Owner: @Hardy Yu @Nolan Haines

Other peripherals on tracking antenna pcb: Tracking Antenna Status & Mechanical/Electrical Components

Power Analysis

XBEE

Voltage: 2.8-3.4V
Max Current: 50mA (regular version), 250mA (pro version)

RFD900

Voltage: 5V
Max Current: 1A

BMX160

Voltage: 3.3V
Max Current: 1.6mA

TBS m8.2

Voltage: 3.3V
Max Current: 21mA

Servo

Voltage: 5V
Max Current: 1.5A

Nucleo

Voltage: 5V
Max Current: 500mA

Features & Design

26V Reverse Polarity Protection - @Nolan Haines

Daniel made a nice write up about RPP for anyone interested: Reverse Polarity Protection Circuits

Leaning towards the Schottky diode solution for RPP. I think this makes sense to reduce cost and complexity, given that for most cases RPP is already accomplished mechanically by the XT60 connectors (which are designed to physically block any reverse connection). I don’t think power consumption is a huge issue in this situation since we’re plugging in 6S batteries which gives us quite a bit of leeway for that.

If we’re going this route, here’s a diode that I think will work: (https://www.digikey.ca/en/products/detail/vishay-general-semiconductor-diodes-division/V6PWM45-M3-I/16683185)

110 C

Recalculation:

For 6A in ambient temperatures, Vf max is 0.58V

P = 6*0.58=3.48W

Thermal resistance = 65C/W

Temp rise = 3.48W*65C/W = 226.2C

We should evaluate this option again

High Side Switch Driver Option

IC: LM74502DDFR

https://www.digikey.com/en/products/detail/texas-instruments/LM74502DDFR/15904171

3.2V-65V input voltage range
Up to -65V RPP

2x High Side NMOS

https://www.digikey.ca/en/products/detail/alpha-omega-semiconductor-inc/AON6236/3060849
Low RDSon (~7mOhm)
40V Vds
+/- 20V Vgs max
Large Id (>15A)

Overvoltage protection

AOZ2261NQI-12 buck has max VIN of 28V
6S full battery is ~25.2V
Set OVP to 27V using

R1 = 100k, R2 = 4.87k (https://www.digikey.ca/en/products/detail/yageo/RC0603FR-074K87L/727217)
- Sets voltage limit to 26.92V
R2 not standard, but there is not too much wiggle room between minimum and maximum voltage that OVP can be

Charge Pump VCAP

Need to be able to charge input capacitance of both FETs
Input capacitance of AON6236 is 1.225nF
- minimum capacitance is 2*1.225*10 = 24.5nF
- Use 100nF capacitor

EN/UVLO

Will use this feature to shutdown the board when a battery lipo cell reaches 3.2V and do low battery indication when battery cell reaches 3.4V

LDO
- https://www.digikey.ca/en/products/detail/texas-instruments/TLV76050DBZR/7402852
- 30V max input, 5V fixed output
- 100mA
  - Will need to validate/calculate how much current voltage cell detection requires
Differential Opamp
- https://www.digikey.ca/en/products/detail/texas-instruments/LM124DR/644185
Hysteresis Comparator
- https://www.digikey.ca/en/products/detail/texas-instruments/LMV7231SQ-NOPB/2434909
  - More likely to use this for undervoltage protection + low battery indicator
    - CO1-CO6 are pulled low when one voltage cell goes below 3.2V
    - COPOL determines if CO1-CO6 go low or go high when the cell voltage is below 3.2V or above 3.4V. Tie COPOL to low.
    - AO goes low when either all the voltage cells are below 3.2V or all the cells are above 3.4V
    - AOSEL determines whether AO goes low when all cells are below 3.2V (tie AOSEL to low) or all above 3.4V (tie AOSEL to high)
      - Basically, CO1-CO6 going low indicates battery is crtitically low and will shutdown and AO going high means at least one voltage cell is below 3.4V (low battery)
  - Use the following case to calculate resistors for window
    - Let dead cell voltage (Vuv) be 3.2V and low battery (Vov) be 3.4V. Differential opamps have a gain of 1/2 so input Vuv and Vov will actually be 1.6V and 1.7V.
    - R3 = 10k
    - R2 = 10k(1.7/1.6-1) = 625
      - Use 620
    - R1 = 10k((1/0.394)1.7-1.7/1.6) = 32.522k
      - Use 32.4k

