p r o d u c t i n n o v a t i o n f r o m vre306 vre306ds description the vre306 is a low cost, high precision +6 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 +6 v output with 0.6 mv (.01%) initial accuracy and a temperature coeff - cient of 0.6 ppm/oc. this improvement in accuracy is made possible by a unique, patented multipoint laser compensation technique. signifcant improvements have been made in other performance parameters as well, including initial accuracy, warm-up drift, line regulation, and long-term stability, making the vre306 series the most accurate reference available in a stan - dard 8-pin smt package. for enhanced performance, the vre306 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 reduction pin and the ground pin. a reference ground pin is pro - vided to eliminate socket contact resistance errors. fea tures ? +6 v output, 0.6 mv (.01%) ? temperature drift: 0.6 ppm/oc ? low noise: 4 v p-p (0.1-10hz) ? industry standard pinout: 8-pin surface mount package ? excellent line regulation: 6 ppm/v typical ? output trim capability applica tions the vre306 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 vre306 offers su - perior performance over monolithic references. precision voltage reference vre306 p r o d u c t i n n o v a t i o n f r o m figure . block diagram copyright ? cirrus logic, inc. 2009 (all rights reserved) http://www.cirrus.com mar 2009 apex ? vre306dsrevc model initial error (mv) temp. coeff. (ppm/oc) temp. range (oc) VRE306A vre306c 0.6 1.2 0.6 2.0 0oc to +70oc 0oc to +70oc selection guide 8-pin surface mount package style gd
p r o d u c t i n n o v a t i o n f r o m vre306 2 vre306ds . characteristics and specifica tions electric al specifica tions v ps = 15v, t = +25oc, r l = 10k unless otherwise noted . model VRE306A vre306c parameter min typ max min typ max units absolute maximum ra tings power supply 14 15 16 * * * v operating temperature (a,c) 0 +70 * * oc storage temperature -65 +150 * * oc short circuit protection continuous * output vol t age vre306 +6.0 * v temp. sensor voltage (note 1) 630 * mv output vol t age errors initial error (note 2) 0.6 1.2 mv warmup drift 1 3 ppm t min - t max (note3) 0.6 2.0 ppm/oc long-term stability 6 * ppm/1000hrs. noise (0.1 - 10hz) (note 4) 4 * vpp output current range 10 ma regula tion line 6 10 * * ppm/v load 3 * ppm/ma output adjustment range 10 * mv power suppl y current (note 5) vre306 +ps 5 7 * * ma notes: * same as a models. 1. the temp. reference tc is 2.1 mv/ oc 2. the specifed values are without external trim. 3. the temperature coeffcient is determined by the box method using the following formula: 4. the specifed values are without the external noise reduction capacitor . 5. the specifed values are unloaded. v nominal x (t max ? t min ) v max ? v min t.c. = x 10 6
p r o d u c t i n n o v a t i o n f r o m vre306 vre306ds 3 2. typic al performance cu rves t em p erat u re o c v r e 30 6 a v out v s . tempe r a t ure v out v s . tempe r a t ure t em p erat u re o c vre306c q u i e s c e n t curr e n t v s . t e m p t em p erat u re o c j u n c t i on te m p . r i se vs . outpu t c u r r en t outpu t curr e nt ( m a ) p s rr v s . fr eq uenc y fr e qu e n c y (hz ) 3. th eory of opera tion 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 amplifer which amplifes 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.
p r o d u c t i n n o v a t i o n f r o m vre306 vre306ds the proper connection of the vre306 series voltage references with the optional trim resistor for initial error and the optional capacitor for noise reduction is shown below. the vre306 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 fowing 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 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 suffciently small that it does not effect performance. pay careful attention to the circuit layout to avoid noise pickup and voltage drops in the lines. extern al connections 8 4 6 5 + v o u t 2 + v in v r e30 6 10 kw c n 1 f opti o n a l noi s e r e duct i o n c a p a c i t o r opti o n a l fin e trim a dj u s t m e nt 3 v temp out 7 r ef . g n d 5 6 7 8 v r e30 6 top vie w 1 2 3 4 n/c + v in t emp g n d noi s e reduct i o n r ef . g n d v o u t trim cont acting 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 tucson.support@cirrus.com. international customers can also request support by contacting their local cirrus logic sales representative. to fnd 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, indemnifcation, 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 parties. this document is the property of cirrus and by furnishing this information, cirrus grants no license, express or implied under any patents, mask work rights, copyrights, trademarks, trade secrets or other intellectual property rights. cirrus owns the copyrights associated with the information contained herein and gives con - sent for copies to be made of the information only for use within your organization with respect to cirrus integrated circuits or other products of cirrus. 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. certain applications using semiconductor products may involve potential risks of death, personal injury, or severe prop - erty or environmental damage (critical applications). cirrus products are not designed, authorized or warranted to be suitable for use in products surgically implanted into the body, automotive safety or security devices, life support prod - ucts or other critical applications. inclusion of cirrus products in such applications is understood to be fully at the cus - tomers risk and cirrus disclaims and makes no warranty, express, statutory or implied, including the implied warranties of merchantability and fitness for particular purpose, with regard to any cirrus product that is used in such a manner. if the customer or customers customer uses or permits the use of cirrus products in critical applications, customer agrees, by such use, to fully indemnify cirrus, its officers, directors, employees, distributors and other agents from any and all liability, including attorneys fees and costs, that may result from or arise in connection with these uses. cirrus logic, cirrus, and the cirrus logic logo designs, apex precision power, apex and the apex precision power logo designs are trademarks of cirrus logic, inc. all other brand and product names in this document may be trademarks or service marks of their respective owners. pin configura tion
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