MICROCHIP TC9400, TC9401, TC9402 Technical data

TC9400/9401/9402

AMPLIFIER OUT

THRESHOLD DETECTOR

FREQ/2 OUT

OUTPUT COMMON

PULSE FREQ OUT

BIAS

ZERO ADJ

REF

OUT

GND

REF

TC9400 TC9401 TC9402

14-Pin Plastic DIP/CERDIP

14-Pin SOIC

TC9400 TC9401 TC9402

NC = No Internal Connection

AMPLIFIER OUT

THRESHOLD DETECTOR

FREQ/2 OUT

OUTPUT COMMON

PULSE FREQ OUT

BIAS

ZERO ADJ

REF

OUT

GND

REF

Voltage-to-Frequency / Frequency-to-Voltage Converters

Features:

VOLTAGE-TO-FREQUENCY

• Choice of Linearity:

- TC9401: 0.01%

- TC9400: 0.05%

- TC9402: 0.25%

• DC to 100 kHz (F/V) or 1 Hz to 100 kHz (V/F)

• Low Power Dissipation: 27 mW (Typ.)

• Single/Dual Supply Operation:

- +8V to +15V or ±4V to ±7.5V

• Gain Temperature Stability: ±25 ppm/°C (Typ.)

• Programmable Scale Factor

FREQUENCY-TO-VOLTAGE

• Operation: DC to 100 kHz

• Choice of Linearity:

- TC9401: 0.02%

- TC9400: 0.05%

- TC9402: 0.25%

• Programmable Scale Factor

Applications:

• Microprocessor Data Acquisition

• 13-bit Analog-to-Digital Converters (ADC)

• Analog Data Transmission and Recording

• Phase Locked Loops

• Frequency Meters/Tachometer

• Motor Control

• FM Demodulation

General Description:

The TC9400/9401/9402 are low-cost Voltage-to-Frequency (V/F) converters, utilizing low-power CMOS technology. The converters accept a variable analog input signal and generate an output pulse train, whose frequency is linearly proportional to the input voltage.

The devices can also be used as highly accurate Frequency-to-Voltage (F/V) converters, accepting virtually any input frequency waveform and providing a linearly proportional voltage output.

A complete V/F or F/V system only requires the addition of two capacitors, three resistors, and reference voltage.

Package Type

TC9400/9401/9402

REF

TC9400

Integrator Op Amp

Integrator Capacitor

Threshold Detector

One Shot

Pulse Output

Pulse/2 Output

÷2

Input

Voltage

Reference Capacitor

Reference Voltage

Functional Block Diagram

TC9400/9401/9402

1.0 ELECTRICAL CHARACTERISTICS

Absolute Maximum Ratings †

VDD – VSS ......................................................................+18V

..................................................................................10 mA

– V

OUTMAX

– VSS .....................................................................-1.5V

REF

Storage Temperature Range .........................-65°C to +150°C

Operating Temperature Range:

C Device ...................................................... 0°C to +70°C

E Device.................................................... -40°C to +85°C

Package Dissipation (T

8-Pin CerDIP........................................................800 mW

8-Pin Plastic DIP ..................................................730 mW

8-Pin SOIC...........................................................470 mW

Common.................................................23V

OUT

≤ 70°C):

† Stresses above those listed under “Absolute Maximum

Ratings” may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operation sections of the specifications is not implied. Exposure to Absolute Maximum Rating conditions for extended periods may affect device reliability.

TC940X ELECTRICAL SPECIFICATIONS

Electrical Characteristics: unless otherwise specified, VDD = +5V, VSS = -5V, V

10 kHz. T

= +25°C, unless temperature range is specified (-40°C to +85°C for E device, 0°C to +70°C for C device).

