Dallas DS1800 Dual inverting log gain/attenuator Datasheet

DS1800
Dual Inverting Log Gain/Attenuator
www.dalsemi.com
FEATURES
PIN ASSIGNMENT
Ultra-low power consumption
Operates from 3V or 5V supplies
Two digitally controlled, 128-position
potentiometers including mute
Logarithmic gain characteristics
Zero-crossing detection eliminates noise
caused by discrete wiper changes
Two control interfaces
- 3-wire serial CPU control
- Pushbutton control
20-pin DIP (300-mil), 20-pin SOIV (300mil), and 20-pin (173-mil) TSSOP packaging
available
Operating Temperature Range:
- Industrial: -40°C to +85°C
Software and hardware mute
Standard Resistance Available: 53KΩ
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
IN0
20-Pin DIP (300-mil)
20-Pin SOIC (300-mil)
20-Pin TSSOP
See Mech. Drawings Section
PIN DESCIPTION
OUT0,OUT1
IN0, IN1
W0,W1
VCC
RST
CLK
D
COUT
P0G,P1G
P0A,P1A
ZCEN
MUTE
AGND
GND
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-
Low-end of resistor
High-end of resistor
Wiper Terminal
3V or 5V Power Supply Input
Serial Port Reset Input
Serial Port Clock Input
Serial Port Data Input
Cascade Data Output
Gain Input Pot Controls
Attenuation Input Pot Controls
Zero-Crossing Detect Input
Hardware Mute Control Input
Analog Ground
Ground
032000
DS1800
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 VO /VI relationship of -20log(RF/RI), giving a gain/attenuation range covering +20 dB to -63
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 RST , CLK, and D. The second interface is a contact-closure interface, allowing easy pushbutton 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 pushbutton 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 kΩ=is
available for the device.
OPERATION
The DS1800 provides two 129-position 45 kΩ potentiometers. These potentiometers are specifically
designed to operate in the configuration shown in Figure 2. Under this configuration the V0/VI
relationship provides the gain/attenuation function of -20log(RF/RI) over a range of +20 dB to -63 dB.
This function is illustrated in Figure 3 as a graph of gain/attenuation versus position. Figure 4 provides
the relationship between RF and RI 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/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.
VCC - 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 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.
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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.
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
synchronization.
D - Serial Data Input. The D input is used to input serial data for wiper position changes.
COUT - Serial Cascade Output. The COUT 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 COUT pin.
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, COUT, is provided when controlling multiple devices via one CPU or when reading the wiper
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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DS1800
3-WIRE SERIAL INTERFACE CONTROL
CPU control of the DS1800 is accomplished using the 3-wire serial port of the device. This interface
drives an internal control logic unit. Direct wiper positioning is accomplished by using this port which
consist of three input signals: RST , CLK, and D.
The RST control signal is used to enable 3-wire serial port write operations. The CLK terminal is an input
that provides synchronization for data I/O. Data is input bit by bit via the D input signal pin.
The 3-wire serial timing diagrams are provided in Figure 5. Serial port operation or activity begins with
the transition of the RST signal from a low state to a high state. Once activated, data is clocked into the
part on the low to high transition of the CLK signal input. Data input via the D terminal is transferred in
order of the desired potentiometer-0 wiper value, followed by the potentiometer-1 wiper position value.
Two 8-bit values are used to store wiper position for each potentiometer during powered conditions.
These 8-bit values are written to a 16-bit I/O shift register. A detailed diagram of the 16-bit I/O shift
register is shown in Figure 6.
Bits 0 through 7 are reserved for the positioning of wiper-0 while bits 8 through 15 are reserved for
control of wiper-1. Bits 0 through 6 are used for actual wiper positioning of potentiometer-0. Bit 7 is used
to mute potentiometer-0. If this bit is set to a 1, the potentiometer-0 wiper will be connected to the OUT0
end of the resistor array regardless of the settings of bits 0 through 6.
Bits 8 through 15 are used for positioning the wiper of potentiometer-1. Bits 8 through 14 control wiper
position on the resistor array. Bit 15 is used for muting potentiometer-1. Bit 15, like bit 7, when set to 1
will mute potentiometer 1, regardless of the settings of bits 8 through 14.
