LM5018SD/NOPB - Texas Instruments

VIN

BST

RON

RTN

VCC

VIN

VOUT

RFB1

UV1

RON

COUT

BST

RFB2

RUV2

UVLO

CVCC

LM5018

7.5 V - 100 V

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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.

LM5018

SNVS787H –JANUARY 2012–REVISED NOVEMBER 2017

LM5018 100-V, 300-mA Constant On-Time Synchronous Buck Regulator

1 Features

1• Wide 7.5- to 100-V Input Range

• Integrated 300-mA High-Side and

Low-Side Switches

• No Schottky Required

• Constant On-time Control

• No Loop Compensation Required

• Ultra-Fast Transient Response

• Nearly Constant Operating Frequency

• Intelligent Peak Current Limit

• Adjustable Output Voltage From 1.225 V

• Precision 2% Feedback Reference

• Frequency Adjustable to 1 MHz

• Adjustable Undervoltage Lockout

• Remote Shutdown

• Thermal Shutdown

• Packages:

– WSON-8

– SO PowerPAD™-8

• Create a Custom Design Using the LM5018 With

the WEBENCH®Power Designer

2 Applications

• Smart Power Meters

• Telecommunication Systems

• Automotive Electronics

• Isolated Bias Supply

3 Description

The LM5018 is a 100-V, 300-mA synchronous step-

down regulator with integrated high-side and low-side

MOSFETs. The constant-on-time (COT) control

scheme employed in the LM5018 device requires no

loop compensation, provides excellent transient

response, and enables very low step-down ratios.

The on-time varies inversely with the input voltage

resulting in nearly constant frequency over the input

voltage range. A high-voltage startup regulator

provides bias power for internal operation of the IC

and for integrated gate drivers.

A peak current limit circuit protects against overload

conditions. The undervoltage lockout (UVLO) circuit

allows the input undervoltage threshold and

hysteresis to be independently programmed. Other

protection features include thermal shutdown and

bias supply undervoltage lockout.

The LM5018 device is available in WSON-8 and SO

PowerPAD-8 plastic packages.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)

LM5018 SO PowerPAD (8) 4.89 mm × 3.90 mm

WSON (8) 4.00 mm × 4.00 mm

(1) For all available packages, see the orderable addendum at

the end of the data sheet.

Typical Application

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Table of Contents

1 Features.................................................................. 1

2 Applications ........................................................... 1

3 Description............................................................. 1

4 Revision History..................................................... 2

5 Pin Configuration and Functions......................... 4

6 Specifications......................................................... 5

6.1 Absolute Maximum Ratings ..................................... 5

6.2 ESD Ratings ............................................................ 5

6.3 Recommended Operating Conditions....................... 5

6.4 Thermal Information.................................................. 5

6.5 Electrical Characteristics........................................... 6

6.6 Timing Requirements................................................ 6

6.7 Typical Characteristics.............................................. 7

7 Detailed Description.............................................. 9

7.1 Overview................................................................... 9

7.2 Functional Block Diagram......................................... 9

7.3 Feature Description................................................. 10

7.4 Device Functional Modes........................................ 14

8 Application and Implementation ........................ 15

8.1 Application Information............................................ 15

8.2 Typical Applications ................................................ 15

9 Power Supply Recommendations...................... 24

10 Layout................................................................... 24

10.1 Layout Guidelines ................................................. 24

10.2 Layout Example .................................................... 24

11 Device and Documentation Support................. 25

11.1 Device Support...................................................... 25

11.2 Documentation Support ........................................ 25

11.3 Receiving Notification of Documentation Updates 25

11.4 Community Resources.......................................... 25

11.5 Trademarks........................................................... 25

11.6 Electrostatic Discharge Caution............................ 25

11.7 Glossary................................................................ 26

12 Mechanical, Packaging, and Orderable

Information........................................................... 26

4 Revision History

Changes from Revision G (October 2015) to Revision H Page

• Added WEBENCH links to the data sheet.............................................................................................................................. 1

• Deleted lead temperature from the Absolute Maximum Ratings table .................................................................................. 5

• Added Receiving Notification of Documentation Updates section ....................................................................................... 25

Changes from Revision F (December 2014) to Revision G Page

• Changed 14 V to 13 V in VCC Regulator section ................................................................................................................. 11

• Changed 8 to 4 on equation in Input Capacitor section....................................................................................................... 17

• Changed 0.17 μF to 0.34 μF in Input Capacitor section....................................................................................................... 17

Changes from Revision E (December 2013) to Revision F Page

• Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional

Modes,Application and Implementation section, Power Supply Recommendations section, Layout section, Device

and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1

• Changed input voltage in Typical Application schematic ...................................................................................................... 1

• Added package designators to pin out drawings. ................................................................................................................. 4

• Changed Thermal Information table....................................................................................................................................... 5

• Changed Soft-Start Circuit graphic....................................................................................................................................... 14

• Changed Frequency Selection,Inductor Selection,Output Capacitor,Input Capacitor, and UVLO Resistors sections..... 15

• Changed Series Ripple Resistor RCsection to Type III Ripple Circuit ................................................................................ 17

Changes from Revision D (December 2013) to Revision E Page

• Added Thermal Parameters. .................................................................................................................................................. 5

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Changes from Revision C (September 2013) to Revision D Page

• Changed formatting throughout document to be TI compliant............................................................................................... 1

• Changed minimum operating input voltage from 9 V to 7.5 V in Features ........................................................................... 1

• Changed minimum operating input voltage from 9 V to 7.5 V in Typical Application ........................................................... 1

• Changed minimum operating input voltage from 9 V to 7.5 V in Pin Descriptions ............................................................... 4

• Added Maximum Junction Temperature................................................................................................................................. 5

Changes from Revision B (February 2012) to Revision C Page

• Added SW to RTN (100 ns transient) in Absolute Maximum Ratings ................................................................................... 5

BST

VCC

UVLO

RON

RTN

VIN WSON-8

Exp Pad

UVLO 3

RON 4

RTN 1

VIN 2

8 SW

7 BST

6 VCC

5 FB

PowePAD-8

Exp Pad

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5 Pin Configuration and Functions

DDA Package

8-Pin SO PowerPAD

Top View

NGU Package

8-Pin WSON

Top View

Pin Functions

PIN I/O DESCRIPTION APPLICATION INFORMATION

NO. NAME

1 RTN — Ground Ground connection of the integrated circuit.

2 VIN I Input Voltage Operating input range is 7.5 V to 100 V.

3 UVLO I Input Pin of Undervoltage Comparator

Resistor divider from VIN to UVLO to GND programs the

undervoltage detection threshold. An internal current source

is enabled when UVLO is above 1.225 V to provide

hysteresis. When UVLO pin is pulled below 0.66 V

externally, the parts goes in shutdown mode.

