LT3074AVPBF datasheet(34/62 Pages) AD

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Data Sheet

LT3074

analog.com

Rev 0.

34 of 62

Figure 84. Ceramic Capacitor DC Bias Characteristics

Figure 85. Ceramic Capacitor Temperature Characteristics

The X5R and X7R dielectrics result in more stable characteristics and thus are more suitable for the LT3074. The X7R

dielectric has better stability across temperature, while the X5R is less expensive and is available in higher values.

Nonetheless, care must still be exercised when using X5R and X7R capacitors. The X5R and X7R codes only specify

operating temperature range and the maximum capacitance change over temperature. While capacitance changes

due to DC bias for X5R and X7R is better than Y5V and Z5U dielectrics, it can still be significant enough to drop the

capacitance below sufficient levels. As shown in Figure 86, capacitor DC bias characteristics tend to improve as

component case size increases. However, verification of expected capacitance at the operating voltage is highly

recommended. Due to its good voltage coefficient in small case sizes, Analog Devices recommends using the Murata

GCM series ceramic capacitors.

Figure 86. Capacitor Voltage Coefficient for Different Case Sizes

In addition to DC bias and temperature variation noted above, variation in effective capacitance with applied AC

voltage needs to be considered as well. Ceramic capacitors are typically specified for an AC ripple of 1V. Effective

capacitance decreases with lower AC ripple voltages. Effective capacitance decreases by 30% or more with the very

low AC ripple at the output of the LT3074. Contact the respective ceramic capacitor vendor for more information on

temperature, DC bias voltage, and AC ripple voltage effects when selecting a capacitor to meet the minimum

capacitance requirements of the LT3074.

DC BIAS VOLTAGE (V)

–100

–80

–60

–40

–20

X5R

Y5V

BOTH CAPACITORS ARE 16V

1210 CASE SIZE, 10µF

TEMPERATURE (°C)

–100

–80

–60

–40

–20

–15

–35

–55

X5R

Y5V

BOTH CAPACITORS ARE 25V

1210 CASE SIZE, 10µF

DC BIAS (V)

–100

–80

–60

–40

–20

MURATA: 25V, 10%

X7R/X7S, 10µF CERAMIC

GRM SERIES, 0805, 1.45mm THICK

GRM SERIES, 1206, 1.8mm THICK

GRM SERIES, 1210, 2.2mm THICK

GRM SERIES, 1206, 1.9mm THICK

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