Product Innovation From
VRE104
2. TYPICAL PERFORMANCE GRAPHS
V
OUT
vs. TEMPERATURE
V
OUT
vs. TEMPERATURE
V
OUT
vs. TEMPERATURE
V
OUT
vs. TEMPERATURE
0.49
0.4
0.69
0.6
-0.49
-0.4
-0.69
-0.6
Temperature
o
C
VRE104C
Temperature
o
C
VRE104CA
Temperature
o
C
VRE104M
Temperature
o
C
VRE104MA
QUIESCENT CURRENT VS. TEMP
JUNCTION TEMP. RISE VS. OUTPUT CURRENT
PSRR VS. FREQUENCY
Temperature
o
C
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 4.5 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 method leaves a residual error over wide temperature
ranges.
To remove this residual error, a nonlinear compensation network of thermistors and resistors has been developed
that is used in the VRE104 series references. This proprietary network eliminates most of the nonlinearity in the
voltage vs. temperature function. By then adjusting the slope, the VRE104 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.
VRE104DS
3
CIRRUS [ CIRRUS LOGIC ]
