XRP7708 Datasheet, PDF (21/27 Pages) Exar Corporation – Quad Channel Digital PWM Step Down Controller

XRP7708
Quad Channel Digital PWM Step Down Controller
When powering in sync mode the slave unit will initially power up with its internal clock to transfer
the configuration memory. Once this transfer occurs, then the unit is set to function as a slave unit.
In turn the unit will take the external clock provided by the master to run as its main internal clock.
GPIO1 ^CLK_OUT
GPIO2 ^SYNC_OUT
XRP7708
configured
as a master
CLK_IN
GPIO1
SYNC_IN _GPIO2
XRP7708
configured
as a slave
Fig. 23: Master/Slave Configuration of the XRP7708
External Clock Synchronization Master Slave combination
When an external clock is used, the user will need to setup the master to also have an external
clock in function. All of the same rules apply as in the External clock synchronization, Synchronized
operation as a Slave unit section of this document. There are two ways of synchronizing this,
either the external clock going to both Master/Slave CLK_IN, or CLK_IN can go to the Master, and
the Master can synchronize SYNC_OUT and CLK_OUT to the Slave.
CLK_IN
GPIO1
GPIO2 ^SYNC_OUT
XRP7708
Configured as a
master with
external clock sync
CLK_IN
GPIO1
SYNC_IN
GPIO2
XRP7708
configured
as slave
Fig. 24: External Clock Synchronization Master Slave Combination
CLK_IN
CLK_OUT
GPIO3 GPIO1
GPIO2 ^SYNC_OUT
XRP7708
Configured as a
master with
external clock sync
CLK_IN
GPIO1
SYNC_IN
GPIO2
XRP7708
configured
as slave
Fig. 25:Alternative External clock synchronization Master Slave combination
© 2010 Exar Corporation
21/27
Rev. 1.0.3