You're going to have to be more descriptive. Answer questions such as:
What type of pulse shape are you using?
Do you want to decrease the time required to charge something?
Do you want to double the frequency of an arbitrary pulse shape?
The LM2907/LM2917 has a charge-pump that doubles the input frequency so that the DC output of its f to V tachometer is fast to frequency changes and has low ripple.