3
Hardware description and setup
3.1
Block diagram
Figure 4.
STEVAL-PCC020V1 block diagram
3.2
Galvanic isolation
The
has to be placed on the offline converter primary side: the galvanic isolation between the USB
and the remaining electronic of the board prevents any voltage from reaching the host PC and causing electrical
damage or interference.
3.3
Power supply
The
interface board is self-supplied via the 5 V USB connector.
This voltage directly supplies U3 and the related circuitry.
A dual isolated DC-DC module (U5) is used to supply the remaining part of the board, maintaining the isolation
among the PC and the target sides.
U5 generates two supplies, loosely regulated (+5 V and +20 V).
3.3.1
MCU subsystem supply (5 V)
The +5 V supply is later converted to a stable and clean +3V3 thanks to the linear regulator U6, which is always
on.
3.3.2
VCC generation (20 V)
The +20 V is always generated from +5 V and +15 V cascaded together (VOUT2- is referenced to VOUT1+ in
place of ground).
This voltage is later on supplied by the linear regulator U8 which has the following roles:
•
to generate a 18.5 V;
•
to act as a switch; U8 is enabled thanks to the MCU GPIO PA14 configured in open drain mode. When the
MCU wants to enable the VCC generation, PA14 is driven low.
D5 provides an OR-ing diode which, by default, is short-circuited by R17 resistor (0 W).
UM2342
Hardware description and setup
UM2342
-
Rev 1
page 5/57
