AD7466BRTZ-R2 Analog Devices Inc, AD7466BRTZ-R2 Datasheet - Page 18

• Manufacturer Part Number: AD7466BRTZ-R2
• Description: IC ADC 12BIT 1.6V LP SOT23-6
• Manufacturer: Analog Devices Inc

Specifications of AD7466BRTZ-R2

• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Design Resources: Software Calibrated, 50 MHz to 9 GHz, RF Power Measurement System (CN0178)
• Number Of Bits: 12
• Sampling Rate (per Second): 200k
• Number Of Converters: 1
• Power Dissipation (max): 900µW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-6
• Resolution (bits): 12bit
• Sampling Rate: 200kSPS
• Input Channel Type: Single Ended
• Supply Voltage Range - Analog: 1.6V To 3.6V
• Supply Current: 300µA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-AD7466CBZ - BOARD EVALUATION FOR AD7466
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

AD7466/AD7467/AD7468
TYPICAL CONNECTION DIAGRAM
Figure 23 shows a typical connection diagram for the devices.
V
be well decoupled. This provides an analog input range of
0 V to V
The conversion result consists of four leading zeros followed by
the MSB of the 12-bit, 10-bit, or 8-bit result from the AD7466,
AD7467, or AD7468, respectively. See the Serial Interface
section. Alternatively, because the supply current required by
the AD7466/AD7467/AD7468 is so low, a precision reference
can be used as the supply source to the devices.
The REF19x series devices are precision micropower, low drop-
out voltage references. For the AD7466/AD7467/AD7468
voltage range operation, the REF193, REF192, and REF191 can
be used to supply the required voltage to the ADC, delivering
3 V, 2.5 V, and 2.048 V, respectively (see Figure 23). This con-
figuration is especially useful if the power supply is quite noisy
or if the system supply voltages are at a value other than 3 V or
2.5 V (for example, 5 V). The REF19x outputs a steady voltage to
the AD7466/AD7467/AD7468. If the low dropout REF192 is
used when the AD7466 is converting at a rate of 100 kSPS, the
REF192 needs to supply a maximum of 240 µA to the AD7466.
The load regulation of the REF192 is typically 10 ppm/mA
(REF192, V
for the 240 µA drawn from it. This corresponds to a 0.0098 LSB
error for the AD7466 with V
applications where power consumption is important, the
automatic power-down mode of the ADC and the sleep mode
of the REF19x reference should be used to improve power
performance. See the Normal Mode section.
Table 7 provides some typical performance data with various
references used as a V
conditions. The ADR318, for instance, is a 1.8 V band gap
voltage reference. Its tiny footprint, low power consumption,
and additional shutdown capability make the ADR318 ideal for
battery-powered applications.
0V TO V
680nF
REF
INPUT
is taken internally from V
DD
240µA
DD
.
V
GND
V
S
IN
DD
= 5 V), which results in an error of 2.4 ppm (6 µV)
Figure 23. REF192 as Power Supply to AD7466
0.1µF
AD7466
TANT
DD
1µF
2.5V
source under the same setup
SDATA
SCLK
DD
CS
DD
REF192
= 2.5 V from the REF192. For
and, therefore, V
10µF
INTERFACE
SERIAL
0.1µF
DD
should
5V
SUPPLY
µC/µP
Rev. B | Page 18 of 28
Table 7. AD7466 Performance for Voltage Reference IC
Reference Tied to V
ADR318 @ 1.8 V
ADR370 @ 2.048 V
ADR421 @ 2.5 V
ADR423 @ 3 V
ANALOG INPUT
An equivalent circuit of the AD7466/AD7467/AD7468 analog
input structure is shown in Figure 24. The two diodes, D1 and
D2, provide ESD protection for the analog inputs. Care must be
taken to ensure that the analog input signal never exceeds the
supply rails by more than 300 mV. This causes these diodes to
become forward-biased and to start conducting current into the
substrate. Capacitor C1 in Figure 24 is typically about 4 pF and
can primarily be attributed to pin capacitance. Resistor R1 is a
lumped component made up of the on resistance of a switch.
This resistor is typically about 200 Ω. Capacitor C2 is the ADC
sampling capacitor with a typical capacitance of 20 pF.
For ac applications, removing high frequency components
from the analog input signal by using a band-pass filter on
the relevant analog input pin is recommended. In applications
where harmonic distortion and signal-to-noise ratio are critical,
the analog input should be driven from a low impedance source.
Large source impedances significantly affect the ac performance
of the ADC. This might necessitate the use of an input buffer
amplifier. The choice of the op amp is a function of the particu-
lar application.
Table 8 provides typical performance data for various op amps
used as the input buffer under constant setup conditions.
Table 8. AD7466 Performance for Input Buffers
Op Amp in the
Input Buffer
AD8510
AD8610
AD797
V
IN
4pF
C1
Figure 24. Equivalent Analog Input Circuit
V
DD
DD
D1
D2 CONVERSION PHASE—SWITCH OPEN
TRACK PHASE—SWITCH CLOSED
AD7466 SNR Performance (dB)
30 kHz Input, V
70.75
71.45
71.42
R1
AD7466 SNR Performance (dB)
70.73
70.72
71.13
71.44
20pF
C2
DD
= 1.8 V