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diff --git a/docs/hardware/PROCUREMENT_T64.md b/docs/hardware/PROCUREMENT_T64.md new file mode 100644 index 0000000..1102a84 --- /dev/null +++ b/docs/hardware/PROCUREMENT_T64.md @@ -0,0 +1,38 @@ +# T64 procurement sheet — gray-market MDAC line (v1, 2026-07-16) + +Anchor prices: TLC7528CDW (TI, new) $5.05@1k DigiKey, 845 in stock, 9-wk lead. +AD7528JN (ADI, pin-compatible original): UTSource used $0.68–0.72; **Taobao/华强北 spot ¥3/pc +(~$0.42) — user-verified 2026-07-16.** At ¥3 the whole 2,250-cell line is ≈$950; buy 2× and +screen down. + +## Phase 1 — screening batch (order NOW, ~¥300–600 total) +- 50–100 pcs × 2–3 DIFFERENT sellers (diversify counterfeit/batch risk). Keep seller lots separated + and labeled — per-lot pass rates decide where the volume order goes. +- Prefer sellers listing date codes / original reels or tubes; DIP (JN) package is fine for the + screening rig; note the volume build may want SOIC (AD7528JR / AD7628KR alternate footprint — + qualify both on the probe PCB). +- Red flags: freshly-blacktopped tops, inconsistent pin-1 markers within a lot, one price far + below the ¥3 street level. + +## Phase 2 — acceptance screen (Stage-1 single-column rig doubles as ATE) +Per-part functional screen, in order of kill power: +1. Basic DAC function: full-scale + zero code on both channels; reject hard failures. +2. System settle with 64-load column: **commit ≤3 µs; kill >7 µs** (pre-registered T64 gate). +3. ENOB after per-cell digital pre-scale calibration, 1-hr drift window: **≥7.0** — RELAX this + bar per the Stage-0 qup verdict (if 6-bit updates are lossless, acceptance drops to ~6 ENOB + and pass-rate rises). +4. Channel gain mismatch / INL spot-check at 4 codes (0x40/0x80/0xC0/0xFF): within the + forward/transpose asymmetry budget from Stage-0 gate #2 (pending). +Log pass-rate per seller lot; ≥70% pass at the relaxed bar makes the ¥3 line the plan of record. + +## Phase 3 — volume buy (after G1 + qup verdicts) +- 2,250 required + overage sized by measured pass-rate (default 2× at ¥3 ≈ ¥13.5k ≈ $1.9k). +- Fallback capped: TI TLC7528CDW new ($11.4k line) stays available (ACTIVE) — worst case 8× + price, zero schedule risk. +- Customs/compliance: 1980s commodity DACs, no export-control exposure; UTSource invoices work + for university reimbursement, Taobao spot = personal advance. + +## Do NOT spend effort on +Chopper choice, FRAM vs SRAM, PCB vendor substitutions — audited ≤2–3× movers. The money is in +this MDAC line (8–12×) and consumer-grade converter periphery (PCM1808 $0.90/ch ADC, +TLC5947 $0.17/ch DAC, 10–30× vs instrumentation-grade). |