VRE202 データシートの表示（PDF） - Cirrus Logic
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VRE202 Datasheet PDF : 4 Pages
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2. TYPICAL PERFORMANCE CURVES
VOUT vs. TEMPERATURE
0.25
-0.25
VRE202
VOUT vs. TEMPERATURE
0.2
-0.2
Temperature oC
VRE202C
Temperature oC
VRE202CA
QUIESCENT CURRENT VS. TEMP
JUNCTION TEMP. RISE VS. OUTPUT CURRENT
PSRR VS. FREQUENCY
Temperature oC
Output Current (mA)
Frequency (Hz)
3. THEORY OF OPERATION
The following discussion refers to the block diagram in Figure 1. A FET current source is used to bias a 6.3 V zener
diode. The zener voltage is divided by the resistor network R1 and R2. This voltage is then applied to the noninvert-
ing input of the operational amplifier which amplifies the voltage to produce a 2.5 V output. The gain is determined
by the resistor networks R3 and R4: G=1 + R4/R3. The 6.3 V 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’ volt-
age 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 tem-
perature 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. Then by adjusting
the slope, a very stable voltage over wide temperature ranges is produced. 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, a voltage reference is produced that also has very good long term stability.
VRE202DS
3
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