Ho letto e consolidato la documentazione R2 e avviato lo schema Rev A. Il progetto ora contiene 53 componenti e 45 reti, inclusi nRF9151, nRF5340, power path, MAX17055 con reti Kelvin, collegamento SPI tra MCU, ES8388/I²S e catena RF 50 Ω.
Lo schema non è ancora pronto per il layout:
L’esecutore iniziale ha riportato 235 segnalazioni ERC.
Mancano ancora verifiche/completamenti per decoupling e pin riservati dei due MCU, shunt Kelvin reale, protezione batteria, consenso USB-C, watchdog/CE, NTC, matrici K1, PTT, UI, debug e test point.
Pinout OLED e alcuni dati meccanici restano non verificati.
Ho rimandato lo schema allo stesso esecutore con istruzioni precise per completare questi punti e ridurre l’ERC, ma non ho potuto recuperarne il nuovo rapporto finale.
Nessun placement, routing o layout PCB è stato avviato: procedere con uno schema ancora non verificato sarebbe rischioso.
Il prossimo passo è recuperare il risultato dell’ultima correzione, eseguire una review indipendente dello schema e, solo dopo ERC accettabile, configurare il PCB JLCPCB a sei strati e iniziare placement e routing.
L’esecuzione si è fermata perché gli ACUs sono terminati.
Non ho potuto recuperare né riconciliare il report dell’executor “Beltpack Schematic Rev A”, quindi non posso confermare che lo schema sia corretto o pronto per il layout. In questa sessione non sono state apportate ulteriori modifiche a schema o PCB.
Restano da completare:
verifica indipendente di componenti, collegamenti, alimentazioni ed ERC;
confronto dello schema con i documenti di specifica allegati;
correzione degli eventuali errori;
definizione del budget di potenza;
solo dopo la validazione dello schema: stackup JLCPCB a 6 strati, profilo scheda, placement, vincoli RF/antenna e routing controllato;
checkpoint di approvazione tra schema verificato e layout.
L’esecuzione si è fermata perché gli ACUs disponibili sono esauriti.
Status: Phase 2 battery-management selection reconciled with the locked Rev A mechanical path. No schematic capture has started.
Scope: compare the requested fuel gauges and charger / power-path ICs for a single protected removable 18650 Li-ion beltpack powered and charged from USB-C 5 V, assembled by JLCPCB using standard 6-layer controlled-impedance capabilities.
Executive Decision
Recommended Rev A battery-management pair:
Fuel gauge: MAX17055ETB+T.
Charger / power-path IC: BQ25895RTWT or same RTW package ordering variant available for assembly.
Holder: MPD BK-18650-PC2, THT removable-cell path; assembly stock must be confirmed or the holder hand-installed/consigned.
The MAX17055 gives more useful runtime diagnostics than the MAX17048 while avoiding the heavier TI Impedance Track configuration burden of the BQ27441/BQ27542 family. The BQ25895 is the best fit among the charger candidates because it is single-cell focused, mature, available in the Flux/JLCPCB/LCSC ecosystem, supports switch-mode charging, has NVDC-style power-path behavior, and avoids the unnecessary 1-4 cell / PD / MPPT complexity of BQ25792 and BQ25672.
Important constraint: USB-C 5 V / 3 A input is a source capability, not a default charge current. Rev A should start at 1.0-1.5 A charge current and allow 2.0 A only after cell datasheet, enclosure thermal, and USB-C current-advertisement validation.
PCB / JLCPCB Manufacturing Assumptions
Use JLCPCB standard capabilities only:
Manufacturer: JLCPCB.
Material: Shengyi S1000-2M.
Layer count: 6.
Nominal board thickness: 1.6 mm unless mechanical design changes it.
Finish: ENIG.
Via technology: through vias; epoxy-filled and capped vias are allowed if ordered as a JLCPCB standard capability.
Controlled impedance: yes, using a standard JLCPCB 6-layer stackup.
Do not use exotic PCB technologies: no blind vias, no buried vias, no HDI microvias, no unusual materials, no nonstandard copper weights unless specifically justified.
The screenshot shows standard JLCPCB 6-layer 1.6 mm stackup options such as JLC06161H-3313, JLC06161H-7628, JLC06161H-1080, JLC06161H-2116A/B, JLC06161H-3313C/D/E, JLC06161H-1080A/B, and JLC06161H-7628A/B. Final stackup should be chosen during RF/USB/layout setup using the JLCPCB impedance calculator so the 50 ohm DECT RF feed and any USB 2.0 differential pair geometry match the actual copper/core/prepreg option.
Preliminary Power Sizing Check
The Phase 1 power budget estimated normal mixed-use system power around 0.65-0.95 W, continuous coordinator/relay around 1.0-1.5 W, and worst continuous TX/RX around 1.5-2.0 W.
For USB-C 5 V input with a switch-mode charger:
Table
Case
Battery charge power
Approx input current for charging at 90% efficiency
Add system load from USB
Planning interpretation
1.0 A at 4.2 V
4.2 W
0.93 A
~0.2-0.45 A
Easy on 5 V / 1.5 A or 3 A source if thermals pass.
