Rainbow Electronics DS1800 - Manual (Page 2)

DS1800
072095 2/13
CPU) or hardware muting (MUTE control input). The
hardware mute is a toggle type which returns the wiper
positions to their prior states. Additional information on
CPU and push–button control is described under the
section entitled “OPERATION”.
The DS1800 is available in 20–pin DIPs, SOICs, and
TSSOPs. One standard resistance grade of 53K
Ω
is
available for the device.
OPERATION
The DS1800 provides two 129–position 45K
Ω
poten-
tiometers. These potentiometers are specifically
designed to operate in the configuration shown in Figure
2. Under this configuration the V0/VI relationship pro-
vides the gain/attenuation function of –20log(R
F
/R
I
)
over a range of +20 dB to –63 dB. This function is illus-
trated in Figure 3 as a graph of gain/attenuation versus
position. Figure 4 provides the relationship between R
F
and R
I
as a function of position.
The DS1800 has a total of 129 positions including a
mute position. Five areas of resolution are provided
over the gain/attenuation range and are illustrated in
Figure 3. From position 0 to position 68, a resolution of
0.25 dB per step is attained covering a gain/attenuation
range of +20 dB to +3 dB. From position 68 to position
98, 0.5 dB per step of resolution is attained covering +3
dB to –12 dB of gain/attenuation. Positions 98 to 113
have 1 dB per step resolution and cover a gain/attenua-
tion range of –12 to –27 dB. Positions 113 to 123 pro-
vide 2 dB per step and cover a gain/attenuation range of
–27 dB to –47 dB. Positions 123 to 127 provide 4 dB per
step and cover a gain/attenuation range of –47 dB to 63
dB. Position 128 is the mute position and typically pro-
vides 100 dB of attenuation.
PIN DESCRIPTIONS
The DS1800 has a total of 20 pins which provide various
functions for the device. This section provides a
description of each pin’s operation.
V
CC
– Power Supply Voltage Input. The DS1800 will
support 3V or 5V power supply operation.
GND – Ground. The DS1800 has two ground pins. The
GND supports the digital ground for the device.
AGND – Analog Ground. The DS1800 has two ground
pins. The AGND supports analog ground for the device.
IN0, IN1 – Input terminals for the two respective poten-
tiometers as shown in Figure 2. These terminals should
be connected to the analog signal,VI, to provide the
gain/attenuation characteristics stated. These termi-
nals are referenced as INx in the Figure 2 drawing.
OUT0, OUT1 – Analog Outputs. These pins should be
connected to the output terminal of the operational
amplifier as shown in Figure 2. These inputs are refer-
enced as OUTx in the Figure 2 drawing.
W0, W1 – Wiper Terminals. The wiper terminals of each
pot are connected to the inverting terminal of the opera-
tional amplifier. The position of the wiper terminal is
selected either through CPU control or push–button
control.
P0A, P1A – Attenuation Push–button Inputs. These
push–button inputs are used to control wiper position of
the part . Activity on these inputs will cause the position
of the wiper to move towards the OUT0, and OUT1 ter-
minals, respectively.
P0G, P1G – Gain Push–button Inputs. These push–
button inputs control wiper position and are used to
move the position of the wiper towards the IN0 and IN1
terminals, respectively.
RST – Serial Port Reset. The RST input deactivates the
3–wire serial interface. This input is active when in the
low–state. All 3–wire communications must take place
when this input is in a high state.
CLK – Serial Clock Input. The CLK input is the positive–
edge clock signal input used for 3–wire timing synchro-
nization.
D – Serial Data Input. The D input is used to input serial
data for wiper position changes.
C
OUT
– Serial Cascade Output. The C
OUT
is an output
signal used to read the contents of the current settings
of the wiper positions. As data is clocked into the D
input, data corresponding to the wipers are shifted out of
the C
OUT
pin.
MODE – Push–button Debounce Control. The MODE
pin is used to choose between a fast and slow mode of
push–button debouncing. When in a high state, push–
button debounce is slow. When in a low–state, push–