SLVUBB4B November 2017 – February 2023
#GUID-163394AE-B42D-41C7-ABEE-0EC78936D3FF/T5147377-45 lists general information.
Vin | Input voltage |
Vout | Output voltage |
Iout | Load current |
L | Inductance / Flyback primary inductance |
DCRL | Inductor DC resistance |
Cout,1 | Capacitance output capacitor 1 For ceramic capacitors use the capacitance at the DC bias voltage. |
ESRout,1 | Equivalent series resistance output capacitor 1 |
Cout,2 | Capacitance output capacitor 2 For ceramic capacitors use the capacitance at the DC bias voltage. |
ESRout,2 | Equivalent series resistance output capacitor 2 |
fswitch | Switching frequency |
Np ⁄ Ns | Transformer turns ratio |
Opto BW | Optocoupler bandwidth |
#GUID-163394AE-B42D-41C7-ABEE-0EC78936D3FF/T5147377-46 lists gain information.
Vramp | PWM ramp voltage |
Gm | Error amplifier transconductance |
As | Current-sense amplifier gain |
Rs | Current-sense resistance |
AOL | Error amplifier open-loop gain |
GBWP | Error amplifier gain bandwidth product |
Rp ⁄ RD | Optocoupler transfer ratio |
CTR | Current Transfer Ratio |
Vslope | Slope compensation voltage |
SLM | Slope compensation multiplier |
Current-sense gain As and current-sense resistance Rs:
For converters with integrated current-sensing circuits, sometimes there are no specific values for As and Rs in the data sheet. Instead, a value for Gm,ps (can also appear as “COMP to switch current transconductance”) is typically displayed. Equation 28 shows the relationship between these values.
In this case, values for As and Rs must be chosen to have the stated Gm,ps as a result. (For example, use the RDS(on) of the internal FET for Rs and calculate As from Equation 28.)
The input field for Vslope offers the user the option to use either Vslope or a slope compensation multiplier (SLM), in case the value for Vslope cannot be calculated by the designer (for example, because of internal slope compensation). Switching between these two variables can be done by right-clicking on the Vslope/SLM input field.
Vslope:
SLM:
#GUID-163394AE-B42D-41C7-ABEE-0EC78936D3FF/T5147377-53 lists component values.
RFBT | Top feedback resistance |
RFBB | Bottom feedback resistance |
RFF | Compensation feed-forward resistance |
RCOMP | Compensation resistance |
CFF | Compensation feed-forward capacitance |
CCOMP | Compensation capacitance |
CHF | Compensation high-frequency capacitance |
For Type II and Type II transconductance compensation networks, the Loop Calculator offers an option to use an additional Feed-Forward Capacitor in parallel with RFBT. This option can be enabled by right-clicking on the CFF input field and choosing Use.
At start-up the Loop Calculator displays only the resulting Bode plot for the Total Gain and Total Phase. The graphs for the Gain of the Power Stage, Phase of the Power Stage, Gain of the Error Amplifier, Phase of the Error Amplifier and the Error Amplifier Open Loop Gain can be switched on by selecting the respective checkbox.