Texas Instruments LM5155DSSR

The LM5155DSSR controls an external N-channel MOSFET in positive-output boost and SEPIC converters and in isolated or non-isolated flyback converters. Its wide BIAS range, low-current operating modes, programmable synchronization, adjustable soft start, power-good output, and protection functions support compact power supplies operating from batteries and industrial rails.

LM5155DSSR is supplied in TI's 12-pin WSON (DSS) surface-mount package with an exposed thermal pad and a nominal 3 mm × 2 mm body. The customer package registry maps this orderable part to 12-WFDFN Exposed Pad. The DSSR carrier is a 3,000-piece large tape-and-reel.

Layout checks

• Use TI's current DSS package drawing and recommended land pattern for final pad geometry.
• Connect the exposed pad to AGND and a suitable ground copper area for heat spreading.
• Keep the GATE and current-sense paths short, and separate CS, FB, COMP, RT, and SS routing from switching nodes.
• Place BIAS and VCC bypass capacitors close to their pins with short returns to PGND.

The registered package JPG is currently missing and must be added before publication. Confirm pin-1 orientation, exposed-pad geometry, stencil design, and assembly rules against TI's latest mechanical drawing.

The following mapping is for the TI 12-pin WSON DSS package, top view.

The UVLO/EN/SYNC pin must not float. When the function is unused, follow TI's specified connection to BIAS. Confirm all passive values and grounding paths in the current datasheet.

Typical values, limits, and operating ranges may use different test conditions. Use the TI electrical-characteristics tables and design equations for guaranteed limits and worst-case calculations.

Evaluate alternatives using the full ordering code. Package similarity does not by itself prove electrical or qualification equivalence.

• LM5155DSST: TI lists this as the same LM5155 device and DSS package in a 250-piece small tape-and-reel carrier. The electrical function and footprint are the closest match; confirm purchasing and carrier requirements.
• LM51551DSSR: Same controller family and 12-pin DSS package, with hiccup-mode overload protection enabled. Revalidate overload recovery, startup behavior, and system fault requirements.
• LM5155QDSSRQ1: Automotive-qualified LM5155 variant with wettable-flank package details and an operating range extending to 150 °C. Confirm the exact land pattern, qualification requirements, marking, and approved bill of materials.
• LM5155QDSSTQ1: Small-reel automotive ordering option. It changes both carrier quantity and qualification class, so procurement and assembly documentation must be reviewed.

For every substitution, compare the exact package drawing, pin configuration, current-limit behavior, hiccup option, reference and UVLO behavior, temperature rating, wettable-flank designation, and carrier quantity before approving the change.

Texas Instruments lists LM5155DSSR as an active catalog device. The controlled sources used for this summary are the LM5155DSSR orderable-part page and the LM5155/LM51551 datasheet, document SNVSB75E.

• Exact ordering identity: LM5155DSSR, WSON DSS, 12 pins, large tape-and-reel.
• Qualification: Catalog grade. Do not infer AEC-Q100 qualification from the related LM5155-Q1 family.
• Assembly data: TI lists NiPdAu lead finish, MSL 1 at 260 °C peak reflow, and RoHS compliance for this orderable part.

• Identity: verify the complete LM5155DSSR ordering code, DSS package, 1U4H device marking, reel label, and pin-1 orientation.
• Traceability: retain supplier, lot, date-code, and packaging records required by the purchasing specification.
• Handling: follow current TI guidance for ESD, moisture sensitivity, storage, reflow, and exposed-pad assembly.
• Inspection: compare package dimensions and markings with controlled manufacturer data rather than relying on product photographs alone.