FSDH321, FSDL321
12
Figure 11. KA5-series FPS Full Range EMI scan(67KHz,
no Frequency Modulation) with DVD Player SET
Figure 12. FSDX-series FPS Full Range EMI Scan (67KHz,
with Frequency Modulation) with DVD Player SET
8. Adjusting Peak Current Limit :
As shown in Figure 13,
a combined 2.8k
Ω
internal resistance is connected to the
non-inverting lead on the PWM comparator. A external
resistance of Rx on the current limit pin forms a parallel
resistance with the 2.8k
Ω
when the internal diodes are
biased by the main current source of 900uA.
Figure 13. Peak Current Limit Adjustment
For example, FSDx321 has a typical Sense FET peak current
limit (I
LIM
) of 0.7A. I
LIM
can be adjusted to 0.5A by insert-
ing Rx between the Ipk pin and the ground. The value of the
Rx can be estimated by the following equations:
0.7A : 0.5A = 2.8k
Ω
: Xk
Ω
,
X = Rx || 2.8k
Ω
.
(X represents the resistance of the parallel network)
Frequency (MHz)
Amplitud
e (dB
µ
V)
Frequency (MHz)
A
m
plitude (dB
µ
V)
3
Vcc
Vcc
I
DELAY
I
FB
2k
Ω
Vfb
PWM
Comparator
4
Ipk
0.8k
Ω
Rx
SenseFET
Current
Sense
900uA
5uA
