PE4305
Product Specification
Programming Options
serially entered into the shift register, a process that
is independent of the state of the LE input.
Parallel/Serial Selection
Either a parallel or serial interface can be used to
control the PE4305. The P/S bit provides this
selection, with P/S=LOW selecting the parallel
interface and P/S=HIGH selecting the serial
interface.
The LE input controls the latch. When LE is HIGH,
the latch is transparent and the contents of the serial
shift register control the attenuator. When LE is
brought LOW, data in the shift register is latched.
The shift register should 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. The start bit (B5) of the data should
always be low to prevent an unknown state in the
device. The timing for this operation is defined by
Figure 17 (Serial Interface Timing Diagram) and
Table 8 (Serial Interface AC Characteristics).
Parallel / Direct Mode Interface
The parallel interface consists of five CMOS-
compatible control lines that select the desired
attenuation state, as shown in Table 5.
The parallel interface timing requirements are
defined by Figure 18 (Parallel Interface Timing
Diagram), Table 9 (Parallel Interface AC
Characteristics), and switching speed (Table 1).
Power-up Control Settings
For parallel programming the Latch Enable (LE)
should be held LOW while changing attenuation
state control values, then pulse LE HIGH to LOW
(per Figure 18) to latch new attenuation state into
device.
The PE4305 always assumes a specifiable
attenuation setting on power-up. This feature exists
for both the Serial and Parallel modes of operation,
and allows a known attenuation state to be
established before an initial serial or parallel control
word is provided.
For direct programming, the Latch Enable (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).
When the attenuator powers up in Serial mode (P/
S=1), the five control bits are set to whatever data is
present on the five parallel data inputs (C0.5 to C8).
This allows any one of the 32 attenuation settings to
be specified as the power-up state.
Table 5. Truth Table
When the attenuator powers up in Parallel mode (P/
S=0) with LE=0, the control bits are automatically set
to one of two possible values. These two values are
selected by the power-up control bit, PUP2, as
shown in Table 6 (Power-Up Truth Table, Parallel
Mode).
Attenuation
P/S
C8
C4
C2
C1
C0.5
State
0
0
0
0
0
0
0
Reference Loss
0
0
0
0
0
1
1
0
0
0
0
1
0
1
0
0
0
1
0
0
1
0
0
1
0
0
0
1
0
1
0
0
0
0
1
0.5 dB
1 dB
2 dB
4 dB
Table 6. Power-Up Truth Table, Parallel
Interface Mode
8 dB
15.5 dB
P/S
0
LE
0
PUP2
Attenuation State
Reference Loss
8 dB
Note: Not all 32 possible combinations of C0.5-C8 are shown in table
0
1
0
0
Serial Interface
0
1
Defined by C0.5-C8
X
The PE4305’s serial interface is a 6-bit serial-in,
parallel-out shift register buffered by a transparent
latch. The latch is controlled by three CMOS-
compatible signals: Data, Clock, and Latch Enable
(LE). The Data and Clock inputs allow data to be
Note: Power up with LE=1 provides normal parallel operation with
C0.5-C8, and PUP2 is not active
©2005 Peregrine Semiconductor Corp. All rights reserved.
Document No. 70/0159~02C │ UltraCMOS™ RFIC Solutions
Page 6 of 11
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