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LM2734ZMKX

LM2734ZMKX

  • 厂商:

    BURR-BROWN(德州仪器)

  • 封装:

    SOT-23-6L

  • 描述:

    IC REG BUCK ADJ 1A TSOT23-6

  • 数据手册
  • 价格&库存
LM2734ZMKX 数据手册
Sample & Buy Product Folder Support & Community Tools & Software Technical Documents LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 LM2734Z/-Q1 Thin SOT 1-A Load Step-Down DC-DC Regulator 1 Features 3 Description • • The LM2734Z regulator is a monolithic, highfrequency, PWM step-down DC–DC converter assembled in a thick 6-pin SOT and a WSON nonpullback package. The device provides all the active functions to provide local DC–DC conversion with fast transient response and accurate regulation in the smallest possible PCB area. 1 • • • • • • • • • • • Qualified for Automotive Applications AEC-Q100 Qualified With the Following Results: – Device Temperature Grade 1: –40°C to 125°C Ambient Operating Temperature Range – Device HBM ESD Classification Level 2 – Device CDM ESD Classification Level C6 6-pin SOT Package, or 6-Pin WSON Package 3.0-V to 20-V Input Voltage Range 0.8-V to 18-V Output Voltage Range 1-A Output Current 3-MHz Switching Frequency 300-mΩ NMOS Switch 30-nA Shutdown Current 0.8-V, 2% Internal Voltage Reference Internal Soft-Start Current-Mode, PWM Operation Thermal Shutdown 2 Applications • • • • • DSL Modems Local Point of Load Regulation Battery-Powered Devices USB-Powered Devices Automotive With a minimum of external components and online design support through WEBENCH™, the LM2734Z is easy to use. The ability to drive 1-A loads with an internal 300-mΩ NMOS switch using state-of-the-art 0.5-µm BiCMOS technology results in the best power density available. The world class control circuitry allows for ON-times as low as 13 ns, thus supporting exceptionally high-frequency conversion over the entire 3-V to 20-V input operating range down to the minimum output voltage of 0.8 V. Switching frequency is internally set to 3 MHz, allowing the use of extremely small surface mount inductors and chip capacitors. Even though the operating frequency is very high, efficiencies up to 85% are easy to achieve. External shutdown is included, featuring an ultra-low standby current of 30 nA. The LM2734Z uses currentmode control and internal compensation to provide high-performance regulation over a wide range of operating conditions. Additional features include internal soft-start circuitry to reduce inrush current, pulse-by-pulse current limit, thermal shutdown, and output overvoltage protection. Device Information(1) PART NUMBER LM2734Z PACKAGE BODY SIZE (NOM) WSON (6) 3.00 mm × 3.00 mm SOT (6) 1.60 mm × 2.90 mm (1) For all available packages, see the orderable addendum at the end of the data sheet. Typical Application Circuit Efficiency vs Load Current D2 VIN BOOST VIN C3 C1 L1 SW VOUT LM2734 ON D1 EN C2 R1 OFF FB GND R2 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. LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 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 4 6.1 6.2 6.3 6.4 6.5 6.6 4 4 4 5 5 6 Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics........................................... Typical Characteristics .............................................. Detailed Description .............................................. 7 7.1 Overview ................................................................... 7 7.2 Functional Block Diagram ......................................... 7 7.3 Feature Description................................................... 7 7.4 Device Functional Modes........................................ 11 8 Application and Implementation ........................ 12 8.1 Application Information............................................ 12 8.2 Typical Applications ................................................ 12 9 Power Supply Recommendations...................... 26 10 Layout................................................................... 26 10.1 Layout Guidelines ................................................. 26 10.2 Layout Examples................................................... 27 11 Device and Documentation Support ................. 28 11.1 11.2 11.3 11.4 11.5 11.6 Device Support...................................................... Documentation Support ........................................ Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 28 28 28 28 28 28 12 Mechanical, Packaging, and Orderable Information ........................................................... 28 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision E (April 2013) to Revision F Page • Added ESD Ratings table, Feature Description section, Device Functional Modes section, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section................................................................ 1 • Removed soldering information ............................................................................................................................................. 4 Changes from Revision D (April 2013) to Revision E • 2 Page Changed layout of National Data Sheet to TI format ........................................................................................................... 25 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 5 Pin Configuration and Functions DDC Package 6-Pin SOT Top View BOOST 1 6 SW GND 2 5 VIN FB 3 4 EN NGG Package 6-Pin WSON Top View FB 1 GND 2 BOOST 3 DAP 6 EN 5 VIN 4 SW Pin Functions PIN TYPE (1) DESCRIPTION NAME SOT WSON BOOST 1 3 I Boost voltage that drives the internal NMOS control switch. A bootstrap capacitor is connected between the BOOST and SW pins. DAP — — P The die attach pad is internally connected to GND. EN 4 6 I Enable control input. Logic high enables operation. Do not allow this pin to float or be greater than VIN + 0.3 V. FB 3 1 I Feedback pin. Connect FB to the external resistor divider to set output voltage. GND 2 2 P Signal and Power ground pin. Place the bottom resistor of the feedback network as close as possible to this pin for accurate regulation. SW 6 4 O Output switch. Connects to the inductor, catch diode, and bootstrap capacitor. VIN 5 5 P Input supply voltage. Connect a bypass capacitor to this pin. (1) I –Input, O – Output, P – Power Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 3 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com 6 Specifications 6.1 Absolute Maximum Ratings See (1) (2) VIN MIN MAX UNIT Input voltage –0.5 24 V SW voltage –0.5 24 V Boost voltage –0.5 30 V Boost to SW voltage –0.5 6 V FB voltage –0.5 3 V EN voltage –0.5 VIN + 0.3 V 150 °C 150 °C TJ Junction temperature Tstg Storage temperature (1) (2) –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. