LT1781IS 查看數據表（PDF） - Linear Technology
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LT1781IS Datasheet PDF : 12 Pages
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ESD PROTECTIO
The RS232 line inputs of the LT1780/LT1781 have on-chip
protection from ESD transients up to ±15kV air gap and
±8kV contact tested to IEC-1000-4-2 test methods. The
protection structures act to divert the static discharge
safely to system ground. In order for the ESD protection to
function effectively, the power supply and ground pins of
the circuit must be connected to ground through low
impedances. The power supply decoupling capacitors and
charge pump storage capacitors provide this low imped-
ance in normal application of the circuit. The only con-
straint is that low ESR capacitors must be used for
bypassing and charge storage. ESD testing must be done
with pins VCC, VL, V+, V –, and GND shorted to ground or
connected with low ESR capacitors.
LT1780/LT1781
ESD Test Circuit
0.1µF
0.1µF
0.1µF
0.1µF
1
NC
C1+ 2
V+ 3
C1– 4
C2+ 5
C2– 6
V– 7
8
DR2 OUT
RS232
LINE PINS
PROTECTED
9
RX2 IN
TO IEC-1000-4-2
LEVEL 4
LT1780
18
ON/OFF
17 5V VCC
16 GND
0.1µF
15 DR1 OUT
14
RX1 IN
13 RX1 OUT
RS232
LINE PINS
PROTECTED
TO IEC-1000-4-2
LEVEL 4
12 DR1 IN
11 DR2 IN
10
RX2 OUT
1780 • ESD TC
TYPICAL APPLICATIO
Operation Using 5V and 12V Power Supplies
12V INPUT
2
4
5
0.1µF
6
12
LOGIC
INPUTS
11
13
LOGIC
OUTPUTS
10
18
ON/OFF
17
3
LT1780
7
15
8
14
5k
9
5k
16
5V INPUT
–12VOUT
0.1µF
RS232 OUTPUT
RS232 OUTPUT
RS232 INPUT
RS232 INPUT
1780/81 • TA03
7
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