LM3485   
Hysteretic PFET Buck Controller 		Click link to Download

Features
•Easy to use control methodology
•No control loop compensation required
•4.5V to 35V wide input range
•1.242V to VIN adjustable output range
•High Efficiency 93%
•±1.3% (±2% over temp) internal reference
•100% duty cycle
•Maximum operating frequency > 1MHz
•Current limit protection
•MSOP-8

Description

The LM3485 is a high efficiency PFET switching regulator controller that can be used to quickly and easily develop a small, low cost, switching buck regulator for a wide range of applications. The hysteretic control architecture provides for simple design without any control loop stability concerns using a wide variety of external components. The PFET architecture also allows for low component count as well as ultra-low dropout, 100% duty cycle operation. Another benefit is high efficiency operation at light loads without an increase in output ripple.

Current limit protection is provided by measuring the voltage across the PFET’s RDS(ON), thus eliminating the need for a sense resistor. The cycle-by-cycle current limit can be adjusted with a single resistor, ensuring safe operation over a range of output currents.

Applications
•Set-Top Box
•DSL/Cable Modem
•PC/IA
•Auto PC
•TFT Monitor
•Battery Powered Portable Applications
•Distributed Power Systems
•Always On Power
WEBENCH Power Designer My Designs

LM3485
 
4.50 <=		 V in Lower
 V		  
<=		 V in Upper
 V		  
<= 35.00
V out 1.24 <=  V <= 35.00
I out    A <= 4.00
Ambient Temperature  °C <= 100


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Also Recommended
LM1770▲Low-Voltage SOT-23 Synchronous Buck Controller
LM1771▲Low-Voltage Sync. Buck Controller With Precision Enable
LM25085▲Higher Efficiency, Higher Frequency With Less Variation
LM3475▲Low Voltage SOT-23 Version With Sub-Bandgap Output
LM3477▲N-FET PWM Buck Controller
LM3489▲Hysteretic PFET Buck Controller (LM3485) With Enable Pin



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                                              LM3485
Drag-Select for Table Reset Graph
Also Recommended
LM1770▲Low-Voltage SOT-23 Synchronous Buck Controller
LM1771▲Low-Voltage Sync. Buck Controller With Precision Enable
LM25085▲Higher Efficiency, Higher Frequency With Less Variation
LM3475▲Low Voltage SOT-23 Version With Sub-Bandgap Output
LM3477▲N-FET PWM Buck Controller
LM3489▲Hysteretic PFET Buck Controller (LM3485) With Enable Pin

Typical Application
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Block Diagram
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Typical Performance
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Paramaters / ValuesLM3485 LM1770 LM1771 LM25085 LM3475 LM3477 LM3489
Input Min Voltage4.5 Volt 2.8 Volt 2.8 Volt 4.5 Volt 2.7 Volt 2.95 Volt 4.5 Volt
Input Max Voltage35 Volt 5.5 Volt 5.5 Volt 42 Volt 10 Volt 35 Volt 35 Volt
Output Range1.242V to Vin 0.8V to 4.5V 0.8V to 4.5V 1.25V to VIN 0.8V to Vin 1.265V min 1.239V min.
Frequency Min0 kHz 300 kHz 300 kHz 0 kHz 500 kHz 0 kHz
Frequency Max1400 kHz 1000 kHz 1000 kHz 1000 kHz 1400 kHz 500 kHz 1400 kHz
Feedback Voltage1.27 Volt 0.8 Volt 0.8 Volt 1.25 Volt 0.8 Volt 1.265 Volt 1.239 Volt
Efficiency (peak)93 % 95 % 95 % 95 % 90 %
Sync PinNo No No No No No No
Adj Switch FrequencyYes No No Yes No No Yes
Frequency Min0 kHz 300 kHz 300 kHz 0 kHz 500 kHz 0 kHz
Adjustable OutputYes Yes Yes Yes Yes Yes Yes
Error FlagNo No No No No No No
Special FeaturesNo compensation required; Current limit; PFET controller No compensation required Precision enable for sequencing multiple rails Near constant switching frequency, PFET for 100% duty cycle Fast transient response; High efficiency; Wide Vin range; 100% duty cycle capable Hysteretic threshold at 36% of programmed current limit; Vout OVP No compensation required; Current limit; PFET controller; Enable; Power-saving shutdown mode
On/Off PinNo No Yes Yes Yes Yes Yes
Error FlagNo No No No No No No
SoftStartNo Yes Yes Yes Yes Yes No
Sync PinNo No No No No No No
InvertingNo Yes No Yes No Yes No
FlybackNo No No No No No No
RegTypeSwitching Controller Switching Controller Switching Controller Switching Controller Switching Controller Switching Controller Switching Controller
Temperature Min-40 deg C -40 deg C -40 deg C -40 deg C -40 deg C -40 deg C -40 deg C
Temperature Max125 deg C 125 deg C 125 deg C 125 deg C 125 deg C 125 deg C 125 deg C
PWM ModeHysteretic Constant on-time Constant on-time Constant On-Time (COT) Hysteretic Current Hysteretic
TopologyBuck Buck Buck Buck Buck Buck Buck
Step-Up1, No No No No No No
InvertingNo Yes No Yes No Yes No
FlybackNo No No No No No No
RegTypeSwitching Controller Switching Controller Switching Controller Switching Controller Switching Controller Switching Controller Switching Controller
Adjustable OutputYes Yes Yes Yes Yes Yes Yes
Special FeaturesNo compensation required; Current limit; PFET controller No compensation required Precision enable for sequencing multiple rails Near constant switching frequency, PFET for 100% duty cycle Fast transient response; High efficiency; Wide Vin range; 100% duty cycle capable Hysteretic threshold at 36% of programmed current limit; Vout OVP No compensation required; Current limit; PFET controller; Enable; Power-saving shutdown mode
TopologyBuck Buck Buck Buck Buck Buck Buck
PWM ModeHysteretic Constant on-time Constant on-time Constant On-Time (COT) Hysteretic Current Hysteretic
Step-Up1, No No No No No No
Temperature Max125 deg C 125 deg C 125 deg C 125 deg C 125 deg C 125 deg C 125 deg C
Output Min1.242 Volt 0.8 Volt 0.8 Volt 1.25 Volt 0.8 Volt 1.265 Volt 1.239 Volt
AEC Q-100 Automotive Grade1 1
AutomotiveYes No Yes
AutomotiveYes No Yes