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. 6.2 ESD Ratings VALUE V(ESD) (1) (2) Electrostatic discharge Human-body model (HBM), per AEC Q100-002 (1) (2) ±2000 Charged-device model (CDM), per AEC Q100-002 ±1000 UNIT V AEC Q100-002 indicates that HBM stressing shall be in accordance with the ANSI/ESDA/JEDEC JS-001 specification. Human-body model, 1.5 kΩ in series with 100 pF. 6.3 Recommended Operating Conditions VIN TJ 4 MIN MAX 3 20 V SW voltage –0.5 20 V Boost voltage V Input voltage UNIT –0.5 25 Boost to SW voltage 1.6 5.5 V Junction temperature –40 125 °C Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 6.4 Thermal Information LM2734Z THERMAL METRIC (1) DDC (SOT) NGG (WSON) 6 PINS 6 PINS UNIT RθJA Junction-to-ambient thermal resistance (2) 180.3 56.2 °C/W RθJC(top) Junction-to-case (top) thermal resistance 51.6 52.6 °C/W RθJB Junction-to-board thermal resistance 27.7 30.7 °C/W ψJT Junction-to-top characterization parameter 1.2 0.9 °C/W ψJB Junction-to-board characterization parameter 27.3 30.8 °C/W RθJC(bot) Junction-to-case (bottom) thermal resistance — 10.7 °C/W (1) (2) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report (SPRA953). Thermal shutdown occurs if the junction temperature exceeds 165°C. The maximum power dissipation is a function of TJ(MAX), RθJA and TA . The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) – TA)/RθJA . All numbers apply for packages soldered directly onto a 3-in × 3-in printed-circuit-board with 2-oz. copper on 4 layers in still air. For a 2-layer board using 1-oz. copper in still air, RθJA = 204°C/W. 6.5 Electrical Characteristics All typical specifications are for TJ = 25°C, and all maximum and minimum limits apply over the full operating temperature range (TJ = –40°C to 125°C). VIN = 5 V, VBOOST – VSW = 5 V (unless otherwise noted). Data sheet minimum and maximum specification limits are specified by design, test, or statistical analysis. PARAMETER TEST CONDITIONS VFB Feedback voltage ΔVFB/ΔVIN Feedback voltage line regulation VIN = 3 V to 20 V IFB Feedback input bias current Sink and source Undervoltage lockout VIN Rising Undervoltage lockout VIN Falling UVLO UVLO hysteresis MIN (1) TYP (2) MAX (1) 0.784 0.8 0.816 0.01 V %/V 10 250 2.74 2.90 nA 2 2.3 0.30 0.44 0.62 3.6 MHz FSW Switching frequency 2.2 3.0 DMAX Maximum duty cycle 78% 85% DMIN Minimum duty Cycle RDS(ON) Switch ON resistance ICL UNIT V 8% VBOOST - VSW = 3 V (SOT Package) 300 600 mΩ VBOOST - VSW = 3 V (WSON Package) 340 650 mΩ Switch current limit VBOOST - VSW = 3 V 1.7 2.5 A Quiescent current Switching 1.5 2.5 mA Quiescent current (shutdown) VEN = 0 V 30 Boost pin current (Switching) Shutdown threshold voltage VEN Falling Enable threshold voltage VEN Rising IEN Enable pin current Sink/source ISW Switch leakage IQ IBOOST VEN_TH (1) (2) 1.2 4.25 nA 6 0.4 1.8 mA V 10 nA 40 nA Specified to Texas Instruments' Average Outgoing Quality Level (AOQL). Typicals represent the most likely parametric norm. Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 5 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com 6.6 Typical Characteristics at VIN = 5 V, VBOOST - VSW = 5 V, L1 = 2.2 µH and TA = 25°C (unless otherwise noted) VOUT = 5 V VOUT = 3.3 V Figure 1. Efficiency vs Load Current Figure 2. Efficiency vs Load Current VOUT = 1.5 V Figure 3. Efficiency vs Load Current VOUT = 1.5 V IOUT = 500 mA Figure 4. Oscillator Frequency vs Temperature VOUT = 3.3 V Figure 5. Line Regulation 6 Submit Documentation Feedback IOUT = 500 mA Figure 6. Line Regulation Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 7 Detailed Description 7.1 Overview The LM2734Z is a constant frequency buck regulator that can deliver load current of 1 A. Device is optimized for high-efficiency operation and includes a number of features that make it suitable for demanding applications. High switching frequency allows for use of small external components enabling small solution size and saving board space. Device is designed to operate from wide input voltage range up to 20 V, making it ideal for wide range of applications (such as automotive, industrial, communications, and so forth). LM2734Z can be controlled through shutdown pin, consuming only 30 nA in standby mode, making it very appealing for applications that demand very low standby power consumption. 7.2 Functional Block Diagram VIN VIN Current-Sense Amplifier OFF EN Internal Regulator and Enable Circuit + - BOOST VBOOST Under Voltage Lockout Oscillator CIN D2 Thermal Shutdown Current Limit Output Control Logic Reset Pulse + ISENSE + + Corrective Ramp 0.3: Switch Driver SW OVP Comparator - ON RSENSE Error Signal D 1 + PWM Comparator CBOOST VSW L IL VOUT COUT 0.88V + - R 1 FB Internal Compensation + Error Amplifier + - VREF 0.8V R 2 GND 7.3 Feature Description 7.3.1 Theory of Operation The LM2734Z is a constant frequency PWM buck regulator IC that delivers a 1-A load current. The regulator has a preset switching frequency of 3 MHz. This high frequency allows the LM2734Z to operate with small surface mount capacitors and inductors, resulting in a DC–DC converter that requires a minimum amount of board space. The LM2734Z is internally compensated, so it is simple to use, and requires few external components. The LM2734Z uses current-mode control to regulate the output voltage. The following operating description of the LM2734Z refers to the Functional Block Diagram and to the waveforms in Figure 7. The LM2734Z supplies a regulated output voltage by switching the internal NMOS control switch at constant frequency and variable duty cycle. A switching cycle begins at the falling edge of the reset pulse generated by the internal oscillator. When this pulse goes low, the output control logic turns on the internal NMOS control switch. During this ON-time, the SW pin voltage (VSW) swings up to approximately VIN, and the inductor