LP5521 datasheet(37/48 Pages) TI1

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LP5521

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SNVS441H – JANUARY 2007 – REVISED MAY 2016

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8.2.1.2 Detailed Design Procedure

8.2.1.2.1

Capacitor Selection

The LP5521 requires 4 external capacitors for proper operation (CIN = COUT = 1 μF, CFLY1 = CFLY2 = 470 nF).

Surface-mount multi-layer ceramic capacitors are recommended. These capacitors are small, inexpensive and

have very low equivalent series resistance (ESR < 20 m

Ω typical). Tantalum capacitors, OS-CON capacitors,

and aluminum electrolytic capacitors are not recommended for use with the LP5521 due to their high ESR, as

compared to ceramic capacitors.

For most applications, ceramic capacitors with X7R or X5R temperature characteristic are preferred for use with

the LP5521. These capacitors have tight capacitance tolerance (as good as ±10%) and hold their value over

temperature (X7R: ±15% over –55°C to 125°C; X5R: ±15% over –55°C to 85°C).

Capacitors with Y5V or Z5U temperature characteristic are generally not recommended for use with the LP5521.

Capacitors with these temperature characteristics typically have wide capacitance tolerance (+80%, –20%) and

vary significantly over temperature (Y5V: +22%, –82% over –30°C to +85°C range; Z5U: +22%, –56% over

+10°C to +85°C range). Under some conditions, a nominal 1-

μF Y5V or Z5U capacitor could have a capacitance

of only 0.1

μF. Such detrimental deviation is likely to cause Y5V and Z5U capacitors to fail to meet the minimum

capacitance requirements of the LP5521.

The minimum voltage rating acceptable for all capacitors is 6.3 V. The recommended voltage rating of the output

capacitor is 10 V to account for DC bias capacitance losses.

NOTE

Some ceramic capacitors, especially those in small packages, exhibit a strong capacitance

reduction with the increased applied voltage (DC bias effect). The capacitance value can

fall below half of the nominal capacitance. Choose output and input capacitor with DC bias

voltage effect better than –50% at 5 V voltage (0.5

μF at 5 V).

Table 36. External Component Examples

MODEL

TYPE

VENDOR

VOLTAGE RATING

SIZE INCH (mm)

μF for COUT and CIN

C1005X5R1A105K

Ceramic X5R

TDK

10 V

0402 (1005)

ECJ0EB1A105M

Ceramic X5R

Panasonic

10 V

0402 (1005)

ECJUVBPA105M

Ceramic X5R, array of two

Panasonic

10 V

0504

470 nF for CFLY1-2

C1005X5R1A474K

Ceramic X5R

TDK

10 V

0402 (1005)

ECJ0EB0J474K

Ceramic X5R

Panasonic

10 V

0402 (1005)

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