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CALIFORNIA MICRO DEVICES
CM8870/70C
CMOS Integrated DTMF Receiver
Features
* Full DTMF receiver * Less than 35mW power consumption * Industrial temperature range * Uses quartz crystal or ceramic resonators * Adjustable acquisition and release times * 18-pin DIP, 18-pin DIP EIAJ, 18-pin SOIC, 20-pin PLCC * CM8870C -- -- -- Power down mode Inhibit mode Buffered OSC3 output (PLCC package only)
Applications
* PABX * Central office * Mobile radio * Remote control * Remote data entry * Call limiting * Telephone answering systems * Paging systems
* CM8870C is fully compatible with CM8870 for 18-pin devices by grounding pins 5 and 6
Product Description
The CAMD CM8870/70C provides full DTMF receiver capability by integrating both the bandsplit filter and digital decoder functions into a single 18-pin DIP, SOIC, or 20-pin PLCC package. The CM8870/70C is manufactured using state-of-the-art CMOS process technology for low power consumption (35mW, max.) and precise data handling. The filter section uses a switched capacitor technique for both high and low group filters and dial tone rejection. The CM8870/70C decoder uses digital counting techniques for the detection and decoding of all 16 DTMF tone pairs into a 4-bit code. This DTMF receiver minimizes external component count by providing an on-chip differential input amplifier, clock generator, and a latched three-state interface bus. The on-chip clock generator requires only a low cost TV crystal or ceramic resonator as an external component.
(c) 2000 California Micro Devices Corp. All rights reserved. 9/28/2000
+##' Tel: (408) 263-3214 Fax: (408) 263-7846 www.calmicro.com
215 Topaz Street, Milpitas, California 95035
1
CALIFORNIA MICRO DEVICES
Absolute Maximum Ratings: (Note 1)
ABSOLUTE MAXIMUM RATINGS Parameter Power Supply Voltage (VDDV SS) Voltage on any Pin Current on any Pin Operating Temperature Storage Temperature Symbol VDD Vdc ID D TA TS Value 6.0V Max VSS-0.3V to VDD+0.3V 10mA Max -40C to +85C -65C to +150C
CM8870/70C
This device contains input protection against damage due to high static voltages or electric fields; however, precautions should be taken to avoid application of voltages higher than the maximum rating. Notes: 1. Exceeding these ratings may cause permanent damage, functional operation under these conditions is not implied.
DC Characteristics: All voltages referenced to VSS, VDD = 5.0V 5%, TA = -40C to +85C unless otherwise noted.
Parameter Operating Supply Voltage Operating Supply Current Standby Supply Current Power Consumption Low Level Input Voltage High Level Input Voltage Input Leakage Current Pull Up (Source) Current on TOE Input Impedance, (IN+, IN-) Steering Threshold Voltage Low Level Output Voltage High Level Output Voltage Output Low (Sink) Current Output High (Source) Current Output Voltage Output Resistance DC CHARACTE RISTICS Symbol Min Typ V DD I DD I DDQ PO V IL V IH I I H/ L I L I so R IN V Tst V OL V OH I OL I OH V R EF R OR 4.97 1.0 0.4 2.4 10 2.5 0.8 2.7 8 2.2 3.5 0.1 6.5 10 2.5 0.03 20 15 4.75 3.0 Max 5.25 7.0 25 35 1.5 Units V mA A mW V V A A M V V V mA mA V PD =VDD f=3.579 MHz; VDD=5.0V VDD=5.0V VDD=5.0V VIN = VSS = VDD (Note 1) TOE=0V, VDD=5.0V @ 1K H z VDD = 5.0V VDD = 5.0V, No Load VDD = 5.0V, No Load VOUT = 0.4V VOUT = 4.6V VDD = 5.0V, No Load Test Conditions
VREF
Operating Characteristics: All voltages referenced to VSS, VDD = 5.0V 5%, TA = -40C to +85C unless otherwise noted. Gain Setting Amplifier
OPERATING CHARACTERISTICS
Parameter Input Leakage Current Input Resistance Input Offset Voltage Power Supply Rejection Common Mode Rejection D C Open Loop Voltage Gain Open Loop Unity Gain Bandwidth Output Voltage Swing Maximum Capacitive Load (GS) Maximum Resistive Load (GS) Common Mode Range (No Load)
(c)2000 California Micro Devices Corp. All rights reserved.
