AD9231BCPZ-20 Analog Devices Inc, AD9231BCPZ-20 Datasheet - Page 22

• Manufacturer Part Number: AD9231BCPZ-20
• Description: 12 Bit, 20 MSPS Dual Low Power ADC
• Manufacturer: Analog Devices Inc

Specifications of AD9231BCPZ-20

• Number Of Bits: 12
• Sampling Rate (per Second): 20M
• Data Interface: Serial, SPI™
• Number Of Converters: 2
• Power Dissipation (max): 73.3mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-LFCSP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD9231
VOLTAGE REFERENCE
A stable and accurate 1.0 V voltage reference is built into the
AD9231. The VREF can be configured using either the internal
1.0 V reference or an externally applied 1.0 V reference voltage.
The various reference modes are summarized in the sections
that follow. The Reference Decoupling section describes the
best practices PCB layout of the reference.
Internal Reference Connection
A comparator within the AD9231 detects the potential at the
SENSE pin and configures the reference into two possible modes,
which are summarized in Table 10. If SENSE is grounded, the
reference amplifier switch is connected to the internal resistor
divider (see Figure 46), setting VREF to 1.0 V.
Table 10. Reference Configuration Summary
Selected Mode
Fixed Internal Reference
Fixed External Reference
1.0µF
Figure 46. Internal Reference Configuration
VIN+A/VIN+B
VIN–A/VIN–B
0.1µF
SENSE
VREF
SELECT
SENSE Voltage (V)
AGND to 0.2
AVDD
LOGIC
ADC
0.5V
CORE
ADC
Resulting VREF (V)
1.0 internal
1.0 applied to external VREF pin
Rev. A | Page 22 of 36
If the internal reference of the AD9231 is used to drive multiple
converters to improve gain matching, the loading of the reference
by the other converters must be considered. Figure 47 shows
how the internal reference voltage is affected by loading.
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
0
0
0.2
Figure 47. VREF Accuracy vs. Load Current
0.4
Resulting Differential Span (V p-p)
2.0
2.0
0.6
LOAD CURRENT (mA)
INTERNAL VREF = 0.993V
0.8
1.0
1.2
1.4
1.6
1.8
2
.0