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DS1800

Dual Inverting Log Gain/Attenuator

DS1800

PRODUCT PREVIEW

072095 1/13

FEATURES

• Ultra–low power consumption

• Operates from 3V or 5V supplies

• Two digitally controlled, 128–position potentiometers

including mute

• Logarithmic Gain Characteristics

• Zero–crossing detection circuitry eliminates noise

caused by discrete wiper position changes

• Two Control Interfaces

– 3–wire serial CPU control

– Push–button control

• 20–pin DIP (300 Mil), 20–pin SOIC (300 Mil), and

20–pin (173 Mil) TSSOP packaging available

• Operating Temperature:

– Commercial: 0°C to 70°C

– Industrial: –40°C to 85°C

• Software and hardware mute

• Resistance Available: 53KΩ

PIN ASSIGNMENT

P1G

P1A

P0G

P0A

MUTE

AGND

IN1

OUT1

GND

OUT

CLK

RST

ZCEN

MODE

OUT0

IN0

20–PIN DIP (300 MIL)

20–PIN SOIC (300 MIL)

20–PIN TSSOP

PIN DESCRIPTION

OUT0,OUT1 – Low–end of resistor

IN0, IN1 – High–end of resistor

W0,W1 – Wiper Terminal

– 3V or 5V Power Supply Input

RST – Serial Port Reset Input

CLK – Serial Port Clock Input

D – Serial Port Data Input

OUT

– Cascade Data Output

P0G,P1G – Gain Input Pot Controls

P0A,P1A – Attenuation Input Pot Controls

ZCEN – Zero–Crossing Detect Input

MUTE – Hardware Mute Control Input

AGND – Analog Ground

GND – Ground

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

relationship of –20log(R

) giving a gain/attenu-

ation range covering +20 dB to –63 dB. Each poten-

tiometer 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, and

from –27 dB to –47 dB; 2 dB per step, and from –47 dB to

–63 dB; 4 dB per step. 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

RST

, CLK, and D. The second interface is a contact–

closure interface, allowing easy push–button control

without the need for external debounce or timing cir-

cuitry. The device also provides for software muting (via

Summary of content (13 pages)

PAGE 1
DS1800 PRODUCT PREVIEW DS1800 Dual Inverting Log Gain/Attenuator FEATURES PIN ASSIGNMENT • Ultra–low power consumption • Operates from 3V or 5V supplies • Two digitally controlled, 128–position potentiometers GND 1 20 VCC COUT 2 19 P1G CLK 3 18 P1A D 4 17 P0G RST 5 16 P0A ZCEN 6 15 MUTE MODE 7 14 AGND W0 8 13 IN1 OUT0 9 12 OUT1 10 11 W1 including mute • Logarithmic Gain Characteristics • Zero–crossing detection circuitry eliminates noise caused by discrete wipe
PAGE 2
DS1800 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”. 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.
PAGE 3
DS1800 button debounce is faster. These timing differences are discussed in the section entitled “Push–button 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.
PAGE 4
DS1800 provide the opposite function; positioning the wiper(s) closer to the INx terminals, thus providing gain. Each of these control inputs are internally pulled–up via a 50KΩ resistance. Additionally, these inputs require no external components for debouncing or timing which are provided internal to the part. Contact closure is defined as the transition from a high level to a low level on these input terminals. The DS1800 interprets input pulse widths as the means of controlling wiper movement.
PAGE 5
DS1800 Also, if operating in push–button mode, MUTE will be deactivated if an input is received over any push–button input. This input, like the push–button inputs, is internally debounced and requires no external circuitry. When the device powers up, the first activity on the mute pin will move the wipers to position 128 or the OUTx end of the potentiometer(s). Software muting was discussed in the 3–wire serial control section. Bits 7 and 15 are reserved for muting each respective potentiometer.
PAGE 6
DS1800 ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature –1.0V to +7.0V 0°C to 70°C; commercial –40°C to +85°C; industrial –55°C to 125°C 260°C for 10 seconds Storage Temperature Soldering Temperature * This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied.
PAGE 7
DS1800 ANALOG RESISTOR CHARACTERISTICS PARAMETER SYMBOL (–40°C to +85°C; VCC=2.7V to 5.5V) MIN Total Resistance TYP MAX 53 UNITS NOTES KΩ End–to–End Resistor Tolerance –20 +20 % Absolute Tolerance –0.5 –1.0 +0.5 +1.0 dB dB 9 Tap–to–Tap Tolerance –0.5 +0.5 dB 7 Interchannel Matching –0.25 –0.5 +0.25 +0.5 dB dB 6 1 MHz 13 650 ppm/°C 0.002 % 13 Output Noise (20 Hz to 20 KHz, Grounded Input, Tap=0 dB) 2.
PAGE 8
DS1800 AC ELECTRICAL CHARACTERISTICS PARAMETER (–40°C to +85°C; VCC=2.7V to 5.
PAGE 9
DS1800 8. Power–up time is the time for all push–button inputs to be stable and active once power has reached a valid level, 2.7V min. 9. Absolute tolerance is used to determine wiper voltage versus expected wiper voltage as determined by wiper position. The DS1800 is bounded by a ±0.5 dB absolute tolerance from position 0 to position 112 and ±1 dB tolerance from position 113 to position 127. 10.
PAGE 10
DS1800 RECOMMENDED CIRCUIT CONFIGURATION Figure 2 DS1800 VI INx OUTx RF RI Wx – VO + VCC/2 VO/VI GAIN/ATTENUATION VS.
PAGE 11
DS1800 RF/RI RELATIONSHIP VS.
PAGE 12
DS1800 16–BIT I/O SHIFT REGISTER Figure 6 WIPER–0 POSITION VALUE WIPER–1 POSITION VALUE 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 CONTACT CLOSURE TIMING DIAGRAMS Figure 7 (a) Single Pulse Inputs tCPW VIH VIL (b) Repetitive Pulse Inputs tCPW tHPW VIH VIL (c) Continuous Pulse Inputs tCCP VIH VIL CASCADING OPERATION Figure 8 D DS1800 #1 COUT D DS1800 COUT #2 DS1800 #n 2K–20KΩ (ISOLATION RESISTOR) 072095 12/13 D COUT
PAGE 13
DS1800 DIGITAL OUTPUT LOAD Figure 9 5V 1.1 KΩ D.U.T. 680Ω 50 pF INTERNAL GROUND CONNECTIONS Figure 10 AGND GND 100Ω (TYPICAL) NOTE: GND and AGND must be tied to the same voltage level.