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Picobus - further information

This page expands on our basic picobus information page.

There is one dual function line, Q3-, which can function as a switch to Vcc and/or as a negative supply, depending on the microprocessor motherboard implementation. No system has yet implemented this feature


Implementation Q3- Function
No negative supply Q3- function same as Q0-Q2
No Q3 Mux select Q3- is nominal -7V
Both -Vee and Q3 Muxsel Q3- is push-pull driver, switch to Vcc at time T=3, switch to -7V at other times
The presence of a negative voltage simplifies the design of some circuitry. The -7V may also be used in conjunction with the +5V to supply 12V for a relay coil. The translation of a normal Qn signal, which is typically 0v...5v level, to the Q3- signal, which is -7v...5v level, does require extra circuitry. A typical circuit for this translation appears below.

Note: This circuit is presented as a typical
example only and is not mandatory
Typical pico bus Q3- drive
Implementing optional Q3-

Any circuitry utilizing the -7V rail must include a supply switch, such that -7V is only connected when +5V and Gnd are detected. Devices using -7V should also feature a prominent warning in the instructions for the user to remove power before connecting or disconnecting the Picobus connector.

This page was last updated 08 July 2010

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