PCB needed Revisions

discussion

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

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

(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

(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.

(14) pg 3/18 : replace 1.25mm header for EC30 enc/hall w/ 12x0.8mm header
- [12x8 pinout]
- interface cable

(16) pg 11/18 : (CB) need to determine the accuracy of the RTC. Seems to be drifting.

(18) Connect TP56 to LSSGA connector. needs to protect dsPIC, but no other circuity.
- adjust C95 for 15khz cutoff freq
(19) pg 14/18 : Connect TP252 to LSSGA connector. Needs to protect dsPIC, but no other circuity.

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.