AD9269-20EBZ Analog Devices Inc, AD9269-20EBZ Datasheet - Page 25

• Manufacturer Part Number: AD9269-20EBZ
• Description: A/D Converter Eval. Board
• Manufacturer: Analog Devices Inc

Specifications of AD9269-20EBZ

• Silicon Manufacturer: Analog Devices
• Application Sub Type: ADC
• Kit Application Type: Data Converter
• Silicon Core Number: AD9269
• Kit Contents: Software, Evaluation Board
• Number Of Adc's: 2
• Number Of Bits: 16
• Sampling Rate (per Second): 20M
• Data Interface: Serial, SPI™
• Inputs Per Adc: 1 Differential
• Input Range: 2 Vpp
• Power (typ) @ Conditions: 96.9mW @ 20MSPS
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD9269
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The AD9269 is placed in power-down mode either by the SPI
port or by asserting the PDWN pin high. In this state, the ADC
typically dissipates 1 mW. During power-down, the output
drivers are placed in a high impedance state. Asserting the PDWN
pin low returns the AD9269 to its normal operating mode. Note
that PDWN is referenced to the digital output driver supply
(DRVDD) and should not exceed that supply voltage.
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.
DIGITAL OUTPUTS
The AD9269 output drivers can be configured to interface with
1.8 V to 3.3 V CMOS logic families. Output data can also be multi-
plexed onto a single output bus to reduce the total number of
traces required.
The CMOS 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 and
may affect converter performance.
Applications requiring the ADC to drive large capacitive loads
or large fanouts may require external buffers or latches.
The output data format can be selected to be either offset binary
or twos complement by setting the SCLK/DFS pin when operating
in the external pin mode (see Table 11).
Table 12. Output Data Format
Input (V)
VIN+ − VIN−
VIN+ − VIN−
VIN+ − VIN−
VIN+ − VIN−
VIN+ − VIN−
Condition (V)
< −VREF − 0.5 LSB
= −VREF
= 0
= +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 25 of 40
Table 11. SCLK/DFS Mode Selection (External Pin Mode)
Voltage at Pin
AGND
DRVDD
As detailed in the AN-877 Application Note, Interfacing to High
Speed ADCs via SPI, the data format can be selected for offset
binary, twos complement, or gray code when using the SPI control.
Digital Output Enable Function (OEB)
The AD9269 provides a flexible three-state ability for the digital
output pins. The three-state mode is enabled by the OEB pin or
through the SPI interface. 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 interface, the data outputs and DCO of
each channel can be independently three-stated by using the
output disable (OEB) bit, Bit 4 in Register 0x14.
TIMING
The AD9269 provides latched data with a pipeline delay of nine
clock cycles. Data outputs are available one propagation delay (t
after the rising edge of the clock signal.
Minimize the length of the output data lines and loads placed
on them to reduce transients within the AD9269. These transients
may degrade converter dynamic performance.
The lowest typical conversion rate of the AD9269 is 3 MSPS. At
clock rates below 3 MSPS, dynamic performance may degrade.
Data Clock Output (DCO)
The AD9269 provides two data clock output (DCO) signals that
are designed to capture the data in an external register. The CMOS
data outputs are valid on the rising edge of DCO unless the DCO
clock polarity has been changed via the SPI. See Figure 2 and
Figure 3 for a graphical timing description.
Twos Complement Mode
1000 0000 0000 0000
1000 0000 0000 0000
0000 0000 0000 0000
0111 1111 1111 1111
0111 1111 1111 1111
SCLK/DFS
Offset binary (default)
Twos complement
SDIO/DCS
DCS disabled
DCS enabled (default)
AD9269
OR
1
0
0
0
1
PD
)