Input/Output Caps

Use 0.1uF input decoupling
Use typical 220uF output cap

Overcurrent Protection - @Nolan Haines

IC: TCKE812NA,RF

https://www.digikey.com/en/products/detail/toshiba-semiconductor-and-storage/TCKE812NA-RF/12324959

5V buck has 5A current limit implemented
12V buck has 3+A current limit implemented for short circuit conditions
Motor Overcurrent protection
- Same IC as 12S servo module
- Have one overcurrent IC for each motor. Limits current to 1.5A per motor using R18
- C34 controls voltage slew rate which limits inrush current
  - Assuming (worst case scenario) that output capacitance downstream is in the order of 100uF,
  - 1nF cap for dV/dT should safely avoid any OCP triggering

Low Battery Indicator - @Hardy Yu

Requirements:

Show the state of the battery without software dependency
Turn on a red LED light when the battery drops down to a dangerous voltage
Tunable voltage threshold achieved by potentiometer

Component Selection:

IC - @TL431

TI: TL431ACDBZR

Highlights:

Cheap, simple, small, and provide voltage reference

10K trimmer potentiometer - @ST-32ETA103

Digikey:https://www.digikey.ca/en/products/detail/nidec-components-corporation/ST-32ETA103/738168

Circuit Idea:

25 to 5V Buck @ 5A - @Nolan Haines

Voltage input 26 ~ 15V
Output Voltage - clean 5V
Max Current @ 5A

Options:

Final IC chosen: https://www.digikey.ca/en/products/detail/alpha-omega-semiconductor-inc/AOZ2261NQI-12/16265489

Data sheet: https://aosmd.com/res/data_sheets/AOZ2261NQI-12.pdf

Unless otherwise specified all formulas used here are from the data sheet

Caps:

Input Capacitor (C2): https://www.digikey.ca/en/products/detail/murata-electronics/GRM188R61E225KA12J/4905350

∆V_in = 0.03*Vi = 0.75V; Io = 5A; f = 425kHz (see RTON calc below); Cin = ?

Apply formula 6 on page 12 of the datasheet.

Cin = 2.5uF

This capacitor will have an applied DC voltage of 25V. In an X5R cap, this can cause a capacitance drop of 80%. This would make each of the capacitors above have an actual capacitance of ~0.44uF. Thus, we would need 6 of this capacitor in order to get the desired capacitance.

Output Capacitor (C3): https://www.digikey.ca/en/products/detail/samsung-electro-mechanics/CL10A335KP8NNNC/3887550

https://www.digikey.ca/en/products/detail/murata-electronics/GRM188Z71A475KE15J/16602144

NOTE: 4.7uF cap chosen as it is amore common value.

Apply Equation 12 on page 13 of datasheet to determine capacitance. Take an output voltage ripple of 3%.

∆V_out = 0.03*V_out = 0.15V; Io = 5A; f = 425kHz (see RTON calc below); Co = ?

Co = ~3.3uF

This capacitor will have an applied DC voltage of 5V. In an X5R cap, this can cause a capacitance drop of 40%. This would make each of the capacitors above have an actual capacitance of ~2uF. Thus, we would need two of these capacitors to get the desired capacitance.

4.7uF Decoupling Capacitor (C4): https://www.digikey.ca/en/products/detail/murata-electronics/GRM188R6YA475ME15D/4905370

This capacitor will have an applied DC voltage of 5V. In an X5R cap, this can cause a capacitance drop of 40%. This would make each of the capacitors above have an actual capacitance of ~2.8uF. Thus, we would need two of these capacitors to get the desired capacitance.

0.1uF Bootstrap Capacitor (C5): https://www.digikey.ca/en/products/detail/murata-electronics/GCJ188R71C104KA01D/2783813

Resistors:

Feedback Resistors:

R1: https://www.digikey.ca/en/products/detail/yageo/RC0603FR-0773K2L/727374

R2: https://www.digikey.ca/en/products/detail/yageo/AC0603FR-1310KL/13694194

https://fscdn.rohm.com/en/products/databook/applinote/ic/power/switching_regulator/resistor_setting_for_vout_appli-e.pdf

Using the formula at the bottom of the first page of the link above, and setting R2 = 10kOhm, we get a value of 73.3333kOhm (reference voltage is 0.6V). We will take the closest standard resistor value which is 73.2kOhm.

