QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1185
DUAL PHASE/DUAL OUTPUT SYNCHRONOUS BUCK CONVERTER
5
SYNCHRONIZATION TO AN EXTERNAL CLOCK
The LTC3850 uses a phase lock loop which forces its
internal clock to be synchronized to an external clock.
Once synchronized, the rising edge of the top FET gate is
aligned to the rising edge of the external clock. The ex-
ternal clock signal needs to be applied to the LTC3850’s
MODE pin which is tied to the turret labeled SYNC. The
internal phase lock loop is stabilized by a network on the
FREQ pin of the LTC3850. To setup the DC1185 for syn-
chronization to an external clock, follow the steps below.
1. Remove R7.
2. Stuff 10k
Ω
at R8.
3. Stuff 10nF at R10.
4. Leave 1nF at C12.
5. Float the MODE pin by placing the MODE
jumper in the BM position.
6. Apply the external clock from the turret la-
beled SYNC to GND.
