DS1800 Dallas Semiconducotr, DS1800 Datasheet - Page 2

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

DESCRIPTION
The DS1800 is a dual audio-taper potentiometer designed specifically for use in the feedback path of the
inverting configuration of an operational amplifier (see Figure 2). In this configuration, the DS1800
provides a V
dB. Each potentiometer has a total of 129 positions including mute. The DS1800 provides five areas of
resolution, which include: 0.25 dB per step from +20 dB to +3 dB; 0.5 dB per step from +3 dB to -12 dB;
1 dB from -12 dB to -27 dB; 2 dB per step from -27 dB to -47 dB; and 4 dB per step from -47 dB to -63
dB. The mute position provides 100 dB of attenuation.
The DS1800 has two control interfaces (see Figure 1). The first is a 3-wire serial CPU interface
consisting of
button control without the need for external debounce or timing circuitry. The device also provides for
software muting (via 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 53 k =is
available for the device.
OPERATION
The DS1800 provides two 129-position 45 k
designed to operate in the configuration shown in Figure 2. Under this configuration the V0/VI
relationship provides the gain/attenuation function of -20log(R
This function is illustrated in Figure 3 as a graph of gain/attenuation versus position. Figure 4 provides
the relationship between R
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/attenuation range of -12 to -27 dB.
Positions 113 to 123 provide 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 provides 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
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 potentiometers as shown in Figure 2. These terminals
should be connected to the analog signal, VI, to provide the gain/attenuation characteristics stated. These
terminals are referenced as INx in the Figure 2 drawing.
CC
- Power Supply Voltage Input. The DS1800 will support 3V or 5V power supply operation.
O
RST
/V
I
, CLK, and D. The second interface is a contact-closure interface, allowing easy push-
relationship of -20log(R
F
and R
I
as a function of position.
F
/R
I
), giving a gain/attenuation range covering +20 dB to -63
potentiometers. These potentiometers are specifically
2
of
14
F
/R
I
) over a range of +20 dB to -63 dB.
DS1800