MAX14945 Datasheet, PDF (13/21 Pages) Maxim Integrated Products – 2.75kVRMS Isolated 500kbps Half-Duplex RS-485

MAX14945
2.75kV_RMS Isolated 500kbps Half-Duplex RS-485/
RS-422 Transceiver with ±30kV ESD Protection
Pin Description (continued)
PIN
NAME REFERENCE
FUNCTION
Driver Output Enable. Drive DE high to enable bus driver outputs A and B. Drive DE low or
5
DE
GNDA
connect to GNDA to disable A and B. A and B are high impedance when DE is low. DE has
an internal 4.5µA pulldown to GNDA.
6
TXD
7
SBA
9, 15
10, 14
GNDB
N.C.
11
VLDO
12
A
13
B
16
VDDB
GNDA
GNDA
—
—
GNDB
GNDB
GNDB
GNDB
Driver Input. With DE high, a low on TXD forces the noninverting output (A) low and the inverting
output (B) high. Similarly, a high on TXD forces the noninverting output high and the inverting
output low. TXD has an internal 4.5µA pullup to VDDA.
Side B Active Indicator Output. SBA asserts low when side B is powered and working. SBA
has an internal 5kΩ pullup resistor to V_DDA.
Cable-Side Ground. GNDB is the ground reference for the internal LDO and the RS-485/RS-422
bus signals.
No Connection. Not internally connected.
LDO Power Input. Connect a minimum voltage of 4.68V to VLDO to power the cable-side
of the transceiver. Bypass VLDO to GNDB with both 0.1µF and 1µF capacitors as close to
the device as possible. To disable the internal LDO, leave VLDO unconnected or connect to
GNDB.
Noninverting Receiver Input and Noninverting Driver Output
Inverting Receiver Input and Inverting Driver Output
Cable-Side Power Input/Isolated LDO Power Output. Bypass VDDB to GNDB with both
0.1µF and 1μF capacitor as close as possible to the device. V_DDB is the output of the
internal LDO when power is applied to VLDO. When the internal LDO is not used (VLDO is
unconnected or connected to GNDB), VDDB is the positive supply input for the cable-side of
the IC.
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