Data is transmitted LSB first starting with bit 0. A complete transmission of 16 bits of data is required to
insure proper setting of each potentiometer’s wiper. An incomplete transmission may result in undesired
wiper settings.
Once the 16 bits of information has been transmitted and the RST signal input transitions to a low state,
the new wiper positions are loaded into the part.
PUSHBUTTON INTERFACE CONTROL
The DS1800 can be configured to operate from contact closure or pushbutton inputs. The pushbutton
inputs consist of signals P0A, P0G, P1A, P1G and MUTE. P0A and P0G allow attenuation and gain
control of the input signal to potentiometer-0, while P1A and P1G provide the same control for
potentiometer-1. The MUTE input provides a toggle control for muting the potentiometers via
pushbutton.
The P0A and P1A control inputs, based on the recommended circuit configuration, are used to attenuate
the incoming signal by moving the wiper position towards the OUTx terminals. The P0G and P1G control
inputs provide the opposite function; positioning the wiper(s) closer to the INx terminals, thus providing
gain.
Each of these control inputs is internally pulled up via a 50 kΩ=resistance. Additionally, these inputs
require no external components for debouncing or timing which are provided internal to the part.
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DS1800
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. A single pulse input
over the PxA or PxG input terminals will cause the wiper to move one position. A transition from high to
low on these inputs is considered the beginning of pulse activity or contact closure. The DS1800 has two
timing modes for controlling the speed at which pushbuttons will operate. These modes are termed fast
mode operation and slow mode operation.
In slow mode operation, a single pulse is defined as being greater than 1 ms but lasting no longer than 0.8
seconds. Correspondingly, in fast mode operation, a single pulse is defined as being greater than 50 µs
but lasting no longer than 0.8 second.
Repetitive pulsed inputs can be used to step through each resistive position of the device in a relatively
fast manner. The timing requirements for repetitive pulsed inputs is that pulses must be separated by a
minimum time of 1 ms for slow mode operation and 50 µs for fast mode operation.
Pulse inputs lasting longer than 0.8 seconds will cause the wiper to move one position every 25 ms
seconds after the initial 0.8 second hold time. This is true regardless of the mode input. The total time
required to transcend the entire potentiometer using a continuous input pulse is given by the following
formula:
0.8(seconds) + 127 x 25 ms = 3.975(seconds)
SLOW MODE AND FAST MODE OPERATION
Pushbutton operation, as mentioned, can be operated at two distinct speeds or modes; fast and slow. The
mode or speed of pushbutton debounce is determined at device power-up by the state of the MODE pin.
When MODE powers to a high state, pushbutton debounce timing will operate at the slow mode rate.
When powered and in the low state, debounce timing operates at the fast rate. Timing specifications for
pushbutton operation can be found in the AC Electrical Specification Table for pushbutton operation.
Timing diagrams for pushbutton operation can be found in Figure 7.
ZERO CROSSING DETECTION
The DS1800 provides a zero-crossing detection capability when using the 3-Wire serial interface. Zerocrossing detection provides a means for minimizing unwanted audible noise that may result from sizable
discrete wiper transitions when using the part in audio applications. The zero-crossing detect feature
allows independent wiper changes only when the two terminals of the potentiometer(s) have equal
potentials and within a 50 ms time window from the fall of the RST signal. If at 50 ms the DS1800 has
not detected a zero-crossing, the wiper position of the potentiometer(s) will change regardless of the state
of the input signal. Zero-crossing detection is activated when the ZCEN input is in a low-state. When high,
the ZCEN input deactivates both the 50 ms time requirement and zero-crossing detection.
Zero-crossing detection is also available when using the part in pushbutton operation. When a pushbutton
is activated, the part will change wiper position during the first detected zero-crossing or at the end of a
50 ms time window.
When operating in pushbutton operation with a continuous input pulse, the wiper position will change
once during the initial 0.8-second time period. This change is dictated by a detected zero-crossing or 50
ms time window. Subsequent changes when operating with a continuous input pulse occur on 25 ms time
intervals and are dependent on zero-crossings or 50 ms time-outs.
