CDCM6208_14 Datasheet, PDF (32/89 Pages) Texas Instruments – 2:8 Clock Generator, Jitter Cleaner With Fractional Dividers

CDCM6208
SCAS931F – MAY 2012 – REVISED APRIL 2014
www.ti.com
9.3.12 Device Configuration Control
Figure 35 illustrates the relationships between device states, the control pins, device initialization and
configuration, and device operational modes. In pin mode, the state of the control pins determines the
configuration of the device for all device states. In programming mode, the device registers are initialized to their
default state and the host can update the configuration by writing to the device registers.
A system may transition a device from pin mode to host connected mode by changing the state of the SI_MODE
pins and then triggering a device power cycle by toggling the PDN input pin (high-low-high); however, outputs will
be disabled during the transition as the device registers are initialized to the host mode default state.
9.3.13 Configuring the RESETN Pin
Figure 34 shows two typical applications examples of the RESETN pin and usage of the PWR pin in Pin Mode.
DVDD
DVDD
DVDD
50k
#44 (RESET)
GPO
5k
50k
#44 (RESET)
50k
#44 (PWR)
R_PD
Host
Controller
(a) (SPI/I2C Host mode)
CDCM6208
CDCM6208
(b) (SPI/I2C Host Mode)
CDCM6208
if I/O power = 1.8V: R_PD=0-Ohm
if I/O power=3.3V: R_PD=open
(c) (PIN Mode)
Figure 34. RESETN/PWR Pin Configurations
Figure 34 (a) SPI / I2C mode only: shows the RESETN pin connected to a digital device that controls device
reset. The resistor and capacitor combination ensure reset is held low even if the CDCM6208 is powered up
before the host controller output signal is valid.
Figure 34(b) SPI / I2C mode only: shows a configuration in which the user wishes to introduce a delay between
the time that the system applies power to the device and the device exiting reset. If the user does not use a
capacitor, then the device effectively ignores the state of the RESETN pin.
Figure 34 (c) Pin mode only: shows a configuration useful if the device is used in Pin Mode. Here device pin
number 44 becomes the PWR input. An external pull down resistor can be used to pull this pin down. If the
resistor is not installed, the pin is internally pulled high.
Figure 35 shows how the different possible device configurations and when the VCO becomes calibrated and the
outputs turn on and off.
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