOUT (9) 9.2.2.10 External UVLO In some cases an input UVLO level different than that provided internal to the device is needed. This can be accomplished by using the circuit shown in Figure 19. The input voltage at which the device turns on is designated VON; while the turnoff voltage is VOFF. First a value for RENB is chosen in the range of 10 kΩ to 100 kΩ and then Equation 10 is used to calculate RENT and VOFF. Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 23 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com VIN RENT EN RENB Figure 19. Set-Up for External UVLO Application RENT § VON ¨¨ © VEN H VOFF § VEN HYS VON ˜ ¨¨1 VEN © · 1¸¸ ˜ RENB ¹ · ¸¸ ¹ where • • VON = VIN turnon voltage VOFF = VIN turnoff voltage (10) 9.2.2.11 Maximum Ambient Temperature As with any power conversion device, the LMR33620 dissipates internal power while operating. The effect of this power dissipation is to raise the internal temperature of the converter above ambient. The internal die temperature (TJ) is a function of the ambient temperature, the power loss and the effective thermal resistance, RθJA of the device and PCB combination. The maximum internal die temperature for the LMR33620 must be limited to 125°C. This establishes a limit on the maximum device power dissipation and therefore the load current. Equation 11 shows the relationships between the important parameters. It is easy to see that larger ambient temperatures (TA) and larger values of RθJA reduce the maximum available output current. The converter efficiency can be estimated by using the curves provided in this data sheet. If the desired operating conditions can not be found in one of the curves, then interpolation can be used to estimate the efficiency. Alternatively, the EVM can be adjusted to match the desired application requirements and the efficiency can be measured directly. The correct value of RθJA is more difficult to estimate. As stated in Semiconductor and IC Package Thermal Metrics, the value of RθJA given in the Thermal Information table is not valid for design purposes and must not be used to estimate the thermal performance of the application. The values reported in that table were measured under a specific set of conditions that are rarely obtained in an actual application. IOUT MAX TJ TA 1 K ˜ ˜ R TJA 1 K VOUT where • η = Efficiency (11) The effective RθJA is a critical parameter and depends on many factors such as power dissipation, air temperature/flow, PCB area, copper heat-sink area, number of thermal vias under the package, and adjacent component placement; to mention just a few. The HSOIC (DDA) package utilizes a die attach paddle, or thermal pad (PAD) to provide a place to solder down to the PCB heat-sinking copper. This provides a good heat conduction path from the regulator junction to the heat sink and must be properly soldered to the PCB heat sink copper. Due to the ultra-miniature size of the VQFN (RNX) package, a DAP is not available. This means that this package exhibits a somewhat large value RθJA. Typical examples of RθJA vs copper board area can be found in Figure 20 and Figure 21. The copper area given in the graph is for each layer; the top and bottom layers are 2 oz. copper each, while the inner layers are 1 oz. A typical curve of maximum output current vs. ambient temperature is shown in Figure 22. This data was taken with a device/PCB combination giving an RθJA of about 30°C/W. It must be remembered that the data given in these graphs are for illustration purposes only, and the actual performance in any given application depends on all of the previously mentioned factors. 