LTC2873H Просмотр технического описания (PDF) - Analog Devices
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LTC2873H Datasheet PDF : 32 Pages
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LTC2873
TEST CIRCUITS
A/DO
VL
OR
DI
DRIVER
GND
B/RI
DE485/F232
OR SHDN
RL GND
OR
VCC
CL
RL
VCC
OR
GND
CL
DE485/F232 ½VL
OR SHDN
A/DO OR B/RI
tZLD485,
tZLSD485
½VCC
B/RI OR A/DO
tZHD485,
tZHSD485
½VCC
VL
½VL
0V
tLZD485,
tLZSD485
VCC
0.5V
VOL
0.5V
VOH
0V
tHZD485,
tHZSD485
2873 F05
Figure 5. RS485 Driver Enable and Disable Timing Measurements
±VAB/2 A/DO
A/DO TO B/RI 0V
VCM
RO
RECEIVER
B/RI
CL
±VAB/2
tPLHR485
90%
RO
10%
½VL
tRR485
VAB
tPHLR485
90%
½VL
10%
tFR485
–VAB
VL
0V
tSKEWR485 = tPLHR485 – tPHLR485
2873 F06
Figure 6. RS485 Receiver Propagation Delay Measurements
A/DO
0V TO 3V
B/RI
3V TO 0V
RECEIVER
RO
RL
VL
OR
GND
CL
RE485
OR SHDN
RE485
OR SHDN
½VL
tZLR485,
tZLRSR485
RO
½VL
RO
½VL
tZHR485,
tZHRSR485
VL
½VL
0V
tLZR485,
tLZSR485
VL
0.5V
VOL
0.5V
VOH
0V
tHZR485,
tHZSR485
2873 F07
Figure 7. RS485 Receiver Enable and Disable Timing Measurements
IA
RTERM =
VAB
IA
RECEIVER A/DO +– VAB
TE485
B/RI
+– VB
TE485 ½VL
IA
½VL
tRTEN485
90%
Figure 8. RS485 Termination Resistance and Timing Measurements
VL
0V
tRTZ485
10%
2873 F08
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