Application Hints
STV8172A
8/14
STMicroelectronics Confidential
C
S
performs an integration of the parabolic signal on C
L
, therefore the amount of S correction is set
by the combination of C
L
and C
s
.
4.3
Application with Differential-output Drivers
Certain driver ICs provide the ramp signal in differential form, as two current sources i
+
and i
-
with
opposite variations.
Let us set some definitions:
●
i
cm
is the common-mode current:
●
at peak of signal, i
+
= i
cm
+ i
p
and i
-
= i
cm
- i
p
, therefore the peak differential signal is i
p
- (-
i
p
) = 2 i
p
, and the peak-peak differential signal, 4i
p
.
The application is described in
Figure 7
with DC yoke coupling. The calculations still rely on the fact
that V
1
remains equal to V
7
.
Figure 7: Using a Differential-output Driver
+Vs
R
2
R
1
Rd(*)
Yoke
Ly
-V
EE
0.
2
2
μ
F
(*)
recommended:
Ly
50
m
s
--------------
Rd
Ly
20
m
s
--------------
<
<
0.1μF
0.1μF
C
F
(47 to 100μF)
Power
Amplifier
Flyback
Generator
Thermal
Safety
+
-
470μF
470μF
Output
Current
Output
Voltage
I
p
7
3
2
5
6
1
4
R
7
+
-
Differential output
driver IC
i
p
i
cm
-i
p
i
cm
1.5
W
i
cm
1
2
--- i
+
i
-
+
(
)
=