24 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 44 42 40 R JA (ƒC/W) 38 36 34 32 30 28 26 24 22 DDA, 4L 20 0 10 20 30 40 50 60 70 Copper Area (cm2) C003 Figure 20. Typical RθJA vs Copper Area for a Four-Layer Board and the HSOIC (DDA) Package 70 60 55 R JA (ƒC/w) 65 50 45 RNX, 4L 40 0 10 20 30 40 50 60 70 Copper Area (cm2) C005 Figure 21. RθJA vs Copper Board Area for the VQFN (RNX) Package Maximum Output Current (A) 3 2.5 2 1.5 1 0.5 0 20 30 40 50 60 70 80 90 100 110 120 130 140 Ambient Temperature (ƒC) C004 Figure 22. Maximum Output Current vs Ambient Temperature VIN = 12 V, VOUT = 5 V, ƒSW = 400 kHz, RθJA = 30°C/W Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 25 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com The resources below can be used as a guide to optimal thermal PCB design and estimating RθJA for a given application environment: • Thermal Design by Insight not Hindsight • A Guide to Board Layout for Best Thermal Resistance for Exposed Pad Packages • Semiconductor and IC Package Thermal Metrics • Thermal Design Made Simple with LM43603 and LM43602 • SLMA002 PowerPADTM Thermally Enhanced Package • PowerPADTM Made Easy • SBVA025 Using New Thermal Metrics 26 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 9.2.3 Application Curves 100 100 95 95 90 90 85 85 80 80 Efficiency (%) Efficiency (%) Unless otherwise specified the following conditions apply: VIN = 12 V, TA = 25°C. The circuit is shown in Figure 47, with the appropriate BOM from Table 3 or Table 4. 75 70 65 8V 60 75 70 65 55 55 12V 50 24V 50 24V 45 45 36V 40 0.001 0.01 0.1 1 VOUT = 5 V 40 0.001 10 Output Current (A) 0.01 400 kHz 0.1 1 10 Output Current (A) DDA Package VOUT = 3.3 V C017 400 kHz DDA Package Figure 24. Efficiency 100 100 95 95 90 90 85 85 80 80 Efficiency (%) Efficiency (%) 36V C016 Figure 23. Efficiency 75 70 65 8V 60 75 70 65 5V 60 55 12V 55 12V 50 24V 50 24V 45 45 36V 40 0.001 0.01 0.1 1 VOUT = 5 V 40 0.001 10 Output Current (A) 36V 0.01 1.4 MHz 0.1 1 10 Output Current (A) C013 DDA Package VOUT = 3.3 V Figure 25. Efficiency C014 1.4 MHz DDA Package Figure 26. Efficiency 100 100 95 95 90 90 85 85 80 80 Efficiency (%) Efficiency (%) 5V 60 12V 75 70 65 8V 60 75 70 65 5V 60 55 12V 55 12V 50 24V 50 24V 45 45 36V 40 0.001 VOUT = 5 V 0.01 0.1 Output Current (A) 2.1 MHz 1 10 40 0.001 0.1 1 10 Output Current (A) C009 DDA Package 36V 0.01 VOUT = 3.3 V Figure 27. Efficiency 2.1 MHz C010 DDA Package Figure 28. Efficiency Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 27 LMR33620 www.ti.com 100 100 95 95 90 90 85 85 Efficiency (%) Efficiency (%) SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 80 75 70 8V 65 0.01 0.1 1 VOUT = 5 V 50 0.001 10 Output Current (A) 400 kHz RNX Package 90 85 85 Efficiency (%) Efficiency (%) 95 90 80 75 70 8V 65 55 1 75 70 1.4 MHz RNX Package 36V 0.01 VOUT = 3.3 V 100 95 95 90 90 85 85 Efficiency (%) Efficiency (%) 24V 0.1 1 10 C021 1.4 MHz RNX Package Figure 32. Efficiency 80 75 70 8V 65 70 5V 12V 24V 55 36V 1 75 60 24V 55 80 65 12V 60 10 50 0.001 RNX Package 36V 0.01 0.1 Output Current (A) C020 VOUT = 3.3 V Figure 33. Efficiency 28 12V Output Current (A) 100 2.1 MHz 5V C022 Figure 31. Efficiency VOUT = 5 V RNX Package 80 50 0.001 10 Output Current (A) 0.1 10 C019 400 kHz 55 36V Output Current (A) 1 60 24V 0.01 0.1 65 12V 60 50 0.001 0.01 Figure 30. Efficiency 100 VOUT = 5 V 36V VOUT = 3.3 V 95 0.1 24V Output Current (A) 100 0.01 12V C018 Figure 29. Efficiency 50 0.001 5V 55 36V 50 0.001 70 60 24V 55 75 65 12V 60 80 2.1 MHz 1 10 C023 RNX Package Figure 34. Efficiency Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 34 5.055 8V 5.045 12V 5.04 24V 5.035 36V 32 Input Supply Current (µA) Output Voltage (V) 5.05 5.03 5.025 5.02 5.015 5.01 30 28 26 24 22 5.005 5V 5 20 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Output Current (A) 5 2 10 15 20 25 30 35 40 Input Voltage (V) C011 VOUT = 5 V VOUT = 5 V C016 RFBT = 1 MΩ IOUT = 0 A Figure 35. Line and Load Regulation Figure 36. Input Supply Current 0.25 10000000 1000000 Switching Frequency (Hz) 0.15 X PWM 0.1 PFM X Output