ISL6740 Datasheet, PDF (25/29 Pages) Intersil Corporation – Flexible Double Ended Voltage and Current Mode PWM Controllers

ISL6740, 1SL6741
The gain and phase plots combined with the opto coupler’s
transfer characteristics appear in Figures 24A and 24B:
30
20
10
0
-10
10
100
1•10³
1•10⁴
1•10⁵
1•10⁶
FREQUENCY (Hz)
FIGURE 24A. EA PLUS OPTO COUPLER GAIN
90
45
0
-45
-90
-135
-180
10
100
1•10³
1•10⁴
1•10⁵
1•10⁶
FREQUENCY (Hz)
FIGURE 24B. EA PLUS OPTO COUPLER GAIN
Using the control-to-output transfer function combined with
the EA transfer function, the loop gain and phase may be
predicted. The predicted loop gain and phase margin of the
converter appear in Figures 25A and 25B:
50
40
30
20
10
0
-10
-20
-30
-40
-50
100
1•10³
1•10⁴
FREQUENCY (Hz)
FIGURE 25A. PREDICTED LOOP GAIN
1•10⁵
225
180
135
90
45
0
-45
-90
-135
100
1•10³
1•10⁴
FREQUENCY (Hz)
1•10⁵
FIGURE 25B. PREDICTED LOOP PHASE MARGIN
25
FN9111.4
July 13, 2007