W99681CF Datasheet, PDF (35/78 Pages) Winbond – JPEG USB Dual Mode Camera Chip

W99681CF
7.6 Power Management
The W99681CF provides three output pins as described below for the video camera power
management to meet the USB specification requirements.
• PWRDWN/PWRDWN#: These pins, when active, are used to turn off the USB 5V power
supply to the video source circuits (CCD/CMOS sensor device, ADC, DSP, video decoder,
etc.).
• SUSPND: This pin, when active, is used to turn off the 3.3V power supply to the W99681CF
(excluding USBVDD pin, the power supply for the transceiver), DRAM, and E²PROM.
Bit 10 of the Miscellaneous Control register (CR00) determines whether the W99681CF-based device
is a high power device or a low power device as described below:
• CR00_10 = 1: High power, bus-powered devices. They must draw no more than 100 mA
upon power up and may draw up to 500 mA after being configured.
• CR00_10 = 0: Low power, bus-powered devices. May draw up to 100 mA from their upstream
connection to allow the interface to function when the remainder of the hub is powered down.
7.6.1 W99681CF Reset
The W99681CF has two reset sources: system reset from the input RSTIN# pin, and the USB reset
detected by seeing a single-ended zero (SE0) for more than 2.5 us. All reset sources are joined inside
the W99681CF into a single reset signal which initializes the W99681CF and is also output via the
RSTOUT pin to initialize other external circuits.
Reset can wake the W99681CF from the suspended mode (SUSPND is inactive low) and turn off the
USB 5V power supply to the video source circuits (PWRDWN is active high and PWRDWN# is active
low).
7.6.2 Before Configured
Before configured, the W99681CF should be reset and keep PWRDWN and PWRDWN# to be active
(CR00_4 = 0) such that the W99681CF-based devices will not draw more than 100 mA from the USB
bus power supply. It is required that an external power-on reset should be applied to the RSTIN# pin
before any USB transaction is sent to the W99681CF by the host.
7.6.3 After Configured
After configured, PWRDWN and PWRDWN# pins should be inactive by programming the Camera
Power-on Control register to one (CR00_4 = 1) to enable device functions. The W99681CF-based
devices must draw less than 100 mA (CR00_10 = 0) or 500 mA (CR00_10 = 1) from the bus during
normal operation. The SOF (Start of Frame) packet is guaranteed to occur once a frame to keep full
speed devices awake during normal bus operation.
7.6.4 Suspend
The W99681CF goes into the suspend mode from any powered state when it sees a constant idle state
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Publication Release Date: March 2000
Revision A1