VRE304
VRE304DS 1
VRE304
DESCRIPTION
The VRE304 is a low cost, high precision +4.5 V refer-
ence. Available in an industry standard 8-pin surface
mount package, the device is ideal for upgrading sys-
tems that use lower performance references.
The device provides ultrastable +4.5 V output with
±0.45 mV (.01%) initial accuracy and a temperature
coefcient of 0.6 ppm/°C. This improvement in accu-
racy is made possible by a unique, patented multipoint
laser compensation technique. Signicant improve-
ments have been made in other performance param-
eters as well, including initial accuracy, warm-up drift,
line regulation, and long-term stability.
For enhanced performance, the VRE304 has an exter-
nal trim option for users who want less than 0.01% ini-
tial error. For ultra low noise applications, an external
capacitor can be attached between the noise reduc-
tion pin and the ground pin. A reference ground pin is
provided to eliminate socket contact resistance errors.
FEATURES
♦ +4.5 V Output, ± 0.450 mV (.01%)
♦ Temperature Drift: 0.6 ppm/ºC
♦ Low Noise: 3μVp-p (0.1-10Hz)
♦ Industry Standard Pinout: 8-Pin Surface Mount
Package
♦ Excellent Line Regulation: 6 ppm/V Typical
♦ Output Trim Capability
APPLICATIONS
The VRE304 is recommended for use as a refer-
ence for 14, 16, or 18 bit D/A converters which re-
quire an external precision reference. The device
is also ideal for calibrating scale factor on high
resolution A/D converters. The VRE304 offers su-
perior performance over monolithic references.
Precision Voltage Reference
VRE304
Figure 1. BLOCK DIAGRAM
Model
Initial Error
(mV)
Temp. Coeff.
(ppm/ºC)
Temp. Range
(ºC)
VRE304CS ±0.90 2.0 0ºC to +70ºC
SELECTION GUIDE
8-pin Surface Mount
Package Style GD
Copyright © Apex Microtechnology, Inc. 2012
(All Rights Reserved)
www.apexanalog.com SEP 2012
VRE304DS REVI
VRE304
2 VRE304DS
1. CHARACTERISTICS AND SPECIFICATIONS
ELECTRICAL SPECIFICATIONS
VPS = +15V, T = +25ºC, RL = 10KΩ Unless Otherwise Noted.
Parameter Min Typ Max Units
ABSOLUTE MAXIMUM RATINGS
Power Supply +13.5 +15 +22 V
Operating Temperature 0 +70 ºC
Storage Temperature -65 +150 ºC
Short Circuit Protection Continuous
OUTPUT VOLTAGE
VRE304 (Note 1) +4.5 V
Temp. Sensor Voltage 630 mV
OUTPUT VOLTAGE ERRORS
Initial Error (Note 2) ±0.90 mV
Warmup Drift 3 ppm
TMIN - TMAX (Note3) 2.0 ppm/ºC
Long-Term Stability 6 ppm/1000hrs.
Noise (0.1 - 10Hz) (Note 4) 3 µVpp
OUTPUT CURRENT
Range ±10 mA
REGULATION
Line 6 10 ppm/V
Load 3 ppm/mA
OUTPUT ADJUSTMENT
Range 10 mV
POWER SUPPLY CURRENT (Note 5)
VRE304 +PS 5 7 mA
NOTES:
1. The temp. reference TC is 2.1 mV/ ºC
2. The specied values are without external trim.
3. The temperature coefcient is determined by the box method using the following formula:
4. The specied values are without the external noise reduction capacitor.
5. The specied values are unloaded.
VNOMINAL x (TMAX – TMIN)
VMAX – VMIN
T.C. = x 106
VRE304
VRE304DS 3
2. TYPICAL PERFORMANCE CURVES
VOUT vs. TEMPERATURE
Temperature oC
VRE304CS
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 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 amplier which amplies 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 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.
VRE304
4 VRE304DS
The proper connection of the VRE304 series voltage references with the optional trim resistor for initial error and
the optional capacitor for noise reduction is shown below. The VRE304 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 owing through the contact resistance. If the contact resistance was constant with time and tem-
perature, this voltage drop could be trimmed out. When the reference is plugged into a socket, this source of error
can be as high as 20ppm. 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 sufciently 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
8
4
6
5
+ VOUT
2
+ VIN
VRE304
10kΩ
CΝ
1µF
OPTIONAL
NOISE REDUCTION
CAPACITOR
OPTIONAL
FINE TRIM
ADJUSTMENT
3
VTEMP OUT
7
REF. GND
5
6
7
8
VRE304
TOP
VIEW
1
2
3
4
N/C
+VIN
TEMP
GND
NOISE
REDUCTION
REF. GND
VOUT
TRIM
PIN CONFIGURATION
NEED TECHNICAL HELP? CONTACT APEX SUPPORT!
For all Apex Microtechnology product questions and inquiries, call toll free 800-546-2739 in North America.
For inquiries via email, please contact apex.support@apexanalog.com.
International customers can also request support by contacting their local Apex Microtechnology Sales Representative.
To nd the one nearest to you, go to www.apexanalog.com
IMPORTANT NOTICE
Apex Microtechnology, Inc. has made every effort to insure the accuracy of the content contained in this document. However, the information is subject to change
without notice and is provided "AS IS" without warranty of any kind (expressed or implied). Apex Microtechnology reserves the right to make changes without further
notice to any specications or products mentioned herein to improve reliability. This document is the property of Apex Microtechnology and by furnishing this informa-
tion, Apex Microtechnology grants no license, expressed or implied under any patents, mask work rights, copyrights, trademarks, trade secrets or other intellectual
property rights. Apex Microtechnology owns the copyrights associated with the information contained herein and gives consent for copies to be made of the informa-
tion only for use within your organization with respect to Apex Microtechnology integrated circuits or other products of Apex Microtechnology. This consent does not
extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale.
APEX MICROTECHNOLOGY PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED TO BE SUITABLE FOR USE IN PRODUCTS USED FOR
LIFE SUPPORT, AUTOMOTIVE SAFETY, SECURITY DEVICES, OR OTHER CRITICAL APPLICATIONS. PRODUCTS IN SUCH APPLICATIONS ARE UNDER-
STOOD TO BE FULLY AT THE CUSTOMER OR THE CUSTOMER’S RISK.
Apex Microtechnology, Apex and Apex Precision Power are trademarks of Apex Microtechnolgy, Inc. All other corporate names noted herein may be trademarks
of their respective holders.
Copyright © Apex Microtechnology, Inc. 2012
(All Rights Reserved)
www.apexanalog.com SEP 2012
VRE304DS REVI