4 RON I On-Time Control A resistor between this pin and VIN sets the switch on-time

as a function of VIN. Minimum recommended on-time is

100 ns at max input voltage.

5 FB I Feedback This pin is connected to the inverting input of the internal

regulation comparator. The regulation level is 1.225 V.

6 VCC O Output From the Internal High Voltage

Series Pass Regulator.

Regulated at 7.6 V

The internal VCC regulator provides bias supply for the gate

drivers and other internal circuitry. A 1.0-μF decoupling

capacitor is recommended.

7 BST I Bootstrap Capacitor

An external capacitor is required between the BST and SW

pins

(0.01-μF ceramic). The BST pin capacitor is charged by the

VCC regulator through an internal diode when the SW pin is

low.

8 SW O Switching Node Power switching node. Connect to the output inductor and

bootstrap capacitor.

— EP — Exposed Pad Exposed pad must be connected to RTN pin. Connect to

system ground plane on application board for reduced

thermal resistance.

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(1) Absolute Maximum Ratings are limits beyond which damage to the device may occur. Recommended Operating Conditions are

conditions under which operation of the device is intended to be functional. For verified specifications and test conditions, see the

Electrical Characteristics.The RTN pin is the GND reference electrically connected to the substrate.

(2) High junction temperatures degrade operating lifetimes. Operating lifetime is de-rated for junction temperatures greater than 125°C

6 Specifications

6.1 Absolute Maximum Ratings(1)

MIN MAX UNIT

VIN, UVLO to RTN –0.3 100 V

SW to RTN –1.5 VIN + 0.3 V

SW to RTN (100 ns transient) –5 VIN + 0.3 V

BST to VCC 100 V

BST to SW 13 V

RON to RTN –0.3 100 V

VCC to RTN –0.3 13 V

FB to RTN –0.3 5 V

Maximum junction temperature(2) 150 °C

Storage temperature range, Tstg –55 150 °C

(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.

(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

6.2 ESD Ratings VALUE UNIT

V(ESD) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2000 V

Charged-device model (CDM), per JEDEC specification JESD22-C101(2) ±750

(1) Recommended Operating Conditions are conditions under the device is intended to be functional. For specifications and test conditions,

see Electrical Characteristics.

(2) High junction temperatures degrade operating lifetimes. Operating lifetime is de-rated for junction temperatures greater than 125°C.

6.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)(1)

MIN MAX UNIT

VIN voltage 7.5 100 V

Operating junction temperature(2) –40 125 °C

(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report (SPRA953).

6.4 Thermal Information

THERMAL METRICS(1)

LM5018

UNITNGU (WSON) DDA (SO

PowerPAD)

8 PINS 8 PINS

RθJA Junction-to-ambient thermal resistance 41.3 41.1 °C/W

RθJCbot Junction-to-case (bottom) thermal resistance 3.2 2.4 °C/W

ΨJB Junction-to-board thermal characteristic parameter 19.2 24.4 °C/W

RθJB Junction-to-board thermal resistance 19.1 30.6 °C/W

RθJCtop Junction-to-case (top) thermal resistance 34.7 37.3 °C/W

ΨJT Junction-to-top thermal characteristic parameter 0.3 6.7 °C/W

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(1) All hot and cold limits are specified by correlating the electrical characteristics to process and temperature variations and applying

statistical process control.

(2) VCC provides self bias for the internal gate drive and control circuits. Device thermal limitations limit external loading.

6.5 Electrical Characteristics

Typical values correspond to TJ= 25°C. Minimum and maximum limits apply over –40°C to 125°C junction temperature

range, unless otherwise stated. VIN = 48 V unless otherwise stated. See(1) .

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

VCC SUPPLY

VCC Reg VCC Regulator Output VIN = 48 V, ICC = 20 mA 6.25 7.6 8.55 V

VCC Current Limit VIN = 48 V(2) 26 mA

VCC Undervoltage Lockout

Voltage (VCC increasing) 4.15 4.5 4.9 V

VCC Undervoltage Hysteresis 300 mV

VCC Drop Out Voltage VIN = 9 V, ICC = 20 mA 2.3 V

IIN Operating Current Nonswitching, FB = 3 V 1.75 mA

IIN Shutdown Current UVLO = 0 V 50 225 µA

SWITCH CHARACTERISTICS

Buck Switch RDS(ON) ITEST = 200 mA, BST-SW = 7 V 0.8 1.8 Ω

Synchronous RDS(ON) ITEST = 200 mA 0.45 1 Ω

Gate Drive UVLO VBST −VSW Rising 2.4 3 3.6 V

Gate Drive UVLO Hysteresis 260 mV

CURRENT LIMIT

Current Limit Threshold 390 575 750 mA

Current Limit Response Time Time to Switch Off 150 ns

OFF-Time Generator (Test 1) FB = 0.1 V, VIN = 48 V 12 µs

OFF-Time Generator (Test 2) FB = 1.0 V, VIN = 48 V 2.5 µs

REGULATION AND OVERVOLTAGE COMPARATORS

FB Regulation Level Internal Reference Trip Point for

Switch ON 1.2 1.225 1.25 V

FB Overvoltage Threshold Trip Point for Switch OFF 1.62 V

FB Bias Current 60 nA

UNDERVOLTAGE SENSING FUNCTION

UV Threshold UV Rising 1.19 1.225 1.26 V

UV Hysteresis Input Current UV = 2.5 V –10 –20 –29 µA

Remote Shutdown Threshold Voltage at UVLO Falling 0.32 0.66 V

Remote Shutdown Hysteresis 110 mV

THERMAL SHUTDOWN

Tsd Thermal Shutdown Temperature 165 °C

Thermal Shutdown Hysteresis 20 °C

6.6 Timing Requirements

Typical values correspond to TJ= 25°C. Minimum and maximum limits apply over –40°C to 125°C junction temperature range

unless otherwise stated. VIN = 48 V, unless otherwise stated. MIN NOM MAX UNIT

ON-TIME GENERATOR

TON Test 1 VIN = 32 V, RON = 100 kΩ270 350 460 ns

TON Test 2 VIN = 48 V, RON = 100 kΩ188 250 336 ns

TON Test 3 VIN = 75 V, RON = 250 kΩ250 370 500 ns

TON Test 4 VIN = 10 V, RON = 250 kΩ1880 3200 4425 ns

MINIMUM OFF-TIME

Minimum Off-Timer FB = 0 V 144 ns

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6.7 Typical Characteristics

Figure 1. Efficiency at 240 kHz, 10 V Figure 2. VCC vs VIN

Figure 3. VCC vs ICC Figure 4. ICC vs External VCC

Figure 5. TON vs VIN and RON Figure 6. TOFF (ILIM) vs VFB and VIN

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Typical Characteristics (continued)

Figure 7. IIN vs VIN (Operating, Non-Switching) Figure 8. IIN vs VIN (Shutdown)

