APPLICATIONS INFOR
參數(shù)資料
型號: LTC1545IG#TR
廠商: Linear Technology
文件頁數(shù): 4/16頁
文件大小: 0K
描述: IC TXRX SOFTWARE SELECTBL 36SSOP
標準包裝: 2,000
類型: 收發(fā)器
驅動器/接收器數(shù): 5/5
電源電壓: 4.75 V ~ 5.25 V
安裝類型: 表面貼裝
封裝/外殼: 36-SSOP(0.209",5.30mm 寬)
供應商設備封裝: 36-SSOP
包裝: 帶卷 (TR)
12
LTC1545
APPLICATIONS INFORMATION
WU
U
DTE vs DCE Operation
The DCE/DTE pin acts as an enable for Driver 3/Receiver
1 in the LTC1543, and Driver 3/Receiver 1 in the LTC1545.
The LTC1543/LTC1545 can be configured for either DTE
or DCE operation in one of two ways: a dedicated DTE or
DCE port with a connector of appropriate gender, or a port
with one connector that can be configured for DTE or DCE
operation by rerouting the signals to the LTC1543/LTC1545
using a dedicated DTE cable or dedicated DCE cable.
A dedicated DTE port using a DB-25 male connector is
shown in Figure 22. The interface mode is selected by logic
outputs from the controller or from jumpers to either VCC
or GND on the mode select pins. A dedicated DCE port
using a DB-25 female connector is shown in Figure 23.
A port with one DB-25 connector, can be configured for
either DTE or DCE operation is shown in Figure 24. The
configuration requires separate cables for proper signal
routing in DTE or DCE operation. For example, in DTE
mode, the TXD signal is routed to Pins 2 and 14 via Driver
1 in the LTC1543. In DCE mode, Driver 1 now routes the
RXD signal to Pins 2 and 14.
Compliance Testing
A European standard EN 45001 test report is available for
the LTC1343/LTC1545/LTC1344A chipset. A copy of the
test report is available from LTC or TUV Telecom Services
Inc. (formerly Detecon Inc.)
The title of the report is:
Test Report No. NET2/071601/98.
The address of TUV Telecom Services Inc. is:
TUV Telecom Services Inc.
Suite 107
1775 Old Highway 8
St. Paul, MN 55112 USA
Tel. +1 (612) 639-0775
Fax. +1 (612) 639-0873
Any mismatch in the driver rise and fall times or skew in
the driver propagation delays will force current through
the center termination resistor to ground, causing a high
frequency common mode spike on the A and B terminals.
The common mode spike can cause EMI problems that are
reduced by capacitor C1 which shunts much of the com-
mon mode energy to ground rather than down the cable.
No-Cable Mode
The no-cable mode (M0=M1= M2= D4ENB=1, R4EN = 0)
is intended for the case when the cable is disconnected
from the connector. The charge pump, bias circuitry,
drivers and receivers are turned off, the driver outputs are
forced into a high impedance state, and the supply current
drops to less than 200
A.
Charge Pump
The LTC1543 uses an internal capacitive charge pump to
generate VDD and VEE as shown in Figure 21. A voltage
doubler generates about 8V on VDD and a voltage inverter
generates about – 7.5V for VEE. Four 1F surface mounted
tantalum or ceramic capacitors are required for C1, C2, C3
and C4. The VEE capacitor C5 should be a minimum of
3.3
F.Allcapacitorsare16Vandshouldbeplacedasclose
as possible to the LTC1543 to reduce EMI. The turn-on
time for the charge pump is 60ms.
28
27
26
25
1545 F21
3
2
1
4
C3
1
F
C4
1
F
5V
C1
1
F
C2
1
F
C5
3.3
F
LTC1543
VDD
C1+
C1
VCC
C2+
C2
VEE
GND
+
Figure 21. Charge Pump
Receiver Fail-Safe
All LTC1543/LTC1545 receivers feature fail-safe opera-
tion in all modes. If the receiver inputs are left floating or
shorted together by a termination resistor, the receiver
output will always be forced to a logic high.
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