4 - 6 SE4750 Integration Guide
Power Supply Sequencing
The imager engine contains three power domains: VCC, VCC_ILLUM, and VDD_IO_HOST. Specific power-up and
power-down sequences of these three supplies are recommended to ensure proper operation.
Power-up
During power-up, the VCC supply ramps up before or at the same time as the VCC_ILLUM and VCC_IO_HOST
supplies. The VCC_ILLUM and VDD_IO_HOST supplies can ramp up together or at different times. While supplies
ramp up, however, the VCC_ILLUM and VDD_IO_HOST supplies should not exceed the voltage on the VCC
supply.
Figure 4-4
Power-up Sequence
Power-down
To power-down the engine, it is recommended that the host system send a command to the engine that causes it to
enter the low-power standby state. This ensures that critical operations, such as flash writes, are not interrupted
when power is removed. Once the standby command is acknowledged, the power supplies can be safely removed.
The VCC_ILLUM and VDD_IO_HOST supplies should be removed before or at the same time as the VCC supply.
While supplies are ramping down, however, the VCC_ILLUM and VCC_IO_HOST supplies should not exceed the
voltage on the VCC supply.
Figure 4-5
Power-down Sequence
VCC
VCC_ILLUM
VDD_IO_HOST
≥ 0
Power-up Sequence
≥ 0
VCC
VCC_ILLUM
VDD_IO_HOST
≥ 0
Power-down Sequence
≥ 0
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