Rev200 mods

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  • isolate current sensors from remainder of 5V supply.
  • overload latch circuit
  • high side current sense to include clamp

PCB needed Revisions

  • generate PDFs at 8.5x11 and mirror output when necessary.

IMU revisions

  • [1] (DONE) protect switcherwith resistor / TVS
  • [2] (DONE) protect ISP - R53-55 added.
  • [3] U5 change to 24LC128 (DFN8 still) or larger (512k available from digikey)
  • [4] (done) redo battery sensor circuit to not over voltage ADC
  • [5] on SC, route VBAT_PROT through newly added 200mA fuse to IMU connector J3 pins 1,2
  • [6] on FET change F1 (1210) to ~300mA - thus no chance of SC or IMU taking down the other.
  • [7] rework #4 - to make more accurate voltage measurement: raw "IMU_VIN" to Q7.S, replace R44 w/80k, replace C58 w/1nF resulting in 80uS tau (2khz BW)
  • [8] replace Z gyro filter cap C56 w/1nF - resulting in ~800hz BW
  • [9] (done) We'll keep R45 as show, which decreases the peek Z gyro rate (increase gain)

notes Oct 23

  1. use red PCBs
  2. where are we regarding the 12 x 0.8mm JST connectors?
  3. LDO voltage is 6.15V, use 0.1%, 97.6k, 24.9k
  4. for D13 use SDMK0340L
  5. primary coin cells BT1,BT4 can be removed
  6. pg 3 : ECO 14 - looks good.
  7. pg 3 : ECO 20 - can use 6 pin x 1mm ????
  8. pg 6 : ECO 15 - looks good.
  9. pg 7 : ECO 6,7,8,10 - looks good
  10. pg 7 : ECO 11 - disagreement over cut off freq
  11. pg 8 : ECO 12 - need to use 1nF for C148
  12. pg 8 : ECO 13 - populate R220,R222, R232, R233 - none should be DNP
  13. pg 11 : check drop cross D14, and coin cell voltage.
  14. pg 14 : wonder about this circuit and diode to 3.3V MC - should be SC to avoid loading.
  15. pg 15 : ECO 17, 18 implmented - but...
  16. pg 15 : wonder about this circuit and diode to 3.3V MC - should be SC to avoid loading.
  17. pg 17 : verify full bridge

discussion Mon Oct 5

  • regarding ECO 2016:
    • C2 can be decreased to 0.1uF, 50V - and will be a better high frequency filter as a result.
    • C19-21 have a maximum working voltage of ~9V. These could be replaced with 16V to 25V devices.
    • C60 won't exceed ~5V, 1.0u, 16V would be fine.
    • C101, C121, C136 = 0.1uF, 50V (same as C2 above)
    • C40, C62 has a 3.3V working voltage. 1.0uF, 16V would be fine

  • Regarding : ECO 2018 :
    • this is an input to the micro and requires no change to the associated input circuitry.
  • I don't believe that my ECO #15 was captured. This ECO changes the HALL_C input to a 5V CMOS level output. Thus D10A is removed and some sort of buffer or inverter from the 5V supply is inserted. Probably the Schmitt inverter (1200-000348) would work well for this.

discussion Sun Oct 4

  • overall our goal is it keep to a minimum the number of changes. The changes they we have proposed are absolutely necessary from our point of view.
  • changing 0.8mm headers to 1mm
    • We need to stay with the 12 x 0.8mm header for the pyramid, EC30 MILE, and IMU. Fortunally we need only 1 part number. The 5 position linear spring header can become 1mm
  • 4 Channel DAC
    • We would like this to remain.
  • Primary Li cells
    • We would like these to remain. We may wish to locate SMT cells for both primary and 2ndary, and ones that have lower height profile.
  • Current sensors :
    • We're aware of the linearity issue.
    • The present design with the current sensors can actually cause an over-voltage condition on the dsPIC. When this happens there are offset and cross coupling issues on all channels. The slight lose in resolution is minor compared with the upside.
  • Hall sensor should remain. The location of the sensor may change slightly.
    • The purpose of the connection to TP252 is so that we may experiment with alternative sensors. At present we don't have any.
  • IMU
    • I believe we would like to stay with the right ankle 12 pin x 0.8mm header. KS would like it moved down a few MM. We need to see the full V2 design to finalize this connector.
  • Temperature of coin cells:
    • We've monitored the temperature. However, I wasn't aware of the narrow temperature limitation of the cells. Clearly this could be an issue.


