HA4404 Intersil Corporation, HA4404 Datasheet - Page 4

• Manufacturer Part Number: HA4404
• Description: 330MHz/ 4 x 1 Video Crosspoint Switch with Tally Outputs
• Manufacturer: Intersil Corporation

Application Information
General
The HA4404B is a 4 x 1 crosspoint switch that is ideal for the
matrix element of high performance switchers and routers.
This crosspoint’s low input capacitance and high input resis-
tance provide excellent video terminations when used with
an external 75
inputs are connected together, the use of an input buffer
should be considered (see Figure 1). This crosspoint con-
tains no feedback or gain setting resistors, so the output is a
true high impedance load when the IC is disabled (CS = 1).
Ground Connections
All GND pins are connected to a common point on the die,
so any one of them will suffice as the functional GND con-
nection. For the best isolation and crosstalk rejection, how-
ever, all GND pins must connect to the GND plane.
Frequency Response
Most applications utilizing the HA4404B require a series out-
put resistor, R
capacitance, C
as C
table), so give careful consideration to component place-
ment to minimize trace length. In big matrix configurations
where C
cascading two levels of crosspoints in the case of multi-
plexed outputs (see Figure 2), or distributing the load
between two drivers if C
stage input capacitance.
Control Signals
CS - This is a TTL/CMOS compatible, active low Chip Select
input. When driven high, CS forces the output to a true high
impedance state and reduces the power dissipation by a fac-
tor of 25. The CS input has no on-chip pull-down resistor, so
it must be connected to a logic low (recommend GND) if the
enable function isn’t utilized.
A0, A1 - These are binary coded, TTL/CMOS compatible
address inputs that select which one of the four inputs con-
nect to the crosspoint output.
L
increases (as shown in the Electrical Specification
L
is large, better frequency response is obtained by
S
L
, to tune the response for the specific load
, driven. Bandwidth and slew rate degrade
resistor. Nevertheless, if several HA4404B
L
is due to bussing and subsequent
HA4404B
8
T0-T3 - The Tally outputs are open collector PNP transistors
connected to V+. When CS = 0, the PNP transistor associ-
ated with the selected input is enabled and current is deliv-
ered to the load. When the crosspoint is disabled, or the
channel is unselected, the Tally output(s) present a very high
impedance to the external circuitry. Several Tally outputs
may be wire OR’d together to generate complex control sig-
nals, as shown in the application circuits below. The Tally
load may be terminated to GND or to V- as long as the con-
tinuous output current doesn’t exceed 3mA (6mA at 50%
duty cycle, etc.).
Switcher/Router Applications
Figure 1 illustrates one possible implementation of a wide-
band, low power, 4 x 4 switcher/router utilizing the HA4404B
for the switch matrix. A 4 x 4 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 out-
put, or an input may connect to multiple outputs). This appli-
cation utilizes the HA4600 (video buffer with output disable)
for the input buffer, the HA4404B as the switch matrix, and
the HFA1112 (programmable gain buffer) as the gain of two
output driver. Figure 2 details a 16 x 1 switcher (basically a
16:1 mux) which uses the HA4201 (1 x 1 crosspoint) and the
HA4404B in a cascaded stage configuration to minimize
capacitive loading at each output node, thus increasing sys-
tem bandwidth.
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.
Intersil’s Crosspoint Family
Intersil offers a variety of 4 x 1 and 1 x 1 crosspoint switches.
In addition to the HA4404B, the 4 x 1 family includes the
HA4314 and HA4344. The HA4314 is a basic 14 lead device
without Tally outputs. The HA4344 is a 16 lead crosspoint
with synchronized control lines (A0, A1, CS). With synchroni-
zation, the control information for the next channel switch
can be loaded into the crosspoint without affecting the cur-
rent state. On a subsequent clock edge the stored control
state effects the desired channel switch.
The 1 x 1 family is comprised of the HA4201 and HA4600.
They are essentially similar devices, but the HA4201
includes a Tally output. The 1 x 1s are useful as high perfor-
mance video input buffers, or in a switch matrix requiring
very high off isolation.