ADI AD5360 调整DAC输出方案

　　如何使用内部校准寄存器调整DAC电压输出范围？AD5360是一种采用8 mm×8 mm 外形尺寸56 引脚LFCSP封装的高集成度16通道串行输入±10 V电压输出16 bit DAC。它提供一种4倍VREF标称输出电压范围，例如，如果某项设计需要－8 V～+8 V输出电压范围，这属于一种非工业标准4 V参考电压，它没有考虑到DAC的零点误差和满度误差，并且可能会影响输出电压范围。

　　为了克服这个问题，该解决方案提供一种高于要求的电压范围的可选择参考电压，并且使用内部增益寄存器（m）和失调寄存器（c）独立调整每个通道输出达到要求的范围。

　　为了给出－8.192 V～＋8.192 V（包括零点误差和满度误差）大约输出范围，使用4.096 V参考电压。

　　测量零点电压和满度电压，例如分别为－8.193 V和＋8.195 V

　　计算LSB的大小，即8.195 V － (－8.193 V)/65536 = 250 μV。

　　为了将零点电压从－8.193 V移动到－8 V需要的步距为0.193 V/250 μV = 772 LSB

　　现在的满度电压为8.195 V+0.193 V=+8.388 V。为了从+8.388 V降低到+8 V需要的步距为0.388 V/250 μV = 1552 LSB。

　　你现在可以将这些数据设置到DAC通道的失调寄存器（c）和增益寄存器（m）

　　失调寄存器的默认值为32768。根据32768 + 772 = 33540，对给定的－8 V零点电压重新设置这个数据。

　　增益寄存器的默认值为65535。根据35535－1552 = 63983，对给定的＋8 V零点电压重新设置这个数据。

　　The AD5360/AD5361 contain 16, 16-/14-bit DACs in a single 52-lead LQFP package. It provides buffered voltage outputs with a span four times the reference voltage. The gain and offset of each DAC can be independently trimmed to remove errors. For even greater flexibility, the device is divided into two groups of eight DACs, and the output range of each group can be independently adjusted by an offset DAC.

　　The AD5360/AD5361 offer guaranteed operation over a wide supply range with VSS from −4.5 V to −16.5 V and VDD from +8 V to +16.5 V. The output amplifier headroom requirement is 1.4 V operating with a load current of 1 mA.

　　The AD5360/AD5361 have a high speed 4-wire serial interface, which is compatible with SPI, QSPI™, MICROWIRE™, and DSP interface standards and can handle clock speeds of up to 50 MHz. All the outputs can be updated simultaneously by taking the LDAC input low. Each channel has a programmable gain and an offset adjust register.

　　Each DAC output is amplified and buffered on-chip with respect to an external SIGGND input. The DAC outputs can also be switched to SIGGND via the CLR pin.

　　主要特性：

　　16-channel DAC in 52-lead LQFP package

　　Guaranteed monotonic to 16/14 bits

　　Nominal output voltage range of −10 V to +10 V

　　Multiple output spans available

　　Temperature monitoring function

　　Channel monitoring multiplexer

　　GPIO function

　　System calibration function allowing user-programmable offset and gain

　　Channel grouping and addressing features

　　Data error checking feature

　　SPI-compatible serial interface

　　2.5 V to 5.5 V digital interface

　　Digital reset (RESET)

　　Clear function to user-defined SIGGNDx

　　Simultaneousupdateof DAC outputs

　　应用：

　　Instrumentation

　　Industrial control systems

　　Level setting in automatic test equipment (ATE)

　　Variable optical attenuators (VOA)

　　Optical line cards

　　图1。AD5360功能方框图

　　图2。和Blackfin DSP 的连接图