HA4201
matrix, and the HFA1112 (programmable gain buffer) as the
Control Signals
gain of two output driver. Figure 2 details a 16x1 switcher
(basically a 16:1 mux) which uses the HA4201 in a cascaded
stage configuration to minimize capacitive loading at each
output node, thus increasing system bandwidth.
EN - The ENABLE input is a TTL/CMOS compatible, active
high input. When driven low this input forces the output to a
true high impedance state and reduces the power
dissipation by two orders of magnitude. The EN input has no
on-chip pull-up resistor, so it must be connected to a logic
high (recommend V+) if the enable function isn’t utilized.
Power Up Considerations
No signals should be applied to the analog or digital inputs
before the power supplies are activated. Latch-up may occur
if the inputs are driven at the time of power up. To prevent
latch-up, the input currents during power up must not exceed
the values listed in the Absolute Maximum Ratings.
Tally - The Tally output is an open collector PNP transistor
connected to V+. When EN = 1, the PNP transistor is enabled
and current is delivered to the load. When the crosspoint is
disabled, the Tally output presents a very high impedance to the
external circuitry. Several Tally outputs may be wire OR’d
together to generate complex control signals, as shown with the
HA4404 in the application circuits below. The Tally load may be
terminated to GND or to V- as long as the continuous output
current doesn’t exceed 3mA (6mA at 50% duty cycle, etc.).
Intersil’s Crosspoint Family
Intersil offers a variety of 1x1 and 4x1 crosspoint switches. In
addition to the HA4201, the 1x1 family includes the HA4600
which is an essentially similar device but without the Tally
output. The 4x1 family is comprised of the HA4314, HA4404,
and HA4344. The HA4314 is a 14 lead basic 4x1 crosspoint.
The HA4404 is a 16 Ld device with Tally outputs to indicate
the selected channel. The HA4344 is a 16 Ld crosspoint with
synchronized control lines (A0, A1, CS). With
synchronization, the control information for the next channel
switch can be loaded into the crosspoint without affecting the
current state. On a subsequent clock edge the stored control
state effects the desired channel switch.
Switcher/Router Applications
Figure 1 illustrates one possible implementation of a
wideband, low-power, 4x4 switcher/router. A 4x4
switcher/router allows any of the four outputs to be driven by
any one of the four inputs (e.g. each of the four inputs may
connect to a different output, or an input may connect to
multiple outputs). This application utilizes the HA4201 for the
input buffer, the HA4404 (4x1 crosspoint switch) as the switch
INPUT BUFFERS
EN
SWITCH MATRIX
10kΩ
SOURCE0
OUT
R
S
75Ω
IN0
T0
IN0
T0
IN0
T0
IN0
T0
HA4201
CS
CS
CS
CS
SOURCE1
75Ω
HA4404
HA4404
HA4404
HA4404
OUT
OUT
OUT
OUT
SOURCE2
75Ω
R
R
R
R
S
S
S
S
IN3
T3
IN3
T3
IN3
T3
IN3
T3
EN
OUT
SOURCE3
75Ω
10kΩ
R
S
+
+
+
+
-
-
-
-
HA4201
OUTPUT BUFFERS
(HFA1112 OR HFA1115)
X2
X2
X2
X2
75Ω
75Ω
75Ω
75Ω
OUT2
OUT0
OUT1
OUT3
FIGURE 1. 4x4 SWITCHER/ROUTER APPLICATION
FN3680.6
March 8, 2007
4
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