LT1963 datasheet(15/28 Pages) LINER

15 / 28 page

LT3089

3089f

For more information www.linear.com/LT3089

APPLICATIONS INFORMATION

In some extreme cases, capacitors or series RC networks

may be required on both the LT3089’s input and output to

stabilize the circuit. Figure 6 depicts a general application

using input and output capacitor networks rather than

an input-to-output capacitor. As the input of the current

source tends to be high impedance, placing a capacitor

on the input does not have the same effect as placing a

capacitoronthelowerimpedanceoutput.Capacitorsinthe

range of 0.1µF to 1µF usually provide sufficient bypassing

on the input, and the value of input capacitance may be

increased without limit. Pay careful attention to using low

ESR input capacitors with long input lines (see the Stabil-

ity and Input Capacitance section for more information).

Using Ceramic Capacitors

Give extra consideration to the use of ceramic capacitors.

Ceramic capacitors are manufactured with a variety of di-

electrics, each with different behavior across temperature

and applied voltage. The most common dielectrics used

are specified with EIA temperature characteristic codes of

Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are

good for providing high capacitances in a small package,

but they tend to have strong voltage and temperature

coefficients as shown in Figures 7 and 8. When used with

a 5V regulator, a 16V 10μF Y5V capacitor can exhibit an

effective value as low as 1μF to 2μF for the DC bias voltage

appliedandovertheoperatingtemperaturerange.TheX5R

and X7R dielectrics result in more stable characteristics

and are more suitable for use as the output capacitor.

The X7R type has better stability across temperature,

while the X5R is less expensive and is available in higher

values. Care still must be exercised when using X5R and

X7R capacitors. The X5R and X7R codes only specify

operating temperature range and maximum capacitance

change over temperature. Capacitance change due to DC

bias with X5R and X7R capacitors is better than Y5V and

Z5U capacitors, but can still be significant enough to drop

capacitor values below appropriate levels. Capacitor DC

bias characteristics tend to improve as component case

size increases, but expected capacitance at operating

voltage should be verified.

Figure 8. Ceramic Capacitor DC Bias Characteristics

Figure 7. Ceramic Capacitor Temperature Characteristics

Figure 6. Input and/or Output Capacitors May

Be Used for Compensation

3089 F06

SET

OUT

–

LT3089

50µA

IOUT

RSET

ROUT

COUT OR

VIN

COUT

ROUT

CIN

RIN

TEMPERATURE (°C)

–50

–20

–40

–60

–80

–100

3089 F07

–25

100

125

Y5V

X5R

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10µF

DC BIAS VOLTAGE (V)

3089 F08

–20

–40

–60

–80

–100

X5R

Y5V

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10µF

LT1963 Datasheet(PDF) 15 Page - Linear Technology

LT1963 Datasheet(HTML) 15 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 25 26 27 28

Datasheet Download

Link URL