Category: Hardware
Product Number: LTC3300-1
Description:
We are using an STM32G4 MCU to communicate with three LTC3300-1 chips via SPI in daisy chain configuration. The SPI settings are:
- Mode: 3 (CPOL = 1, CPHA = 1)
- Clock Speed: 750 kbps
- Data Frame Format: 8 bits
We have verified that:
- TOS and VMODE signals are correct
- VREG output for all LTC3300-1 chips is 4.8V
- CS, SCK, and MOSI signals are toggling correctly and meet timing specifications
Issue:
The bottom LTC3300-1 in the daisy chain does not respond to the Read Balance Status command (0xAC). Specifically, MISO remains high instead of returning data.
Hardware Setup:
- PCB is long, with the MCU-to-last-LTC3300 distance being ~17 inches
- CS pullup: 10K to MCU's 3.3V
- MISO pullup: 2K to MCU's 3.3V
- Observed ripple on MCU's 3.3V rail
Troubleshooting Steps Tried:
- Lowered SPI clock rate
- Silenced all other SPI activity on the board
- Adjusted MISO pullup resistor values
Given the PCB length and power rail ripple, could signal integrity or power fluctuations be contributing to this issue? Are there recommended mitigation strategies for long daisy chains or power stability concerns?
Thank you for your support.
