Instruction Manual

Hot-Plug of SCART Connectors—Floating
Chassis Discharge
The MAX4399 features high-ESD protection on all
SCART inputs and outputs, and requires no external
transient voltage suppressor (TVS) devices to protect
against floating chassis discharge. Some set-top boxes
have a floating chassis problem in which the chassis is
not connected to earth ground. As a result, the chassis
can charge up to 500V. When a SCART cable is con-
nected to the SCART connector, the charged chassis
can discharge through a signal pin. The equivalent cir-
cuit is a 2200pF capacitor charged to 311V connected
through less than 0.1Ω to a signal pin. The MAX4399 is
soldered on the PC board when it experiences such a
discharge. Therefore, the current spike flows through
the ESD protection diodes and is absorbed by the sup-
ply bypass capacitors, which have high capacitance
and low ESR.
MAX4399
Audio/Video Switch for Three SCART
Connectors
______________________________________________________________________________________ 19
CLAMPLOWPASS FILTERD/A
CVBS
A = +1V/V
IN1 OUT1
0.1
µ
F
ENC_Y/CVBS_IN
CLAMPLOWPASS FILTERD/A
Y
A = +1V/V
IN2 OUT2
0.1
µ
F
ENC_Y_IN
BIASLOWPASS FILTERD/A
C
A = +1V/V
IN3 OUT3
0.1
µ
F
ENC_C_IN
CLAMPLOWPASS FILTERD/A
R
A = +1V/V
IN4 OUT4
0.1
µ
F
ENC_R/C_IN
CLAMPLOWPASS FILTERD/A
G
A = +1V/V
IN5 OUT5
0.1
µ
F
ENC_G_IN
CLAMPLOWPASS FILTERD/A
B
A = +1V/V
IN6 OUT6
0.1
µ
F
ENC_B_IN
MPEG DECODER
MAX7440
MAX4399
G_VID
+5V
V_VID
+5V
0.1
µ
F1
µ
F
Figure 9. MPEG Decoder Outputs Filtered by the MAX7440 Before Being Passed to the MAX4399