Datasheet MC145482DW, MC145482SD Datasheet (Motorola)

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The MC145482 is a 13–bit linear PCM Codec–Filter with 2s complement data
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1
format, and is offered in 20–pin SOG and SSOP packages. This device performs the voice digitization and reconstruction as well as the band limiting and smoothing required for the voice coding in digital communication systems. This device is designed to operate in both synchronous and asynchronous applications and contains an on–chip precision reference voltage.
This device has an input operational amplifier whose output is the input to the encoder section. The encoder section immediately low–pass filters the analog signal with an active R–C filter to eliminate very high frequency noise from being modulated down to the passband by the switched capacitor filter. From the active R–C filter, the analog signal is converted to a dif ferential signal. From this
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ORDERING INFORMATION
MC145482DW SOG Package MC145482SD SSOP
After the differential converter, a differential switched capacitor filter band– passes the analog signal from 200 Hz to 3400 Hz before the signal is digitized by the differential 13–bit linear A/D converter. The digital output is 2s complement format.
The decoder digital input accepts 2s complement data and reconstructs it using a differential 13–bit linear D/A converter. The output of the D/A is low–pass filtered at 3400 Hz and sinX/X compensated by a differential switched capacitor filter. The signal is then filtered by an active R–C filter to eliminate the out–of–band energy of the switched capacitor filter.
The MC145482 PCM Codec–Filter has a high impedance VAG reference pin which allows for decoupling of the internal circuitry that generates the
PIN ASSIGNMENT
RO–
PI
PO– PO+ 5
V
DD
FSR
DR
PDI
1 2 3 4
6 7 8 9 10
VAG Ref
BCLKR
mid–supply VAG reference voltage to the VSS power supply ground. This reduces clock noise on the analog circuitry when external analog signals are referenced to the power supply ground.
The MC145482 13–bit linear PCM Codec–Filter accepts both Short Frame Sync and Long Frame Sync clock formats, and utilizes CMOS due to its reliable low–power performance and proven capability for complex analog/digital VLSI functions.
Single 5 V Power Supply
13–Bit Linear ADC/DAC Conversions with 2s Complement Data Format
Typical Power Dissipation of 25 mW, Power–Down of 0.01 mW
Fully–Differential Analog Circuit Design for Lowest Noise
Transmit Band–Pass and Receive Low–Pass Filters On–Chip
Transmit High–Pass Filter May be Bypassed by Pin Selection
Active R–C Pre–Filtering and Post–Filtering
On–Chip Precision Reference Voltage of 1.575 V for a 0 dBm TLP
@ 600
Full–Duplex Sample Rates from 7 k to 16 k Samples/s
3–Terminal Input Op Amp Can be Used, or a 2–Channel Input Multiplexer
Receive Gain Control from 0 dB to – 21 dB in 3 dB Steps in Synchronous
Operation
Push–Pull 300 Power Drivers with External Gain Adjust
This document contains information on a product under development. Motorola reserves the right to change or discontinue this product without notice.
REV 0 3/97 TN97032700
DW SUFFIX
SOG PACKAGE
CASE 751D
SD SUFFIX
SSOP
CASE 940C
20 19 18 17 16 15
14 13 12
11
V
AG
TI+ TI–
TG HB
V
SS
FST DT BCLKT MCLK
Motorola, Inc. 1997
MC145482MOTOROLA
1
RO–
RECEIVE
SHIFT
FREQ
PI
DAC
REGISTER
DR
– 1
– +
V
DD
R*
1
R*
V
SS
FREQ
PO–
PO+
V
DD
V
SS
VAG Ref
V
AG
TG
TI– TI+
HB
– +
Figure 1. MC145482 13–Bit Linear PCM Codec–Filter Block Diagram
DEVICE DESCRIPTION
A PCM Codec–Filter is used for digitizing and reconstruct­ing the human voice. These devices are used primarily for the telephone network to facilitate voice switching and trans­mission. Once the voice is digitized, it may be switched by digital switching methods or transmitted long distance (T1, microwave, satellites, etc.) without degradation. The name codec is an acronym from ‘‘COder’’ for the analog–to–digital converter (ADC) used to digitize voice, and ‘‘DECoder’’ for the digital–to–analog converter (DAC) used for reconstruct­ing voice. A codec is a single device that does both the ADC and DAC conversions.
To digitize intelligible voice requires a signal–to–distortion ratio of about 30 dB over a dynamic range of about 40 dB. This may be accomplished with a linear 13–bit ADC and DAC. The MC145482 satisfies these requirements and may be used as the analog front–end for voice coders using DSP technology to further compress the digital data stream.
In a sampling environment, Nyquist theory says that to properly sample a continuous signal, it must be sampled at a frequency higher than twice the signal’s highest frequency component. Voice contains spectral energy above 3 kHz, but
FSR
SHARED
DAC
SEQUENCE
AND
CONTROL
1.575 V REF
ADC
TRANSMIT
SHIFT
REGISTER
BCLKR
PDI
MCLK
BCLKT
FST
DT
its absence is not detrimental to intelligibility. To reduce the digital data rate, which is proportional to the sampling rate, a sample rate of 8 kHz was adopted, consistent with a band­width of 3 kHz. This sampling requires a low–pass filter to limit the high frequency energy above 3 kHz from distorting the in–band signal. The telephone line is also subject to 50/60 Hz power line coupling, which must be attenuated from the signal by a high–pass filter before the analog–to– digital converter. The MC145482 includes a high–pass filter for compatibility with existing telephone applications, but it may be removed from the analog input signal path by the high–pass bypass pin.
The digital–to–analog conversion process reconstructs a staircase version of the desired in–band signal, which has spectral images of the in–band signal modulated about the sample frequency and its harmonics. These spectral images are called aliasing components, which need to be attenuated to obtain the desired signal. The low–pass filter used to at­tenuate these aliasing components is typically called a re­construction or smoothing filter.
The MC145482 PCM Codec–Filter has the codec, both presampling and reconstruction filters, and a precision volt­age reference on–chip.
