AD9859/PCBZ Analog Devices Inc, AD9859/PCBZ Datasheet - Page 22

• Manufacturer Part Number: AD9859/PCBZ
• Description: 400 MSPS DDS W/ 10 BIT DAC EvalBd
• Manufacturer: Analog Devices Inc
• Series: AgileRF™r

Specifications of AD9859/PCBZ

• Main Purpose: Timing, Direct Digital Synthesis (DDS)
• Embedded: No
• Utilized Ic / Part: AD9859
• Primary Attributes: 10-Bit DAC, 32-Bit Tuning Word Width
• Secondary Attributes: 400MHz, Graphical User Interface
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD9859
When the CFR1<3> bit is 0 and the PWRDWNCTL input pin is
high, the AD9859 is put into a fast recovery power-down mode.
In this mode, the digital logic and the DAC digital logic are
powered down. The DAC bias circuitry, PLL, oscillator, and
clock input circuitry is NOT powered down.
When the CFR1<3> bit is high and the PWRDWNCTL input
pin is high, the AD9859 is put into the full power-down mode.
In this mode, all functions are powered down. This includes
the DAC and PLL, which take a significant amount of time to
power up.
When the PWRDWNCTL input pin is high, the individual
power-down bits (CFR1<7>, <5:4>) are invalid (Don’t Care)
and unused. When the PWRDWNCTL input pin is low, the
individual power-down bits control the power-down modes of
operation.
Note that the power-down signals are all designed such that a
Logic 1 indicates the low power mode and a Logic 0 indicates
the active or power-up mode.
Table 8. Power-Down Control Functions
Control
PWRDWNCTL = 0 CFR1<3> Don’t Care
PWRDWNCTL = 1 CFR1<3> = 0
PWRDWNCTL = 1 CFR1<3> = 1
Mode Active
Software Control
External Control,
Fast Recovery Power-Down Mode
External Control,
Full Power-Down Mode
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Table 8 indicates the logic level for each power-down bit that
drives out of the AD9859 core logic to the analog section and
the digital clock generation section of the chip for the external
power-down operation.
Layout Considerations
For the best performance, these layout guidelines should be
observed. Always provide the analog power supply (AVDD) and
the digital power supply (DVDD) on separate supplies, even if
just from two different voltage regulators driven by a common
supply. Likewise, the ground connections (AGND, DGND)
should be kept separate as far back to the source as possible (i.e.,
separate the ground planes on a localized board, even if the
grounds connect to a common point in the system). Bypass
capacitors should be placed as close to the device pin as possi-
ble. Usually, a multitiered bypassing scheme consisting of a
small high frequency capacitor (100 pF) placed close to the
supply pin and progressively larger capacitors (0.1 µF, 10 µF)
further away from the actual supply source works best.
Description
Digital Power-Down = CFR1<7>
DAC Power-Down = CFR1<5>
Input Clock Power-Down = CFR1<4>
Digital Power-Down = 1’b1
DAC Power-Down = 1’b0
Input Clock Power-Down = 1’b0
Digital Power-Down = 1’b1
DAC Power-Down = 1’b1
Input Clock Power-Down = 1’b1