Parameter Min Typ Max Min Typ Max Min Typ Max Units Test Conditions

Voltage-to-Frequency

GND

= 0V, V

REF

= -5V, R

= 100 kΩ, Full Scale =

BIAS

Accuracy TC9400 TC9401 TC9402

Linearity 10 kHz — 0.01 0.05 — 0.004 0.01 — 0.05 0.25 %

Linearity 100 kHz — 0.1 0.25 — 0.04 0.08 — 0.25 0.5 %

Gain Temperature Drift (Note 1)

Gain Variance — ±10 — — ±10 — — ±10 — % of

Zero Offset

(Note 2)

Zero Temperature Drift (Note 1)

Note 1: Full temperature range; not tested.

2: I

= 0.

3: Full temperature range, I 4: I

OUT

5: Threshold Detect = 5V, Amp Out = 0V, full temperature range. 6: 10 Hz to 100 kHz; not tested. 7: 5 µs minimum positive pulse width and 0.5 µs minimum negative pulse width. 8: t

= tF = 20 ns.

9: R

≥ 2kΩ, tested @ 10 kΩ.

10: Full temperature range, V

— ±25 ±40 — ±25 ±40 — ±50 ± 100 ppm/°C

— ±10 ±50 — ±10 ±50 — ±20 ±100 mV Correction at Zero

— ±25 ±50 — ±25 ±50 — ±50 ±100 µV/°C Variation in Zero Offset

= 10 mA.

= 10 µA.

OUT

= -0.1V.

Full Scale

Nominal

Output Deviation from Straight Line Between Normalized Zero and Full Scale Input

Output Deviation from Straight Line Between Normalized Zero Reading and Full Scale Input

Variation in Gain A due to Temperature Change

Variation from Ideal Accuracy

Adjust for Zero Output when Input is Zero

Due to Temperature Change

TC9400/9401/9402

TC940X ELECTRICAL SPECIFICATIONS (CONTINUED)

Electrical Characteristics: unless otherwise specified, VDD = +5V, VSS = -5V, V

10 kHz. T

= +25°C, unless temperature range is specified (-40°C to +85°C for E device, 0°C to +70°C for C device).

Parameter Min Typ Max Min Typ Max Min Typ Max Units Test Conditions

Analog Input

Full Scale — 10 — — 10 — — 10 — µA Full Scale Analog Input

Over Range — — 50 — — 50 — — 50 µA Over Range Current

Response Time — 2 — — 2 — — 2 — Cycle Settling Time to 0.1%

Digital Section TC9400 TC9401 TC9402

@ IOL = 10mA — 0.2 0.4 — 0.2 0.4 — 0.2 0.4 V Logic “0” Output

SAT

– V

OUTMAX

Common (Note 4)

OUT

Pulse Frequency

— — 18 — — 18 — — 18 V Voltage Range Between

—3——3——3 — µs

Output Width

Frequency-to-Voltage

Supply Current

Quiescent

(Note 5)

Quiescent

(Note 5)

Supply 4 — 7.5 4 — 7.5 4 — 7.5 V Operating Range of

Supply -4 — -7.5 -4 — -7.5 -4 — -7.5 V Operating Range of

Reference Voltage

– V

REF

Accuracy

Non-Linearity

(Note 10)

Input Frequency Range

(Notes 7 and 8)

Note 1: Full temperature range; not tested.

2: I

= 0.

3: Full temperature range, I 4: I

OUT

5: Threshold Detect = 5V, Amp Out = 0V, full temperature range. 6: 10 Hz to 100 kHz; not tested. 7: 5 µs minimum positive pulse width and 0.5 µs minimum negative pulse width. 8: t

= tF = 20 ns.

9: R

≥ 2kΩ, tested @ 10 kΩ.

10: Full temperature range, V

— 1.5 6 — 1.5 6 — 3 10 mA Current Required from

— -1.5 -6 — -1.5 -6 — -3 -10 mA Current Required from

-2.5 — — -2.5 — — -2.5 — — V Range of Voltage

— 0.02 0.05 — 0.01 0.02 — 0.05 0.25 %

10 — 100k 10 — 100k 10 — 100k Hz Frequency Range for

= 10 mA.

= 10 µA.

