Single Voltage Reference vs. Dual Voltage Reference - III

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Single Voltage Reference vs. Dual Voltage Reference - III [Copy link]

Now let’s look at other design considerations for these three solutions: space occupied and cost.

Space occupancy and cost

In addition to system performance, PCB area requirements can be critical in high-density applications. An overview of the total PCB space for each solution is given in Figure 1 (without considering decoupling capacitors).

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Table 1 below shows a simple calculation of the required space (considering only the device body size). By providing dual outputs from an integrated solution with a package size of 4.64 mm2, the REF2030 reduces the total space occupied by 83% and 67% relative to Solution 1 and Solution 2, respectively. From a cost perspective, the REF2030 is only $1.4, which is 52% and 30% lower than Solutions 1 and 2, respectively.

Table 1: Space occupancy and cost

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in conclusion

Solution 1
consists of two independent voltage references. Solution 1 is very straightforward and easy to implement. However, its disadvantages are also obvious: the voltage options are limited and there is no direct drift tracking between the outputs. In addition, the two low drift, high precision references used in Solution 1 are very expensive.

Although Solution 2
requires more components and occupies more board space, Solution 2 is less expensive than Solution 1 and has better drift tracking. However, the accuracy of VBIAS in Solution 2 is less accurate than Solution 1 because it depends on the drift of VREF, the voltage divider, and the buffer amplifier. On the plus side, Solution 2 is more flexible in designing different bias voltages, in which VBIAS ≠ VREF/2.

Solution 3

The most significant difference of Solution 3 is that it is a single-chip solution. This design has the best initial accuracy, lower cost, and smaller PCB space. In fact, Solution 3 has 90% better output matching than Solution 2, occupies 67% less space, and costs 30% less. In other words, if your design goal is a low-drift system and you don’t want to spend too much to get high-precision performance, Solution 3 ( REF2030 ) would be a good choice.

Table 2: Final comparison results

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