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LM1085

www.ti.com

SNVS038G –JULY 1999–REVISED MARCH 2013

LM1085 3A Low Dropout Positive Regulators

Check for Samples: LM1085

FEATURES

DESCRIPTION

The LM1085 is a series of low dropout positive

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

voltage regulators with a maximum dropout of 1.5V at

Versions

3A of load current. It has the same pin-out as TI's

• Current Limiting and Thermal Protection

industry standard LM317.

• Output Current 3A

The LM1085 is available in an adjustable version,

• Line Regulation 0.015% (typical)

which can set the output voltage with only two

external resistors. It is also available in three fixed

• Load Regulation 0.1% (typical)

voltages: 3.3V, 5.0V and 12.0V. The fixed versions

integrate the adjust resistors.

APPLICATIONS

The LM1085 circuit includes a zener trimmed

• High Efficiency Linear Regulators

bandgap reference, current limiting and thermal

• Battery Charger

shutdown.

• Post Regulation for Switching Supplies

The LM1085 series is available in TO-220 and

• Constant Current Regulator

DDPAK/TO-263 packages. Refer to the LM1084 for

• Microprocessor Supply

the 5A version, and the LM1086 for the 1.5A version.

Connection Diagram

Figure 1. TO-220 Top View Figure 2. DDPAK/TO-263 Top View

Figure 3. Basic Functional Diagram, Adjustable Figure 4. Application Circuit

Version

1.2V to 15V Adjustable Regulator

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (22 pages)

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LM1085 www.ti.com SNVS038G – JULY 1999 – REVISED MARCH 2013 LM1085 3A Low Dropout Positive Regulators Check for Samples: LM1085 FEATURES 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 TI's industry standard LM317. 1 2 • • • • Available in 3.3V, 5.0V, 12V and Adjustable Versions Current Limiting and Thermal Protection Output Current 3A Line Regulation 0.015% (typical) Load Regulation 0.
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LM1085 SNVS038G – JULY 1999 – REVISED MARCH 2013 www.ti.com Simplified Schematic Figure 5.
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LM1085 www.ti.com SNVS038G – JULY 1999 – REVISED MARCH 2013 These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) Maximum Input to Output Voltage Differential LM1085-ADJ 29V LM1085-12 18V LM1085-3.3 27V LM1085-5.
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LM1085 SNVS038G – JULY 1999 – REVISED MARCH 2013 www.ti.com Electrical Characteristics (continued) Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the operating junction temperature (TJ) range of -40°C to +125°C. Minimum and Maximum limits are ensured through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Symbol Typ Max (1) Units 0.015 0.035 0.2 0.
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LM1085 www.ti.com SNVS038G – JULY 1999 – REVISED MARCH 2013 Typical Performance Characteristics Dropout Voltage vs. Output Current Short-Circuit Current vs. Input/Output Difference Figure 6. Figure 7. Percent Change in Output Voltage vs. Temperature Adjust Pin Current vs. Temperature Figure 8. Figure 9.
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LM1085 SNVS038G – JULY 1999 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) Maximum Power Dissipation vs. Temperature Ripple Rejection vs. Frequency (LM1085-Adj.) Figure 10. Figure 11. Ripple Rejection vs. Output Current (LM1085-Adj.) Line Transient Response Figure 12. Figure 13. Load Transient Response Figure 14.
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LM1085 www.ti.com SNVS038G – JULY 1999 – REVISED MARCH 2013 APPLICATION NOTE GENERAL Figure 15 shows a basic functional diagram for the LM1085-Adj (excluding protection circuitry) . The topology is basically that of the LM317 except for the pass transistor. Instead of a Darlingtion NPN with its two diode voltage drop, the LM1085 uses a single NPN. This results in a lower dropout voltage. The structure of the pass transistor is also known as a quasi LDO.
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LM1085 SNVS038G – JULY 1999 – REVISED MARCH 2013 www.ti.com 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 tantalums 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 value at the input. See RIPPLE REJECTION section regarding the value for the adjust pin capacitor.
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LM1085 www.ti.com SNVS038G – JULY 1999 – REVISED MARCH 2013 Figure 18. Best Load Regulation using Adjustable Output Regulator PROTECTION DIODES Under normal operation, the LM1085 regulator does not need any protection diode. With the adjustable device, the internal resistance between the adjustment and output terminals limits the current. No diode is needed to divert the current around the regulator even with a capacitor on the adjustment terminal.
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LM1085 SNVS038G – JULY 1999 – REVISED MARCH 2013 www.ti.com THERMAL CONSIDERATIONS FOR THE TO-220 PACKAGE ICs heats up when in operation, and power consumption is one factor in how hot it gets. The other factor is how well the heat is dissipated. Heat dissipation is predictable by knowing the thermal resistance between the IC and ambient (θJA). Thermal resistance has units of temperature per power (°C/W). The higher the thermal resistance, the hotter the IC.
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LM1085 www.ti.com SNVS038G – JULY 1999 – REVISED MARCH 2013 Figure 21. Heat sink thermal Resistance vs Area THERMAL CONSIDERATION FOR THE DDPAK/TO-263 PACKAGE Unlike the TO-220 package, the TO-263 package uses the printed circuit board as the heat sink to remove heat from the device. The device dissipation is: PD = OUTPUT Section Dissipation + CONTROL Section Dissipation (8) For the LM1085IS-x.
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LM1085 SNVS038G – JULY 1999 – REVISED MARCH 2013 www.ti.com For more information refer to : “Application Note 1520 A Guide to Board Layout for Best Thermal Resistance for Exposed Packages”, TI Literature Number: SNVA183 It is important to remember that the TAB of the LM1085IS package is internally conntected to device pin 2 (OUTPUT), so the copper area connected to the TAB must be isolated from all other potentials, including ground.
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LM1085 www.ti.com SNVS038G – JULY 1999 – REVISED MARCH 2013 Figure 28. Regulator with Reference Figure 29. High Current Lamp Driver Protection Figure 30. Battery Backup Regulated Supply Figure 31. Ripple Rejection Enhancement Figure 32. Automatic Light control Figure 33.
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LM1085 SNVS038G – JULY 1999 – REVISED MARCH 2013 www.ti.com Figure 34.
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LM1085 www.ti.com SNVS038G – JULY 1999 – REVISED MARCH 2013 REVISION HISTORY Changes from Revision F (March 2013) to Revision G • Page Deleted layout of National Data Sheet to TI format ............................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LM1085IS-12/NOPB ACTIVE DDPAK/ TO-263 KTT 3 45 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM1085 IS-12 LM1085IS-3.3 NRND DDPAK/ TO-263 KTT 3 45 TBD Call TI Call TI -40 to 125 LM1085 IS-3.3 LM1085IS-3.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
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PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM1085ISX-3.3 DDPAK/ TO-263 KTT 3 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2 LM1085ISX-3.3/NOPB DDPAK/ TO-263 KTT 3 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2 LM1085ISX-5.0/NOPB DDPAK/ TO-263 KTT 3 500 330.0 24.4 10.
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PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM1085ISX-3.3 DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0 LM1085ISX-3.3/NOPB DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0 LM1085ISX-5.0/NOPB DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0 LM1085ISX-ADJ DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0 LM1085ISX-ADJ/NOPB DDPAK/TO-263 KTT 3 500 367.0 367.0 45.
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MECHANICAL DATA NDE0003B www.ti.
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MECHANICAL DATA KTT0003B TS3B (Rev F) BOTTOM SIDE OF PACKAGE www.ti.
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IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.