current (IL) increases with a linear slope. IL is measured by the current-sense amplifier, which generates an output proportional to the switch current. The sense signal is summed with the corrective ramp of the Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 7 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com Feature Description (continued) regulator and compared to the output of the error amplifier, which is proportional to the difference between the feedback voltage and VREF. When the PWM comparator output goes high, the output switch turns off until the next switching cycle begins. During the switch OFF-time, inductor current discharges through Schottky diode D1, which forces the SW pin to swing below ground by the forward voltage (VD) of the catch diode. The regulator loop adjusts the duty cycle (D) to maintain a constant output voltage. VSW D = TON/TSW VIN SW Voltage TOFF TON 0 VD IL t TSW IPK Inductor Current t 0 Figure 7. LM2734Z Waveforms of SW Pin Voltage and Inductor Current 7.3.2 Boost Function Capacitor CBOOST and diode D2 in Figure 8 are used to generate a voltage VBOOST. VBOOST - VSW is the gate drive voltage to the internal NMOS control switch. To properly drive the internal NMOS switch during its ON-time, VBOOST needs to be at least 1.6 V greater than VSW. Although the LM2734Z operates with this minimum voltage, it may not have sufficient gate drive to supply large values of output current. Therefore, TI recommends that VBOOST be greater than 2.5 V above VSW for best efficiency. VBOOST – VSW must not exceed the maximum operating limit of 5.5 V. 5.5 V > VBOOST – VSW > 2.5 V for best performance. VBOOST D2 BOOST VIN VIN CIN LM2734 CBOOST L SW VOUT GND COUT D1 Figure 8. VOUT Charges CBOOST When the LM2734Z starts up, internal circuitry from the BOOST pin supplies a maximum of 20 mA to CBOOST. This current charges CBOOST to a voltage sufficient to turn the switch on. The BOOST pin continues to source current to CBOOST until the voltage at the feedback pin is greater than 0.76 V. 8 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 Feature Description (continued) There are various methods to derive VBOOST: 1. From the input voltage (VIN) 2. From the output voltage (VOUT) 3. From an external distributed voltage rail (VEXT) 4. From a shunt or series zener diode In Functional Block Diagram, capacitor CBOOST and diode D2 supply the gate-drive current for the NMOS switch. Capacitor CBOOST is charged through diode D2 by VIN. During a normal switching cycle, when the internal NMOS control switch is off (TOFF) (refer to Figure 7), VBOOST equals VIN minus the forward voltage of D2 (VFD2), during which the current in the inductor (L) forward biases the Schottky diode D1 (VFD1). Therefore the voltage stored across CBOOST is calculated using Equation 1. VBOOST –VSW = VIN – VFD2 + VFD1 (1) When the NMOS switch turns on (TON), the switch pin rises to: VSW = VIN – (RDSON x IL), (2) forcing VBOOST to rise thus reverse biasing D2. The voltage at VBOOST is then: VBOOST = 2 VIN – (RDSON x IL) – VFD2 + VFD1 (3) which is approximately: 2 VIN – 0.4 V (4) for many applications. Thus the gate-drive voltage of the NMOS switch is approximately: VIN –0.2 V (5) An alternate method for charging CBOOST is to connect D2 to the output as shown in Figure 8. The output voltage must be between 2.5 V and 5.5 V, so that proper gate voltage is applied to the internal switch. In this circuit, CBOOST provides a gate drive voltage that is slightly less than VOUT. In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged directly from these voltages. If VIN and VOUT are greater than 5.5 V, CBOOST can be charged from VIN or VOUT minus a Zener voltage by placing a Zener diode D3 in series with D2, as shown in Figure 9. When using a series Zener diode from the input, ensure that the regulation of the input supply does not create a voltage that falls outside the recommended VBOOST voltage. (VINMAX – VD3) < 5.5V (VINMIN – VD3) > 1.6V (6) (7) D2 D3 VIN VIN CIN BOOST VBOOST CBOOST LM2734 L VOUT SW GND D1 C OUT Figure 9. Zener Reduces Boost Voltage from VIN An alternative method is to place the Zener diode D3 in a shunt configuration as shown in Figure 10. A small 350-mW to 500-mW, 5.1-V Zener in a SOT or SOD package can be used for this purpose. A small ceramic capacitor such as a 6.3-V, 0.1-µF capacitor (C4) must be placed in parallel with the Zener diode. When the internal NMOS switch turns on, a pulse of current is drawn to charge the internal NMOS gate capacitance. The 0.1-µF parallel shunt capacitor ensures that the VBOOST voltage is maintained during this time. Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 9 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com Feature Description (continued) Resistor R3 must be chosen to provide enough RMS current to the Zener diode (D3) and to the BOOST pin. A recommended choice for the Zener current (IZENER) is 1 mA. The current IBOOST into the BOOST pin supplies the gate current of the NMOS control switch and varies typically according to Equation 8. IBOOST = (D + 0.5) × (VZENER – VD2) mA where • • • • • D is the duty cycle VZENER and VD2 are in volts IBOOST is in milliamps VZENER is the voltage applied to the anode of the boost diode (D2) VD2 is the average forward voltage across D2 (8) NOTE Equation 8 for IBOOST gives typical current. For the worst case IBOOST, increase the current by 25%. In that case, the worse-case boost current is: IBOOST-MAX = 1.25 × IBOOST (9) R3 is then given by Equation 10. R3 = (VIN - VZENER) / (1.25 × IBOOST + IZENER) (10) For example, let VIN = 10 V, VZENER = 5 V, VD2 = 0.7 V, IZENER = 1 mA, and duty cycle D = 50%. Then: IBOOST = (0.5 + 0.5) × (5 - 0.7) mA = 4.3 mA R3 = (10 V - 5 V) / (1.25 × 4.3 mA + 1 mA) = 787 Ω (11) (12) VZ C4 D2 D3 R3 VIN VIN BOOST CBOOST LM2734 C IN VBOOST L SW VOUT GND COUT D1 Figure 10. Boost Voltage Supplied from the Shunt Zener on VIN 7.3.3 Soft-Start This function forces VOUT to increase at a controlled rate during start-up. During soft-start, the reference voltage of the error amplifier ramps from 0 V to its nominal value of 0.8 V in approximately 200 µs. This forces the regulator output to ramp up in a more linear and controlled fashion, which helps reduce inrush current. 