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LT3668

3668fa

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APPLICATIONS INFORMATION

COMMON

Ceramic Capacitor Characteristics

Give extra consideration to the use of ceramic capacitors.

Manufacturers make ceramic capacitors with a variety of

dielectrics, each with different behavior across tempera-

ture and applied voltage. The most common dielectrics

are specified with EIA temperature characteristic codes

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

provide high C-V products in a small package at low cost,

but exhibit strong voltage and temperature coefficients, as

can be seen for Y5V in Figures 6 and 7. 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

applied, and over the operating temperature range. The

X5R and X7R dielectrics yield much more stable charac-

teristics and are more suitable for use as input and output

capacitors. The X7R type works over a wider temperature

range and has better temperature stability, while the X5R

is less expensive and is available in higher values. Still

exercise care when using X5R and X7R capacitors; the

X5R and X7R codes only specify operating temperature

rangeandmaximumcapacitancechangeovertemperature.

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

toimproveascomponentcasesizeincreases,butexpected

capacitance at operating voltage should be verified.

Figure 6. Ceramic Capacitor DC Bias Characteristics

Figure 7. Ceramic Capacitor Temperature Characteristics

DC BIAS VOLTAGE (V)

3668 F06

–20

–40

–60

–80

–100

X5R

Y5V

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10µF

TEMPERATURE (°C)

–50

–20

–40

–60

–80

–100

3668 F07

–25

100

125

Y5V

X5R

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10µF

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