Circuit for clamping current in a charge pump
View Patent ↗A circuit for clamping current in a charge pump is disclosed. The charge pump includes switching circuitry having a number of switching circuitry transistors. Each of first and second pairs of transistors in the circuit can provide an additional path for current from its associated one of the switching circuitry transistors during off-switching of that transistor so that a spike in current from the switching circuitry transistor is only partially transmitted through a path extending between the switching circuitry transistor and a capacitor of the charge pump.
1. A circuit for clamping current in a charge pump, the charge pump including switching circuitry and a capacitor, and the charge pump defining first and second paths through which current is transmitted to/received from the capacitor, at least one parasitic spike in current from at least one of a number of transistors of the switching circuitry being generated during switching off of the at least one transistor, the circuit comprising:
first and second pairs of transistors, each of the transistors supporting on and off states, and each including a control electrode to permit transition between said states to be controlled, one of said first pair of transistors electrically connected to a first of the transistors of the switching circuitry through a first node, the first path extending through said first node, and one of said second pair of transistors electrically connected to a second of the transistors of the switching circuitry through a second node, the second path extending through said second node, both transistors of each of the first and second pairs of transistors being in a common additional current path from a respective one of the first and second nodes;
first delay introducing inverter circuitry; and
second delay introducing inverter circuitry, each of said first delay introducing inverter circuitry and said second delay introducing inverter circuitry having an input signal connected to the control electrode of the one of the respective pair of transistors and an output signal connected to the control electrode of the other of the respective pair of transistors, and for a moment when the switching off occurs, both said input signal and said output signal having values that produce said on state, and after a delay, the output signal having a value that produces an off state in the other of the respective pair of transistors,
at least one of said first and second pairs of transistors providing the common additional current path for the current from the at least one of the transistors during the switching off only when both of the respective pair of transistors are in the on state and before the other of the respective pair of transistors is off so that the at least one parasitic spike is only partially communicated through any paths to the capacitor.
2. The circuit as claimed in claim 1 , wherein said first and second pairs of transistors are FETs, and the control electrodes of said first and second pairs of FETs are FET gates.
3. The circuit as claimed in claim 1 , wherein the transistors of the switching circuitry are FETs.
4. The circuit as claimed in claim 1 , wherein the at least one parasitic spike is two parasitic spikes, each being generated in a different one of the transistors of the switching circuitry, one of the parasitic spikes being asymmetrical as compared to the other parasitic spike.
5. The circuit as claimed in claim 1 , further comprising a number of capacitor-plugged devices, one of said capacitor-plugged devices for pumping additional charge into said first node during the switching off of the at least one of the transistors.
6. The circuit as claimed in claim 1 , wherein the charge pump further includes first and second FETs both electrically connected to the capacitor, the first FET positioned along the first path, the second FET positioned along the second path.