LT3063 datasheet(14/22 Pages) LINER

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LT3063 Series

3063fa

For more information www.linear.com/LT3063

Output Capacitance

The LT3063 regulator is stable with a wide range of output

capacitors. The ESR of the output capacitor affects stabil-

ity, most notably with small capacitors. Use a minimum

output capacitor of 3.3µF with an ESR of 3Ω or less to

prevent oscillations. The LT3063 is a micropower device

and output load transient response is a function of output

capacitance.Largervaluesofoutputcapacitancedecrease

the peak deviations and provide improved transient re-

sponseforlargerloadcurrentchanges.Bypasscapacitors,

used to decouple individual components powered by the

LT3063, will increase the effective output capacitor value.

For applications with large load current transients, a low

ESR ceramic capacitor in parallel with a bulk tantalum

capacitor often provides an optimally damped response.

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

shown in Figures 4 and 5. 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 characteristics and are

more suitable for use as the output capacitor. The X7R

type works over a wider temperature range and has better

temperaturestability,whiletheX5Rislessexpensiveandis

availableinhighervalues.Carestillmustbeexercisedwhen

using X5R and X7R capacitors; the X5R and X7R codes

only specify operating temperature range and maximum

capacitancechangeovertemperature.Capacitancechange

due to DC bias with X5R and X7R capacitors is better than

Y5VandZ5Ucapacitors,butcanstillbesignificantenough

to drop capacitor values below appropriate levels. Capaci-

tor DC bias characteristics tend to improve as component

case size increases, but expected capacitance at operating

voltage should be verified.

APPLICATIONS INFORMATION

Voltage and temperature coefficients are not the only

sources of problems. Some ceramic capacitors have a

piezoelectric response. A piezoelectric device generates

DC BIAS VOLTAGE (V)

3063 F04

–20

–40

–60

–80

–100

X5R

Y5V

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10µF

TEMPERATURE (°C)

–50

–20

–40

–60

–80

–100

3063 F05

–25

100

125

Y5V

X5R

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10µF

Figure 4. Ceramic Capacitor DC Bias Characteristics

Figure 5. Ceramic Capacitor Temperature Characteristics

Figure 6. Noise Resulting from Tapping on a Ceramic Capacitor

4ms/DIV

3063 F06

VOUT

500µV/DIV

VOUT = 0.6V

COUT = 10µF

CREF/BYP = 10nF

ILOAD = 100mA

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