Eda Research

Workflow

1. Load Context

Read existing project constraints:

@docs/design-constraints.json
@docs/project-spec.md
@docs/component-selections.md (if exists)

If constraints missing, ask user for minimum requirements:

• What does this component need to do?
• Key specifications (voltage, current, package)?
• Budget constraints?

2. Understand Requirements

For the target component role, identify:

• Critical specifications (must-have)
• Preferred specifications (nice-to-have)
• Package preferences (SMD size, through-hole)
• Any specific brands or series to consider/avoid

2.5 Check Architecture Constraints

Before searching, review design-constraints.json for:

• Power topology: LDO vs buck decision already made in architect phase
• Thermal budget: Max watts for this role (check thermal.hotComponents)
• DFM targets: Assembly method affects package choice
• Board layers: May affect component density

For power components, see reference/REGULATOR-SELECTION.md for selection criteria. For passives, see reference/PASSIVE-SELECTION.md and reference/DECOUPLING-STRATEGY.md.

3. Research Options

Use web search to understand:

• Common solutions for this application
• Recommended parts from reference designs
• Known issues or considerations
• Alternative approaches

4. Search JLC

Use mcp__jlc__component_search to find candidates:

• Search with specific parameters
• Filter by stock availability
• Note pricing at target quantity
• Check for "Basic" parts (lower assembly fee at JLCPCB)

5. Analyze Candidates

For top 3-5 options:

• Download/fetch datasheets
• Extract key specifications
• Check application circuits
• Note layout requirements
• Identify any gotchas

5.5 Validate Against Constraints

Before presenting options, verify each candidate:

Thermal validation:

P_dissipation = (calculated from datasheet)
Thermal budget = (from design-constraints.json)
✓ P_dissipation < Thermal budget

Assembly compatibility:

• Hand assembly → 0603/0805 minimum, no fine-pitch
• Reflow → 0402+ OK
• Turnkey → Check JLCPCB availability

Architecture compliance:

• Meets LDO/buck decision from architect phase
• Noise specs OK for rail type (analog vs digital)
• Efficiency acceptable for battery applications

Flag any candidates that fail validation with specific concerns.

6. Present Comparison

Create a comparison table:

Include recommendation with rationale.

7. Confirm Selection

• Get user confirmation
• Document selection with rationale
• Update constraint file
• Save datasheet

8. Validate Symbol (After library_fetch)

When fetching online components with mcp__jlc__library_fetch, analyze the returned validation_data:

Quick checks:

Common issues:

• QFN/BGA packages often have exposed thermal pads (EP) not included in symbol
• Pin electrical types may be incorrect (power pins marked as passive)
• Pin names may not match datasheet

Fixing with library_fix:

Use mcp__jlc__library_fix to regenerate symbol with corrections:

mcp__jlc__library_fix lcsc_id="C#####" corrections='{
  "pins": [
    { "action": "add", "number": "EP", "name": "GND", "type": "passive" },
    { "action": "modify", "number": "1", "set_type": "power_in" }
  ]
}'

Correction actions:

• add - Add missing pin (number, name, type required)
• modify - Rename and/or change electrical type
• swap - Swap positions of two pins
• remove - Remove incorrect pin

Output Format

component-selections.md Entry

### [Role]: [Part Name] ([LCSC Number])

**Selected:** [Date]
**MPN:** [Manufacturer Part Number]
**Manufacturer:** [Name]
**Price:** $X.XX @ [quantity]

**Specifications:**
- Key spec 1: value
- Key spec 2: value

**Rationale:**
[Why this part was chosen over alternatives]

**Alternatives Considered:**
- [Part 2] - rejected because [reason]
- [Part 3] - rejected because [reason]

**Design Notes:**
- [Any layout or application notes from datasheet]

**Datasheet:** `datasheets/[filename].pdf`

bom-draft.json Entry

{
  "role": "regulator-3v3",
  "lcsc": "C6186",
  "mpn": "AMS1117-3.3",
  "manufacturer": "AMS",
  "description": "3.3V 1A LDO Regulator",
  "value": "3.3V",
  "footprint": "SOT-223",
  "quantity": 1,
  "unitPrice": 0.04,
  "extendedPrice": 0.04,
  "category": "power",
  "basic": true
}

Component Role Categories

See reference/COMPONENT-CATEGORIES.md for detailed role definitions.

Common roles:

• mcu - Main microcontroller
• regulator-Xv - Voltage regulators
• crystal - Oscillators/crystals
• connector-* - Various connectors
• esd-* - ESD protection
• decoupling-* - Bypass/bulk capacitors
• led-* - Indicator LEDs
• sensor-* - Various sensors

Guidelines

• Prefer JLCPCB "Basic" parts when suitable (lower assembly cost)
• Check stock levels - avoid parts with < 100 in stock
• Consider package size vs hand soldering capability
• Note lead times for non-stock items
• Always document why a part was chosen
• Download datasheets for all selected components
• Identify 1-2 alternatives for critical components (see reference/COMPONENT-ALTERNATIVES.md)
• Validate thermal before confirming power components
• Check architecture decisions from design-constraints.json before selecting

Reference Documents

Next Steps

After component selection is complete:

1. Run /eda-source for remaining components
2. When all components selected, run /eda-schematic
3. Update design-constraints.json stage to "schematic"