Burr Brown VFC121BP, VFC121AP Datasheet

®

VFC121

Precision Single Power Supply

VOLTAGE-TO-FREQUENCY CONVERTER

FEATURES

● SINGLE SUPPLY OPERATION:

+4.5V to +36V

= 1.5MHz max

● f

O

● LOW NONLINEARITY: 0.03% max at

100kHz, 0.1% max at 1MHz

● HIGH INPUT IMPEDANCE

● VOLTAGE REFERENCE OUTPUT

● THERMOMETER OUTPUT: 1mV/

°K

DESCRIPTION

The VFC121 is a monolithic voltage-to-frequency
converter consisting of an integrating amplifier, volt­age reference, and one-shot charge pump circuitry.
High-frequency complementary NPN/PNP circuitry is
used to implement the charge-balance technique,
achieving speed and accuracy far superior to previous
single power supply VFCs.

The high-impedance input accepts signals from ground
potential to V

VIN= 0 to +2V

R

RIN= 8kΩ

– 2.5V. Power supplies from 4.5V to

S

C

= 2700pF

INT

Integrator

= 8kΩ

BIAS

(Optional)

R

TRIM

12
11

R

IN

10 9 13 2

V

REF

I

REF

APPLICA TIONS

● INTEGRATING A/D CONVERSION

● ANALOG SIGNAL TRANSMISSION

● PHASE-LOCKED LOOP VCO

● GALVANICALLY ISOLATED SYSTEMS

36V may be used. A 2.6V reference voltage output
may be used to excite sensors or bias external cir­cuitry. A thermometer output voltage proportional to
absolute temperature (°K) may be used as a tempera­ture sensor or for temperature compensation of appli­cations circuits.

Frequency output is an open-collector transistor. A
disable pin forces the output to the high impedance
state, allowing multiple VFCs to share a common
transmission path.

Comparator

V

REF

63 54

2.6V V

+5V Ground

+V

S

T

(Optional)

One
Shot

COS= 1200pF

V

PULL UP

14

8

R

PULL UP

0 to 100kHz

f

=

OUT

International Airport Industrial Park • Mailing Address: PO Box 11400 • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706

Tel: [phone] • Twx: 910-952-1111 • Cable: BBRCORP • Telex: 066-6491 • FAX: [phone] • Immediate Product Info: [phone]

© 1989 Burr-Brown Corporation PDS-971A Printed in U.S.A. March, 1992

SPECIFICATIONS

ELECTRICAL

At TA = +25°C, VS = +5V, and RIN = 8kΩ, unless otherwise noted.

VFC121AP VFC121BP
PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS
ACCURACY

Nonlinearity: f

Gain Error: f
Gain Drift: f
Relative to V
PSRR 0.025 * %/V

INPUT

Minimum Input Voltage 0*V
Maximum Input Voltage V
Impedance 10 100 * * MΩ
I

BIAS

V

OS

V

Drift T

OS

OPEN COLLECTOR OUTPUT

V

SAT

I

LEAKAGE

Fall Time 100 * ns
Delay to Rise R
Settling Time To Specified Linearity for

REFERENCE VOLTAGE

Voltage 2.59 2.6 2.61 * * * V
Voltage Drift 100 50 ppm/°C
Load Regulation I
PSRR V
Current Limit Short Circuit Protected

INTEGRATOR AMPLIFIER OUTPUT

Output Voltage Range R

COMPARATOR INPUT

I

BIAS

Trigger Voltage 2.6 * V
Input Voltage Range 0 2.9 * * V

THERMOMETER

V

T

V

Slope T

T

DISABLE INPUT

V

(Disabled) 2 * V

HIGH

V

LOW

I

(Disabled) V

HIGH

I

LOW

POWER SUPPLY

Voltage 4.5 5 36 * * * V
Current 7.5 10 * * mA

TEMPERATURE RANGE

Specified –25 +85 * * °C
Storage –40 +125 * * °C

* Same specification as VFC121AP.
NOTE: (1) One pulse of new frequency plus 1µs.

