ADP7112 datasheet(26/47 Pages) AD

26 / 47 page

Data Sheet

LT3046

analog.com

Rev 0

26 of 47

meets these requirements. While the LT3046 is robust enough not to oscillate if the recommended layout is not

followed, depending on the actual layout, phase and gain margin, noise, and PSRR performance can degrade.

Figure 69. COUT and CSET Connections for Best Performance

Stability and Output Capacitance

The LT3046 requires an output capacitor for stability. Given its high bandwidth, Analog Devices recommends low

ESR and ESL ceramic capacitors. A minimum of 4.7μF capacitance with an ESR of less than 20mΩ and an ESL of less

than 2nH is required for stability.

Given the high PSRR and low-noise performance attained using a single 4.7μF ceramic-output capacitor, larger

values of output capacitors are not necessary. However, these capacitors can still improve the performance. See

the Typical Performance Characteristics section for additional information. Moreover, larger value output

capacitance decreases peak-output deviations during a load transient. Note that bypass capacitors used to

decouple individual components powered by the LT3046 increase the effective-output capacitance.

Give extra consideration to the type of ceramic capacitors used. The capacitors are manufactured with a variety of

dielectrics, each with different behaviors across temperature and applied voltage. The most common dielectrics

used are specified with Electronic Industries Alliance (EIA) temperature characteristic codes of Z5U, Y5V, X5R, and

X7R. The Z5U and Y5V dielectrics are good for providing high capacitance in small packages, but these dielectrics

tend to have stronger voltage and temperature coefficients as shown in Figure 70 and Figure 71. When used with a

5V regulator, a 16V, 10μF Y5V capacitor can exhibit an effective value as low as 1μF to 3μF for the DC bias voltage

applied over the operating temperature range.

CIN

100µA

EN/UV

PGFB

VIN

SET

GND

ILIM

OUTS

OUT

LT3046

VOUT

IOUT(MAX)

200mA

CSET

RSET

COUT

DEMO BOARD

PCB LAYOUT

ILLUSTRATES

4-TERMINAL

CONNECTION

TO COUT

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