Datasheet LMC567CN, LMC567CM, LMC567CMX Datasheet (NSC)

LMC567
Low Power Tone Decoder

General Description

The LMC567 is a low power general purpose LMCMOS

™

tone decoder which is functionally similar to the industry
standard LM567. It consists of a twice frequency
voltage-controlled oscillator (VCO) and quadrature dividers
which establish the reference signals for phase and ampli­tude detectors. The phase detector and VCO form a
phase-locked loop (PLL) which locks to an input signal fre­quency which is within the control range of the VCO. When
the PLL is locked and the input signal amplitude exceeds an
internally pre-set threshold, a switch to ground is activated
on the output pin. External components set up the oscillator
to run at twice the input frequency and determine the phase
and amplitude filter time constants.

Features

n Functionally similar to LM567
n 2V to 9V supply voltage range
n Low supply current drain
n No increase in current with output activated
n Operates to 500 kHz input frequency
n High oscillator stability
n Ground-referenced input
n Hysteresis added to amplitude comparator
n Out-of-band signals and noise rejected
n 20 mA output current capability

Block Diagram (with External Components)

LMCMOS™is a trademark of National Semiconductor Corp.

DS008670-1

Order Number LMC567CM or LMC567CN

See NS Package Number M08A or N08E

June 1999

LMC567 Low Power Tone Decoder

© 1999 National Semiconductor Corporation DS008670 www.national.com

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Input Voltage, Pin 3 2 V

p–p

Supply Voltage, Pin 4 10V
Output Voltage, Pin 8 13V
Voltage at All Other Pins Vs to Gnd
Output Current, Pin 8 30 mA
Package Dissipation 500 mW
Operating Temperature Range (T

A

) −25˚C to +125˚C

Storage Temperature Range −55˚C to +150˚C
Soldering Information

Dual-In-Line Package

Soldering (10 sec.) 260˚C

Small Outline Package

Vapor Phase (60 sec.) 215˚C
Infrared (15 sec.) 220˚C

See AN-450 “Surface Mounting Methods and Their Effect
on Product Reliability” for other methods of soldering
surface mount devices.

Electrical Characteristics

Test Circuit, T

A

=

25˚C, V

s

=

5V, RtCt

#

2, Sw. 1 Pos. 0, and no input, unless otherwise noted.

Symbol Parameter Conditions Min Typ Max Units

I4 Power Supply

Current

RtCt

#

1, Quiescent

or Activated

V

s

=

2V 0.3

mAdcV

s

=

5V 0.5 0.8

V

s

=

9V 0.8 1.3
V3 Input D.C. Bias 0 mVdc
R3 Input Resistance 40 kΩ
I8 Output Leakage 1 100 nAdc
f

0

Center Frequency,
F

osc

÷

2

RtCt

#

2, Measure Oscillator

Frequency and Divide by 2

V

s

=

2V 98

kHzV

s

=

5V 92 103 113

V

s

=

9V 105
∆f

0

Center Frequency
Shift with Supply

1.0 2.0

%

/V

V

in

Input Threshold Set Input Frequency Equal to f

0

Measured Above, Increase Input Level
Until Pin 8 Goes Low.

V

s

=

2V 11 20 27

mVrmsV

s

=

5V 17 30 45

V

s

=

9V 45
∆V

in

Input Hysteresis Starting at Input Threshold, Decrease Input

Level Until Pin 8 goes High.

1.5 mVrms

V8 Output ’Sat’ Voltage Input Level

>

Threshold

Choose RL for Specified I8

I8=2 mA 0.06 0.15

Vdc

I8=20 mA 0.7

L.D.B.W. Largest Detection

Bandwidth

Measure F

osc

with Sw. 1 in

Pos. 0, 1, and 2;

V

s

=

2V

71115

%

V

s

=

5V

11 14 17

V

s

=

9V

15

∆BW Bandwidth Skew

0±1.0

%

f

max

Highest Center
Freq.

RtCt#3, Measure Oscillator Frequency and Divide by 2

700 kHz

V

in

Input Threshold at
f

max

Set Input Frequency Equal to f

max

measured Above,

Increase Input Level Until Pin 8 goes Low.

35

mVrms

Note 1: Absolute Maximum Ratingsindicatelimitsbeyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is func­tional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guar­antee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is
given, however, the typical value is a good indication of device performance.

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Test Circuit

RtCt Rt Ct

#

1 100k 300 pF

#

2 10k 300 pF

#

3 5.1k 62 pF

DS008670-2

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Typical Performance Characteristics

Applications Information

(refer to Block

Diagram)

GENERAL

The LMC567 low power tone decoder can be operated at
supply voltages of 2V to 9V and at input frequencies ranging
from 1 Hz up to 500 kHz.

The LMC567 can be directly substituted in most LM567 ap­plications with the following provisions:

1. Oscillator timing capacitor Ct must be halved to double
the oscillator frequency relative to the input frequency
(See OSCILLATOR TIMING COMPONENTS).