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DS1800
MUTE CONTROL
The DS1800 provides a mute control feature which can be accessed by the user through hardware or
software. Hardware control of the device is achieved through the MUTE input pin. This pin is internally
pulled up through a 50 kΩ resistor and functions like the PxG and PxA pushbutton controls. When this
input is driven low, the wiper outputs of both potentiometers will be internally connected to the OUTx
terminal of their respective potentiometers. This input performs as a toggle input, with the first activity
on this pin connecting the wiper terminals to the OUTx terminals (position 128) of the potentiometer.
The next input activity on this pin will return the wiper position to the previous state before muting
occurred.
Also, if operating in pushbutton mode, MUTE will be deactivated if an input is received over any push–
button input. This input, like the pushbutton 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. If these bits have value 1, the wiper positions of the pot will be transferred
to the mute position. Unlike hardware mute control, software muting allows the user individual control of
each potentiometer. Additionally, the software mute requires that the complete wiper position setting be
rewritten to establish a non-muted position. Note that bits 7 and 15 of the I/O shift register must have
value 0 to release the software mute position.
CASCADE OPERATION
A feature of the DS1800 is the ability to control multiple devices from a single processor. Multiple
DS1800’s can be linked or daisy-chained as shown in Figure 8. As a data bit is entered into the I/O shift
register of the DS1800, a data bit will appear at the COUT output after a maximum delay of 50
nanoseconds.
The COUT output of the DS1800 can be used to drive the D input of another DS1800. When connecting
multiple devices, the total number of bits sent is always 16 times the number of DS1800’s is the daisy
chain.
An optional feedback resistor can be placed between the COUT terminal of the last device and the D input
of the first DS1800, thus allowing the controlling processor to circularly clock data through the daisy
chain. The value of the feedback or isolation resistor should be in the range from 2 kΩ=to 20 kΩ.
When reading data via the COUT pin and the isolation resistor, the D input is left floating by the reading
device. When RST is driven high, bit 0 is present on the COUT pin, which is fed back to the D pin through
the isolation resistor. When the CLK input transitions low to high, bit 0 is loaded into the first position of
the I/O shift register and bit 1 becomes present on COUT and D of the next device. After 16 bits (or 16
times the number of DS1800s in the daisy chain), the data has shifted completely around and back to its
original position. When RST transitions to the low state to end data transfer, the value (the same as before
the read occurred is loaded into the wiper–0 and wiper–1 registers.
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DS1800
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
-1.0V to +7.0V
-40° to +85°C
-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. Exposure to absolute
maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS
PARAMETER
SYMBOL
MIN
Supply Voltage
VCC
Input Logic 1
Input Logic 0
MAX
UNITS
NOTES
2.7
5.5
V
1
VIH
2.0
VCC+0.5
V
1,2
VIL
-0.5
+0.8
V
1,2
Analog Ground
AGND
GND-0.5
GND+0.5
V
14
Resistor Inputs
L,H,W
GND-0.5
GND+0.5
V
1
DC ELECTRICAL CHARACTERISTICS
PARAMETER
SYMBOL
Supply Current
ICC
Input Leakage
ILI
Wiper Resistance
RW
Wiper Current
IW
Logic 1 Output Current @2.4V
IOH
Logic 0 Output Current @0.4V
IOL
Standby Current:
3 Volts
(-40°C to +85°C; VCC=2.7V to 5.5V)
MIN
TYP
-1
400
MAX
UNITS
NOTES
2000
µA
10
+1
µA
1000
Ω
1
mA
-1
ISTBY
mA
12
5 Volts
Power-Up Time
TYP
(-40°C to +85°C)
tPU