Figure 9. Switching Frequency vs VIN

VIN VCC

RTN

BST

1.225V

VILIM

LM5018

RON

ILIM

COMPARATOR

V UVLO

ON/OFF

TIMERS

COT CONTROL

LOGIC

1.225V

START-UP

REGULATOR

VIN

FEEDBACK

DISABLE

THERMAL

SHUTDOWN

UVLO

OVER-VOLTAGE

1.62V

UVLO

4.5V

SHUTDOWN

VDD REG

BG REF

0.66V

20 µA

CURRENT

LIMIT

ONE-SHOT

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7 Detailed Description

7.1 Overview

The LM5018 step-down switching regulator features all the functions needed to implement a low-cost, efficient,

buck converter capable of supplying up to 300 mA to the load. This high-voltage regulator contains 100 V, N-

channel buck and synchronous switches, is easy to implement, and is provided in thermally enhanced SO

PowerPAD-8 and WSON-8 packages. The regulator operation is based on a constant on-time control scheme

using an on-time inversely proportional to VIN. This control scheme does not require loop compensation. The

current limit is implemented with a forced off-time inversely proportional to VOUT. This scheme ensures short

circuit protection while providing minimum foldback. The simplified block diagram of the LM5018 is shown in the

Functional Block Diagram section.

The LM5018 device can be applied in numerous applications to efficiently regulate down higher voltages. This

regulator is well-suited for 48 V telecom and automotive power bus ranges. Protection features include: thermal

shutdown, undervoltage lockout, minimum forced off-time, and an intelligent current limit.

7.2 Functional Block Diagram

SW L1

COUT

RFB2

VOUT

LM5018

RFB1

VOUT

(low ripple)

RFB2 + RFB1

VOUT = 1.225V x RFB1

VOUT

gSW = K x RON

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7.3 Feature Description

7.3.1 Control Overview

The LM5018 buck regulator employs a control principle based on a comparator and a one-shot on-timer, with the

output voltage feedback (FB) compared to an internal reference (1.225 V). If the FB voltage is below the

reference the internal buck switch is turned on for the one-shot timer period, which is a function of the input

voltage and the programming resistor (RON). Following the on-time the switch remains off until the FB voltage

falls below the reference, but never before the minimum off-time forced by the minimum off-time one-shot timer.

When the FB pin voltage falls below the reference and the minimum off-time one-shot period expires, the buck

switch is turned on for another on-time one-shot period. This will continue until regulation is achieved and the FB

voltage is approximately equal to 1.225 V (typ).

In a synchronous buck converter, the low side (sync) FET is 'on' when the high side (buck) FET is 'off.' The

inductor current ramps up when the high side switch is ‘on’ and ramps down when the high side switch is ‘off’.

There is no diode emulation feature in this IC, and therefore, the inductor current may ramp in the negative

direction at light load. This causes the converter to operate in continuous conduction mode (CCM) regardless of

the output loading. The operating frequency remains relatively constant with load and line variations. The

operating frequency can be calculated as shown in Equation 1.

where

• K = 9 × 10–11 (1)

The output voltage (VOUT) is set by two external resistors (RFB1, RFB2). The regulated output voltage is calculated

as shown in Equation 2.

(2)

This regulator regulates the output voltage based on ripple voltage at the feedback input, requiring a minimum

amount of ESR for the output capacitor (COUT). A minimum of 25 mV of ripple voltage at the feedback pin (FB) is

required for the LM5018. In cases where the capacitor ESR is too small, additional series resistance may be

required (RCin Figure 10).

For applications where lower output voltage ripple is required, the output can be taken directly from a low ESR

output capacitor, as shown in Figure 10. However, RCslightly degrades the load regulation.

Figure 10. Low Ripple Output Configuration

7.3.2 VCC Regulator

The LM5018 device contains an internal high-voltage linear regulator with a nominal output of 7.6 V. The input

pin (VIN) can be connected directly to the line voltages up to 100 V. The VCC regulator is internally current limited

to 30 mA. The regulator sources current into the external capacitor at VCC. This regulator supplies current to

internal circuit blocks including the synchronous MOSFET driver and the logic circuits. When the voltage on the

VCC pin reaches the undervoltage lockout (VCC UVLO) threshold of 4.5 V, the IC is enabled.

An internal diode connected from VCC to the BST pin replenishes the charge in the gate drive bootstrap capacitor

when SW pin is low.

0.07 x VIN

TOFF(ILIM) = VFB + 0.2V Ps

10-10 x RON

TON = VIN

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Feature Description (continued)

At high-input voltages, the power dissipated in the high voltage regulator is significant and can limit the overall

achievable output power. As an example, with the input at 48 V and switching at high frequency, the VCC

regulator may supply up to 7 mA of current resulting in 48 V × 7 mA = 336 mW of power dissipation. If the VCC

voltage is driven externally by an alternate voltage source between 8.55 V and 13 V, the internal regulator is

disabled. This reduces the power dissipation in the IC.

7.3.3 Regulation Comparator

The feedback voltage at FB is compared to an internal 1.225 V reference. In normal operation, when the output

voltage is in regulation, an on-time period is initiated when the voltage at FB falls below 1.225 V. The high side

switch will stay on for the on-time, causing the FB voltage to rise above 1.225 V. After the on-time period, the

high side switch will stay off until the FB voltage again falls below 1.225 V. During start-up, the FB voltage will be

below 1.225 V at the end of each on-time, causing the high side switch to turn on immediately after the minimum

forced off-time of 144 ns. The high side switch can be turned off before the on-time is over if the peak current in

the inductor reaches the current limit threshold.

7.3.4 Overvoltage Comparator

The feedback voltage at FB is compared to an internal 1.62 V reference. If the voltage at FB rises above 1.62 V

the on-time pulse is immediately terminated. This condition can occur if the input voltage and/or the output load

changes suddenly. The high-side switch will not turn on again until the voltage at FB falls below 1.225 V.

7.3.5 On-Time Generator

The on-time for the LM5018 is determined by the RON resistor and is inversely proportional to the input voltage

(VIN), resulting in a nearly constant frequency as VIN is varied over its range. The on-time for the LM5018 can be

calculated using Equation 3.

(3)

See Figure 5. RON should be selected for a minimum on-time (at maximum VIN) greater than 100 ns, for proper

operation. This requirement limits the maximum switching frequency for high VIN.

7.3.6 Current Limit

The LM5018 device contains an intelligent current limit off-timer. If the current in the buck switch exceeds 575

mA, the present cycle is immediately terminated, and a non-resetable off-timer is initiated. The length of off-time

is controlled by the FB voltage and the input voltage VIN. As an example, when FB = 0 V and VIN = 48 V, the

maximum off-time is set to 16 μs. This condition occurs when the output is shorted, and during the initial part of

start-up. This amount of time ensures safe short circuit operation up to the maximum input voltage of 100 V.

