LT6201 datasheet(16/22 Pages) LINER

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LTC2385-18

238518f

For more information www.linear.com/LTC2385-18

APPLICATIONS INFORMATION

Internal Reference with Internal Reference Buffer

To use the internal reference and internal reference buf-

fer, bypass REFIN to GND with a 0.1μF ceramic capacitor

(Figure 6). Bypass REFBUF to REFGND with a single 10μF

(X7R,0805size)ceramiccapacitor.TheREFBUFcapacitor

should be as close as possible to the LTC2385-18 package

to minimize wiring inductance. Do not place this capaci-

tor on the opposite side of the board. Adding a second,

smaller capacitor in parallel with the 10μF may degrade

performance and is not recommended.

Figure 7. Suggested REFBUF Bypass Capacitor Layout

Figure 8. Using the LTC6655-2.048 as an External Reference

shown in Figure 8. Linear Technology offers a portfolio of

high performance references designed to meet the needs

of many applications. With its small size, low power, and

high accuracy, the LTC6655-2.048 is well suited for use

with the LTC2385-18 when overdriving the internal ref-

erence. The LTC6655-2.048 offers 0.025% (max) initial

accuracy and 2ppm/°C (max) temperature coefficient for

highprecisionapplications.BypassingtheLTC6655-2.048

with a 2.7μF to 10μF ceramic capacitor close to the REFIN

pin is recommended.

Figure 7 shows a suggested layout for the REFBUF capaci-

tor. The capacitor should be connected to REFBUF and

REFGND through short, wide traces. REFGND should also

be connected with a wide trace to the grounded exposed

pad (Pin 33).

External Reference with Internal Reference Buffer

If more accuracy and/or lower drift is desired, REFIN can

be directly overdriven by an external 2.048V reference as

External Reference Buffer

The internal reference buffer can also be overdriven with

an external 4.096V reference at REFBUF as shown in

Figure 9. To do so, REFIN must be grounded to disable

the reference buffer. The external reference must have a

fast transient response and be able to drive the 0.5mA

to 0.9mA load at the REFBUF pin. The LTC6655-4.096 is

recommended when overdriving REFBUF.

238518 F08

REFGND

REFBUF

REFIN

2.7µF

LTC2385-18

REFGND

REFBUF

10µF

VIN

LTC6655-2.048

GND

SHDN

VOUT_F

VOUT_S

0.1µF

Figure 6. Configuration for Using the Internal Reference

Figure 5. LTC2385-18 Internal Reference Circuitry

238518 F05

2.048V

REFERENCE

ADC

CORE

REFGND

REFBUF

REFIN

15k

LTC2385-18

2×

238518 F06

REFGND

REFBUF

REFIN

0.1µF

LTC2385-18

REFGND

REFBUF

10µF

238518 F07

9 10 11 12

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