AD9650-105EBZ Analog Devices Inc, AD9650-105EBZ Datasheet - Page 35

• Manufacturer Part Number: AD9650-105EBZ
• Description: 16Bit Hi SNR 105 Msps Dual ADC
• Manufacturer: Analog Devices Inc

Specifications of AD9650-105EBZ

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

determined by the sample rate and the characteristics of the
analog input signal.
Reducing the capacitive load presented to the output drivers
reduces digital power consumption.
By asserting PDWN (either through the SPI port or by asserting
the PDWN pin high), the AD9650 is placed in power-down
mode. In this state, the ADC typically dissipates 3.3 mW.
During power-down, the output drivers are placed in a high
impedance state. Asserting the PDWN pin low returns the
AD9650 to its normal operating mode.
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 must be recharged when returning to normal
operation.
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.
DIGITAL OUTPUTS
The AD9650 output drivers can be configured to interface with
1.8 V CMOS logic families. The AD9650 can also be configured
for LVDS outputs (standard ANSI or reduced output swing mode)
using a DRVDD supply voltage of 1.8 V.
In CMOS output mode, the output drivers are sized to provide
sufficient output current to drive a wide variety of logic families.
However, large drive currents tend to cause current glitches on
the supplies that may affect converter performance.
Applications requiring the ADC to drive large capacitive loads
or large fanouts may require external buffers or latches.
The default output mode is CMOS, with each channel output
on a separate bus, as shown in Figure 2. The output can also be
configured for interleaved CMOS via the SPI port. In interleaved
CMOS mode, the data for both channels is output through the
Channel A output pins, and the Channel B output is placed into
high impedance mode. The timing diagram for interleaved
CMOS output mode is shown in Figure 3.
The output data format can be selected for either offset binary
or twos complement by setting the SCLK/DFS pin when operating
in the external pin mode (see Table 12).
Table 13. Output Data Format
Input (V)
V
V
V
V
V
IN+
IN+
IN+
IN+
IN+
− V
− V
− V
− V
− V
IN−
IN−
IN−
IN−
IN−
Condition (V)
< −VREF − 0.5 LSB
= −VREF
= 0 V
= +VREF − 1.0 LSB
> +VREF − 0.5 LSB
Offset Binary Output Mode
0000 0000 0000 0000
0000 0000 0000 0000
1000 0000 0000 0000
1111 1111 1111 1111
1111 1111 1111 1111
Rev. 0 | Page 35 of 44
As detailed in the
Speed ADCs via SPI, the data format can be selected for offset
binary, twos complement, or gray code when using the SPI control.
Table 12. SCLK/DFS Mode Selection (External Pin Mode)
Voltage at Pin
AGND
AVDD
Digital Output Enable Function (OEB)
The AD9650 has a flexible three-state ability for the digital output
pins. The three-state mode is enabled using the OEB pin or
through the SPI. If the OEB pin is low, the output data drivers and
DCOs are enabled. If the OEB pin is high, the output data drivers
and DCOs are placed in a high impedance state. This OEB
function is not intended for rapid access to the data bus. Note
that OEB is referenced to the digital output driver supply
(DRVDD) and should not exceed that supply voltage.
When using the SPI, the data outputs and DCO of each channel
can be independently three-stated by using the output enable
bar bit (Bit 4) in Register 0x14.
TIMING
The AD9650 provides latched data with a pipeline delay of
12 clock cycles. Data outputs are available one propagation
delay (t
The length of the output data lines and loads placed on them
should be minimized to reduce transients within the AD9650.
These transients can degrade converter dynamic performance.
The lowest typical conversion rate of the AD9650 is 10 MSPS.
At clock rates below 10 MSPS, dynamic performance can
degrade.
Data Clock Output (DCO)
The AD9650 provides two data clock output (DCO) signals
intended for capturing the data in an external register. In CMOS
output mode, the data outputs are valid on the rising edge of DCO,
unless the DCO clock polarity has been changed via the SPI. In
LVDS output mode, the DCO and data output switching edges
are closely aligned. Additional delay can be added to the DCO
output using SPI Register 0x17 to increase the data setup time.
In this case, the Channel A output data is valid on the rising
edge of DCO, and the Channel B output data is valid on the
falling edge of DCO. See Figure 2, Figure 3, and Figure 4 for a
graphical timing description of the output modes.
PD
) after the rising edge of the clock signal.
Twos Complement Mode
1000 0000 0000 0000
1000 0000 0000 0000
0000 0000 0000 0000
0111 1111 1111 1111
0111 1111 1111 1111
AN-877
SCLK/DFS
Offset binary (default)
Twos complement
Application Note, Interfacing to High
SDIO/DCS
DCS disabled
DCS enabled
(default)
AD9650
ORx
1
0
0
0
1