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LM1085IS-3.3 Linear Voltage Regulator - Equivalent & Substitute Parts
Part Overview
The LM1085IS-3.3 is a positive fixed linear voltage regulator IC manufactured by Texas Instruments, rated for 3.3V output at 3A maximum current. This device is classified as Last Time Buy, indicating discontinued production status. The regulator is housed in a TO-263 (DDPAK-3) surface mount package and provides over-current and over-temperature protection. Due to its Last Time Buy status, identifying equivalent substitute parts from active product lines is essential for ongoing design support and procurement continuity.
Substiute Parts
Key Parameters
| Parameter | Value |
|---|---|
| Manufacturer | Texas Instruments |
| Part Number | LM1085IS-3.3 |
| Output Voltage | 3.3V Fixed |
| Output Current | 3A |
| Input Voltage (Max) | 27V |
| Voltage Dropout (Max) | 1.5V @ 3A |
| Quiescent Current | 10 mA |
| PSRR | 72dB (120Hz) |
| Protection Features | Over Current, Over Temperature |
| Operating Temperature | -40°C to 125°C (TJ) |
| Package | TO-263 (DDPAK-3) |
| Mounting Type | Surface Mount |
| RoHS Status | ROHS3 Compliant |
| MSL Rating | 3 (168 Hours) |
Substitute Part Grouping Explanation
Substitution eligibility for the LM1085IS-3.3 is determined by the following critical parameters:
- Output voltage specification: 3.3V fixed
- Output current capability: minimum 3A
- Package compatibility: TO-263 (DDPAK-3) surface mount
- Input voltage tolerance: maximum 27V or higher
- Voltage dropout: 1.5V @ rated current or lower
- Protection features: over-current and over-temperature protection
- Operating temperature range: -40°C to 125°C or wider
- RoHS3 compliance and REACH unaffected status
Substitute parts are grouped into two categories: direct equivalents from the same manufacturer (Texas Instruments) and cross-manufacturer alternatives that meet all electrical and mechanical specifications.
Parameter Comparison
| Parameter | LM1085IS-3.3 | LM1085IS-3.3/NOPB | LD1085D2M33R | LD1086D2M33TR | LT1085CM-3.3#PBF | LT1085CM-3.3#TRPBF |
|---|---|---|---|---|---|---|
| Manufacturer | Texas Instruments | Texas Instruments | STMicroelectronics | STMicroelectronics | Analog Devices Inc. | Analog Devices Inc. |
| Output Voltage | 3.3V | 3.3V | 3.3V | 3.3V | 3.3V | 3.3V |
| Output Current | 3A | 3A | 3A | 1.5A | 3A | 3A |
| Input Voltage (Max) | 27V | 27V | 30V | 30V | 20V | 20V |
| Voltage Dropout (Max) | 1.5V @ 3A | 1.5V @ 3A | 1.5V @ 3A | 1.5V @ 1.5A | 1.5V @ 3A | 1.5V @ 3A |
| Quiescent Current | 10 mA | 10 mA | 10 mA | 10 mA | 10 mA | 10 mA |
| PSRR | 72dB (120Hz) | 72dB (120Hz) | 72dB (120Hz) | 79dB (120Hz) | 72dB (120Hz) | 72dB (120Hz) |
| Protection Features | Over Current, Over Temperature | Over Current, Over Temperature | Over Current, Over Temperature | Over Current, Over Temperature | Over Temperature | Over Temperature |
| Operating Temperature | -40°C to 125°C | -40°C to 125°C | -40°C to 125°C | -40°C to 125°C | 0°C to 125°C | 0°C to 125°C |
| Package | TO-263 (DDPAK-3) | TO-263 (DDPAK-3) | D2PAK-3 | D2PAK-3 | DDPAK-3 | DDPAK-3 |
| Product Status | Last Time Buy | Active | Active | Active | Active | Active |
| RoHS Status | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant | ROHS3 Compliant |
| MSL Rating | 3 (168 Hours) | 3 (168 Hours) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) | 1 (Unlimited) |
Engineering Selection Recommendations
Primary Substitute: LM1085IS-3.3/NOPB
The LM1085IS-3.3/NOPB is the direct equivalent from Texas Instruments with Active product status. This part maintains identical electrical specifications and package configuration to the LM1085IS-3.3. Selection of this part eliminates any design re-qualification requirements and provides the longest product lifecycle support.
