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LM5085

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4.5-75V Wide Vin, Constant On-Time Non-Synchronous PFET Buck Controller

Data sheet
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4.5-75V Wide Vin, Constant On-Time Non-Synchronous PFET Buck Controller

LM5085

ACTIVE
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Product details

Parameters

Vin (Min) (V) 4.5 Vin (Max) (V) 75 Vout (Min) (V) 1.25 Vout (Max) (V) 75 Iout (Max) (A) 10 Iq (Typ) (uA) 1300 Switching frequency (Min) (kHz) 50 Switching frequency (Max) (kHz) 1000 Features Adjustable Current Limit, Enable, Frequency Synchronization Operating temperature range (C) -40 to 125 Regulated outputs (#) 1 Number of Phases 1 Rating Catalog open-in-new Find other Buck controllers (external switch)

Package | Pins | Size

HVSSOP (DGN) 8 9 mm² 3 x 3 VSSOP (DGK) 8 15 mm² 3 x 4.9 WSON (NGQ) 8 9 mm² 3 x 3 open-in-new Find other Buck controllers (external switch)

Features

  • LM5085-Q1 is an Automotive Grade Product that
    is AEC-Q100 Grade 1 Qualified (–40°C to 125°C
    Operating Junction Temperature)
  • Wide 4.5-V to 75-V Input Voltage Range
  • Adjustable Current Limit Using RDS(ON) or a
    Current Sense Resistor
  • Programmable Switching Frequency to 1MHz
  • No Loop Compensation Required
  • Ultra-Fast Transient Response
  • Nearly Constant Operating Frequency with Line
    and Load Variations
  • Adjustable Output Voltage from 1.25 V
  • Precision ±2% Feedback Reference
  • Capable of 100% Duty Cycle Operation
  • Internal Soft-start Timer
  • Integrated High Voltage Bias Regulator
  • Thermal Shutdown
  • Package:
    • HVSSOP-8
    • VSSOP-8
    • WSON-8
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Description

The LM5085 is a high efficiency PFET switching regulator controller that can be used to quickly and easily develop a small, efficient buck regulator for a wide range of applications. This high voltage controller contains a PFET gate driver and a high voltage bias regulator which operates over a wide 4.5-V to 75-V input range. The constant on-time regulation principle requires no loop compensation, simplifies circuit implementation, and results in ultrafast load transient response. The operating frequency remains nearly constant with line and load variations due to the inverse relationship between the input voltage and the on-time. The PFET architecture allows 100% duty cycle operation for a low dropout voltage. Either the RDS(ON) of the PFET or an external sense resistor can be used to sense current for over-current detection.

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Technical documentation

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Type Title Date
* Datasheet LM5085/-Q1 75-V Constant On-Time PFET Buck Switching Controller datasheet (Rev. I) Aug. 12, 2015
Technical article Crafty idea: Create a 150V non synchronous buck solution with a lower Vin rated controller Aug. 25, 2017
Application note Reduce buck-converter EMI and voltage stress by minimizing inductive parasitics Jul. 21, 2016
Technical article How to design for EMC and isolation with Fly-Buck™ converters Jul. 28, 2015
Application note Transient Response versus Ripple – An Analysis of Ripple Injection Techniques Apr. 28, 2014
Technical article How to dynamically control the output voltage with a COT regulator Dec. 19, 2013
Technical article Eight switching circuits to power wide VIN applications - brought to you by Vijay Choudhary and presented by Santa’s reindeer Dec. 18, 2013
White paper Wide VIN power management ICs simplify white paper (Rev. A) Sep. 19, 2013
User guide AN-1878 LM5085 Evaluation Board (Rev. B) Apr. 30, 2013
Application note Constant Current Constant Voltage Buck Converter w/LM25085 (Rev. A) Apr. 23, 2013
Application note Designing Non-Invert Buck-Boost (Zeta) Cnvrts w/a Buck P-FET Cntrl Apr. 22, 2011

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Hardware development

EVALUATION BOARD Download
document-generic User guide
75
Description

The LM5085 evaluation board provides the design engineer with a fully functional buck regulator, employing the LM5085 PFET switching controller which uses the constant on-time (COT) operating principle. The evaluation board provides a 5V output over an input range of 5.5V to 55V. The circuit (...)

Features
  • Input Voltage: 5.5V to 55V, 60V maximum
  • Output Voltage: 5V
  • Maximum load current: 4.5A for VIN >8V
  • Minimum load current: 0A
  • Current Limit Threshold: ≅7.6A
  • Measured Efficiency: 97.2% (VIN 5.5V, IOUT = 0.6Amps)
  • Nominal Switching Frequency: 300 kHz
  • Size: 3.1 in. x 1.5 in. x 0.78 in

 

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Design tools & simulation

SIMULATION MODEL Download
SNVM213A.ZIP (135 KB) - PSpice Model
SIMULATION MODEL Download
SNVM213B.ZIP (147 KB) - PSpice Model
SIMULATION MODEL Download
SNVM496A.TSC (135 KB) - TINA-TI Reference Design
SIMULATION MODEL Download
SNVM497A.TSC (136 KB) - TINA-TI Reference Design
SIMULATION MODEL Download
SNVM498A.ZIP (20 KB) - TINA-TI Spice Model
SIMULATION MODEL Download
SNVM955.ZIP (3 KB) - PSpice Model
SIMULATION TOOL Download
PSpice® for TI design and simulation tool
PSPICE-FOR-TI — PSpice® for TI is a design and simulation environment that helps evaluate functionality of analog circuits. This full-featured, design and simulation suite uses an analog analysis engine from Cadence®. Available at no cost, PSpice for TI includes one of the largest model libraries in the (...)
Features
  • Leverages Cadence PSpice Technology
  • Preinstalled library with a suite of digital models to enable worst-case timing analysis
  • Dynamic updates ensure you have access to most current device models
  • Optimized for simulation speed without loss of accuracy
  • Supports simultaneous analysis of multiple products
  • (...)
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CALCULATION TOOL Download
LM(2)5085 Quick Start Calculator
LM25085-5085QUICK-CALC

Reference designs

REFERENCE DESIGNS Download
Low Cost Buck Provides 24V@2A from 32Vin for Wireless Base Station Reference Design
PMP9103 — This hysteretic buck converter delivers greater than 97% efficiency, low cost and small area. Additional benefits are very low output ripple voltage and excellent load transient response.
REFERENCE DESIGNS Download
Non-Isolated Buck Converter (13.5V@15A)
PMP7821 — This is a non-synchronous buck converter design that has an input voltage range of 18V-to-32Vin max and provides a regulated output of 13.5Vout@15A.
REFERENCE DESIGNS Download
15V – 50V input to 12V@5A, Non Sync Buck
PMP7767 — It is a non synchronous buck controller. It uses a constant on time (COT) device i.e. LM5085. This circuit has ceramic output capacitors which have very low ESR. Therefore the ripple is generated using the DCR of the inductor. The ripple voltage is then superimposed onto the feedback voltage.
Design files
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CAD/CAE symbols

Package Pins Download
HVSSOP (DGN) 8 View options
VSSOP (DGK) 8 View options
WSON (NGQ) 8 View options

Ordering & quality

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