As shown, a more reliable RS232 circuit, there is a need for enhanced industrial grade EMC RS232 chip, such SP3232EEN; a good ESD protection device PESD15VL2BT , 30KV, reverse breakdown voltage of 15V, the junction capacitance of 16pF, power 200W ; ground through the inductor is connected to the internal or beads ; serial signal line 232 on the small resistor (50-120) , to prevent the direct impact of high current chip port, the string must be noted that ESD device chips on this side, so that a large current outside It can be folded to the ESD device, freed, but not directly impact chip port.
FIG: 3232 chips case if only all the way, the way of additional input string recommended 10K resistor to ground.
Isolation chip solution
Model TD301D232H, TD501D232H
C1: 220uF / 10V (electrolytic capacitor)
TVS1: SMCJ5.0A SMCJ6.5A
C2, a C3: 1FF / 25V
Ll: 130μH
C4: 1nF / 2000V
Rl: 1 M [Omega
TVS2, TVS3: SMBJ18CA
TVS4: SMBJ30CA
R2, R3: winding resistance 10 [Omega] / 2W
GDT1: B3D090L-C