Analog Devices EVAL-ADM2485EB3Z, Руководство пользователя

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Evaluation Board User Guide UG-213
Rev. 0 | Page 3 of 12
EVALUATION BOARD CONFIGURATIONS
3.3 V HALF DUPLEX WITH BUS BIASING ON
RECEIVER INPUTS
The EVAL-ADM2485EB3Z board is shipped in a 3.3 V half-duplex
configuration without any bus biasing resistors inserted by
default. Bus biasing resistors can be fitted on the receiver input
by inserting Resistors R3 and R4. Jumpers LK11 and LK13 must
be inserted for the bus biasing resistors to be active. Both bus
biasing resistors, R3 and R4, must be used together; one cannot
be fitted without the other. The default jumper settings are
shown in Table 1. The transformer inserted as T1 for the 3.3 V
version of the evaluation board is the DA2304_AL with a turns
ratio of 1:2.2. The DA2304_AL allows enough headroom for the
ADP667 LDO to output a regulated 5 V output.
5 V HALF DUPLEX WITH BUS BIASING ON
RECEIVER INPUTS
The EVAL-ADM2485EB5Z board is shipped in a 5 V half-duplex
configuration without any bus biasing resistors inserted by
default. Bus biasing resistors can be fitted on the receiver input
by inserting Resistors R3 and R4. Jumpers LK11 and LK13 must
be inserted for the bus biasing resistors to be active. Both bus
biasing resistors, R3 and R4, must be used together; one cannot
be fitted without the other. The default jumper settings are
shown in Table 1. The transformer inserted as T1 for the 5 V
version of the evaluation board is the DA2303_AL with a turns
ratio of 1:1.5. The DA2303_AL allows enough headroom for the
ADP667 LDO to output a regulated 5 V output.
A termination resistor can be fitted on the receiver input by
inserting RT1. The value of the termination resistor should be
equal to the characteristic impedance of the cable used. To
activate the termination resistor, Jumper LK12 must be inserted.
POWERING THE ISOLATED SIDE (VDD2)
The isolated side, V
DD2
, of the EVAL-ADM2485EB3Z can
be powered through the DA2304_AL, with a turns ratio of 1:2.2,
or from an external 5 V source. LK1 is used to switch between
the two sources.
The isolated side, V
DD2
, of the EVAL-ADM2485EB5Z can
be powered through the DA2303_AL, with a turns ratio of 1:1.5,
or from an external 5 V source. LK1 is used to switch between
the two sources.
CHOOSING A TRANSFORMER
There is a built-in transformer on the evaluation board, but
there is also the option of using a custom transformer. Jumper
LK2 and Jumper LK3 are used to choose the transformer. By
inserting Jumper LK2 and Jumper LK3 in Position A, the built-
in transformer on the board is selected. Both Jumper LK2 and
Jumper LK3 must be in the same position. A custom trans-
former can be used by inserting Jumper LK2 and Jumper LK3
into Position C. The custom transformer is fitted on D1_
patchwork, D2_patchwork, SKD1_patchwork, and SKD2_
patchwork.
Table 1. Board Configurations and Jumper Settings
Configuration Jumpers Fitted Jumpers Open
Half Duplex Without Bus Biasing, Without Termination Resistor LK11, LK12, LK13
Half Duplex Without Bus Biasing, with Termination Resistor LK12 LK11, LK13
Half Duplex with Bus Biasing on Receiver, Without Termination
Resistor
LK11, LK13 LK12
Half Duplex with Bus Biasing on Receiver, with Termination Resistor LK11, LK12, LK13
Powering the Bus Side Using the Regulator on the Board LK1 (Position B) LK1 (Position A)
Powering the Bus Side Using an External Power Supply LK1 (Position A) LK1 (Position B)
Using the Transformer on the Board LK2 (Position A), LK3 (Position A) LK2 (Position C), LK3 (Position C)
Using a Custom Transformer Fitted on D1_patchwork,
D2_patchwork, SKD1_patchwork, and SKD2_patchwork
LK2 (Position C), LK3 (Position C) LK2 (Position A), LK3 (Position A)
Using the SMA Connector for RxD LK8 (Position A) LK8 (Position B)
Using the Screw Terminal for RxD LK8 (Position B) LK8 (Position A)
Using the SMA Connector for TxD LK5 (Position B) LK5 (Position A)
Using the Screw Terminal for TxD LK5 (Position A) LK5 (Position B)
RE high LK4 (Position A)
RE low LK4 (Position B)
Using the Screw Terminal for RE LK4 (Position C)
RTS High LK6 (Position A)
RTS Low LK6 (Position B)
Using the Screw Terminal for RTS LK6 (Position C)
Tie RE and RTS Together (Note Only One Jumper Can Be Inserted,
Either LK4 or LK6)
LK14 and (LK4 or LK6) LK4 or LK6