1. FAN7688, DEMO CONFIGURATION
STEVE MAPPUS

2. 2
FAN7688 Evaluation Board (EVB)
Electrical Specifications
Parameter MIN TYP MAX UNIT
VIN 330 400 410 VDC
VOUT 12.4 12.5 12.6 VDC
IOUT 0 20 ADC
POUT 250 W
FRES 100 kHz
FSW(PFM) 90 130 kHz

3. 3
FAN7688, LLC with SR Control, Active Demo
APEC 2015, Charlotte, NC
 Secondary Side SR Control
• 330V<VIN<410V
• VOUT=12.5V
• 0A<IOUT<20A
• POUT=250W
• ηPEAK=96.5%
• FRES=100kHz

4. 4
Back View of Demo Box
1 3 4
5 6 7 8
9 10 11 12
 1-12 are defined on
following 2 pages
2

5. 5
Back of Demo Box
Equipment Connections and Switch Controls
 1 - ”Front Panel”
• Switch to turn on the Fairchild lighted logo on the front of the demo box. Runs on 2 AA batteries located underneath/inside
demo box. Leave the Fairchild logo lit during the entire show….it looks COOL!
 2 - ”VDD-ON”
• Switch to enable VDD which effectively turns on the demo/EVB, after input voltage is applied
 3 - Connect 3 LeCroy oscilloscope standard voltage probes. No oscilloscope ground lead is necessary.
Remove the ground leads and insert the LeCroy voltage probes directly into the probe jack holes
• “SR2-G”, VGS of secondary-side SR2 MOSFET
• “SR1-G”, VGS of secondary-side SR1 MOSFET
• “LS-G”, VGS of primary-side, low-side MOSFET
 4 - ”HS-G”, Connect LeCroy ADP305 high voltage differential probe (HV insulated input)
• VGS of primary-side, high-side MOSFET
 5 - ”VOUT SENSE”, Connect Fluke 179 DVM set for displaying 12.5V out
 6 - NO CONNECT

6. 6
Back of Demo Box
Equipment Connections and Switch Controls
 7 - ”ID”, Connect LeCroy CP015, 15A current probe
• IDS of primary-side, low-side MOSFET
 8 - ”VIN SENSE”, Connect Fluke 179 DVM voltage sense for displaying DC input voltage, 300V<VIN<410V
(HV insulated input)
 9 - ”VOUT”, Connect Kikusui PLZ334W electronic load input, set to CC mode
• Demo EVB is designed for 20A but max current is limited by load to 15A max for live demo only
 10 - NO CONNECT
 11 - ”VDD”, Instek GPS-3030DD Lab DC Power Supply set for 12V bias supply input (do not go above 14V)
• For APEC we are placing this power supply underneath the table surface and running leads up to the demo VDD input
 12 - ”VIN”, Connect Lambda GEN750W, DC Power Supply (HV insulated input)
• For APEC we are placing this power supply underneath the table surface but running the remote control up to the table
surface so you can control the power supply remotely. We will also run the power supply input leads up to the demo VIN
input
• The FAN7688 EVB input power supply range is approximately 330V<VIN<412V. Since the load current is limited to 12A
for APEC, you can operate VIN down to 300V and still regulate VOUT at IOUT=12A

7. 7
Bottom View of Demo Box
Bottom Panel Shown Removed
 13 - (2), AA Batteries
• Power for 4 LEDs used to illuminate the Fairchild
logo on front of demo box. One set of AA batteries
should last entire APEC show. If it is necessary to
change the batteries, remove the bottom panel by
removing the four screws located in each corner
(see next page)
13

8. 8
Bottom View of Demo Box
Bottom Panel Shown Installed

9. 9
Power Up the Demo Box
(numbers in parenthesis refer to back of box diagram)
1. Turn on the FRONT PANEL switch (1) to illuminate the Fairchild logo
2. There are 5 LeCroy oscilloscope inputs (3, 4 and 7). Recommend to connect them all at the demo box and
choose the four that you want to connect at the oscilloscope
3. Verify VDD-ON switch (2) is OFF, in the downward position
4. Turn on DC supply to apply 390V-400V (represents typical PFC output voltage) to VIN (12)
5. Turn on VDD bias supply to apply 12V VDD (11)
6. Set electronic load (9) to CC for 0A<IOUT<12A
7. Turn on the VDD-ON switch (2) by switching it ON, to the upward position
8. Vary the electronic load from 0A to 12A
a) Show primary MOSFET burst/PWM/PFM mode, entry/exit SR SHRINK, SR enable/disable
9. Vary the high voltage DC supply from 300V to 412V
b) Show operation below/at/above resonance

10. 10
Power Down the Demo Box
(numbers in parenthesis refer to back of box diagram)
1. Turn off the FRONT PANEL switch (1) to switch off the Fairchild logo illumination
2. Turn off the DC supply to VIN (12)
3. Turn off the VDD-ON switch (2) by switching it to the downward position
4. Turn off electronic load (9) last to make sure output capacitors are fully discharged
5. Demo box is now fully powered down
a) Safe to turn off all other test equipment

11. 11
Demo Equipment Set-Up for APEC
 Top of table surface (represented by 2’x2.5’ white paper
shown in photo)
• FAN7688 Demo unit
• Oscilloscope and probes
• 2 Fluke DVMs
• Kikusui electronic load
• Lambda GEN750W DC power supply remote
control (small black box shown on top of electronic
load)
 Stored beneath table surface
• Lambda GEN750W DC power supply
• Instek GPS-3030DD Lab DC Power Supply

12. 12
Back of Complete Assembled Demo
 LeCroy voltage probes connect direct so no
ground lead is necessary
 All HV connectors are insulated
 All connecting cables are zip tied and labeled for
easy hook-up
 HV differential probe module fits nicely
underneath scope (see previous page photo)

13. 13
Technical Support
Steve Mappus
Email: steven.mappus@fairchildsemi.com
Fairchild Semiconductor
8 Commerce Drive
Bedford, NH 03110
An instructional video is available showing the set up for APEC 2015 and basic operation of
the FAN7688 EVB demo box. If viewing this document in presentation mode Click here to view
or go to:
https://drive.google.com/a/fairchildsemi.com/file/d/0B3ihdqtq4DTvUGNaeXFDNENXT1E/view

14. THANK YOU