100kOhm Input Resistor (R3): https://www.digikey.ca/en/products/detail/yageo/RC0603FR-07100KL/726889

R_TON: https://www.digikey.ca/en/products/detail/yageo/RC0603FR-13470KL/13694191

R_TON=470kOhms

f = ?

f = V_out/(V_in*T_ON)

T_ON(ns) = (R_TON(kOhms)/V_in(V)) * 25 = (470/25V) * 25 = 470ns

f = (V_out/(V_in*T_ON)) * 10⁶ = (5V/(25V*470ns)) * 10⁶ = 425kHz

Using a 470kOhm resistor for R_TON will set the frequency to 425kHz.

This frequency is reasonable to keep the inductor within a reasonable size while keeping switching losses down.

Current Limit Resistor (R_OCS): https://www.digikey.ca/en/products/detail/yageo/RC0603JR-0718KL/726725

The current limit resistor needs a minimum value of 18k. A current limit resistor of 18k will set a current limit of ~13A.

Inductor:

option 1: https://www.digikey.ca/en/products/detail/eaton-electronics-division/EXLA1V0606-6R8-R/16892708

pros: small, cheap
cons: high DCR

option 2: https://www.digikey.ca/en/products/detail/eaton-electronics-division/DR125-6R8-R/667158

pros: cheap, low DCR
cons: large

Used 30% ripple current.

V_out = 5V, V_in = 25V, f = 425kHz, ∆I_L = 0.3*I_out = 0.3*5 = 1.5A

L = (V_out/(f*∆I_L))*(1 - (V_out/V_in))= (5/(425000*1.5))*(1 - (5/25)) = 6.3uH

Peak inductor current = Iout + (∆I_L/2) = 5 + (1.5/2) = 5.75A

25 to 12V Buck @ 3A - @Hardy Yu

Requirements:

Voltage input 26 ~ 15V
Output Voltage - clean 12V
Max Current @ 3A

Component Selection:

@ LMR33630

Datasheet: https://www.ti.com/lit/ds/symlink/lmr33630.pdf?ts=1688621693140&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLMR33630

All different types of the IC: https://www.digikey.ca/en/product-highlight/t/texas-instruments/lmr33630-simple-switcher-buck-converter

Digikey: https://www.digikey.ca/en/products/detail/texas-instruments/LMR33630CDDAR/8554849

Highlight:

Input voltage max: 36V
Ultra-low EMI
efficiency @ 94%
Small

Price: $2.07 unit price if buy 10 (maybe we can find the same component with less price?)

Simplified Schematic:

According to the datasheet, the component we are choosing, the one with 2.1Mhz switch frequency, will be choosing the connected components with the following number

Inductor Choice:

@ BWVS005050403R3M00

Parameters: 3.3uh 3.5A 2.6mOhms

Digikey: https://www.digikey.ca/en/products/detail/pulse-electronics/BWVS005050403R3M00/12140940

Capacitor Choice:

@ GRM21BZ71H475KE15K

Parameters: 4.7uf X7R 0805 50V

https://www.digikey.ca/en/products/detail/murata-electronics/GRM21BZ71H475KE15K/13904908

@ 06035C105KAT2A

Parameters: 1uf X7R 0603 50V

https://www.digikey.ca/en/products/detail/kyocera-avx/06035C105KAT2A/6564263

@ CL31B106KBHNNNE

Parameters: 10uf X7R 1206 50V

https://www.digikey.ca/en/products/detail/samsung-electro-mechanics/CL31B106KBHNNNE/5961251

Use this 10uF cap for input and output capacitance. Same PN as other projects

GRM21BR61H106KE43L

Thermal Design Concerns Reference:

https://www.ti.com/lit/an/slyt793a/slyt793a.pdf?ts=1689862966472

Select Input Capacitor for a Buck Converter Reference:

https://www.ti.com/lit/an/slyt670/slyt670.pdf?ts=1689851310429&ref_url=https%253A%252F%252Fwww.google.com%252F

Shield-Nucleo Interface - @Hardy Yu

Connection Solution:

Place long-leg female headers on the shield PCB board such that the headers line up with the relative position on the Nucleo board. This will sacrifice some of the pins and the functionalities along with them from Nucelo board because the female headers from the Nucleo do not represent all the pins. We choose to still go for interface the Shielf with Nucleo through those headers because the number of connectivities provided from those connectors are more than enough for the requirement for tracking antenna

Component Selection:

@ SSW-1??-23-F-D - XX Position Receptacle Connector 0.100" (2.54mm) Through Hole Gold

Grouped Output Pinout - @Hardy Yu

Pin Allocation

We don’t want to transport all the connectivities from the Nucleo board to the shield PCB because this is going to significantly increase the complexity of the PCB design.

We the connectivities we want to keep on the shield design -