ha4404b Intersil Corporation, ha4404b Datasheet - Page 4

• Manufacturer Part Number: ha4404b
• 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
resistance provide excellent video terminations when used
with an external 75Ω resistor. Nevertheless, if several
HA4404B inputs are connected together, the use of an input
buffer should be considered (see Figure 1). This crosspoint
contains 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
connection. For the best isolation and crosstalk rejection,
however, all GND pins must connect to the GND plane.
Frequency Response
Most applications utilizing the HA4404B require a series
output resistor, R
capacitance, C
as C
table), so give careful consideration to component
placement to minimize trace length. In big matrix
configurations where C
is obtained by cascading two levels of crosspoints in the
case of multiplexed outputs (see Figure 2), or distributing the
load between two drivers if C
subsequent 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
factor 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
connect to the crosspoint output.
T0-T3 - The Tally outputs are open collector PNP transistors
connected to V+. When CS = 0, the PNP transistor
associated with the selected input is enabled and current is
delivered 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 signals, as shown 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.).
Switcher/Router Applications
L
increases (as shown in the Electrical Specification
L
, driven. Bandwidth and slew rate degrade
S
, to tune the response for the specific load
L
is large, better frequency response
L
4
is due to bussing and
HA4404B
Figure 1 illustrates one possible implementation of a
wideband, 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 output, or an input may connect to multiple outputs).
This application 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 system 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
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.
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
performance video input buffers, or in a switch matrix
requiring very high off isolation.