AD7641BSTZ Analog Devices Inc, AD7641BSTZ Datasheet - Page 15

• Manufacturer Part Number: AD7641BSTZ
• Description: IC ADC 18BIT 2MSPS SAR 48-LQFP
• Manufacturer: Analog Devices Inc

Specifications of AD7641BSTZ

• Data Interface: Serial, Parallel
• Number Of Bits: 18
• Sampling Rate (per Second): 2M
• Number Of Converters: 1
• Power Dissipation (max): 92mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP
• Resolution (bits): 18bit
• Sampling Rate: 2MSPS
• Input Channel Type: Differential
• Supply Current: 23mA
• Digital Ic Case Style: QFP
• No. Of Pins: 48
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-AD7641CBZ - BOARD EVALUATION FOR AD7641
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

APPPLICATIONS INFORMATION
CIRCUIT INFORMATION
The AD7641 is a very fast, low power, single-supply, precise
18-bit ADC using successive approximation architecture. The
AD7641 features different modes to optimize performances
according to the applications. In warp mode, the AD7641 is
capable of converting 2,000,000 samples per second (2 MSPS).
The AD7641 provides the user with an on-chip track-and-hold,
successive approximation ADC that does not exhibit any
pipeline or latency, making it ideal for multiple multiplexed
channel applications.
The AD7641 can operate from a single 2.5 V supply and
interface to either 5 V, 3.3 V, or 2.5 V digital logic. It is housed
in a 48-lead LQFP package or a tiny 48-lead LFCSP package,
which combines space savings with flexibility and allows the
AD7641 to be configured as either a serial or a parallel
interface. The AD7641 is pin-to-pin-compatible and is a
speed upgrade of the AD7674, AD7678, and AD7679.
CONVERTER OPERATION
The AD7641 is a successive approximation ADC based on a
charge redistribution DAC. Figure 21 shows the simplified
schematic of the ADC. The capacitive DAC consists of two
identical arrays of 16 binary weighted capacitors that are
connected to the two comparator inputs.
During the acquisition phase, terminals of the array tied to the
comparator’s input are connected to AGND via SW+ and SW−.
All independent switches are connected to the analog inputs.
Therefore, the capacitor arrays are used as sampling capacitors
and acquire the analog signal on the IN+ and IN− inputs. A
conversion phase is initiated once the acquisition phase is complete
and the CNVST input goes low. 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 REFGND input. Therefore, the differential voltage between
the inputs (IN+ and IN−) captured at the end of the acquisition
phase is applied to the comparator inputs, causing the
REFGND
REF
IN+
IN–
131,072C
131,072C 65,536C
MSB
MSB
65,536C
Figure 21. ADC Simplified Schematic
4C
4C
Rev. 0 | Page 15 of 28
2C
2C
C
C
comparator to become unbalanced. By switching each element
of the capacitor array between REFGND and REF, the comparator
input varies by binary weighted voltage steps (V
throughV
starting with the MSB first, to bring the comparator back into a
balanced condition. After the completion of this process, the
control logic generates the ADC output code and brings BUSY
output low.
MODES OF OPERATION
The AD7641 features three modes of operations: wideband
warp, warp, and normal. Each of these modes is more suitable
for specific applications.
The wideband warp (WARP = high, NORMAL = high) and
warp (WARP = high, NORMAL = low) modes allow the fastest
conversion rate of up to 2 MSPS. However, in these modes, the
full specified accuracy is guaranteed only when the time between
conversions does not exceed 1 ms. If the time between two
consecutive conversions is longer than 1 ms (for instance after
power-up), the first conversion result should be ignored. These
modes make the AD7641 ideal for applications where both high
accuracy and fast sample rates are required. Wideband warp
mode offers slightly improved linearity and THD over warp mode.
Normal mode ( NORMAL = low, WARP = low) is the fastest
mode (1.5 MSPS) without any limitation on time between
conversions. This mode makes the AD7641 ideal for
asynchronous applications, such as data acquisition systems,
where both high accuracy and fast sample rates are required.
C
C
LSB
LSB
AGND
AGND
REF
SW–
SW+
COMP
/131072). The control logic toggles these switches,
SWITCHES
CONTROL
CONTROL
CNVST
LOGIC
OUTPUT
CODE
BUSY
REF
/2, V
AD7641
REF
/4