EEPROM

Xin

Xout

VDD

GND

VDDOUT

Xtal

Y2 = 27 MHz

Y1 = 27 MHz

Y3 = 27 MHz

LV

CMOS

Y4 = 27 MHz

Y5 = 27 MHz

LV

CMOS

Pdiv5 = 1

Pdiv4 = 1

LV

CMOS

LV

CMOS

Pdiv3 = 1

Pdiv2 = 1

LV

CMOS

Programming

and

Register

InputClock

PLL Bypass

PLL 1

PowerDown

PLL Bypass

PLL 2

PowerDown

S0

SDA

SCL

27-MHz

Crystal

ProgrammingBus

“1” = OutputsEnabled

“0” = Outputs 3-State

CDCE925

CDCEL925

www.ti.com

SCAS847F – JULY 2007 – REVISED MARCH 2010

SDA/S1 and SCL/S2 pins of the CDCE925/CDCEL925 are dual-function pins. In default configuration, they are

predefined as SDA/SCL serial programming interface. They can be programmed to control pins (S1/S2) by

setting the relevant bits in the EEPROM. Note that the changes of the bits in the Control Register (bit [6] of byte

02h) have no effect until they are written into the EEPROM.

forced to GND, the two control pins, S1 and S2, temporally act as serial programming pins (SDA/SCL).

S0 is not a multi use pin; it is a control pin only.

DEFAULT DEVICE SETTING

The internal EEPROM of CDCE925/CDCEL925 is preconfigured as shown in Figure 6 The input frequency is

passed through the output as a default. This allows the device to operate in default mode without the extra

production step of programming it. The default setting appears after power is supplied or after power-down/up

sequence until it is reprogrammed by the user to a different application configuration. A new register setting is

programmed via the serial SDA/SCL interface.

Figure 6. Preconfiguration of CDCE925/CDCEL925 Internal EEPROM

Table 4 shows the factory default setting for the Control Terminal Register (external control pins). Note that even

though eight different register settings are possible, in default configuration, only the first two settings (0 and 1)

can be selected with S0, as S1 and S2 are configured as programming pins in default mode.

Y1

PLL1 Settings

PLL2 Settings

Output

Frequency

SSC

Output

Frequency

SSC

Output

External Control Pins

Selection

Selection

Selection

Selection

Selection

Selection

Selection

S2

S1

S0

Y1

FS1

SSC1

Y2Y3

FS2

SSC2

Y4Y5

SCL (I2C)

SDA (I2C)

0

3-state

off

3-state

off

3-state

SCL (I2C)

SDA (I2C)

1

enabled

off

enabled

off

enabled

(1)

In default mode or when programmed respectively, S1 and S2 act as serial programming interface, SDA/SCL. They do not have any

control-pin function but they are internally interpreted as if S1=0 and S2=0. S0, however, is a control-pin which in the default mode

switches all outputs ON or OFF (as previously predefined).

Copyright © 2007–2010, Texas Instruments Incorporated

Submit Documentation Feedback

11

Product Folder Link(s): CDCE925 CDCEL925