james.qiu
Newbie level 6

When I am reading the Keysight 34970 DAQ datasheet, it lists all the relay Multiplexer circuit. the relay used in Multiplexer board is latched relay.
the control signal is from MCU to 74HC574, the signal from 74hc574 to transistor base pin. the driver for coil is made by 2 PNP + 2 NPN transistor a H bridge.
why add a 74hc574 between MCU output and transistor base?
why some relay drivers not use freewheeling diode, some drivers use freewheeling diode?
why some relay drivers use two freewheeling diodes?
driver no freewheeling diode page261
drivers use two freewheeling diodes on set relay direction. page242
the control signal is from MCU to 74HC574, the signal from 74hc574 to transistor base pin. the driver for coil is made by 2 PNP + 2 NPN transistor a H bridge.
why add a 74hc574 between MCU output and transistor base?
why some relay drivers not use freewheeling diode, some drivers use freewheeling diode?
why some relay drivers use two freewheeling diodes?
driver no freewheeling diode page261
drivers use two freewheeling diodes on set relay direction. page242