vre402 Rhopoint Components, vre402 Datasheet - Page 19

• Manufacturer Part Number: vre402
• Description: Precision Dual Reference
• Manufacturer: Rhopoint Components

VRE410
THEORY OF OPERATION
below. 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
10.000V output. The gain is determined by the
networks R1 and R2: G=1 + R2/R1. The 6.3V zener
diode is used because it is the most stable diode
over time and temperature.
regulated output voltage through R3. This feedback
arrangement provides a closely regulated zener
current. This current 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.
compensation technique is not well suited for wide
temperature ranges.
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 then adjusting the slope, Thaler Corporation
produces
temperature ranges.
FIGURE 2
The following discussion refers to the schematic
The zener operating current is derived from the
Thaler Corporation has developed a nonlinear
temperature
a
very
function
stable
DISCUSSION OF PERFORMANCE
voltage
is
nonlinear
over
wide
this
ground terminal brought out on two pins (pin 6 and 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 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 VRE400 series voltage references have the
VRE410DS REV. A MAY 1996