13.24.1.7 Charge Pump Results

The maximum charge pump flying capacitor value is 202 nF to maintain a 95% voltage transfer ratio on the first charge pump cycle. Larger capacitor values may be used, but they will require more cycles to charge to maximum voltage. The minimum required output capacitor value is 2.65 µF to supply 20 mA for 13.3 µs with a 100 mV drop. A larger output capacitor may be used to cover losses due to capacitor tolerance over temperature, capacitor dielectric and PCB losses.

These are approximate calculations. The actual voltages may vary due to incomplete charging or discharging of capacitors per cycle due to load changes. The charge pump calculations assume the charge pump is able to charge up the external boot cap within a few cycles.