Datasheet

_______________Detailed Description
The MAX3471 half-duplex transceiver consumes only
1.6µA from a single +3.6V supply. Its wide 2.5V to 5.5V
supply voltage guarantees operation over the lifetime of
a lithium battery. This device contains one driver and
one receiver. Its true fail-safe receiver input guarantees
a logic-high receiver output when the receiver inputs
are open or shorted, or when they are connected to a
terminated transmission line with all drivers disabled.
Reduced-slew-rate drivers minimize EMI and reduce
reflections caused by improperly terminated cables,
allowing error-free data transmission up to 64kbps.
Receiver Input Filtering
The MAX3471 receiver operates at up to 64kbps and
incorporates input filtering in addition to input hystere-
sis. This filtering enhances noise immunity when differ-
ential signals have very slow rise and fall times.
The MAX3471 guarantees a logic-high receiver output
when the receiver inputs are shorted or open, or when
they are connected to a terminated transmission line
with all drivers disabled. This is accomplished by set-
ting the receiver threshold between -50mV and
-450mV. If the differential receiver input voltage (A-B) is
greater than or equal to -50mV, RO is a logic high. If
A-B is less than or equal to -450mV, RO is a logic low.
In the case of a terminated bus with all transmitters dis-
abled, the receiver’s differential input voltage is pulled
to 0V by the termination. With the MAX3471’s receiver
thresholds, this results in a logic high with a 50mV mini-
mum noise margin.
MAX3471
1.6µA, RS-485/RS-422, Half-Duplex,
Differential Transceiver for Battery-Powered Systems
6 _______________________________________________________________________________________
______________________________________________________________Pin Description
RECEIVER PROPAGATION DELAY
MAX3471toc17
B
DI
(2V/div)
(2V/div)
A-B
(2V/div)
R
O
(2V/div)
A
1µs/div
DRIVER PROPAGATION DELAY
MAX3471toc18
B
DI
(2V/div)
(2V/div)
A-B
(1V/div)
A
400ns/div
R = 1.5kΩ, C
L
= 100pF
GroundGND5
Noninverting Driver Output and Noninverting Receiver InputA6
Inverting Driver Output and Inverting Receiver InputB7
Positive Supply: +2.5V ≤ V
CC
≤ +5.5VV
CC
8
Driver Input. With DE high, a low on DI forces the noninverting output low and the inverting output high.
Similarly, a high on DI forces the noninverting output high and the inverting output low.
DI4
Driver Output Enable. Drive DE high to enable the driver outputs. These outputs are high impedance when
DE is low.
DE3
PIN
Receiver Output Enable. Drive RE low to enable RO; RO is high impedance when RE is high.RE
2
Receiver Output. When RE is low, if A - B ≥ -50mV, RO will be high; if A - B ≤ -450mV, RO will be low.
RO1
FUNCTIONNAME
Typical Operating Characteristics (continued)
(V
CC
= +3.6V, T
A
= +25°C, unless otherwise noted.)