AD7870 Analog Devices, AD7870 Datasheet - Page 16

• Manufacturer Part Number: AD7870
• Description: LC2MOS Complete/ 12-Bit/ 100 kHz/ Sampling ADCs
• Manufacturer: Analog Devices

SKT5 is a 9-way D-type connector that is meant for serial inter-
facing only. An inverted DB9/SCLK output is also provided on
this connector for systems that accept data on a rising clock
edge. The SKT5 pinout is shown in Figure 27.
AD7870/AD7875/AD7876
SHORTING PLUG OPTIONS
There are seven shorting plug options that must be set before
using the board. These are outlined below:
LK1 Connects the analog input to a buffer amplifier. The
LK2 Selects either the ADC internal clock or an external
LK3 Configures the ADC 12/8/CLK input for the appropri-
LK4 Connects the ADC RD input directly to the two parallel
LK5– Connect the pull-up resistors R3, R4 and R5 to SSTRB,
LK7 SCLK and SDATA. These shorting plugs should be
analog input may also be connected to a component grid
for signal conditioning.
clock source.
ate serial or parallel interface.
connectors or to a decoded STRB and R/W input. This
shorting plug setting depends on the microprocessor e.g.,
the TMS32010 has a separate RD output while the
TMS32020 has STRB and R/W outputs.
removed for parallel interfacing.
Figure 27. SKT5, D-Type Connector Pinout
–16–
SKT1, SKT2 and SKT3 are three BNC connectors which pro-
vide input connections for the analog input, the CONVST input
and an external clock input. The use of an external clock source
is optional; there is a shorting plug (LK2) on the ADC CLK in-
put that must be connected to either –5 V (for the ADCs own
internal clock) or to SKT3.
POWER SUPPLY CONNECTIONS
The PCB requires two analog power supplies and one 5 V digi-
tal supply . The analog supplies are labelled V+ and V–, and the
range for both supplies is 12 V to 15 V (see silkscreen in Figure
29). Connection to the 5 V digital supply is made through any
of the connectors (SKT4 to SKT6). The –5 V supply required
by the ADC is generated from a voltage regulator on the V–
power supply input (IC3 in Figure 27).
COMPONENT LIST
IC1
IC2
IC3
IC4
IC5
C1, C3, C5, C7,
C9, C11
C2, C4, C6, C8,
C10, C12
R1, R2
R3*, R5*
R4*
LK1, LK2
LK3, LK4
LK5, LK6, LK7
SKT1, SKT2, SKT3 BNC Sockets
SKT4
SKT5
SKT6
*Required for Serial Communication only.
AD711 Op Amp
AD7870/AD7875/AD7876 Analog-to-
Digital Converter
MC79L05 –5 V Regulator
74HC00 Quad NAND Gate
74HC74 Dual D-Type Flip Flop
10 F Capacitors
0.1 F Capacitors
10 k Pull-Up Resistors
4.7 k Pull-Up Resistors
2 k Pull-Up Resistor
Shorting Plugs
26-Contact (2-Row) IDC Connector
9-Contact D-Type Connector
96-Contact (3-Row) Eurocard Connector
REV. B