PCB Assembly Challenges

flux

Completed the full no-consign JLCPCB audit. Every BOM component now has an LCSC part number, and unavailable/uncertain passive parts were changed to stocked, same-package, equal-or-better electrical alternatives; no footprint or routing changes were required.
Key confirmed stock included:
  • ESP32 module C701346: ~2,358
  • DRV8873-Q1 C2150479: ~2,381
  • LM5146-Q1 C1850329: ~2,300
  • L2 C2047831: ~446
  • Q1/Q2 C396083: ~1,990
  • F1 C135417: ~825
Checks show no current sourcing/manufacturing or DRC errors. Stock can change before checkout, so JLCPCB’s live BOM matching page remains the final authority.
Updated files:
  • Gerbers ZIP

  • JLCPCB BOM

    CommentDesignatorFootprintJLCPCB Part #LCSC Part #
    35YXF2200MFFC16X31.5C1C88844
    C3225X7R1H106KT000EC2C432929
    CC0603KRX7R7BB224C3C106249
    CL21A226MPQNNNEC10, C6, C7, C8, C9C29277
    TCC0603X5R105M500CTC11, C13, C15, C5C20539427
    CL10B104KB8NNNCC12, C16, C28, C4C1591
    CL10B473KO8NNNCC14, C29C2762284
    GRM31CR72A225KA73LC17, C18, C19, C20, C21C913599
    CC1210MKX7R9BB226C22, C23, C24, C25, C26C914881
    CL10A225KL8NNNCC27C307463
    CL10B472JB8NNNCC30C159797
    TCC0603COG101J500CTC31C344186
    SS510D1, D2, D3, D4SMC_L6.9-W5.9-LS7.9-R-RDC717458
    SMBJ26A-TRD5SMB_L4.6-W3.6-LS5.3-RDC133666
    A30-600F1FUSE-TH_L19.1-W3.0-P10.20-D1.2-S2.0C135417
    B2P-VH(LF)(SN)J1, J2CONN-TH_B2P-VH-LF-SNC160315
    VLS6045EX-6R8ML1C415364
    SPM10065VT-6R8M-DL2IND-SMD_L10.5-W10.0C2047831
    P0603P1N46G12LED1C5123548
    KT-0603RLED2C2286
    SED10070GGQ1, Q2DFN-8_L5.1-W5.7-P1.27-LS6.1-BLC396083
    RC0603FR-07100KLR1, R8C14675
    AC0603FR-0743K2LR2C227902
    RC0603FR-07820RLR5C114638
    SCR0603F68KR7C3016380
    RC0603FR-07215KLR9C22954
    RC0603FR-0710KLR10, R13, R3, R4, R6C98220
    RC0603FR-0724K9LR11C137761
    CRCW0603174KFKEAR12C2076698
    CR0603FA6190GR14C101134
    RC0603FR-078K06LR15C131052
    RC0603FR-071KLR16, R17C21190
    DRV8873HPWPRQ1U1HTSSOP-24_L7.8-W4.4-P0.65-LS6.4-BL-EP5.2C2150479
    74LVC1G04SE-7U2SOT-353_L2.2-W1.4-P0.65-LS2.4-BRC264081
    LMR33630BDDARU3SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL-EP2.8-1C544370
    ESP32-WROOM-32UE-N16U4C701346
    LM5146QRGYRQ1U5VQFN-20_L4.5-W3.5-P0.50-BL-EP-1C1850329

