AD7699 Analog Devices, AD7699 Datasheet - Page 17

• Manufacturer Part Number: AD7699
• Description: 16-Bit, 8-Channel, 500 kSPS PulSAR ADC
• Manufacturer: Analog Devices

Specifications of AD7699

• Resolution (bits): 16bit
• # Chan: 8
• Sample Rate: 500kSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni,SE-Bip,SE-Uni
• Ain Range: (Vref) p-p,4 V p-p,Bip (Vref) x 0.5,Uni (Vref)
• Adc Architecture: SAR
• Pkg Type: CSP

Data Sheet
The analog inputs can be configured as
•
•
•
•
CH0+ (–)
CH0– (+)
CH1+ (–)
CH1– (+)
CH2+ (–)
CH2– (+)
CH3+ (–)
CH3– (+)
Figure 31A, single-ended referenced to system ground;
CFG[12:10] = 111
Figure 31B, bipolar differential with a common reference
point; COM = V
Unipolar differential with COM connected to a ground
sense; CFG[12:10] = 110
Figure 31C, bipolar differential pairs with INx− referenced
to V
Unipolar differential pairs with INx− referenced to a
ground sense; CFG[12:10] = 10X
In this configuration, the INx+ is identified by the channel
in CFG[9:7]. For example, for IN0 = IN1+ and IN1 =
IN1−, CFG[9:7] = 000
CFG[9:7] = 001
Figure 31D, inputs configured in any of the above
combinations (showing that the AD7699 can be configured
dynamically).
CH0+
CH1+
CH2+
CH3+
CH4+
CH5+
CH6+
CH7+
REF
Figure 31. Multiplexed Analog Input Configurations
/2; CFG[12:10] = 00X
A—8 CHANNELS,
C—4 CHANNELS,
SINGLE ENDED
DIFFERENTIAL
2
IN2
IN3
IN5
COM
GND
IN2
IN3
IN5
COM
GND
IN0
IN1
IN4
IN6
IN7
IN0
IN1
IN4
IN6
IN7
.
REF
2
.
/2; CFG[12:10] = 010
2
; for IN1 = IN1+ and IN0 = IN1−,
2
.
CH0+ (–)
CH0– (+)
CH1+ (–)
CH1– (+)
2
COM–
.
COM–
CH2+
CH3+
CH4+
CH5+
CH1+
CH2+
CH3+
CH4+
CH5+
CH0+
CH6+
CH7+
COMMON REFERENCE
2
.
D—COMBINATION
B—8 CHANNELS,
2
.
IN2
IN3
IN5
COM
IN0
IN1
IN4
IN6
IN7
COM
GND
GND
IN2
IN3
IN5
IN7
IN0
IN1
IN4
IN6
Rev. A | Page 17 of 28
Sequencer
The
channels in a IN0 to IN[7:0] fashion. Channels are scanned as
singles or pairs, with or without the temperature sensor, after
the last channel is sequenced.
The sequencer starts with IN0 and finishes with IN[7:0] set in
CFG[9:7]. For paired channels, the channels are paired
depending on the last channel set in CFG[9:7]. Note that the
channel pairs are always paired as IN (even) = INx+ and IN
(odd) = INx− regardless of CFG[7].
To enable the sequencer, CFG[2:1] are written to for initializing
the sequencer. After CFG[13:0] are updated, DIN must be held
low while reading data out (at least for Bit 13), or the CFG register
begins updating again.
While operating in a sequence, the CFG register can be changed
by writing 01
or single channel) or CFG[9:7] (last channel in sequence), the
sequence reinitializes and converts IN0 (or IN1) after CFG is
updated.
Examples
Bit[13], Bits[6:3], and Bit 0 are configured for the input and
sequencer.
As a first example, scan all IN[7:0] referenced to COM = GND
with the temperature sensor.
13
CFG
As a second example, scan three paired channels without the
temperature sensor and referenced to V
13
CFG
1
Source Resistance
When the source impedance of the driving circuit is low, the
AD7699
cantly affect the ac performance, especially total harmonic
distortion (THD). The dc performances are less sensitive to the
input impedance. The maximum source impedance depends on
the amount of THD that can be tolerated. The THD degrades as a
function of the source impedance and the maximum input
frequency.
X = don’t care.
AD7699
12
0
12
1
can be driven directly. Large source impedances signifi-
INCC
INCC
11
0
11
1
2
includes a channel sequencer useful for scanning
to CFG[2:1]. However, if changing CFG11 (paired
10
X
10
0
1
9
1
9
1
INx
INx
8
0
8
1
7
X
7
1
1
6
BW
6
BW
REF
5
5
/2.
REF
REF
4
4
3
3
AD7699
2
1
2
1
SEQ
SEQ
1
0
1
1
0
RB
0
RB