MC145482 MOTOROLA 2
PIN DESCRIPTIONS
POWER SUPPLY V
DD
Positive Power Supply (Pin 6)
This is the most positive power supply and is typically con-
nected to + 5 V. This pin should be decoupled to VSS with a
0.1 µF ceramic capacitor.
V
SS
Negative Power Supply (Pin 15)
This is the most negative power supply and is typically
connected to 0 V.
V
AG
Analog Ground Output (Pin 20)
This output pin provides a mid–supply analog ground. This pin should be decoupled to VSS with a 0.01 µF ceramic ca­pacitor. All analog signal processing within this device is ref­erenced to this pin. If the audio signals to be processed are referenced to VSS, then special precautions must be utilized to avoid noise between VSS and the VAG pin. Refer to the ap­plications information in this document for more information. The VAG pin becomes high impedance when this device is in the powered–down mode.
VAG Ref Analog Ground Reference Bypass (Pin 1)
This pin is used to capacitively bypass the on–chip circuit­ry that generates the mid–supply voltage for the VAG output pin. This pin should be bypassed to VSS with a 0.1 µF ceram­ic capacitor using short, low inductance traces. The VAG Ref pin is only used for generating the reference voltage for the VAG pin. Nothing is to be connected to this pin in addition to the bypass capacitor. All analog signal processing within this device is referenced to the VAG pin. If the audio signals to be processed are referenced to VSS, then special precautions must be utilized to avoid noise between VSS and the VAG pin. Refer to the applications information in this document for more information. When this device is in the powered–down mode, the VAG Ref pin is pulled to the VDD power supply with a non–linear, high–impedance circuit.
CONTROL HB
Transmit High–Pass Filter Bypass (Pin 16)
This pin selects whether the transmit high–pass filter will be used or bypassed, which allows frequencies below 200 Hz to appear at the input of the ADC to be digitized. This high–pass filter is a third order filter for attenuating power line frequencies, typically 50/60 Hz. A logic low selects this filter. A logic high deselects or bypasses this filter. When the filter is bypassed, the transmit frequency response extends down to dc.
when a logic 1 is applied to this pin. The device goes through a power–up sequence when this pin is taken to a logic 1 state, which prevents the DT PCM output from going low im­pedance for at least two FST cycles. The VAG and VAG Ref circuits and the signal processing filters must settle out be­fore the DT PCM output or the RO– receive analog output will represent a valid analog signal.
ANALOG INTERFACE TI+
Transmit Analog Input (Non–Inverting) (Pin 19)
This is the non–inverting input of the transmit input gain setting operational amplifier . This pin accommodates a differ­ential to single–ended circuit for the input gain setting op amp. This allows input signals that are referenced to the V pin to be level shifted to the VAG pin with minimum noise. This pin may be connected to the VAG pin for an inverting amplifier configuration if the input signal is already refer­enced to the VAG pin. The common mode range of the TI+ and TI– pins is from 1.2 V , to VDD minus 1.2 V . This is an FET gate input.
The TI+ pin also serves as a digital input control for the transmit input multiplexer . Connecting the TI+ pin to VDD will place this amplifier’s output (TG) into a high–impedance state, and selects the TG pin to serve as a high–impedance input to the transmit filter. Connecting the TI+ pin to VSS will also place this amplifier’s output (TG) into a high–impedance state, and selects the TI– pin to serve as a high–impedance input to the transmit filter.
TI– Transmit Analog Input (Inverting) (Pin 18)
This is the inverting input of the transmit gain setting op­erational amplifier. Gain setting resistors are usually con­nected from this pin to TG and from this pin to the analog signal source. The common mode range of the TI+ and TI– pins is from 1.2 V to VDD – 1.2 V. This is an FET gate input.
The TI– pin also serves as one of the transmit input mulit­plexer pins when the TI+ pin is connected to VSS. When TI+ is connected to VDD, this pin is ignored. See the pin descrip­tions for the TI+ and the TG pins for more information.
TG Transmit Gain (Pin 17)
This is the output of the transmit gain setting operational amplifier and the input to the transmit band–pass filter. This op amp is capable of driving a 2 k load. Connecting the TI+ pin to VDD will place the TG pin into a high–impedance state, and selects the TG pin to serve as a high–impedance input to the transmit filter. All signals at this pin are referenced to the VAG pin. When TI+ is connected to VSS, this pin is ignored. See the pin descriptions for TI+ and TI– pins for more in­formation. This pin is high impedance when the device is in the powered–down mode.
SS
PDI Power–Down Input (Pin 10)
This pin puts the device into a low power dissipation mode when a logic 0 is applied. When this device is powered down, all of the clocks are gated off and all bias currents are turned off, which causes RO–, PO–, PO+, TG, VAG, and DT to be­come high impedance. The device will operate normally
RO– Receive Analog Output (Inverting) (Pin 2)
This is the inverting output of the receive smoothing filter from the digital–to–analog converter. This output is capable of driving a 2 k load to 1.575 V peak referenced to the V pin. If the device is operated half–channel with the FST pin clocking and FSR pin held low, the receive filter input will be
AG
MC145482MOTOROLA
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connected to the VAG voltage. This minimizes transients at the RO– pin when full–channel operation is resumed by clocking the FSR pin. This pin is high impedance when the device is in the powered–down mode.
PI Power Amplifier Input (Pin 3)
This is the inverting input to the PO– amplifier. The non– inverting input to the PO– amplifier is internally tied to the VAG pin. The PI and PO – pins are used with external resis­tors in an inverting op amp gain circuit to set the gain of the PO+ and PO– push–pull power amplifier outputs. Connect­ing PI to VDD will power down the power driver amplifiers and the PO+ and PO– outputs will be high impedance.
