vre402 precision dual reference description features the vre402 is a low cost, high precision, 2.5v reference. packaged in 14 pin dip or smt packages, the device is ideal for new designs that need a high performance reference. the device provides ultrastable 2.500v output with 0.250 mv (.01%) initial accuracy and a temperature coefficient of 0.6 ppm/c. this improvement in accuracy is made possible by a unique, patented multipoint laser compensation technique developed by thaler corporation. another key feature of this reference is the 0.3 mv maximum tracking error between the positive and negative output voltages over the operating temperature range. this is extremely important in high performance systems for reducing overall system errors. for designs which use the dip package in a socket, there is a reference ground pin to eliminate reference ground errors. the vre402 is recommended for use as a reference for high precision a/d and d/a converters which require an external precision reference. the device is ideal for calibrating scale factor on high resolution a/d converters. the vre402 offers superior performance over monolithic references. ? 2.500 v output 0.250 mv (.01%) ? temperature drift: 0.6 ppm/c ? low noise: 1.5 v pp (0.1-10hz) ? tracking error: 0.2 mv max. ? excellent line regulation: 6ppm/v typ. ? surface mount and dip packages figure 1 vre402ds rev. a may 1996 selection guide model temp. range c temp. coeff. ppm/ c vre402a 0.25 0.6 0c to +70c vre402b 0.40 1.0 0c to +70c vre402c 0.50 2.0 0c to +70c vre402j 0.25 0.6 -40c to +85c vre402k 0.40 1.0 -40c to +85c vre402l 0.50 2.0 -40c to +85c for package option add d for dip or s for surface mount to end of model number. initial error mv thaler corporation ? 2015 n. forbes boulevard ? tucson, az. 85745 ? (520) 882-4000 11 12 13 14 vre402 top view 1 2 3 4 n/c +v in gnd ref. gnd +v out pin configuration 5 6 7 10 9 8 - v out n/c - v in n/c n/c n/c n/c n/c n/c
model a/j b/k c/l parameter min typ max min typ max min typ max units absolute ratings power supply 13.5 15 22 * * * * * * v operating temp. ( a,b,c ) 0 +70 * * * * c operating temp. ( j,k,l ) -40 +85 * * * * c storage temperature -65 +150 * * * * c short circuit protection continuous * * output voltage vre402 2.5 * * v output voltage errors initial error 0.25 0.40 0.50 mv warmup drift 1 2 3 ppm t min - t max 0.6 1.0 2.0 ppm/ c tracking error 0.2 0.3 0.4 mv long-term stability 6 * * ppm/1000hrs noise (.1-10hz) 1.5 * * m vpp output current range 10 * * ma regulation line 3 10 * * * * ppm/v load 3 * * ppm/ma power supply currents +ps 7 9 * * * * ma -ps 4 6 * * * * ma vre402 notes: *same as a/j models. 1. the specified values are without external trim. 2. the temperature coefficient (tc) is determined by the box method using the following formula: v max - v min tc = x 10 6 v nominal x (t max -t min ) 3. the tracking error is the deviation between the positive and negative output over the operating temp. range. (1) (4) (2) (3) vre402ds rev. a may 1996 vps = 15v, t = 25c, rl = 10k w unless otherwise noted. electrical specifications 4. the specified values are unloaded.
typical performance curves vre402ds rev. a may 1996 quiescent current vs. temp temperature o c junction temp. rise vs. output current output current (ma) psrr vs. frequency frequency (hz) quiescent current vs. temp temperature o c junction temp. rise vs. output current output current (ma) psrr vs. frequency frequency (hz) temperature o c vre402a v out vs. temperature temperature o c vre402b v out vs. temperature v out vs. temperature temperature o c vre402c temperature o c vre402j v out vs. temperature temperature o c vre402k v out vs. temperature temperature o c vre402l v out vs. temperature positive output (typ) negative output (typ)
discussion of performance vre402ds rev. a may 1996 vre402 figure 2 theory of operation the following discussion refers to the schematic in figure 2 below. a fet current source is used to bias a 6.3v 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 2.500v output. the gain is determined by the resistor networks r3 and r4: g=1 + r4/r3. the 6.3v 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. thaler corporation has developed a nonlinear compensation network of thermistors and resistors that 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, thaler corporation 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. the vre402 reference has it?s ground brought out on two pins (pin 6 and 7) which are connected 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 20ppm. by connecting pin 7 to the power supply ground and pin 6 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.
dim min max min max dim min max min max a .114 .136 2.90 3.45 e .410 .435 10.4 11.0 b .018 .027 .460 .690 e1 .390 .415 9.91 10.5 b1 .047 .056 1.19 1.42 e2 .265 .270 6.73 6.86 b2 .097 .103 2.46 2.62 g1 .285 .315 7.24 8.00 c .009 .020 0.22 0.51 l .195 .225 4.95 5.72 d .690 .715 17.5 18.1 p .090 .110 2.29 2.79 d 1 .666 .680 16.9 17.2 q .050 .070 1.27 1.79 s .040 .060 1.02 1.52 inches millimeter inches millimeter vre402ds rev. a may 1996 mechanical figure 4 figure 3 dim min max min max dim min max min max a .114 .136 2.90 3.45 e .495 .526 12.5 13.3 b .098 .103 2.48 2.62 e1 .390 .415 9.91 10.5 b1 .047 .056 1.19 1.42 e2 .265 .270 6.73 6.86 c .103 .118 2.62 3.00 p .090 .110 2.29 2.79 c1 .009 .020 0.22 0.51 q .024 .035 0.61 .890 c2 .054 .062 1.37 1.57 s .040 .060 1.02 1.52 d .690 .715 17.5 18.1 d1 .666 .680 16.9 17.2 inches millimeter inches millimeter
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