LMC567CM/NOPB - National Semiconductor

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 inter-

nally 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

nFunctionally similar to LM567

n2V to 9V supply voltage range

nLow supply current drain

nNo increase in current with output activated

nOperates to 500 kHz input frequency

nHigh oscillator stability

nGround-referenced input

nHysteresis added to amplitude comparator

nOut-of-band signals and noise rejected

n20 mA output current capability

Block Diagram (with External Components)

00867001

Order Number LMC567CM or LMC567CN

See NS Package Number M08A or N08E

LMCMOS™is a trademark of National Semiconductor Corp.

June 1999

LMC567 Low Power Tone Decoder

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

) −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

= 25˚C, V

= 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

= 2V 0.3

mAdcV

= 5V 0.5 0.8

= 9V 0.8 1.3

V3 Input D.C. Bias 0 mVdc

R3 Input Resistance 40 kΩ

I8 Output Leakage 1 100 nAdc

Center Frequency,

osc

÷2

RtCt #2, Measure Oscillator

Frequency and Divide by 2

=2V 98

kHzV

= 5V 92 103 113

= 9V 105

∆f

Center Frequency

Shift with Supply 1.0 2.0 %/V

Input Threshold Set Input Frequency Equal to f

Measured

Above, Increase Input Level Until Pin 8

Goes Low.

=2V 112027

mVrmsV

=5V 173045

=9V 45

∆V

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=2mA 0.06 0.15 Vdc

I8=20mA 0.7

L.D.B.W. Largest Detection

Bandwidth

Measure F

osc

with Sw. 1 in

Pos. 0, 1, and 2;

=2V 71115

=5V 11 14 17

=9V 15

∆BW Bandwidth Skew

0±1.0 %

max

Highest Center Freq. RtCt #3, Measure Oscillator Frequency and Divide by 2 700 kHz

Input Threshold at

max

Set Input Frequency Equal to f

max

measured Above,

Increase Input Level Until Pin 8 goes Low. 35 mVrms

Note 1: Absolute Maximum Ratings indicate limits beyond 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.

LMC567

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Test Circuit

00867002

RtCt Rt Ct

#1 100k 300 pF

#2 10k 300 pF

#3 5.1k 62 pF

LMC567

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Typical Performance Characteristics

Supply Current vs.

Operating Frequency

Bandwidth vs.

Input Signal Level

00867003 00867007

Largest Detection

Bandwidth vs. Temp.

Bandwidth as

a Function of C2

00867008 00867009

Frequency Drift

with Temperature

Frequency Drift

with Temperature

00867010 00867011

LMC567

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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

every half cycle to charge Ct:

due to Rt = V

/(4Rt)

Thus the supply current can be minimized by keeping Rt as

large as possible (see supply current vs. operating fre-

quency 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 oscil-

lator 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 ac-

commodate the tolerances of Rt and Ct.

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 nomi-

nal 40 kΩresistor. 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 kΩpin 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 maxi-

mum 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

. 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

the output is activated (see OUTPUT PIN).

Capacitor C1 in conjunction with the nominal 40 kΩpin 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 be-

tween 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 tech-

nique 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

Apart from the obvious current component due to the exter-

nal pin 8 load resistor, no additional supply current is re-

quired 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.

LMC567

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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

LMC567

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Notes

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves

the right at any time without notice to change said circuitry and specifications.

For the most current product information visit us at www.national.com.

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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

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LMC567 Low Power Tone Decoder