BVA304 Datasheet, PDF (4/22 Pages) BeRex Corporation – 50-4000 MHz DIGITAL VARIABLE GAIN AMPLIFIER

BVA304
50-4000 MHz DIGITAL VARIABLE GAIN AMPLIFIER
Programming Options
Parallel/Serial Selection
Either a parallel or serial interface can be used to
control the BVA304. The P/S bit provides this
selection, with P/S = LOW selecting the parallel
interface and P/S = HIGH selecting the serial
interface.
Parallel Mode Interface
The parallel interface consists of six CMOS compatible
control lines that select the desired
attenuation state, as shown in Table 4.
The parallel interface timing requirements are
defined by Figure 4 (Parallel Interface Timing
Diagram), Table 7 (Parallel Interface AC
Characteristics), and switching speed (Table 1).
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 3) to latch the new attenuation state into
the device.
For direct parallel 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).
Table 4. Truth Table
P/S C16 C8 C4 C2 C1 C0.5 Attenuation state
Clock, and Latch Enable (LE). The Data and Clock
inputs allow data to be serially entered into the shift
register, a process that is independent of the state of
the LE input.
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 timing for this operation is defined by
Figure 3 (Serial Interface Timing Diagram) and
Table 6 (Serial Interface AC Characteristics).
Power-up Control Settings
The BVA304 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.
When the attenuator powers up in Serial mode
(P/S = 1), the six control bits are set to whatever
data is present on the six parallel data inputs (C0.5
to C16). This allows any one of the 64 attenuation
settings to be specified as the power-up state.
0 0 0 0 0 0 0 Reference Loss When the attenuator powers up in Parallel mode
0000001
0000010
0.5 dB
1 dB
(P/S = 0) with LE = 0, the control bits are
automatically set to one of four possible values.
These four values are selected by the two power-up
0000100
0001000
2 dB
control bits, PUP1 and PUP2, as shown in Table 5
(Power-Up Truth Table, Parallel Mode).
4 dB
0010000
8 dB
Table 5. Parallel PUP Truth Table
0100000
0111111
Note: Not all 64 possible combinations of C0.5-C16 are shown in table
16 dB
31.5 dB
Serial Interface
The serial interface is a 6-bit serial-in, parallel-out
shift register buffered by a transparent latch. It is
controlled by three CMOS-compatible signals: Data,
P/S
LE PUP2 PUP1
Attenuation state
0
0
0
0
Reference Loss
0
0
1
0
8 dB
0
0
0
1
16 dB
0
0
1
1
31.5 dB
0
1
X
X
Defined by C0.5-C16
Note: Power up with LE = 1 provides normal parallel operation with C0.5-C16, and PUP1 and PUP2
are not active
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