VRE306 CIRRUS [Cirrus Logic], VRE306 Datasheet - Page 3

• Manufacturer Part Number: VRE306
• Description: Precision Voltage Reference
• Manufacturer: CIRRUS [Cirrus Logic]

VRE306
P r o d u c t I n n o v a t i o n F r o m
2. TYPICal PERFORMaNCE CuRVES
V
vs. TEMPERATURE
V
vs. TEMPERATURE
OUT
OUT
Temperature
o
C
Temperature
o
C
VRE306A
VRE306C
PSRR VS. FREQUENCY
QUIESCENT CURRENT VS. TEMP
JUNCTION TEMP. RISE VS. OUTPUT CURRENT
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 6.0V 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. By adjusting the
slope, a very stable voltage is produced 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.
VRE306DS
3