7.3.4 Output Overvoltage Protection The overvoltage comparator compares the FB pin voltage to a voltage that is 10% higher than the internal reference Vref. Once the FB pin voltage goes 10% above the internal reference, the internal NMOS control switch is turned off, which allows the output voltage to decrease toward regulation. 10 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 Feature Description (continued) 7.3.5 Undervoltage Lockout Undervoltage lockout (UVLO) prevents the LM2734Z from operating until the input voltage exceeds 2.74 V (typical). The UVLO threshold has approximately 440 mV of hysteresis, so the part operates until VIN drops below 2.3 V (typical). Hysteresis prevents the part from turning off during power up if VIN is non-monotonic. 7.3.6 Current Limit The LM2734Z uses cycle-by-cycle current limiting to protect the output switch. During each switching cycle, a current limit comparator detects if the output switch current exceeds 1.7 A (typical), and turns off the switch until the next switching cycle begins. 7.4 Device Functional Modes 7.4.1 Enable Pin and Shutdown Mode The LM2734Z has a shutdown mode that is controlled by the enable pin (EN). When a logic low voltage is applied to EN, the part is in shutdown mode and its quiescent current drops to typically 30 nA. Switch leakage adds another 40 nA from the input supply. The voltage at this pin must never exceed VIN + 0.3 V. 7.4.2 Thermal Shutdown Thermal shutdown limits total power dissipation by turning off the output switch when the IC junction temperature exceeds 165°C. After thermal shutdown occurs, the output switch doesn’t turn on until the junction temperature drops to approximately 150°C. Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 11 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com 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 This device operates with wide input voltage in the range of 3 V to 20 V and provides regulated output voltage in the range of 0.8 V to 18 V. This device is optimized for high-efficiency operation with a minimum number of external components, making it ideal for applications where board space is constrained. 8.2 Typical Applications 8.2.1 LM2734Z Design Example 1 D2 VIN BOOST VIN C3 C1 L1 R3 VOUT SW LM2734 ON D1 EN C2 R1 OFF FB GND R2 Figure 11. VBOOST Derived from VIN Operating Conditions: 5 V to 1.5 V / 1 A 8.2.1.1 Design Requirements Table 1 lists the operating conditions for the design example 1. Table 1. Design Parameters PARAMETER VALUE PARAMETER VALUE VIN 5.0 V POUT 2.5 W VOUT 2.5 V PDIODE 151 mW IOUT 1.0 A PIND 75 mW VD 0.35 V PSWF 53 mW Freq 3 MHz PSWR 53 mW IQ 1.5 mA PCOND 187 mW TRISE 8 ns PQ 7.5 mW TFALL 8 ns PBOOST 21 mW RDSON 330 mΩ PLOSS 548 mW INDDCR 75 mΩ D 56.8% 12 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 8.2.1.2 Detailed Design Procedure 8.2.1.2.1 Inductor Selection The Duty Cycle (D) can be approximated quickly using the ratio of output voltage (VO) to input voltage (VIN) as shown in Equation 13. VO D= VIN (13) The catch diode (D1) forward voltage drop and the voltage drop across the internal NMOS must be included to calculate a more accurate duty cycle. Calculate D with Equation 14. VO + VD D= VIN + VD - VSW (14) VSW can be approximated by Equation 15. VSW = IO x RDS(ON) (15) The diode forward drop (VD) can range from 0.3 V to 0.7 V depending on the quality of the diode. The lower VD is, the higher the operating efficiency of the converter. The inductor value determines the output ripple current. Lower inductor values decrease the size of the inductor, but increase the output ripple current. An increase in the inductor value decreases the output ripple current. The ratio of ripple current (ΔiL) to output current (IO) is optimized when it is set between 0.3 and 0.4 at 1 A. The ratio r is defined in Equation 16. r= 'iL lO (16) One must also ensure that the minimum current limit (1.2 A) is not exceeded, so the peak current in the inductor must be calculated. The peak current (ILPK) in the inductor is calculated by Equation 17. ILPK = IO + ΔIL/2 (17) If r = 0.5 at an output of 1 A, the peak current in the inductor is 1.25 A. The minimum specified current limit over all operating conditions is 1.2 A. One can either reduce r to 0.4 resulting in a 1.2-A peak current, or make the engineering judgement that 50 mA over is safe enough with a 1.7-A typical current limit and 6 sigma limits. When the designed maximum output current is reduced, the ratio r can be increased. At a current of 0.1 A, r can be made as high as 0.9. The ripple ratio can be increased at lighter loads because the net ripple is actually quite low, and if r remains constant the inductor value can be made quite large. An equation empirically developed for the maximum ripple ratio at any current below 2 A is: r = 0.387 × IOUT-0.3667 (18) NOTE Use this as a guideline. The LM2734Z operates at frequencies allowing the use of ceramic output capacitors without compromising transient response. Ceramic capacitors allow higher inductor ripple without significantly increasing output ripple. See the Output Capacitor section for more details on calculating output voltage ripple. Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 13 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com Now that the ripple current or ripple ratio is determined, the inductance is calculated by Equation 19. L= VO + VD IO x r x fS x (1-D) where • • fs is the switching frequency IO is the output current (19) When selecting an inductor, make sure that it is capable of supporting the peak output current without saturating. Inductor saturation results in a sudden reduction in inductance and prevent the regulator from operating correctly. Because of the speed of the internal current limit, the peak current of the inductor need only be specified for the required maximum output current. For example, if the designed maximum output current is 0.5 A and the peak current is 0.7 A, then the inductor must be specified with a saturation current limit of >0.7 A. There is no need to specify the saturation or peak current of the inductor at the 1.7-A typical switch current limit. The difference in inductor size is a factor of 5. Because of the operating frequency of the LM2734Z, ferrite based inductors are preferred to minimize core losses. This presents little restriction because the variety of ferrite based inductors is huge. Lastly, inductors with lower series resistance (DCR) provides better operating efficiency. For recommended inductors, see the design examples in Typical Applications. 