OUT

= -0.1V.

GND

= 0V, V

= -5V, R

REF

Full Scale

= 100 kΩ, Full Scale =

BIAS

Current to achieve Specified Accuracy

Full Scale

Voltage (Note 3)

Output and Common

Positive Supply during Operation

Negative Supply during Operation

Positive Supply

Negative Supply

Reference Input

Deviation from ideal Transfer Function as a Percentage Full Scale Voltage

Specified Non-Linearity

TC9400/9401/9402

TC940X ELECTRICAL SPECIFICATIONS (CONTINUED)

Electrical Characteristics: unless otherwise specified, VDD = +5V, VSS = -5V, V

10 kHz. T

= +25°C, unless temperature range is specified (-40°C to +85°C for E device, 0°C to +70°C for C device).

Parameter Min Typ Max Min Typ Max Min Typ Max Units Test Conditions

Frequency Input

Positive Excursion 0.4 — V

0.4 — V

Negative Excursion -0.4 -2 -0.4 — -2 -0.4 — -2 V Voltage Required to

Minimum Positive

—5——5——5 — μs Time between

Pulse Width

(Note 8)

Minimum Negative

— 0.5 — — 0.5 — — 0.5 — μs Time Between

Pulse Width

(Note 8)

Input Impedance — 10 — — 10 — — 10 MΩ

Analog Outputs TC9400 TC9401 TC9402

Output Voltage

(Note 9)

—V

– 1 — — V

Output Loading 2 — — 2 — — 2 — — kΩ Resistive Loading at

Supply Current TC9400 TC9401 TC9402

Quiescent

(Note 10)

Quiescent

(Note 10)

Supply 4 — 7.5 4 — 7.5 4 — 7.5 V Operating Range of

Supply -4 — -7.5 -4 — -7.5 -4 — -7.5 V Operating Range of

— 1.5 6 — 1.5 6 — 3 10 mA Current Required from

— -1.5 -6 -1.5 -6 — -3 -10 mA Current Required from

Reference Voltage

REF

– V

-2.5 — — -2.5 — — -2.5 — — V Range of Voltage

Note 1: Full temperature range; not tested.

2: I

= 0.

3: Full temperature range, I 4: I

= 10 µA.

OUT

= 10 mA.

5: Threshold Detect = 5V, Amp Out = 0V, full temperature range. 6: 10 Hz to 100 kHz; not tested. 7: 5 µs minimum positive pulse width and 0.5 µs minimum negative pulse width. 8: t

= tF = 20 ns.

9: R

≥ 2kΩ, tested @ 10 kΩ.

10: Full temperature range, V

= -0.1V.

GND

= 0V, V

REF

= -5V, R

= 100 kΩ, Full Scale =

BIAS

V Voltage Required to

Turn Threshold Detector On

Turn Threshold Detector Off

Threshold Crossings

– 1 — V Voltage Range of Op

Amp Output for Specified Non-Linearity

Output of Op Amp

Positive Supply During Operation

Negative Supply During Operation

Positive Supply

Negative Supply

Reference Input

TC9400/9401/9402

2.0 PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 2-1.

TABLE 2-1: PIN FUNCTION TABLE

Pin No. Symbol Description

2 ZERO ADJ Low frequency adjustment input.

6 GND Analog ground.

8 PULSE FREQ

9OUTPUT

10 FREQ/2 OUT This open drain output is a square wave at one-half the frequency of the pulse output

11 THRESHOLD

12 AMPLIFIER OUT Output of the integrator amplifier.

13 NC No internal connection.

14 V

BIAS

OUT Reference capacitor connection.

REF

OUT

COMMON

DETECTOR

This pin sets bias current in the TC9400. Connect to VSS through a 100 kΩ resistor.

Input current connection for the V/F converter.

Negative power supply voltage connection, typically -5V.

Voltage reference input, typically -5V.

Frequency output. This open drain output will pulse LOW each time the Freq. Threshold Detector limit is reached. The pulse rate is proportional to input voltage.

