VRE302-6 데이터 시트보기 (PDF) - Unspecified

부품명

상세내역

제조사

VRE302-6

Low Cost Precision Reference

Unspecified 

DISCUSSION OF PERFORMANCE

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 2.048V 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.

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 VRE302-6

series voltage references with the optional trim resistor for

initial error. The VRE302-6 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.

VRE302-6

FIGURE 2

FIGURE 3

EXTERNAL CONNECTIONS

OPTIONAL

NOISE REDUCTION

CN

1µF

CAPACITOR

+ VIN

V TEMP OUT

2

3

8

6

VRE302-6

5

7

4

+ VOUT

10kΩ

OPTIONAL

FINE TRIM

ADJUSTMENT

REF. GND

VRE302-6DS REV. B MAY 2001

Share Link: