The Compensation Calculator spreadsheet
calculates MAX1846/MAX1847 compensation components based on the application requirements and components' specifications. User inputs are entered in column B, highlighted in blue. Calculated values are noted in red.
The Compensation Calculator spreadsheet is easy to use. The list below explains what unit information is required for, or calculated in, each cell. Just enter the required information into column B. The spreadsheet will do the rest.
B2: Chosen RFREQ
(frequency setting resistor).
D2: Calculated switching frequency (FOSC
B3: Enter the maximum input voltage.
B4: Enter the minimum input voltage.
B5: Enter the output voltage, VOUT
(must be negative).
B6: Enter the maximum output current.
D6: Calculated equivalent resistive load.
B7: Estimate VDS
, of PFET, P1, at maximum peak current (0.1V).
B8: Estimate current-sense voltage (0.1V).
D8: Calculated minimum duty cycle.
B9: Estimate voltage drop across output diode, D1 (0.5V).
D9: Calculated maximum duty cycle.
G9: Calculated RMS input-ripple current, assuming 80% efficiency.
D10: Calculated inductor-ripple current (IRIPPLE
), assuming LIR = 0.4 at VIN
D11: Calculated inductor, L .
G10: Calculated RMS output-ripple current.
F11: Calculated minimum inductor (for duty cycles greater than 50%).
B12: Enter the inductor (next lower standard value, but greater than LMIN
D12: Calculated DC current in inductor (ILDC
D13: Calculated ripple current in the inductor (ILPEAK
F13: Calculated peak current in the inductor.
H13: Calculated current-sense resistor (RCS
B14: Bottom feedback resistor, R2.
D14: Calculated top feedback resistor, R1.
B15: Enter the top feedback resistor (next higher standard value).
D15: Calculated COUT for 1% peak-to-peak ripple voltage (Excludes ESR).
B16: Enter the current-sense resistor (next lower standard value).
B17: Enter the output capacitor, COUT (next higher standard value).
D17: Calculated output pole frequency (POUT1
B18: Enter the ESR of output capacitor (RESR
D19: Calculated DC open-loop gain (ADC
B20: Enter a compensation frequency (ZESR
) less than FOSC
(G20) and FESR
D21: Calculated compensation capacitor, CFB
G22: Calculate right half-plane zero (ZRHP
) frequency .
H22: Calculated Nyquist limit (POUT2
I22: Calculated output filter cut off frequency (OUTFIL
B22: Enter the loop crossover frequency (FCROSS
) less than ZRHP
(G22) and POUT2
B23: Enter next lower standard for CFB
D23: Calculated compensation resistor, RCOMP
B24: Enter the compensation resistor, RCOMP
(next lower standard value).
D24: Calculated compensation capacitor, CCOMP
B25: Enter compensation capacitor, CCOMP
(next higher standard value).
D25: Recalculated POUT1
frequency based on compensation components.
D26: Calculated optional roll-off capacitor, CCOMP2