Source connection for the open drain output FETs.

(Pin 8). Output transitions of this pin occur on the rising edge of Pin 8.

Input to the Threshold Detector. This pin is the frequency input during F/V operation.

Positive power supply connection, typically +5V.

2.1 Bias Current (I

BIAS

)

An external resistor, connected to VSS, sets the bias point for the TC9400. Specifications for the TC9400 are based on R

= 100 kΩ ±10%, unless otherwise

BIAS

noted.

Increasing the maximum frequency of the TC9400 beyond 100 kHz is limited by the pulse width of the pulse output (typically 3 µs). Reducing R

BIAS

will decrease the pulse width and increase the maximum operating frequency, but linearity errors will also increase. R

can be reduced to 20 kΩ, which will

BIAS

typically produce a maximum full scale frequency of 500 kHz.

2.2 Zero Adjust

This pin is the non-inverting input of the operational amplifier. The low frequency set point is determined by adjusting the voltage at this pin.

2.3 Input Current (IIN)

The inverting input of the operational amplifier and the summing junction when connected in the V/F mode. An input current of 10 μA is specified, but an over range current up to 50 μA can be used without detrimental effect to the circuit operation. I junction of an operational amplifier. Voltage sources cannot be attached directly, but must be buffered by external resistors.

connects the summing

2.4 Voltage Capacitor (V

The charging current for C

is supplied through this

REF

Out)

pin. When the op amp output reaches the threshold level, this pin is internally connected to the reference

x C

voltage and a charge, equal to V

REF

, is removed

REF

from the integrator capacitor. After about 3μsec, this pin is internally connected to the summing junction of the op amp to discharge C

. Break-before-make switch-

REF

ing ensures that the reference voltage is not directly applied to the summing junction.

2.5 Voltage Reference (V

REF

)

A reference voltage from either a precision source, or the V

supply is applied to this pin. Accuracy of the

TC9400 is dependent on the voltage regulation and temperature characteristics of the reference circuitry.

Since the TC9400 is a charge balancing V/F converter, the reference current will be equal to the input current. For this reason, the DC impedance of the reference voltage source must be kept low enough to prevent linearity errors. For linearity of 0.01%, a reference impedance of 200Ω or less is recommended. A 0.1 µF bypass capacitor should be connected from V

REF

ground.

TC9400/9401/9402

3ms Typ.

1/f

OUT

Amp Out

REF

INT

Note 1: To adjust F

MIN

, set VIN = 10 mV and adjust the 50 kΩ offset for 10 Hz output.

2: To adjust F

MAX

, set VIN = 10V and adjust RIN or V

REF

for 10 kHz output.

3: To increase F

OUTMAX

to 100 kHz, change C

REF

to 2 pF and C

INT

to 75 pF.

4: For high performance applications, use high stability components for R

, C

REF

. V

REF

(metal film

resistors and glass capacitors). Also, separate output ground (Pin 9) from input ground (Pin 6).

2.6 Pulse Freq Out

This output is an open-drain N-channel FET, which provides a pulse waveform whose frequency is proportional to the input voltage. This output requires a pullup resistor and interfaces directly with MOS, CMOS, and TTL logic (see Figure 2-1).

2.7 Output Common

The sources of both the FREQ/2 OUT and the PULSE FREQ OUT are connected to this pin. An output level swing from the drain voltage to ground, or to the V

supply, may be obtained by connecting this pin to the appropriate point.

2.8 Freq/2 Out

This output is an open-drain N-channel FET, which provides a square-wave one-half the frequency of the pulse frequency output. The FREQ/2 OUT output will change state on the rising edge of PULSE FREQ OUT. This output requires a pull-up resistor and interfaces directly with MOS, CMOS, and TTL logic.

2.9 Threshold Detector Input

In the V/F mode, this input is connected to the AMPLIFIER OUT output (Pin 12) and triggers a 3 µs pulse when the input voltage passes through its threshold. In the F/V mode, the input frequency is applied to this input.

