CIRRUS VRE505K

VRE505
VRE505
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Precision Voltage Reference
Features
♦ +5 V Output, ± 1.0 mV (.02%)
♦ Temperature Drift: 1 ppm/ºC
♦ Low Noise: 3 μVP-P (0.1-10 Hz)
♦ Industry Standard Pinout: 8-pin Surface Mount
Package
♦ Excellent Line Regulation: 6 ppm/V Typ.
♦ Output Trim Capability
DESCRIPTION
The VRE505 is a low cost, high precision +5 V reference. The device is ideal for upgrading systems that
use lower performance references.
The device provides ultrastable +5 V output with ±0.5
mV (.01%) initial accuracy and a temperature coefficient of 0.6 ppm/ºC. This improvement in accuracy is
made possible by a unique, patented multipoint laser
compensation technique. Significant improvements
have been made in other performance parameters as
well, including initial accuracy, warm-up drift, line regulation, and long-term stability, making the VRE505 the
most accurate reference available.
For enhanced performance, the VRE505 has an external trim option for users who want less than 0.01% initial error. For ultra low noise applications, an external
capacitor can be attached between the noise reduction pin and the ground pin. A reference ground pin is
provided to eliminate socket contact resistance errors.
The VRE505 is recommended for use as a reference
for 14, 16, or 18 bit D/A converters which require an
external precision reference. The device is also ideal
for calibrating scale factor on high resolution A/D converters. The VRE505 offers superior performance over
monolithic references.
Figure 1. BLOCK DIAGRAM
Selection Guide
Model
VRE505K
Initial Error Temp. Coeff.
(mV)
(ppm/ºC)
±1.0
2.0
Temp. Range
(ºC)
-40ºC to +85ºC
8-pin Surface Mount
Package Style GF
VRE505DS
http://www.cirrus.com
Copyright © Cirrus Logic, Inc. 2009
(All Rights Reserved)
AUG 20091
APEX - VRE505DSREVC
VRE505
P r o d u c t I n n o v a t i o nF r o m
1. Characteristics and Specifications
ELECTRICAL Specifications
Vps = +15V, T = +25ºC, RL = 10KΩ Unless Otherwise Noted.
Parameter
Min
Typ
±13.5
±15
Max
Units
ABSOLUTE RATINGS
Power Supply
±22
V
Operating Temperature
-40
+85
ºC
Storage Temperature
-65
+150
ºC
Short Circuit Protection
Continuous
OUTPUT VOLTAGE
VRE505
+5.0
Temperature Sensor Voltage
(Note 1)
V
630
OUTPUT VOLTAGE ERRORS
Initial Error
(Note 2)
±1.0
Warmup Drift
TMIN - TMAX
(Note 3)
ppm
2.0
Long-Term Stability
Noise (0.1 - 10Hz)
mV
2
(Note 4)
ppm/ºC
6
ppm/1000hrs.
3
µVpp
OUTPUT CURRENT
Range
±10
mA
REGULATION
Line
6
Load
3
10
ppm/mA
ppm/V
10
mV
OUTPUT ADJUSTMENT
Range
POWER SUPPLY CURRENT (Note 5)
+PS
5
7
mA
NOTES:
1. The temp. reference TC is 2.1 mV/ºC
2. The specified values are without external trim.
3. The temperature coefficient is determined by the box method using the following formula:
VMAX – VMIN
TC =
x 106
VNOMINAL x (TMAX – TMIN)
2
4. The specified values are without the external noise reduction capacitor.
5. The specified values are unloaded.
VRE505DS
VRE505
P r o d u c t I n n o v a t i o nF r o m
2. TYPICAL PERFORMANCE CURVES
VOUT vs. TEMPERATURE
Temperature oC
VRE505K
QUIESCENT CURRENT VS. TEMP
Temperature oC
JUNCTION TEMP. RISE VS. OUTPUT CURRENT
Output Current (mA)
PSRR VS. FREQUENCY
Frequency (Hz)
3. THEORY OF OPERATION
The following discussion refers to the Block Diagram. 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 noninverting
input of the operational amplifier which amplifies the voltage to produce a 5.0 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’ 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.
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, this device 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.
VRE505DS
3
VRE505
P r o d u c t I n n o v a t i o nF r o m
The proper connection of the VRE505 series voltage references with the optional trim resistor for initial error and
the optional capacitor for noise reduction is shown below. The VRE505 reference has the ground terminal brought
out on two pins (pin 4 and pin 7) which are connected together internally. This allows the user to achieve greater
accuracy when using a socket. Voltage references have a voltage drop across their power supply ground pin due to
quiescent current flowing through the contact resistance. If the contact resistance was constant with time and temperature, this voltage drop could be trimmed out. When the reference is plugged into a socket, this source of error
can be as high as 20 ppm. By connecting pin 4 to the power supply ground and pin 7 to a high impedance ground
point in the measurement circuit, the error due to the contact resistance can be eliminated. If the unit is soldered
into place, the contact resistance is sufficiently small that it does not effect performance. Pay careful attention to the
circuit layout to avoid noise pickup and voltage drops in the lines.
EXTERNAL CONNECTIONS
+ VIN
V TEMP OUT
2
OPTIONAL
NOISE REDUCTION
CAPACITOR
CN
1µF
3
8
6
VRE505
5
7
PIN CONFIGURATION
4
+ VOUT
10KΩ
N/C
1
+VIN
2
TEMP
3
GND
4
VRE505
TOP
VIEW
8
NOISE
REDUCTION
7
REF. GND
6
VOUT
5
TRIM
OPTIONAL
FINE TRIM
ADJUSTMENT
REF. GND
Contacting Cirrus Logic Support
For all Apex Precision Power product questions and inquiries, call toll free 800-546-2739 in North America.
For inquiries via email, please contact [email protected]
International customers can also request support by contacting their local Cirrus Logic Sales Representative.
To find the one nearest to you, go to www.cirrus.com
IMPORTANT NOTICE
Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject
to change without notice and is provided "AS IS" without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant
information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale
supplied at the time of order acknowledgment, including those pertaining to warranty, indemnification, and limitation of liability. No responsibility is assumed by Cirrus
for the use of this information, including use of this information as the basis for manufacture or sale of any items, or for infringement of patents or other rights of third
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does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale.
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VRE505DS