8.2.1.2.2 Input Capacitor An input capacitor is necessary to ensure that VIN does not drop excessively during switching transients. The primary specifications of the input capacitor are capacitance, voltage, RMS current rating, and ESL (Equivalent Series Inductance). The recommended input capacitance is 10 µF, although 4.7 µF works well for input voltages below 6 V. The input voltage rating is specifically stated by the capacitor manufacturer. Make sure to check any recommended deratings and also verify if there is any significant change in capacitance at the operating input voltage and the operating temperature. The input capacitor maximum RMS input current rating (IRMS-IN) must be greater than: IRMS-IN = IO x r2 D x 1-D + 12 (20) As seen in Equation 20, the maximum RMS capacitor current occurs when D = 0.5. Always calculate the RMS at the point where the duty cycle, D, is closest to 0.5. The ESL of an input capacitor is usually determined by the effective cross sectional area of the current path. A large leaded capacitor has high ESL and a 0805 ceramic chip capacitor has very low ESL. At the operating frequencies of the LM2734Z, certain capacitors may have an ESL so large that the resulting impedance (2πfL) is higher than that required to provide stable operation. As a result, surface mount capacitors are strongly recommended. Sanyo POSCAP, Tantalum or Niobium, Panasonic SP or Cornell Dubilier ESR, and multilayer ceramic capacitors (MLCC) are all good choices for both input and output capacitors and have very low ESL. For MLCCs, TI recommends using X7R or X5R dielectrics. Consult capacitor manufacturer data sheet to see how rated capacitance varies over operating conditions. 8.2.1.2.3 Output Capacitor The output capacitor is selected based upon the desired output ripple and transient response. The initial current of a load transient is provided mainly by the output capacitor. The output ripple of the converter is shown in Equation 21. 'VO = 'iL x (RESR + 1 ) 8 x fS x CO (21) When using MLCCs, the ESR is typically so low that the capacitive ripple may dominate. When this occurs, the output ripple is approximately sinusoidal and 90° phase shifted from the switching action. Given the availability and quality of MLCCs and the expected output voltage of designs using the LM2734Z, there is really no need to review any other capacitor technologies. Another benefit of ceramic capacitors is their ability to bypass high frequency noise. A certain amount of switching edge noise couples through parasitic capacitances in the inductor 14 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 to the output. A ceramic capacitor bypasses this noise while a tantalum will not. Because the output capacitor is one of the two external components that control the stability of the regulator control loop, most applications will require a minimum at 10 µF of output capacitance. Capacitance can be increased significantly with little detriment to the regulator stability. Like the input capacitor, recommended multilayer ceramic capacitors are X7R or X5R. Again, verify actual capacitance at the desired operating voltage and temperature. Check the RMS current rating of the capacitor. The RMS current rating of the capacitor chosen must also meet Equation 22. r 12 IRMS-OUT = IO x (22) 8.2.1.2.4 Catch Diode The catch diode (D1) conducts during the switch OFF-time. A Schottky diode is recommended for its fast switching times and low forward voltage drop. The catch diode must be chosen so that its current rating is greater than Equation 23. ID1 = IO x (1-D) (23) The reverse breakdown rating of the diode must be at least the maximum input voltage plus appropriate margin. To improve efficiency choose a Schottky diode with a low forward voltage drop. 8.2.1.2.5 Boost Diode A standard diode such as the 1N4148 type is recommended. For VBOOST circuits derived from voltages less than 3.3 V, a small-signal Schottky diode is recommended for greater efficiency. A good choice is the BAT54 small signal diode. 8.2.1.2.6 Boost Capacitor A ceramic 0.01-µF capacitor with a voltage rating of at least 6.3 V is sufficient. The X7R and X5R MLCCs provide the best performance. 8.2.1.2.7 Output Voltage The output voltage is set using Equation 24 where R2 is connected between the FB pin and GND, and R1 is connected between VO and the FB pin. A good value for R2 is 10 kΩ. R1 = VO VREF - 1 x R2 (24) 8.2.1.2.8 Calculating Efficiency, and Junction Temperature The complete LM2734Z DC–DC converter efficiency can be calculated in the following manner: POUT K= PIN (25) Or POUT K= POUT + PLOSS (26) Calculations for determining the most significant power losses are shown below. Other losses totaling less than 2% are not discussed. Power loss (PLOSS) is the sum of two basic types of losses in the converter, switching and conduction. Conduction losses usually dominate at higher output loads, where as switching losses remain relatively fixed and dominate at lower output loads. The first step in determining the losses is to calculate the duty cycle (D). VOUT + VD D= VIN + VD - VSW (27) Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 15 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com VSW is the voltage drop across the internal NFET when it is on, and is equal to Equation 28. VSW = IOUT × RDSON (28) VD is the forward voltage drop across the Schottky diode. It can be obtained from the Electrical Characteristics section. If the voltage drop across the inductor (VDCR) is accounted for, use Equation 29 to calculate the duty cycle. VO + VD + VDCR D= VIN + VD - VSW (29) This usually gives only a minor duty cycle change, and has been omitted in the examples for simplicity. The conduction losses in the free-wheeling Schottky diode are calculated using Equation 30. PDIODE = VD × IOUT(1-D) (30) Often this is the single most significant power loss in the circuit. Take care choosing a Schottky diode that has a low forward voltage drop. Another significant external power loss is the conduction loss in