In cases of overload where the FB voltage is above zero volts (not a short circuit) the current limit off-time is

reduced. Reducing the off-time during less severe overloads reduces the amount of foldback, recovery time, and

start-up time. The off-time is calculated from Equation 4.

(4)

The current limit protection feature is peak limited. The maximum average output will be less than the peak.

7.3.7 N-Channel Buck Switch and Driver

The LM5018 device integrates an N-Channel Buck switch and associated floating high voltage gate driver. The

gate driver circuit works in conjunction with an external bootstrap capacitor and an internal high voltage diode. A

0.01-uF ceramic capacitor connected between the BST pin and the SW pin provides the voltage to the driver

during the on-time. During each off-time, the SW pin is at approximately 0 V, and the bootstrap capacitor charges

from VCC through the internal diode. The minimum off-timer, set to 144 ns, ensures a minimum time each cycle to

recharge the bootstrap capacitor.

+VIN

UVLO

VIN

RUV1

CIN RUV2

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Feature Description (continued)

7.3.8 Synchronous Rectifier

The LM5018 device provides an internal synchronous N-Channel MOSFET rectifier. This MOSFET provides a

path for the inductor current to flow when the high-side MOSFET is turned off.

The synchronous rectifier has no diode emulation mode, and is designed to keep the regulator in continuous

conduction mode even during light loads which would otherwise result in discontinuous operation.

7.3.9 Undervoltage Detector

The LM5018 device contains a dual level undervoltage lockout (UVLO) circuit. A summary of threshold voltages

and operational states is provided in Device Functional Modes.When the UVLO pin voltage is below 0.66 V, the

regulator is in a low current shutdown mode. When the UVLO pin voltage is greater than 0.66 V but less than

1.225 V, the regulator is in standby mode. In standby mode the VCC bias regulator is active while the regulator

output is disabled. When the VCC pin exceeds the VCC undervoltage threshold and the UVLO pin voltage is

greater than 1.225 V, normal operation begins. An external set-point voltage divider from VIN to GND can be

used to set the minimum operating voltage of the regulator.

UVLO hysteresis is accomplished with an internal 20-μA current source that is switched on or off into the

impedance of the set-point divider. When the UVLO threshold is exceeded, the current source is activated to

quickly raise the voltage at the UVLO pin. The hysteresis is equal to the value of this current times the resistance

RUV2.

If the UVLO pin is connected directly to the VIN pin, the regulator will begin operation once the VCC undervoltage

is satisfied.

Figure 11. UVLO Resistor Setting

7.3.10 Thermal Protection

The LM5018 device should be operated so the junction temperature does not exceed 150°C during normal

operation. An internal Thermal Shutdown circuit is provided to protect the LM5018 in the event of a higher than

normal junction temperature. When activated, typically at 165°C, the controller is forced into a low power reset

state, disabling the buck switch and the VCC regulator. This feature prevents catastrophic failures from accidental

device overheating. When the junction temperature reduces below 145°C (typical hysteresis = 20°C), the VCC

regulator is enabled, and normal operation is resumed.

7.3.11 Ripple Configuration

LM5018 uses Constant-On-Time (COT) control scheme, in which the on-time is terminated by an on-timer, and

the off-time is terminated by the feedback voltage (VFB) falling below the reference voltage (VREF). Therefore, for

stable operation, the feedback voltage must decrease monotonically, in phase with the inductor current during

the off-time. Furthermore, this change in feedback voltage (VFB) during off-time must be large enough to

suppress any noise component present at the feedback node.

Table 1 shows three different methods for generating appropriate voltage ripple at the feedback node. Type 1

and Type 2 ripple circuits couple the ripple at the output of the converter to the feedback node (FB). The output

voltage ripple has two components:

1. Capacitive ripple caused by the inductor current ripple charging/discharging the output capacitor.

2. Resistive ripple caused by the inductor current ripple flowing through the ESR of the output capacitor.

RFB1 x RFB2

R2 x (RFB1 + RFB2) + RFB1 x RFB2

VFB = (VCC - VD) x

ûIL(MIN)

25 mV

gsw(RFB2||RFB1)

C >

Cr = 3300 pF

RrCr<

Cac = 100 nF

(VIN(MIN) - VOUT) x TON

25 mV

RCûIL(MIN)

VOUT

VREF

GND

To FB

COUT

RFB2

RFB1

VOUT

GND

To FB

COUT

RFB2

RFB1

VOUT

Cac

COUT

VOUT

GND

Cac

To FB

RFB2

RFB1

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Feature Description (continued)

The capacitive ripple is not in phase with the inductor current. As a result, the capacitive ripple does not

decrease monotonically during the off-time. The resistive ripple is in phase with the inductor current and

decreases monotonically during the off-time. The resistive ripple must exceed the capacitive ripple at the output

node (VOUT) for stable operation. If this condition is not satisfied unstable switching behavior is observed in COT

converters, with multiple on-time bursts in close succession followed by a long off-time.

Type 3 ripple method uses Rrand Crand the switch node (SW) voltage to generate a triangular ramp. This

triangular ramp is ac coupled using Cac to the feedback node (FB). Because this circuit does not use the output

voltage ripple, it is ideally suited for applications where low output voltage ripple is required. See AN-1481

Controlling Output Ripple and Achieving ESR Independence in Constant On-Time (COT) Regulator Designs

(SNVA166) for more details for each ripple generation method.

Table 1. Ripple Configuration

TYPE 1

LOWEST COST CONFIGURATION TYPE 2

REDUCED RIPPLE CONFIGURATION TYPE 3

MINIMUM RIPPLE CONFIGURATION

(5)

(6) (7)

7.3.12 Soft-Start

A soft-start feature can be implemented with the LM5018 using an external circuit. As shown in Figure 12, the

soft-start circuit consists of one capacitor, C1, two resistors, R1and R2, and a diode, D. During the initial start-up,

the VCC voltage is established prior to the VOUT voltage. Capacitor C1is discharged and D is thereby forward

biased to pull up the FB voltage. The FB voltage exceeds the reference voltage (1.225 V) and switching is

therefore disabled. As capacitor C1charges, the voltage at node B gradually decreases and switching

commences. VOUT will gradually rise to maintain the FB voltage at the reference voltage. Once the voltage at

node B is less than a diode drop above FB voltage, the soft-start sequence is finished and D is reverse biased.

During the initial part of the start-up, the FB voltage can be approximated as follows. Please note that the effect

of R1has been ignored to simplify the calculation shown in Equation 8.

(8)

C1 is charged after the first start up. Diode D1 is optional and can be added to discharge C1 and initialize the

soft-start sequence when the input voltage experiences a momentary drop.

VOUT

RFB2

VCC

RFB1

To FB D

RFB1 x RFB2

RFB1 + RFB2

tS = C1 x (R2 + )

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To achieve the desired soft-start, the following design guidance is recommended:

1. R2is selected so that VFB is higher than 1.225 V for a VCC of 4.5 V, but is lower than 5 V when VCC is 8.55 V.

If an external VCC is used, VFB should not exceed 5 V at maximum VCC.

