that5171 THAT Corporation, that5171 Datasheet - Page 7

• Manufacturer Part Number: that5171
• Description: High-performance Digital Preamplifier Controller Ic
• Manufacturer: THAT Corporation

THAT5171 High-Performance
Digital Preamplifier Controller IC
at the outputs, it does require time to react. When
gain is changed, particularly if a sudden large
increase in gain is initiated (e.g., 5.6dB to 68.6dB),
the servo output will not change instantaneously with
the gain change. Immediately after the gain increase,
the servo will be supplying a dc offset appropriate for
the lower gain, and the dc at the output will thus
change, on a transient basis, to a higher level. As the
servo acquires the new required value, the dc offset
will be driven down to under 1.5mV.
change, THAT recommends that gain be increased
slowly by sending many commands to the 5171 that
increase gain a few dB at a time, over a second or
more of total time. This replaces the one big change
in dc offset with a series of much smaller ones,
allowing the servo some time to settle (at least par-
tially) in between each step. Note that the problem is
much less audible during stepwise decreases in gain,
since the servo’s output is not amplified as much at
the new (lower) gain as it was at the previous one.
While the servo is effective at minimizing dc offset
To minimize the sonic impact of the dc offset
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Page 7 of 20
Control Interface
peripheral interface (SPI) port to accept external gain
commands. The SPI inputs accept 3.3V logic levels.
The 5171 address is established during reset by
resistors or other appropriate loads connected to the
first three general-purpose outputs (GPOs 0 through
2). During reset, these serve as inputs only for pro-
gramming the device’s three-bit address. Addresses
from 0 through 7 (binary) are accepted.
applications.
revisions of the 5171, ensure that GPO3 is tied to a
logic level of 0 during reset.
to 10MHz.
purpose outputs (the fourth one is not used for chip
addressing). These provide 3.3V logic signals to drive
whatever a designer may require.
The
The GPO3 is reserved as an input for future
The SPI interface may be clocked at speeds of up
As just mentioned, the 5171 offers four general
5171
To ensure compatibility with future
includes
an
Document 600133 Rev 02
addressable
serial-