VRE3025 Просмотр технического описания (PDF) - Cirrus Logic
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VRE3025 Datasheet PDF : 7 Pages
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Product Innova tionFrom
VRE3025
EXTERNAL CONNECTIONS
+ VIN
Optional Noise
Reduction
Capacitor
CN 1µF
2
8
6
VRE3025
5
4
+ VOUT
10kΩ
Optional Fine
Trim Adjustment
PIN DESCRIPTIONS
1, 3, 7 N. C. Internally connected. Do not use
2
VIN
Positive power supply input
4
GND Ground
5
TRIM External trim input. Leave open if not
used.
6
OUT
Voltage reference output
8
NR
Noise Reduction
4. BASIC CIRCUIT CONNECTION
To achieve the specified performance, pay careful attention to the layout. A low resistance star configuration will
reduce voltage errors, noise pickup, and noise coupled from the power supply. Commons should be connected to
a single point to minimize interconnect resistances.
5. TEMPERATURE PERFORMANCE
The VRE3025 is designed for applications where the initial error at room temperature and drift over temperature
are important to the user. For many instrument manufacturers, a voltage reference with a temperature coefficient
less than 1 ppm/°C makes it possible to not have to perform a system temperature calibration, a slow and costly
process.
Of the three TC specification methods (slope, butterfly, and box), the box method is used commonly used. A box
is formed by the min/max limits for the nominal output voltage over the operating temperature range. The equation
follows:
T.C. =
VMAX – VMIN
VNOMINAL x (TMAX – TMIN)
x 106
This method corresponds more accurately to the method of test and provides a closer estimate of actual error than
the other methods. The box method guarantees limits for the temperature error but does not specify the exact shape
and slope of the device under test.
A designer who needs a 14-bit accurate data acquisition system over the industrial temperature range (-40°C to
+85°C), will need a voltage reference with a temperature coefficient (TC) of 1.0 ppm/°C if the reference is allowed
to contribute an error equivalent to 1LSB. For 1/2LSB equivalent error from the reference you would need a volt-
age reference with a temperature coefficient of 0.5 ppm/°C. Figure 4 shows the required reference TC vs. delta T
change from 25°C for resolution ranging from 8 bits to 20 bits.
VRE3025DS
5
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