AD9600ABCPZ-125 Analog Devices Inc, AD9600ABCPZ-125 Datasheet - Page 33

• Manufacturer Part Number: AD9600ABCPZ-125
• Description: 10Bit 125Msps Dual 1.8V PB Free ADC
• Manufacturer: Analog Devices Inc

Specifications of AD9600ABCPZ-125

• Number Of Bits: 10
• Sampling Rate (per Second): 125M
• Data Interface: Serial, SPI™
• Number Of Converters: 2
• Power Dissipation (max): 800mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-LFCSP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

SIGNAL MONITOR
The signal monitoring block provides additional information about
the signal being digitized by the ADC. The signal monitor computes
the rms input magnitude, the peak magnitude, and/or the number
of samples by which the magnitude exceeds a particular threshold.
Together, these functions can be used to gain insight into the
signal characteristics and to estimate the peak/average ratio or
even the shape of the complementary cumulative distribution
function (CCDF) curve of the input signal. This information
can be used to drive an AGC loop to optimize the range of the
ADC in the presence of real-world signals.
The signal monitor result values can be obtained from the part by
reading back Register 0x116 to Register 0x11B, using the SPI port
or the signal monitor SPORT output. The output contents of the
SPI-accessible signal monitor registers are set via the two signal
monitor mode bits of the signal monitor control register
(Address 0x112). Both ADC channels must be configured for
the same signal monitor mode. Separate SPI-accessible, 20-bit
signal monitor result (SMR) registers (Address 0x116 to Address
0x11B) are provided for each ADC channel. Any combination of
the signal monitor functions can also be output to the user via
the serial SPORT interface. These outputs are enabled using the
peak detector output enable, rms magnitude output enable, and
threshold crossing output enable bits in the signal monitor
SPORT control register (Address 0x111).
For each of the signal monitor measurements, a programmable
signal monitor period register (SMPR) controls the duration of
the measurement. This period is programmed as the number of
input clock cycles in the 24-bit signal monitor period register
located at Address 0x113, Address 0x114, and Address 0x115.
This register can be programmed with a period from 128 samples
to 16.78 (2
Because the dc offset of the ADC can be significantly larger
than the signal of interest (affecting the results from the signal
monitor), a dc correction circuit is included as part of the signal
monitor block to null the dc offset before measuring the power.
PEAK DETECTOR MODE
The magnitude of the input port signal is monitored over a
programmable period (determined by SMPR) to give the peak
value detected. This function is enabled by programming a
Logic 1 in the signal monitor mode bits of the signal monitor
control register (Address 0x112) or by setting the peak detector
output enable bit in the signal monitor SPORT control register
(Address 0x111). The 24-bit SMPR must be programmed before
activating this mode.
After enabling this mode, the value in the SMPR is loaded into
a monitor period timer and the countdown is started. The magni-
tude of the input signal is compared with the value in the
internal peak level holding register (not accessible to the user),
and the greater of the two values is updated as the current peak
level. The initial value in the peak level holding register is set to
24
) million samples.
Rev. B | Page 33 of 72
the current ADC input signal magnitude, and the comparison
continues until the monitor period timer reaches a count of 1.
When the monitor period timer reaches a count of 1, the 13-bit
value in the peak level holding register is transferred to the signal
monitor holding register (not accessible to the user) and can be
read through the SPI port or output through the SPORT serial
interface. The monitor period timer is reloaded with the value in
the SMPR, and the countdown is restarted. In addition, the value in
the peak level holding register is reset to the magnitude of the
first input sample, and the previously explained comparison and
update procedure continues.
Figure 67 is a block diagram of the peak detector logic. The
SMR register contains the absolute magnitude of the peak
detected by the peak detector logic.
RMS/MS MAGNITUDE MODE
In this mode, the root-mean-square (rms) or mean-square (ms)
magnitude of the input port signal is integrated (by adding an
accumulator) over a programmable period (determined by SMPR)
to give the rms or ms magnitude of the input signal. This mode
is set by programming Logic 0 in the signal monitor mode bits
of the signal monitor control register (Address 0x112) or by setting
the rms magnitude output enable bit in the signal monitor
SPORT control register (Address 0x111). The 24-bit SMPR,
representing the period over which integration is performed,
must be programmed before activating this mode.
After enabling the rms/ms magnitude mode, the value in the SMPR
is loaded into a monitor period timer, and the countdown is started
immediately. Each input sample is converted to floating-point
format and squared. It is then converted to an 11-bit fixed-point
format and added to the contents of the 24-bit accumulator. The
integration continues until the monitor period timer reaches a
count of 1.
When the monitor period timer reaches a count of 1, the square
root of the value in the accumulator is taken and transferred
(after some formatting) to the signal monitor holding register,
which can be read through the SPI port or output through the
SPORT serial port. The monitor period timer is reloaded with
the value in the SMPR, and the countdown is restarted. In addition,
MEMORY
* THESE ARE INTERNAL REGISTERS. THEY ARE NOT IN THE REGISTER
PORTS
MAP AND CANNOT BE ACCESSED BY USERS.
INPUT
FROM
FROM
MAP
PERIOD REGISTER
SIGNAL MONITOR
Figure 67. ADC Input Peak Detector Block Diagram
LOAD
MAGNITUDE
REGISTER*
COMPARE
STORAGE
A>B
CLEAR
LOAD
COUNTER
DOWN
SIGNAL MONITOR
REGISTER (SMR)*
LOAD
IS COUNT = 1?
HOLDING
AD9600
MAP/SPORT
MEMORY
TO