Freelance projects

Freelance projects

Redesign the power supply on the board according to the specifications.

Drawings & Diagrams — incorrectly specified categories?

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https://github.com/rishikesh2715/STM32F7_FC

Redesign of the power block for STM32F7 Flight Controller (30×30 mm)

📌 Project Context

There is a ready design of a flight controller on STM32F722 (30×30 mm format).
The current design uses a budget power block:

Buck TPS54335 (9V and 5V)
LDO AZ1117-3.3
One common ground (GND)
3.3V powers both the MCU and the IMU

This approach works, but introduces excess noise on the IMU and is not suitable for a quality FC.

🎯 Goal of the Redesign

Redesign only the power block (without logic, MCU, OSD, etc.) to achieve:

better stability
less noise
correct power supply for the IMU
compact layout for 30×30 mm

This is NOT a complete FC design, only the power section.

🔌 Input Data

Board format: 30×30 mm
Input power: VBAT (LiPo 3–6S)
There is a ready schematic of the power block that needs to be used as a basis and redesigned
Components have already been purchased — use exactly them

📦 Components that MUST be used

Buck 5V

LMR23630AFDDAR
→ output +5V, ≥2A

LDO

TLV75733 — 3.3V for digital logic (MCU, OSD, Flash)
TLV75533 — 3.3V low-noise separately for IMU

Protection

TVS SMBJ58A on VBAT

Passive Components

Inductance: 4.7µH (≥3A)
Capacitors: 10µF, 22µF, 100nF (X7R)
Resistors for feedback (33k / 10k or equivalent)
0Ω resistor for connecting grounds (star point)

⚡ Power Architecture (MUST)

VBAT
 └─ TVS
 └─ Buck LMR23630 → +5V (PGND)
 ├─ LDO TLV75733 → +3V3_DIGITAL
 └─ LDO TLV75533 → +3V3_IMU

🌍 Ground (VERY IMPORTANT)

Separate the ground into:
- PGND — power (buck, TVS, CIN, COUT)
- AGND — quiet/analog (IMU, FB, CVCC, LDO_IMU)
THE ONLY connection point PGND ↔ AGND through a 0Ω resistor
No other ground connections

📐 Layout Requirements

Compact FPV-style layout, not reference EVM
Minimize:
- VIN current loop
- SW current loop
Inductance as close to SW as possible
CIN as close to VIN/PGND as possible
FB and IMU rails far from SW
Realistically fit within 30×30 mm

🧪 Expected Outcome

The freelancer must provide:

Updated schematic of the power block
PCB layout of the power block (KiCad)
Explanation:
- where PGND / AGND
- where the star point is
- how to connect the IMU to +3V3_IMU

❌ What NOT to do

Do not redesign the MCU / OSD / Flash
Do not create a complete FC
Do not change components to others
Do not use a single GND

✅ Acceptance Criteria

Clean ERC / DRC
Separate low-noise rail for IMU
Correct operation of buck + LDO
Layout suitable for FPV FC

Proposals Discussions 1

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Nikita Chumak
Kyiv, Ukraine

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