Glitch-Free Digital Step Attenuator

5

Jul 12, 2021

PARALLEL CONTROL MODE

The user has the option of running in one of two parallel modes: Direct Parallel Mode or Latched Parallel

Mode.

DIRECT PARALLEL MODE:

Direct Parallel Mode is selected when VMODE (pin 3) is < VIL and LE (pin 16) is > VIH. In this mode the

device will immediately react to any voltage changes to the parallel control pins [pins 19, 20, 21, 22, 23,

24, 1]. Use direct parallel mode for the fastest settling time.

LATCHED PARALLEL MODE:

Latched Parallel Mode is selected when VMODE (pin 3) is < VIL and LE (pin 16) is toggled from < VIL to > VIH

To utilize Latched Parallel Mode:



Set LE < VIL



Adjust pins [19, 20, 21, 22, 23, 24, 1] to the desired attenuation setting. (Note the device will not

react to these pins while LE < VIL.)



Pull LE > VIH. The device will then transition to the attenuation settings reflected by these pins.

Latched Parallel Mode implies a default state for when the device is powered up with VMODE < VIL and LE < VIL.

In this case the default setting is MAXIMUM Attenuation.

LATCHED PARALLEL MODE TIMING DIAGRAM: (Note the Timing Spec Intervals in Blue)

LATCHED PARALLEL MODE TIMING TABLE:

Interval

Symbol

Description

Min

Spec

Max

Spec

Units

A

Serial to Parallel Mode Setup Time

100

ns

B

Parallel Data Hold Time

10

ns

C

LE minimum pulse width

10

ns

D

Parallel Data Setup Time

10

ns

D[6:0]

Data Word

Latched into

Active Register

LE

VMODE

Spec

Intervals

A

D

C

B