LTC1150 datasheet(20/24 Pages) LINER

20 / 24 page

LTC2758

2758fb

For more information www.linear.com/LTC2758

applicaTions inForMaTion

Table 7. Partial List of LTC Precision References Recommended

for Use with the LTC2758 with Relevant Specifications

REFERENCE

INITIAL

TOLERANCE

TEMPERATURE

DRIFT

0.1Hz to 10Hz

NOISE

LT1019A-5,

LT1019A-10

±0.05% max

5ppm/°C max

12µVP-P

LT1236A-5,

LT1236A-10

±0.05% max

5ppm/°C max

3µVP-P

LT1460A-5,

LT1460A-10

±0.075% max

10ppm/°C max

20µVP-P

LT1790A-2.5

±0.05% max

10ppm/°C max

12µVP-P

LTC6652A-5

±0.05% max

5ppm/°C max

2.8ppmP-P

LTC6655A-2.5

LTC6655A-5

±0.025% max

2ppm/°C max

0.25ppmP-P

As precision DAC applications move to 18-bit perfor-

mance, reference output voltage noise may contribute a

dominant share of the system’s noise floor. This in turn can

degrade system dynamic range and signal-to-noise ratio.

Care should be exercised in selecting a voltage reference

with as low an output noise voltage as practical for the

system resolution desired. Precision voltage references

like the LT1236 or LTC6655 produce low output noise in

the 0.1Hz to 10Hz region, well below the 18-bit LSB level

in 5V or 10V full-scale systems. However, as the circuit

bandwidths increase, filtering the output of the reference

may be required to minimize output noise.

Grounding

As with any high-resolution converter, clean grounding

is important. A low-impedance analog ground plane is

necessary, as are star grounding techniques. Keep the

board layer used for star ground continuous to minimize

ground resistances; that is, use the star-ground concept

without using separate star traces. The IOUT2 pins are

of particular concern; INL will be degraded by the code-

dependent currents carried by the IOUT2XF and IOUT2XS

pins if voltage drops to ground are allowed to develop.

The best strategy here is to tie the pins to the star ground

plane by multiple vias located directly underneath the part.

Alternatively, the pins may be routed to the star ground

point if necessary; join the force and sense pins together

at the part and route one trace for each channel of no more

than 30 squares of 1oz copper.

In the rare case in which neither of these alternatives is

practicable, a force/sense amplifier should be used as a

ground buffer (see Figure 4). Note, however, that the volt-

age offset of the ground buffer amp directly contributes to

the effects on accuracy specified in Table 5 under ‘VOS1’.

The combined effects of the offsets can be calculated by

substituting the total offset from IOUT1X to IOUT2XS for

VOS1 in the equations.

LTC1150 Datasheet(PDF) 20 Page - Linear Technology

LTC1150 Datasheet(HTML) 20 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Datasheet Download

Link URL