the output inductor. The equation can be simplified to Equation 31. PIND = IOUT2 × RDCR (31) The LM2734Z conduction loss is mainly associated with the internal NFET, as shown in Equation 32. PCOND = IOUT2 ×RDSON x D (32) Switching losses are also associated with the internal NFET. They occur during the switch on and off transition periods, where voltages and currents overlap resulting in power loss. The simplest means to determine this loss is to empirically measure the rise and fall times (10% to 90%) of the switch at the switch node using Equation 33 through Equation 35. PSWF = 1/2 (VIN × IOUT × freq × TFALL) PSWR = 1/2(VIN x IOUT x freq x TRISE) PSW = PSWF + PSWR (33) (34) (35) Table 2. Typical Rise and Fall Times vs Input Voltage VIN TRISE TFALL 5V 8 ns 4 ns 10 V 9 ns 6 ns 15 V 10 ns 7 ns Another loss is the power required for operation of the internal circuitry: PQ = IQ x VIN (36) IQ is the quiescent operating current, and is typically around 1.5 mA. The other operating power that needs to be calculated is that required to drive the internal NFET: PBOOST = IBOOST x VBOOST (37) VBOOST is normally between 3 VDC and 5 VDC. The IBOOST rms current is approximately 4.25 mA. Total power losses are: 6PCOND + PSW + PDIODE + PIND + PQ + PBOOST = PLOSS (38) 8.2.1.2.9 Calculating the LM2734Z Junction Temperature Thermal Definitions: TJ = Chip junction temperature TA = Ambient temperature RθJC = Thermal resistance from chip junction to device case RθJA = Thermal resistance from chip junction to ambient air 16 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 Figure 12. Cross-Sectional View of Integrated Circuit Mounted on a Printed Circuit Board Heat in the LM2734Z due to internal power dissipation is removed through conduction and/or convection. Conduction: Heat transfer occurs through cross sectional areas of material. Depending on the material, the transfer of heat can be considered to have poor to good thermal conductivity properties (insulator vs conductor). Heat Transfer goes as: silicon→package→lead frame→PCB. Convection: Heat transfer is by means of airflow. This could be from a fan or natural convection. Natural convection occurs when air currents rise from the hot device to cooler air. Thermal impedance is defined as shown in Equation 39. RT = 'T Power (39) Thermal impedance from the silicon junction to the ambient air is defined as shown in Equation 40. TJ - TA RTJA = Power (40) This impedance can vary depending on the thermal properties of the PCB. This includes PCB size, weight of copper used to route traces and ground plane, and number of layers within the PCB. The type and number of thermal vias can also make a large difference in the thermal impedance. Thermal vias are necessary in most applications. They conduct heat from the surface of the PCB to the ground plane. Four to six thermal vias must be placed under the exposed pad to the ground plane if the WSON package is used. If the 6-pin SOT package is used, place two to four thermal vias close to the ground pin of the device. The data sheet specifies two different RθJA numbers for the thin SOT–6 package. The two numbers show the difference in thermal impedance for a four-layer board with 2-oz. copper traces, versus a four-layer board with 1oz. copper. RθJA equals 120°C/W for 2-oz. copper traces and GND plane, and 235°C/W for 1-oz. copper traces and GND plane. The first method to accurately measure the silicon temperature for a given application, two methods can be used. The first method requires the user to know the thermal impedance of the silicon junction to case. (RθJC) is approximately 80°C/W for the thin SOT-6 package. Knowing the internal dissipation from the efficiency calculation given previously, and the case temperature, which can be empirically measured on the bench: TJ - TC RTJA = Power (41) Therefore: TJ = (RθJC × PLOSS) + TC (42) Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 17 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com 6PCOND + PSWF + PSWR + PQ + PBOOST = PINTERNAL PINTERNAL = 322 mW TJ = (RTJC x Power) + TC = 80oC/W x 322 mW + TC (43) The second method can give a very accurate silicon junction temperature. The first step is to determine RθJA of the application. The LM2734Z has overtemperature protection circuitry. When the silicon temperature reaches 165°C, the device stops switching. The protection circuitry has a hysteresis of 15°C. Once the silicon temperature has decreased to approximately 150°C, the device starts to switch again. Knowing this, the RθJA for any PCB can be characterized during the early stages of the design by raising the ambient temperature in the given application until the circuit enters thermal shutdown. If the SW-pin is monitored, it is obvious when the internal NFET stops switching indicating a junction temperature of 165°C. Knowing the internal power dissipation from the above methods, the junction temperature and the ambient temperature, RθJA can be determined using Equation 44. 165oC - TA RTJA = PINTERNAL (44) Once this is determined, the maximum ambient temperature allowed for a desired junction temperature can be found using Equation 45. 6PCOND + PSWF + PSWR + PQ + PBOOST = PINTERNAL PINTERNAL = 322 mW (45) Using a standard Texas Instruments 6-pin SOT demonstration board to determine the RθJA of the board. The four layer PCB is constructed using FR4 with 1/2-oz copper traces. The copper ground plane is on the bottom layer. The ground plane is accessed by two vias. The board measures 2.5 cm × 3 cm. It was placed in an oven with no forced airflow. The ambient temperature was raised to 94°C, and at that temperature, the device went into thermal shutdown. RTJA = 165oC - 94oC 322 mW = 220oC/W (46) If the junction temperature was to be kept below 125°C, then the ambient temperature cannot go above 54.2°C. TJ - (RθJA × PLOSS) = TA (47) The method described above to find the junction temperature in the thin 6-pin SOT package can also be used to calculate the junction temperature in the WSON package. The 6-pin WSON package has a RθJC = 20°C/W, and RθJA can vary depending on the application. RθJA can be calculated in the same manner as described in method 2 (see LM2734Z Design Example 3). 