The HA4314B is a very wide bandwidth 4x1 crosspoint switch ideal for professional video switching, HDTV, computer monitor routing and other high performance applications. The circuit features extremely low power consumption (105MW enabled, 4mW disabled), excellent differential gain and phase, and very high off isolation. When off, the output switches to a high impedance state, making the HA4314B ideal for routing matrix devices. The HA4314B requires no external current source and features fast switching and symmetrical slew rate.

PC Board Layout The frequency response of this circuit depends heavily on the care taken in designing the printed circuit board. The use of low inductance components such as chip resistors and chip capacitors is strongly recommended, while ground planes are required. Care should be taken to decouple the power supply. A large value (10µF) tantalum capacitor in parallel with a smaller value (0.1µF) chip capacitor will work in most situations. Keep the input and output traces as short as possible, as trace inductance and capacitance can easily become performance-limiting items.

Application Information

The HA4314B is a 4x1 matrix switch that is ideal as a matrix element for high performance switches and routers. The low input capacitance and high input resistance of this cross point provide excellent video termination when used with an external 75Ω resistor. However, if there are multiple HA4314B inputs connected together, the use of a single input buffer should be considered (see Figure 1). This crossover does not contain any feedback or gain setting resistors, so the output is a true high impedance load when the IC is off (CS=1).

ground connection

All GND pins are connected to a common point in the die, so any one of them is sufficient as a functional GND connection. For best isolation and crosstalk rejection, however, all GND pins must be connected to the GND plane.

Frequency response

Most applications utilizing the HA4314B require a series of output resistors, RS, adjusted to drive the specific load in response to a capacitor, CL. Bandwidth and slew rate degrade as CL increases, so careful component placement is considered to minimize trace lengths. In a large matrix configuration, where CL is large, better frequency response is obtained through the crossover of the two stages in the cascade. L is due to the input capacitance of Bussing and the post stage.

Control Signal 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 power dissipation by 25. The CS input factor has no pull-up or pull-down resistors, so it must be tied to a logic low (GND recommended) if The enable function is not used. A0, A1 - These are binary coded, TTL/CMOS compatible. The select address inputs are four of which input 1 is connected to the output of the crosspoint.

Switch/Router Applications

Figure 1 shows one possible implementation of a wideband, low power, 4x4 switcher/router utilizing the HA4314B's switch matrix. A 4x4 switcher/router allows any of the four outputs to be driven by any of the 4 inputs (eg, every four inputs can be connected to a different output, or an input can be connected to multiple outputs). This application uses the HA4600 (video buffer disabled) with the output as the input buffer, the HA4314B as the switch matrix, and the HFA1112 (programmable gain buffer) as the gain for the two output drivers. The 16X1 switcher (basically a 16:1 multiplexer) detailed in Figure 2 uses the HA4201 (1x1 crosspoint) and HA4314BCON group fi guration at each output in a cascaded stage Minimize capacitive load nodes, thereby increasing the bandwidth of the system.