Rainbow Electronics MAX5184 - Manual (Page 14)

MAX5181/MAX5184
10-Bit, 40MHz, Current/Voltage-Output DACs
14 ______________________________________________________________________________________
relaxed requirements in resolution (10-bit AWGs). To
increase an AWG’s high-frequency accuracy, tempera-
ture stability, wide-band tuning, and past phase-contin-
uos frequency switching, the user may approach a
direct digital synthesis (DDS) AWG (Figure 8b). This
DDS loop supports standard waveforms that are repeti-
tive, such as sine, square, TTL, and triangular wave-
forms. DDS allows for precise control of the
data-stream input to the DAC. Data for one complete
output waveform cycle is sequentially stored in a RAM.
As the RAM addresses are changing, the DAC con-
verts the incoming data bits into a corresponding volt-
age waveform. The resulting output signal frequency is
proportional to the frequency rate at which the RAM
addresses are changed. Grounding and Power-Supply Decoupling
Grounding and power-supply decoupling strongly influ-
ence the MAX5181/MAX5184’s performance. Unwanted
digital crosstalk may couple through the input, refer-
ence, power-supply, and ground connections, which
may affect dynamic specifications like SNR or SFDR. In
addition, electromagnetic interference (EMI) can either
couple into or be generated by the MAX5181/
MAX5184. Therefore, grounding and power-supply
decoupling guidelines for high-speed, high-frequency
applications should be closely followed.
First, a multilayer PC board with separate ground and
power-supply planes is recommended. High-speed
signals should be run on controlled impedance lines
Figure 8b. Direct Digital Synthesis AWG
Figure 8a. Traditional Arbitrary Waveform Generation
9.6k*
400 Ω*
WAVEFORM
MEMORY
(RAM)
DV DD AV DD
*MAX5181 ONLY
MAX5181
MAX5184
10 ADR
FILTERED
WAVEFORM
(ANALOG OUTPUT)
LOWPASS
RECONSTRUCTION
FILTER
VARIABLE
fc
COUNTER
CLOCK
GENERATOR
DATA
9.6k*
400 Ω*
WAVEFORM
MEMORY
(RAM)
DV DD AV DD
*MAX5181 ONLY
MAX5181
MAX5184
10
DATA
ADR
A
D
D
E
R
FILTERED
WAVEFORM
(ANALOG OUTPUT)
LOWPASS
RECONSTRUCTION
FILTER
VARIABLE
fc
PHASE
ACCUMULATOR
ACCUMULATOR
FEEDBACK LOOP
FOR DATA BITS
CLOCK
GENERATOR
PIR
PHASE
INCREMENT
REGISTER