8

SY10E196

SY100E196

Micrel, Inc.

M9999-032006

hbwhelp@micrel.com or (408) 955-1690

Typically, the analog input will be driven by an external

DAC to provide a digital control with very fine analog

output steps. The final resolution of the device will be

dependent on the width of the DAC chosen.

To determine the voltage range necessary for the

FTUNE input, the graphs provided should be used. As

an example, if a range of 40ps is selected to cover worst

case conditions and ensure coverage of the digital range,

from the 100E196 graph a voltage range of –3.25V to

–4V would be necessary on the FTUNE pin. Obviously,

there are numerous voltage ranges which can be used

to cover a given delay range.

Users are given the

flexibility to determine which one best fits their design.

Figure 1. Cascading Interconnect Architecture

Cascading Multiple E196s

To increase the programmable range of the E196,

internal cascade circuitry has been included. This circuitry

allows for the cascading of multiple E196s without the

need for any external gating. Furthermore, this capability

requires only one more address line per added E196.

Obviously, cascading multiple PDCs will result in a larger

programmable range; however, this increase is at the

expense of a longer minimum delay.

Figure 1 illustrates the interconnect scheme for

cascading two E196s. As can be seen, this scheme can

of the E196 is the cascade control pin.

With the

signals the need for a larger programmable range than

is achievable with a single device.

An expansion of the latch section of the block diagram

is pictured below. Use of this diagram will simplify the

explanation of how the cascade circuitry works. When

be low, while the cascade bar output will be a logical

high. In this condition, the SET MIN pin of chip #2 will

be asserted and, thus, all of the latches of chip #2 will

be reset and the device will be set at its minimum delay.

Since the RESET and SET inputs of the latches are

not affect the operation of chip #2.

Chip #1, on the other hand, will have both SET MIN

and SET MAX de-asserted so that its delay will be

needed is greater than can be achieved with 31.75 gate

Using the FTUNE Analog Input

The analog FTUNE pin on the E196 device is intended

to enhance the 20ps resolution capabilities of the fully

digital E195.

The level of resolution obtained is

dependent on the number of increments applied to the

appropriate range on the FTUNE pin.

To provide another level of resolution, the FTUNE pin

must be capable of adjusting the delay by greater than

the 20ps digital resolution.

As shown in the provided

graphs, this requirement is easily achieved since a 100ps

delay can be achieved over the entire FTUNE voltage

range.This extra analog range ensures that the FTUNE

pin will be capable, even under worst case conditions, of

covering the digital resolution.

E196

Chip #1

LEN

VEE

IN

VBB

IN

VCC

VCCO

Q

VCCO

Q

E196

Chip #2

LEN

VEE

IN

VBB

IN

VCC

VCCO

Q

VCCO

Q

ADDRESS BUS (A0 – A6)

Input

Output

LINEAR

INPUT

FTUNE

FTUNE