LM3475 - Hysteretic PFET Buck Controller

Datasheet	Packaging	Samples & Pricing	Eval. Boards	Reliability	Reference Designs	Application Notes	Knowledge Base

Features

•	Easy to use control methodology
•	0.8V to V_IN adjustable output range
•	High Efficiency (90% typical)
•	±0.9% (±1.5% over temp) feedback voltage
•	100% duty cycle capable
•	Maximum operating frequency up to 2MHz
•	Internal Soft-Start
•	Enable pin
•	SOT23-5 package

General Description

The LM3475 is a hysteretic P-FET buck controller designed to support a wide range of high efficiency applications in a very small SOT23-5 package. More...

Applications

•	TFT Monitor
•	Auto PC
•	Vehicle Security
•	Navigation Systems
•	Notebook Standby Supply
•	Battery Powered Portable Applications
•	Distributed Power Systems

Typical Application

click for larger image

Parameters Values

Output Current 5000 mA

Input Min Voltage 2.7 Volt

Input Max Voltage 10 Volt

Output Range 0.8V to Vin

Frequency Min 0 kHz

Frequency Max 1400 kHz

Feedback Voltage 0.8 Volt

Feedback Tolerance 1.5 %

Efficiency (peak) 90 %

Adj Switch Frequency No

Adjustable Output Yes

On/Off Pin Yes

Error Flag No

SoftStart Yes

Sync Pin No

Inverting No

Flyback No

Lossless Current Sense Yes

RegType Switching Controller

Temperature Min -40 deg C

Temperature Max 125 deg C

Channels 1 Channels

Special Features Fast transient response; High efficiency; Wide Vin range; 100% duty cycle capable

Topology Buck

PWM Mode Hysteretic

Step-Down Yes

Step-Up No

Output Max 1 Volt

Output Min 0.8 Volt

Typical Performance

click for larger image

Also Recommended

LM1770▲	Low-Voltage SOT-23 Synchronous Buck Controller
LM1771▲	Low-Voltage Synchronous Buck Controller With Precision Enable
LM2743▲	Sync Buck Controller - 2A To 25A Iout

Additional Resources

Application Notes

Block Diagram

click for larger image

Datasheet

RoHS Compliance Information	Size in Kbytes	Date
LM3475 Hysteretic PFET Buck Controller	777 Kbytes	7-Jan-05	Download

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Package Availability, Models, Samples & Pricing

Part Number

Package

Factory Lead Time

Models

Samples &
Electronic
Orders

Budgetary Pricing

Std
Pack
Size

Package
Marking
Format

Type

Pins

Spec.

MSL
Rating

Peak
Reflow

RoHS
Report

CAD
Symbols

Weeks

Qty

$US each

LM3475EVAL

Hysteretic PFET Buck Controller

Full production

N/A

$29.40

8 weeks

N/A

LM3475MF

SOT-23

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$0.52

reel
of
1000

S65B
XTT

6 weeks

2000

LM3475MFX

SOT-23

NOPB

260

RoHS

Download

Full production

N/A

1K+

$0.52

reel
of
3000

S65B
XTT

6 weeks

5000

General Description

The LM3475 is a hysteretic P-FET buck controller designed to support a wide range of high efficiency applications in a very small SOT23-5 package. The hysteretic control scheme has several advantages, including simple system design with no external compensation, stable operation with a wide range of components, and extremely fast transient response. Hysteretic control also provides high efficiency operation, even at light loads. The PFET architecture allows for low component count as well as 100% duty cycle and ultra-low dropout operation.

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM3475MF	ABCD150	0	34175	0	0	4234000	1	1201409060
LM3475MFX	ABCD150	0	34175	0	0	4234000	1	1201409060

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

For more information on Reliability Metrics, please click here.

Reference Designs

•	LM3475 Reference Design - Buck Dual Output Converter: 5V Input, 3.3V @ 2A, 2.5V @ 2A

Application Notes

Title	Size in Kbytes	Date
AN-1381: Application Note 1381 LM3475 Evaluation Board	457 Kbytes	4-May-05	Download

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More Application Notes

Title	Size in Kbytes	Date
AN-1204: Application Note 1204 LM3478/LM3488 Evaluation Board	218 Kbytes	10-May-04	Download
AN-1149: Application Note 1149 Layout Guidelines for Switching Power Supplies	248 Kbytes	1-May-04	Download
AN-1149 (Japanese): Application Note 1149 Layout Guidelines for Switching Power Supplies	90 Kbytes
AN-1193: Application Note 1193 LM3477 Evaluation Board	248 Kbytes	10-May-04	Download
AN-1286: Application Note 1286 Compensation For The LM3478 Boost Controller	204 Kbytes	19-May-09	Download
AN-1286 (Japanese): Application Note 1286 Compensation For The LM3478 Boost Controller	202 Kbytes
AN-1286 (Chinese): Application Note 1286 Compensation For The LM3478 Boost Controller	368 Kbytes
AN-1484: Application Note 1484 Designing A SEPIC Converter	196 Kbytes	30-Apr-08	Download
AN-1484 (Japanese): Application Note 1484 Designing A SEPIC Converter	175 Kbytes
AN-1484 (Chinese): Application Note 1484 Designing A SEPIC Converter	338 Kbytes

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[Information as of 8-Nov-2009]