AD7994 Analog Devices, AD7994 Datasheet - Page 16

• Manufacturer Part Number: AD7994
• Description: 4 Channel, 12-Bit ADC with I2C Compatible Interface in 16-Lead TSSOP
• Manufacturer: Analog Devices

Specifications of AD7994

• Resolution (bits): 12bit
• # Chan: 4
• Sample Rate: 188kSPS
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref)
• Adc Architecture: SAR
• Pkg Type: SOP

AD7993/AD7994
TYPICAL CONNECTION DIAGRAM
Figure 22 shows the typical connection diagram for the AD7993/
AD7994. In Figure 22 the address select pin (AS) is tied to V
however, AS can also be tied to AGND or left floating, allowing
the user to select up to five AD7993/AD7994 devices on the
same serial bus. An external reference must be applied to the
AD7993/AD7994. This reference can be in the range of 1.2 V to
V
ADR03, or ADR381 can be used to supply the reference voltage
to the ADC.
SDA and SCL form the 2-wire I
face. External pull-up resisters are required for both SDA and
SCL lines.
The AD7993-0/AD7994-0 support standard and fast I
interface modes. The AD7993-1/AD7994-1 support standard,
fast, and high speed I
the AD7993/AD7994 in either standard or fast mode, up to five
AD7993/AD7994 devices can be connected to the bus as noted:
In high speed mode, up to three AD7993-1/AD7994-1 devices
can be connected to the bus.
Wake-up from shutdown prior to a conversion is approximately
1 µs, and conversion time is approximately 2 µs. The AD7993/
AD7994 enter shutdown mode again after each conversion,
which is useful in applications where power consumption is
a concern.
DD
3 × AD7993-0/AD7994-0 and 2 × AD7993-1/ AD7994-1
or
3 × AD7993-1/AD7994-1 and 2 × AD7994-0/AD7993-0
. A precision reference like the REF 19x family, AD780,
2
C interface modes. Therefore, if operating
REF 19x
2
C/SMBus-compatible inter-
0.1µF
0V to REF
INPUT
IN
1µF
Figure 22. AD7993/AD7994 Typical Connection Diagram
V
V
REF
IN
IN
4
1
IN
AD7993/
2
AD7994
C
GND
DD
Rev. 0 | Page 16 of 32
V
DD
;
10µF
CONVST
ALERT
SDA
SCL
AS
0.1µF
ANALOG INPUT
Figure 21 shows an equivalent circuit of the AD7993/AD7994’s
analog input structure. The two diodes, D1 and D2, provide
ESD protection for the analog inputs. Care must be taken to
ensure that the analog input signal does not exceed the supply
rails by more than 300 mV. This causes these diodes to become
forward biased and start conducting current into the substrate.
These diodes can conduct a maximum current of 10 mA
without causing irreversible damage to the part.
Capacitor C1 in Figure 21 is typically about 4 pF and primarily
can be attributed to pin capacitance. Resistor R1 is a lumped
component made up of the on resistance (R
(track-and-hold switch), and also includes the R
multiplexer. The total resistor is typically about 400 Ω. C2, the
ADC sampling capacitor, has a typical capacitance of 30 pF.
V
IN
V
4pF
C1
DD
R
P
R
P
R
Figure 21. Equivalent Analog Input Circuit
P
V
5V SUPPLY
DD
2-WIRE SERIAL
INTERFACE
D1
D2
CONVERSION PHASE—SWITCH OPEN
TRACK PHASE—SWITCH CLOSED
µC/µP
R1
30pF
C2
ON
) of a switch
ON
of the input