Current (A) 0.2 0.05 100000 10000 1000 8V 100 12V 10 24V 36V 5V 0 0 5 10 15 20 25 30 35 Input Voltage (V) VOUT = 5 V 40 1 0.00001 ƒSW = 400 kHz VOUT = 5 V Figure 37. Mode Change Thresholds 0.0001 0.001 0.01 0.1 1 10 Output Current (A) C005 C014 ƒSW = 400 kHz Figure 38. Switching Frequency vs Output Current VOUT, 300mV/Div VOUT, 300mV/Div Output Current, 0.5A/Div Output Current, 0.5A/Div 100µs/Div VIN = 12 V tf = tr = 2 µs VOUT = 5 V IOUT = 0 A to 2 A 100µs/Div VIN = 12 V tf = tr = 2 µs VOUT = 5 V IOUT = 1 A to 2 A Figure 40. Load Transient Figure 39. Load Transient Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 29 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com 34 3.345 5V 32 12V 3.335 24V 3.33 36V Input Supply Current (µA) Output Voltage (V) 3.34 3.325 3.32 3.315 30 28 26 24 3.31 22 3.305 20 3.3V 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Output Current (A) 5 2 15 20 VOUT = 3.3 V Figure 41. Line and Load Regulation 0.30 1000000 Switching Frequency (Hz) 10000000 0.25 0.20 X PWM 0.10 PFM X 0.05 30 35 C015 IOUT = 0 A RFBT = 1 MΩ 100000 10000 1000 5V 100 12V 10 24V 36V 3.3V 0.00 0 5 10 15 20 25 30 35 Input Voltage (V) VOUT = 3.3V 40 1 0.00001 ƒSW = 400 kHz 0.0001 0.001 0.01 0.1 1 10 Output Current (A) C006 VOUT = 3.3 V Figure 43. Mode Change Thresholds C015 ƒSW = 400 kHz Figure 44. Switching Frequency vs Output Current VOUT, 300mV/Div VOUT, 300mV/Div Output Current, 0.5A/Div Output Current, 0.5A/Div 0 100µs/Div VIN = 12 V tf = tr = 2 µs VOUT = 3.3 V IOUT = 0 A to 2 A 100µs/Div VIN = 12 V tf = tr = 2 µs VOUT = 3.3 V IOUT = 1 A to 2 A Figure 46. Load Transient Figure 45. Load Transient 30 40 Figure 42. Input Supply Current 0.35 0.15 25 Input Voltage (V) VOUT = 3.3 V Output Current (A) 10 C012 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 L VIN VIN VOUT SW U1 CBOOT CIN CHF COUT BOOT EN 0.1 µF RFBT PG 100 NŸ PG 100 NŸ VCC CVCC 1 µF FB PGND AGND RFBB Figure 47. Circuit for Application Curves Table 3. BOM for Typical Application Curves DDA Package (1) (1) VOUT FREQUENCY RFBB COUT CIN + CHF L U1 3.3 V 400 kHz 43.3 kΩ 4 × 22 µF 1 × 10 µF + 1 × 220 nF 6.8 µH, 14 mΩ LMR33620ADDA 3.3 V 1400 KHz 43.3 kΩ 4 × 22 µF 1 × 10 µF + 1 × 220 nF 2.2 µH, 11.4 mΩ LMR33620BDDA 3.3 V 2100 kHz 43.3 kΩ 4 × 22 µF 1 × 10 µF + 1 × 220 nF 1.2 µH, 16 mΩ LMR33620CDDA 5V 400 kHz 24.9 kΩ 4 × 22 µF 1 × 10 µF + 1 × 220 nF 8.2 µH, 14 mΩ LMR33620ADDA 5V 1400 KHz 24.9 kΩ 4 × 22 µF 1 × 10 µF + 1 × 220 nF 2.2 µH, 11.4 mΩ LMR33620BDDA 5V 2100 kHz 24.9 kΩ 4 × 22 µF 1 × 10 µF + 1 × 220 nF 1.5 µH, 8.2 mΩ LMR33620CDDA The values in this table were selected to enhance certain performance criteria and may not represent typical values. Table 4. BOM for Typical Application Curves RNX Package (1) (1) VOUT FREQUENCY RFBB COUT CIN + CHF L U1 3.3 V 400 kHz 43.3 kΩ 4 × 22 µF 2 × 4.7 µF + 2 × 100 nF 4.7 µH, 28 mΩ LMR33620ARNX 3.3 V 1400 KHz 43.3 kΩ 4 × 22 µF 2 × 4.7 µF + 2 × 100 nF 2.2 µH, 11.4 mΩ LMR33620BRNX 3.3 V 2100 kHz 43.3 kΩ 4 × 22 µF 2 × 4.7 µF + 2 × 100 nF 2.2 µH, 11.4 mΩ LMR33620CRNX 5V 400 kHz 24.9 kΩ 4 × 22 µF 2 × 4.7 µF + 2 × 100 nF 6.8 µH, 14 mΩ LMR33620ARNX 5V 1400 KHz 24.9 kΩ 4 × 22 µF 2 × 4.7 µF + 2 × 100 nF 2.2 µH, 11.4 mΩ LMR33620BRNX 5V 2100 kHz 24.9 kΩ 4 × 22 µF 2 × 4.7 µF + 2 × 100 nF 2.2 µH, 11.4 mΩ LMR33620CRNX The values in this table were selected to enhance certain performance criteria and may not represent typical values. 9.3 Do's and Don'ts • • • • • • • Don't: Exceed the Absolute Maximum Ratings Don't: Exceed the ESD Ratings Don't: Exceed the Recommended Operating Conditions Don't: Allow the EN input to float. Don't: Allow the output voltage to exceed the input voltage, nor go below ground. Don't: Use the value of RθJA given in the Thermal Information table to design your application. Do: Follow all the guidelines and/or suggestions found in this data sheet before committing the design to production. TI application engineers are ready to help critique your design and PCB layout to help make your project a success (see Community Resources). Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 31 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com 10 Power Supply Recommendations The characteristics of the input supply must be compatible with the Absolute Maximum Ratings and Recommended Operating Conditions found in this data sheet. In addition, the input supply must be capable of delivering the required input current to the loaded regulator. The average input current can be estimated with Equation 12, where η is the efficiency. VOUT ˜ IOUT IIN VIN ˜ K (12) If the regulator is connected to the input supply through long wires or PCB traces, special care is required to achieve good performance. The parasitic inductance and resistance of the input cables can have an adverse effect on the operation of the regulator. The parasitic inductance, in combination with the low-ESR, ceramic input capacitors, can form an under damped resonant circuit, resulting in overvoltage transients at the input to the regulator. The parasitic resistance can cause the voltage at the VIN pin to dip whenever a load transient is applied to the output. If the application is operating close to the minimum input voltage, this dip may cause the regulator to momentarily shutdown and/or reset. The best way to solve these kind of issues is to reduce the distance from the input supply to the regulator and/or use an aluminum or tantalum input capacitor in parallel with the ceramics. The moderate ESR of these types of capacitors help to damp the input resonant circuit and reduce any overshoots. A value in the range of 20 µF to 100 µF is usually sufficient to provide input damping and help to hold the input voltage steady during large load transients. Sometimes, for other system considerations, an input filter is used in front of the regulator. This can lead to instability, as well as some of the effects mentioned above, unless it is designed carefully. The user guide AN2162 Simple Success With Conducted EMI From DCDC Converters provides helpful suggestions when designing an input filter for any switching regulator. In some cases a transient voltage suppressor (TVS) is used on the input of regulators. One class of this device has a snap-back characteristic (thyristor type). The use of a device with this type of characteristic is not recommended. When the TVS fires, the clamping voltage falls to a very low value. If this voltage is less than the output voltage of the regulator, the output capacitors discharge through the device back to the input. This uncontrolled current flow may damage the device. The input voltage should not be allowed to fall below the output voltage. In this scenario, such as a shorted input test, the output capacitors will discharge through the internal parasitic diode found between the VIN and SW pins of the device. During this condition, the current can become uncontrolled, possibly causing damage to the device. If this scenario is considered likely, then a Schottky diode between the input supply and the output should be used. 32 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 11 Layout 11.1 Layout Guidelines The PCB layout of any DC/DC converter is critical to the optimal performance of the design. Bad PCB layout can disrupt the operation of an otherwise good schematic design. Even if the converter regulates correctly, bad PCB layout can mean the difference between a robust design and one that cannot be mass produced. Furthermore, the EMI performance of the regulator is dependent on the PCB layout, to a great extent. In a buck converter the most critical PCB feature is the loop formed by the input capacitor(s) and power ground, as shown in Figure 48. This loop carries large transient currents that can cause large transient voltages when reacting with the trace inductance. These unwanted transient voltages will disrupt the proper operation of the converter. Because of this, the traces in this loop should be wide and short, and the loop area as small as possible to reduce the parasitic inductance. Figure 49 and Figure 50 show recommended layouts for the critical components of the LMR33620 . 