2. C1is selected to achieve the desired start-up time that can be determined from Equation 9.

(9)

3. R1is used to maintain the node B voltage at zero after the soft-start is finished. A value larger than the

feedback resistor divider is preferred. Note that the effect of R1is ignored in the previous equations.

Based on the schematic shown in Figure 13, selecting C1= 1 uF, R2=1kΩ, R1= 30 kΩresults in a soft-start

time of about 2 ms.

Figure 12. Soft-Start Circuit

7.4 Device Functional Modes

The UVLO pin controls the operating mode of the LM5018 device (see Table 2 for the detailed functional states).

Table 2. UVLO Mode

UVLO VCC MODE DESCRIPTION

< 0.66 V Disabled Shutdown VCC regulator disabled.

Switching disabled.

0.66 V — 1.225 V Enabled Standby VCC regulator enabled

Switching disabled.

> 1.225 V VCC < 4.5 V Standby VCC regulator enabled.

Switching disabled.

VCC > 4.5 V Operating VCC enabled.

Switching enabled.

VIN BST

RON

RTN

VCC

VIN

VOUT

UVLO

LM5018

12V - 95V

1 F0.1 F127 NŸ

14 NŸ

237 NŸ

GND

(TP1)

(TP2)

UVLO/SD

U1 R6

(TP3)

(TP5)

GND

EXP 1 NŸ

6.98 NŸ

4.7 F

1.5Ÿ

220 H

0.01 F

1 F

0.1 F

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8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The LM5018 device is step-down DC-DC converter. The device is typically used to convert a higher DC voltage

to a lower DC voltage with a maximum available output current of 300 mA. Use the following design procedure to

select component values for the LM5018 device. Alternately, use the WEBENCH®software to generate a

complete design. The WEBENCH software uses an iterative design procedure and accesses a comprehensive

database of components when generating a design. This section presents a simplified discussion of the design

process.

8.2 Typical Applications

8.2.1 Application Circuit: 12.5- to 95-V Input and 10-V, 300-mA Output Buck Converter

The application schematic of a buck supply is shown in Figure 13. For output voltage (VOUT) above the maximum

regulation threshold of VCC (8.55 V, see Electrical Characteristics), the VCC pin can be connected to VOUT through

a diode (D2), for higher efficiency and lower power dissipation in the IC.

The design example below uses equations from the Feature Description with component names provided in the

Typical Application schematic. Corresponding component designators from Figure 13 are also provided for each

selected value.

Figure 13. 12.5-V to 95-V Input and 10-V, 300-mA Output Buck Converter

8.2.1.1 Design Requirements

Selection of external components is illustrated through a design example. The design example specifications are

shown in Table 3.

Table 3. Buck Converter Design Specifications

DESIGN PARAMETERS VALUE

Input Range 12.5 V to 95 V, transients up to 100 V

Output Voltage 10 V

Maximum Output Current 300 mA

Nominal Switching Frequency ≈440 kHz

LI OUT I (max)

I (peak) I 346 mA



VIN - VOUT

ûIL = L1 x gSW

VOUT

VIN

OUT

SW ON

¦K R

DMIN

gSW(MAX) = TON(MIN)

10/48

100 ns

= = 2.1 MHz

1 - DMAX

gSW(MAX) = TOFF(MIN)

1 - 10/12.5

200 ns

= = 1 MHz

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8.2.1.2 Detailed Design Procedure

8.2.1.2.1 Custom Design With WEBENCH® Tools

Click here to create a custom design using the LM5018 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.

8.2.1.2.2 RFB1, RFB2

VOUT = VFB × (RFB2 / RFB1 + 1), and since VFB = 1.225 V, the ratio of RFB2 to RFB1 is calculated to be 7:1.

Standard values are chosen with RFB2 = R1 = 6.98 kΩand RFB1 = R6 = 1.00 kΩ. Other values could be used as

long as the 7:1 ratio is maintained.

8.2.1.2.3 Frequency Selection

At the minimum input voltage, the maximum switching frequency of LM5018 is restricted by the forced minimum

off-time (TOFF(MIN)) as given by Equation 10.

(10)

Similarly, at maximum input voltage, the maximum switching frequency of LM5018 is restricted by the minimum

TON as given by Equation 11.

(11)

Resistor RON sets the nominal switching frequency based on Equation 12.

(12)

Where:

K = 9 × 10–11

Operation at high switching frequency results in lower efficiency while providing the smallest solution. For this

example, 440 kHz was selected, resulting in RON = 253 kΩ. A standard value for RON = R3 = 237 kΩis selected.

8.2.1.2.4 Inductor Selection

The minimum inductance is selected to limit the inductor ripple current to 20 to 40 percent of the maximum load

current. In addition, the peak inductor current at maximum load must be smaller than the minimum current limit

threshold provided in Electrical Characteristics. The inductor current ripple is given by Equation 13.

(13)

The maximum ripple is observed at maximum input voltage. Substituting VIN = 95 V and ΔIL = 40 percent ×

IOUT(max) results in L1 = 169 μH. The higher standard value of 220 μH is chosen. With this value of inductance,

peak-to-peak minimum and maximum inductor current ripple of 27 mA and 92 mA occur at the minimum and

maximum input voltages, respectively. The peak inductor and switch current is given by Equation 14.

(14)

VIN(HYS) =IHYS x RUV2

IOUT(MAX)

CIN 4 x gSW x ûVIN

ûIL(MIN)

25 mV

gsw(RFB2||RFB1)

Cac >

ûIL

COUT = 8 x gsw x ûVripple

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The peak inductor current of 346 mA is smaller than the minimum current limit threshold of 390 mA. The selected

inductor should be able to operate at the maximum current limit of 750 mA during startup and overload

conditions without saturating.

8.2.1.2.5 Output Capacitor

The output capacitor is selected to minimize the capacitive ripple across it. The maximum ripple is observed at

maximum input voltage and is given by Equation 15.

(15)

Where:

ΔVripple is the voltage ripple across the capacitor and ΔILis the peak-to-peak inductor ripple current.

Assuming VIN = 95 V and substituting ΔVripple = 10 mV gives COUT = 2.6 μF. A 4.7-μF standard value is selected

for COUT = C9. An X5R or X7R type capacitor with a voltage rating 16 V or higher should be selected.

8.2.1.2.6 Type II Ripple Circuit

Type II ripple circuit, as described in Ripple Configuration,is chosen for this example. For a constant on time

converter to be stable, the injected in-phase ripple should be larger than the capacitive ripple on COUT.

Using type II ripple circuit equations with minimum FB pin ripple of 25 mV, the values of the series resistor RC

and ac coupling capacitor Cac can calculated.

