VRE3025 ETC1 [List of Unclassifed Manufacturers], VRE3025 Datasheet - Page 5

• Manufacturer Part Number: VRE3025
• Description: Low Cost Precision Reference
• Manufacturer: ETC1 [List of Unclassifed Manufacturers]

PIN DESCRIPTION
THEORY OF OPERATION
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 2.500V 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.
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.
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.
resistance so it has a negligible effect on long term
stability. Figure 3 shows the proper connection of the
VRE3025 series voltage references with the optional trim
resistor for initial error and the optional capacitor for noise
reduction.
Figure 2 Functional Block Diagram
The following discussion refers to the schematic in
The current source provides a closely regulated zener
Thaler
This network is less than 2% of the overall network
1,3,7
2
4
5
6
8
Corporation
R1
N.C.
Vin
GND
TRIM
OUT
NR
R2
8
Internally connected. Do not use
Positive power supply input
Ground
External trim input. Leave open if
not used.
Voltage reference output
Noise Reduction
4
has
R3
R4
developed
+
-
2
5
a
nonlinear
6
BASIC CIRCUIT CONNECTION
Figure 3 shows the proper connection of the VRE3025
voltage reference with the optional trim resistor for initial
error and optional capacitor for noise reduction.
attention to the layout. A low resistance star configuration
will reduce voltage errors, noise pickup, and noise
coupled from the power supply.
connected to a single point to minimize interconnect
resistances.
To achieve the specified performance, pay careful
Optional Noise
Figure 3 External Connections
Reduction
Capacitor
C
N
1µF
8
VRE3025
+ V
2
4
IN
6
5
Commons should be
10k
+ V
Optional Fine
Trim Adjustment
VRE3025DS REV.D JULY 2000
OUT