2-36 Workstation 5 Field Service Guide
Workstation 5 System Board Technical Descriptions
System Board Power Distribution
Working Domain Voltages
The following describes the Working Domain Voltages.
In response to the user pressing the power button or connecting the AC power
cable, the PMC in the CS5536 Companion Device issues the WORKING signal
to enable the following voltages.
VCC12
The ‘Always ON’ +12V output is fed to a switch consisting of U22 and
Q25 (Sht24) to produce the VCC12 output. When VCC5 (also the working
domain, see below) goes active, this turns on Q25, which in turn enables
Q22, switching on VCC12.
VCC12 powers many system board components including the audio power
amp, LCD Panel and Backlight Inverter, Memory Voltage Regulator U43
(Sht25), and the RS232 Line Drivers/Receivers.
VCC12 is used on Sheet 30 to generate VCC24V. See the Cash Drawer
Interface for more information about VCC24V.
VCC3
VCC3 is produced by U38 REG#2. The SoftStart input to this regulator,
SS_STBY2, is enabled by the WORKING output of the Companion chip.
Q16 inverts this signal to the active low PS_ON# and Q13 inverts the
signal to the active high STBY_3V.
Output switching is handled by Q19 and Q20 through inductor L4 and
EC28. The over current trip point is determined by R293/C298 connected
across the TRIP2 input.
VCC5
VCC5 is produced by U38 REG#3. The SoftStart input to this regulator,
SS_STBY3, is enabled by the WORKING output of the Companion chip.
Q16 inverts this signal to the active low PS_ON# and Q12 inverts the
signal to the active high STBY_5V.
Output switching is handled by Q18 and Q17 through inductor L5 and
EC27. The over current trip point is determined by R297/C302 across the
TRIP3 input.
VCC12-
VCC12- is derived from the SW_3 output of U38, through a combination
of D24, D26, and EC25. VCC12- is used only by the RS232 Line
Drivers/Receivers.
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