Symbol IIN R IN V OS PSRR CMR R A V OL fc VO CL RL Vcm
Min 10
Typ
Max 100 25
Units nA M mV dB dB dB MHz VP-P
Test Conditions V S S < V IN < V D D
50 40 32 0.3 4.0 10 0 50 2.5
1KHz (Note 12) -3.0V < VIN < 3.0V
RL 100KW to VSS
pF K VP-P N o L o ad
2
215 Topaz Street, Milpitas, California 95035
Tel: (408) 263-3214
Fax: (408) 263-7846
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9/28/2000
CALIFORNIA MICRO DEVICES
CM8870/70C
AC Characteristics: All voltages referenced to VSS, VDD=5.0V 5%, TA=-40C to +85C, fCLK=3.579545 MHz using test circuit (Fig. 1) unless otherwise noted.
AC CHARACTERISTICS Parameter
Valid Input Signal Levels (each tone of composite signal) Positive Twist Accept Negative Twist Accept Freq. D eviation Accept Limit Freq. D eviation Reject Limit Third Tone Tolerance Noise Tolerance D ial Tone Tolerance Tone Present D etection Time Tone Absent D etection Time Min Tone D uration Accept Max Tone D uration Reject Min. Interdigit Pause Accept Max. Interdigit Pause Reject Propagation D elay (St to Q) Propagation D elay (St to StD ) Output D ata Set Up (Q to StD ) Propagation D elay (TOE to Q) Crystal/Clock Frequency Clock Output (OSC 2) Capacitive L o ad Enable D isable t DP t DA t R EC t R EC t ID t DO t PQ t PSt D t QSt D t PTE t PTD f CL K C LO 3.5759 20 6 9 3.4 50 300 3.5795 3.5831 30 11 16 20 40 5 0.5 3.5% -16 -12 +22 8 3 14 8.5 40
Symbol
Min
-29 27.5
Typ
Max
+1 869 10 10 1.5%2Hz
Units
dBm mVRMS dB dB Nom. Nom. dB dB dB mS mS mS mS mS S S S S nS nS MHz pF
Notes
1,2,3,4,5,8 2,3,4,8 2,3,5,8,10 2,3,5 2,3,4,5,8,9,13,14 2,3,4,5,6,8,9 2,3,4,5,7,8,9 Refer to Timing D iagram (User Adjustable) Times shown are obtained with circuit in Fig. 1)
TOE = VDD
R L = 10 K CL = 50pF
Notes: 1. dBm = decibels above or below a reference power of 1 mW into a 600 ohm load. 2. Digit sequence consists of all 16 DTMF tones. 3. Tone duration = 40mS. Tone pause = 40 mS. 4. Nominal DTMF frequencies are used. 5. Both tones in the composite signal have an equal amplitude. 6. Bandwidth limited (0 to 3 KHz) Gaussian Noise. 7. The precise dial tone frequencies are (350 Hz and 440 Hz) 2%. 8. For an error rate of better than 1 in 10,000
9. 10. 11. 12. 13. 14.
Referenced to lowest level frequency component in DTMF signal. Minimum signal acceptance level is measured with specified maximum frequency deviation. Input pins defined as IN+, IN-, and TOE. External voltage source used to bias VREF. This parameter also applies to a third tone injected onto the power supply. Referenced to Figure 1. Input DTMF tone level at -28 dBm.
