Datasheet

14
LT1203/LT1205
U
S
A
O
PP
L
IC
AT
I
WU
U
I FOR ATIO
those used in the 16-to-1 crosspoint with one additional
suggestion: Surround the LT1205 output traces by ground
plane and route them away from the (–) inputs of the
other three LT1254s.
Each pair of logic inputs labeled Select Logic Output is
used to select a particular output. The truth table is used
to select the desired input and is applied to each pair of
logic inputs. For example, to route Channel 1 Input to
Output 3, the 4th pair of logic inputs labeled Select Logic
Output 3 is coded A = Low and B = High. To route
Channel 3 Input to all outputs, set all eight logic inputs
High. Channel 3 is the default input with all logic inputs
open. To shut off all channels a pair of LT1259s can be
substituted for the LT1254. The LT1259 is a dual current
feedback amplifier with a shutdown pin that reduces the
supply current to 0µA.
Response of All Four Inputs for the 4 × 4 Crosspoint
FREQUENCY (MHz)
1
GAIN (dB)
2
0
–2
–4
–6
–8
10 100
LT1203/05 • AI08
200
V
S
= ±5V
R
F
= R
G
= 820Ω
R
L
= 100Ω
LT1203/05 • AI10
CHANNEL 0 = 1V
CHANNEL 2 = 0V
4 × 4 Crosspoint, Switching Channel 0 to Channel 2
INPUT A
OF SELECT
LOGIC
OUTPUT 0
5V
0V
4 × 4 Crosspoint, All Hostile Rejection
FREQUENCY (MHz)
1
–120
HOSTILE CROSSTALK REJECTION (dB)
–100
–80
–60
–40
10 100
V
S
= ±5V
R
L
= 100Ω
R
S
= 0Ω
LT1203/05 • AI09