The nominal threshold of the detector is half way between the power supplies, or (V

+ VSS)/2 ±400

mV. The TC9400’s charge balancing V/F technique is not dependent on a precision comparator threshold, because the threshold only sets the lower limit of the op amp output. The op amp’s peak-to-peak output swing, which determines the frequency, is only influenced by external capacitors and by V

REF

2.10 Amplifier Out

This pin is the output stage of the operational amplifier. During V/F operation, a negative going ramp signal is available at this pin. In the F/V mode, a voltage proportional to the frequency input is generated.

FIGURE 2-1: Output Waveforms.

TC9400/9401/9402

–

+5V

10 kΩ

OUT

3ms

Delay

Self-

Star t

20 kΩ

60 pF

Op Amp

INT

820 pF

REF

180 pF

12 pF

1MΩ

+5V

-5V

50 kΩ

510 kΩ

10 kΩ

Offset Adjust

Zero Adjust

0V –10V

BIAS

-5V

Output

Common

REF

OUT

BIAS

100 kΩ

AMP OUT

TC9400 TC9401 TC9402

GND

Threshold

Detector

Threshold Detect

Reference Voltage

(Typically -5V)

÷2

REF

-3V

INPUT

3.0 DETAILED DESCRIPTION

3.1 Voltage-to-Frequency (V/F) Circuit

Description

The TC9400 V/F converter operates on the principal of charge balancing. The operation of the TC9400 is easily understood by referring to Figure 3-1. The input voltage (V resistor. This current is then converted to a charge on the integrating capacitor and shows up as a linearly decreasing voltage at the output of the op amp. The lower limit of the output swing is set by the threshold detector, which causes the reference voltage to be applied to the reference capacitor for a time period long enough to charge the capacitor to the reference voltage. This action reduces the charge on the integrating capacitor by a fixed amount (q = C the op amp output to step up a finite amount.

At the end of the charging period, C This dissipates the charge stored on the reference capacitor, so that when the output again crosses zero, the system is ready to recycle. In this manner, the continued discharging of the integrating capacitor by the input is balanced out by fixed charges from the refer-

) is converted to a current (IIN) by the input

x V

REF

), causing

REF

is shorted out.

ence voltage. As the input voltage is increased, the number of reference pulses required to maintain balance increases, which causes the output frequency to also increase. Since each charge increment is fixed, the increase in frequency with voltage is linear. In addition, the accuracy of the output pulse width does not directly affect the linearity of the V/F. The pulse must simply be long enough for full charge transfer to take place.

The TC9400 contains a “self-start” circuit to ensure the V/F converter always operates properly when power is first applied. In the event that, during power-on, the op amp output is below the threshold and C

is already

REF

charged, a positive voltage step will not occur. The op amp output will continue to decrease until it crosses the

-3.0V threshold of the “self-start” comparator. When this happens, an internal resistor is connected to the op amp input, which forces the output to go positive until the TC9400 is in its normal Operating mode.

The TC9400 utilizes low-power CMOS processing for low input bias and offset currents, with very low power dissipation. The open drain N-channel output FETs provide high voltage and high current sink capability.

FIGURE 3-1: 10 Hz to 10 kHz V/F Converter.

3.2 Voltage-to-Time Measurements

The TC9400 output can be measured in the time domain as well as the frequency domain. Some microcomputers, for example, have extensive timing capability, but limited counter capability. Also, the response time of a time domain measurement is only the period between two output pulses, while the frequency measurement must accumulate pulses during the entire counter time-base period.

Time measurements can be made from either the TC9400’s PULSE FREQ OUT output, or from the FREQ/2 OUT output. The FREQ/2 OUT output changes state on the rising edge of PULSE FREQ OUT, so FREQ/2 OUT is a symmetrical square wave at one-half the pulse output frequency. Timing measurements can, therefore, be made between successive PULSE FREQ OUT pulses, or while FREQ/2 OUT is high (or low).

TC9400/9401/9402

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