Cape v2.0 - PCB Changes

General rule for assembly-drawings

  • origin orientation

    • keepout

    • assembly notes (mech15)

  • designator

    • keepout

    • top designator (mech 2?)

  • Copper / Silk

    • L1 Pads / Via

    • Keepout

    • Top Overlay ⇾ print in Color

Implemented Changes v2.0r0

  • 4 Layer! Planes for Sig, GND, A5V, (3V3)

  • decide Manufacturer, EC, Aisler, Betalayout

  • add design rules

  • add layer stackup

  • add default vias

  • divide in groups / rooms

  • optimize surroundings of ICs

  • change vias of pson50, dfn-10 (by lt3487 spec)

  • move lvlchangers to the left

  • change pads of pinheaders in inner layers

  • thermal pad of switch unused? yes, no word of use in datasheet

  • increase restring / holesize, sheph seems to have 0.15mm holes?, target 0.075 ring

Implemented Changes v2.0r1

  • Beaglebone

  • Emulator

    • DAC

      • previous: DAC8562SDGSR, mouser 595-DAC8562SDGSR

        • 50 MHz SPI, 7-10 us Settling, 1-4 mV Zero-Scale-Error, 40 mA Short-Circuit-Current,

      • constraints: >= 16 bit, SMD, 2 CH, not maxim, v-range ~2.5…5.5 V, short settling time

        • this could also be low-res and slow for only bq-output-sim, but it would benefit to also tap in cap-voltage directly

        • https://www.mouser.de/Semiconductors/Data-Converter-ICs/Digital-to-Analog-Converters-DAC/_/N-4c44d?P=1z0w8k6Z1z0w2wwZ1z0w2wvZ1z0w2wtZ1z0z7ptZ1yz5pwlZ1yzmm10Z1yzml2aZ1yzmm18Z1yzmlprZ1yzmm0yZ1yzmm13Z1yzmlr9Z1yzmlh1Z1yzmlwtZ1yzmm16Z1yzmm0zZ1yyh4l4Z1z0zls6Z1yzxao2&Ns=Pricing%7c0

      • replacement: AD5663ARMZ-REEL7, mouser 584-AD5663ARMZ-R7

        • 50 MHz SPI, 4 us Settling, Zero-Scale-Error<1mV, 30mA Shor-Circuit-Current, needs voltage reference, WATCH OUT - there are versions with midpoint-start

      • replacement: DAC8830, 1-CH, 50 MHz, 16bit, 10nV/sqrtHz, 1us Settling,

      • replacement: AD5545B, 2-CH, 50

    • OpAmp for V-BUF 2CH?

      • previous: OPA2388IDGKT, digikey 296-50277-2-ND

        • 30-60 mA perm, 5 V/us, 7 nV / sqrtHz, 0.25 uV Offset,

      • constraints: opAmp, 3CH, supply ~ 3-5 V, Rail2Rail

        • https://www.mouser.de/Semiconductors/Integrated-Circuits-ICs/Amplifier-ICs/Operational-Amplifiers-Op-Amps/_/N-6j73m?P=1yzxao0Z1yzmm18Z1yzmm0xZ1yzmm13Z1yzmm14&Ns=Pricing|0

      • replacement: AD8606ARMZ-REEL, mouser 584-AD8606ARMZ-R

        • 2CH, 80 mA, 5 V/us, 8 nV/sqrtHz, 20 uV Input Offset,

    • shunt-Resistor

      • nRF52 takes 9 mA @ 4dBm, 16 mA @ 8 dBm for ~ 200 us, rest is below 2 mA,

      • previous: 2 Ohm 1% ⇾ 16 mA => 32 mV, would mean 1% Voltage drop at 3V3, less would be better

      • current sensors are no alternative, too expensive, not enough resolution

      • replacement: 1 Ohm 0.1% ⇾ 1:1 mA:mA, 0603 or 1206

        • RT1206BRD071RL, mouser 603-RT1206BRD071RL

    • OP-Amp for Shunt

      • previous: AD8422BRMZ in combination with LM27762DSSR

      • constraints: 1 CH, > 2 MHz Gain-BW-Product, Supply ~ 2-5 V, >75 dB CMRR, Low input offset voltage

