Archived datasheet entries and legacy databooks show the LT1178ACN8's package, pinout, and core electrical parameters used in power-supply designs. This guide synthesizes archived information for repair, reverse engineering, and legacy-design maintenance.
The goal is practical: provide concise, data-driven reference tables, a labeled pin mapping suitable for diagram reproduction, recommended electrical tests, and design/layout checklists engineers can action immediately in the lab. Where archived sources differ or lack clarity, the text flags uncertainty and recommends bench verification before any critical substitution or redesign.
Overview & Package/Pinout Summary
Pinout Diagram and Package Variants
Package options commonly referenced in archives include an 8-pin PDIP and an 8-pin SOIC variant; pin functions are consistent between these variants. Below is a compact table mapping pin number to function. Confirm package marking before wiring—pin numbering follows the chamfer/dot convention on PDIP and SOIC bodies.
| Pin # | Pin Name | Function (Brief) |
|---|---|---|
| 1 | V+ | Positive supply input |
| 2 | IN- | Negative input / sense |
| 3 | OUT | Main output / driver node |
| 4 | GND | Ground reference / thermal path |
| 5 | FB | Feedback / regulation sense |
| 6 | COMP | Compensation / loop adjust |
| 7 | EN | Enable / shutdown |
| 8 | SYNC | Sync or oscillator control |
Mechanical Dimensions & Thermal Considerations
Archived mechanical tables indicate standard 8-pin SOIC and PDIP footprints. Recommended PCB land patterns include 0.049" (1.25 mm) pitch for SOIC and 0.300" (7.62 mm) spacing for PDIP.
- ✔ PCB footprint checklist: Verify pad sizes, toe fillet, and solder mask openings before reflow.
- ✔ Thermal callouts: Add thermally conductive plane under GND; use 2–4 vias for thermal relief in SOIC land.
Electrical Specifications & Absolute Limits
The following quick-reference table summarizes absolute maximums and recommended operating values. Verify critical values against physical part markings.
| Parameter | Recommended | Absolute Max | Units |
|---|---|---|---|
| Supply Voltage (V+) |
±5 to 18
|
±20
|
V |
| Output Current |
Typ 50
|
Max 100
|
mA |
| Operating Junction |
-40 to 85
|
-40 to 125
|
°C |
| Storage Temp |
-55 to 125
|
-55 to 150
|
°C |
Typical Performance Characteristics
Engineers should reproduce standard plots for validation:
- Efficiency vs. Load: 0–100% scale.
- Line/Load Regulation: Vout vs. Vin and Vout vs. Iout.
- Transient Response: Capture 10–90% load step.
- Switching Waveform: Monitor at the OUT node.
Test Procedures & Bench Benchmarks
Step-by-Step Checklist
- Confirm pinout visually via marking dot.
- Use 1A current limit initially to prevent damage.
- Power up at min Vin and check no-load Vout.
- Apply incremental load while monitoring ripple and temp.
- Record Vout tolerance and capture transient response.
Example Benchmark Results
| Test | Measured | Status |
|---|---|---|
| Vout (12V/100mA) | 11.98 V | PASS |
| Ripple | 18 mVp-p | PASS |
| Thermal Rise | +22°C | PASS |
Typical Application Circuits & Design Notes
Common Topologies: Includes simple linear regulators and switch-mode front ends.
BOM Highlights
- Cinput: 10–47 μF low-ESR
- Ccomp: 10–100 nF
- Rfb Divider: 10k/10k (Base)
Layout Tips
- Decoupling: 0.1 μF within 3mm of V+
- EMI: Use ferrite beads on input
- GND: Solid plane for stability
Troubleshooting & Failure Modes
Symptom Mapping:
- 🔴 No Output: Blown device or input fuse. Measure V+ pin.
- 🔴 Excessive Ripple: Degraded caps or poor layout. Scope switching node.
- 🔴 Overheating: Insufficient copper/thermal path. Check soldering.
FAQ
What is the recommended way to verify LT1178ACN8 pinout before powering? ▼
Can I substitute a modern regulator for the LT1178ACN8 in a legacy board? ▼
What bench measurement best indicates a failing LT1178ACN8? ▼
Summary
In short, the LT1178ACN8 reference consolidates archived datasheet and pinout information into quick-reference tables, lab-ready tests, and practical layout checklists. Key retention points: confirm package pinout visually, verify absolute limits on the bench, and run specified transient/thermal tests before production use or repair validation.
