The S4g module contains 4 current sources. These are controlled by the same 18-bit DACs (Digital to Analog Converters) as in the D5a module. These DAC outputs are then routed through Voltage to Current (V/I) converters to create 4 current outputs. As with the D5a, the output range can be set via software. The available ranges are ±50mA , ±25mA and +50mA. It has been designed to be able to deliver these currents into a 50Ω load. Whatever the current range setting, the DAC resolution remains 18-bit. This allows the user to choose the optimal range without sacrificing resolution.
Above is a block diagram of the inner workings of the module. There are 4 18-bit DACs with a shared internal reference selected for low temperature drift and low noise. The outputs of these DACs go to V/I converters containing precision resistors to minimize the temperature drift. Each current output has a voltage monitor output and a clip LED. This LED lights up if the signal reaches the load voltage compliance limit. The voltage monitor outputs the load voltage via a buffer.
|±50 , ±25 , +50