VRE304C - Thaler Corporation

VRE304

Low Cost

Precision Reference

DESCRIPTION

FEATURES

The VRE304 is a low cost, high precision 4.5V

reference. Packaged in the industry standard 8

pin DIP, the device is ideal for upgrading systems

that use lower performance references.

The device provides ultrastable +4.500V output

with ±0.4500 mV (.01%) initial accuracy and a

temperature coefficient of 0.6 ppm/°C. This

improvement in accuracy is made possible by a

unique, patented multipoint laser compensation

technique developed by Thaler Corporation.

Significant improvements have been made in

other performance parameters as well, including

initial accuracy, warm-up drift, line regulation, and

long-term stability, making the VRE304 series the

most accurate reference available in the standard

8 pin DIP package.

For enhanced performance, the VRE304 has an

external trim option for users who want less than

0.01% initial error. For ultra low noise

applications, an external capacitor can be

attached between the noise reduction pin and the

ground pin. A reference ground pin is provided to

eliminate socket contact resistance errors.

VRE304

TOP

VIEW

N/C

+VIN

TEMP

GND

NOISE

REDUCTION

REF. GND

VOUT

TRIM

PIN CONFIGURATION

The VRE304 is recommended for use as a

reference for 14, 16, or 18 bit D/A converters

which require an external precision reference.

The device is also ideal for calibrating scale

factor on high resolution A/D converters. The

VRE304 offers superior performance over

monolithic references.

• 4.500 V OUTPUT ± 0.450 mV (.01%)

• TEMPERATURE DRIFT: 0.6 ppm/°C

• LOW NOISE: 3µV p-p (0.1-10Hz)

• INDUSTRY STD PINOUT- 8 PIN DIP OR

SURFACE MOUNT PACKAGE

•EXCELLENT LINE REGULATION: 6ppm/V Typ.

• OUTPUT TRIM CAPABILITY FIGURE 1

VRE304DS REV. C AUG. 1995

SELECTION GUIDE

Model

Temp.

Range

°C

Temp.

Coeff.

ppm/°C

VRE304A 0.45 0.6 0°C to +70°C

VRE304B 0.70 1.0 0°C to +70°C

VRE304C 0.90 2.0 0°C to +70°C

VRE304J 0.45 0.6 -40°C to +85°C

VRE304K 0.70 1.0 -40°C to +85°C

VRE304L 0.90 2.0 -40°C to +85°C

For package option add D for DIP or S for Surface

Mount to end of model number.

Initial

Error

RHOPOINT COMPONENTS LTD., Holland Road,Hurst Green, Oxted, Surrey, RH8 0AX. Tel: +44 (0)1883 717988

MODEL A/J B/K C/L

PARAMETER MIN TYP MAX MIN TYP MAX MIN TYP MAX UNITS

ABSOLUTE RATINGS

Power Supply +13.5 +15 +22 ****** V

Operating Temp. (A,B,C)0+70 * * * * °C

Operating Temp. (J,K,L)-40 +85 * * * * °C

Storage Temperature -65 +150 * * * * °C

Short Circuit Protection Continuous * *

OUTPUT VOLTAGE

VRE304 4.500 * * V

Temp. Sensor Voltage 630 * * mV

OUTPUT VOLTAGE ERRORS

Initial Error 0.45 0.70 0.90 mV

Warmup Drift 123ppm

Tmin - Tmax 0.6 1.0 2.0 ppm/ °C

Long-Term Stability 6* *ppm/1000hrs

Noise (.1-10Hz) 3* * µVpp

OUTPUT CURRENT

Range ±10 * * mA

REGULATION

Line 6 10 * * * * ppm/V

Load 3 * * ppm/mA

OUTPUT ADJUSTMENT

Range 10 * * mV

POWER SUPPLY CURRENTS

VRE304 +PS 5 7 * * * * mA

VRE304

NOTES: *Same as A/J Models.

1. The temp. reference TC is 2.1mV/ °C

2. The specified values are without external trim.

3. The temperature coefficient is determined by the box

method using the following formula:

Vmax - Vmin

T.C. = x 106

Vnominal x (Tmax-Tmin)

(1)

(5)

(2)

(3)

VRE304DS REV. C AUG. 1995

Vps =+15V, T = 25°C, RL = 10KΩ unless otherwise noted.

ELECTRICAL SPECIFICATIONS

4. The specified values are without the external

noise reduction capacitor.