8.2.1.2.10 WSON Package The LM2734Z is packaged in a thin, 6-pin SOT package and the 6-pin WSON. The WSON package has the same footprint as the thin, 6-pin SOT, but is thermally superior due to the exposed ground paddle on the bottom of the package. Figure 13. No Pullback WSON Configuration 18 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 RθJA of the WSON package is normally two to three times better than that of the thin, 6-pin SOT package for a similar PCB configuration (area, copper weight, thermal vias). FB 1 GND BOOST 2 3 6 EN 5 VIN 4 SW Figure 14. Dog Bone For certain high power applications, the PCB land may be modified to a dog bone shape (see Figure 14). By increasing the size of ground plane, and adding thermal vias, the RθJA for the application can be reduced. 6PCOND + PSWF + PSWR + PQ + PBOOST = PINTERNAL PINTERNAL = 322 mW (48) This example follows LM2734Z Design Example 2, but uses the WSON package. Using a standard Texas Instruments 6-pin WSON demonstration board, use Method 2 to determine RθJA of the board. The four-layer PCB is constructed using FR4 with 1- or 2-oz copper traces. The copper ground plane is on the bottom layer. The ground plane is accessed by four vias. The board measures 2.5 cm × 3 cm. It was placed in an oven with no forced airflow. The ambient temperature was raised to 113°C, and at that temperature, the device went into thermal shutdown. RTJAa = 165oC - 113oC 322 mW = 161oC/W (49) If the junction temperature is to be kept below 125°C, then the ambient temperature cannot go above 73.2°C. TJ - (RθJA × PLOSS) = TA (50) 8.2.1.2.11 Package Selection To determine which package you must use for your specific application, variables must be known before determining the appropriate package to use. 1. Maximum ambient system temperature 2. Internal LM2734Z power losses 3. Maximum junction temperature desired 4. RθJA of the specific application, or RθJC (WSON or 6-pin SOT) The junction temperature must be less than 125°C for the worst-case scenario. Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 19 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com Table 3 lists the bill of materials for LM2734Z design example 1. Table 3. Bill of Materials for Figure 11 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A Buck Regulator LM2734ZX Texas Instruments C1, Input Cap 10 µF, 6.3 V, X5R C3216X5ROJ106M TDK C2, Output Cap 10 µF, 6.3 V, X5R C3216X5ROJ106M TDK C3, Boost Cap 0.01 uF, 16 V, X7R C1005X7R1C103K TDK D1, Catch Diode 0.3 VF Schottky 1A, 10VR MBRM110L ON Semi D2, Boost Diode 1 VF at 50-mA Diode 1N4148W Diodes, Inc. L1 2.2 µH, 1.8 A ME3220–222MX Coilcraft R1 8.87 kΩ, 1% CRCW06038871F Vishay R2 10.2 kΩ, 1% CRCW06031022F Vishay R3 100 kΩ, 1% CRCW06031003F Vishay 8.2.1.3 Application Curve VIN=5.0 V VOUT = 1.5 V No load Figure 15. Typical Start-Up Profile 20 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 8.2.2 LM2734Z Design Example 2 D2 VIN BOOST VIN C3 C1 L1 R3 VOUT SW LM2734 ON D1 C2 EN OFF R1 FB GND R2 Figure 16. VBOOST Derived from VOUT 12 V to 3.3 V / 1 A 8.2.2.1 Design Requirements Table 4 lists the operating conditions for design example 2. Table 4. Design Parameters PARAMETER VALUE PARAMETER VALUE VIN 5.0 V POUT VOUT 2.5 V PDIODE 151 mW 2.5 W IOUT 1.0 A PIND 75 mW VD 0.35 V PSWF 53 mW Freq 3 MHz PSWR 53 mW IQ 1.5 mA PCOND 187 mW TRISE 8 ns PQ 7.5 mW TFALL 8 ns PBOOST 21 mW RDSON 330 mΩ PLOSS 548 mW INDDCR 75 mΩ D 56.8% 8.2.2.2 Detailed Design Procedure Refer to Detailed Design Procedure. Table 5 lists the bill of materials for LM2734Z design example 2. Table 5. Bill of Materials for Figure 16 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A Buck Regulator LM2734ZX Texas Instruments C1, Input Cap 10 µF, 25 V, X7R C3225X7R1E106M TDK C2, Output Cap 22 µF, 6.3 V, X5R C3216X5ROJ226M TDK C3, Boost Cap 0.01 µF, 16 V, X7R C1005X7R1C103K TDK D1, Catch Diode 0.34 VF Schottky 1A, 30VR SS1P3L Vishay D2, Boost Diode 0.6 VF at 30-mA Diode BAT17 Vishay L1 3.3 µH, 1.3 A ME3220–332MX Coilcraft R1 31.6 kΩ, 1% CRCW06033162F Vishay R2 10.0 kΩ, 1% CRCW06031002F Vishay R3 100 kΩ, 1% CRCW06031003F Vishay Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 21 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com 8.2.3 LM2734Z Design Example 3 C4 D3 R4 D2 BOOST VIN VIN C3 C1 R3 L1 VOUT SW LM2734 ON OFF D1 C2 EN R1 FB GND R2 Figure 17. VBOOST Derived from VSHUNT 18 V to 1.5 V / 1 A 8.2.3.1 Design Requirements Table 6 lists the operating conditions for design example 3. Table 6. Design Parameters PARAMETER VALUE PARAMETER VALUE Package SOT-6 POUT 2.475 W VIN 12.0 V PDIODE 523 mW VOUT 3.30 V PIND 56.25 mW IOUT 750 mA PSWF 108 mW VD 0.35 V PSWR 108 mW Freq 3 MHz PCOND 68.2 mW IQ 1.5 mA PQ IBOOST 4 mA VBOOST 5V TRISE 8 ns TFALL 8 ns RDSON 400 mΩ INDDCR 75 mΩ D 30.3% 22 Submit Documentation Feedback 18 mW PBOOST 20 mW PLOSS 902 mW Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 8.2.3.2 Detailed Design Procedure Refer to Detailed Design Procedure. Table 7 lists the bill of materials for LM2734Z design example 3. Table 7. Bill of Materials for Figure 17 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A Buck Regulator LM2734ZX Texas Instruments C1, Input Cap 10 µF, 25 V, X7R C3225X7R1E106M TDK C2, Output Cap 22 µF, 6.3 V, X5R C3216X5ROJ226M TDK C3, Boost Cap 0.01 µF, 16 V, X7R C1005X7R1C103K TDK C4, Shunt Cap 0.1 µF, 6.3 V, X5R C1005X5R0J104K TDK D1, Catch Diode 0.4 VF Schottky 1A, 30VR SS1P3L Vishay D2, Boost Diode 1 VF at 50-mA Diode 1N4148W Diodes, Inc. D3, Zener Diode 5.1 V 250-Mw SOT BZX84C5V1 Vishay L1 3.3 µH, 1.3 A ME3220–332MX Coilcraft R1 8.87 kΩ, 1% CRCW06038871F Vishay R2 10.2 kΩ, 1% CRCW06031022F Vishay R3 100 kΩ, 1% CRCW06031003F Vishay R4 4.12 kΩ, 1% CRCW06034121F Vishay 8.2.4 LM2734Z Design Example 4 D3 D2 BOOST VIN VIN C1 C3 R3 L1 VOUT SW LM2734 ON D1 EN C2 R1 OFF FB GND R2 Figure 18. VBOOST Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1 A Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 23 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com 8.2.4.1 Design Requirements Table 8 lists the operating conditions for design example 4. Table 8. Design Parameters PARAMETER VALUE PARAMETER VALUE POUT 2.475 W 12.0 V PDIODE 523 mW VOUT 3.3 V PIND 56.25 mW IOUT 750 mA PSWF 108 mW VD 0.35 V PSWR 108 mW Freq 3 MHz PCOND 68.2 mW IQ 1.5 mA PQ Package WSON-6 VIN IBOOST 4 mA VBOOST 5V TRISE 8 ns TFALL 8 ns