Secondary Substitutes: LD1085D2M33R and LT1085CM-3.3 Series
The LD1085D2M33R from STMicroelectronics and LT1085CM-3.3#PBF/LT1085CM-3.3#TRPBF from Analog Devices Inc. are functionally equivalent alternatives. All three parts meet the 3.3V output, 3A current, and protection feature requirements. The LD1085D2M33R offers improved input voltage tolerance (30V maximum) and superior moisture sensitivity rating (MSL 1). The LT1085CM-3.3 series provides identical electrical performance with ROHS3 compliance and unlimited MSL rating.
Not Recommended: LD1086D2M33TR
The LD1086D2M33TR is not suitable as a direct substitute due to reduced output current specification (1.5A versus 3A required). This part is applicable only in applications where maximum output current does not exceed 1.5A.
Compliance Considerations
All recommended substitutes maintain ROHS3 compliance and REACH unaffected status, ensuring regulatory continuity. Parts with MSL 1 rating (LD1085D2M33R and LT1085CM-3.3 series) provide superior moisture handling characteristics compared to the original MSL 3 specification.
Frequently Asked Questions (FAQ)
Q: Can the LM1085IS-3.3/NOPB be used as a direct replacement for LM1085IS-3.3?
A: Yes. The LM1085IS-3.3/NOPB is electrically and mechanically identical to the LM1085IS-3.3. The only difference is product status: LM1085IS-3.3/NOPB is Active, while the original is Last Time Buy. No design changes are required.
Q: What is the difference between LD1085D2M33R and LT1085CM-3.3#PBF?
A: Both parts deliver 3.3V at 3A with identical dropout voltage and quiescent current. The LD1085D2M33R supports higher input voltage (30V versus 20V) and has superior moisture sensitivity (MSL 1 versus MSL 1). The LT1085CM-3.3#PBF operates over a narrower temperature range (0°C to 125°C versus -40°C to 125°C) and lacks over-current protection, providing only over-temperature protection.
Q: Is the LD1086D2M33TR compatible with designs requiring 3A output?
A: No. The LD1086D2M33TR is rated for 1.5A maximum output current. It is not suitable for applications requiring the full 3A capability of the LM1085IS-3.3. Use this part only in designs where load current does not exceed 1.5A.
Q: Are the D2PAK-3 and DDPAK-3 packages interchangeable?
A: Yes. D2PAK-3 and DDPAK-3 are equivalent package designations for the TO-263 surface mount package with three leads plus tab. PCB footprints are identical, and parts are mechanically and electrically interchangeable.
Q: What is the significance of the /NOPB suffix on LM1085IS-3.3/NOPB?
A: The /NOPB suffix indicates "No Plumbum" (lead-free) packaging, confirming ROHS3 compliance. This is a manufacturing designation and does not affect electrical performance or compatibility.
Q: Why do some substitutes have different operating temperature ranges?
A: Operating temperature range is a design specification set by each manufacturer. The LT1085CM-3.3 series operates from 0°C to 125°C, which is narrower than the LM1085IS-3.3 range of -40°C to 125°C. Verify that your application's temperature requirements fall within the selected substitute's operating range before implementation.
Q: What does MSL rating mean, and why does it vary among substitutes?
A: MSL (Moisture Sensitivity Level) indicates the maximum time a component can be exposed to moisture at specified temperature and humidity before soldering. MSL 1 (unlimited) provides superior moisture tolerance compared to MSL 3 (168 hours). For applications with extended storage or high-humidity environments, parts with MSL 1 rating are preferred.
Q: Can I use LT1085CM-3.3#TRPBF instead of LT1085CM-3.3#PBF?
A: Yes. Both parts are electrically identical. The difference is packaging format: #TRPBF indicates Tape & Reel packaging, while #PBF indicates Tube packaging. Selection depends on procurement and assembly requirements, not electrical performance.
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