SLVSD01B September 2015 – May 2019 TPS57140-EP
PRODUCTION DATA.
Figure 39 shows an equivalent model for the TPS57140-EP control loop which the designer can model in a circuit-simulation program to check frequency response and dynamic load response. The error amplifier is a transconductance amplifier with a gmEA of 97 μS. The designer can model the error amplifier using an ideal voltage-controlled current source. Resistor Ro and capacitor Co model the open-loop gain and frequency response of the amplifier. The 1-mV ac voltage source between nodes a and b effectively breaks the control loop for the frequency-response measurements. Plotting c / a shows the small-signal response of the frequency compensation. Plotting a / b shows the small-signal response of the overall loop. The designer can check the dynamic loop response in a time-domain analysis by replacing RL with a current source having the appropriate load-step amplitude and step rate. This equivalent model is only valid for CCM designs.