A very low power 16-channel ASIC has been designed and fabricated in a standard 0.35 $mu{hbox{m}}$ CMOS technology. It is to be used as the front-end electronics of the micro-channel plates (MCPs) based detector of a 3D space plasma analyzer. Each channel includes a charge sensitive amplifier (CSA) and a discriminator. With a CSA conversion gain of 0.5 mV/fC, the ASIC is able to detect charges emitted by the MCPs over a wide dynamic range of 10 fC to 3.5 pC. The CSA pulse-pair-resolution (PPR) is 170 ns, and the maximum counting rate frequency is 7.5 MHz for input charges limited to 100 fC and 4.6 MHz for full scale inputs. The CSA input devices are optimized for a detector capacitance varying in the range of 2-12 pF. The measured input equivalent noise charge $({hbox{ENC}}_{rm in})$ is 1.3 fC $+$ 0.1 fC/pF rms. These features have been obtained with an unprecedented low power consumption of only 0.64 mW per channel. Experimental tests under the extended temperature range of $-{hbox{40}}~^{circ}{hbox{C}}$ to 85$~^{circ}{hbox{C}}$ have shown no significant performance variations.