6-7
RA7. The signal labeled PCON (power control) is
driven from the DAC on the Display PCB and is
the control voltage for output power. The range
for P
CON is 0V-9V.
IMEA is a ratio of the output current measured,
scaled from 0V to 4V maximum. I
MEA allows the
monitor microcontroller to monitor the output
current. Too much output current will cause RF
to be inhibited and an error code displayed.
FB_EN is “cleared” by the control microcontroller
anytime that Cut, Blend, Bipolar, or Pinpoint are
activated. This signal enables the power control
circuit when cleared. With FB_EN set, an offset
is placed on the non-inverting input of the differ
-
ential amplifier, causing P
ERR to be greater than 0
volts, which in the event of a failure, would force
the HVDC to be low. P
ERR was covered earlier
but as a reminder, this signal is the difference
between the measured output power and request
-
ed power. When P
ERR is positive, the HVDC
is decreased and when negative the HVDC is
increased.
6.3.2 RF Logic [U7 on the Power Control
Assembly]
U7 is an FPGA, programmable logic device that
is used to develop the RF amplifier drive signals
for all modes. This device will be described with
respect to the I/O only. Listed below is a brief
description of the I/O on U7.
COND0 - COND7 (Control Microcontroller
Inputs)
The hex count on these inputs select which
RF amplifier will be driven and sets the
right drive signals for the mode. The eight
signals are latched into U7 when an activa
-
tion request is made. (See display panel
description for hex values as related to modes
requested.)
RF_CLK (RF Clock - input)
A 1MHz clock for RF drive timing. Runs con
-
tinuously.
RF_INH (RF inhibit - input from monitor
microcontroller)
When CLEARED (low), RF is inhibited.
CLEARED when no activation is requested or
if a failure is detected.
FB_EN (Full Bridge Enable - input from control
microcontroller)
CLEARED when Cut, Blend, Pinpoint or
Bipolar modes are requested. A
CLEARED is
required to enable output power control.
OV_TST (Over voltage test - input from control
microcontroller)
A test pin used only to test the ABC™ Over
Voltage circuit during system initialization by
a series of pulses that simulate an ABC™ over
voltage condition. After the test is conducted,
the signal is latched low.
A/T (Active/Target - output to control
microcontroller)
ABC™ mode only - A high occurs when ABC™
is in the ACTIVE mode; a low occurs when
ABC™ is in the TARGET Mode. For tone
control only as the two modes have distinctive
tones.
BM>80 (Beam greater than 80W - from control
microcontroller)
SET when ABC™ power is greater than 80W.
An internal limit in U7 for switching from
active to target mode.
RFEN: (RF Enable - input from control
microcontroller)
SET to enable RF Drive to the amplifiers.
RST: (Reset - from system reset signal)
A SET causes internal latches to CLEAR.
CT_PCON: (Cut Power Control voltage select)
SET when Cut or Blend modes are activated .
Switches Pcon for Cut.
CG_PCON: (Coag Power Control voltage select)
SET when Pinpoint is activated. Switches Pcon
for Pinpoint.
BP_P
CON: (Bipolar Power Control voltage select)
SET when Bipolar is activated. Switches Pcon
for Bipolar.
SE_PCON: (PCON for Spray & ABC™ active
select)
SET for Spray or ABC™ active only. Switches in
Pcon for Spray and ABC™ active.
BM_BST: (ABC™ Booster voltage control level)
SET to enable Boost Pcon.
BM_TAR: (ABC™ Target voltage control level)
SET to enable Target Pcon.
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