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Project Owners: Mostafa Hussein Rayyan Mahmood

Requirements:

  • Can take 6S voltage

  • Can handle 50 A continuous

  • Create block diagram

    • Show the high-level process of how the motor controller works from receiving a battery voltage to controlling the phases of the motor

  • Create table for engineering decisions and tradeoffs for the following components:

    • MCU

    • Gate driver IC

      • Does it have field-oriented control?

      • Does it have built in current sense? That would be extremely useful so that we don’t have to waste board space using a current sense amplifier and shunt

    • Power MOSFETs

    • Buck converter for MCU

    • Battery input connection type

    • PWM connection type

    • Programming pins connection type

Component Selection

Buck:

Part Number

Price

Comments

 TPS62932DRLR

$1.09

Buck IC

RC0805FR-0716KL

$0.15

R7(16kΩ) - Lower resistor in Feedback voltage divider

RC0805FR-0749K9L

$0.15

R6(49.9KΩ) - Upper resistor in Feedback voltage divider

GCD21BR71H333KA01L

$0.27

Css (Soft-start Cap) - 33nF

GCD21BR71H104KA01L

$0.33 (x2)

CBST & Filtering Cap (0.1uF - 50V)

GRM21BR61H106KE43L

$0.48 (x8)

Cin(10µF) x 8 (since it is around 1.3µF at 25.3 Volts due to DC Bias) - Ceramic Cap , 50V

RC0805FR-1320KL

$0.15

R2 (20 KΩ) UVLO

RC0805FR-07280KL

$0.15

R1 (280 KΩ) UVLO

IHLP3232DZER3R3M01

$1.90

L1 (3.3uH - 9.2A)

GRM21BR61A476ME15K

$0.91

Cout (47UF - 10V)

Buck Selection:

Re-evaluating the decision of going with the MAX5033DASA+ chip for the buck converter, mainly to reduce form factor while maintaining high efficiency.

Current Issue:

To optimize the circuit for the MAX5033DASA+ chip, specific requirements need to be considered for the output capacitor. The datasheet provides a specific range of frequencies for the zeros of the buck’s power stage which is controlled by the output capacitance and ESR. Furthermore, to optimize the capacitor selection for the proposed use case - 6S ESC, handing 6S lipo input, outputting 3.3V at 0.5 Amps - a tantalum or electrolytic capacitor is needed.

Additionally, operating at a fixed switching frequency, this chip forces a high inductance inductor to be used. The higher the inductance the larger the inductor.
Overall, the MAX5033DASA+ chip requires a large footprint to operate “optimally” for the restrictions desired.

Comparison Chart:

LMR54406

TPS54302

TPS563300

TPS62932

MAX5033

Vin Range (V)

4 - 36

4.5 - 28

3.8 - 28

3.8 - 30

7.5 - 76

Vout Range (V)

1 - 28

0.6 -26

0.8 - 22

0.8 - 22

1.25 - 13.2

Iout Max (A)

0.6

3

3

3

0.5

Switching Freq. (kHz)

935 - 1264

400

500

200 - 2200

125

Electrolytic/Tantalum Caps needed? (Y/N)

Ceramic

Ceramic

Ceramic

Ceramic

Tantalum

Package Size

8.12 mm²

8.12 mm²

3.36 mm²

3.36 mm²

-

Price

$1.55

$2.42

$1.03

$1.09

In the bay ($6.40)

Note 1: All these chips have adjustable outputs using a feedback pin connected to a voltage divider.

Note 2: These (new) chips were selected for ease of use and available resources on their usage.

Decision Matrix:

LMR54406

TPS54302

TPS563300

TPS62932

MAX5033

Max

Vin Range (V)

5

5

5

5

5

5

Vout Range (V)

5

5

5

5

5

5

Iout Max (A)

5

5

5

5

5

5

Switching Freq. (kHz)

4

2

2

5

1

5

Electrolytic/Tantalum Caps needed? (Y/N)

5

5

5

5

1

5

Package Size

3

3

5

5

3

5

Price

3

2

5

5

5

5

Totals

30

27

32

30

25

30

Summary of Decision Matrix:

Each entry was given a max rating out of 5 to denote how “good” a chip using a score. Summing up all the scores for each chip, the one with the highest score would then be considered the “best” of this set of chips.

