How does the DAC function within this circuit?How do the transceiver work in this case?

Thread Starter


Joined Oct 20, 2020
I have this circuit which I have to study but I don't know how the DAC circuit works when combined with the other components. I understand the functioning of the DAC but not that of the other components.
What is the function of P5 component, what does it do?

Delta prime

Joined Nov 15, 2019
Hello there
What is the function of P5 component, what does it do?
This is straight from the data sheet if you could be more specific.
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General Description
The MAX481E, MAX483E, MAX485E, MAX487E–
MAX491E, and MAX1487E are low-power transceivers for
RS-485 and RS-422 communications in harsh environ-
ments. Each driver output and receiver input is protected
against ±15kV electro-static discharge (ESD) shocks,
without latchup. These parts contain one driver and one
receiver. The MAX483E, MAX487E, MAX488E, and
MAX489E feature reduced slew-rate drivers that minimize
EMI and reduce reflections caused by improperly termi-
nated cables, thus allowing error-free data transmission
up to 250kbps. The driver slew rates of the MAX481E,
MAX485E, MAX490E, MAX491E, and MAX1487E are not
limited, allowing them to transmit up to 2.5Mbps.
These transceivers draw as little as 120µA supply cur-
rent when unloaded or when fully loaded with disabled
drivers (see Selector Guide). Additionally, the MAX481E,
MAX483E, and MAX487E have a low-current shutdown
mode in which they consume only 0.5µA. All parts oper-
ate from a single +5V supply.
Drivers are short-circuit current limited, and are protected
against excessive power dissipation by thermal shutdown
circuitry that places their outputs into a high-impedance
state. The receiver input has a fail-safe feature that guar-
antees a logic-high output if the input is open circuit.
The MAX487E and MAX1487E feature quarter-unit-load
receiver input impedance, allowing up to 128 trans-
ceivers on the bus. The MAX488E–MAX491E are
designed for full-duplex communications, while the
MAX481E, MAX483E, MAX485E, MAX487E, and
MAX1487E are designed for half-duplex applications.
For applications that are not ESD sensitive see the pin-
and function-compatible MAX481, MAX483, MAX485,
MAX487–MAX491, and MAX1487


Joined Dec 31, 2017
P5 is a jumper to connect or disconnect R12 if needed. This resistor is used to terminate the line correctly when using long cable runs up to 4000ft