(16)

Assuming RFB2 = 6.98 kΩand RFB1 =1kΩ, the calculated minimum value of Cac is 0.013 µF. A standard value of

0.1 µF is selected for Cac = C8. The value of the series output resistor RCis calculated for the minimum input

voltage condition when the inductor ripple current as at a minimum. Using Equation 13 and assuming VIN = 12.5

V, the minimum inductor ripple current is 27 mA. The calculated minimum value of RCis 0.93 Ω. A standard

value of 1.5 Ωis selected for RC= R2 to provide additional ripple for stable switching at low VIN.

8.2.1.2.7 VCC and Bootstrap Capacitor

The VCC capacitor provides charge to bootstrap capacitor as well as internal circuitry and low side gate driver.

The bootstrap capacitor provides charge to high-side gate driver. The recommended value for CVCC =C7=1μF.

A good value for CBST = C1 = 0.01 μF.

8.2.1.2.8 Input Capacitor

Input capacitor should be large enough to limit the input voltage ripple which can be calculated using

Equation 17.

(17)

Choosing a ΔVIN = 0.5 V gives a minimum CIN = 0.34 μF. A standard value of 1 μF is selected CIN = C4. The

input capacitor should be rated for the maximum input voltage under all conditions. A 100 V X7R dielectric

should be selected for this design.

Input capacitor should be placed directly across VIN and RTN (pin 2 and 1) of the IC. If it is not possible to place

all of the input capacitor close to the IC, a 0.1-μF capacitor should be placed near the IC to provide a bypass

path for the high frequency component of the switching current.

8.2.1.2.9 UVLO Resistors

The UVLO resistors RUV1 and RUV2 set the UVLO threshold and hysteresis according to the relationship shown in

Equation 18 and Equation 19.

where

RUV2

VIN (UVLO,rising) = 1.225 V x RUV1 + 1

( )

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• IHYS = 20 μA (18)

(19)

Setting UVLO hysteresis of 2.5 V and UVLO rising threshold of 12 V results in RUV1 = 14.53 kΩand

RUV2 = 125 kΩ. Selecting standard values of RUV1 =R7=14kΩand RUV2 = R5 = 127 kΩresults in UVLO

threshold and hysteresis of 12.4 V and 2.5 V respectively.

8.2.1.3 Application Curves

Figure 14. Efficiency vs Load Current Figure 15. Frequency vs Input Voltage

Figure 16. Typical Switching Waveform (VIN = 48 V, IOUT = 200 mA)

VIN

BST

RON

RTN

VCC

UVLO

VIN

VOUT1

VOUT2

RFB1

RUV1

RON

COUT1

CBST

CIN

COUT2

RFB2

RUV2

LM5018

CVCC

20V-95V

Cac

CBYP

127 kΩ

8.25 kΩ

1 µF 0.1 µF

130 kΩ

0.01 µF

1 µF

0.1 µF

7.32 kΩ

1 kΩ

1 µF

1 nF

46.4 kΩ

47 µH

VOUT2 = VOUT1 xNP- VF

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8.2.2 Typical Isolated DC-DC Converter Using LM5018

An isolated supply using LM5018 is shown in Figure 17. Inductor (L) in a typical buck circuit is replaced with a

coupled inductor (X1). A diode (D1) is used to rectify the voltage on a secondary output. The nominal voltage at

the secondary output (VOUT2) is given by Equation 20.

where

• VFis the forward voltage drop of D1

• NPand NSare the number of turns on the primary and secondary of coupled inductor X1. (20)

For output voltage (VOUT1) more than one diode drop above the maximum VCC (8.55 V), the VCC pin can be diode

connected to VOUT1 for higher efficiency and low dissipation in the IC.

Figure 17. Isolated Fly-Buck™ Converter Using LM5018

8.2.2.1 Design Requirements

Table 4 lists the design parameters of this example.

Table 4. Buck Converter Design Specifications

DESIGN PARAMETERS VALUE

Input Range 20 V to 100 V

Primary Output Voltage 10 V

Secondary (Isolated) Output Voltage 9.5 V

Maximum Output Current (Primary + Secondary) 250 mA

Maximum Power Output 2.5 W

Nominal Switching Frequency 750 kHz

8.2.2.2 Detailed Design Procedure

8.2.2.2.1 Transformer Turns Ratio

The transformer turns ratio is selected based on the ratio of the primary output voltage to the secondary

(isolated) output voltage. In this design example, the two outputs are nearly equal and a 1:1 turns ratio

transformer is selected. Therefore, N2 / N1 = 1.

If the secondary (isolated) output voltage is significantly higher or lower than the primary output voltage, a turns

ratio less than or greater than 1 is recommended. The primary output voltage is normally selected based on the

input voltage range such that the duty cycle of the converter does not exceed 50% at the minimum input voltage.

This condition is satisfied if VOUT1 < VIN_MIN / 2.

'VOUT = 'IL1

x f x COUT1

IN(MAX) OUT OUT

L1 IN(MAX)W

V V V

L1 42.6 H

I V¦



u P

' u

L1 OUT1 OUT2 N2

I 0.39 A I I 2 0.28 A

§ ·

'   u u

¨ ¸

VOUT1

fSW = .x RON

x RFB1 = 7.16 k:

VOUT1

:RFB2 = 1.225 - 1)(

)

RFB2

VOUT1 = 1.225V x (RFB1

1+

OUT(MAX) OUT1 OUT2 N2

I I I 0.25 A

 u

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8.2.2.2.2 Total IOUT

The total primary referred load current is calculated by multiplying the isolated output load(s) by the turns ratio of

the transformer as shown in Equation 21.

(21)

8.2.2.2.3 RFB1, RFB2

The feedback resistors are selected to set the primary output voltage. The selected value for RFB1 is 1 kΩ. RFB2

can be calculated using the following equations to set VOUT1 to the specified value of 10 V. A standard resistor

value of 7.32 kΩis selected for RFB2.

(22)

(23)

8.2.2.2.4 Frequency Selection

Equation 1 is used to calculate the value of RON required to achieve the desired switching frequency.

where

• K = 9 × 10–11 (24)

For VOUT1 of 10 V and fSW of 750 kHz, the calculated value of RON is 148 kΩ. A lower value of 130 kΩis selected

for this design to allow for second order effects at high switching frequency that are not included in Equation 24.

8.2.2.2.5 Transformer Selection

A coupled inductor or a flyback-type transformer is required for this topology. Energy is transferred from primary

to secondary when the low-side synchronous switch of the buck converter is conducting.

The maximum inductor primary ripple current that can be tolerated without exceeding the buck switch peak

current limit threshold (0.39 A minimum) is given by Equation 25.

(25)

Using the maximum peak-to-peak inductor ripple current ΔIL1 from Equation 25, the minimum inductor value is

given by Equation 26.

