LP5900

SNVS358O – JULY 2005 – REVISED MAY 2013

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CAPACITOR CHARACTERISTICS

The LP5900 is designed to work with ceramic capacitors on the input and output to take advantage of the

benefits they offer. For capacitance values in the range of 0.47

μF to 4.7 μF, ceramic capacitors are the smallest,

least expensive and have the lowest ESR values, thus making them best for eliminating high frequency noise.

The ESR of a typical 0.47

μF ceramic capacitor is in the range of 20 mΩ to 40 mΩ, which easily meets the ESR

requirement for stability for the LP5900.

The temperature performance of ceramic capacitors varies by type and manufacturer. Most large value ceramic

capacitors (

≥ 2.2 µF) are manufactured with Z5U or Y5V temperature characteristics, which results in the

capacitance dropping by more than 50% as the temperature goes from 25°C to 85°C.

A better choice for temperature coefficient in a ceramic capacitor is X7R. This type of capacitor is the most stable

and holds the capacitance within ±15% over the temperature range. 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 0.47

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.

NO-LOAD STABILITY

The LP5900 will remain stable and in regulation with no external load.

ENABLE CONTROL

The LP5900 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 3nA.

regulator output permanently on. In this case the supply voltage must be fully established 500

μs or less to

ensure correct operation of the startup circuit. Failure to comply with this condition may cause a delayed startup

time of several seconds.

A 1M

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

DSBGA MOUNTING

The DSBGA package requires specific mounting techniques, which are detailed in Texas Instruments Application

Note AN-1112, SNVS009.

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

micro SMD device.

DSBGA LIGHT SENSITIVITY

Exposing the DSBGA device to direct light may cause incorrect operation of the device. Light sources such as

halogen lamps can affect electrical performance if they are situated in proximity to the device.

Light with wavelengths in the red and infra-red part of the spectrum has the most detrimental effect; thus, the

fluorescent lighting used inside most buildings has very little effect on performance.

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