AD9879BS Analog Devices Inc, AD9879BS Datasheet - Page 14

• Manufacturer Part Number: AD9879BS
• Description: IC FRONT-END MIXED-SGNL 100-MQFP
• Manufacturer: Analog Devices Inc

Specifications of AD9879BS

• Rohs Status: RoHS non-compliant
• Number Of Bits: 12
• Number Of Channels: 5
• Power (watts): 587mW
• Voltage - Supply, Analog: 3.3V
• Voltage - Supply, Digital: 3.3V
• Package / Case: 100-MQFP, 100-PQFP

AD9879
RESET AND TRANSMIT POWER-DOWN
Power-Up Sequence
On initial power-up, the RESET pin should be held low until
the power supply is stable.
Once RESET is deasserted, the AD9879 can be programmed
over the serial port. The on-chip PLL requires a maximum of
1 millisecond after the rising edge of RESET or a change of the
multiplier factor (M) to completely settle. It is recommended
that the PWRDN pin be held low during the reset and PLL
settling time. Changes to ADC Clock Select (Register 0x08) or
SYS Clock Divider N (Register 0x01) should be programmed
before the rising edge of PWRDN .
Once the PLL is frequency locked and after the PWRDN pin is
brought high, transmit data can be sent reliably.
If the PWRDN pin cannot be held low throughout the reset and
PLL settling time period, the power-down digital Tx bit or the
PWRDN pin should be pulsed after the PLL has settled. This
will ensure correct transmit filter initialization.
RESET
To initiate a hardware reset, the RESET pin should be held low
for at least 100 nanoseconds. All internally generated clocks
stop during reset. The rising edge of RESET resets the PLL clock
multiplier and reinitializes the programmable registers to their
default values. The same sequence as described in the Power-Up
Sequence section should be followed after a reset or change in M.
TXSYNC
PWRDN
TXIQ
0
20 NULL SYMBOLS
5MCLK
0
Figure 6. Timing Sequence to Flush Tx Data Path
MIN
0
0
Rev. A | Page 14 of 32
DATA SYMBOLS
A software reset (writing a 1 into Bit 5 of Register 0x00) is
functionally equivalent to the hardware reset but does not force
Register 0x00 to its default value.
Transmit Power-Down
A low level on the PWRDN pin stops all clocks linked to the
digital transmit data path and resets the CIC filter. Deasserting
PWRDN reactivates all clocks. The CIC filter is held in a reset
state for 80 MCLK cycles after the rising edge of PWRDN to
allow for flushing of the half-band filters with new input data.
Transmit data bursts should be padded with at least 20 symbols
of null data directly before the PWRDN pin is deasserted.
Immediately after the PWRDN pin is deasserted, the transmit
burst should start with a minimum of 20 null data symbols.
This avoids unintended DAC output samples caused by the
transmit path latency and filter settling time.
Software Power-Down Digital Tx (Bit 5 in Register 02x00) is
functionally equivalent to the hardware PWRDN pin and takes
effect immediately after the last register bit has been written
over the serial port.
PWRDN
RESET
V
S
0
Figure 5. Power-Up Sequence for Tx Data Path
20 NULL SYMBOLS
0
0
0
1ms
MIN
5 MCLK
MIN