      • replacement: INA331AIDGKR, mouser 595-INA331AIDGKR, in combination with LM7705 (-0.23V) on V-, mouser 926-LM7705MMX/NOPB

        • ref: https://e2e.ti.com/support/amplifiers/f/14/t/700003

      • proper replacement: ad8429B

        • https://tools.analog.com/en/diamond/#difL=0&difR=0.05&difSl=0&gain=100&l=0&pr=AD8429&r=5&sl=0&tab=1&ty=2&vn=-8&vp=9&vr=0

        • https://training.ti.com/system/files/docs/1312%20-%20Noise%202%20-%20slides.pdf

    • ADC 2CH

      • previous: ADS8694TSSOP38 4 CH

        • 18 bit, 4 CH, two V-Rails for A&D, 500 kSPS, 18 MHz SPI, variable LPF, 1175 ns Acq & 825 ns Conv.

      • constraints: 2CH, 18-24 Bit, SMD, >100 kSPS

      • replacement: ADS8691, 1CH 1 MSPS 8€, ADS8695 1CH 500kSPS 9€, ADS8699 1CH 100kSPS 6€, Acq 335/1000/5000ns, Conv 665/1000/5000ns

    • analog switch ⇾ is there a way to power the offline target? Switch up supplies

      • previous: TMUX1101DCK, 4 Ohm, 1 SPST SinglePole-SingleThrow

      • constraints: 2 Ch, legs, supply >= 5, rdson <= 500 mOhm,

      • replacement: NLAS4684MR2G, mouser 863-NLAS4684MR2G, 2CH, 300 mA Conti, 500 mOhm rds

    • Target-Port-IO (GPIO, SPI, I2C, UART, SWD/JTAG, BAT_OK PRU) ⇾ Q: is HS-GPIO enough? rest is userspace-logged

  • debug to target

    • voltage-level-translator,

      • previous1: TXB0304RUTR BiDir, autosense, min 3mA input drive current, 4 CH, >40 Mbps

      • previous2: SN74LV4T125PWR UniDir

      • constraints: 1 Mbps, high channelcount, autosensing, 2-5V, HighZ-Mode

      • replacement: NXS0108PWJ, mouser 771-NXS0108PWJ, 50 Mbps, BiDir, Autosense, open drain, 8 Bit, NXB-Version: 2mA input drive req.

        • ⇾ WARNING: expected 18.01.2021, nxs0101 already in stock, nxs0102 in may

  • target-port ⇾ default pin-header, maybe smaller version of it

  • suppply for second target ⇾ 2. CH of DAC + Buffer

  • status-Leds

    • green 575nm, 0603, 60mcd 2V@20mA, 150060VS55040, mouser 710-150060VS55040

    • blue 470nm, 0603, 80 mcd 3.2V@60mA, 150060BS55040, mouser 710-150060BS55040

    • red 645nm, 0603, 70 mcd, 2V@20mA, 150060SS55040, mouser 710-150060SS55040

    • orange 605nm, 0603, 100 mcd, 2.2V@20mA,

  • LEDs for current active (and powered) Target

  • multipurpose nChannel MosFet

    • constraints: <50mOhm, smd, n-CHannel, VGS <=700mV

    • sot-323-3: DMN2058UW-7, mouser 621-DMN2058UW-7

  • i2c-storage, prev: CAT24C256WI-GT3

  • Cage

  • Part Properties:

    • price (for ten), manufacturer, manufacturer id, shop 1, shop 1 ID, …

    • special properties: max voltage, power, current, size / package, color, forward Voltage

  • extra information (i2c-adress, spi-speed, ) directly in schematic

  • power-recording-stage

    • DAC DAC80501ZDGSR

    • OPAmp OPA388ID, pin-compatible with LTC2050HV

    • nMOS SI2374DS, test with BSH103

    • ShuntOPAmp Ina190A1IDCKR

  • power in via vdd_5v (P5/6) ⇾ Test shows: BB does not power up via sys_5v

  • reboot / boot via Pin-Toggle (Shutdown via command), we should trigger both (RESn⇾PD,PWR⇾PD), Test shows: Reset works while PWR is in PD

  • add 256 GB USB-Stick

  • switch to smaller IC-Packages and 0402

  • order / add GPS

  • is the gps capable of alarm (wake up sys)

