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 2000 Semtech Corp.

www.semtech.com

EDGE HIGH-PERFORMANCE PRODUCTS

Edge693

Circuit Description

Introduction

The driver circuit will force the DOUT output to one of

three states:

1.

DVH (driver high voltage level)

2.

DVL (driver low voltage level)

3.

High Impedance (Hi Z).

Both driver digital control inputs (DHI/DHI*, DRVEN/

DRVEN*) are wide-voltage differential inputs capable of

receiving ECL, TTL, and CMOS signals. Single-ended

operation is achievable by generating the proper

threshold levels for the inverting inputs.

Drive Enable

The drive enable (DRVEN/DRVEN*) inputs control

whether the driver is forcing a voltage or is placed in a

high-impedance state. If DRVEN is more positive than

DRVEN*, the output will force either DVL or DVH,

depending on the driver data inputs. When DRVEN is

more negative than DRVEN*, the output is set to high-

impedance, independent of the driver data inputs.

Driver Data

The driver data inputs (DHI/DHI*) determine whether

the driver output is high or low. If DHI is more positive

than DHI*, the output will force DVH when the driver is

enabled. If DHI is more negative than DHI*, the output

will force DVL when the driver is enabled.

Table 1 summarizes the functionality of the driver enable

and driver data pins.

Table 1. DRVEN and DHI Pin Functionality

Driver Levels

DVH and DVL are high-input impedance voltage controlled

inputs that establish the driver logical high and low levels

respectively.

Slew Rate Adjustment

The driver rising and falling slew rates are adjustable

from 3.0 V/ns to 1 V/ns. The SLEWADJ signals are

current controlled inputs that vary the rising and falling

edge slew rates. An input current of 2.0 mA translates

to a slew rate of 3.0 V/ns. An input current of 0.8 mA

forces a 1 V/ns edge (see Figure 1).

Figure 1. Slew Rate Control

Notice that the driver A slew rate and driver B slew rate

are independent. However, the rising and falling edge

slew rates on each driver track each other and are not

independent (see Figure 2).

Figure 2. Output Slew Rate Adjustability

*

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2.0

SLEWADJ (mA)

(BIAS = 1.5 mA)

a

b

a. SLEWADJ = 2.0 mA, Rising SR = Falling SR = 2.5V/ns.

b. SLEWADJ = 0.8 mA, Rising SR = Falling SR = 1.0V/ns.