1. Place the input capacitor(s) as close as possible to the VIN and GND terminals. VIN and GND pins are adjacent, simplifying the input capacitor placement. 2. Place bypass capacitor for VCC close to the VCC pin. This capacitor must be placed close to the device and routed with short, wide traces to the VCC and GND pins. 3. Use wide traces for the CBOOT capacitor. Place CBOOT close to the device with short/wide traces to the BOOT and SW pins. For the VQFN package, it is important to route the SW connection under the device to the NC pin, and use this path to connect the BOOT capacitor to SW. 4. Place the feedback divider as close as possible to the FB pin of the device. Place RFBB, RFBT, and CFF, if used, physically close to the device. The connections to FB and GND must be short and close to those pins on the device. The connection to VOUT can be somewhat longer. However, this latter trace must not be routed near any noise source (such as the SW node) that can capacitively couple into the feedback path of the regulator. 5. Use at least one ground plane in one of the middle layers. This plane acts as a noise shield and also act as a heat dissipation path. 6. Connect the thermal pad to the ground plane. The SOIC package has a thermal pad (PAD) connection that must be soldered down to the PCB ground plane. This pad acts as a heat-sink connection and an electrical ground connection for the regulator. The integrity of this solder connection has a direct bearing on the total effective RθJA of the application. 7. Provide wide paths for VIN, VOUT, and GND. Making these paths as wide and direct as possible reduces any voltage drops on the input or output paths of the converter and maximizes efficiency. 8. Provide enough PCB area for proper heat sinking. As stated in the Maximum Ambient Temperature section, enough copper area must be used to ensure a low RθJA, commensurate with the maximum load current and ambient temperature. Make the top and bottom PCB layers with two-ounce copper; and no less than one ounce. With the SOIC package, use an array of heat-sinking vias to connect the thermal pad (PAD) to the ground plane on the bottom PCB layer. If the PCB design uses multiple copper layers (recommended), thermal vias can also be connected to the inner layer heat-spreading ground planes. 9. Keep switch area small. Keep the copper area connecting the SW pin to the inductor as short and wide as possible. At the same time the total area of this node should be minimized to help reduce radiated EMI. See the following PCB layout resources for additional important guidelines: • Layout Guidelines for Switching Power Supplies • Simple Switcher PCB Layout Guidelines • Construction Your Power Supply- Layout Considerations • Low Radiated EMI Layout Made Simple with LM4360x and LM4600x Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 33 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com Layout Guidelines (continued) VIN CIN SW GND Figure 48. Current Loops with Fast Edges 11.1.1 Ground and Thermal Considerations As mentioned above, TI recommends using one of the middle layers as a solid ground plane. A ground plane provides shielding for sensitive circuits and traces. It also provides a quiet reference potential for the control circuitry. The AGND and PGND pins should be connected to the ground planes using vias next to the bypass capacitors. PGND pins are connected directly to the source of the low