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Part Number: DLPC3430
On initial power-up, we apply VSYS (3.8V) and then VCC (1.8V). Before PROJ_ON pin is toggled, i noticed that the I2C0_SCL and I2C_SDA pins are pulled low. These pins stay in this state until PROJ_ON turns on the DLPA2000. After that, the I2C lines go High-Z. After that, we can clear PROJ_ON and the SDA and SCL lines remain High-Z.
Is this behavior expected? It seems strange that the I2C bus does not power up to High-Z by default.
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In reply to Azad:
In our main system, we have 2.2k resistors.
On one board, i removed everything besides the DLPC and DLPA and put weak (100k) pull ups and i see the same behavior. I2C is pulled low (by the DLPC since that is the only device on the bus) and the pull down is removed as soon as PROJ_ON is set high.
Toggling the HOST_IRQ did not clear the pull down.
In reply to Gerald:
Hi Gerald, Which voltage source are the resistors pulled up to? The external VCC (1.8V) or the 1.8V LS_OUT of the DLPA2000? Regards Azad
This is pulled to VDD_INTF which is the input to the LS_1P8 rail. This rail is our system 1.8V rail which is always on when our system is powered.
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