Datasheet
TitleSizeDateOther
Language
LM3485 Hysteretic PFET Buck Controller411
Kbytes		29-Sep-09日本語


Featured Application Notes
TitleSizeDateOther
Language
AN-1227: Application Note 1227 LM3485 Evaluation Board86
Kbytes		10-May-04 
AN-1392: Application Note 1392 LM3485 LED Demo Board569
Kbytes		7-Jun-06 中文


More Application Notes
TitleSizeDateOther
Language
AN-1204: Application Note 1204 LM3478/LM3488 Evaluation Board218
Kbytes		10-May-04 
AN-1756: Application Note 1756 LM3481 Evaluation Board505
Kbytes		30-Apr-08日本語
AN-1471: Application Note 1471 LM3489 Demonstration Board695
Kbytes		24-May-06 

Part Number(s)
(NSID)		Top ViewAvailabilityCurrent Reported StockBudgetary PricingStandard Pack Size
LM3485MM/NOPB
LM3485MM

RoHS



MINI SOIC		Full production
Lead Time: 6 weeks

Samples
DistributorRegionQty
AECO TECHAsia Pacific1000
AITGAsia Pacific1001
ARROWWorldwide899
AVNET-EMWorldwide2975
DIGIKEYWorldwide5677
FARNELLEurope and Asia2398
FUTUREWorldwide1100
KEIKONGAsia Pacific25000
NEWARKAmericas2120
RS COMPONENTSWorldwide470
TECHMOSAAsia Pacific229000
$0.55 each at 1K+ pcsreel
of
1000
LM3485MMX/NOPB
LM3485MMX

RoHS



MINI SOIC		Full production
Lead Time: 8 weeks

 
DistributorRegionQty
ARROWWorldwide3100
DIGIKEYWorldwide0
FUTUREWorldwide1100
NEWARKAmericas940
$0.55 each at 1K+ pcsreel
of
3500

Part Number(s)
(NSID)		DescriptionAvailabilityCurrent Reported StockBudgetary PricingStandard Pack Size
LM3485EVAL
Hysteretic PFET Buck ControllerFull production


 
DistributorRegionQty
DIGIKEYWorldwide2
FUTUREWorldwide1
NATIONALWorldwide58
$30.00 each1
Hysteretic PFET Buck Controller

General Features:
  • Easy to use control methodology
  • No control loop compensation required
  • 4.5V to 35V wide input range
  • 1.242V to VIN adjustable output range
  • High efficiency 93%
  • +1.3% ( +2% over temp) internal reference
  • 100% duty cycle
  • Maximum operating frequency > 1MHz
  • Current limit protection
  • MSOP-8
Applications:
  • Set-Top Box
  • DSL/Cable Modem
  • PC/IA
  • Auto PC
  • TFT Monitor
  • Battery Powered Portable Applications
  • Distributed Power Systems
  • Always On Power
LM3485EVAL Pitchpak includes:
  • A fully assembled LM3485 evaluation board
  • LM3485 Evaluation Board Application Notes (includes Bill of Materials)
  • LM3485 datasheet
  • Switching Regulator Selection Guide

Part Number(s)
(NSID)		DescriptionAvailabilityCurrent Reported StockBudgetary PricingStandard Pack Size
LM3485LED EVAL
Hysteretic PFET Buck ControllerFull production


 
DistributorRegionQty
DIGIKEYWorldwide0
FUTUREWorldwide3
NATIONALWorldwide58
$30.00 each1
LM3485 Hysteretic PFET Buck Controller

General Features:
  • Easy to use control methodology
  • No control loop compensation required
  • 4.5V to 35V wide input range
  • 1.242V to VIN adjustable output range
  • High efficiency 93%
  • ± 1.3% (±2% over temp) internal reference
  • 100% duty cycle
  • Maximum operating frequency > 1MHz
  • Current limit protection
  • MSOP-8
Applications:
  • Set-top Box
  • DSL/Cable Modem
  • PC/IA
  • Auto PC
  • TFT Monitor
  • Battery Powered Portable Applications
  • Distributed Power Systems
  • Always On power
LM3485LED EVAL Pitchpak includes:
  • A fully assembled LM3485LED evaluation board.
  • LM3485 datasheet
  • LM3485LED evaluation board appnote

Part Number(s)
(NSID)		Top ViewTypePinsMSL RatingPeak ReflowRoHSCAD SymbolsModelsPackage
Marking
Format
LM3485MM/NOPB
LM3485MM
MINI SOIC81
1		260
260		RoHSDownloadN/A
ZXTT
S29B
LM3485MMX/NOPB
LM3485MMX
MINI SOIC81
1		260
260		RoHSDownloadN/A
ZXTT
S29B

Reliability Metrics
Part Number Process EFR Reject EFR Sample Size PPM LTA Rejects LTA Device Hours FITS MTTF (Hours)
LM3485MMABCD15003417500423400011201409060
LM3485MMXABCD15003417500423400011201409060

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 22-Nov-2009]