DS1800 Dallas Semiconducotr, DS1800 Datasheet - Page 3

• Manufacturer Part Number: DS1800
• Description: Dual Inverting Log Gain/Attenuator
• Manufacturer: Dallas Semiconducotr

DS1800
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 referenced 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 operational amplifier. The position of the wiper terminal is selected either through CPU control or
pushbutton control.
P0A, P1A - Attenuation Pushbutton Inputs. These pushbutton 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 terminals, respectively.
P0G, P1G - Gain Pushbutton Inputs. These pushbutton inputs control wiper position and are used to
move the position of the wiper towards the IN0 and IN1 terminals, respectively.
- Serial Port Reset. The
input deactivates the 3-wire serial interface. This input is active when
RST
RST
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
synchronization.
D - Serial Data Input. The D input is used to input serial data for wiper position changes.
C
- Serial Cascade Output. The C
is an output signal used to read the contents of the current
OUT
OUT
settings of the wiper positions. As data is clocked into the D input, data corresponding to the wipers are
shifted out of the C
pin.
OUT
MODE - Pushbutton Debounce Control. The MODE pin is used to choose between a fast and slow mode
of pushbutton debouncing. When in a high state, pushbutton debounce is slow. When in a low-state,
pushbutton debounce is faster. These timing differences are discussed in the section entitled “Pushbutton
Interface Control.” The state of this pin is determined only at device power-up.
POWER-UP CONDITIONS
The position of the wipers of the DS1800 on power-up are internally set to position 127, which is the last
position before mute. The user then has the responsibility of changing the wiper position to the desired
attenuation/ gain levels.
Additionally, the serial port is stable and active within 10 microseconds. The contact closure control
interface inputs are active after 50 ms.
INTERFACE CONTROL OPTIONS
Control of the DS1800 is provided via two types of interface ports. A 3-wire CPU control interface
allows the exact wiper positions of the potentiometers to be written using two 8-bit words. A cascade
output, C
, is provided when controlling multiple devices via one CPU or when reading the wiper
OUT
positions of each potentiometer.
The second interface is a contact closure interface that allows pushbuttons to control movement of the
wiper positions. Under pushbutton control no external debounce or timing circuitry is needed. A block
diagram of the DS1800 is shown in Figure 1.
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