EVAL-ADM3066EEBZ/EVAL-ADM3066EEB1Z User Guide UG-1131
Rev. 0 | Page 3 of 9
EVALUATION BOARD HARDWARE
SETTING UP THE EVALUATION BOARD
The E VA L -ADM3066EEBZ and E VA L-ADM3066EEB1Z
evaluation boards are powered by connecting a 3.0 V or 5.5 V
power supply to the J1 screw terminals for VCC and GND at the
top of the evaluation board. A 10 µF decoupling capacitor, C3, is
fitted at the connector between VCC and GND. The VCC pin of
the RS-485 transceiver is fitted with a 100 nF decoupling
capacitor, C1, with a second footprint for an optional additional
capacitor, C2. VIO can be connected with VCC or a separate 1.8 V
power supply.
Corresponding labeled test points allow monitoring of the
power supply to the evaluation board and the probe reference to
ground.
INPUT AND OUTPUT CONNECTIONS
Digital input and output signals are connected via the J3 screw
terminal block, allowing wire connections from the evaluation
boards to a signal generator or UART. The EVA L -ADM3066EEBZ
and E VA L -ADM3066EEB1Z include connections for data input
(DI), receiver output (RO), receiver enable (RE), and driver
enable (DE). Alternatively, jumper connections can drive these
inputs and/or connect them to VCC and GND (see Table 1). The
E VA L-ADM3066EEBZ and E VA L -ADM3066EEB1Z evaluation
boards also have an SMA right angle jack (DI), which is the
preferred option for delivering a high speed 50 Mbps signal to
the evaluation boards.
Connections to an RS-485 bus are made via a screw terminal block,
J5. For the E VA L -ADM3066EEBZ or E VA L-ADM3066EEB1Z
half-duplex boards, there are two bus input/output signals, A
and B, for noninverting and inverting signals, respectively. The
bus cable can also include a common ground connection or
shield and can also be connected to the J5 screw terminal block
of the evaluation boards. Test points are available on the
evaluation boards and are appropriately labeled for all digital
and bus input/output signals.
OTHER BOARD COMPONENTS
The E VA L -ADM3066EEBZ and E VA L -ADM3066EEB1Z
evaluation boards include footprints for termination resistors,
RT1 and RT2, as well as pull-up and pull-down resistors, R1 and
R2. Termination resistors of 120 Ω are fitted to the evaluation
board; these resistors can be removed or replaced with a
different value resistor as needed. Inserting both LK3 and LK4
adds a 60 Ω load to the RS-485 driver.
Biasing Resistors for Bus Idle Fail-Safe
Although the ADM3066E has a built-in receiver fail-safe for the
bus idle condition, there are footprints on the evaluation boards
for fitting the R2 pull-up resistor to VCC on A, as well as the R1
pull-down resistor to GND on B. These resistors can be fitted if
the user is connecting to other devices that require such external
biasing resistors on the bus. The exact value required for a
200 mV minimum differential voltage in the bus idle condition
depends on the supply voltage (for example, 960 Ω for 3.3 V
and 1440 Ω for 5 V).
For more information about the bus idle fail-safe, see the
AN-960 Application Note, RS-485/RS-422 Circuit
Implementation Guide.
Table 1. Jumper Configurations
Link Connection Description
LK1 A Connects the receiver enable (RE) input of the ADM3066E to VCC. This setting disables the receiver.
B Connects the RE input of the ADM3066E to GND. This setting enables the receiver.
C Connects the RE input of the ADM3066E to the J3-2 terminal block connector.
RE
input of the ADM3066E to the J3-3 terminal block connector; that is, the input for both
RE
is set by LK1. This setting ensures that when the driver is enabled, the receiver is disabled, or when the driver is
disabled, the receiver is enabled.
Connects the DE input of the ADM3066E to V
CC
. This setting enables the driver.
B Connects the DE input of the ADM3066E to GND. This setting disables the driver.
C Connects the DE input of the ADM3066E to the J3-2 terminal block connector.
LK3 Inserted Connects the 120 Ω RT1 termination resistor across the RS-485 A and B pins.
Not inserted Disconnects the 120 Ω RT1 termination resistor across the RS-485 A and B pins.
LK4 Inserted Connects the 120 Ω RT2 termination resistor across the RS-485 A and B pins.
Disconnects the 120 Ω RT2 termination resistor across the RS-485 A and B pins.
LK6 Inserted Connects VCC with VIO.
CC
IO.