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LM1085
3A Low Dropout Positive Regulators

General Description

The LM1085 is a series of low dropout positive voltage
regulators with a maximum dropout of 1.5V at 3A of load
current. It has the same pin-out as National Semiconductor’s
industry standard LM317.

The LM1085 is available in an adjustable version, which can
set the output voltage with only two external resistors. It is
also available in three fixed voltages: 3.3V, 5.0V and 12.0V.
The fixed versions integrate the adjust resistors.

The LM1085 circuit includes a zener trimmed bandgap ref-
erence, current limiting and thermal shutdown.

The LM1085 series is available in TO-220 and TO-263 pack-
ages. Refer to the LM1084 for the 5A version, and the
LM1086 for the 1.5A version.

Features

n

Available in 3.3V, 5.0V, 12V and Adjustable Versions

n

Current Limiting and Thermal Protection

n

Output Current

3A

n

Line Regulation

0.015% (typical)

n

Load Regulation

0.1% (typical)

Applications

n

High Efficiency Linear Regulators

n

Battery Charger

n

Post Regulation for Switching Supplies

n

Constant Current Regulator

n

Microprocessor Supply

Connection Diagrams

TO-220

10094702

Top View

TO-263

10094704

Top View

Basic Functional Diagram,
Adjustable Version

10094765

Application Circuit

10094752

1.2V to 15V Adjustable Regulator

June 2005

LM1085

3A

Low

Dropout

Positive

Regulators

© 2005 National Semiconductor Corporation

DS100947

www.national.com

Содержание LM1085 Series

Страница 1: ...n The LM1085 series is available in TO 220 and TO 263 pack ages Refer to the LM1084 for the 5A version and the LM1086 for the 1 5A version Features n Available in 3 3V 5 0V 12V and Adjustable Versions n Current Limiting and Thermal Protection n Output Current 3A n Line Regulation 0 015 typical n Load Regulation 0 1 typical Applications n High Efficiency Linear Regulators n Battery Charger n Post R...

Страница 2: ...TS3B LM1085ISX ADJ Tape and Reel LM1085IS 12 Rails LM1085ISX 12 Tape and Reel LM1085IS 3 3 Rails LM1085ISX 3 3 Tape and Reel LM1085IS 5 0 Rails LM1085ISX 5 0 Tape and Reel 3 lead TO 220 40 C to 125 C LM1085IT ADJ Rails T03B LM1085IT 12 Rails LM1085IT 3 3 Rails LM1085IT 5 0 Rails Simplified Schematic 10094734 LM1085 www national com 2 ...

Страница 3: ...Reference Voltage LM1085 ADJ IOUT 10mA VIN VOUT 3V 10mA IOUT IFULL LOAD 1 5V VIN VOUT 15V Note 7 1 238 1 225 1 250 1 250 1 262 1 270 V V VOUT Output Voltage Note 7 LM1085 3 3 IOUT 0mA VIN 5V 0 IOUT IFULL LOAD 4 8V VIN 15V 3 270 3 235 3 300 3 300 3 330 3 365 V V LM1085 5 0 IOUT 0mA VIN 8V 0 IOUT IFULL LOAD 6 5V VIN 20V 4 950 4 900 5 000 5 000 5 050 5 100 V V LM1085 12 IOUT 0mA VIN 15V 0 IOUT IFULL ...

Страница 4: ...ice is intended to be functional but specific performance is not guaranteed For guaranteed specifications and the test conditions see the Electrical Characteristics Note 2 Power dissipation is kept in a safe range by current limiting circuitry Refer to Overload Recovery in Application Notes Note 3 The maximum power dissipation is a function of TJ max θJA and TA The maximum allowable power dissipat...

Страница 5: ...uit Current vs Input Output Difference 10094763 10094768 Percent Change in Output Voltage vs Temperature Adjust Pin Current vs Temperature 10094799 10094798 Maximum Power Dissipation vs Temperature Ripple Rejection vs Frequency LM1085 Adj 10094770 10094743 LM1085 www national com 5 ...

Страница 6: ...Typical Performance Characteristics Continued Ripple Rejection vs Output Current LM1085 Adj Line Transient Response 10094744 10094772 Load Transient Response 10094771 LM1085 www national com 6 ...

Страница 7: ...lues will assure stability for the majority of applications The adjustable versions allows an additional capacitor to be used at the ADJ pin to increase ripple rejection If this is done the output capacitor should be increased to 22uF for tantal ums or to 150uF for aluminum Capacitors other than tantalum or aluminum can be used at the adjust pin and the input pin A 10uF capacitor is a reasonable v...

Страница 8: ...gu lator the internal diode between the output and input pins can withstand microsecond surge currents of 10A to 20A With an extremely large output capacitor 1000 µf and with input instantaneously shorted to ground the regulator could be damaged In this case an external diode is recom mended between the output and input pins to protect the regulator shown in Figure 5 OVERLOAD RECOVERY Overload rec...

Страница 9: ...he Absolute Maximum section of the datasheet TJ max is 125 C for the control section while TJ max is 150 C for the output section θJA max should be calculated separately for each section as follows θJA max CONTROL SECTION 125 C TA max PD θJA max OUTPUT SECTION 150 C TA max PD The required heat sink is determined by calculating its re quired thermal resistance θHA max θHA max θJA max θJC θCH θHA ma...

Страница 10: ...750 Adjustable 5V 10094752 1 2V to 15V Adjustable Regulator 10094753 5V Regulator with Shutdown 10094754 Battery Charger 10094755 Adjustable Fixed Regulator 10094756 Regulator with Reference 10094757 High Current Lamp Driver Protection LM1085 www national com 10 ...

Страница 11: ...ns Continued 10094759 Battery Backup Regulated Supply 10094760 Ripple Rejection Enhancement 10094761 Automatic Light control 10094762 Generating Negative Supply voltage 10094758 Remote Sensing LM1085 www national com 11 ...

Страница 12: ...Physical Dimensions inches millimeters unless otherwise noted 3 Lead TO 263 NS Package Number TS3B 3 Lead TO 220 NS Package Number T03B LM1085 www national com 12 ...

Страница 13: ...nent of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness BANNED SUBSTANCE COMPLIANCE National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products Stewardship Specification CSP 9 111C2 and the Banned Substa...

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