The TMCS1127 only requires a power supply (V_S) on the low-voltage isolated side, which powers the analog circuitry independent of the isolated current input. V_S determines the full-scale output range of the analog output V_OUT, and can be supplied with any voltage between 3V and 5.5V. To filter noise in the power-supply path, place a low-ESR decoupling capacitor of 0.1µF between V_S and GND pins as close as possible to the supply and ground pins of the device. More decoupling capacitance can be added to compensate for noisy or high-impedance power supplies. When used in extremely noisy environments, ferrite beads can be added close to the supply pin as shown in Figure 9-4 to target and suppress high-frequency noise coupled on to system supply.

Figure 9-4 Power Supply Noise Filtering

The TMCS1127 power supply V_S can be sequenced independently of current flowing through the input. However, there is a power-on delay between V_S reaching the recommended operating voltage and the analog output validation. During this power-on time, the output voltage V_OUT can transition between GND and V_S as the output transfers from a high impedance reset state to the active drive state. If this behavior must be avoided, then provide a stable supply voltage V_S for longer than the power-on time prior to applying input current.