saa8115hl NXP Semiconductors, saa8115hl Datasheet - Page 15

• Manufacturer Part Number: saa8115hl
• Description: Saa8115hl-04 Digital Camera Usb Interface
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 07395
Product specification
8.11 Power management
8.12 Power supply
USB requires the device to switch power states. The SAA8115HL contains a power
management module since the complete camera may not consume more than
500 A during the power state called SUSPEND. This requires that even the crystal
oscillator must be switched off. The SAA8115HL is not functional except for some
logic that enables the IC to wake-up the camera. After wake-up of the SAA8115HL
first the clock to the microcontroller is generated and thereafter an interrupt is
generated to wake-up the microcontroller. Therefore the clock of the microcontroller is
generated by the SAA8115HL.
The power management module also sets a flag in register SET_MODE_AND_READ
(PSIE_MMU_STATUS). After a reset the microcontroller should check this register via
the I
start-up routines.
The internal video processing core uses another supply domain which can be
switched off during SUSPEND mode.
The PPG is switched off by setting PPG_RESUME_MODE (0x08) and resetting
PAL_VGA (0x09).
In non CIF modes the power consumption is reduced by resetting
COMPRESSION_MODE (0x2F) and COMPRESSION_CLOCK (0x09).
The SAA8115HL has the feature to autonomously wake-up from SUSPEND mode,
but requires microcontroller interference before going in SUSPEND mode (via the
signal on pin SUSPREADYNOT).
Since the main oscillator of the SAA8115HL is switched off during SUSPEND mode,
precautions are needed to avoid undefined states when the clock is switched on. This
is ensured via the pins CLOCKON and TRC. Pin CLOCKON goes HIGH as soon as
the main oscillator is switched on. The oscillator will need some time to make a stable
48 MHz signal. However, the clock is only passed through to other parts of the
SAA8115HL when the level on pin TRC reaches a certain threshold. The time
needed to reach the threshold can be trimmed with an external RC circuit.
A power supply regulator is integrated in the device. This DC-to-DC converter
transforms the USB supply voltage (range from 4.0 to 5.5 V) into a stable 5 V supply
voltage. This power domain is switchable. The power circuit also generates a reset
signal when the external 3.3 V supply voltage is stable and in range.
2
C-bus and find the cause of the wake-up. Different causes may require different
Rev. 04 — 10 August 2000
Digital camera USB interface
SAA8115HL
© Philips Electronics N.V. 2000. All rights reserved.
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