  • (1) w/clamp circuit - use thermal vias for R4 - this device is impossible to replace
    • will try low temp solder and send to MPD
  • (2) height of coin cells is too great. need the cells from this original coin cell specification
  • (3) pg 4/8 : populate coin cell charger as default
    • populate BT2,BT3 as default, DNP BT1,BT4 (but keep R18, D21)
    • DNP D13 only if primary coins are installed.
    • Would like the coin cells to have 6.0 to 6.1V to be fully changed. ABS maximum is 6.2V
      • It doesn't appear to be possible to obtain this tight voltage specification with 1% resistors and the (PDF) MIC5235 LDO. The LDO has up to 2% variation in its output over temperate. Thus a total variation of upto +- 3.65% could be expected.
      • 6.2 +- 3.65% = 5.98V to 6.42V
      • expect a 150-200mV drop across D13
  • (4) change D13 (and D21 ?) to diode that actually has 200mV drop @ 1uA. BAS116-F-7 appears to have 427mV @ 0.3uA
    • See : (PDF) - Diodes Inc BAS116-7-F fig 3, pg 2]

  • (5) pg 4/8 : ability to measure coin cell voltage without charger enabled? Connect pin 3 of U10 to something like the SFTYSNS_EN, or MTR_EN signal at TP97 or U20B


  • (6) pg 7/18 : change cutoff freq to ~15Khz for temp circuit (U22) R102=1k, C73=0.01u
  • (7) pg 7/18 : remove R232 - 10k for batt_temp_mon pullup (CEB - 10-13-09 - i think I mean R242)
  • (8) pg 7/18 : remove R245 - 220 ohm for mtr_temp_mon pullup
  • (10) pg 7/18 : R206, R216 -> 6.66k to scale range 0-5V to 0-3.0V (current sensors)
    • presently 5V @ current sensor becomes 3.283V, but ADC reference is 3.0V so of the 75.76A range (0->5V), only 69.23A are viable. Thus range is -37.88A to +31.34A. The scale factor is 65536 / (5/.066 * 3/(5*10/15.23)) = 946.6789
  • (11) pg 7/18 : bridge current sensor use same values phase U,V

  • (12) Pg 8/18 : increase size of resisters (by 10x) for supply voltage measurement (R91, R94, R221, R88). Keep cut off freq the same.
  • (13) pg 8/18 : populate so measurement of supply voltage is default (R222, R233 installed). its easier to remove components than to add them.

  • (15) pg 6/18 : replace HALL_C input with SSI_CLK (CMOS 5V) output.
    • Remove D10A
    • Insert Schmitt inverter (1200-000348) between MC and R86
  • (16) pg 11/18 : (CB) need to determine the accuracy of the RTC. Seems to be drifting.
  • (17) pg 18/18 : Remove LSSGA before TP56
  • (18) pg 18/18 : Connect TP56 to LSSGA connector. needs to protect dsPIC, but no other circuity.
    • adjust C95 for 15khz cutoff freq
    • appears on page 15
  • (19) pg 14/18 : Connect TP252 to LSSGA connector. Needs to protect dsPIC, but no other circuity.

  • (20) 3/18 : LSSGA connector signals:
    • AGND
    • A3V ref (analog 3.0V reference)
    • Various power source options such as Vbat(fused), 5.0V, 3.3V. The reference can't (shouldn't)
    • TP56 analog in
    • TP252 analog in
    • Hall_B input
  • (21) 11/18 : RTC coin cell isn't fully charged. Recommend connected D14 to the 3.3V supply.

  • locate IMU header for easier access. possibly rot180 - or move 2mm away from edge.
    • KS - lower position for V2.
    • CB - in V2 appears to be much more space in the shell, no other changes may be needed.


  • probably want to upgrade dual axis IMU
  • battery measurement circuit needs to be re-done.