MAX5893 Maxim Integrated Products, MAX5893 Datasheet - Page 24

• Manufacturer Part Number: MAX5893
• Description: 12-Bit/ 500Msps Interpolating and Modulating Dual DAC with CMOS Inputs
• Manufacturer: Maxim Integrated Products

The MAX5893 features digital modulation at frequen-
cies of f
input to the modulator. f
interpolation modes. In 8x interpolation mode, f
equals f
always the same as the input data rate to the modula-
tor, f
In complex modulation mode, data from the second
interpolation filter is frequency mixed with the on-chip
in-phase and quadrature (I/Q) local oscillator (LO).
Complex modulation provides the benefit of image
sideband rejection when combined with an external
quadrature modulator commonly found in wireless
communication systems.
In the f
be used. The modulator multiplies successive input data
samples by the sequence [1, 0, -1, 0] for a cos(ωt). The
modulator modulates the input signal up to f
ing upper and lower images around f
ture LO sin(ωt) is realized by delaying the cos(ωt)
sequence by one clock cycle. Using complex modula-
tion, complex IF is generated. The complex IF combined
with an external quadrature modulator provides image
rejection. The sign of the LO can be changed to allow
the user to select whether the upper or the lower image
should be rejected (bit 1 of register 01h).
When f
signal is multiplied by [-1, 1] on both channels. This pro-
duces images around f
modulation mode is not available for this LO frequency.
12-Bit, 500Msps Interpolating and Modulating
Dual DAC with CMOS Inputs
Figure 13. (a) Modulator in Complex Modulation Mode; (b) Modulator in Real Modulation Mode
24
IM
______________________________________________________________________________________
.
LO
IM
IM
DAC
/2 is chosen as the LO frequency, the input
= f
/2 and f
IM
/2. The output rate of the modulator is
/4 mode, real or complex modulation can
IM
/4, where f
I-CHANNEL
INPUT DATA
Q-CHANNEL
INPUT DATA
IM
IM
/2. The complex image-reject
equals f
IM
Digital Modulator
cos(ωt)
cos(ωt)
sin(ωt)
sin(ωt)
is the data rate at the
DAC
IM
(a)
in 1x, 2x, and 4x
/4. The quadra-
IM
∑
∑
/4, creat-
I-CHANNEL
OUTPUT DATA
TO
FIR3
Q-CHANNEL
OUTPUT DATA
IM
I-CHANNEL
INPUT DATA
Q-CHANNEL
INPUT DATA
The outputs of the modulator can be expressed as:
in complex modulation, e
in complex modulation, e
where ω = 2 x π x f
For real modulation, the outputs of the modulator can
be expressed as:
If more than one MAX5893 is used, their LO phases
can be synchronized by simultaneously releasing
RESET. This sets the MAX5893 to its predefined initial
phase.
The MAX5893 can be reset by holding the RESET pin
low for 10ns. This will program the control registers to
their default values in Table 2. During power-on, RESET
must be held low until all power supplies have stabi-
lized. Alternatively, programming bit 5 of address 00h
to a logic-high also resets the MAX5893 after power-up.
I t
I t
Q t
Q t
( )
( )
cos(ωt)
cos(ωt)
( )
( )
sin(ωt)
sin(ωt)
=
=
=
=
A t
A t
(b)
A t
A t
( )
( )
I t
Q t
( )
( )
( )
LO
×
×
( )
×
×
=
cos
cos
.
=
sin
sin
A t
A t
( )
∑
∑
( ) ( )
( )
+jwt
-jwt
( )
( )
ω
ω
( )
ω
ω
t B t
t
×
t
t
I-CHANNEL
OUTPUT DATA
TO
FIR3
Q-CHANNEL
OUTPUT DATA
×
−
+
cos
+
+
B t
cos
B t
B t
( )
( )
( )
( )
ω
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( )
×
ω
×
t
×
×
sin
t
sin
cos
cos
Device Reset
( )
( )
ω
ω
( )
( )
t
ω
ω
t
t
t