XRP7708_12 Datasheet, PDF (22/28 Pages) Exar Corporation – Quad Channel Digital PWM Step Down Controllers

XRP7708 and XRP7740
Quad Channel Digital PWM Step Down Controllers
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. 258:Alternative External clock synchronization Master Slave combination
PHASE SHIFT
Each switching channel can be programmed to a phase shift of the multiples of 90 degrees [for a 4
phase configuration] or 120 degrees [for a 3 phase configuration]. Two or more of the channels
can use the same phase shift, however, it is preferable to run each channel at separate phases.
GPIO PINS
The General Purpose Input Output (GPIO) Pins are the basic interface between the XRP7708 and
the system. Although all of the stored data within the IC can be read back using the I²C bus it is
sometimes convenient to have some of those internal register to be displayed and or controlled by
a single data pin. Besides simple input output functions the GPIO pins can be configured to serve
as external clock inputs. These pins can be programmed using OTP bits or can be programmed
using the I²C bus. This GPIO_CONFIG register allows the user close to 100 different configuration
functions that the GPIO can be programmed to do.
NOTE: the GPIO Pins (and all I/Os) should NOT be driven without a 10K resistor when VIN is not
being applied to the IC.
© 2012 Exar Corporation
22/28
Rev. 1.2.2