JAJS383E September 2009 – April 2018 TPS54418
PRODUCTION DATA.
Figure 31 shows an equivalent model for the TPS54418 device control loop which can be modeled in a circuit simulation program to check frequency response and dynamic load response. The error amplifier is a transconductance amplifier with a gM of 225 μA/V. The error amplifier can be modeled using an ideal voltage controlled current source. The resistor ROUT(ea) and capacitor COUT(ea) model the open loop gain and frequency response of the amplifier. The 1-mV AC voltage source between the nodes a and b effectively breaks the control loop for the frequency response measurements. Plotting a/c shows the small signal response of the frequency compensation. Plotting a/b shows the small signal response of the overall loop. The dynamic loop response can be checked by replacing the RLOAD with a current source with the appropriate load step amplitude and step rate in a time domain analysis.