side MOSFET switch, and also connected directly to the grounds of the input and output capacitors. The PGND net contains noise at the switching frequency and may bounce due to load variations. The PGND trace, as well as the VIN and SW traces, must be constrained to one side of the ground planes. The other side of the ground plane contains much less noise and must be used for sensitive routes. TI recommends providing adequate device heat sinking by utilizing the thermal pad (PAD) of the device as the primary thermal path. Use a minimum 4 × 3 array of 10 mil thermal vias to connect the PAD to the system ground plane heat sink. The vias must be evenly distributed under the PAD. Use as much copper as possible, for system ground plane, on the top and bottom layers for the best heat dissipation. Use a four-layer board with the copper thickness for the four layers, starting from the top as: 2 oz / 1 oz / 1 oz / 2 oz. A four-layer board with enough copper thickness, and proper layout, provides low current conduction impedance, proper shielding and lower thermal resistance. 34 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 11.2 Layout Example GND HEATSINK INDUCTOR VOUT COUT COUT CBOOT COUT CHF GND CIN VIN EN CVCC PGOOD RFBT RFBB GND GND HEATSINK Top Trace Bottom Trace VIA Ground Plane VIA Bottom Figure 49. Example Layout for HSOIC (DDA) Package Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 35 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com Layout Example (continued) VOUT VOUT INDUCTOR COUT COUT COUT COUT GND GND CIN CIN CHF 12 11 2 10 3 9 4 8 5 6 VIN EN PGOOD 7 RFBT CBOOT 1 VIN CHF CVCC RFBB GND HEATSINK GND HEATSINK INNER GND PLANE Top Trace/Plane Inner GND Plane VIN Strap on Inner Layer Top VIA to Signal Layer Inner GND Plane VIA to GND Planes VIN Strap and GND Plane Signal traces and GND Plane VIA to VIN Strap Trace on Signal Layer Figure 50. Example Layout for VQFN Package 36 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 12 Device and Documentation Support 12.1 Device Support 12.1.1 Development Support 12.1.1.1 Custom Design With WEBENCH® Tools Click here to create a custom design using the LM33620 device with the WEBENCH® Power Designer. 1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements. 2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial. 3. Compare the generated design with other possible solutions from Texas Instruments. The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time pricing and component availability. In most cases, these actions are available: • Run electrical simulations to see important waveforms and circuit performance • Run thermal simulations to understand board thermal performance • Export customized schematic and layout into popular CAD formats • Print PDF reports for the design, and share the design with colleagues Get more information about WEBENCH tools at www.ti.com/WEBENCH. 12.2 Documentation Support 12.2.1 Related Documentation For related documentation see the following: • Thermal Design by Insight not Hindsight • A Guide to Board Layout for Best Thermal Resistance for Exposed Pad Packages • Semiconductor and IC Package Thermal Metrics • Thermal Design Made Simple with LM43603 and LM43602 • SLMA002 PowerPADTM Thermally Enhanced Package • PowerPADTM Made Easy • SBVA025 Using New Thermal Metrics • Layout Guidelines for Switching Power Supplies • Simple Switcher PCB Layout Guidelines • Construction Your Power Supply- Layout Considerations • Low Radiated EMI Layout Made Simple with LM4360x and LM4600x 12.3 Receiving Notification of Documentation Updates To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document. 12.4 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 37 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com 12.5 Trademarks PowerPAD, E2E are trademarks of Texas Instruments. SIMPLE SWITCHER, WEBENCH are registered trademarks of Texas Instruments. All other trademarks are the property of their respective owners. 