Technalogix TAU-100, Manual

Page: 23 / 54

VI-1
Section VI – Monitor and Control System
Control Board Overview (Series II-H)
The control printed circuit boards (PCB) are located at the front of each enclosure connected directly
to the back of the liquid crystal displays (LCD) and are identified as Series II-H PCBs. The main
purpose of the Series II-H PCB is to monitor the RF power and the DC supply voltages in the power
amplifier and filter enclosures and to monitor just the DC supply voltages in the power supply
enclosure. In all cases, a DC voltage proportional to the parameter being sampled is conditioned,
protected, buffered, and then run into an analog-to-digital converter (ADC) where software processes
the signal. The software processing determines if the parameters are within the predetermined safe
operating levels and displays the parameters on the LCD for monitoring purposes. The Series II-H PCB
can be broken apart into (5) main component areas: the power supply, interface, signal processing,
display, and microcontroller. Schematics are found later in this section.
Power Supply Components
There are (4) power supply voltages generated on the Series II-H PCB:
1. +5Vdc for all logic and general purpose PCB supply voltage.
2. +4Vdc for the LED backlighting on the LCD
3. -4Vdc for the contrast voltage required by the LCD
4. +8Vdc for the directional coupler supply
The +5Vdc is generated from a small switching power supply comprised of C1, C2, D2, L1, and U1.
This power supply accepts DC input voltages up to 40Vdc and o5Vdc at up to 1Adc. This
voltage is always on, as the ON/OFF pin on U1 is hard-wired to the on configuration.
The +4Vdc is generated from a small switching power supply comprised of components C3, C4, D3, L2,
and U2. This power supply accepts DC input voltages up to 40Vdc and o5Vdc at up to 1Adc.
The voltage then gets dropped down to +4Vdc through R1. This backlight voltage can be turned on
and off via the ON/OFF pin on U2. The PCB is setup in a manner that allows this voltage to be hard-
wired on all the time or controlled from the microcontroller through latch U11. This selection is made
with jumper J2.
The -4Vdc is generated using a switched capacitor voltage converter design, using components C6,
C7, R2, R3, U4, and VR1. U4 a5Vdc from the general p5Vdc supply and generates -
4Vdc. This voltages then gets dropped across the voltage divider (R2, R3) to generate the contrast
voltage specific to the LCD that is installed in the system.
The +8Vdc required by the directional coupler is generated with a standard linear voltage regulator,
U3. C5 helps clean up any ripple or noise that might be on the output voltage.