LM1770   
Low-Voltage SOT23 Synchronous Buck Controller With No External Compensation from the PowerWise® Family		 Click link to Download

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

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.

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



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                                              LM1770
Drag-Select for Table Reset Graph
Also Recommended
LM1771▲With Precision Enable
LM2853▲3A Integrated FETs PWM Version

Typical Application
click for larger image


Block Diagram
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Typical Performance
*click for larger image


Paramaters / ValuesLM1770 LM1771 LM2853
Output Current4000 mA 6000 mA 3000 mA
Input Min Voltage2.8 Volt 2.8 Volt 3 Volt
Input Max Voltage5.5 Volt 5.5 Volt 5.5 Volt
Feedback Voltage0.8 Volt 0.8 Volt Undefined Volt
Feedback Tolerance2 % 2 %
Frequency Min300 kHz 300 kHz 550 kHz
Frequency Max1000 kHz 1000 kHz 550 kHz
Efficiency (peak)95 % 95 % 95 %
Output Range0.8V to 4.5V 0.8V to 4.5V 1.8, 1, 2.5, 1.2, 0.8, 3.3, 3, 1.5
Adj Switch FrequencyNo No No
Adjustable OutputYes Yes No
Synchronous RectificationYes Yes Yes
On/Off PinNo Yes Yes
Error FlagNo No No
SoftStartYes Yes Yes
Sync PinNo No No
InvertingYes No No
FlybackNo No No
Lossless Current SenseNo No
RegTypeSwitching Controller Switching Controller Switching Regulator
Temperature Min-40 deg C -40 deg C -40 deg C
Temperature Max125 deg C 125 deg C 125 deg C
Channels1 Channels 1 Channels
Special FeaturesNo compensation required Precision enable for sequencing multiple rails Internal compensation, low standby current
TopologyBuck Buck Synchronous Buck
PWM ModeConstant on-time Constant on-time Voltage
Step-DownNo Yes Yes
Step-UpNo No
Output Max4.5 Volt 4.5 Volt 1.8, 1, 2.5, 1.2, 0.8, 3.3, 3, 1.5 Volt
Output Min0.8 Volt 0.8 Volt 1.8, 1, 2.5, 1.2, 0.8, 3.3, 3, 1.5 Volt
PowerWiseYes Yes Yes

Datasheet
TitleSizeDateOther
Language
LM1770 Low-Voltage SOT23 Synchronous Buck Controller With No External Compensation687
Kbytes		20-Jul-06日本語


Featured Application Notes
TitleSizeDateOther
Language
AN-1400: Application Note 1400 LM1770 Evaluation Board528
Kbytes		30-Sep-05 中文
AN-1414: Application Note 1414 LM1770 Design Reference750
Kbytes		8-Nov-05 中文
AN-1677: Application Note 1677 LM1771 and LM3880 Based FPGA Power Supply Reference Design177
Kbytes		14-Jan-08 


More Application Notes
TitleSizeDateOther
Language
AN-1477: Application Note 1477 LM1771 Evaluation Board573
Kbytes		11-Jul-06 中文

Part Number(s)
(NSID)		Top ViewAvailabilityCurrent Reported StockBudgetary PricingStandard Pack Size
LM1770SMF/NOPB
LM1770SMF

RoHS



SOT-23		Full production
Lead Time: 6 weeks

Samples
DistributorRegionQty
DIGIKEYWorldwide2638
FARNELLEurope and Asia718
FUTUREWorldwide1100
RS COMPONENTSWorldwide75
$0.80 each at 1K+ pcsreel
of
1000
LM1770TMF/NOPB
LM1770TMF

RoHS



SOT-23		Full production
Lead Time: 6 weeks

Samples
DistributorRegionQty
AVNET-EMWorldwide1000
DIGIKEYWorldwide1086
FARNELLEurope and Asia963
RS COMPONENTSWorldwide75
$0.80 each at 1K+ pcsreel
of
1000
LM1770UMF/NOPB
LM1770UMF

RoHS



SOT-23		Full production
Lead Time: 6 weeks

Samples
DistributorRegionQty
AVNET-EMWorldwide1000
DIGIKEYWorldwide2068
FARNELLEurope and Asia848
RS COMPONENTSWorldwide70
$0.80 each at 1K+ pcsreel
of
1000
LM1770SMFX/NOPB
LM1770SMFX

RoHS



SOT-23		Full production
Lead Time: 6 weeks

 
DistributorRegionQty
DIGIKEYWorldwide0
$0.80 each at 1K+ pcsreel
of
3000
LM1770TMFX/NOPB
LM1770TMFX

RoHS



SOT-23		Full production
Lead Time: 6 weeks

 
DistributorRegionQty
DIGIKEYWorldwide0
$0.80 each at 1K+ pcsreel
of
3000
LM1770UMFX/NOPB
LM1770UMFX

RoHS



SOT-23		Full production
Lead Time: 6 weeks

 
DistributorRegionQty
DIGIKEYWorldwide0
$0.80 each at 1K+ pcsreel
of
3000

Part Number(s)
(NSID)		DescriptionAvailabilityCurrent Reported StockBudgetary PricingStandard Pack Size
LM1770EVAL
Low-Voltage SOT23 Synchronous Buck Controller With No External CompensationFull production
Lead Free (RoHS)

 
DistributorRegionQty
DIGIKEYWorldwide0
NATIONALWorldwide76
$28.00 each1

Desscription:

LM1770 SOT-23 Synchronous Buck Controller

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 400mA
  • Internal soft-start
  • Short circuit protection
  • Tiny SOT-23 package

Contents:

  • A fully assembled LM1770 evaluation board
  • LM1770 datasheet
  • LM1770 evaluation board appnote

Part Number(s)
(NSID)		Top ViewTypePinsMSL RatingPeak ReflowRoHSCAD SymbolsModelsPackage
Marking
Format
LM1770SMF/NOPB
LM1770SMF
SOT-2351
1		260
260		RoHSDownloadN/A
SKJB
XTT
LM1770TMF/NOPB
LM1770TMF
SOT-2351
1		260
260		RoHSDownloadN/A
SKKB
XTT
LM1770UMF/NOPB
LM1770UMF
SOT-2351
1		260
260		RoHSDownloadN/A
SKLB
XTT
LM1770SMFX/NOPB
LM1770SMFX
SOT-2351
1		260
260		RoHSDownloadN/A
SKJB
XTT
LM1770TMFX/NOPB
LM1770TMFX
SOT-2351
1		260
260		RoHSDownloadN/A
SKKB
XTT
LM1770UMFX/NOPB
LM1770UMFX
SOT-2351
1		260
260		RoHSDownloadN/A
SKLB
XTT

Reliability Metrics
Part Number Process EFR Reject EFR Sample Size PPM LTA Rejects LTA Device Hours FITS MTTF (Hours)
LM1770SMFCS065238968520440200011249079519
LM1770SMFXCS065238968520440200011249079519
LM1770TMFCS065238968520440200011249079519
LM1770TMFXCS065238968520440200011249079519
LM1770UMFCS065238968520440200011249079519
LM1770UMFXCS065238968520440200011249079519

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.


[Information as of 21-Nov-2009]