AD9246-125EBZ Analog Devices Inc, AD9246-125EBZ Datasheet - Page 17

• Manufacturer Part Number: AD9246-125EBZ
• Description: BOARD EVAL FOR 125MSPS AD9246
• Manufacturer: Analog Devices Inc

Specifications of AD9246-125EBZ

• Design Resources: Using AD8376 to Drive Wide Bandwidth ADCs for High IF AC-Coupled Appls (CN0002) Driving AD9233/46/54 ADCs in AC-Coupled Baseband Appls (CN0051)
• Number Of Adc's: 1
• Number Of Bits: 14
• Sampling Rate (per Second): 125M
• Data Interface: Serial
• Inputs Per Adc: 1 Differential
• Input Range: 2 Vpp
• Power (typ) @ Conditions: 458mW @ 125MSPS
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD9246-125
• Silicon Manufacturer: Analog Devices
• Application Sub Type: ADC
• Kit Application Type: Data Converter
• Silicon Core Number: AD9246
• Kit Contents: Board
• Power Dissipation Pd: 458mW
• Input Channels Per Adc: 1
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 9. Reference Configuration Summary
Selected Mode
External Reference
Internal Fixed Reference
Programmable Reference
Internal Fixed Reference
VOLTAGE REFERENCE
A stable and accurate voltage reference is built into the AD9246.
The input range is adjustable by varying the reference voltage
applied to the AD9246, using either the internal reference or an
externally applied reference voltage. The input span of the ADC
tracks reference voltage changes linearly. The various reference
modes are summarized in the following sections. The Reference
Decoupling section describes the best practices and require-
ments for PCB layout of the reference.
Internal Reference Connection
A comparator within the AD9246 detects the potential at the
SENSE pin and configures the reference into four possible
states, as summarized in Table 9. If SENSE is grounded, the
reference amplifier switch is connected to the internal resistor
divider (see Figure 42), setting VREF to 1 V.
Connecting the SENSE pin to VREF switches the reference
amplifier input to the SENSE pin, completing the loop and
providing a 0.5 V reference output.
2V p-p
ANALOG INPUT
ANALOG INPUT
0.1µF
P
SENSE Voltage
AVDD
VREF
0.2 V to VREF
AGND to 0.2 V
A
0.1µF
0.1µF
C
D
Figure 41. Differential Input Configuration Using the AD8352
Figure 40. Differential Double Balun Input Configuration
S
R
D
0Ω
0Ω
S
R
G
16
1
2
3
4
5
P
Rev. A | Page 17 of 44
0.1µF
0.1µF
V
AD8352
CC
Resulting VREF (V)
N/A
0.5
1.0
8, 13
14
0
0.1µF
5 .
×
25Ω
25Ω
0.1µF
11
10
⎛ +
⎜
⎝
1
R2
R1
0.1µF
0.1µF
If a resistor divider is connected external to the chip as shown
in Figure 43, the switch sets to the SENSE pin. This puts the
reference amplifier in a noninverting mode with the VREF
output defined as
If the SENSE pin is connected to AVDD, the reference amplifier
is disabled, and an external reference voltage can be applied to
the VREF pin (see the External Reference Operation section).
The input range of the ADC always equals twice the voltage at
the reference pin for either an internal or an external reference.
0.1µF
⎞
⎟
⎠
(see Figure 43)
VREF
200Ω
200Ω
R
R
C
=
0.1µF
0
R
R
5 .
C
⎛ +
⎜
⎝
1
VIN+
VIN–
R2
R1
AD9246
⎞
⎟
⎠
VIN+
VIN–
AD9246
CML
CML
Resulting Differential
Span (V p-p)
2 × External Reference
1.0
2 × VREF
2.0
AD9246