AD6636PCB datasheet(47/72 Pages) AD

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AD6636

Rev. 0 | Page 47 of 72

USER-CONFIGURABLE BUILT-IN SELF-TEST (BIST)

Each channel of AD6636 includes a BIST block. The BIST, along

with an internal test signal (pseudorandom test input signal),

can be used to generate a signature. This signature can be

compared with a known good device and an untested device to

see if the untested device is functional.

BIST timer bits in the BIST control register can be programmed

with a timer value that determines the number of clock cycles

that the output of the channels (output of AGC) have

accumulated. When the disable signature generation bit is

written with Logic 0, the BIST timer is counted down and a

signature register is written with the accumulated output of the

AD6636 channel.

When the BIST timer expires, the signature register for I and Q

paths can be read back to compare it with the signature register

from a known good device.

CHIP SYNCHRONIZATION

The AD6636 offers two types of synchronization: start sync and

hop sync. Start sync is used to bring individual channels out of

sleep after programming. It can also be used while AD6636 is

operational to resynchronize the internal clocks. Hop sync is

used to change or update the NCO frequency tuning word and

the NCO phase offset word.

Two methods can be used to initiate a start sync or hop sync:

• Soft sync is provided by the memory map registers and is

applied to channels directly through the microport or serial

port interface.

• Pin sync is provided using four hard-wired SYNC[3:0] pins.

Each channel is programmed to listen to one of these SYNC

pins and do a start sync or a hop sync when a signal is

received on these pins.

The pin synchronization configuration register (Address 0x04)

is used to make pin synchronization even more flexible. The

part can be programmed to be edge-sensitive or level-sensitive

for SYNC pins. In edge-sensitive mode, a rising edge on the

SYNC pins is recognized as a synchronization event.

Start

Start refers to the startup of an individual channel or chip, or of

multiple chips. If a channel is not used, it should be put into

sleep mode to reduce power dissipation. Following a hard reset

(low pulse on the RESET pin), all channels are placed into sleep

mode. Alternatively, channels can be put to sleep manually by

writing 0 to the sleep register.

Start with Soft Sync

The AD6636 can synchronize channels or chips under micro-

processor control. The start hold-off counter, in conjunction

with the soft start enable bit and the channel enable bits, enables

this synchronization.

To synchronize the start of multiple channels via micro-

processor control:

Write the channel enable register to enable one or more

channels, if the channels are inactive.

Write the NCO start hold-off counter(s) to the appropriate

value (greater than 1 and less than 216).

Write the soft sync channel enable bit(s) and soft start

synchronization enable bit high in the soft synchronization

configuration register. This starts the countdown by the

start hold-off counter. When the count reaches 1, the

channels are activated or resynchronized.

Start with Pin Sync

Four sync pins (0, 1, 2, and 3) provide very accurate synchro-

nization among channels. Each channel can be programmed to

monitor any of the four sync pins.

To start the channels with a pin sync:

Write the channel register to enable one more channels, if

the channels are inactive.

Write the NCO start hold-off counter(s) to the appropriate

value (greater than 1 and less than 216 − 1).

Program the channel NCO control registers to monitor the

appropriate SYNC pins.

Write the start synchronization enable bit and SYNC pin

enable bits high in the pin synchronization configuration

counter. When the count reaches 1, the channels are

activated or resynchronized.

Hop

Hop is a jump from one NCO frequency and/or phase offset to

a new NCO frequency and/or phase offset. This change in

frequency and/or phase offset can be synchronized via

microprocessor control (soft sync) or via an external sync signal

(pin sync).

AD6636PCB Datasheet(PDF) 47 Page - Analog Devices

AD6636PCB Datasheet(HTML) 47 Page - Analog Devices

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