EVAL-ADM3061EEBZ/EVAL-ADM3061EEB1Z User Guide UG-1172
Rev. 0 | Page 3 of 9
EVALUATION BOARD HARDWARE
SETTING UP THE EVALUATION BOARD
The EVAL-ADM3061EEBZ and EVAL-ADM3061EEB1Z
evaluation boards are powered by connecting a 3.3 V or 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.
Corresponding labeled test points allow monitoring of the power
supply to the evaluation board and 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 a universal asynchronous receiver/
transmitter (UART). The EVAL-ADM3061EEBZ and EVAL-
ADM3061EEB1Z 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 EVAL-
ADM3061EEBZ and EVAL-ADM3061EEB1Z evaluation boards
also have a right hand SMA connector (DI), which is the preferred
option for delivering a 50 Mbps signal to the evaluation boards.
Connections to an RS-485 bus are made via a screw
terminal block, J5. For the EVAL-ADM3061EEBZ or EVAL-
ADM3061EEB1Z 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
on the right 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 EVAL-ADM3061EEBZ and EVAL-ADM3061EEB1Z
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 can be removed or replaced with a different value resistor
as needed. Inserting both LK3 and LK4 presents a 60 Ω load to
the RS-485 driver.
Biasing Resistors for Bus Idle Failsafe
Although the ADM3061E 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 Configuration
Link Connection Description
LK1 A Connects the receiver enable (RE) input of the ADM3061E to VCC. This setting disables the receiver.
B Connects the RE input of the ADM3061E to GND. This setting enables the receiver.
C Connects the RE input of the ADM3061E to the J3-2 terminal block connector.
D Connects the RE input of the ADM3061E to the DE input; that is, the input for both RE and DE 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.
LK2 A Connects the DE input of the ADM3061E to VCC. This setting enables the driver.
B Connects the DE input of the ADM3061E to GND. This setting disables the driver.
C Connects the DE input of the ADM3061E to the J3-3 terminal block connector.
LK3 Inserted Connects the 120 Ω RT1 termination resistor across the RS-485 A pin and B pin.
Not inserted Disconnects the 120 Ω RT1 termination resistor across the RS-485 A pin and B pin.
LK4 Inserted Connects the 120 Ω RT2 termination resistor across the RS-485 A pin and B pin.
Not inserted Disconnects the 120 Ω RT2 termination resistor across the RS-485 A pin and B pin.