HMC627A是一款可变增益放大器，可由spi协议写入芯片内寄存器控制增益，或者使用D0-D7引脚输入的TTL电平来控制增益。如果我只使用SPI协议控制增益，那么它的外围电路中，D0-D7引脚是不是可以悬空？
您好，官网中有关HMC627A的设计资料您可先参考下哦
http://www.analog.com/cn/products/amplifiers/variable-gain-amplifiers/hmc627a.html
只使用SPI协议控制增益，D0-D7引脚状态将不会影响到寄存器配置！
因为SPI协议时P/S is kept high，再请仔细理解这句话：When P/S is low, 3-wire SPI interface inputs (SERIN, CLK, LE) are disabled and serial input register is loaded
asynchronously with parallel digital inputs (D0-D5). When Le is high, 6-bit parallel data is transferred to the attenuator.
For all modes of operations, the DVGA state will stay constant while LE is kept low.
