LM1771 - Low-Voltage Synchronous Buck Controller with Precision Enable and No External Compensation

LM1771 - Low-Voltage Synchronous Buck Controller with Precision Enable and No External Compensation from the PowerWise® Family

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

Features

•	Input voltage range of 2.8V to 5.5V
•	0.8V reference voltage
•	Precision enable
•	No compensation required
•	Constant frequency across input range
•	Low quiescent current of 400 µA
•	Internal soft-start
•	Short circuit protection
•	Tiny LLP-6 package and MSOP-8 package

General Description

The LM1771 is an efficient synchronous buck switching controller with a precision enable requiring no external compensation. More...

Applications

•	Simple To Design, High Efficiency Step Down Switching Regulators
•	FPGAs, DSPs, and ASIC Power Supplies
•	Set-Top Boxes
•	Cable Modems
•	Printers
•	Digital Video Recorders
•	Servers
•	Graphic Cards

Typical Application

*click for larger image

Parametric Table expand

Parametric Table collapse

Output Current 6000 mA

Input Min Voltage 2.8 Volt

Input Max Voltage 5.5 Volt

Feedback Voltage 0.8 Volt

Feedback Tolerance 2 %

Frequency Min 300 kHz

Frequency Max 1000 kHz

Efficiency (peak) 95 %

Output Current 6000 mA

Input Min Voltage 2.8 Volt

Input Max Voltage 5.5 Volt

Feedback Voltage 0.8 Volt

Feedback Tolerance 2 %

Frequency Min 300 kHz

Frequency Max 1000 kHz

Efficiency (peak) 95 %

Output Range 0.8V to 4.5V

Adj Switch Frequency No

Adjustable Output Yes

Synchronous Rectification Yes

On/Off Pin Yes

Error Flag No

SoftStart Yes

Sync Pin No

Inverting No

Flyback No

Lossless Current Sense No

RegType Switching Controller

Temperature Min -40 deg C

Temperature Max 125 deg C

Channels 1 Channels

Special Features Precision enable for sequencing multiple rails

Topology Buck

PWM Mode Constant on-time

Step-Down Yes

Step-Up No

Output Power Undefined Watt

Output Max 4.5 Volt

Output Min 0.8 Volt

PowerWise Yes

View Using Catalog

Typical Performance

*click for larger image

Also Recommended

LM1770	SOT23 Package
LM2853	3A Integrated FETs PWM Version

Additional Resources

Application Notes (see below)

Block Diagram

*click for larger image

Datasheet

RoHS Compliance Information	Size in Kbytes	Date
LM1771 Low-Voltage Synchronous Buck Controller with Precision Enable and No External Compensation	772 Kbytes	13-Oct-06	Download
LM1771 Low-Voltage Synchronous Buck Controller with Precision Enable and No External Compensation (Japanese)	540 Kbytes

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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

Qty

Qty

$US each

LM1771EVAL

Low-Voltage Synchronous Buck Controller with Precision Enable and No External Compensation

Full production

N/A

Buy Now

1+

$38.00

1

8 weeks

N/A

LM1771SMM

8

NOPB

1

260

Full production

N/A

Samples

Buy Now

1K+

$0.85

reel
of
1000

22 weeks

500

LM1771TMM

8

NOPB

1

260

Full production

N/A

Samples

Buy Now

1K+

$0.85

reel
of
1000

22 weeks

2000

LM1771UMM

8

NOPB

1

260

Full production

N/A

Samples

Buy Now

1K+

$0.85

reel
of
1000

22 weeks

1000

LM1771SMMX

8

NOPB

1

260

Full production

N/A

Buy Now

1K+

$0.85

reel
of
3500

6 weeks

N/A

LM1771TMMX

8

NOPB

1

260

Full production

N/A

Buy Now

1K+

$0.85

reel
of
3500

22 weeks

15000

LM1771UMMX

8

NOPB

1

260

Full production

N/A

Buy Now

1K+

$0.85

reel
of
3500

16 weeks

N/A

LM1771SSD

6

NOPB

1

260

Full production

N/A

Samples

Buy Now

1K+

$0.85

reel
of
1000

22 weeks

40000

LM1771TSD

6

NOPB

1

260

Full production

N/A

Samples

Buy Now

1K+

$0.85

reel
of
1000

22 weeks

2000

LM1771USD

6

NOPB

1

260

Full production

N/A

Samples

Buy Now

1K+

$0.85

reel
of
1000

22 weeks

40000

LM1771SSDX

6

NOPB

1

260

Full production

N/A

Buy Now

1K+

$0.85

reel
of
4500

22 weeks

N/A

LM1771TSDX

6

NOPB

1

260

Full production

N/A

Buy Now

1K+

$0.85

reel
of
4500

22 weeks

N/A

LM1771USDX

6

NOPB

1

260

Full production

N/A

Buy Now

1K+

$0.85

reel
of
4500

22 weeks

N/A

General Description

The LM1771 is an efficient synchronous buck switching controller with a precision enable requiring no external compensation. The constant on-time control scheme provides a simple design free of compensation components, allowing minimal component count and board space. The precision enable pin allows flexibility in sequencing multiple rails and setting UVLO. The LM1771 also incorporates a unique input feed-forward to maintain a constant frequency independent of the input voltage. The LM1771 is optimized for a low voltage input range of 2.8V to 5.5V and can provide an adjustable output as low as 0.8V. Driving an external high side PFET and low side NFET it can provide efficiencies as high as 95%.

Three versions of the LM1771 are available depending on the switching frequency desired for the application. Nominal switching frequencies are in the range of 100kHz to 1000kHz.

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM1771SMM	CS065	2	34108	59	0	3862000	1	1095853045
LM1771SMMX	CS065	2	34108	59	0	3862000	1	1095853045
LM1771SSD	CS065	2	34108	59	0	3862000	1	1095853045
LM1771SSDX	CS065	2	34108	59	0	3862000	1	1095853045
LM1771TMM	CS065	2	34108	59	0	3862000	1	1095853045
LM1771TMMX	CS065	2	34108	59	0	3862000	1	1095853045
LM1771TSD	CS065	2	34108	59	0	3862000	1	1095853045
LM1771TSDX	CS065	2	34108	59	0	3862000	1	1095853045
LM1771UMM	CS065	2	34108	59	0	3862000	1	1095853045
LM1771UMMX	CS065	2	34108	59	0	3862000	1	1095853045
LM1771USD	CS065	2	34108	59	0	3862000	1	1095853045
LM1771USDX	CS065	2	34108	59	0	3862000	1	1095853045

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.

Application Notes

Title	Size in Kbytes	Date
AN-1477: Application Note 1477 LM1771 Evaluation Board	573 Kbytes	11-Jul-06	Download
AN-1477 (Chinese): Application Note 1477 LM1771 Evaluation Board	218 Kbytes
AN-1677: Application Note 1677 LM1771 and LM3880 Based FPGA Power Supply Reference Design	177 Kbytes	14-Jan-08	Download

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More Application Notes

Title	Size in Kbytes	Date
AN-1400: Application Note 1400 LM1770 Evaluation Board	528 Kbytes	30-Sep-05	Download
AN-1400 (Chinese): Application Note 1400 LM1770 Evaluation Board	207 Kbytes
AN-1414: Application Note 1414 LM1770 Design Reference	750 Kbytes	8-Nov-05	Download
AN-1414 (Chinese): Application Note 1414 LM1770 Design Reference	471 Kbytes

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[Information as of 3-Jul-2009]