(c) 2000 California Micro Devices Corp. All rights reserved. 9/28/2000
215 Topaz Street, Milpitas, California 95035
Tel: (408) 263-3214
Fax: (408) 263-7846
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CALIFORNIA MICRO DEVICES
CM8870/70C
Explanation of Events A) Tone bursts detected, tone duration invalid, outputs not updated. B) Tone #n detected, tone duration valid, tone decoded and latched in outputs. C) End of tone #n detected, tone absent duration valid, outputs remain latched until next valid tone. D) Outputs switched to high impedance state. E) Tone #n + 1 detected, tone duration valid, tone decoded and latched in outputs (currently high impedance). F) Acceptable dropout of tone #n + 1, tone absent duration invalid, outputs remain latched. G) End of tone #n + 1 detected, tone absent duration valid, outputs remain latched until next valid tone. Explanation of Symbols VIN ESt St/GT DTMF composite input signal. Early Steering Output. Indicates detection of valid tone frequencies. Steering input/guard time output. Drives external RC timing circuit. Q1-Q4 4-bit decoded tone output. StD Delayed Steering Output. Indicates that valid frequencies have been present/absent for the required guard time, thus constituting a valid signal. TOE Tone Output Enable (input). A low level shifts Q1-Q4 to its high impedance state. tREC Maximum DTMF signal duration not detected as valid. tREC Minimum DTMF signal duration required for valid recognition. tID Minimum time between valid DTMF signals. tDO Maximum allowable drop-out during valid DTMF signal. tDP Time to detect the presence of valid DTMF signals. tDA Time to detect the absence of valid DTMF signals. tGTP Guard time, tone present. tGTA Guard time, tone absent.
(c)2000 California Micro Devices Corp. All rights reserved.
4
215 Topaz Street, Milpitas, California 95035
Tel: (408) 263-3214
Fax: (408) 263-7846
www.calmicro.com
9/28/2000
CALIFORNIA MICRO DEVICES
Functional Description
The CAMD CM8870/70C DTMF Integrated Receiver provides the design engineer with not only low power consumption, but high performance in a small 18-pin DIP, SOIC, or 20-pin PLCC package configuration. The CM8870/70C's internal architecture consists of a bandsplit filter section which separates the high and low tones of the received pair, followed by a digital decode (counting) section which verifies both the frequency and duration of the received tones before passing the resultant 4-bit code to the output bus.
CM8870/70C
considered a valid pause. This capability together with the capability of selecting the steering time constants externally, allows the designer to tailor performance to meet a wide variety of system requirements.
Guard Time Adjustment
In situations which do not require independent selection of receive and pause, the simple steering circuit of Figure 4 is applicable. Component values are chosen according to the following formula: tREC = tDP + tGTP tGTP 0.67 RC The value of tDP is a parameter of the device and tREC is the minimum signal duration to be recognized by the receiver. A value for C of 0.1 uF is recommended for most applications, leaving R to be selected by the designer. For example, a suitable value of R for a tREC of 40 milliseconds would be 300K. A typical circuit using this steering configuration is shown in Figure 1. The timing requirements for most telecommunication applications are satisfied with this circuit. Different steering arrangements may be used to select independently the guardtimes for tone-present (tGTP) and tone absent (tGTA). This may be necessary to meet system specifications which place both accept and reject limits on both tone duration and interdigit pause. Guard time adjustment also allows the designer to tailor system parameters such as talk-off and noise immunity. Increasing tREC improves talk-off performance, since it reduces the probability that tones simulated by speech will maintain signal condition for long enough to be registered. On the other hand, a relatively short tREC with a long tDO would be appropriate for extremely noisy environments where fast acquisition time and immunity to drop-outs would be requirements. Design information for guard time adjustment is shown in Figure 5.
Filter Section
Separation of the low-group and high-group tones is achieved by applying the dual-tone signal to the inputs of two 9th-order switched capacitor bandpass filters. The bandwidths of these filters correspond to the bands enclosing the low-group and high-group tones (See Figure 3). The filter section also incorporates notches at 350 Hz and 440 Hz which provides excellent dial tone rejection. Each filter output is followed by a single order switched capacitor section which smooths the signals prior to limiting. Signal limiting is performed by highgain comparators. These comparators are provided with a hysteresis to prevent detection of unwanted low-level signals and noise. The outputs of the comparators provide full-rail logic swings at the frequencies of the incoming tones.
