AD9125 Analog Devices, AD9125 Datasheet - Page 38

• Manufacturer Part Number: AD9125
• Manufacturer: Analog Devices

Specifications of AD9125

• Resolution (bits): 16bit
• Dac Update Rate: 1GSPS
• Dac Settling Time: n/a
• Max Pos Supply (v): +3.47V
• Single-supply: No
• Dac Type: Current Out
• Dac Input Format: Par

AD9125
DATA RATES VS. INTERPOLATION MODES
Table 23 summarizes the maximum bus speed (f
supported input data rates, and the signal bandwidths for
various combinations of bus width modes and interpolation
rates. The maximum bus speed in any mode is 250 MHz. The
maximum DAC update rate (f
The real signal bandwidth supported is a fraction of the input
data rate, which depends on the interpolation filter (HB1, HB2,
or HB3) selected. The complex signal bandwidth supported is
twice the real signal bandwidth.
In general, 2× interpolation is best supported by enabling HB1,
and 4× interpolation is best supported enabling HB1 and HB2.
In some cases, power dissipation can be lowered by avoiding
HB1. If the bandwidth required is low enough, 2× interpolation
can be supported by using HB2, and 4× interpolation can be
supported by using HB2 and HB3.
COARSE MODULATION MIXING SEQUENCES
The coarse digital quadrature modulation occurs within the
interpolation filters. The modulation shifts the frequency
spectrum of the incoming data by the frequency offset selected.
The frequency offsets available are multiples of the input data
rate. The modulation is equivalent to multiplying the quadrature
input signal by a complex carrier signal, C(t), of the form
Table 23. Summary of Data Rates and Bandwidths vs. Interpolation Modes
Bus Width
Byte Mode
Word Mode
Dual-Word Mode
(8 Bits)
(16 Bits)
(32 Bits)
C ( t ) = cos( ω
c
t ) + j sin( ω
HB3
0
0
0
0
1
1
0
0
0
0
1
1
0
0
0
0
1
1
Filter Modes
HB2
0
0
1
1
1
1
0
0
1
1
1
1
0
0
1
1
1
1
c
t )
DAC
) in any mode is 1000 MHz.
HB1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
f
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
125
BUS
BUS
(Mbps)
), the
Rev. 0 | Page 38 of 56
f
62.5
62.5
62.5
62.5
62.5
62.5
125
125
125
125
125
125
250
250
250
250
250
125
DATA
(Mbps)
In practice, this modulation results in mixing functions as
shown in Table 22.
Table 22. Modulation Mixing Sequences
Modulation
f
f
3 × f
f
Note that
As shown in Table 22, the mixing functions of most of the modes
result in cross coupling samples between the I and Q channels.
The I and Q channels only operate independently in f
This means that real modulation using both the I and Q DAC
outputs can only be done in f
modes require complex input data and produce complex output
signals.
S
S
S
/2
/4
/8
S
/4
Real Signal Bandwidth (MHz)
31.25
25
15.625
25
15.625
25
62.5
50
31.25
50
31.25
50
125
100
62.5
100
62.5
50
r
=
Mixing Sequence
I = I, −I, I, −I, …
Q = Q, −Q, Q, −Q, …
I = I, Q, −I, −Q, …
Q = Q, −I, −Q, I, …
I = I, −Q, −I, Q, …
Q = Q, I, −Q, −I, …
I = I, r(I + Q), Q, r(−I + Q), −I, −r(I + Q), −Q, r(I − Q), …
Q = Q, r(Q − I), −I, −r(Q + I), −Q, r(−Q + I),I, r(Q + I), …
2
2
S
/2 mode. All other modulation
f
62.5
125
125
250
250
500
125
250
250
500
500
1000
250
500
500
1000
1000
1000
DAC
S
/2 mode.
(MHz)