  • our 5V analog should be stabilized more! Add A5V with 2 Stage Bead, or real coil

  • add footprint for layer-windows

  • add footprint for shepherd-logo

  • give INA190 a negative supply (>1mV would be enough) on GND-pin, ref stays on common gnd, extra decouple

  • Debug-Pins with Ground

  • extend harvest-Port, add option to measure VSense, and output VCap (V_A of Emulator)

  • it would be wise to detach a5v even further from 5V, with a low-drop diode

  • EMI-guard SPI, currentlimit at pinheader, terminate at ICs, 33 Ohms close to cpu recommended (avoid reflections)

  • add alarm-feature, something SPI-programmable, that can act like a watchdog, with at least max 1-4h windows

  • check against shepherd v1.5

  • don’t shut down individual Emu / Rec - Parts (delete or just disable all at once) ⇾ done by Pwr-control

  • Harvester needs second channel ADC with very low input current, 1MOhm is too low

  • manual button with LED ⇾ connector S4B-ZR-SM4A-TF, P1 3V3, P2 LED ODrain, P3 SenseButton with PU, P4-6 GND

  • add ultra low noise LDO to A5V, and possibly a boost-converter upfront

  • find better level translator, less current (best if near 0)

  • reprocessed 11_concept.file

  • switched Ina190 for AD8421

  • added boost/Inverter for proper voltage rail

  • add target port (comparator-include?) System will be a nRF52840 and most likely a MSP430

    • try to make it compatible with breadboard / dev-Kit

    • is spy-by-wire physically compatible with swd ⇾ it is, TClock is uni-dir, TDIO is bi-dir

  • replace 100nF/16, 1uF/16, 10uF/16

  • BOM, more precise alternative - BB uses 32.768 kHz osci MC-306 (20 ppm, 8x3.8mm) or similar, package says 327A5M

    • alternative: 5 ppm, 12.5pF, 50 kOhm, https://www.mouser.de/ProductDetail/Citizen-FineDevice/CM200C32768HZFT?qs=rkhjVJ6%2F3ELrGt3qchcVtQ%3D%3D

    • BB also uses 24.576 MHz

  • check output limits of opax388 and DAC

  • compare lowNoise LDO to LM27762

  • 750 kOhm 1%, 667-ERJ-2RKF7503X, 5 + 32

  • connect BB-Pins, 500 Ohm to input pins that could be driven from both sides

  • complete ERC

  • 1uF/16V is still 0603, change to 0402, there are 34x (incl. Recorder)

  • redistribute capacitors

  • replace coil with smaller one, check recommended direction

  • add 1kR & 100R high precision for current measurement, EMU

  • order digikey (extBut, samtec), mouser, csv

  • add footprint for quality-control-panel

  • BB Pinheader Cape-Design Stays ⇾ possible alternaltive Producer is Samtech, design is now divided

  • add production-constraints

  • update BOM

  • v2r1 ordered

Implemented Changes v2.0r2

  • silkscreen - 10k array are 1k

  • 3d-Step: shield transparent for better view below

  • silk. “P3” designator is below component

  • pads of 0402 bigger, 1.2x1.2 as min area for pads? paste 0.8x0.8? got some tombstones on current revision

    • half a pad distance to neighbour (keepout)

  • improve connection betwenn pads (esp. 0402)

  • feducial seems massive, shrink it?

  • SPI-CS with at least 33R to lower chance of interference

  • R for BatteryGood is wrong (handled by PRU), should it also be routed to userspace?

  • TC7WH-Footprint is to large

  • HC2G-comment (Name) is wrong / twisted

  • DAC pads could be longer, reach more under the IC

  • MP32 has no dot on package, just [ABC], lower left is pin1

  • NSR (or all diodes) could get a line on the 3d-file (current dot is confusing, because the actual package has line and dot)

  • the orange led is red! … bad UI for general blinking

  • describe gain of OP-Amp in schematic

  • 100R, accuracy is missing in description / constraints

  • Silk for L9/L10

  • essential silk-numbers on headers can be bigger/bold, a bit more distance from header

  • rename rec to harvest, port on pcb more obvious

  • harvest dAC ch-b - drain power source OK?