(26)

A higher value of 47 µH is selected to insure the high-side switch current does not exceed the minimum peak

current limit threshold.

8.2.2.2.6 Primary Output Capacitor

In a conventional buck converter, the output ripple voltage is calculated as shown in Equation 27.

(27)

To limit the primary output ripple voltage ΔVOUT1 to approximately 50 mV, an output capacitor COUT1 of 0.93 µF is

required.

COUT2

'VOUT2 = IOUT2 x

TON (MAX)

IL2

IOUT2

TON(MAX) x IOUT2

IL2

IOUT2

TON(MAX) x IOUT2

IL1

TON(MAX) x IOUT2 x N2/N1

OUT2 ON(MAX)

OUT1 OUT1

I T

V 0.16 V

§ ·

u u

¨ ¸

' |

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Figure 18 shows the primary winding current waveform (IL1) of a Fly-Buck converter. The reflected secondary

winding current adds to the primary winding current during the buck switch off-time. Because of this increased

current, the output voltage ripple is not the same as in conventional buck converter. The output capacitor value

calculated in Equation 27 should be used as the starting point. Optimization of output capacitance over the entire

line and load range must be done experimentally. If the majority of the load current is drawn from the secondary

isolated output, a better approximation of the primary output voltage ripple is given by Equation 28.

(28)

Figure 18. Current Waveforms for COUT1 Ripple Calculation

A standard 1-µF, 25-V capacitor is selected for this design. If lower output voltage ripple is required, a higher

value should be selected for COUT1 and/or COUT2.

8.2.2.2.7 Secondary Output Capacitor

A simplified waveform for secondary output current (IOUT2) is shown in Figure 19.

Figure 19. Secondary Current Waveforms for COUT2 Ripple Calculation

The secondary output current (IOUT2) is sourced by COUT2 during on-time of the buck switch, TON. Ignoring the

current transition times in the secondary winding, the secondary output capacitor ripple voltage can be calculated

using Equation 29.

(29)

For a 1:1 transformer turns ratio, the primary and secondary voltage ripple equations are identical. Therefore,

COUT2 is chosen to be equal to COUT1 (1 µF) to achieve comparable ripple voltages on primary and secondary

outputs.

If lower output voltage ripple is required, a higher value should be selected for COUT1 and/or COUT2.

8.2.2.2.8 Type III Feedback Ripple Circuit

Type III ripple circuit as described in Ripple Configuration is required for the Fly-Buck topology. Type I and Type

II ripple circuits use series resistance and the triangular inductor ripple current to generate ripple at VOUT and the

FB pin. The primary ripple current of a Fly-Buck is the combination or primary and reflected secondary currents

as illustrated in Figure 18. In the Fly-Buck topology, Type I and Type II ripple circuits suffer from large jitter as the

reflected load current affects the feedback ripple.

OUT(MA

IN I

C4¦ 9u '

VD1 = VIN

Cr = 1000 pF

Cac = 0.1 PF

50 mV

RrCr d(VIN (MIN) - VOUT)x TON

GND

Cac

To FB

FB1

FB2

COUT

VOUT

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Figure 20. Type III Ripple Circuit

Selecting the Type III ripple components using the equations from Ripple Configuration will guarantee that the FB

pin ripple is be greater than the capacitive ripple from the primary output capacitor COUT1. The feedback ripple

component values are chosen as shown in Equation 30.

(30)

The calculated value for Rr is 66 kΩ. This value provides the minimum ripple for stable operation. A smaller

resistance should be selected to allow for variations in TON, COUT1 and other components. For this design, Rr

value of 46.4 kΩis selected.

8.2.2.2.9 Secondary Diode

The reverse voltage across secondary-rectifier diode D1 when the high-side buck switch is off can be calculated

using Equation 31.

(31)

For a VIN_MAX of 95 V and the 1:1 turns ratio of this design, a 100 V Schottky is selected.

8.2.2.2.10 VCC and Bootstrap Capacitor

A 1-µF capacitor of 16 V or higher rating is recommended for the VCC regulator bypass capacitor.

A good value for the BST pin bootstrap capacitor is 0.01-µF with a 16 V or higher rating.

8.2.2.2.11 Input Capacitor

The input capacitor is typically a combination of a smaller bypass capacitor located near the regulator IC and a

larger bulk capacitor. The total input capacitance should be large enough to limit the input voltage ripple to a

desired amplitude. For input ripple voltage ΔVIN, CIN can be calculated using Equation 32.

(32)

Choosing a ΔVIN of 0.5 V gives a minimum CIN of 0.167 μF. A standard value of 0.1 μF is selected for CBYP in this

design. A bulk capacitor of higher value reduces voltage spikes due to parasitic inductance between the power

source to the converter. A standard value of 1 μF is selected for CIN in this design. The voltage ratings of the two

input capacitors should be greater than the maximum input voltage under all conditions.

VIN (UVLO, rising) = 1.225V x RUV2 + 1)(RUV1

VIN (HYS) = IHYS x RUV2

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8.2.2.2.12 UVLO Resistors

UVLO resistors RUV1 and RUV2 set the undervoltage lockout threshold and hysteresis according to Equation 33

and Equation 34.

where

• IHYS = 20 μA, typical. (33)

(34)

For a UVLO hysteresis of 2.5 V and UVLO rising threshold of 20 V, Equation 33 and Equation 34 require RUV1 of

8.25 kΩand RUV2 of 127 kΩand these values are selected for this design example.

8.2.2.2.13 VCC Diode

Diode D2 is an optional diode connected between VOUT1 and the VCC regulator output pin. When VOUT1 is more

than one diode drop greater than the VCC voltage, the VCC bias current is supplied from VOUT1. This results in

reduced power losses in the internal VCC regulator which improves converter efficiency. VOUT1 must be set to a

voltage at least one diode drop higher than 8.55 V (the maximum VCC voltage) if D2 is used to supply bias

current.

8.2.2.3 Application Curves

Figure 21. Efficiency at 750 kHz, VOUT1 = 10 V Figure 22. Steady-State Waveform (VIN = 48 V, IOUT1 = 0

mA, IOUT2 = 100 mA)

Figure 23. Step Load Response (VIN = 48 V, IOUT1 = 0, Step Load on IOUT2 = 80 mA to 180 mA)

UVLO 3

RON 4

RTN 1

VIN 2

8 SW

7 BST

6 VCC

5 FB

PowerPAD

-8

CIN

CVCC

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9 Power Supply Recommendations

LM5018 is a power management device. The power supply for the device is any DC voltage source within the

specified input range.

10 Layout

10.1 Layout Guidelines

A proper layout is essential for optimum performance of the circuit. In particular, the following guidelines should

be observed:

1. CIN: The loop consisting of input capacitor (CIN), VIN pin, and RTN pin carries switching currents. Therefore,

the input capacitor should be placed close to the IC, directly across VIN and RTN pins and the connections to

these two pins should be direct to minimize the loop area. In general it is not possible to accommodate all of

input capacitance near the IC. A good practice is to use a 0.1-μF or 0.47-μF capacitor directly across the VIN

and RTN pins close to the IC, and the remaining bulk capacitor as close as possible (see Figure 24).

