AD9980PCB datasheet(34/44 Pages) AD

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AD9980

Preliminary Technical Data

Rev. 0 | Page 34 of 44

power-down to be controlled by software. With

manual power-down control, the polarity of the

power-down pin must be set (0x1E, Bit 2) whether it is

used or not. If unused, it is recommended to set the

polarity to active high and to hardwire the pin to

ground with a 10 kΩ resistor.

Table 44. Auto Power-Down Select

Power-Down Select

Result

Manual power-down control

User determines power-down

Auto power-down control

Chip determines power-down

0x1E

Power-Down

This bit is used to manually put the chip in power-

down mode. It is used only if manual power-down

control is selected (see Bit 4 of the power-down

power-down pin (Pin 17) are used to control manual

power-down (see the Power Management section for

more details on power-down.).

Table 45. Power-Down Settings

Power-Down Select

Pin 17

Result

Normal operation

Power-down

0x1E

Power-Down Polarity

This bit defines the polarity of the power-down pin (Pin 17). It

is only used if manual power-down control is selected (see Bit 4

above).

Table 46. Power-Down Pin Polarity

Select

Result

Power-down pin is active low

Power-down pin is active high

0x1E

Power-Down Fast Switching Control

This bit controls a special fast switching mode. With

this bit, the AD9980 can stay active during power-

down and only put the outputs in high impedance.

This option is useful when the data outputs from two

chips are connected on a PCB and the user wants to

switch instantaneously between the two.

Table 47. Power-Down Fast Switching Control

Fast

Switching Control

Result

Normal power-down operation

The chip stays powered-up and the

outputs are put in high impedance

mode

0x1E

SOGOUT High Impedance Control

This bit controls whether the SOGOUT output pin is

in high impedance or not when in power-down mode.

In most cases, SOGOUT is not put in high impedance

during normal operation. It is usually needed for sync

detection by the graphics controller. The option to put

SOGOUT in high impedance is included mainly to

allow for factory testing modes.

Table 48. SOGOUT High Impedance Control

SOGOUT

Control

Result

The SOGOUT output operates as normal

during power-down.

The SOGOUT output is in high impedance

during power-down.

OUTPUT CONTROL

0x1F

6:5

Output Mode

These bits choose between three options for the

output mode. In 4:4:4 mode RGB is standard, in 4:2:2

mode YCbCr is standard, which allows a reduction in

the number of output pins from 24 to 16. In 4:4:4

DDR output mode, the data is in RGB mode but

changes on every clock edge. The power-up default

setting is 00.

Table 49. Output Mode

Output Mode

Result

4:4:4 RGB mode

4:2:2 YCbCr mode

4:4:4 DDR mode

0x1F

Primary Output Enable

This bit places the primary output in active or high

impedance mode. The power-up default setting is 1.

Table 50. Primary Output Enable

Select

Result

Primary output is in high impedance mode

Primary output is enabled

0x1F

Secondary Output Enable

This bit places the secondary output in active or high

impedance mode.

The secondary output is designated when using either

4:2:2 or 4:4:4 DDR. In these modes, the data on the

blue output channel is the secondary output while the

output data on the red and green channels are the

primary output. Secondary output is always a YCbCr

DDR data mode. See the Output Formatter section

and Table 11. The power-up default setting is 0.

Table 51. Secondary Output Enable

Select

Result

Secondary output is in high impedance mode

Secondary output is enabled

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