LTC2871IFE#PBF Linear Technology, LTC2871IFE#PBF Datasheet - Page 20

• Manufacturer Part Number: LTC2871IFE#PBF
• Description: IC, RS232-RS485 TXRX, 200MBPS, 5.5V, TSSOP-38
• Manufacturer: Linear Technology

Specifications of LTC2871IFE#PBF

• Device Type: Transceiver
• No. Of Drivers: 2
• Supply Voltage Range: 3V To 5.5V
• Driver Case Style: TSSOP
• No. Of Pins: 38
• Operating Temperature Range: -40°C To +85°C
• Rohs Compliant: Yes
• Ic Interface Type: RS232, RS485

LTC2870/LTC2871
APPLICATIONS INFORMATION
Inrush Current and Supply Overshoot Precaution
In certain applications fast supply slew rates are generated
when power is connected. If the V
than 4.5V and its rise time is faster than 10μs, the pins
V
during start-up. When supply voltage is applied to V
voltage difference between V
current flowing through inductor L1 and capacitors C1 and
C2. The peak inrush current must not exceed 2A. To avoid
this condition, add a 1Ω resistor as shown in Figure 14.
This precaution is not relevant for supply voltages below
4.5V or rise times longer than 10μs.
20
DD
and SW can exceed their absolute maximum values
0V
Figure 14. Supply Current Overshoot Protection
for Input Supplies of 4.5V of Higher
≤10μs
5V
R1
1Ω
1/8W
C4
2.2μF
CURRENT
V
INRUSH
CC
10μH
L1
CC
V
SW
220nF
C2
1μF
DD
and V
C1
CC
DD
GND
CAP
voltage is greater
generates inrush
28701 F14
CC
, the
V
A separate logic supply pin V
LTC2871 to interface with any logic signal from 1.7V to
5.5V. All logic I/Os use V
operation, V
power-up, if V
damaged, but behavior of the device is not guaranteed.
If V
capacitor to GND.
RS232 and RS485 driver outputs are undriven and the
RS485 termination resistors are disabled when V
is grounded or V
Although all logic input pins reference V
supply, they can be driven up to 7V, independent of V
V
by more than 1V for proper operation. Logic input pins
do not have internal biasing devices to pull them up or
down. They must be driven high or low to establish valid
logic levels; do not float.
RS485 Driver
The RS485 driver provides full RS485/RS422 compati-
bility. When enabled, if DI is high, Y – Z is positive. With
the driver disabled the Y and Z output resistance is greater
than 96kΩ (typically 125kΩ) to ground over the entire
common mode range of –7V to +12V. This resistance is
equivalent to the input resistance on these lines when the
driver is configured in half-duplex mode and Y and Z act
as the RS485 receiver inputs.
Driver Overvoltage and Overcurrent Protection
The RS232 and RS485 driver outputs are protected from
short circuits to any voltage within the absolute maximum
range ±15V. The maximum current in this condition is 90mA
for the RS232 driver and 250mA for the RS485 driver.
If the RS485 driver output is shorted to a voltage greater
than V
may flow from the driver output back to V
power supply or loading cannot sink this excess current,
clamp V
1N4734) to prevent an overvoltage condition on V
L
CC
Logic Supply and Logic Pins
, with the exception of FEN, which must not exceed V
L
is not connected to V
CC
, when it is active, positive current of up to 100mA
CC
to GND with a Zener diode (e.g., 5.6V, 1W,
L
L
should not be greater than V
is higher than V
CC
is disconnected.
L
as their high supply. For proper
CC
L
, bypass V
CC
allows the LTC2870 and
, the device will not be
CC
L
L
. If the system
as their high
with a 0.1μF
CC
. During
L
or V
CC
L
28701f
.
and
CC
L