VX6854LC datasheet(19/114 Pages) STMICROELECTRONICS

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VX6854LC

Functional description

3.4

Power management

VX6854LC requires a dual power supply. The analog circuits are powered by a nominal

2.8 V supply while the digital logic and digital I/O are powered by a 1.8 V supply. Different

sections of the sensor are powered depending on the system state. See Table 7 for details.

Table 6. Operating modes

Mode

Description

Power off

Power supplies are off.

Hardware standby

This is the lowest power consumption mode. CCI communications are not

supported in this mode. The clock input pad, PLL and the video blocks are

powered down. This state is entered by pulling the control pin

XSHUTDOWN down. All registers are returned to their default values.

Software standby

This mode preserves the contents of the CCI register map. CCI

communications are supported in this mode. The software standby mode is

selected using a serial interface command. If this state is entered from

hardware standby the data pads remain high impedance. If this state is

entered from streaming then the data pads go high impedance at the end

of the current frame. At this point the video block and PLL power down. The

internal video timing is reset to the start of a video frame in preparation for

the enabling of active video. The values of the serial interface registers like

exposure and gain are preserved. The system clock must remain active

when communicating with the sensor.

This state is entered by releasing the device from hard reset by: setting

XSHUTDOWN high, writing 0x00 to the mode control register (0x0100) or

commanding a soft reset by writing 0x01 to the software reset register

(0x0103). Note that after a soft reset or the transition of XSHUTDOWN to

high, all registers are returned to their default values.

Streaming

The VX6854LC streams live video. This mode is entered by writing 0x01 to

the mode control register (0x0100).

Table 7. Power management matrix

Mode

Functional block powered down

Video data

inhibit

CCI

Digital

PLL and

CLK pins

(1)

PLL, CLK+ and CLK- pins

Output

pins

Analog

Hardware

standby

Yes

Software standby

Yes

Streaming

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