HP 3478A Technical Manual page 109

3478A
Figure 7-F-15. Determining the DAC Setting
S-4 current and the S-I current is 1/1000 the S-4 current.
The S + 2 and S + I currents use the same circuitry con-
figuration as the S+4 current (see Figure 7-F-11). In this
case, resistor values chosen are such that the S + 2
current is 1/100 the value of S+4 current and S+ 1 is
1/1000 the value of S+4.
7-F-49. A/D Converter and Reference Circuitry. The
A/D Converter Circuitry consists of the A/D Hybrid
(U403), A/D Integrator (U401 and associated circuitry),
A/D Controller (U462), and a DAC (U465 and associated
circuitry). Since the Voltage Reference Cir- cuitry (U461,
U405, U404, U402, and associated cir- cuitry) uses part
of the A/D Hybrid (for stability pur- poses) and since it is
also used by the A/D Converter, it is considered part of
the converter circuitry.
following explanation on the A/D Converter Circuitry
(except for the DAC, see paragraph 7-F-46 and 7-F47
for its explanation).
Figure 7-F-16, operates as follows:
latches, decoders, and a clock generator. The decoders
receive control information from the A/D Controller, then
decode the information and pass the new information to
the latches.
information to the various switches in the hybrid during
each clock pulse. The clock pulses are generated by the
clock
Figure 7-F-16. A/D Hybrid (U403)
7-F-15
Refer to Schematic 3 for the
a. A/D Hybrid (U403). The A/D Hybrid, shown in
1.The A/D Hybrid has, internal to it, various
The latches then transfer the new
TM 11-6625-3071-14