THVD1510 Datasheet, PDF (22/39 Pages) Texas Instruments – 5-V RS-485 Transceivers With 18-kV IEC ESD Protection

THVD1510, THVD1512
THVD1550, THVD1551, THVD1552
SLLSEV1 – SEPTEMBER 2017
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Typical Application (continued)
In the case of surge transients, high-energy content is characterized by long pulse duration and slow decaying
pulse power. The electrical energy of a transient that is dumped into the internal protection cells of a transceiver
is converted into thermal energy, which heats and destroys the protection cells, thus destroying the transceiver.
Figure 27 shows the large differences in transient energies for single ESD, EFT, surge transients, and an EFT
pulse train that is commonly applied during compliance testing.
1000
100
Surge
10
1
EFT Pulse Train
0.1
0.01
10^-3
EFT
10^-4
ESD
10^-5
10^-6
0.5
1
2
4 6 8 10 15
Peak Pulse Voltage (kV)
Figure 27. Comparison of Transient Energies
10.2.2 Detailed Design Procedure
Figure 28 and Figure 29 suggest a protection circuit against 1 kV surge (IEC 61000-4-5) transients. Table 7
shows the associated bill of materials.
100nF
10k
R
RxD
MCU/
RE
UART
DE
DIR
D
TxD
10k
5V
100nF
V_CC
A
B
GND
R1
TVS
R2
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Figure 28. Transient Protection Against Surge Transients for Half-Duplex Devices
22
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