AD7651ACP Analog Devices Inc, AD7651ACP Datasheet - Page 15

• Manufacturer Part Number: AD7651ACP
• Description: IC ADC 16BIT UNIPOLAR 48-LFCSP
• Manufacturer: Analog Devices Inc
• Series: PulSAR®r

Specifications of AD7651ACP

• Rohs Status: RoHS non-compliant
• Number Of Bits: 16
• Sampling Rate (per Second): 100k
• Data Interface: Serial, Parallel
• Number Of Converters: 1
• Power Dissipation (max): 45mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-VFQFN, CSP Exposed Pad
• For Use With: EVAL-AD7651CBZ - BOARD EVALUATION FOR AD7651

CIRCUIT INFORMATION
The AD7651 is a very fast, low power, single supply, precise
16-bit analog-to-digital converter (ADC).
The AD7651 provides the user with an on-chip track/hold,
successive approximation ADC that does not exhibit any
pipeline or latency, making it ideal for multiple multiplexed
channel applications.
The AD7651 can be operated from a single 5 V supply and can
be interfaced to either 5 V or 3 V digital logic. It is housed in
either a 48-lead LQFP or a 48-lead LFCSP that saves space and
allows flexible configurations as either a serial or parallel inter-
face. The AD7651 is pin-to-pin compatible with PulSAR ADCs.
CONVERTER OPERATION
The AD7651 is a successive-approximation ADC based on a
charge redistribution DAC. F
matic of the ADC. The capacitive DAC consists of an array of 16
binary weighted capacitors and an additional LSB capacitor. The
comparator’s negative input is connected to a dummy capacitor
of the same value as the capacitive DAC array.
REFGND
INGND
REF
IN
igure 20
32,768C
shows a simplified sche-
16,384C
MSB
4C
Figure 20. ADC Simplified Schematic
Rev. 0 | Page 15 of 28
2C
65,536C
C
During the acquisition phase, the common terminal of the array
tied to the comparator's positive input is connected to AGND
via SW
input IN. Thus, the capacitor array is used as a sampling
capacitor and acquires the analog signal on IN. Similarly, the
dummy capacitor acquires the analog signal on INGND.
When CNVST goes LOW, a conversion phase is initiated. When
the conversion phase begins, SW
capacitor array and dummy capacitor are then disconnected
from the inputs and connected to REFGND. Therefore, the
differential voltage between IN and INGND 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 REFGND and REF,
the comparator input varies by binary weighted voltage steps
(V
switches, starting with the MSB, to bring the comparator back
into a balanced condition.
After this process is completed, the control logic generates the
ADC output code and brings the BUSY output LOW.
C
REF
LSB
/2, V
A
. All independent switches are connected to the analog
SW
SW
REF
COMP
A
B
/4, …V
SWITCHES
CONTROL
REF
/65536). The control logic toggles these
CONTROL
CNVST
LOGIC
A
OUTPUT
BUSY
CODE
and SW
02964-0-005
B
are opened. The
AD7651