1.5 A at 4.2 V
6.3 W
1.40 A
~0.2-0.45 A
Good Rev A target with Type-C current awareness and thermal testing.
2.0 A at 4.2 V
8.4 W
1.87 A
~0.2-0.45 A
Possible from 5 V / 3 A source, but enclosure and cell temperature dominate.
3.0 A at 4.2 V
12.6 W
2.80 A
~0.2-0.45 A
Not appropriate as a default; exceeds or crowds 5 V / 3 A once system load and losses are included.
Rev A design target: configure the charger and firmware so the default charge current is conservative, then expose test points and telemetry to validate higher current safely.
USB-C implementation note: a USB-C receptacle with only Rd pull-downs cannot assume 3 A from every source. Either add a simple Type-C current-detection controller or set the input current limit conservatively until firmware can identify the source capability.
Fuel Gauge Comparison
Table
Candidate
Type
Strengths
Risks / drawbacks
JLCPCB / Flux status
Rev A decision
MAX17048
ADI/Maxim 1S ModelGauge, voltage/model-based, no sense resistor
Very low hardware complexity, low current, I2C, tiny TDFN option, no current shunt, easy bring-up
Less robust under pulsed RF/audio loads, aging, temperature variation, and removable-cell uncertainty; reports less diagnostic current/capacity detail
Flux library match found: MAX17048G+T10, LCSC Extended, TDFN option
Keep as low-risk fallback only
MAX17055
ADI/Maxim 1S ModelGauge m5 EZ with current sensing
Better SOC robustness, voltage/current/SOC/capacity/time-to-empty/age reporting, no heavy learning workflow, I2C, TDFN package
Needs sense resistor, Kelvin routing, and more careful layout than MAX17048
Flux library and LCSC matches found: MAX17055ETB+T, TDFN-10, LCSC Extended
Recommended
BQ27441
TI system-side Impedance Track gauge for 1S Li-ion
Mature TI gauge, system-side use, SOC/SOH/capacity, I2C, JLC/LCSC availability
Requires sense resistor and TI gauge configuration/chemistry workflow; more firmware/bring-up effort than MAX17055
Flux library match found: BQ27441DRZT/DRZR variants, LCSC Extended
Viable alternate if TI gauge ecosystem is preferred
BQ27542
TI pack-side Impedance Track gauge for 1S smart packs
Powerful pack-side feature set, high capacity range, authentication/logging features
More appropriate inside a smart battery pack than on the beltpack PCB; highest configuration burden; unnecessary for Rev A
Flux library matches found, LCSC Extended, but fewer options
Avoid for Rev A
Fuel Gauge Recommendation
Use MAX17055ETB+T for Rev A.
Design notes:
Place the gauge near the battery connector and current-sense resistor.
Use Kelvin connections for CSP/CSN sense routing.
Use a low-value precision sense resistor in the battery current path; 10 mOhm is a reasonable first planning value subject to datasheet/reference-circuit confirmation.
Keep gauge sense traces away from charger SW node, inductor, and high di/dt loops.
Add test points for BAT+, BAT-, gauge I2C, ALERT, and the sense resistor Kelvin nodes.
Firmware should log voltage, current, SOC, remaining capacity, and temperature during charge/discharge/radio tests.
Use MAX17048 only if schedule risk matters more than SOC robustness and the product can tolerate an approximate battery indicator.
Charger / Power-Path Comparison
Table
Candidate
Topology / role
Strengths
Risks / drawbacks
JLCPCB / Flux status
Rev A decision
BQ25792
TI 1-4S 5 A buck-boost charger, NVDC, USB-PD OTG capable
Very capable, wide 3.6-24 V input, 5 A charge, integrated ADC, USB-PD/PPS-friendly OTG, high integration
Overkill for 1S 5 V charging; more pins/registers/layout complexity; unnecessary unless >5 V input, 2S-4S pack, or advanced OTG is required
Flux library and LCSC matches found: BQ25792RQMR, QFN-29, LCSC Extended
Avoid for Rev A unless PD/multicell requirement appears
BQ25895
TI 1S 5 A switch-mode charger with power path and OTG boost
Single-cell focused, mature, I2C, input current limit, NVDC-style power path, OTG boost, 4 mm QFN, good JLC availability
Still a switching charger requiring disciplined layout; USB-C CC/current detection is external
Flux library and LCSC match found: BQ25895RTWT, WQFN-24, LCSC Extended
Recommended
BQ25672
TI 1-4S 3 A buck charger with dual input, MPPT, ADC
Modern, integrated ADC, dual-input and MPPT useful for solar/multisource designs
Not aligned with simple 5 V USB-C 1S design; multi-cell/MPPT complexity; buck topology/input requirements are less attractive for 5 V-only charging
MPS 1S 4.5 A switch-mode charger with NVDC, OTG, ADC, I2C
Functionally attractive single-cell charger, compact QFN-26, good feature fit on paper
Not found as a usable Flux library part; weaker JLCPCB/Flux ecosystem confidence for immediate schematic capture; would require part creation/import
Web-confirmed part exists, but Flux library search found no usable match; missing-part request filed
Avoid for Rev A unless user specifically wants MPS path and accepts library creation
Charger Recommendation
Use BQ25895RTWT for Rev A.
