0

1.0

2.0

3.0

4.0

5.0

DC BIAS (V)

0402, 6.3V, X5R

0603, 10V, X5R

100

80

60

40

20

13

LP8900

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SNVS542E – MAY 2008 – REVISED JUNE 2016

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Other ceramic types such as Y5V and Z5U are less suitable owing to their inferior temperature characteristics.

(See Capacitor Characteristics.)

It is also recommended that the output capacitor is placed within 1 cm of the output pin and returned to a clean,

low impedance, ground connection.

It is possible to use tantalum or film capacitors at the device output, OUT, but these are not as attractive for

reasons of size and cost. (See Capacitor Characteristics.)

9.2.2.4 No-Load Stability

The LP8900 remains stable and in regulation with no external load. This is an important consideration in some

circuits, for example CMOS RAM keep-alive applications.

9.2.2.5 Capacitor Characteristics

The LP8900 is designed to work with ceramic capacitors on the input and outputs to take advantage of the

benefits they offer. For capacitance values around 1 µF, ceramic capacitors give the circuit designer the best

design options in terms of low cost and minimal area.

For both input and output capacitors, careful interpretation of the capacitor specification is required to ensure

correct device operation. The capacitor value can change greatly dependant on the conditions of operation and

capacitor type.

In particular, to ensure stability, the output capacitor selection must take account of all the capacitor parameters,

to ensure that the specification is met within the application. Capacitance value can vary with DC bias conditions

as well as temperature and frequency of operation. Capacitor values may also show some decrease over time

due to aging. The capacitor parameters are also dependant on the particular case size with smaller sizes giving

poorer performance figures in general.

Figure 12. Effect of DC Bias on Capacitance Value

As an example Figure 12 shows a typical graph showing a comparison of capacitor case sizes in a capacitance

vs. DC bias plot. As shown in Figure 12, as a result of the DC bias condition, the capacitance value may drop

below the minimum capacitance value given in Table 2. Note that the graph shows the capacitance out of spec

for the 0402 case size capacitor at higher bias voltages. It is therefore recommended that the capacitor

manufacturers' specifications for the nominal value capacitor are consulted for all conditions as some capacitor

sizes (for example, 0402) may not be suitable in the actual application. Ceramic capacitors have the lowest ESR

values, thus making them best for eliminating high frequency noise. The ESR of a typical 4.7-µF ceramic

capacitor is in the range of 20 m

Ω to 40 mΩ, which easily meets the ESR requirement for stability for the

LP8900. The temperature performance of ceramic capacitors varies by type. Capacitor type X7R is specified with

a tolerance of ±15% over the temperature range –55°C to +125°C. The X5R has a similar tolerance over the

reduced temperature range of –55°C to +85°C. Some large value ceramic capacitors (4.7 µF) are manufactured

with Z5U or Y5V temperature characteristics, which can result in the capacitance dropping by more than 50% as

the temperature varies from 25°C to 85°C. Therefore, X7R or X5R types are recommended in applications where

the temperature changes significantly above or below 25°C.