Decoder Section
The CM8870/70C decoder uses a digital counting technique to determine the frequencies of the limited tones and to verify that these tones correspond to standard DTMF frequencies. A complex averaging algorithm is used to protect against tone simulation by extraneous signals (such as voice) while providing tolerance to small frequency variations. The averaging algorithm has been developed to ensure an optimum combination of immunity to "talk-off" and tolerance to the presence of interfering signals (third tones) and noise. When the detector recognizes the simultaneous presence of two valid tones (known as "signal condition"), it raises the "Early Steering" flag (ESt). Any subsequent loss of signal condition will cause ESt to fall.
Input Configuration
The input arrangement of the CM8870/70C provides a differential input operational amplifier as well as a bias source (VREF) which is used to bias the inputs at mid-rail. Provision is made for connection of a feedback resistor to the op-amp output (GS) for adjustment of gain. In a single-ended configuration, the input pins are connected as shown in Figure 1, with the op-amp connected for unity gain and VREF biasing the input at 1/2 VDD. Figure 6 shows the differential configuration, which permits the adjustment of gain with the feedback resistor R5.
Steering Circuit
Before the registration of a decoded tone pair, the receiver checks for a valid signal duration (referred to as "characterrecognition-condition"). This check is performed by an external RC time constant driven by ESt. A logic high on ESt causes VC (See Figure 4) to rise as the capacitor discharges. Providing signal condition is maintained (ESt remains high) for the validation period (tGTP), VC reaches the threshold (VTSt) of the steering logic to register the tone pair, thus latching its corresponding 4-bit code (See Figure 2) into the output latch. At this point, the GT output is activated and drives VC to VDD. GT continues to drive high as long as ESt remains high, signaling that a received tone pair has been registered. The contents of the output latch are made available on the 4-bit output bus by raising the three-state control input (TOE) to a logic high. The steering circuit works in reverse to validate the interdigit pause between signals. Thus, as well as rejecting signals too short to be considered valid, the receiver will tolerate signal interruptions (drop outs) too short to be
(c) 2000 California Micro Devices Corp. All rights reserved. 9/28/2000
Clock Circuit
The internal clock circuit is completed with the addition of a standard television color burst crystal or ceramic resonator having a resonant frequency of 3.579545 MHz. The CM8870C in a PLCC package has a buffered oscillator output (OSC3) that can be used to drive clock inputs of other devices such as a microprocessor or other CM887X's as shown in Figure 7. Multiple CM8870/70Cs can be connected as shown in figure 8 such that only one crystal or resonator is required.
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CALIFORNIA MICRO DEVICES
Pin Function Table
PIN FUNCTION
CM8870/70C
N am e
IN + IN GS VREF IN H OSC3 PD OSC1 OSC2 V SS TOE Q1 Q2 Q3 Q4 StD ESt St/Gt VDD IC Non-inverting Input I n v e rti n g I n p u t Gain Select
D escription
Connection to the front-end differential amplifier
Gives access to output of front-end differential amplifier for connection of feedback resistor. R e f e r e n c e v o l ta g e o u tp u t ( n o mi n a l l y V D D /2 ) . M a y b e u s e d to b i a s th e i n p u ts a t mi d -r a i l . Inhibits detection of tones represents keys A, B, C, and D D igital buffered oscillator output. Power D own Clock Input Clock Output Logic high powers down the device and inhibits the oscillator. 3.579545 MHz crystal connected between these pins completes internal oscillator.
Negative power supply (normally connected to OV). T h r e e -s t a t e o u t p u t e n a b l e ( i n p u t ) . L o g i c h i g h e n a b l e s t h e o u t p u t s Q1 -Q4 . I n t e r n a l p u l l -u p . Three-state outputs. When enabled by TOE, provides the code corresponding to the last valid tone pair received. (See Fig. 2). D elayed steering output. Presents a logic high when a received tone pair has been registered and the output latch is updated. Returns to logic low when the voltage on St/GT falls below VTSt. Early steering output. Presents a logic high immediately when the digital algorithm detects a recognizable tone pair (signal condition). Any momentary loss of signal condition will cause ESt to return to a logic low. Steering input/guard time output (bidirectional). A voltage greater than VTSt detected a St causes the device to register the detected tone pair . The GT output acts to reset the external steering time constant, and its state is a function of ESt and the voltage on St. (See Fig. 2) Positive power supply. Internal Connection. Must be tied to VSS (for 8870 configuration only)
FLOW
697 697 697 770 770 770 8 52 8 52 8 52 9 41 9 41 9 41 697 770 8 52 9 41 -
F H IGH
1209 13 36
KE Y
1 2
TOW
H H
Q4
0 0
Q3
0 0
Q2
0 1
Q1
1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 Z
All resistors are 1%tolerance. All capacitors are 5% tolerance.
