双极性工作为maxrefdes74

　　The MAXREFDES74# is a high-speed， 18-bit precision data-acquisition system featuring the MAX11156 ADC and MAX5318 DAC. The reference design allows for both unipolar and bipolar modes of operation from a single +15V to +20V DC source. The unipolar mode operates as expected; however， the bipolar mode contains a potential power sequencing issue upon startup if J6 is in position 1-2. This only applies to boards using a 100kΩ resistor for R31. The reference design uses a single +15V to +20V power source， an on-board transformer to create power isolation， and relies on several regulators to generate the power rails necessary for board operation. When operating in bipolar mode， J6 connects the MAX664 regulator output to AVSS of the MAX5318. Figure 1 provides a block diagram of the connections between the MAX5318 and MAX664 along with the power supplies to each chip.