Power integrations InnoSwitch3 Application Note page 13

AN-72
Step 6 – Secondary Components
Enter: RFB_UPPER
SECONDARY COMPONENTS
118
119 RFB_UPPER
120 RFB_LOWER
121 CFB_LOWER
Figure 9. Secondary Components Section of InnoSwitch3 PIXLs Spreadsheet.
125 MULTIPLE OUTPUT PARAMETERS
126 OUTPUT 1
127 VOUT1
128 IOUT1
129 POUT1
130 IRMS_SECONDARY1
131 IRIPPLE_CAP_OUTPUT1
132 AWG_SECONDARY1
133 OD_SECONDARY1_INSULATED
134 OD_SECONDARY1_BARE
135 CM_SECONDARY1
136 NSECONDARY1
137 VREVERSE_RECTIFIER1
138 SRFET1
139 VF_SRFET1
140 VBREAKDOWN_SRFET1
141 RDSON_SRFET1
Figure 10. Secondary Components Section of InnoSwitch3 PIXls Spreadsheet.
Upper Feedback Resistor, RFB_UPPER
The RFB_UPPER resistor value is calculated based on VOUT and the
nominal internal reference voltage of the IC (1.265 V).
Upper Feedback Resistor, RFB_LOWER
The RFB_LOWER resistor is calculated based on VOUT and the 1.265 V
internal reference voltage. The value will change if the specified
value is used for the RFB_UPPER resistor.
Lower Feedback Resistor Decoupling Capacitor, CFB_LOWER
A 330 pF surface mount ceramic X7R type capacitor (or better) is
recommended as this can be placed close to the pins of the FEEDBACK
and GROUND pins of the IC.
Step 7 – Multiple Output Parameters
This section allows the user to design up to three secondary outputs
(excluding bias supply) and choose a suitable MOSFET size for
synchronous rectification. The spreadsheet will provide a warning
should the total power of the multiple outputs exceed the power
described in the POUT cell.
For single output design, cells VOUT1, IOUT1 and POUT1 will be
the main output parameters entered in section 1.
www.power.com
Auto
Upper feedback resistor (connected to the first
100.00 kΩ output voltage)
34.00 kΩ Lower feedback resistor
330 pF Lower feedback resistor decoupling capacitor
5.00 V Output 1 voltage
4.00 A Output 1 current
20.00 W Output 1 power
Root mean squared value of the secondary
5.95 A current for output 1
Current ripple on the secondary waveform for
4.41 A output 1
19 AWG Wire size for output 1
Secondary winding wire outer diameter with
1.217 mm insulation for output 1
Secondary winding wire outer diameter without
0.912 mm insulation for output 1
Bare conductor effective area in circular mils for
1191 Cmils output 1
6 Number of turns for output 1
SRFET reverse voltage (not accounting parasitic
34.09 V voltage ring) for output 1
AON6266 SRFET selection for output 1
0.076 V SRFET on-time drain voltage for output 1
60 V SRFET breakdown voltage for output 1
SRFET on-time drain resistance at 25degC and
19.0 mΩ VGS=4.4V for output 1
Each output provides a selection of synchronous rectifier MOSFETs
(SRFET) in the drop down menu, (see Table 10). Based on the SR
FET chosen the on-state forward voltage, VF_SRFET (V), breakdown
voltage, VBREAKDOWN_SRFET (V), and on-time drain resistance,
RDSON_SRFET (mΩ) will be displayed in the spreadsheet.
The spreadsheet also calculates the critical electrical parameters for
each secondary output:
RMS Current of the Secondary Output, RMS_SECONDARY (A)
– Used to size the secondary winding wire.
Current Ripple on Secondary, IRIPPLE_CAP_OUTPUT (A)
– Used to size the output filter capacitor.
–Number of Turns for Output, NSECONDARY
– Calculated turns for each output.
Additional information for the magnetic wire are also given, AWG_
SECONDARY (AWG), OD_SECONDARY_INSULATED (mm) and
OD_SECONDARY_BARE (mm).
Application Note
13
Rev. A 10/18