Power Supply - HP 5384A Operating And Service Manual

HP 5384A and HP 5385A
Service
VH
NOTE:
WHILE ONLY A LOGICAL "1" IS
2.2V
TW
SHOWN HERE, ALL LOGICAL BITS MUST
CONFORM TO THE SAME BASIC SPECIFICATIONS.
Tf{-......_
l.-----1
~--------T1--------~
1.35V
0.6V
0.3V
I
I
I
I
I
I
I
I
I
I
I
TR
O.OOV
_ _j
I
I
I
I
I
I
1-'
I
'------1
-0.3V
I
V1 \
I \
I \
I
BEGINNING OF \
Minimum Maximum
Parameter
NEXT BIT-
TR 30n8 120n8
-1.35V
1/
(NOT NEXT FRAME)
\ 7.
r200 n8'
TR " ' /
Ti
1.9!'8 101'8
TO
11'8
TW 950n8 1500n8
-2.2V
'When tested with a 20 meter cable.
VL
Figure 8-42. Open Circuit Output Waveform
8-229. Frames are asynchronous with respect to
each other. That means no common system clock is
necessary in HP-IL. The sync bit requires six micro-
seconds to transmit while other bits take four micro-
seconds. A complete frame, which may contain one
byte of data, takes46 microseconds assuming no extra
delay between bits. If we further assume no extra
delay between frames, a maximum loop rate of
approximately 20 kilobytes per second could be
achieved. In a typical application, hardware and
software delays lower this rate to somewhere between
three and five kilobytes per second.
8-230. POWER SUPPLY
8-231. Refer to Figures 8-50 or 8-51 (sheet 2 of 2), A 1
Motherboard Power Supply Assembly for the follow-
ing discussion on the theory of operation.
8-232. The HP 5384A and HP 5385A power supply is a
de to de converter having a constant frequency,
variable pulse width modulator. There are three
sources of raw power available; ac line, external de
and a 6-volt internal battery. Although only one of the
sources is necessary to power the instrument, any or
all may be connected.
8-30
8-233. In the de to de down converter type power
supply, power is pulsed into an output filter that
smooths the large pulses into very small changes that
are acceptable and can be called de. By modifying the
ratio of on to off time of the switch transistor, (pulse
width modulation) the output voltage can be adjusted.
8-234. When the switch transistor is saturated, cur-
rent ramps up in L 1. Some of the energy is dissipated
in the load, and some energy is stored in the magnetic
field of L 1 and the electric field of C36 and C69. When
the switch transistor turns off, the magnetic field
around L 1 collapses and transfers the energy in L 1 to
the load and filter capacitor via CR12.
8-235. Power is applied to the primary of T1 through
noise filter L7 (and L6 in the return line). Fuse F1 is a
1/4 amp slow blow fuse mounted inside the counter
and is intended to blow only in the case of catastrophic
failure of the transformer T1 or bridge rectifier CR8.
All other failures should result in the 2 amp fast blow
fuse F2 opening. The 2 amp fuse is accessible from the
rear panel.
8-236. External de polarity protection and shorting
protection is provided.
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