We use the AD5535B evaluation board to provide 32 channel bias voltage for our silicon photon sensors(MPPC from Hamamatsu) that have a working voltage ranges from 65 to 70 volts with consumed current around 1 mA.The AD5535B only provide a maximum source current around 550 uA. We tried to directly drive our photon sensor and it only goes up to about 64.4 volts.
I check the datasheet and found AD5535B provide much larger sink current, around -2 mA. My idea is to increase the driven capacity of the DAC output with a pull up resistor that connected to 100 V power source. Assuming the output voltage is 67 V, the input high voltage Vpp is 100 V, the pull up resistor with 17.5 k Ohms gives 2 mA current, then 1 mA goes to the photon sensor and the other 1 mA goes to the DAC as a sink current. I tested the output and found it only goes up to 67.2 V and can not goes up anymore. The datasheet only gives the Output Amplifier Source and Sink Capability with output voltage of 70 V, I want to know how it will change for different output voltage setting? Is there a detailed circuit diagram of the chip's output stage? Could you give some other suggestions to increase the chip's current driven capacity?
The max current that each channel is capable of driving is 550uA. This part is not designed to be capable of driving larger loads. It was designed to drive MEMS mirrors which demanded small currents. The typical plot which you refer to should be similar right across the range, so it can provide 550uA across the full specified range of 1V to Vpp-1V. The sink current is not specified on this part as it was not designed for such an application. The output stage consisting of a DAC and buffer configuration as shown on the datasheet is attached.
Precision Applications Group.
The AD5535 is the predecessor of the AD5535B. The output current capability is slightly better at 700uA but again it's not specified for sinking capabilities. This part is being discontinued.
Precision Applications Group
Unfortunately we don't have high voltage buffers.
How about the AD5535 chip? It provides the maximum sink current of 2.8 mA
The required current is around 500 uA and it may worth to try the AD5535 instead. Are there some buffer circuits for this kind of DAC chips for high voltage and high precision applications?