12.6 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. 12.7 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 13 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. 38 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 PACKAGE OUTLINE DDA0008J PowerPADTM SOIC - 1.7 mm max height SCALE 2.400 PLASTIC SMALL OUTLINE C 6.2 TYP 5.8 SEATING PLANE PIN 1 ID AREA A 0.1 C 6X 1.27 8 1 2X 3.81 5.0 4.8 NOTE 3 4 5 8X 4.0 3.8 NOTE 4 B 0.51 0.31 0.1 C A 1.7 MAX B 0.25 TYP 0.10 SEE DETAIL A 5 4 EXPOSED THERMAL PAD 0.25 GAGE PLANE 3.1 2.5 8 1 0 -8 0.15 0.00 1.27 0.40 DETAIL A 2.6 2.0 TYPICAL 4221637/B 03/2016 PowerPAD is a trademark of Texas Instruments. NOTES: 1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing per ASME Y14.5M. 2. This drawing is subject to change without notice. 3. This dimension does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not exceed 0.15 mm per side. 4. This dimension does not include interlead flash. Interlead flash shall not exceed 0.25 mm per side. 5. Reference JEDEC registration MS-012, variation BA. www.ti.com Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 39 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com EXAMPLE BOARD LAYOUT DDA0008J PowerPAD TM SOIC - 1.7 mm max height PLASTIC SMALL OUTLINE (2.95) NOTE 9 SOLDER MASK DEFINED PAD (2.6) SOLDER MASK OPENING SEE DETAILS 8X (1.55) 1 8 8X (0.6) SYMM (1.3) TYP (3.1) SOLDER MASK OPENING (4.9) NOTE 9 6X (1.27) 5 4 ( 0.2) TYP VIA METAL COVERED BY SOLDER MASK SYMM (1.3) TYP (5.4) LAND PATTERN EXAMPLE SCALE:10X 0.07 MIN ALL AROUND 0.07 MAX ALL AROUND SOLDER MASK OPENING METAL METAL UNDER SOLDER MASK SOLDER MASK OPENING SOLDER MASK DEFINED NON SOLDER MASK DEFINED SOLDER MASK DETAILS 4221637/B 03/2016 NOTES: (continued) 6. Publication IPC-7351 may have alternate designs. 7. Solder mask tolerances between and around signal pads can vary based on board fabrication site. 8. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature numbers SLMA002 (www.ti.com/lit/slma002) and SLMA004 (www.ti.com/lit/slma004). 9. Size of metal pad may vary due to creepage requirement. www.ti.com 40 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 EXAMPLE STENCIL DESIGN DDA0008J PowerPAD TM SOIC - 1.7 mm max height PLASTIC SMALL OUTLINE (2.6) BASED ON 0.125 THICK STENCIL 8X (1.55) 1 8 8X (0.6) (3.1) BASED ON 0.127 THICK STENCIL SYMM 6X (1.27) 5 4 METAL COVERED BY SOLDER MASK SYMM (5.4) SEE TABLE FOR DIFFERENT OPENINGS FOR OTHER STENCIL THICKNESSES SOLDER PASTE EXAMPLE EXPOSED PAD 100% PRINTED SOLDER COVERAGE BY AREA SCALE:10X STENCIL THICKNESS SOLDER STENCIL OPENING 0.1 0.125 0.150 0.175 2.91 X 3.47 2.6 X 3.1 (SHOWN) 2.37 X 2.83 2.20 X 2.62 4221637/B 03/2016 NOTES: (continued) 10. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate design recommendations. 11. Board assembly site may have different recommendations for stencil design. www.ti.com Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 41 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com PACKAGE OUTLINE RNX0012B VQFN-HR - 1 mm max height SCALE 4.500 PLASTIC QUAD FLATPACK - NO LEAD 2.1 1.9 B A PIN 1 INDEX AREA 3.1 2.9 0.1 MIN (0.05) SECTION A-A A-A 40.000 TYPICAL 1 MAX C SEATING PLANE 0.05 0.00 0.08 C 1 SYMM (0.2) TYP 7 5 2X 0.675 2X 1.125 4X 0.5 8 4 PKG 1.725 1.525 2X 0.65 A 1 11 A 12 PIN 1 ID 11X 0.3 0.2 11X 0.5 0.3 0.3 0.2 0.1 0.05 C B A C 4223969/B 03/2018 NOTES: 1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing per ASME Y14.5M. 2. This drawing is subject to change without notice. 3. