LM1770 - Low-Voltage SOT23 Synchronous Buck Controller With No External Compensation

LM1770 - Low-Voltage SOT23 Synchronous Buck Controller With 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
•	No compensation required
•	Constant frequency across input range
•	Low quiescent current of 400µA
•	Internal soft-start
•	Short circuit protection
•	Tiny SOT-23 package

General Description

The LM1770 is an efficient synchronous buck switching controller in a tiny SOT23 package. More...

Applications

•	Simple To Design, High Efficiency Step Down Switching Regulators
•	Set-Top Boxes
•	Cable Modems
•	Printers
•	Digital Video Recorders
•	Servers

Typical Application

click for larger image

Parameters Values

Output Current 4000 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 No

Error Flag No

SoftStart Yes

Sync Pin No

Inverting Yes

Flyback No

Lossless Current Sense No

RegType Switching Controller

Temperature Min -40 deg C

Temperature Max 125 deg C

Channels 1 Channels

Special Features No compensation required

Topology Buck

PWM Mode Constant on-time

Step-Down No

Step-Up No

Output Max 4.5 Volt

Output Min 0.8 Volt

PowerWise Yes

Typical Performance

*click for larger image

WEBENCH Live Simulation!

WEBENCH® Designer

LM1770T
2.80 <=	V in Lower V	<=	V in Upper V	<= 5.50
V out	0.80 <=		V	<= 1.80
I out			A	<= 4.00
Ambient Temperature			°C	<= 100
What are WEBENCH® tools?

Also Recommended

LM1771▲	With Precision Enable
LM2853▲	3A Integrated FETs PWM Version

Additional Resources

Online Seminars

Powering FPGAs: Design Considerations, IC Solutions and Tools

Application Notes

Block Diagram

click for larger image

Datasheet

RoHS Compliance Information	Size in Kbytes	Date
LM1770 Low-Voltage SOT23 Synchronous Buck Controller With No External Compensation	687 Kbytes	20-Jul-06	Download
LM1770 Low-Voltage SOT23 Synchronous Buck Controller With No External Compensation (Japanese)	404 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

Weeks

Qty

$US each

LM1770EVAL

Low-Voltage SOT23 Synchronous Buck Controller With No External Compensation

Full production

N/A

$28.00

8 weeks

N/A

LM1770SMF

SOT-23

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$0.80

reel
of
1000

SKJB
XTT

6 weeks

2000

LM1770TMF

SOT-23

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$0.80

reel
of
1000

SKKB
XTT

6 weeks

2000

LM1770UMF

SOT-23

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$0.80

reel
of
1000

SKLB
XTT

6 weeks

500

LM1770SMFX

SOT-23

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$0.80

reel
of
3000

SKJB
XTT

6 weeks

N/A

LM1770TMFX

SOT-23

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$0.80

reel
of
3000

SKKB
XTT

6 weeks

7500

LM1770UMFX

SOT-23

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$0.80

reel
of
3000

SKLB
XTT

6 weeks

7500

General Description

The LM1770 is an efficient synchronous buck switching controller in a tiny SOT23 package. The constant on-time control scheme provides a simple design free of compensation components, allowing minimal component count and board space. It also incorporates a unique input feed-forward to maintain a constant frequency independent of the input voltage. The LM1770 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 LM1770 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 Device Hours	FITS	MTTF (Hours)
LM1770SMF	CS065	2	38968	52	4402000	1	1249079519
LM1770SMFX	CS065	2	38968	52	4402000	1	1249079519
LM1770TMF	CS065	2	38968	52	4402000	1	1249079519
LM1770TMFX	CS065	2	38968	52	4402000	1	1249079519
LM1770UMF	CS065	2	38968	52	4402000	1	1249079519
LM1770UMFX	CS065	2	38968	52	4402000	1	1249079519

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-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
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-1477: Application Note 1477 LM1771 Evaluation Board	573 Kbytes	11-Jul-06	Download
AN-1477 (Chinese): Application Note 1477 LM1771 Evaluation Board	218 Kbytes

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[Information as of 7-Nov-2009]