= 100kHz COS 1200pF, C

FS

f

= 1MHz COS 68pF, C

FS

= 100kHz COS 1200pF, C

FS

= 100kHz T

FS

REF

+VS = +5V to +36V 100 40 ppm/°C

I

Full Scale Input Step

= 2700pF 0.05 0.03 %FS

INT

= 270pF 0.1 0.1 %FS

INT

= 2700pF 10 * %FS

INT

MIN

to T

MAX

– 2.5 VS – 2 * * V

S

80 40 ppm/°C

150 300 * * nA
300 800 100 400 µV

to T

MIN

MAX

= 10mA 0.4 * V

PULL UP

V

= 5V 1 * µA

PULL UP

V

= 36V 10 * µA

PULL UP

= 470Ω 100 * ns

PULL UP

= 0 to 10mA 10 * mV

O

= +5V to +36V 10 * mV

S

= 100kΩ 0.8 2.9 * * V

L

(1)

10 * µV/°C

+1 * µA

TA = +25°C 298 * mV

MIN

to T

MAX

1 * mV/°K

0.8 * V

= 2V 10 * µA

HIGH

V

= 0.8V 10 * µA

LOW

ORDERING INFORMATION

LINEARITY

MODEL PACKAGE (f

VFC121AP Plastic DIP 0.05% –25°C to +85°C
VFC121BP Plastic DIP 0.03% –25°C to +85°C

The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user's own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.

®

VFC121

ERROR, MAX TEMPERATURE

= 100kHz) RANGE 1–24 25–99 100+

S

2

®

PIN CONFIGURATION PIN CONFIGURATION

Top View

NC

Disable

Gnd Sense

C

V

REF

NC

1
2
3

V



T

4
5



OS

6



7

14

f

OUT

13

+V

S

12

–V

IN

11

+V

IN

10

Int Out

9

Comp In

8

Gnd

ABSOLUTE MAXIMUM RATINGS

Power Supply Voltage (+VS) ................................................................ 40V

f

Sink Current............................................................................... 20mA

OUT

Comparator In Voltage .......................................................... –0.5V to +3V

Enable Input........................................................................... –0.3V to +V

Integrator Common-Mode Voltage..................................... 0V to +VS – 2V

Integrator Differential Input Voltage ................................... –0.3V to +0.3V

V

Out (short-circuit).................................................................Indefinite

REF

Operating Temperature Range ......................................... –40°C to +85°C

Storage Temperature...................................................... –40°C to +125°C

Lead Temperature (soldering, 10s)................................................ +300°C

Stresses above these ratings may permanently damage the device. Expo­sure to absolute maximum rating conditions for extended periods may affect
device reliability.

S

PIN # NAME DESCRIPTION

1 NC Not Connected
2 Disable Input logic Low for normal operation. Input logic

High to disable the VFC121. Has internal pull­down, for normal operation if not connected.

3V

T

Temperature compensation voltage proportional
to absolute temperature. Typically 298mV at
room temperature (298°K), with a change of

1mV per °C (°K).
4 Gnd Sense Defines ground for the internal voltage reference.
5C

OS

6V

REF

One-shot capacitor is connected between here

and ground to set full scale output frequency.

Output from the internal band-gap voltage

reference, typically 2.6V. Can be used

externally to set levels or excite sensors.
7 NC Not Connected
8 Gnd Ground
9 Comp In Comparator In

10 Int Out Integrator Out
11 +V

12 –V

IN

IN

Non-inverting input of the integrating op amp.

The input signal is applied here.

Inverting input of the integrating op amp. C

connected between here and the integrator

output (pin 10), and R

here and ground.

13 +V

14 f

S

OUT

Supply voltage connected here. Range is +4.5V

to +36V.

Frequency output pin. This is the output of an

open-collector transistor, and an external pull-

up circuit should be used to generate the appro-

priate logic levels.

is connected between

IN

is

INT

PACKAGE INFORMATION

MODEL PACKAGE NUMBER

PACKAGE DRAWING

VFC121AP 14-Pin Plastic DIP 010
VFC121BP 14-Pin Plastic DIP 010

NOTE: (1) For detailed drawing and dimension table, please see end of data

sheet, or Appendix D of Burr-Brown IC Data Book.

(1)

3

VFC121