PO– Power Amplifier Output (Inverting) (Pin 4)
This is the inverting power amplifier output, which is used to provide a feedback signal to the PI pin to set the gain of the push–pull power amplifier outputs. This pin is capable of driving a 300 load to PO+. The PO+ and PO– outputs are differential (push–pull) and capable of driving a 300 load to
3.15 V peak, which is 6.3 V peak–to–peak. The bias voltage and signal reference of this output is the VAG pin. The V pin cannot source or sink as much current as this pin, and therefore low impedance loads must be between PO+ and PO–. The PO+ and PO– differential drivers are also capable of driving a 100 resistive load or a 100 nF Piezoelectric transducer in series with a 20 resister with a smalll in­crease in distortion. These drivers may be used to drive re­sistive loads of 32 when the gain of PO– is set to 1/4 or less. Connecting PI to VDD will power down the power driver amplifiers, and the PO+ and PO– outputs will be high imped­ance. This pin is also high impedance when the device is powered down by the PDI
PO+ Power Amplifier Output (Non–Inverting) (Pin 5)
This is the non–inverting power amplifier output, which is an inverted version of the signal at PO–. This pin is capable of driving a 300 load to PO–. Connecting PI to VDD will power down the power driver amplifiers and the PO+ and PO– outputs will be high impedance. This pin is also high im­pedance when the device is powered down by the PDI See PI and PO– for more information.
DIGITAL INTERFACE MCLK
Master Clock (Pin 11)
This is the master clock input pin. The clock signal applied to this pin is used to generate the internal 256 kHz clock and sequencing signals for the switched–capacitor filters, ADC, and DAC. The internal prescaler logic compares the clock on this pin to the clock at FST (8 kHz) and will automatically accept 256, 512, 1536, 1544, 2048, 2560, or 4096 kHz. For MCLK frequencies of 256 and 512 kHz, MCLK must be syn-
pin.
AG
pin.
chronous and approximately rising edge aligned to FST. For optimum performance at frequencies of 1.536 MHz and higher, MCLK should be synchronous and approximately ris­ing edge aligned to the rising edge of FST. In many ap­plications, MCLK may be tied to the BCLKT pin.
FST Frame Sync, Transmit (Pin 14)
This pin accepts an 8 kHz clock that synchronizes the out­put of the serial PCM data at the DT pin. This input is com­patible with both Long Frame Sync and Short Frame Sync. If both FST and FSR are held low for several 8 kHz frames, the device will power down. FST must be clocking for the device to power up affter being powered down by the frame syncs.
BCLKT Bit Clock, Transmit (Pin 12)
This pin controls the transfer rate of transmit PCM data. In the synchronous modes of sign–bit extended and receive gain adjust, the BCLKT also controls the transfer rate of the receive PCM data. This pin can accept any bit clock frequen­cy from 256 to 4096 kHz for Long Frame Sync and Short Frame Sync timing.
DT Data, Transmit (Pin 13)
This pin is controlled by FST and BCLKT and is high im­pedance except when outputting PCM data. This pin is high impedance when the device is in the powered–down mode.
FSR Frame Sync, Receive (Pin 7)
This pin accepts an 8 kHz clock, which synchronizes the input of the serial PCM data at the DR pin. FSR can be asynchronous to FST in the Long Frame Sync or Short Frame Sync modes.
BCLKR Bit Clock, Receive (Pin 9)
This pin accepts any bit clock frequency from 256 to 4096 kHz. The BCLKR pin is also used as a mode select pin when not being clocked for several 8 kHz frames. The BCKLT pin is used to clock the receive PCM data transfers when the BCLKR pin is not being clocked. When the BCLKR pinis a logic 0, the sign–bit extended synchronous mode is selected, which uses 16–bit transfers with the first four bits being the sign bit. When the BCLKR pin is a logic 1, the receive gain adjust synchronous mode is selected, which uses a 13–bit transfer for the transmit PCM data, but uses a 16–bit transfer for the receive side, with the 13–bit voice data being first, fol­lowed by three bits which control the attenuation of the re­ceive analog output.
DR Data, Receive (Pin 8)
This pin is the PCM data input. See the pin descriptions for FSR, BCLKR, and BCKLT for more information.
MC145482 MOTOROLA 4
FUNCTIONAL DESCRIPTION
ANALOG INTERFACE AND SIGNAL PATH
The transmit portion of this device includes a low–noise, three–terminal op amp capable of driving a 2 k load. This op amp has inputs of TI+ (Pin 19) and TI– (Pin 18) and its output is TG (Pin 17). This op amp is intended to be confi­gured in an inverting gain circuit. The analog signal may be applied directly to the TG pin if this transmit op amp is inde­pendently powered down by connecting the TI+ input to the VDD power supply. The TG pin becomes high impedance when the transmit op amp is powered down. The TG pin is internally connected to a 3–pole anti–aliasing pre–filter. This pre–filter incorporates a 2–pole Butterworth active low–pass filter, followed by a single passive pole. This pre–filter is fol­lowed by a single–ended to differential converter that is clocked at 512 kHz. All subsequent analog processing uti­lizes fully–differential circuitry. The next section is a fully–dif­ferential, 5–pole switched–capacitor low–pass filter with a
3.4 kHz frequency cutoff. After this filter is a 3–pole switched–capacitor high–pass filter having a cutoff fre­quency of about 200 Hz. This high–pass stage has a trans­mission zero at dc that eliminates any dc coming from the analog input or from accumulated op amp offsets in the pre­ceding filter stages. The high–pass filter may be bypassed or removed from the signal path by the HB pin. When the high– pass filter is bypassed, the frequency response extends down to include dc. The last stage of the high–pass filter is an autozeroed sample and hold amplifier.
One bandgap voltage reference generator and digital–to– analog converter (DAC) are shared by the transmit and re­ceive sections. The autozeroed, switched–capacitor bandgap reference generates precise positive and negative reference voltages that are virtually independent of tempera­ture and power supply voltage. A capacitor array (CDAC) is combined with a resistor string (RDAC) to implement the 13–bit linear DAC structure. The encode process uses the DAC, the voltage reference, and a frame–by–frame auto­zeroed comparator to implement a successive approxima­tion conversion algorithm. All of the analog circuitry involved in the data conversion (the voltage reference, RDAC, CDAC, and comparator) are implemented with a differential architec­ture.
