LTC2873H Ver la hoja de datos (PDF) - Analog Devices
Número de pieza
componentes Descripción
Lista de partido
LTC2873H Datasheet PDF : 32 Pages
| |||
LTC2873
PIN FUNCTIONS
VEE (Pins 1, 10, 25): Generated Negative Supply Voltage
for RS232 Driver (–6.3V). Tie all pins together and connect
1µF capacitor between VEE (Pin 10) and GND. Exposed
pad (Pin 25) must be soldered to PCB to maintain low
thermal resistance.
RO (Pin 2): RS485 Differential Receiver Output and RS232
Receiver Output. Logic level referenced to GND and VL.
485/232 (Pin3): Interface Select Input. A logic low enables
RS232 mode and a high enables RS485 mode. The mode
determines which transceiver inputs and outputs are ac-
cessible at the LTC2873 pins. Logic level referenced to
GND and VL. Do not float.
RE485 (Pin4): RS485 Receiver Enable. In RS485 mode, a
logic high disables the RS485 receiver, leaving its output
Hi-Z and a logic low enables the RS485 receiver. This input
has no function in RS232 mode (485/232 low). Logic level
referenced to GND and VL. Do not float.
DE485/F232 (Pin 5): RS485 Driver Enable and RS232 Fast
Mode Enable. In RS485 mode (485/232 high), a logic low
disables the RS485 driver leaving the driver outputs in a
Hi-Z state and a logic high enables the RS485 driver. In
RS232 mode (485/232 low), a logic high enables Fast mode
with maximum data rate of 1Mbps. A logic low enables
Slow mode with a maximum data rate of 250kbps. Logic
level referenced to GND and VL. Do not float.
DI (Pin 6): RS485 and RS232 Driver Input. Logic level
referenced to GND and VL. Do not float.
SHDN (Pin7): Shutdown Control. A logic low disables the
LTC2873 into low power shutdown state, independent
of the other inputs. Driver and receiver outputs become
Hi-Z. Logic level referenced to GND and VL. Do not float.
GND (Pin 8, 11, 16, 20): Ground. Tie all four pins together.
CAP (Pin 9): Charge Pump Capacitor for Generated Negative
Supply Voltage VEE. Connect a 220nF capacitor between
CAP and SW.
SW (Pin 12): Switch Pin. Connect 10µH inductor between
SW and VCC. See Inductor Selection section for further
details.
VDD (Pin 13): Generated Positive Supply Voltage for
RS232 Driver (+7.0V). Connect 1µF capacitor between
VDD and GND.
VCC (Pin 14, 18, 21): Input Supply (3V to 5.5V). Tie all
three pins together and connect a 2.2µF or larger capacitor
between VCC (adjacent to VDD) and GND.
B/RI (Pin 15): RS485 Negative Receiver Input and Driver
Output. In RS232 mode, this is the RS232 receiver input.
A/DO (Pin 17): RS485 Positive Receiver Input and Driver
Output. In RS232 mode, this is the RS232 driver output.
NC (Pin 19): Not connected internally.
VL (Pin 22): Logic Supply (1.7V to 5.5V) for the Receiver
Outputs, Driver Inputs, and Control Inputs. Bypass this
pin to GND with a 0.1µF capacitor if not tied to VCC. Keep
VL ≤ VCC for operation guaranteed to meet specifications.
However, VL > VCC will not damage the device, provided
that absolute maximum limits are respected. See “VL Logic
Supply and Logic Pins” in Applications section for more
information.
LB (Pin 23): Loopback Enable. A logic high enables logic
loopback diagnostic mode, internally routing the driver
input logic signals to the receiver output pins. This applies
to RS232 and RS485 operation. The targeted receiver
must be enabled for the loopback signal to be available
on its output. A logic low disables Loopback mode. In
Loopback mode, signals are not inverted from driver
inputs to receiver outputs. Logic level referenced to GND
and VL. Do not float.
TE485 (Pin24): RS485 Termination Enable. In RS485 mode,
a logic low enables a 120Ω resistor between pins A/DO
and B/RI. A logic high opens the resistor between A/DO
and B/RI, leaving the pins unterminated. In RS485 mode,
the 5k resistor between B/RI and GND is never engaged.
In RS232 mode, the 120Ω resistor between A/DO and B/
RI is never engaged, regardless of the state of TE485, and
the 5k resistor between B/RI and GND is always engaged.
Logic level referenced to GND and VL. Do not float.
REV B
10
For more information www.analog.com
Share Link: 