2. CVCC and CBST: The VCC and bootstrap (BST) bypass capacitors supply switching currents to the high and

low side gate drivers. These two capacitors should also be placed as close to the IC as possible, and the

connecting trace length and loop area should be minimized (see Figure 24).

3. The Feedback trace carries the output voltage information and a small ripple component that is necessary for

proper operation of LM5018. Therefore, care should be taken while routing the feedback trace to avoid

coupling any noise to this pin. In particular, feedback trace should not run close to magnetic components, or

parallel to any other switching trace.

4. SW trace: The SW node switches rapidly between VIN and GND every cycle and is therefore a possible

source of noise. The SW node area should be minimized. In particular, the SW node should not be

inadvertently connected to a copper plane or pour.

10.2 Layout Example

Figure 24. Placement of Bypass Capacitors

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11 Device and Documentation Support

11.1 Device Support

11.1.1 Development Support

11.1.1.1 Custom Design With WEBENCH® Tools

Click here to create a custom design using the LM5018 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.

11.2 Documentation Support

11.2.1 Related Documentation

•AN-2292 Designing an Isolated Buck (Flybuck) Converter (SNVA674)

•AN-1481 Controlling Output Ripple and Achieving ESR Independence in Constant On-Time (COT) Regulator

Designs (SNVA166)

•AN-2239 LM5018 Isolated Evaluation Board (SNVA667)

11.3 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.

11.4 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.

11.5 Trademarks

PowerPAD, Fly-Buck, E2E are trademarks of Texas Instruments.

WEBENCH is a registered trademark of Texas Instruments.

All other trademarks are the property of their respective owners.

11.6 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.

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11.7 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.

PACKAGE OPTION ADDENDUM

www.ti.com 28-Nov-2017

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead/Ball Finish

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LM5018MR/NOPB ACTIVE SO PowerPAD DDA 8 95 Green (RoHS

& no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 L5018

LM5018MRX/NOPB ACTIVE SO PowerPAD DDA 8 2500 Green (RoHS

& no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 L5018

LM5018SD/NOPB ACTIVE WSON NGU 8 1000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 L5018

LM5018SDX/NOPB ACTIVE WSON NGU 8 4500 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 L5018

(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 <=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. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish

value exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information

provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

PACKAGE OPTION ADDENDUM

www.ti.com 28-Nov-2017

Addendum-Page 2

continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.

TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device Package

Type Package

Drawing Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

(mm) B0

(mm) K0

(mm) P1

(mm) W

(mm) Pin1

Quadrant

LM5018MRX/NOPB SO

Power

PAD

DDA 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1

LM5018SD/NOPB WSON NGU 8 1000 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1

LM5018SDX/NOPB WSON NGU 8 4500 330.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1

PACKAGE MATERIALS INFORMATION

www.ti.com 28-Nov-2017

Pack Materials-Page 1

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

LM5018MRX/NOPB SO PowerPAD DDA 8 2500 367.0 367.0 35.0

LM5018SD/NOPB WSON NGU 8 1000 210.0 185.0 35.0

LM5018SDX/NOPB WSON NGU 8 4500 367.0 367.0 35.0

PACKAGE MATERIALS INFORMATION

www.ti.com 28-Nov-2017

Pack Materials-Page 2

www.ti.com

PACKAGE OUTLINE

6X 1.27

8X 0.51

0.31

3.81

TYP

0.25

0.10

0 - 8 0.15

0.00

2.71

2.11

3.4

2.8 0.25

GAGE PLANE

1.27

0.40

4214849/A 08/2016

PowerPAD SOIC - 1.7 mm max heightDDA0008B

PLASTIC SMALL OUTLINE

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.

PowerPAD is a trademark of Texas Instruments.

0.25 C A B

PIN 1 ID

AREA

NOTE 4

SEATING PLANE

0.1 C

SEE DETAIL A

DETAIL A

TYPICAL

SCALE 2.400

EXPOSED

THERMAL PAD

TYP

6.2

5.8

1.7 MAX

NOTE 3

5.0

4.8

B4.0

3.8

www.ti.com

EXAMPLE BOARD LAYOUT

(5.4)

(1.3) TYP

( ) TYP

VIA

0.2

(R ) TYP0.05

0.07 MAX

ALL AROUND 0.07 MIN

ALL AROUND

8X (1.55)

8X (0.6)

6X (1.27)

(2.95)

NOTE 9

(4.9)

NOTE 9

(2.71)

(3.4)

SOLDER MASK

OPENING

(1.3)

TYP

4214849/A 08/2016

PowerPAD SOIC - 1.7 mm max heightDDA0008B

PLASTIC SMALL OUTLINE

SYMM

SEE DETAILS

LAND PATTERN EXAMPLE

SCALE:10X

SOLDER MASK

OPENING

METAL COVERED

BY SOLDER MASK

SOLDER MASK

DEFINED PAD

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.

10. Vias are optional depending on application, refer to device data sheet. If any vias are implemented, refer to their locations shown

on this view. It is recommended that vias under paste be filled, plugged or tented.

METAL

SOLDER MASK

OPENING

NON SOLDER MASK

DEFINED

SOLDER MASK DETAILS

PADS 1-8

OPENING

SOLDER MASK METAL UNDER

SOLDER MASK

DEFINED

www.ti.com

EXAMPLE STENCIL DESIGN

(R ) TYP0.05

8X (1.55)

8X (0.6)

6X (1.27)

(5.4)

(2.71)

(3.4)

BASED ON

0.125 THICK

STENCIL

4214849/A 08/2016

PowerPAD SOIC - 1.7 mm max heightDDA0008B

PLASTIC SMALL OUTLINE

2.29 X 2.870.175 2.47 X 3.100.150 2.71 X 3.40 (SHOWN)0.125 3.03 X 3.800.1

SOLDER STENCIL

OPENING

STENCIL

THICKNESS

NOTES: (continued)

11. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate

design recommendations.

12. Board assembly site may have different recommendations for stencil design.

SOLDER PASTE EXAMPLE

EXPOSED PAD

100% PRINTED SOLDER COVERAGE BY AREA

SCALE:10X

SYMM

BASED ON

0.125 THICK

STENCIL

BY SOLDER MASK

METAL COVERED SEE TABLE FOR

DIFFERENT OPENINGS

FOR OTHER STENCIL

THICKNESSES

MECHANICAL DATA

NGU0008B

www.ti.com

SDC08B (Rev A)

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Mouser Electronics

Authorized Distributor

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LM5018MR/NOPB LM5018MRX/NOPB LM5018SD/NOPB LM5018SDX/NOPB