The receive section includes the DAC described above, a sample and hold amplifier, a 5–pole, 3400 Hz switched ca­pacitor low–pass filter with sinX/X correction, and a 2–pole active smoothing filter to reduce the spectral components of the switched capacitor filter. The output of the smoothing fil­ter is buffered by an amplifier , which is output at the RO– pin. This output is capable of driving a 2 k load to the VAG pin. The MC145482 also has a pair of power amplifiers that are connected in a push–pull configuration. The PI pin is the in­verting input to the PO– power amplifier. The non–inverting input is internally tied to the VAG pin. This allows this amplifier to be used in an inverting gain circuit with two external resis­tors. The PO+ a mplifier has a gain of minus one, and is in­ternally connected to the PO– output. This complete power amplifier circuit is a differential (push–pull) amplifier with ad­justable gain. The power amplifier may be powered down in­dependently of the rest of the chip by connecting the PI pin to VDD.
The calibration level for both ADC and DAC of this 13–bit linear PCM Codec–Filter is referenced to Mu–Law with the
same bit voltage weighting about the zero crossing. This re­sults in the 0 dBm0 calibration level being 3.20 dB below the peak sinusoidal level before clipping. Based on the reference voltage of 1.575 V, the calibration level is 0.775 Vrms or 0 dBm at 600 .
The MC145482 has the ability to attenuate the receive analog output when used in the receive gain adjust mode. This mode is accessed by applying a logic high to the BCLKR pin while the rest of the clock pins are clocked nor­mally. This allows three additional bits that will be used to control the gain of the analog output to be clocked into the DR pin following the 13 bits of voice data. Table 1 shows the attenuation values and the corresponding digital codes.
T able 1. Receive Gain Adjust Mode
Coefficients and Attenuation Weightings
Coefficient Attenuation in dB
000 0 001 – 3 010 – 6 011 – 9 100 – 12 101 – 15 110 – 18 111 – 21
POWER–DOWN
There are two methods of putting this device into a low power consumption mode, which makes the device nonfunc­tional and consumes virtually no power. PDI
is the power– down input pin which, when taken low, powers down the device. Another way to power the device down is to hold both the FST and FSR pins low while the BCLKT and MCLK pins are clocked. When the chip is powered down, the VAG, TG, RO–, PO+, PO–, and DT outputs are high impedance and the VAG Ref pin is pulled to the VDD power supply with a non– linear, high–impedance circuit. To return the chip to the pow­er–up state, PDI
must be high and the FST frame sync pulse must be present while the BCLKT and MCLK pins are clocked. The DT output will remain in a high–impedance state for at least two 8 kHz FST pulses after power–up.
MASTER CLOCK
Since this codec–filter design has a single DAC architec­ture, the MCLK pin is used as the master clock for all analog signal processing including analog–to–digital conversion, digital–to–analog conversion, and for transmit and receive fil­tering functions of this device. The clock frequency applied to the MCLK pin may be 256 kHz, 512 kHz, 1.536 MHz,
1.544 MHz, 2.048 MHz, 2.56 MHz, or 4.096 MHz. This de­vice has a prescaler that automatically determines the proper divide ratio to use for the MCLK input, which achieves the re­quired 256 kHz internal sequencing clock. The clocking re­quirements of the MCLK input are independent of the PCM data transfer mode (i.e., Long Frame Sync, Short Frame Sync, whether the device is used in the synchronous modes or not).
MC145482MOTOROLA
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DIGITAL I/O
The MC145482 is a 13–bit linear device using 2s comple­ment data format. Table 2 shows the 13–bit data word format for the maximum positive code and negative zero and full– scale.
Table 3 shows the series of eight 13–bit PCM words that correspond to a digital milliwatt. The digital milliwatt is the 1 kHz calibration signal reconstructed by the DAC that de­fines the absolute gain or 0 dBm0 transmission level point (TLP) of the DAC. The calibration level for this 13–bit linear ADC and DAC is referenced to Mu–Law with the same bit voltage weighting about the zero crossing. This results in the 0 dBm0 calibration level being 3.20 dB below the peak sinu­soidal level before clipping. Refer to Figures 2a–2d for a summary and comparison of the four PCM data interface modes of this device.
T able 2. PCM Codes for Zero and Full–Scale
Level Sign Bit Magnitude Bits
+ Full Scale 0 1111 1111 1111 + One Step 0 0000 0000 0001
Zero 0 0000 0000 0000 – One Step 1 1111 1111 1111 – Full Scale 1 0000 0000 0000
Table 3. PCM Codes for 1 kHz Digital Milliwatt
Level Sign Bit Magnitude Bits
π/8 3π/8 5π/8 7π/8 9π/8
11π/8 13π/8 15π/8
MC145482 MOTOROLA 6
FST (FSR)
BCLKT (BCLKR)
DT
Figure 2a. Long Frame Sync (Transmit and Receive Have Individual Clocking)
FST (FSR)
BCLKT (BCLKR)
DT
Figure 2b. Short Frame Sync (Transmit and Receive Have Individual Clocking)
FST (FSR)
SHORT OR
LONG FRAME
SYNC
910111213
87654321
8 910111213
7654321DR DON’T CAREDON’T CARE
8 910 11 12
8DR
7654321
9
10
11 12
137654321
13
DON’T CAREDON’T CARE
BCLKT
DT
DR DON’T CARE
7654321
8
7654321 16
141312111098
15
1514131211109
Figure 2c. Sign–Extended (BCLKR = 0)
Transmit and receive both use BCLKT, and the first four data bits are the sign bit.
FST may occur at a different time than FSR.
FST (FSR)
SHORT OR
LONG FRAME
SYNC
BCLKT
DT
DR
DON’T CARE
87654321
1387654321
1211109
Figure 2d. Receive Gain Adjust (BCLKR = 1)
Transmit and receive both use BCLKT. FST may occur at a different time than FSR.
Bits 14, 15, and 16, clocked into DR, are used for attenuation control for the receive analog output.
