AD9653BCPZ-125 Analog Devices, AD9653BCPZ-125 Datasheet - Page 27

• Manufacturer Part Number: AD9653BCPZ-125
• Description: the ad9653 is a quad, 16-bit, 125 msps analog-to-digital converter (adc) with an...
• Manufacturer: Analog Devices

Data Sheet
ADC output driver supplies to avoid modulating the clock signal
with digital noise. Low jitter, crystal-controlled oscillators make
the best clock sources. If the clock is generated from another
type of source (by gating, dividing, or other methods), it should
be retimed by the original clock at the last step.
Refer to the
Application Note
performance as it relates to ADCs.
POWER DISSIPATION AND POWER-DOWN MODE
As shown in Figure 70, the power dissipated by the
proportional to its sample rate. The digital power dissipation
does not vary significantly because it is determined primarily by
the DRVDD supply and bias current of the LVDS output drivers.
The
port or by asserting the PDWN pin high. In this state, the ADC
typically dissipates 2 mW. During power-down, the output
drivers are placed in a high impedance state. Asserting the
PDWN pin low returns the
mode. Note that PDWN is referenced to the digital output
driver supply (DRVDD) and should not exceed that supply
voltage.
Figure 70. Analog Core Power vs. f
AD9653
130
120
100
110
90
80
70
60
50
40
30
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
1
20
10 BITS
8 BITS
RMS CLOCK JITTER REQUIREMENT
Figure 69. Ideal SNR vs. Input Frequency and Jitter
AN-501 Application Note
is placed in power-down mode either by the SPI
for more in-depth information about jitter
40
ANALOG INPUT FREQUENCY (MHz)
10
V
REF
SAMPLE RATE (MSPS)
60
AD9653
= 1.3V
0.125ps
SAMPLE
0.25ps
0.5ps
1.0ps
2.0ps
80
for f
to its normal operating
V
REF
and the
IN
100
= 9.7 MHz, Four Channels
= 1.0V
100
AN-756
16 BITS
14 BITS
12 BITS
AD9653
120
1000
is
Rev. 0 | Page 27 of 40
Low power dissipation in power-down mode is achieved by
shutting down the reference, reference buffer, biasing networks,
and clock. Internal capacitors are discharged when entering
power-down mode and then must be recharged when returning
to normal operation. As a result, wake-up time is related to the
time spent in power-down mode, and shorter power-down
cycles result in proportionally shorter wake-up times. When
using the SPI port interface, the user can place the ADC in
power-down mode or standby mode. Standby mode allows the
user to keep the internal reference circuitry powered when
faster wake-up times are required. See the Memory Map section
for more details on using these features.
DIGITAL OUTPUTS AND TIMING
The
standard on default power-up. This can be changed to a low power,
reduced signal option (similar to the IEEE 1596.3 standard) via the
SPI. The LVDS driver current is derived on chip and sets the
output current at each output equal to a nominal 3.5 mA. A 100 Ω
differential termination resistor placed at the LVDS receiver
inputs results in a nominal 350 mV swing (or 700 mV p-p
differential) at the receiver.
When operating in reduced range mode, the output current is
reduced to 2 mA. This results in a 200 mV swing (or 400 mV p-p
differential) across a 100 Ω termination at the receiver.
The
receivers in custom ASICs and FPGAs for superior switching
performance in noisy environments. Single point-to-point net
topologies are recommended with a 100 Ω termination resistor
placed as close to the receiver as possible. If there is no far-end
receiver termination or there is poor differential trace routing,
timing errors may result. To avoid such timing errors, it is
recommended that the trace length be less than 24 inches and
that the differential output traces be close together and at equal
lengths. An example of the FCO and data stream with proper
trace length and position is shown in Figure 71. Figure 72 shows
the LVDS output timing example in reduced range mode.
Figure 71. LVDS Output Timing Example in ANSI-644 Mode (Default)
AD9653
AD9653
D0 500mV/DIV
D1 500mV/DIV
DCO 500mV/DIV
FCO 500mV/DIV
differential outputs conform to the ANSI-644 LVDS
LVDS outputs facilitate interfacing with LVDS
4ns/DIV
AD9653