P r o d u c t I n n o v a t i o n F r o m

VRE100

VRE100DS

3

Model

Output (V)

Temperature

Operating Range

Volt Deviation (MaX)

VRE100C

VRE100CA

VRE100M

VRE100MA

+10

+10

+10

+10

-25°C to +85°C

-25°C to +85°C

-55°C to +125°C

-55°C to +125°C

±0.6mV

±0.3mV

±1.0mV

±0.5mV

VRE101C

VRE101CA

VRE101M

VRE100MA

-10

-10

-10

-10

-25°C to +85°C

-25°C to +85°C

-55°C to +125°C

-55°C to +125°C

±0.6mV

±0.3mV

±1.0mV

±0.5mV

VRE102C

VRE102CA

VRE102M

VRE102MA

±10

±10

±10

±10

-25°C to +85°C

-25°C to +85°C

-55°C to +125°C

-55°C to +125°C

±0.6mV

±0.3mV

±1.0mV

±0.5mV

SElECTION GuIDE

2. ThEORY OF OPERaTION

The following discussion refers to the block diagrams in Figure 1. In operation, approximately 6.3 volts is applied

to the noninverting input of the op amp. The voltage is amplified by the op amp to produce a 10.000 V output. The

gain is determined by the networks R1 and R2: G=1 + R2/R1. The 6.3 V zener diode is used because it is the most

stable diode over time and temperature.

The zener operating current is derived from the regulated output voltage through R3. This feedback arrangement

provides a closely regulated zener current. This current determines the slope of the references’ voltage vs. tempera-

ture 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.

A nonlinear compensation network of thermistors and resistors is used in the VRE series voltage references. This

proprietary network eliminates most of the nonlinearity in the voltage vs. temperature function. By then adjusting the

slope, this series 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. By using highly stable resistors in our

network, we produce a voltage reference that also has very good long term stability.

3. aPPlICaTION INFORMaTION

Page 5 shows the proper connection of the VRE100 series voltage reference with the optional trim resistors. When

trimming the VRE102, the positive voltage should be trimmed first since the negative voltage tracks the positive

side. Pay careful attention to the circuit layout to avoid noise pickup and voltage drops in the lines.

The VRE100 series voltage references have the ground terminal brought out on two pins (pin 6 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 20 ppm. By con-

necting pin 7 to the power supply ground and pin 6 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 doesn’t effect performance. The VRE series voltage references can be connected with or

without the use of pin 6 and still provide superior performance.

hermetic 14-pin Ceramic DIP

Package Style hC