16
161514131211109
DON’T CARE
DON’T CARE
Figure 2. Digital Timing Modes for the PCM Data Interface
MC145482MOTOROLA
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PRINTED CIRCUIT BOARD LAYOUT
CONSIDERATIONS
The MC145482 is manufactured using high–speed CMOS VLSI technology to implement the complex analog signal processing functions of a PCM Codec–Filter. The fully–dif fer­ential analog circuit design techniques used for this device result in superior performance for the switched capacitor fil­ters, the analog–to–digital converter (ADC) and the digital– to–analog converter (DAC). Special attention was given to the design of this device to reduce the sensitivities of noise, including power supply rejection and susceptibility to radio frequency noise. This special attention to design includes a fifth order low–pass filter, followed by a third order high–pass filter whose output is converted to a digital signal with greater than 75 dB of dynamic range, all operating on a single 5 V power supply . This results in an LSB size for small audio sig­nals of about 386 µV. The typical idle channel noise level of this device is less than one LSB. In addition to the dynamic range of the codec–filter function of this device, the input gain–setting op amp has the capability of greater than 35 dB of gain intended for an electret microphone interface.
This device was designed for ease of implementation, but due to the large dynamic range and the noisy nature of the environment for this device (digital switches, radio tele­phones, DSP front–end, etc.) special care must be taken to assure optimum analog transmission performance.
PC BOARD MOUNTING
It is recommended that the device be soldered to the PC board for optimum noise performance. If the device is to be used in a socket, it should be placed in a low parasitic pin inductance (generally , low–profile) socket.
POWER SUPPLY, GROUND, AND NOISE CONSIDERATIONS
This device is intended to be used in switching applica­tions which often require plugging the PC board into a rack with power applied. This is known as ‘‘hot–rack insertion.’’ In these applications care should be taken to limit the voltage on any pin from going positive of the VDD pins, or negative of the VSS pins. One method is to extend the ground and power contacts of the PCB connector. The device has input protec­tion on all pins and may source or sink a limited amount of current without damage. Current limiting may be accom­plished by series resistors between the signal pins and the connector contacts.
The most important considerations for PCB layout deal with noise. This includes noise on the power supply, noise generated by the digital circuitry on the device, and cross coupling digital or radio frequency signals into the audio sig­nals of this device. The best way to prevent noise is to:
1. Keep digital signals as far away from audio signals as possible.
2. Keep radio frequency signals as far away from the audio signals as possible.
3. Use short, low inductance traces for the audio circuitry to reduce inductive, capacitive, and radio frequency noise sensitivities.
4. Use short, low inductance traces for digital and RF circuitry to reduce inductive, capacitive, and radio frequency radiated noise.
5. Bypass capacitors should be connected from the VDD, VAG Ref, and VAG pins to VSS with minimal trace length. Ceramic monolithic capacitors of about 0.1 µF are acceptable for the VDD and VAG Ref pins to decouple the device from its own noise. The VDD capacitor helps supply the instantaneous currents of the digital circuitry in addition to decoupling the noise which may be generated by other sections of the device or other circuitry on the power supply. The VAG Ref decoupling capacitor is effecting a low–pass filter to isolate the mid–supply voltage from the power supply noise gener­ated on–chip, as well as external to the device. The V decoupling capacitor should be about 0.01 µF. This helps to reduce the impedance of the VAG pin to VSS at frequencies above the bandwidth of the VAG generator, which reduces the susceptiblility to RF noise.
6. Use a short, wide, low inductance trace to connect the VSS ground pin to the power supply ground. The VSS pin is the digital ground and the most negative power supply pin for the analog circuitry . All analog signal processing is referenced to the VAG pin, but because digital and RF circuitry will probably be powered by this same ground, care must be taken to minimize high frequency noise in the VSS trace. Depending on the application, a double– sided PCB with a VSS ground plane connecting all of the digital and analog VSS pins together would be a good grounding method. A multilayer PC board with a ground plane connecting all of the digital and analog VSS pins together would be the optimal ground configuration. These methods will result in the lowest resistance and the lowest inductance in the ground circuit. This is important to reduce voltage spikes in the ground circuit resulting from the high speed digital current spikes. The magnitude of digitally induced voltage spikes may be hundreds of times larger than the analog signal the device is required to digitize.
7. Use a short, wide, low inductance trace to connect the VDD power supply pin to the 5 V power supply. Depending on the application, a double–sided PCB with VDD bypass capacitors to the VSS ground plane, as described above, may complete the low impedance coupling for the power supply . For a multilayer PC board with a power plane, connecting all of the VDD pins to the power plane would be the optimal power distribution method. The integrated circuit layout and packaging considerations for the 5 V VDD power circuit are essentially the same as for the VSS ground circuit.
8. T he VAG pin is the reference for all analog signal processing. In some applications the audio signal to be digitized may be referenced to the VSS ground. To reduce the susceptibility to noise at the input of the ADC section, the three–terminal op amp may be used in a differential to single–ended circuit to provide level conversion from the VSS ground to the VAG ground with noise cancellation. The op amp may be used for more than 35 dB of gain in microphone interface circuits, which will require a compact layout with minimum trace lengths as well as isolation from noise sources. It is recom­mended that the layout be as symmetrical as possible to avoid any imbalances which would reduce the noise cancelling benefits of this differential op amp circuit. Refer to the application schematics for examples of this circuitry.
AG
MC145482 MOTOROLA 8
If possible, reference audio signals to the VAG pin instead of to the VSS pin. Handset receivers and tele­phone line interface circuits using transformers may be audio signal referenced completely to the VAG pin. Re-
fer to the application schematics for examples of this circuitry. The VAG pin cannot be used for ESD or line protection.
MC145482MOTOROLA
9
MAXIMUM RATINGS (Voltages Referenced to V
Rating Symbol Value Unit
DC Supply Voltage V Voltage on Any Analog Input or Output Pin VSS – 0.3 to VDD + 0.3 V Voltage on Any Digital Input or Output Pin VSS – 0.3 to VDD + 0.3 V Operating Temperature Range T Storage Temperature Range T
SS
Pin)
DD
A
stg
– 0.5 to 6 V
– 40 to + 85 °C
– 85 to +150 °C
POWER SUPPLY (T
DC Supply Voltage 4.75 5.0 5.25 V Active Current Dissipation (VDD = 5 V) (No Load, PI VDD – 0.5 V)
Power–Down Current (VIH for Logic Levels PDI = V Must be VDD – 0.5 V) FST and FSR = VSS, PDI
DIGITAL LEVELS (V
Input Low Voltage V Input High Voltage V Output Low Voltage (DT Pin, IOL= 2.5 mA) V Output High Voltage (DT Pin, IOH = – 2.5 mA) V Input Low Current (VSS Vin VDD) I Input High Current (VSS Vin VDD) I Output Current in High Impedance State (VSS DT VDD) I Input Capacitance of Digital Pins (Except DT) C Input Capacitance of DT Pin when High–Z C
= – 40 to + 85°C)
A
Characteristics
(No Load, PI VDD – 1.5 V)
= 4.75 to 5.25 V, VSS = 0 V, TA = – 40 to + 85°C)
DD
Characteristics
= V
SS
DD
Min Typ Max Unit
— —
— —
Symbol Min Max Unit
IL
IH
OL
OH
IL IH
OZ
in
out
5.0
5.2
0.001
0.01
0.6 V
2.4 V — 0.4 V
VDD – 0.5 V
– 10 + 10 µA – 10 + 10 µA – 10 + 10 µA
10 pF — 15 pF
— —
— —
mA
mA
MC145482 MOTOROLA 10
ANALOG ELECTRICAL CHARACTERISTICS (V
Characteristics
Input Current TI+, TI– ± 0.1 ± 1.0 µA Input Resistance to VAG (VAG – 0.5 V Vin VAG + 0.5 V) Input Capacitance TI+, TI– 10 pF Input Offset V oltage of TG Op Amp TI+, TI– ± 5 mV Input Common Mode Voltage Range TI+, TI– 1.2 VDD – 1.2 V Input Common Mode Rejection Ratio TI+, TI– TBD dB Gain Bandwidth Product (10 kHz) of TG Op Amp (RL 10 k) 3000 kHz DC Open Loop Gain of TG Op Amp (RL 10 k) 95 dB Equivalent Input Noise (C–Message) Between TI+ and TI– at TG – 30 dBrnC Output Load Capacitance for TG Op Amp 0 100 pF Output Voltage Range for TG (RL = 2 k to VAG) 0.5 VDD – 0.5 V Output Current (0.5 V V Output Load Resistance to V Output Impedance RO– 1 Output Load Capacitance RO– 0 500 pF DC Output Offset Voltage of RO– Referenced to V VAG Output Voltage Referenced to VSS (No Load) VDD/2 – 0.1 VDD/2 VDD/2 + 0.1 V VAG Output Current with ± 25 mV Change in Output Voltage ± 2.0 ± 10 mA Power Supply Rejection Ratio Transmit
(0 to 100 kHz @100 mVrms Applied to VDD, Receive C–Message Weighting, All Analog Signals Referenced to VAG Pin)
Input Current (VAG – 0.5 V PI VAG + 0.5 V) PI ± 0.05 ± 1.0 µA Input Resistance (VAG – 0.5 V PI VAG + 0.5 V) PI 10 M Input Offset Voltage PI ± 20 mV Output Offset Voltage of PO+ Relative to PO– (Inverted Unity Gain for PO–) ± 50 mV Output Current (VSS + 0.7 V PO+ or PO– VDD – 0.7 V) ± 10 mA PO+ or PO– Output Resistance (Inverted Unity Gain for PO–) 1 Gain Bandwidth Product (10 kHz, Open Loop for PO–) 1000 kHz Load Capacitance (PO+ or PO– to VAG, or PO+ to PO–) 0 1000 pF Gain of PO+ Relative to PO– (RL = 300 , + 3 dBm0, 1 kHz) – 0.2 0 + 0.2 dB Total Signal to Distortion at PO+ and PO– with a Differential Load of: 300
Power Supply Rejection Ratio 0 to 4 kHz
(0 to 25 kHz @ 100 mVrms Applied to VDD. 4 to 25 kHz PO– Connected to PI. Differential or Measured Referenced to VAG Pin.)
VDD – 0.5 V) TG, RO– ± 1.0 mA
out
AG
= 4.75 to 5.25 V, VSS = 0 V, TA = – 40 to + 85°C)
DD
Min Typ Max Unit
AG
Power Drivers PI, PO+, PO–
100 nF in series with 20
TI+, TI– 10
TG, RO– 2 k
± 25 mV
TBD TBD
45
100
— —
TBD
TBD TBD
60 40 40
TBD TBD
M
— —
— — —
— —
dBC
dBC
dB
MC145482MOTOROLA
11
ANALOG TRANSMISSION PERFORMANCE
(VDD = 4.75 to 5.25 V, VSS = 0 V, All Analog Signals Referenced to VAG, 0 dBm0 = 0.775 Vrms = 0 dBm @ 600 , FST = FSR = 8 kHz, BCLKT = MCLK = 2.048 MHz Synchronous Operation, TA = – 40 to + 85°C, Unless Otherwise Noted)
A/D D/A
Characteristics
Peak Single Frequency Tone Amplitude without Clipping T Absolute Gain (0 dBm0 @ 1.02 kHz, TA = 25°C, VDD = 5.0 V) – 0.25 + 0.25 – 0.25 + 0.25 dB Absolute Gain Variation with Temperature 0 to + 70°C
– 40 to + 85°C—— Absolute Gain Variation with Power Supply (TA = 25°C) TBD TBD dB Total Distortion, 1.02 kHz Tone (C–Message Weighting)
+ 3 dBm0
0 dBm0 – 10 dBm0 – 20 dBm0 – 30 dBm0
–40 dBm0 –50 dBm0 –60 dBm0
Idle Channel Noise (For End–to–End and A/D, See Note 1)
(C–Message Weighted)
(Psophometric Weighted)
Frequency Response 15 Hz (Relative to 1.02 kHz @ 0 dBm0) (HB = 0) 50 Hz
60 Hz 165 Hz 200 Hz
300 to 3000 Hz
3300 Hz 3400 Hz 3600 Hz 4000 Hz
4600 Hz to 100 kHz
Out–of–Band Spurious at VAG Ref (300 to 3400 Hz @ 0 dBm0 in)
4600 to 7600 Hz 7600 to 8400 Hz
8400 to 100,000 Hz Idle Channel Noise Selective (8 kHz, Input = VAG, 30 Hz Bandwidth) – 70 dBm0 Absolute Delay (1600 Hz) (HB = 0) 315 205 µs Group Delay Referenced to 1600 Hz (HB = 0) 500 to 600 Hz
600 to 800 Hz
800 to 1000 Hz 1000 to 1600 Hz 1600 to 2600 Hz 2600 to 2800 Hz 2800 to 3000 Hz
Crosstalk of 1020 Hz @ 0 dBm0 from A/D or D/A (Note 2) –75 –75 dB
NOTES:
1. Extrapolated from a 1020 Hz @ – 50 dBm0 distortion measurement to correct for encoder enhancement.
2. Selectively measured while stimulated with 2667 Hz @ – 50 dBm0.
Min Typ Max Min Typ Max
max
1.575 1.575 Vpk
— — — — — — — —
— —
— — — —
– 1.0 – 0.20 – 0.35
– 0.9
— — —
— — —
— — — — — — —
TBD TBD——
55 58 58 53 44 34 24 14
— —17– 69
– 40
– 30
– 26
– 3
– 0.4
+ 0.20
+ 0.20
– 3
– 14
– 32
— — —
210
130 — — — — —
145
— — — — — — — —
0
— — —
70 35 70 95
— —
— — — — — — — —
— —
– 0.5 – 0.5 – 0.5 – 0.5
– 0.5 – 0.20 – 0.35
– 0.9
— — —
— — —
– 40 – 40 – 40 – 30
— — —
TBD TBD——
60 60 60 55 46 36 26 16
— —11– 79
— — — — — —
+ 0.20
+ 0.20
– 3
– 14
– 30
– 30
– 40
– 30
— — — — — — —
175
— — — — — — — —
0 0 0 0 0
0
— — — — 85
110
Units
dBC
dBrnc0 dBm0p
dB
dB
dB
µs
MC145482 MOTOROLA 12
DIGITAL SWITCHING CHARACTERISTICS, LONG FRAME SYNC AND SHORT FRAME SYNC
(VDD = 4.75 to 5.25 V, VSS = 0 V, All Digital Signals Referenced to VSS, TA = – 40 to + 85°C, CL = 150 pF, FST = FSR = 8 kHz, Unless Otherwise Noted)
Ref.
No.
1 Master Clock Frequency for MCLK
1 MCLK Duty Cycle for 256 kHz Operation 45 55 % 2 Minimum Pulse Width High for MCLK (Frequencies of 512 kHz or Greater) 50 ns 3 Minimum Pulse Width Low for MCLK (Frequencies of 512 kHz or Greater) 50 ns 4 Rise Time for All Digital Signals 50 ns 5 Fall Time for All Digital Signals 50 ns 6 Setup Time from MCLK Low to FST High 50 ns 7 Setup Time from FST High to MCLK Low 50 ns 8 Bit Clock Data Rate for BCLKT or BCLKR 256 4096 kHz
9 Minimum Pulse Width High for BCLKT or BCLKR 50 ns 10 Minimum Pulse Width Low for BCLKT or BCLKR 50 ns 11 Hold Time from BCLKT (BCLKR) Low to FST (FSR) High 20 ns 12 Setup Time for FST (FSR) High to BCLKT (BCLKR) Low 80 ns 13 Setup Time from DR Valid to BCLKR Low 0 ns 14 Hold Time from BCLKR Low to DR Invalid 50 ns
15 Hold Time from 2nd Period of BCLKT (BCLKR) Low to FST (FSR) Low 50 ns 16 Delay Time from FST or BCLKT, Whichever is Later, to DT for Valid MSB Data 60 ns 17 Delay Time from BCLKT High to DT for Valid Data 60 ns 18 Delay Time from the Later of the 13th (16th for Sign–Extended Mode) BCLKT
Falling Edge, or the Falling Edge of FST to DT Output High Impedance
19 Minimum Pulse Width Low for FST or FSR 50 ns
20 Hold Time from BCLKT (BCLKR) Low to FST (FSR) Low 50 ns 21 Setup Time from FST (FSR) Low to MSB Period of BCLKT (BCLKR) Low 50 ns 22 Delay Time from BCLKT High to DT Data Valid 10 60 ns 23 Delay Time from the 13th (16th for Sign–Extended Mode) BCLKT Low to DT
Output High Impedance
Characteristics Min Typ Max Unit
LONG FRAME SPECIFIC TIMING
SHORT FRAME SPECIFIC TIMING
— — — — — —
10 60 ns
10 60 ns
256
512 1536 1544 2048 2560 4096
— — — — — — —
kHz
MC145482MOTOROLA
13
MCLK
7
6 2
1
3
4
5
8
BCLKT
FST
DT
BCLKR
(BCLKT)
FSR
12345671314
11
16
12
15
16
17
9
10
18
18
12 3 4 5 6 13
8
12345671314
11
12
15
9
10
DR
13
14
123456 13
Figure 3. Long Frame Sync Timing
MC145482 MOTOROLA 14
7
6 2
MCLK
1
3
4
5
BCLKT
FST
DT
BCLKR
12
8
12345671314
20
11
22
21
22
9
10
23
1234 56 13
8
12345671314
11
20
12
21
9
10
FSR
DR
13
14
123456 13
Figure 4. Short Frame Sync Timing
MC145482MOTOROLA
15
AUDIO OUT
+ 5 V
0.1 µF
0.1 µF
– +
0.01
µ
10 k
10 k
F
2X20 k
1 2 3 4 5 6 7 8 9
VAG Ref RO– PI PO– PO+ V
DD
FSR DR BCLKR PDI
V
AG TI+
TI– TG
HB
V
SS
FST
DT
BCLKT
MCLK
20 19 18 17 16 15 14 13 12 11 10
10 k
10 k
Figure 5. MC145482 T est Circuit — Signals Referenced to VAG Pin
1.0 µF
1.0 µF
8 kHz PCM OUT
2.048 MHz
PCM IN
ANALOG IN
Y
AUDIO OUT
RL ≥ 2 k
AUDIO OUT RL ≥ 150
10 k
µ
F
0.1 µF
2X20 k
68
µ
F
+
+ 5 V
0.1 µF
1 2 3 4 5 6 7 8 9
VAG Ref RO– PI PO– PO+ V
DD
FSR DR BCLKR PDI
V
AG TI+
TI– TG
HB
V
SS
FST
DT
BCLKT
MCLK
