AD9216 Analog Devices, AD9216 Datasheet - Page 24

• Manufacturer Part Number: AD9216
• Description: 10-Bit, 65/80/105 MSPS Dual A/D Converter
• Manufacturer: Analog Devices

Specifications of AD9216

• Resolution (bits): 10bit
• # Chan: 2
• Sample Rate: 105MSPS
• Interface: Par
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p,(Vref) p-p,1 V p-p,2 V p-p
• Adc Architecture: Pipelined
• Pkg Type: CSP

AD9216
VOLTAGE REFERENCE
A stable and accurate 0.5 V voltage reference is built into
the AD9216. The input range can be adjusted by varying the
reference voltage applied to the AD9216, using either the inter-
nal reference with different external resistor configurations or
an externally applied reference voltage. The input span of the
ADC tracks reference voltage changes linearly.
Internal Reference Connection
A comparator within the AD9216 detects the potential at the
SENSE pin and configures the reference into three possible
states, which are summarized in Table 9. If SENSE is grounded,
the reference amplifier switch is connected to the internal resistor
divider (see Figure 47), setting VREF to 1 V. If a resistor divider
is connected, as shown in Figure 48, the switch is again set to the
SENSE pin. This puts the reference amplifier in a noninverting
mode with the VREF output defined as
Table 9. Reference Configuration Summary
Selected Mode
External Reference
Programmable Reference
Internal Fixed Reference
VREF = 0.5 × (1 + R2 / R1 )
SENSE Voltage
AVDD
0.2 V to VREF
AGND to 0.2 V
Rev. A | Page 24 of 40
Resulting VREF (V)
N/A
0.5 × (1 + R2/R1)
1.0
Note: The optimum performance is obtained with VREF =
1.0 V; performance degrades as VREF (and full scale) reduces
(see Figure 25). In all reference configurations, REFT and REFB
drive the ADC core and establish its input span. The input
range of the ADC always equals twice the voltage at the refer-
ence pin for either an internal or an external reference.
10µF
Figure 47. Internal Reference Configuration (One Channel Shown)
SENSE
0.1µF
VIN+
VIN–
VREF
Resulting Differential Span (V p-p)
2 × External Reference
2 × VREF (see Figure 48)
2.0
SELECT
LOGIC
AD9216
0.5V
CORE
ADC
REFB
REFT
0.1µF
0.1µF
0.1µF
10µF