Raspberry Pi 5 HAT Design Discussion
Table
| Part Name | Purpose | Manufacturer Part Number | Quantity | Footprint | Datasheet link |
|---|---|---|---|---|---|
| 40-pin Pass-through Header (RPi HAT stackable) | Provides stackable GPIO connection to Raspberry Pi 5 and pass-through to other HATs | M20-6102045 | 1 | 2×20 TH | |
| HAT+ ID EEPROM (3.3 V) | Stores HAT identification; connected only to GPIO0/1 with 3.3 V pull-ups | 24LC32A-I/P | 1 | DIP-8/ SOIC-8 (prefer SOIC-8) | |
| I2C Pull-up Resistor 4.7 kΩ | Pull-up on 3.3 V ID bus (GPIO0/1) | RC0603FR-074K7L | 2 | 0603 | |
| Decoupling Capacitor 100 nF | Local decouple for ID EEPROM | CL10B104KB8NNNC | 1 | 0603 | |
| I2C Level Translator | Bidirectional I2C translation between Pi 3.3 V and device 5 V busses | PCA9306DCUR | 1 | VSSOP-8 | |
| I2C Pull-up Resistor 4.7 kΩ | Pull-up on Pi-side I2C1 (3.3 V) | RC0603FR-074K7L | 2 | 0603 | |
| I2C Pull-up Resistor 4.7 kΩ | Pull-up on device-side I2C (5 V) | RC0603FR-074K7L | 2 | 0603 | |
| Decoupling Capacitor 100 nF | Local decouple for PCA9306 | CL10B104KB8NNNC | 1 | 0603 | |
| PWM Controller (16-ch, 12-bit) | Core PWM engine at 5 V; exposes 6 buffered channels + 10 spare | PCA9685PW | 1 | TSSOP-28 | |
| Address Solder Jumpers (A0..A5) | Configure PCA9685 I2C address; default 0x40 | SJ-3523-SMT | 6 | 3-pad SJ | |
| OE Pull-up Resistor 10 kΩ | Holds OE deasserted by default; optional link to GPIO | RC0603FR-0710KL | 1 | 0603 | |
| Decoupling Capacitor 100 nF | Local decouple for PCA9685 | CL10B104KB8NNNC | 1 | 0603 | |
| Bulk Capacitor ≥47 µF | Local bulk for PCA9685 5 V rail | EEE-FT1V470AP | 1 | SMD Elec | |
| Inverting Schmitt Buffer (hex) | Robust 5 V output buffering for 6 primary channels | SN74HC14D | 1 | SOIC-14 | |
| Series Resistor 47 Ω | Damping resistor at each buffered output (CH1..CH6) | RC0603FR-0747RL | 6 | 0603 | |
| Optional RC Cap Pad 0–100 pF (DNP) | Edge-rate tuning near connector per channel | CL10C100JB8NNNC | 6 | 0603 | |
| Low-cap ESD TVS (2-line) | Per-channel ESD protection at connector edge | ESD9M5V-DL | 6 | SOD-923 or DFN | |
| Screw Terminal 3-pos, 5.0 mm, vertical | Field I/O for each primary channel: PWM, +5 V, GND | 691137710003 | 6 | TH 5.0 mm | |
| Spare Channel Series Resistor 220 Ω | Series limit for 10 spare outputs to pads | RC0603FR-07220RL | 10 | 0603 | |
| Test/Expansion Thru-hole Pads | Expose spare channels (DNP connectors) | TP_TH_1.0mm | 10 | TH pad | ___ |
| Decoupling Capacitor 100 nF | Local decouple for SN74HC14 | CL10B104KB8NNNC | 1 | 0603 | |
| External 5 V Input Terminal (2-pos) | Optional field power entry for terminals | 691137710002 | 1 | TH 5.0 mm | |
| Resettable Fuse PTC (hold ~1.1 A) | Protect external 5 V input path | MF-MSMF110/16X | 1 | 1206 | |
| TVS Diode SMBJ5.0A | Surge/ESD at external 5 V entry | SMBJ5.0A | 1 | SMB | |
| Power Inductor 1 µH ≥1 A | LC filter for external 5 V | SRN4018-1R0M | 1 | 4.0×4.0 mm | |
| Ceramic Capacitor 10 µF, 25 V X7R | LC filter output decoupling | CL10A106MQ8NNNC | 1 | 0603 | |
| Bulk Capacitor 100 µF | External 5 V bulk after filter | EEE-FT1E101AP | 1 | SMD Elec | |
| 0 Ω Link (DNP) | Backfeed link between filtered 5 V and Pi 5 V (default open) | RC0603JR-070RL | 1 | 0603 | |
| Solder Bridge (OE to GPIO option) | Optional route OE to Pi GPIO for global mute | SJ-3523-SMT | 1 | 3-pad SJ |