2. Filter capacitors C1 and C2 must be reduced by a factor
of 8 to maintain the same filter time constants.

3. The output current demanded of pin 8 must be limited to
the specified capability of the LMC567.

OSCILLATOR TIMING COMPONENTS

The voltage-controlled oscillator (VCO) on the LMC567 must
be set up to run at twice the frequency of the input signal
tone to be decoded. The center frequency of the VCO is set
by timing resistor Rt and timing capacitor Ct connected to
pins 5 and 6 of the IC. The center frequency as a function of
Rt and Ct is given by:

Since this will cause an input tone of half F

osc

to be decoded,

This equation is accurate at low frequencies; however,
above 50 kHz (F

osc

=

100 kHz), internal delays cause the

actual frequency to be lower than predicted.
The choice of Rt and Ct will be a tradeoff between supply

current and practical capacitor values. An additional supply
current component is introduced due to Rt being switched to
V

s

every half cycle to charge Ct:

I

s

due to Rt=Vs/(4Rt)

Thus the supply current can be minimized by keeping Rt as
large as possible (see supply current vs. operating fre­quency curves). However, the desired frequency will dictate
an RtCt product such that increasing Rt will require a smaller
Ct. Below Ct=100 pF, circuit board stray capacitances be­gin to play a role in determining the oscillation frequency
which ultimately limits the minimum Ct.

To allow for I.C. and component value tolerances, the oscil­lator timing components will require a trim. This is generally
accomplished by using a variable resistor as part of Rt, al­though Ct could also be padded. The amount of initial fre­quency variation due to the LMC567 itself is given in the
electrical specifications; the total trim range must also ac­commodate the tolerances of Rt and Ct.

Supply Current vs.
Operating Frequency

DS008670-3

Bandwidth vs.
Input Signal Level

DS008670-7

Largest Detection
Bandwidth vs. Temp.

DS008670-8

Bandwidth as
a Function of C2

DS008670-9

Frequency Drift
with Temperature

DS008670-10

Frequency Drift
with Temperature

DS008670-11

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Applications Information (refer to Block

Diagram) (Continued)

SUPPLY DECOUPLING

The decoupling of supply pin 4 becomes more critical at high
supply voltages with high operating frequencies, requiring
C4 to be placed as close as possible to pin 4.

INPUT PIN

The input pin 3 is internally ground-referenced with a nomi­nal 40 kΩ resistor. Signals which are already centered on 0V
may be directly coupled to pin 3; however, any d.c. potential
must be isolated via a coupling capacitor. Inputs of multiple
LMC567 devices can be paralleled without individual d.c.
isolation.

LOOP FILTER

Pin 2 is the combined output of the phase detector and con­trol input of the VCO for the phase-locked loop (PLL). Ca­pacitor C2 in conjunction with the nominal 80 kΩ pin 2 inter­nal resistance forms the loop filter.

For small values of C2, the PLL will have a fast acquisition
time and the pull-in range will be set by the built in VCO fre­quency stops, which also determine the largest detection
bandwidth (LDBW). Increasing C2 results in improved noise
immunity at the expense of acquisition time, and the pull-in
range will begin to become narrower than the LDBW (see
Bandwidth as a Function of C2 curve). However, the maxi­mum hold-in range will always equal the LDBW.

OUTPUT FILTER

Pin 1 is the output of a negative-going amplitude detector
which has a nominal 0 signal output of 7/9 V

s

. When the PLL
is locked to the input, an increase in signal level causes the
detector output to move negative. When pin 1 reaches
2/3 V

s

the output is activated (see OUTPUT PIN).

Capacitor C1 in conjunction with the nominal 40 kΩ pin 1 in­ternal resistance forms the output filter. The size of C1 is a
tradeoff between slew rate and carrier ripple at the output
comparator. Low values of C1 produce the least delay be­tween the input and output for tone burst applications, while
larger values of C1 improve noise immunity.

Pin 1 also provides a means for shifting the input threshold
higher or lower by connecting an external resistor to supply
or ground. However, reducing the threshold using this tech­nique increases sensitivity to pin 1 carrier ripple and also re­sults in more part to part threshold variation.

OUTPUT PIN

The output at pin 8 is an N-channel FET switch to ground
which is activated when the PLL is locked and the input tone
is of sufficient amplitude to cause pin 1 to fall below 2/3 V

s

.
Apart from the obvious current component due to the exter­nal pin 8 load resistor, no additional supply current is re­quired to activate the switch. The on resistance of the switch
is inversely proportional to supply; thus the “sat” voltage for
a given output current will increase at lower supplies.

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Physical Dimensions inches (millimeters) unless otherwise noted

Molded Small Outline (SO) Package (M)

Order Number LMC567CM

NS Package Number M08A

Molded Dual-In-Line Package (N)

Order Number LMC567CN

NS Package Number N08E

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Notes

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NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.

2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.

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LMC567 Low Power Tone Decoder

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