AD7840ARS Analog Devices Inc, AD7840ARS Datasheet - Page 13

• Manufacturer Part Number: AD7840ARS
• Description: IC DAC 14BIT LOW POWER 5V 24SSOP
• Manufacturer: Analog Devices Inc

Specifications of AD7840ARS

• Rohs Status: RoHS non-compliant
• Settling Time: 2.5µs
• Number Of Bits: 14
• Data Interface: Serial, Parallel
• Number Of Converters: 1
• Voltage Supply Source: Dual ±
• Power Dissipation (max): 100mW
• Operating Temperature: -25°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SSOP

REV. B
DATA ACQUISITION BOARD
Figure 25 shows the AD7840 in a data acquisition circuit. The
corresponding printed circuit board (PCB) layout and silkscreen
are shown in Figures 26 to 28. The board layout has three inter-
face ports: one serial and two parallel. One of the parallel ports
is directly compatible with the ADSP-2100 evaluation board
expansion connector.
Some systems will require the addition of a re-construction filter
on the output of the AD7840 to complete the data acquisition
system. There is a component grid provided near the analog
output on the PCB which may be used for such a filter or any
other output conditioning circuitry. To facilitate this option,
there is a shorting plug (labeled LK1 on the PCB) on the analog
output track. If this shorting plug is used, the analog output
connects to the output of the AD7840; otherwise this shorting
plug can be omitted and a wire link used to connect the analog
output to the PCB component grid.
The board also contains a simple sample-and-hold circuit which
can be used on the output of the AD7840 to extend the very
good performance of the AD7840 over a wider frequency range.
A second wire link (labelled LK2 on the PCB) connects V
(SKT1) to either the output of this sample-and-hold circuit or
directly to the output of the AD7840.
INTERFACE CONNECTIONS
There are two parallel connectors, labeled SKT4 and SKT6,
and one serial connector, labeled SKT5. A shorting plug option
(LK8 in Figure 25) on the AD7840 CS/SERIAL input config-
ures the DAC for the appropriate interface (see Pin Function
Description).
SKT6 is a 96-contact (3-row) Eurocard connector which is di-
rectly compatible with the ADSP-2100 Evaluation Board Proto-
type Expansion Connector. The expansion connector on the
ADSP-2100 has eight decoded chip enable outputs labeled
ECE1 to ECE8. ECE6 is used to drive the AD7840 CS input
on the data acquisition board. To avoid selecting on-board
sockets at the same time, LK6 on the ADSP-2100 board must
be removed. The AD7840 and ADSP-2100 data lines are
aligned for left justified data transfer.
SKT4 is a 26-way (2-row) IDC connector. This connector con-
tains the same signal contacts as SKT6 and in addition contains
decoded R/W and STRB inputs which are necessary for
TMS32020 interfacing. This decoded WR can be selected via
LK4. The pinout for this connector is shown in Figure 29.
SKT5 is a nine-way D-type connector which is meant for serial
interfacing only. The evaluation board has the facility to invert
SYNC line via LK7. This is necessary for serial interfacing be-
tween the AD7840 and DSP processors such as the DSP56000.
The SKT5 pinout is shown in Figure 30.
SKT1, SKT2 and SKT3 are three BNC connectors which pro-
vide connections for the analog output, the LDAC input and an
external reference input. The use of an external reference is op-
tional; the shorting plug (LK3) connects the REF IN pin to ei-
ther this external reference or to the AD7840’s own internal
reference.
Wire links LK5 and LK6 connect the D11 and D10 inputs to
the data lines for parallel operation. In the serial mode, these
links allow the user to select the required format and justifica-
tion for serial data (see Table I).
OUT
–13–
POWER SUPPLY CONNECTIONS
The PCB requires two analog power supplies and one 5 V digi-
tal supply. Connections to the analog supplies are made directly
to the PCB as shown on the silkscreen in Figure 26. The con-
nections are labelled V+ and V– and the range for both of these
supplies is 12 V to 15 V. Connection to the 5 V digital supply is
made through any of the connectors (SKT4 to SKT6). The
–5 V analog supply required by the AD7840 is generated from
a voltage regulator on the V– power supply input (IC5 in
Figure 25).
SHORTING PLUG OPTIONS
There are eight shorting plug options which must be set before
using the board. These are outlined below:
LK1
LK2
LK3
LK4
LK5
LK6
LK7
LK8
COMPONENT LIST
IC1
IC2
IC3
IC4
IC5
IC6
C1, C3, C5, C7,
C11, C13, C15, C17
C2, C4, C6, C8,
C12, C14, C16, C18
C9
C10
R1, R2
R3
RP1, RP2
LK1, LK2, LK3,
LK4, LK5, LK6,
LK7, LK8
SKT1, SKT2, SKT3
SKT4
SKT5
SKT6
Connects the analog output to SKT1. The analog
output may also be connected to a component grid
for signal conditioning.
Selects either the AD7840 V
hold output.
Selects either the internal or external reference.
Selects the decoded R/W and STRB inputs for
TMS32020 interfacing.
Configures the D11/FORMAT input.
Configures the D10/JUSTIFY input.
Selects either the inverted or noninverted SYNC.
Selects either parallel or serial interfacing.
AD7840 Digital-to-Analog Converter
AD711 Op Amp
ADG201HS High Speed Switch
74HC221 Monostable
79L05 Voltage Regulator
74HC02
10 F Capacitors
0.1 F Capacitors
330 pF Capacitor
68 pF Capacitor
2.2 k Resistors
15 k Resistor
100 k Resistor Packs
Shorting Plugs
BNC Sockets
26-Contact (2-Row) IDC Connector
9-Contact D-Type Connector
96-Contact (3-Row) Eurocard
Connector
OUT
or the sample-and-
AD7840