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance. www.ti.com 42 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 LMR33620 www.ti.com SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 EXAMPLE BOARD LAYOUT RNX0012B VQFN-HR - 1 mm max height PLASTIC QUAD FLATPACK - NO LEAD (0.25) 12 11X (0.6) 1 11 2X (0.65) 11X (0.25) (1.825) 2X (1.125) (0.788) PKG 2X (0.675) 4X (0.5) 8 4 (1.4) (R0.05) TYP 5 SYMM 7 (1.8) LAND PATTERN EXAMPLE EXPOSED METAL SHOWN SCALE:25X 0.07 MAX ALL AROUND 0.07 MIN ALL AROUND SOLDER MASK OPENING METAL EDGE EXPOSED METAL SOLDER MASK OPENING EXPOSED METAL NON SOLDER MASK DEFINED (PREFERRED) METAL SOLDER MASK DEFINED PADS 1, 2, 10-12 SOLDER MASK DETAILS 4223969/B 03/2018 NOTES: (continued) 4. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature number SLUA271 (www.ti.com/lit/slua271). www.ti.com Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 43 LMR33620 SNVSAW1A – FEBRUARY 2018 – REVISED APRIL 2018 www.ti.com EXAMPLE STENCIL DESIGN RNX0012B VQFN-HR - 1 mm max height PLASTIC QUAD FLATPACK - NO LEAD 2X (0.25) 2X (0.812) 12 11X (0.6) 11X (0.25) 1 11 2X (0.65) EXPOSED METAL (1.294) 2X (1.125) PKG (0.282) 2X (0.675) 4X (0.5) 8 4 (1.4) (R0.05) TYP 5 SYMM 7 (1.8) SOLDER PASTE EXAMPLE BASED ON 0.125 mm THICK STENCIL FOR PAD 12 87.7% PRINTED SOLDER COVERAGE BY AREA SCALE:25X 4223969/B 03/2018 NOTES: (continued) 5. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate design recommendations. www.ti.com 44 Submit Documentation Feedback Copyright © 2018, Texas Instruments Incorporated Product Folder Links: LMR33620 PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2018 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LMR33620ADDA ACTIVE SO PowerPAD DDA 8 75 Green (RoHS & no Sb/Br) CU NIPDAUAG Level-2-260C-1 YEAR -40 to 125 33620A LMR33620ADDAR ACTIVE SO PowerPAD DDA 8 2500 Green (RoHS & no Sb/Br) CU NIPDAUAG Level-2-260C-1 YEAR -40 to 125 33620A LMR33620ARNXR ACTIVE VQFN-HR RNX 12 3000 Green (RoHS & no Sb/Br) CU SN Level-2-260C-1 YEAR -40 to 125 33620A LMR33620ARNXT ACTIVE VQFN-HR RNX 12 250 Green (RoHS & no Sb/Br) CU SN Level-2-260C-1 YEAR -40 to 125 33620A LMR33620BDDA ACTIVE SO PowerPAD DDA 8 75 Green (RoHS & no Sb/Br) CU NIPDAUAG Level-2-260C-1 YEAR -40 to 125 33620B LMR33620BDDAR ACTIVE SO PowerPAD DDA 8 2500 Green (RoHS & no Sb/Br) CU NIPDAUAG Level-2-260C-1 YEAR -40 to 125 33620B LMR33620BRNXR ACTIVE VQFN-HR RNX 12 3000 Green (RoHS & no Sb/Br) CU SN Level-2-260C-1 YEAR -40 to 125 33620B LMR33620BRNXT ACTIVE VQFN-HR RNX 12 250 Green (RoHS & no Sb/Br) CU SN Level-2-260C-1 YEAR -40 to 125 33620B LMR33620CDDA ACTIVE SO PowerPAD DDA 8 75 Green (RoHS & no Sb/Br) CU NIPDAUAG Level-2-260C-1 YEAR -40 to 125 33620C LMR33620CDDAR ACTIVE SO PowerPAD DDA 8 2500 Green (RoHS & no Sb/Br) CU NIPDAUAG Level-2-260C-1 YEAR -40 to 125 33620C LMR33620CRNXR ACTIVE VQFN-HR RNX 12 3000 Green (RoHS & no Sb/Br) CU SN Level-2-260C-1 YEAR -40 to 125 33620C LMR33620CRNXT ACTIVE VQFN-HR RNX 12 250 Green (RoHS & no Sb/Br) CU SN Level-2-260C-1 YEAR -40 to 125 33620C (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) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2018 Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (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. 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Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 27-Feb-2018 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LMR33620ADDAR SO Power PAD DDA 8 2500 330.0 12.8 6.4 5.2 2.1 8.0 12.0 Q1 LMR33620BDDAR SO Power PAD DDA 8 2500 330.0 12.8 6.4 5.2 2.1 8.0 12.0 Q1 LMR33620CDDAR SO Power PAD DDA 8 2500 330.0 12.8 6.4 5.2 2.1 8.0 12.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 27-Feb-2018 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LMR33620ADDAR SO PowerPAD DDA 8 2500 366.0 364.0 50.0 LMR33620BDDAR SO PowerPAD DDA 8 2500 366.0 364.0 50.0 LMR33620CDDAR SO PowerPAD DDA 8 2500 366.0 364.0 50.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated (TI) reserves 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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