  • improve marking on Voltages, maybe with an arrow

  • reverse diode of mosfet is too weak - already destroyed the reverse polarity protection

  • some popular Flag-Markers on backside for pinheader

  • Pin1 dot should be a shallow/sharp triangle, pointing in the right direction (less confusing in dense layouts)

  • transistor-footprint is not conform to datasheet, it is slighly bigger and just misses the pads?!?

  • u13 thermal to wide, reduce a bit to avoid shorts (u15 has same possible weakness)

  • rework als Pin-Descriptions (already mentioned)

  • round and divided (big) paste pads

  • add general power-led when shepherd is on? maybe on 6V line

  • switch to thinner stencil, bigger pads (paste is good for it)

  • header-row on target has paste, it should not

  • Font/Writing in copper is unreadable on target (slighly below spec)

  • add layer for manual / pick’and’place descriptions (m15, m?)

  • qr code is not readable, blurred, reduce size of “pixel”

  • warning for harvest V_sense ⇾ Voltage floats if not connected and will most likely show V-Max in this state

  • ADC nRST should not get A5V, only 3.3, also there is no need for a resistor-switch

  • Connector for external switch was copied from old schematic, but this one had inversed pin-numbering on connector, different from datasheet

  • Testpoint on RVS-Pin of

  • protect GND better around Pinheaders

  • U25A, Inputs are switched

  • diode between both 5V-lines should be two diodes that feed the watchdog

  • 3V3 should also be switched - maybe even the 5V0 in, so the PU that hinder bootup are meaningless

  • vias came back only weak tainted (make it less severe if that happens), mainly for target pcb

  • more distance to gnd-plane (soldering is hard, even with thermals

  • TEST Watchdog, make compatible with BB

  • TEST GPIO to and from target

  • same orientation for transistors

  • switch p8-27 and 29 (batOK / GPIO4) for cleaner readout

  • switch p8-43/44 with p8-39/40 for proper boot

  • TEST boot with all pins except 3v3 & 5V

  • but make sure that shepherd-EN (p8-13) stays low during boot

  • switching main power to both targets shows, that the routes seem to have different current-readings for the same load! odd

  • 1k for LEDs

  • check surroundings of mosfets, size has changed

  • mosfet of watchdog-wake could be tied to 3V3 with additional 1k resistor or diode (so that button stays usable)

    • 100k PD for wd-pin (or keep 10k)

    • 3V3 goes low on powerdown, so watchdog can enable (pull low wake) BB again,

    • polling has no effect during normal operation

    • TEST if 1k is enough to pull line low to enable ⇾ it is

  • add open source hardware logo?

Schematic Changes - Open

  • prepare calibration

  • ordered not enough 15uH Coils, need 30 more

  • check remainder of BOM for emu-only assembly

  • shepV1 had a user-space led, which is still there, same pin, but pru-controlled, was it the same in v1?

  • explain schematics,

Part Changes

Note: after Mouser-Order - NOW already ordered

  • DAC 100nF ⇾ 1uF

  • Boost 10uF ⇾ 10uF (inv)

  • Inv +47uF

  • Rec 2x 10k 0603 ⇾ 0402

  • All 34x 1uF/16V/0603 ⇾ 1uF/25V/0402

  • final Shield, cover & frame

  • all 4x 15uH/4mm ⇾ 15uH/3mm

  • parts of nRF-Target

Schematic Changes Postponed

  • internal calibration? with 2 switches and 1 calibration-linear-power-supply

  • OP-Amp, bias Subtractor: LMP7701MF, not needed now

  • sync to pps ⇾ external pcb

  • usb-socket is impossible to hand-solder right now

  • (maybe) add PU to watchdog outputs

  • separate PCBs for PPS-Source, Recorder, Emulator

Open Issues

  • only 5 diodes of type PMEG in order?

  • change 100 uF to 47u? one less component

  • Testpad should be square for GND, half-circle for Signal or similar

  • r3 (dac, emu)

  • proper naming for TP if there is space

  • TPs should have bigger hole, so probes stick

  • oscillating opAmp should be outside of cage

  • allow install of a big cap on A5V or 5V, 5v5 1F is cheap

  • add longer pinheader for p8/p9 23-46