AD9927 Analog Devices, AD9927 Datasheet - Page 79

• Manufacturer Part Number: AD9927
• Description: 14-Bit CCD Signal Processor
• Manufacturer: Analog Devices

V-Driver Power Supply Sequencing
When powering up the V-driver of the AD9927, it is important
to pay attention to the order that the various V-driver power
supplies are turned on. Particularly, a bias voltage of 2.3 V or
greater must be applied to the V5V pin prior to powering up the
VH and VL supplies. V5V is an internal voltage that eventually
rises to ~5.4 V after VH and VL are powered up; therefore, it
needs to be driven through a diode. A Schottky diode is
recommended to maximize the bias voltage on V5V. To ensure
proper operation, adhere to the following steps:
1.
Connect VDD1 and VDD2 to a 3 V supply and keep V5V low.
0V
V
Figure 93. Suggested Power-Up Sequence for AD9927 V-Driver Supplies
DD
V5V
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VH
VL
2.
3.
4.
Perform any necessary writes to Registers 0x25 and 0x26
(VT_STBY12 and VT_STBY3, respectively) to define the
polarities of the V-driver outputs prior to powering up the
VH and VL supplies.
Bring the signal driving the diode to V5V high. (Note that
a GPO output can be used for this operation.)
After V5V reaches a minimum of 2.3 V, VH and VL can be
powered on. There are no restrictions to the order in which
VH and VL can be powered on at this time.
AD9927