Data Sheet

ADRF5721

Rev. 0 | Page 13 of 17

PARALLEL MODE INTERFACE

The ADRF5721 has four digital control inputs, D2 (LSB) to D5

(MSB), to select the desired attenuation state in parallel mode, as

shown in Table 7. The parallel control interface is activated when

PS is set to low.

There are two modes of parallel operation: direct parallel and

latched parallel.

Direct Parallel Mode

To enable direct parallel mode, keep the LE pin high. To change

the attenuation state, use the control voltage inputs (D2 to D5)

directly. This mode is ideal for manual control of the attenuator.

Latched Parallel Mode

To enable latched parallel mode, keep the LE pin low when

changing the control voltage inputs (D2 to D5) to set the

attenuation state. When the desired state is set, toggle LE high

to transfer the 4-bit data to the bypass switches of the attenuator

array, and then toggle LE low to latch the change into the device

until the next desired attenuation change (see Figure 26 in

conjunction with Table 2).

Figure 26. Latched Parallel Mode Timing Diagram

D5 TO D2

PS

LE

X

X

X