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

LP8900

SNVS542C – MAY 2008 – REVISED JULY 2013

www.ti.com

Figure 18. Effect of DC bias on Capacitance Value.

As an example Figure 18 shows a typical graph showing a comparison of capacitor case sizes in a Capacitance

vs. DC Bias plot. As shown in the graph, as a result of the DC Bias condition, the capacitance value may drop

below the minimum capacitance value given in the recommended capacitor table. 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 (e.g. 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 will change significantly above or below 25°C.

Tantalum capacitors are less desirable than ceramic for use as output capacitors because they are more

expensive when comparing equivalent capacitance and voltage ratings in the 1 µF to 4.7 µF range. Another

important consideration is that tantalum capacitors have higher ESR values than equivalent size ceramics. This

means that while it may be possible to find a tantalum capacitor with an ESR value within the stable range, it

would have to be larger in capacitance (which means bigger and more costly) than a ceramic capacitor with the

same ESR value. It should also be noted that the ESR of a typical tantalum will increase about 2:1 as the

temperature goes from 25°C down to -40°C, so some guard band must be allowed.

Enable Control

The LP8900 may be switched ON or OFF by a logic input at the ENABLE pin.A high voltage at this pin will turn

the device on. When the enable pin is low, the regulator output is off and the device typically consumes 3 nA.

A 3-M

able to swing above and below the specified turn-on/off voltage thresholds listed in the ELECTRICAL

DSBGA Mounting

The DSBGA package requires specific mounting techniques which are detailed in the TI Application Note (AN-

1112) SNVA009. Referring to the section Surface Mount Technology (SMT) Assenbly Considerations, it should

be noted that the pad style which must be used with the 6 pin package is NSMD (non-solder mask defined) type.

For best results during assembly, alignment ordinals on the PCB may be used to facilitate placement of the

DSBGA device.

10

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