  • JLCPCB Pick-and-place

    DesignatorLayerRotationMid XMid Y
    C1Top90-5mm-27.25mm
    C2Bottom0-4mm34mm
    C3Bottom0-12.5mm8mm
    C4Bottom903.5mm34mm
    C5Bottom2700mm34mm
    C6Bottom180-12mm25mm
    C7Bottom180-8mm25mm
    C8Bottom180-4mm25mm
    C9Bottom1800mm25mm
    C10Bottom180-12mm30mm
    C11Bottom270-8mm30mm
    C12Bottom0-4mm30mm
    C13Bottom2705mm8mm
    C14Bottom08mm8mm
    C15Bottom18010.8mm8mm
    C16Bottom9012mm5.5mm
    C17Bottom0-11.4mm-9mm
    C18Bottom0-6.8mm-9mm
    C19Bottom0-2.2mm-9mm
    C20Bottom02.4mm-9mm
    C21Bottom07mm-9mm
    C22Bottom011.2mm-9mm
    C23Bottom0-10.8mm-13mm
    C24Bottom270-7mm-13mm
    C25Bottom90-2mm-13mm
    C26Bottom03mm-13mm
    C27Bottom180-12mm1mm
    C28Bottom0-9mm1mm
    C29Bottom270-5.5mm1mm
    C30Bottom90-2mm1mm
    C31Bottom01.5mm1mm
    D1Top180-9.2mm-14mm
    D2Top180-9.2mm-7mm
    D3Top1802mm-14mm
    D4Top1802mm-7mm
    D5Top909.5mm-26mm
    F1Top1800mm-20mm
    J1Top1809mm-37mm
    J2Top010.07mm36mm
    L1Bottom0-2.2mm15mm
    L2Top0-7mm4mm
    LED1Top0-12.2mm32.2mm
    LED2Top0-5mm32.2mm
    Q1Top09.63mm-0.8mm
    Q2Top010.83mm-8.6mm
    R1Bottom180-11mm6mm
    R2Bottom90-8mm6mm
    R3Bottom900mm30mm
    R4Bottom04mm30mm
    R5Bottom05mm12mm
    R6Bottom1808mm12mm
    R7Bottom011mm12mm
    R8Bottom012mm14mm
    R9Bottom05mm-1mm
    R10Bottom2708mm-1mm
    R11Bottom27011mm-1mm
    R12Bottom0-12.5mm-5mm
    R13Bottom180-9mm-5mm
    R14Bottom0-5.5mm-5mm
    R15Bottom0-2mm-5mm
    R16Top0-8.8mm32.2mm
    R17Top0-1.6mm32.2mm
    U1Top1809.5mm7.5mm
    U2Bottom27011.5mm18mm
    U3Bottom270-10.3mm14.995mm
    U4Top0-3.4mm21.03mm
    U5Top1803mm1.5mm
Validate and prepare order
Run final DRC
Review 5 A copper
Verify JLCPCB files
Explain BOM matching

Refine this doc
Ask about this doc
18 V DCC Regulator Notes
Decision
Added a regulated 18 V / 5 A buck stage between raw rectified VBUS and the DRV8873 VM rail. A 36 V-max integrated module was rejected because a 24 VAC transformer can exceed 36 V after rectification under high-line/light-load conditions.
Selected Architecture
  • Controller: TI LM5146-Q1 100 V synchronous buck controller
  • External MOSFETs: 100 V class 5x6 DFN devices
  • Inductor: 6.8 uH high-current SMD inductor
  • Input: rectified 18-24 VAC bus
  • Output: regulated 18V_DCC rail feeding DRV8873 VM
Power Budget
  • DCC rail target: 18 V at 5 A = 90 W
  • Estimated buck efficiency: 90-94%
  • Required input power: about 96-100 W
  • Input current at 25 V bus: about 4 A average, higher in rectifier charging pulses
  • Existing 6 A fuse remains appropriate for the input target but must be thermally checked.
Important Risks / To Verify
  • 2200 uF VBUS bulk capacitance may not hold the buck input above dropout at full 90 W from 18 VAC; bench test ripple and consider more capacitance if full-load regulation is required at low-line.
  • LM5146 compensation and current limit values are provisional from the TI 12 V / 8 A reference family and must be recalculated with TI WEBENCH or the LM5146 Quickstart Calculator before production.
  • 18 V output capacitor effective capacitance must be checked at DC bias.
  • Layout must prioritize the buck hot loop, MOSFET thermal copper, inductor current path, and DRV8873 PowerPAD thermal vias.

  • Decision

  • Selected Architecture

  • Power Budget

  • Important Risks / To Verify

TMCC WiFi DCC 5A Module

TMCC WiFi DCC 5A Module thumbnail
Per-locomotive 18 VAC input module that regenerates a 5 A bipolar DCC output using an ESP32 WiFi module and DRV8873 H-bridge, targeting standard PCB assembly.

Properties

Properties describe core aspects of the project.

Pricing & Availability

Distributor

Qty 1

Arrow

$7.88–$9.21

Digi-Key

$0.02

HQonline

$5.12–$5.46

LCSC

$14.35–$14.77

Mouser

$20.51–$22.80

TME

$10.04

Verical

$0.39–$212.32

Controls