AD7401 current level to keep the output in regulation. If the error amplifiers output increases, more current is taken from the output; if it decreases, less current is taken. One function not shown in Figure 2 is the current limit. The switch current is constantly monitored and not allowed to exceed the nominal value of 1.2A. If the switch current reaches 1.2A, the SR latch is reset regardless of the state of comparator A2. This current limit protects the power switch as well as various external components connected to the AD7401.

The AD7401 is a LED driver with an audio synchronization mode that virtually eliminates the need for real time software processing for LED lighting effects. The AD7401 includes three individual PWM color LED drivers that provide up to 42mA of current drive for each PWM LED output. The AD7401 features an audio synchronization mode where the audio input signal that is mixed in from three audio inputs is filtered into three frequency bands, with each frequency band assigned to a specific PWM LED driver.

These data selectors multiplexers contain full on-chip bina- ry decoding to select one-of-eight data sources and feature a strobe-controlled TRI-STATE output The strobe must be at a low logic level to enable these devices The TRI-STATE outputs permit direct connection to a common bus When the strobe input is high both outputs are in a high-imped- ance state in which both the upper and lower transistors of each totem-pole output are off and the output neither drives nor loads the bus significantly When the strobe is low the outputs are activated and operate as standard TTL totem- pole outputs To minimize the possibility that two outputs will attempt to take a common bus to opposite logic levels the output con- trol circuitry is designed so that the average output disable time is shorter than the average output enable time