20 19 18 17 16 15 14 13 12 11 10
10 k
10 k
Figure 6. MC145482 T est Circuit — Signals Referenced to V
0.01
10 k
10 k
1.0 µF
ANALOG IN
1.0 µF
Y
8 kHz PCM OUT
2.048 MHz
PCM IN
SS
MC145482 MOTOROLA 16
SIDETONE
0.1 µF
0.01
+3 V
1 k
68
µ
µ
F
420 pF
F
1 k
REC
+ 5 V
0.1
µ
1
VAG Ref
2
RO–
3
PI
4
PO–
5
PO+
6
V
DD
7
F
8 9
10
FSR DR BCLKR PDI
V
AG TI+
TI– TG
HB
V
SS
FST
DT
BCLKT
MCLK
20 19 18 17 16 15 14 13 12 11
75 k
75 k
420 pF
1 k
1 k
0.1
0.1 µF
µ
F
8 kHz PCM OUT
2.048 MHz
PCM IN
MIC
Figure 7. MC145482 Handset Interface
1.0
µ
F
10 k
R0 = 600
– 48 V
TIP
N = 0.5
N = 0.5
N = 0.5
RING
+ 5 V
0.1
µ
F
0.1 µF
1/4 R0
2X20 k
10
1 2 3 4 5 6 7 8 9
VAG Ref RO– PI PO– PO+ V
DD
FSR DR BCLKR PDI
V
AG TI+
TI– TG
HB
V
SS
FST
DT
BCLKT
MCLK
20 19 18 17 16 15 14 13 12
11
20 k
0.1 µF
8 kHz PCM OUT
2.048 MHz
PCM IN
Figure 8. MC145482 Step–Up Transformer Line Interface
MC145482MOTOROLA
17
P ACKAGE DIMENSIONS
DW SUFFIX
SOG PACKAGE
CASE 751D–04
–A–
20
1
D20X
0.010 (0.25) B
11
S
P10X
0.010 (0.25)
M
M
B
J
–B–
10
M
S
A
T
F
R
X 45
_
C
SEATING
–T–
18X
G
K
PLANE
M
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSIONS A AND B DO NOT INCLUDE MOLD PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.150 (0.006) PER SIDE.
5. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.13 (0.005) TOTAL IN EXCESS OF D DIMENSION AT MAXIMUM MATERIAL CONDITION.
DIM MIN MAX MIN MAX
A 12.65 12.95 0.499 0.510 B 7.40 7.60 0.292 0.299 C 2.35 2.65 0.093 0.104 D 0.35 0.49 0.014 0.019
F 0.50 0.90 0.020 0.035
G 1.27 BSC 0.050 BSC
J 0.25 0.32 0.010 0.012 K 0.10 0.25 0.004 0.009 M 0 7 0 7
__
P 10.05 10.55 0.395 0.415 R 0.25 0.75 0.010 0.029
INCHESMILLIMETERS
__
SD SUFFIX
SSOP
CASE 940C–02
20 11
A
–P–
G
H
B
–R–
101
D
0.120 (0.005) T
M
J
S
P
C
N
0.25 (0.010)
L
F
NOTE 4
0.076 (0.003)
M
M
R
NOTES:
1. CONTROLLING DIMENSION: MILLIMETER.
2. DIMENSIONS AND TOLERANCES PER ANSI Y14.5M, 1982.
3. DIMENSIONS A AND B DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS AND ARE MEASURED AT THE PARTING LINE. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.15MM PER SIDE.
4. DIMENSION IS THE LENGTH OF TERMINAL FOR SOLDERING TO A SUBSTRATE.
5. TERMINAL POSITIONS ARE SHOWN FOR REFERENCE ONLY.
6. THE LEAD WIDTH DIMENSION DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.08MM TOTAL IN EXCESS OF THE LEAD WIDTH DIMENSION.
DIM MIN MAX MIN MAX
A 7.10 7.30 0.280 0.287 B 5.20 5.38 0.205 0.212 C 1.75 1.99 0.069 0.078 D 0.25 0.38 0.010 0.015
M
F 0.65 1.00 0.026 0.039
G 0.65 BSC 0.026 BSC H 0.59 0.75 0.023 0.030 J 0.10 0.20 0.004 0.008 L 7.65 7.90 0.301 0.311 M 0 8 0 8 N 0.05 0.21 0.002 0.008
INCHESMILLIMETERS
____
MC145482 MOTOROLA 18
Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty , representation or guarantee regarding the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. “T ypical” parameters which may be provided in Motorola data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. Motorola does not convey any license under its patent rights nor the rights of others. Motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a situation where personal injury or death may occur. Should Buyer purchase or use Motorola products for any such unintended or unauthorized application, Buyer shall indemnify and hold Motorola and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that Motorola was negligent regarding the design or manufacture of the part. Motorola and are registered trademarks of Motorola, Inc. Motorola, Inc. is an Equal Opportunity/Affirmative Action Employer.
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MC145482/D
MC145482MOTOROLA
19
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