The invention relates to a modulation device for modulating charged particle beamlets in accordance with pattern data in a multi-beamlet charged particle lithography system. The device comprises a plate-like body, an array of beamlet deflectors, a plurality of power supply terminals (202-205) for supplying at least two different voltages, a plurality of control circuits, and a conductive slab (201) for supplying electrical power to one or more of the power supply terminals (202-205). The plate-like body is divided into an elongated beam area (51) and an elongated non-beam area (52) positioned with their long edges adjacent to each other. The beamlet deflectors are located in the beam area. The control circuits are located in non-beam area. The conductive slab is connected to the control circuits in the non-beam area. The conductive slab comprises a plurality of thin conductive plates (202-205).