STV0674 datasheet(23/35 Pages) STMICROELECTRONICS

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STV0674

Detailed Specifications

4.9

Device current consumption in run and suspend modes

The STV0674 power consumption has been estimated based on a webcam configuration. In this

way, the analysis can specifically consider the device’s intrinsic power consumption rather than that

associated with other system-level components. As STV0674 typically ends up in very low USB or

battery powered applications, it is important device power consumption is measured in three

different operating modes representing typical operating conditions in the real application.

These three modes shall be referred to as low power mode, high power mode and suspend mode.

Suspend mode is the is the lowest power mode of the device. For the core current, it can be

effectively equated to ‘static’ power consumption. In this mode, all embedded clocks are stopped

and all embedded logic blocks, macros, IP, etc. are reset into their low power modes. The XTAL

oscillator pads (providing main clock source to entire STV0674) are also stopped. The name

‘Suspend’ mode historically comes from the device’s requirement to comply with USB ‘suspend’

mode where the total current drawn from the host PC by the USB peripheral is not allowed to

exceed 500 µA.

In low power mode, the embedded VP and VC module clocks are disabled and held in reset. The

VP and VC are the two most power-hungry modules in the STV0674. A limited number of modules

are enabled in this mode to allow USB enumeration, system-level self-configuration or camera user-

interface functions. Such modules include the embedded microcontroller, USB core, memory sub-

systems and SFP core.

In high power mode. The VP and VC module clocks is enabled and are brought out of reset. This is

more typical of the real device application in that video data is being generated and processed. In

measured cases the VP and VC are set up to their fastest (worst-case power) modes of operation

processing VGA source data from the sensor at full 30 frames-per-second.

Note:

The baseline device power model presented here can be extended to cover other system-level

configurations. In such cases the core IDD will remain as measured here (30fps/VGA) but the i/o IDD

is more likely to vary depending for example on which memory type (sdram/nand) is being used.

The power associated with each pin can be calculated based on its frequency (MHz), capacitive (C)

and resistive (R) loading.

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