STV9556

13/24

Figure 16. Arcing protection network (one channel)

10.3

Arcing protection: layout and decoupling

Several layout precautions have to be considered to get the optimum arcing protection:

Sparkgap grounding: when an arc occurs, the energy must flow through the CRT ground without

reaching the amplifier. This is obtained by connecting the sparkgap grounding (point B) to the CRT

ground (socket) via a wide/short trace. Conversely the point B must be connected to the amplifier

ground via a longer/narrower trace.

Grounding separation: In order to set apart the amplifer ground and CRT ground, the R29/C29 net-

Amplifier grounding: The 3 grounds GNDS, GNDA and GNDP must be connected together as

close as possible to the device.

R11

R29(***)

110

Ω/0.5W

C18

100nF

C24

4.7

µF/150V

C12(*)

100nF/250V

R19(**)

R10

110

Ω/0.5W

L1

0.33

µH

D12

FDH400

F1

STV9556

OUT

Spark gap

(**): R19 must be mandatorily used

(***): Ground separation network

33-40

Ω

200V

C29(***)

0.22

µF

1-10

Ω

CRT

GNDP

GNDS

GNDA

D13

FDH400

A

B