Design notes:
Use switch-mode layout exactly following the TI reference layout: tight input capacitor loop, compact SW node, inductor adjacent to SW, short BAT/SYS current path, and solid thermal-pad copper.
Keep SW/inductor copper away from MAX17055 sense traces, audio codec input, microphone bias, and RF feed.
Add NTC / JEITA battery temperature monitoring; do not rely only on protected-cell internal protection.
Expose charge status, fault, I2C, SYS, BAT, VBUS, PMID, and NTC test points.
Add firmware control of input-current limit and charge-current limit.
Add USB-C CC handling outside the charger. For Rev A, a simple Type-C current detector is preferred over a full USB-PD controller unless later power requirements justify PD.
Default charge current should be 1.0-1.5 A. Allow a 2.0 A firmware/test option only after thermal validation.
Why Not USB-PD / Buck-Boost by Default
The beltpack uses one protected 18650 cell. A 5 V / 3 A USB-C source can provide up to 15 W before cable/source losses, which is already enough for conservative 1.0-2.0 A single-cell charging plus system operation if current advertisement is respected.
A PD buck-boost charger such as BQ25792 becomes justified only if one of these requirements is added:
9 V / 12 V / 15 V / 20 V USB-PD input is required.
Charging above the practical 5 V / 3 A budget is required.
The battery pack changes to 2S-4S.
The device must source high-power programmable USB-C OTG.
Dual-source or adapter-management requirements exceed BQ25895 capability.
None of those are currently required for Rev A.
Recommended Rev A Power Architecture
Diagram
Schematic Capture Implications
Add these parts and support circuits in the power block during schematic capture:
BQ25895RTWT charger/power path.
MAX17055ETB+T fuel gauge.
USB-C receptacle with CC handling and ESD.
Input protection / fuse strategy sized after the full power budget.
Charger inductor, input/output/BAT capacitors, bootstrap/support parts, NTC network, and status/test pins per TI reference design.
MAX17055 sense resistor, decoupling, I2C pull-ups if not shared, ALERT net, and test points.
Battery connector/holder strategy with reverse-insertion and serviceability review.
Current-measurement jumpers or 0 ohm links for BAT and SYS if they do not compromise high-current paths.
Before freezing charger passives, complete the detailed rail-by-rail power budget and reflect all loads through SYS/VBUS at worst-case input and charge conditions.
Open Validation Items
Obtain a lot-specific KeepPower P1835J charge specification or written manufacturer confirmation before enabling 1.5 A as normal; retain 1.0 A default and 2.0 A engineering-only.
Prototype-gate exact P1835J fit in BK-18650-PC2 and establish holder current/contact performance; available holder documentation does not state a current rating or an unambiguous 69.25 mm maximum accepted length.
Maintain compliant cell-surface NTC contact across insertion/removal cycles and preserve at least 25 mm battery-to-antenna clearance.
Do not substitute MYOUNG C2988620; protected button-top and 69.25 mm compatibility is not demonstrated.
Decide whether Rev A uses simple CC Rd resistors plus conservative input current, or a Type-C current-detection controller.
Run charger thermal simulation/bench test at 1.0 A, 1.5 A, and 2.0 A in enclosure-like conditions.
Validate MAX17055 SOC accuracy under DECT NR+ TX/RX bursts, OLED activity, audio amplifier load, and removable-cell swaps.
Confirm JLCPCB stock/assembly class at time of BOM lock; all selected active ICs are Extended-class candidates today, so availability must be rechecked before ordering.
Select final JLCPCB 6-layer stackup and controlled-impedance geometry before RF/USB layout.
Sources / Evidence
ADI MAX17048 product/datasheet: 1-cell ModelGauge fuel gauge, I2C, 3 uA hibernate, no sense resistor, TDFN/WLP packages.
ADI MAX17055 product/datasheet: 1-cell ModelGauge m5 EZ fuel gauge, I2C, current/voltage/SOC/capacity/time reporting, TDFN/WLP packages.
TI BQ27441-G1 datasheet/product page: 1S system-side Impedance Track fuel gauge, I2C, VSON-12, 200-8000 mAh class.
TI BQ25792 datasheet/product references: 1-4S 5 A buck-boost charger, I2C, dual input, USB-PD OTG, QFN-29.
TI BQ25895 datasheet/product references: 1S 5 A switch-mode charger with power path, I2C, boost/OTG, WQFN-24.
TI BQ25672 datasheet/product references: 1-4S 3 A buck charger, dual input, MPPT, ADC, QFN-29.
MPS MP2731 product/datasheet references: 1S 4.5 A switching charger with I2C, NVDC power path, OTG, ADC, QFN-26; not currently found as a usable Flux library component.
Flux library searches confirmed usable matches for MAX17048, MAX17055, BQ27441, BQ27542, BQ25792, BQ25895, and BQ25672. MP2731 was not found in the Flux library and a missing-part request was filed.