PE43711
UltraCMOS® RF Digital Step Attenuator
Page 8 DOC-44414-2 – (3/2015)
www.psemi.com
Programming Options
Parallel/Serial Selection
Either a Parallel or Serial interface can be used to
control the PE43711. The P/S bit provides this
selection, with P/S = LOW selecting the Parallel
interface and P/S = HIG H select ing the S erial
interface.
Parallel Mode Interface
The Parallel interface consists of seven CMOS-
compatible control lines th at select the de s ir ed attenu-
ation state, as shown in Table 4.
The Parallel interface timing requirement s are defined
by Figure 4 (Parallel Interface Timing Diagram),
Table 8 (Parallel and Direct Interface AC Character-
istics) and switching time (Table 3).
For Latched Parallel programming, the Latch Enable
(LE) should be held LOW while changing attenuation
state control values then pulse LE HIGH to LOW (per
Figure 4) to latch new attenuation state into the
device.
For Direct Parallel programming, the LE line should
be pulled HIGH. Changing attenuation state control
values will change device state to new attenuation.
Direct mode is ideal for manual control of the device
(using hardwire, switches or jumpers).
Serial Interface
The Serial interface is an 8-bit Serial-In, Parallel-Out
shift register buffered by a transparent latch. The 8-
bits make up the Attenuation Word that controls the
DSA. Figure 3 illustrates an example timing diagram
for programming a state.
The Serial interface is controlled using three CMOS-
compatible signals: SI, Clock (CLK) and LE. The SI
and CLK inputs allow data to be serially entered into
the shift register. Serial data is clocked in LSB first.
The shift register must be loaded while LE is held
LOW to prevent the attenuator value from changing
as data is entered. The LE input should then be
toggled HIGH and brought LOW again, latching the
new data into the DSA. The Attenuation Word truth
table is listed in Table 5. A programming example of
the serial register is illustrated in Figure 2. The Serial
timing diagram is illustrated in Figure 3. It is required
that all Parallel control inputs be grounded when the
DSA is used in Serial mode.
Power-up Control Settings
The PE43711 will always initialize to the maximum
attenuation setting (31.75 dB) on power-up for both
the Serial and Latched Parallel modes of operation
and will remain in this setting until the user latches in
the next programming word. In Direct Parallel mode,
the DSA can be preset to any state within the
31.75 dB range by pre-setting the Para llel control pins
prior to power-up. In this mode, there is a 400 µs
delay between the time the DSA is powered-up to the
time the desired state is set. During this power-up
delay, the device attenuates to the maximum attenu-
ation setting (31.75 dB) before defaulting to the user
defined state. If the control pins are left floating in this
mode during power-up, the device will default to the
minimum attenuation setting (insertion loss state).
Dynamic operation between Serial and Parallel
programming modes is possible.
If the DSA powers up in Serial mode (P/S= HIGH), all
the Parallel control inputs DI[6:0] must be set to logic
LOW. Prior to toggling to Paralle l mode, the DSA must
be programmed serially to ensure D[7] is set to logic
LOW.
If the DSA powers up in either Latched or Direct
Parallel mode, all Parallel pins DI[6:0] must be set to
logic LOW prior to toggling to Serial mode
(P/S= HIGH), and held LOW until the DSA has been
programmed serially to ensure bit D[7] is set to logic
LOW.
The sequencing is only required once on power-up.
Once completed, the DSA may be toggled between
Serial and Parallel programming modes at will.