5. The specified values are unloaded.

(4)

TYPICAL PERFORMANCE CURVES

Temperature oC

VRE304A

VOUT vs. TEMPERATURE

Temperature oC

VRE304B

VOUT vs. TEMPERATURE

VRE304DS REV. C AUG. 1995

VOUT vs. TEMPERATURE

Temperature oC

VRE304C

Temperature oC

VRE304J

VOUT vs. TEMPERATURE

Temperature oC

VRE304K

VOUT vs. TEMPERATURE

Temperature oC

VRE304L

VOUT vs. TEMPERATURE

QUIESCENT CURRENT VS. TEMP

Temperature oC

JUNCTION TEMP. RISE VS. OUTPUT CURRENT

Output Current (mA)

PSRR VS. FREQUENCY

Frequency (Hz)

DISCUSSION OF PERFORMANCE

VRE304DS REV. C AUG. 1995

THEORY OF OPERATION

The following discussion refers to the schematic in

figure 2 below. A FET current source is used to bias a

6.3V zener diode. The zener voltage is divided by the

resistor network R1 and R2. This voltage is then applied

to the noninverting input of the operational amplifier which

amplifies the voltage to produce a 4.500V output. The

gain is determined by the resistor networks R3 and R4:

G=1 + R4/R3. The 6.3V zener diode is used because it is

the most stable diode over time and temperature.

The current source provides a closely regulated zener

current, which determines the slope of the references’

voltage vs. temperature function. By trimming the zener

current a lower drift over temperature can be achieved.

But since the voltage vs. temperature function is

nonlinear this compensation technique is not well suited

for wide temperature ranges.

Thaler Corporation has developed a nonlinear

compensation network of thermistors and resistors that is

used in the VRE series voltage references. This

proprietary network eliminates most of the nonlinearity in

the voltage vs. temperature function. By adjusting the

slope, Thaler Corporation produces a very stable voltage

over wide temperature ranges.

VRE304

FIGURE 2

This network is less than 2% of the overall network

resistance so it has a negligible effect on long term

stability.

Figure 3 shows the proper connection of the VRE304

series voltage references with the optional trim resistor

for initial error and the optional capacitor for noise

reduction. The VRE304 reference has the ground

terminal brought out on two pins (pin 4 and pin 7) which

are connected together internally. This allows the user to

achieve greater accuracy when using a socket. Voltage

references have a voltage drop across their power

supply ground pin due to quiescent current flowing

through the contact resistance. If the contact resistance

was constant with time and temperature, this voltage

drop could be trimmed out. When the reference is

plugged into a socket, this source of error can be as high

as 20ppm. By connecting pin 4 to the power supply

ground and pin 7 to a high impedance ground point in the

measurement circuit, the error due to the contact

resistance can be eliminated. If the unit is soldered into

place, the contact resistance is sufficiently small that it

does not effect performance. Pay careful attention to the

circuit layout to avoid noise pickup and voltage drops in

the lines.

EXTERNAL CONNECTIONS

FIGURE 3

+ VOUT

+ VIN

VRE304 10kΩΩ

1µF

OPTIONAL

NOISE REDUCTION

CAPACITOR

OPTIONAL

FINE TRIM

ADJUSTMENT

V TEMP OUT

REF. GND

DIM MIN MAX MIN MAX DIM MIN MAX MIN MAX

A.115 .125 2.92 3.17 E.397 .403 10.0 10.2

B.018 .022 .457 .558 E1 .264 .270 6.70 6.85

B1 .046 .051 1.14 1.29 G1 .290 .310 7.36 7.87

B2 .098 .102 2.48 2.59 L.195 .215 4.95 5.46

C.009 .012 0.22 0.30 P.085 .095 2.15 2.41

D .397 .403 10.0 10.2 Q.055 .065 1.39 1.65

D 1 .372 .380 9.44 9.65 S.045 .055 1.14 1.39

INCHES MILLIMETER INCHES MILLIMETER

VRE304DS REV. C AUG. 1995

MECHANICAL

FIGURE 4

FIGURE 3

DIM MIN MAX MIN MAX DIM MIN MAX MIN MAX

A.115 .125 2.92 3.17 E .507 .513 12.8 13.0

B.098 .102 2.48 2.59 E1 .397 .403 10.0 10.2

B1 .046 .051 1.14 1.29 E2 .264 .270 6.70 6.85

C.107 .113 2.71 2.87 P .085 .095 2.15 2.41

C1 .009 .012 0.22 0.30 Q.020 .030 .508 .762

C2 .052 .058 1.32 1.47 S.045 .055 1.14 1.39

D.397 .403 10.0 10.2

D1 .372 .380 9.44 9.65

INCHES MILLIMETER INCHES MILLIMETER