Si5321

28

Rev. 2.3

H4

VALTIME

I*

LVTTL*

Clock Validation Time for LOS.

VALTIME sets the clock validation times for recovery

from an LOS alarm condition. When VALTIME is

high, the validation time is approximately 100 ms.

When VALTIME is low, the validation time is approx-

imately 2 ms.

H3

RSTN/CAL

I*

LVTTL*

Reset/Calibrate.

When low, all LVTTL outputs are forced into a high

impedance state, the DSPLL is forced out-of-lock,

and the device control logic is reset.

A low-to-high transition on RSTN/CAL initializes all

digital logic to a known condition and initiates self-

calibration of the DSPLL. At the completion of self-

calibration, the DSPLL begins to lock to the selected

clock input signal and begins to drive out the output

clock signal onto the CLKOUT pins.

F8

LOS

O

LVTTL

Loss-of-Signal (LOS) Alarm for CLKIN.

Active high output indicates that the Si5321 has

detected missing pulses on the input clock signal.

The LOS alarm is cleared after either 100 ms or 13 s

of a valid CLKIN clock input, depending on the set-

ting of the VALTIME input.

D8

DH_ACTV

O

LVTTL

Digital Hold Mode Active.

Active high output indicates that the DSPLL is in

digital hold mode. Digital hold mode locks the

current state of the DSPLL and forces the DSPLL to

continue generation of the output clock with no

additional phase or frequency information from the

input clock.

E8

CAL_ACTV

O

LVTTL

Calibration Mode Active.

This output is driven high during the DSPLL self-cal-

ibration and the subsequent initial lock acquisition

period.

C2

VSEL33

I*

LVTTL*

This is an enable pin for the internal regulator. To

pins.

D3–D5,

E3–E5

Supply

3.3 V Supply.

supply bypassing/decoupling for this configuration is

indicated in the typical application diagram for 3.3 V

supply operation.

Table 10. Si5321 Pin Descriptions (Continued)

Pin #

Pin Name

I/O

Signal Level

Description

*Note:

The LVTTL inputs on the Si5321 device have an internal pulldown mechanism that causes the input to default to a

logic low state if the input is not driven from an external source.