RDSON 400 mΩ INDDCR 75 mΩ D 30.3% 18 mW PBOOST 20 mW PLOSS 902 mW 8.2.4.2 Detailed Design Procedure Refer to Detailed Design Procedure. Table 9 lists the bill of materials for LM2734Z design example 4. Table 9. Bill of Materials for Figure 18 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A Buck Regulator LM2734ZX Texas Instruments C1, Input Cap 10 µF, 25 V, X7R C3225X7R1E106M TDK C2, Output Cap 22 µF, 6.3 V, X5R C3216X5ROJ226M TDK C3, Boost Cap 0.01 µF, 16 V, X7R C1005X7R1C103K TDK D1, Catch Diode 0.4 VF Schottky 1A, 30VR SS1P3L Vishay D2, Boost Diode 1 VF at 50-mA Diode 1N4148W Diodes, Inc. D3, Zener Diode 11 V 350-Mw SOT BZX84C11T Diodes, Inc. L1 3.3 µH, 1.3 A ME3220–332MX Coilcraft R1 8.87 kΩ, 1% CRCW06038871F Vishay R2 10.2 kΩ, 1% CRCW06031022F Vishay R3 100 kΩ, 1% CRCW06031003F Vishay 24 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 8.2.5 LM2734Z Design Example 5 D3 D2 VIN BOOST VIN C3 C1 R3 L1 VOUT SW LM2734 ON D1 EN C2 R1 OFF FB GND R2 Figure 19. VBOOST Derived from Series Zener Diode (VOUT) 15 V to 9 V / 1 A 8.2.5.1 Design Requirements Table 10 lists the operating conditions for design example 5. Table 10. Design Parameters PARAMETER VALUE Package PARAMETER VALUE WSON-6 VIN 15.0 V POUT VOUT 9.0 V PDIODE 130 mW IOUT 1.0 A PIND 104 mW VD 0.35 V PCOND Freq 3 MHz PSW 382.5 mW IQ 1.5 mA PQ 22.5 mW PLOSS 825 mW TRISE 10 ns TFALL 7 ns RDSON 300 mΩ INDDCR 104 mΩ D 9W 186 mW 62% 8.2.5.2 Detailed Design Procedure Refer to Detailed Design Procedure. Table 11 lists the bill of materials for the LM2734Z design example 5. Table 11. Bill of Materials for Figure 19 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A Buck Regulator LM2734ZX Texas Instruments C1, Input Cap 10 µF, 25 V, X7R C3225X7R1E106M TDK C2, Output Cap 22 µF, 16 V, X5R C3216X5R1C226M TDK C3, Boost Cap 0.01 µF, 16 V, X7R C1005X7R1C103K TDK D1, Catch Diode 0.4 VF Schottky 1A, 30VR SS1P3L Vishay D2, Boost Diode 1 VF at 50-mA Diode 1N4148W Diodes, Inc. D3, Zener Diode 4.3 V 350-mw SOT BZX84C4V3 Diodes, Inc. L1 2.2 µH, 1.8 A ME3220–222MX Coilcraft R1 102 kΩ, 1% CRCW06031023F Vishay Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 25 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com Table 11. Bill of Materials for Figure 19 (continued) PART ID PART VALUE PART NUMBER MANUFACTURER R2 10.2 kΩ, 1% CRCW06031022F Vishay R3 100 kΩ, 1% CRCW06031003F Vishay 9 Power Supply Recommendations The LM2734Z is designed to operate from an input voltage supply range between 3 to 20 V. This input supply must be able to withstand the maximum input current and maintain voltage above 3.0 V. In case where input supply is located farther away (more than a few inches) from LM2734Z additional bulk capacitance may be required in addition to ceramic bypass capacitors. 10 Layout 10.1 Layout Guidelines When planning layout there are a few things to consider when trying to achieve a clean, regulated output. The most important consideration when completing the layout is the close coupling of the GND connections of the CIN capacitor and the catch diode D1. These ground ends must be close to one another and be connected to the GND plane with at least two through-holes. Place these components as close to the IC as possible. Next in importance is the location of the GND connection of the COUT capacitor, which must be near the GND connections of CIN and D1. There must be a continuous ground plane on the bottom layer of a two-layer board except under the switching node island. The FB pin is a high impedance node and care must be taken to make the FB trace short to avoid noise pickup and inaccurate regulation. The feedback resistors must be placed as close as possible to the IC, with the GND of R2 placed as close as possible to the GND of the IC. The VOUT trace to R1 must be routed away from the inductor and any other traces that are switching. High AC currents flow through the VIN, SW and VOUT traces, so they must be as short and wide as possible. However, making the traces wide increases radiated noise, so the designer must make this trade-off. Radiated noise can be decreased by choosing a shielded inductor. The remaining components must also be placed as close as possible to the IC. Please see the AN-1229 SIMPLE SWITCHER® PCB Layout Guidelines Application Note (SNVA054) for further considerations and the LM2734Z demo board as an example of a four-layer layout. 26 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 LM2734Z, LM2734Z-Q1 www.ti.com SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 10.2 Layout Examples Figure 20. Top Layer Figure 21. Bottom Layer Figure 22. Internal Plane 1 (GND) Figure 23. Internal Plane 2 (VIN) Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 Submit Documentation Feedback 27 LM2734Z, LM2734Z-Q1 SNVS334F – JANUARY 2005 – REVISED JANUARY 2016 www.ti.com 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 Documentation Support 11.2.1 Related Documentation For related documentation see the following: • AN-1229 SIMPLE SWITCHER® PCB Layout Guidelines Application Note (SNVA054) • AN-1350 LM2734 Evaluation Board User's Guide (SNVA100) 11.3 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. 11.4 Trademarks WEBENCH, E2E are trademarks of Texas Instruments. All other trademarks are the property of their respective owners. 11.5 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. 11.6 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. 28 Submit Documentation Feedback Copyright © 2005–2016, Texas Instruments Incorporated Product Folder Links: LM2734Z LM2734Z-Q1 PACKAGE OPTION ADDENDUM www.ti.com 10-Dec-2020 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) LM2734ZMK/NOPB ACTIVE SOT-23-THIN DDC 6 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 SFTB LM2734ZMKX/NOPB ACTIVE SOT-23-THIN DDC 6 3000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 SFTB LM2734ZQMKE/NOPB ACTIVE SOT-23-THIN DDC 6 250 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 SVBB LM2734ZQSDE/NOPB ACTIVE WSON NGG 6 250 RoHS & Green SN Level-3-260C-168 HR -40 to 125 L238B LM2734ZSD/NOPB ACTIVE WSON NGG 6 1000 RoHS & Green SN Level-3-260C-168 HR -40 to 125 L163B (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. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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