EVAL-AD7693CBZ Analog Devices Inc, EVAL-AD7693CBZ Datasheet - Page 12

• Manufacturer Part Number: EVAL-AD7693CBZ
• Description: BOARD EVALUATION FOR AD7693
• Manufacturer: Analog Devices Inc
• Series: PulSAR®r

Specifications of EVAL-AD7693CBZ

• Number Of Adc's: 1
• Number Of Bits: 16
• Sampling Rate (per Second): 500k
• Data Interface: Serial
• Inputs Per Adc: 1 Differential
• Input Range: ±VREF
• Power (typ) @ Conditions: 18mW @ 500kSPS
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD7693
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD7693
THEORY OF OPERATION
CIRCUIT INFORMATION
The AD7693 is a fast, low power, single-supply, precise, 16-bit
ADC using a successive approximation architecture.
The AD7693 is capable of converting 500,000 samples per
second (500 kSPS) and powers down between conversions.
When operating at 1 kSPS, for example, it consumes 40 μW
typically, ideal for battery-powered applications.
The AD7693 provides the user with an on-chip track-and-hold
and does not exhibit pipeline delay or latency, making it ideal
for multiple multiplexed channel applications.
The AD7693 is specified from 4.5 V to 5.5 V and can be
interfaced to any 1.8 V to 5 V digital logic family. It is housed in
a 10-lead MSOP or a tiny 10-lead QFN (LFCSP) that combines
space savings and allows flexible configurations.
It is pin-for-pin compatible with the 16-bit
AD7688
CONVERTER OPERATION
The AD7693 is a successive approximation ADC based on a
charge redistribution DAC. Figure 25 shows the simplified
schematic of the ADC. The capacitive DAC consists of two
identical arrays of 16 binary-weighted capacitors, which are
connected to the two comparator inputs.
and with the 18-bit
GND
REF
IN+
IN–
AD7690
and AD7691.
32,768C
32,768C
AD7687
16,384C
16,384C
MSB
MSB
and
Figure 25. ADC Simplified Schematic
4C
4C
Rev. 0 | Page 12 of 24
2C
2C
C
C
During the acquisition phase, terminals of the array tied to the
comparator’s input are connected to GND via SW+ and SW−.
All independent switches are connected to the analog inputs.
Thus, the capacitor arrays are used as sampling capacitors and
acquire the analog signal on the IN+ and IN− inputs. When the
acquisition phase is complete and the CNV input goes high, a
conversion phase is initiated. When the conversion phase
begins, SW+ and SW− are opened first. The two capacitor
arrays are then disconnected from the inputs and connected to
the GND input. Therefore, the differential voltage between the
IN+ and IN− inputs captured at the end of the acquisition phase
is applied to the comparator inputs, causing the comparator to
become unbalanced. By switching each element of the capacitor
array between GND and REF, the comparator input varies by
binary-weighted voltage steps (V
The control logic toggles these switches, starting with the MSB,
to bring the comparator back into a balanced condition. After
the completion of this process, the part returns to the
acquisition phase, and the control logic generates the ADC
output code and a busy signal indicator.
Because the AD7693 has an on-board conversion clock, the
serial clock, SCK, is not required for the conversion process.
C
C
LSB
LSB
SW+
SW–
COMP
SWITCHES CONTROL
CONTROL
LOGIC
CNV
REF
/2, V
BUSY
OUTPUT CODE
REF
/4 ... V
REF
/32,768).