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4
mA
40
µA
20
µA
50
ms
12
8
DS1800
ANALOG RESISTOR CHARACTERISTICS
PARAMETER
SYMBOL
MIN
Total Resistance
(-40°C to +85°C; VCC=2.7V to 5.5V)
TYP
MAX
53
UNITS
NOTES
KΩ
End-to-End Resistor
Tolerance
-20
+20
%
15
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
750
ppm/°C
0.002
%
13
2.2
µVrms
13
-90
dB
13
-100
dB
13
-100
dB
-3 dB Cutoff Frequency
fCUTOFF
Temperature Coefficient
Total Harmonic Distortion
(VIN=1Vrms, 20 Hz to 20
kHz, Tap=0 dB)
THD
Output Noise (20 Hz to 20
kHz, Grounded Input, Tap=0
dB)
Digital Feedthrough
(20 Hz to 20 kHz, Tap=0 dB)
Interchannel Isolation (1
kHz, Tap=0 dB)
Mute Control Active
MUTE
CAPACITANCE
PARAMETER
Input Capacitance
Output Capacitance
(-40°C to +85°C; VCC=2.7V to 5.5V)
SYMBOL
MIN
MAX
UNITS
CIN
5
pF
COUT
7
pF
8 of 14
TYP
NOTES
DS1800
AC ELECTRICAL CHARACTERISTICS
PARAMETER
(-40°C to +85°C; VCC=2.7V to 5.5V)
SYMBOL
MIN
CLK Frequency
fCLK
DC
Width of CLK Pulse
tCH
50
ns
Data Setup Time
tDC
30
ns
Data Hold Time
tCDH
10
ns
Propagation Delay Time
Low to High Level
High to Low Level
tPLH
RST High
tCC
50
ns
tHLT
50
ns
to Clock Input High
RST Low to
Clock Input High
CLK Rise Time
RST
Inactive
TYP
MHz
200
SYMBOL
ns
ns
(-40°C to +85°C; VCC=2.7V to 5.5V)
MIN
TYP
MAX
UNITS
tCPW
NOTES
3,5,11
1
50
800
ms
µs
tHPW
tCCP
NOTES
ns
AC ELECTRICAL CHARACTERISTICS
PUSHBUTTON INPUTS
Continuous Input Pulse
10
50
tBLT
Single Pulse Input
Slow Mode
Fast Mode
Repetitive Input Pulse High Time
Slow Mode
Fast Mode
UNITS
50
tCB
PARAMETER
MAX
3,5,11
1
50
0.8
800
DC
ms
µs
s
3,5,11
NOTES:
1. All voltages are referenced to ground.
2. Valid for VCC = 5V only.
3. Both PxA and PxG inputs are internally pulled up with a 50KΩ resistance.
4. Capacitance values apply at 25°C.
5. Input pulse width is the minimum time required for an input to cause an increment or decrement of
wiper position. If the PxA or PxG inputs are held active for longer than 0.8 seconds, subsequent
increments or decrements will occur at intervals of 25 ms. Timing tolerances for pushbutton control
are specified at 35%.
6. Inter–Channel Matching is used to determine the relative voltage difference in dB between the same
position on each potentiometer. The DS1800 is specified for ±0.25 dB inter-channel matching from
position 0 to position 112 (+20 dB to –27 dB) and ±0.5 dB from position 113 to position 127.
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DS1800
7. Tap–to–Tap tolerance is used to determine the change in voltage between successive tap positions.
The DS1800 is specified for ±0.5 dB tap–to–tap tolerance. From position 0 to position 112 (+20 dB to
–27 dB). From position 113 to position 127, the DS1800 is specified for ±1 dB tap–to–tap tolerance.
8. Power–up time is the time for all pushbutton 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. Maximum current specifications are based on clock rate, active zero–crossing detection, and push–
button activation.
11. Valid for VCC =3V or 5V.
12. Standby current levels apply when all inputs are driven to appropriate supply levels.
13. These parameters are characterized and not 100% tested.
14. See Figure 9.
15. Valid at 25°C only.
DS1800 BLOCK DIAGRAM Figure 1
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DS1800
RECOMMENDED CIRCUIT CONFIGURATION Figure 2
VO /VI GAIN/ATTENUATION VS. POSITION RELATIONSHIP Figure 3
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DS1800
RF/RI RELATIONSHIP VS. POSITION Figure 4
3–WIRE SERIAL TIMING DIAGRAM Figure 5
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DS1800
16–BIT I/O SHIFT REGISTER Figure 6
CONTACT CLOSURE TIMING DIAGRAMS Figure 7
CASCADING OPERATION Figure 8
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DS1800
DIGITAL OUTPUT LOAD Figure 9
INTERNAL GROUND CONNECTIONS Figure 10
NOTE:
GND and AGND must be tied to the same voltage level.
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