1477 3 H 0 12 0 9 4 H 0 13 3 6 5 H 0 147 7 6 H 0 12 0 9 7 H 0 13 3 6 8 H 1 147 7 9 H 1 12 0 9 0 H 1 13 3 6 * H 1 147 7 # H 1 16 3 3 A H 1 16 3 3 B H 1 16 3 3 C H 1 16 3 3 D H 0 ANY L Z L = logic Low, H = Logic High, Z = High
Figure 2. Functional Diode Table
0 1 1 0 1 0 1 1 1 1 0 0 0 0 0 1 0 1 1 0 1 0 1 1 1 1 0 0 Z Z Impedance
Figure 1. Single Ended Input Configuration
(c)2000 California Micro Devices Corp. All rights reserved.
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215 Topaz Street, Milpitas, California 95035
Tel: (408) 263-3214
Fax: (408) 263-7846
www.calmicro.com
9/28/2000
CALIFORNIA MICRO DEVICES
CM8870/70C
Figure 3. Typical Filter Characteristic
Figure 4. Basic Steering Circuit
Figure 5. Guard Time Adjustment
Figure 6. Differential Input Configuration
(c) 2000 California Micro Devices Corp. All rights reserved. 9/28/2000
215 Topaz Street, Milpitas, California 95035
Tel: (408) 263-3214
Fax: (408) 263-7846
www.calmicro.com
7
CALIFORNIA MICRO DEVICES
CM8870/70C
OSC1
OSC2
OSC3
OSC1
OSC2
OSC1
OSC2
OSC1
OSC2
OSC1 of other CM887X's Clock input of other devices 30pF
3.58 Mhz 30pF 30pF
Figure 7. CM8870C Crystal Connection (PLCC Package Only)
Pin Assignments
Figure 8. CM8870/70C Crystal Connection
St/GT
3
3
2
2
1
1
20
20
IN+ INGS VREF INH IC* OSC1 OSC2 VSS
1 2
18 17
VDD St/GT ESt StD Q4 Q3 Q2 Q1 TOE
IN+ INGS VREF IC* IC* OSC1 OSC2 VSS
1 2 3
18 17 16
VDD St/GT ESt StD Q4 Q3 Q2 Q1 TOE GS VREF 4 5
3 4 5 6 7 8 9
CM8870C
16 15 14 13 12 11 10
4 5 6 7 8 9
CM8870
15 14 13 12 11 10
19
18
ESt StD NC Q4 Q3
VREF INH PD OSC3 OSC1
4 5 6 7 8
19
18
St/GT
VDD
VDD
ININ+
IN+ IN-
ININ+
IN+ IN-
NC
GS
Est StD NC Q4 Q3
IC * 6 IC * 7 OSC1 8
CM8870
10 11 12 13 9
17 16 15 14
CM8870C
10 11 12 13 Q2 9
17 16 15 14
OSC2
TOE
OSC2
TOE
VSS
P -- Plastic DIP (18) F -- Plastic SOP EIAJ (18) S -- SOIC (18)
P -- Plastic DIP (18) F -- Plastic SOP EIAJ (18) S -- SOIC (18)
PE -- PLCC (20) * -- Connect To VSS
PE
-- PLCC (20)
Ordering Information Example: Product Identification Number Package P -- F -- PE -- S --
CM8870 CM8870C
P
I
Plastic DIP (18) Plastic SOP EIAJ (18) PLCC (20) SOIC (18)
Temperature/Processing None -- 0OC to +70OC, 5% P.S. Tol. I -- -40OC to +85OC, 5% P.S. Tol.
(c)2000 California Micro Devices Corp. All rights reserved.
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VSS
Q1
Q2
Q1
9/28/2000

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