XRP7708 Exar Corporation, XRP7708 Datasheet - Page 21

• Manufacturer Part Number: XRP7708
• Description: Quad Channel Digital Pwm Step Down Controller
• Manufacturer: Exar Corporation

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.
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.
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.
© 2010 Exar Corporation
External Clock Synchronization Master Slave combination
CLK_IN
CLK_IN
Fig. 25:Alternative External clock synchronization Master Slave combination
Fig. 24: External Clock Synchronization Master Slave Combination
as a master
Fig. 23: Master/Slave Configuration of the XRP7708
configured
XRP7708
external clock sync
external clock sync
GPIO1
GPIO3
Configured as a
Configured as a
GPIO1
GPIO2
master with
master with
Q
Q
XRP7708
XRP7708
u
u
a
a
CLK_OUT
GPIO1
d
SYNC_OUT
d
GPIO2
GPIO2
C
C
h
h
CLK_OUT
a
a
SYNC_OUT
SYNC_OUT
21/27
n
n
n
n
e
e
l
l
SYNC_IN
CLK_IN
D
D
There are two ways of synchronizing this,
i
i
g
g
i
i
SYNC_IN
SYNC_IN
t
t
CLK_IN
CLK_IN
a
a
GPIO2
GPIO1
l
l
configured
as a slave
P
P
XRP7708
W
W
GPIO2
GPIO2
GPIO1
GPIO1
M
M
configured
configured
XRP7708
XRP7708
as slave
as slave
S
S
t
t
e
e
p
p
D
D
o
o
w
w
n
n
X
X
C
C
R
R
o
o
n
P
n
P
Rev. 1.0.3
t
t
7
7
r
r
o
7
o
7
l
l
0
0
l
l
e
e
8
8
r
r