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12

LTC1588/LTC1589/LTC1592

1588992fa

While not directly addressed by the simple equations in

Tables 2 and 3, temperature effects can be handled just as

easily for unipolar and bipolar applications. First, consult

an op amps data sheet to find the worst-case V

OS

and I

B

over temperature. Then, plug these numbers in the V

OS

and I

B

equations from Table 3 and calculate the tempera-

ture induced effects.

For applications where fast settling time is important, Appli-

cation Note 74, entitled 

Component and Measurement

Advances Ensure 16-Bit DAC Settling Time

, offers a thor-

ough discussion of 16-bit DAC settling time and op amp

selection.

Precision Voltage Reference Considerations

Much in the same way selecting an operational amplifier

for use with the LTC1592 is critical to the performance of

the system, selecting a precision voltage reference also

requires due diligence. The output voltage of the LTC1592

is directly affected by the voltage reference; thus, any

voltage reference error will appear as a DAC output voltage

error.

There are three primary error sources to consider when

selecting a precision voltage reference for 16-bit applica-

tions: output voltage initial tolerance, output voltage tem-

perature coefficient and output voltage noise.

Initial reference output voltage tolerance, if uncorrected,

generates a full-scale error term. Choosing a reference

APPLICA TIO S I FOR A TIO

WUUU

Table 4. Partial List of LTC Precision Amplifiers Recommended for Use with the LTC1588/LTC1589/LTC1592,

with Relevant Specifications

AMPLIFIER SPECIFICATIONS

VOLTAGE CURRENT SLEW GAIN BANDWIDTH t

SETTLING

POWER

V

OS

I

B

A

OL

NOISE NOISE RATE PRODUCT with LTC1592 DISSIPATION

AMPLIFIER mV nA V/mV nV/ Hz pA/ Hz V/ms MHz msmW

LT1001 25 2 800 10 0.12 0.25 0.8 120 46

LT1097 50 0.35 1000 14 0.008 0.2 0.7 120 11

LT1112 (Dual) 60 0.25 1500 14 0.008 0.16 0.75 115 10.5/Op Amp

LT1124 (Dual) 70 20 4000 2.7 0.3 4.5 12.5 19 69/Op Amp

LT1468 75 10 5000 5 0.6 22 90 2.5 117

LT1469 (Dual) 125 10 2000 5 0.6 22 90 2.5 123/Op Amp

()

5V

V

REF

()

5V

V

REF

()

16.5k

A

VOL1

V

OS1

(mV)

I

B1

(nA)

A

VOL1

(V/V)

V

OS2

(mV)

I

B2

(mV)

A

VOL2

(V/V)

V

OS1

¥ 2.4 ¥

I

B1

¥ 0.0003 ¥˚

A1 ¥

0

()

5V

V

REF

()

5V

V

REF

()

1.5k

A

VOL1

()

66k

A

VOL2

()

131k

A

VOL1

()

131k

A

VOL1

()

131k

A

VOL2

()

131k

A

VOL2

V

OS1

¥ 0.6 ¥

I

B1

¥ 0.00008 ¥˚

A2 ¥

0

()

5V

V

REF

()

5V

V

REF

V

OS1

¥ 13.2 ¥

I

B1

¥ 0.13 ¥˚

0

()

5V

V

REF

()

5V

V

REF

()

5V

V

REF

V

OS1

¥ 13.2 ¥

I

B1

¥ 0.0018 ¥

A5 ¥

V

OS2

¥ 26.2 ¥

I

B2

¥ 0.1 ¥

()

5V

V

REF

()

5V

V

REF

()

5V

V

REF

()

5V

V

REF

A3 ¥ V

OS1

¥ 19.8 ¥

I

B1

¥ 0.01 ¥˚

0

A4 ¥ V

OS2

¥ 13.1 ¥

A4 ¥ I

B2

¥ 0.05 ¥˚

A4 ¥

()

5V

V

REF

()

5V

V

REF

()

5V

V

REF

()

5V

V

REF

()

5V

V

REF

V

OS1

¥ 13.2 ¥

I

B1

¥ 0.0018 ¥

A5 ¥

V

OS2

¥ 26.2 ¥

I

B2

¥ 0.1 ¥

Table 3. Easy-to-Use Equations Determine Op Amp Effects on DAC Accuracy in All Output Ranges

Table 2. Variables for Each Output Range That Adjust the

Equations in Table 3

OUTPUT RANGE A1 A2 A3 A4 A5

5V 1.1 2 1

10V 2.2 3 1.5

–5V 2 2 1.2 1 1.5

–10V 4 4 1.2 1 2.5

–2.5V 1 1 1.6 1 1

—2.5V to 7.5V 1.9 3 1 0.5 1.5

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Canon Powershot SX20 IS Användarguide

Canon Powershot SX20 IS Användarguide

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