The logic behind scoring:

Vin Range (V): All components have a sufficient input range for a 6s Lipo battery (18 - 25.2 V)

Vout Range (V): All components have a sufficient output range for the desired application (3.3 V)

Iout Max (A): All the components satisfy the required output current (0.5 A).

Iq - Quiescent Current (mA): This is the current the buck draws when no load is applied / during idle. So here components were given a score, with the best score going to the chip with the lowest value.

Switching Frequency (kHz): This is the buck’s switching frequency. Having a higher frequency is good since it decreases the size of the inductor, however, that comes at the expense of switching losses. So here the components with a higher frequency have a higher score; especially those with a range of possible frequencies.

Electrolytic/ Tantalum Caps needed (Y/N): This is whether the buck will need a capacitor with a higher ESR value such that it can optimize the closed-loop stability of the power stage. Here all the chips that do not need such caps are given a 5 (all the newly selected ones) and those that need such caps are given a 1.

Number of pins: Not really a very big deal, but just the number of pins each chip has. Chips with fewer pins are considered better under the assumption that they are “simpler” but circuits for all of these chips are similar (same idea overall).

Price: Ranked the chips best on price, giving the MAX5033 a 5 since it is in the bay already.

Conclusion:

Given the current issues with the MAX5033 and evaluating it against other (similar) buck converter chips, it is evident that despite the advantage of already having the MAX5033, other bucks convert chips can satisfy the proposed requirements for the 6S ESC project while minimizing the buck converter circuit’s footprint on the PCB. Moreover, given the results from the Decision Matrix, the recommendation for the new buck chip is the TPS62932.

Plots used for buck selection:

image-20240204-030102.pngimage-20240204-030304.pngimage-20240204-030506.pngimage-20240204-030840.pngimage-20240204-031023.pngimage-20240204-031220.png

MCU:

Part Number

Price

Comments

STM32L412KBT6

 Already orderd && in the bay

 same mcu as 4s esc with same passives

Current Sense:

Part Number

Price

Comments

INA180A1IDBVR

 Already orderd && in the bay

 same current sense IC as 4s esc

BVT-M-R001-1.0

$2.30

1mOhms, 6W shunt resistor

CL10B104KB8NNNC

$0.15

Bypass Cap and filter caps, 0.1uF x2

RC0603FR-0710KL

$0.16

Filter resistor, 10kOhms, 1/10W

 

Gate Driver:

Part Number

Price

Comments

 DRV8328BRUYR

 already ordered

 same gate driver as 4s esc

 

 

 

 

MOSFET:
Calculations for decision matrix:

Part Number

Price

Vds

Rds on (max)

Continuous Current

Gate Charge (nC)

Rise time

Fall time

Max Operating Temperature

Switching Transition Loss

Switching Loss

Conduction Loss

Temperature Rise [Base 25°C]

Comments

 CSD17577Q5A

 1.08

 30V

 4.2mOhm @ 18A, 10V

60A

13 @ 10V

12ns

2ns

150°C

2.1W

0.04472W

10.5W

630°C

TSM080N03EPQ56

 0.96

 30V

 8mOhm @ 16A, 10V

 55A

7.5 @ 4.5 V

12.5ns

8.2ns

150°C

3.105W

0.02025W

20W

1440.26°C

 Wider package size

GSFP03602

1.02

30V

7mOhm @ 30A, 10V

60A

23.5 @ 10V

30ns

6ns

150°C

5.4W

0.0659W

17.5W

N/A [datasheet missing R_θja]

IQDH45N04LM6CGATMA1

5.77

40V

0.45mOhm @ 50A, 10V

60A

129 nC @ 10 V

6ns

14ns

175°C

4W

0.722W

1.125W

294.85°C

IAUA250N04S6N005AUMA1

5.36

40V

0.55mOhm @ 100A, 10V

62A

170 nC @ 10 V

13ns

26ns

175°C

7.8W

N/A [datasheet missing Coss]

1.375W

243.4575°C

SIR500DP-T1-RE3

2.25

30V

0.47mOhm @ 20A, 10V

85.9A

180 nC @ 10 V

11ns

11ns

150°C

3.3W

0.369W

1.175W

96.88°C

 MY SELECTION: SIR500DP-T1-RE3

Primarily for generally lower power losses and lower temperature rise.

Conduction Loss:

Gate Charge Loss:

Output Capacitance Loss:

Switching Transition Loss:

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