Low vin high efficiency chargepump

A charge pump circuit comprising:

• a first charge transfer circuit path coupled including a first boost capacitor coupled to a first clock input, a first charge switch coupled to a circuit input, and a first discharge switch coupled to a circuit output, wherein a source-or-drain connection of the first charge switch is coupled to a source-or-drain connection of the first discharge switch;
• a second charge transfer circuit path including a second boost capacitor coupled to a second clock input, a second charge switch coupled to the circuit input, and a second discharge switch coupled to the circuit output, wherein a source-or-drain connection of the second charge switch is coupled to a source-or-drain connection of the second discharge switch;
• a first charge control circuit including a first gate switch coupled to a gate input of the first discharge switch, and a first gate-drive capacitor coupled to a third clock input and the gate input of the second discharge switch;
• and
• a second charge control circuit including a second gate switch coupled to a gate input of the second discharge switch, and a second gate-drive capacitor coupled to a fourth clock input and the gate input of the first discharge switch.

A method of operating a charge pump circuit, the method comprising:

• charging a first boost capacitor using a circuit input and a first clock input, wherein the charging of the first boost capacitor is controlled using a first charge switch and discharging of the first boost capacitor to a circuit output is controlled using a first discharge switch coupled to the first charge switch;
• charging a second boost capacitor using the circuit input and a second clock input, wherein the charging of the second boost circuit is controlled using a second charge switch and discharging of the second boost capacitor to the circuit output is controlled using a second discharge switch coupled to the second charge switch;
• charging a first drive capacitor using the first clock input and charging a second drive capacitor using the second clock input;
• turning on the first charge switch using the second drive capacitor to charge the first boost capacitor and turning on the first discharge switch using the second boost capacitor to discharge the first boost capacitor;
• and
• turning on the second charge switch using the first drive capacitor to charge the second boost capacitor and turning on the second discharge switch using the first boost capacitor to discharge the second boost capacitor.