ADN2814 Analog Devices, Inc., ADN2814 Datasheet - Page 18

• Manufacturer Part Number: ADN2814
• Description: Continuous Rate 10 Mb/s To 675 Mb/s Clock And Data Recovery Ic With Integrated Limiting Amp
• Manufacturer: Analog Devices, Inc.

ADN2814
The time to detect lock to harmonic is
where:
1/T
switched from OC-12 to OC-3, then T
ρ is the data transition density. Most coding schemes seek to
ensure that ρ = 0.5, for example, PRBS, 8B/10B.
When the ADN2814 is placed in lock to reference mode, the
harmonic detector is disabled.
SQUELCH MODE
Two SQUELCH modes are available with the ADN2814.
SQUELCH DATAOUT and CLKOUT mode is selected when
CTRLC[1] = 0 (default mode). In this mode, when the
SQUELCH input, Pin 27, is driven to a TTL high state, both
the clock and data outputs are set to the zero state to suppress
downstream processing. If the SQUELCH function is not
required, Pin 27 should be tied to VEE.
SQUELCH DATAOUT or CLKOUT mode is selected when
CTRLC[1] is 1. In this mode, when the squelch input is driven
to a high state, the DATAOUTN and DATAOUTP pins are
squelched. When the SQUELCH input is driven to a low state,
the CLKOUT pins are squelched. This is especially useful in
repeater applications, where the recovered clock may not be
needed.
I
The ADN2814 supports a 2-wire, I
driving multiple peripherals. Two inputs, serial data (SDA) and
serial clock (SCK), carry information between any devices
connected to the bus. Each slave device is recognized by a
unique address. The ADN2814 has two possible 7-bit slave
addresses for both read and write operations. The MSB of the
7-bit slave address is factory programmed to 1. B5 of the slave
address is set by Pin 19, SADDR5. Slave Address Bits [4:0] are
defaulted to all 0s. The slave address consists of the 7 MSBs of
an 8-bit word. The LSB of the word either sets a read or write
operation (see Figure 7). Logic 1 corresponds to a read
operation, while Logic 0 corresponds to a write operation.
To control the device on the bus, the following protocol must be
followed. First, the master initiates a data transfer by establish-
ing a start condition, defined by a high-to-low transition on
SDA while SCK remains high. This indicates that an address/
data stream follows. All peripherals respond to the start
condition and shift the next eight bits (the 7-bit address and the
R/W bit). The bits are transferred from MSB to LSB. The
peripheral that recognizes the transmitted address responds by
pulling the data line low during the ninth clock pulse. This is
known as an acknowledge bit. All other devices withdraw from
the bus at this point and maintain an idle condition. The idle
condition is where the device monitors the SDA and SCK lines
2
C INTERFACE
d
2
is the new data rate. For example, if the data rate is
16
× (T
d
/ρ)
2
C-compatible, serial bus
d
= 1/155.52 MHz.
Rev. 0 | Page 18 of 28
waiting for the start condition and correct transmitted address.
The R/W bit determines the direction of the data. Logic 0 on the
LSB of the first byte means that the master writes information to
the peripheral. Logic 1 on the LSB of the first byte means that
the master reads information from the peripheral.
The ADN2814 acts as a standard slave device on the bus. The data
on the SDA pin is eight bits long supporting the 7-bit addresses plus
the R/W bit. The ADN2814 has eight subaddresses to enable the
user-accessible internal registers (see Table 6 through Table 10). It,
therefore, interprets the first byte as the device address and the
second byte as the starting subaddress. Auto-increment mode is
supported, allowing data to be read from or written to the
starting subaddress and each subsequent address without
manually addressing the subsequent subaddress. A data transfer
is always terminated by a stop condition. The user can also
access any unique subaddress register on a one-by-one basis
without updating all registers.
Stop and start conditions can be detected at any stage of the
data transfer. If these conditions are asserted out of sequence
with normal read and write operations, then they cause an
immediate jump to the idle condition. During a given SCK high
period, the user should issue one start condition, one stop
condition, or a single stop condition followed by a single start
condition. If an invalid subaddress is issued by the user, the
ADN2814 does not issue an acknowledge and returns to the idle
condition. If the user exceeds the highest subaddress while
reading back in auto-increment mode, then the highest
subaddress register contents continue to be output until the
master device issues a no-acknowledge. This indicates the end
of a read. In a no-acknowledge condition, the SDATA line is not
pulled low on the ninth pulse. See Figure 8 and Figure 9 for
sample read and write data transfers and Figure 10 for a more
detailed timing diagram.
REFERENCE CLOCK (OPTIONAL)
A reference clock is not required to perform clock and data
recovery with the ADN2814. However, support for an optional
reference clock is provided. The reference clock can be driven
differentially or single-ended. If the reference clock is not being
used, then REFCLKP should be tied to VCC, and REFCLKN
can be left floating or tied to VEE (the inputs are internally
terminated to VCC/2). See Figure 21 through Figure 23 for
sample configurations.
The REFCLK input buffer accepts any differential signal with a
peak-to-peak differential amplitude of greater than 100 mV (for
example, LVPECL or LVDS) or a standard single-ended, low
voltage TTL input, providing maximum system flexibility.
Phase noise and duty cycle of the reference clock are not
critical, and 100 ppm accuracy is sufficient.