AD9600ABCPZ-150 Analog Devices Inc, AD9600ABCPZ-150 Datasheet - Page 30

• Manufacturer Part Number: AD9600ABCPZ-150
• Description: 10Bit 150Msps Dual 1.8V PB Free ADC
• Manufacturer: Analog Devices Inc

Specifications of AD9600ABCPZ-150

• Number Of Bits: 10
• Sampling Rate (per Second): 150M
• Data Interface: Serial, SPI™
• Number Of Converters: 2
• Power Dissipation (max): 890mW
• 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

AD9600
ADC OVERRANGE AND GAIN CONTROL
In receiver applications, it is desirable to have a mechanism to
reliably determine when the converter is about to be clipped.
The standard overflow indicator provides after-the-fact infor-
mation on the state of the analog input that is of limited usefulness.
Therefore, it is helpful to have a programmable threshold below
full scale that allows time to reduce the gain before the clip
actually occurs. In addition, because input signals can have
significant slew rates, latency of this function is of major concern.
Highly pipelined converters can have significant latency. A good
compromise is to use the output bits from the first stage of the
ADC for this function. Latency for these output bits is very low,
and overall resolution is not highly significant. Peak input signals
are typically between full scale and 6 dB to 10 dB below full
scale. A 3-bit or 4-bit output provides adequate range and
resolution for this function.
Via the SPI port, the user can provide a threshold above which
an overrange output would be active. As long as the signal is below
that threshold, the output should remain low. The fast detect
output pins can also be programmed via the SPI port so that one of
the pins functions as a traditional overrange pin for customers
who currently use this feature. In this mode, all 12 bits of the
converter are examined in the traditional manner, and the output is
high for the condition normally defined as overflow. In either
mode, the magnitude of the data is considered in the calculation
of the condition (but the sign of the data is not considered). The
threshold detection responds identically to positive and negative
signals outside the desired magnitude range.
FAST DETECT OVERVIEW
The AD9600 contains circuitry to facilitate fast overrange detec-
tion, allowing very flexible external gain control implementations.
Each ADC has four fast detect output pins that are used to output
information about the current state of the ADC input level. The
function of these pins is programmable via the fast detect mode
select bits and the fast detect enable bit in Register 0x104, allowing
range information to be output from several points in the internal
datapath. These pins can also be set up to indicate the presence of
overrange or underrange conditions, according to programmable
threshold levels. Table 14 shows the six configurations available
for the fast detect pins.
Rev. B | Page 30 of 72
Table 14. Fast Detect Mode Select Bits Settings
Fast Detect
Mode Select Bits
(Register 0x104 [3:1])
000
001
010
011
100
101
1
2
ADC FAST MAGNITUDE
When the fast detect output pins are configured to output the ADC
fast magnitude (that is, when the fast detect mode select bits are
set to 0b000), the information presented is the ADC level from an
early converter stage with only a two-clock-cycle latency (when
in CMOS output mode). Using the fast detect output pins in
this configuration provides the earliest possible level indication
information. Because this information is provided early in the
datapath, there is a significant uncertainty in the level indicated.
The nominal levels, along with the uncertainty indicated by the
ADC fast magnitude, are shown in Table 15.
Table 15. ADC Fast Magnitude Nominal Levels with
Fast Detect Mode Select Bits = 000
ADC Fast Magnitude on
FD [3:0] Pins
0000
0001
0010
0011
0100
0101
0110
0111
1000
The fast detect pins are FD0A/FD0B to FD9A/FD9B for the CMOS mode
configuration and FD0+/FD0− to FD9+/FD9− for the LVDS mode
configuration.
See the ADC Overrange (OR) and Gain Switching sections for more
information about OR, C_UT, F_UT, F_LT, IG, and DG.
FD [3]
ADC fast magnitude
ADC fast magnitude
Nominal Input
Magnitude
Below FS (dB)
<−24
−24 to −14.5
−14.5 to −10
−10 to −7
−7 to −5
−5 to −3.25
−3.25 to −1.8
−1.8 to −0.56
−0.56 to 0
OR
OR
Fast Detect (FD) Pins of Each ADC
(see
(see
ADC fast magnitude (see
ADC fast magnitude
Table 17
Table 17
Information Presented on
(see
FD [2]
Table 16
C_UT
F_UT
)
)
Nominal Input
Magnitude
Uncertainty (dB)
Minimum to −18.07
−30.14 to −12.04
−18.07 to −8.52
−12.04 to −6.02
−8.52 to −4.08
−6.02 to −2.5
−4.08 to −1.16
−2.5 to FS
−1.16 to 0
)
FD [1]
OR
C_UT
F_UT
IG
Table 15
FD [0]
OR
F_LT
F_LT
F_LT
DG
1, 2
)