LP3983

SNVS213A – MAY 2004 – REVISED MARCH 2013

www.ti.com

CAPACITOR CHARACTERISTICS

The LP3983 is designed to work with ceramic capacitors on the output to take advantage of the benefits they

offer. For capacitance values in the range of 1µF to 4.7µF range, ceramic capacitors are the smallest, least

expensive and have the lowest ESR values (which makes them best for eliminating high frequency noise). The

ESR of a typical 1µF ceramic capacitor is in the range of 20 m

Ω to 40 mΩ, which easily meets the ESR

requirement for stability by the LP3983.

The temperature performance of ceramic capacitors varies by type. Larger value ceramic capacitors may be

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, which 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

1µF to 4.7µF 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 OPERATION

The LP3983 may be switched ON or OFF by a logic input at the ENABLE pin, VEN. 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 <

1µA. If the application does not require the shutdown feature, the VEN pin should be tied to VIN to keep the

regulator output permanently on. To ensure proper operation, the signal source used to drive the VEN input must

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

Characteristics section under VIL and VIH.

DSBGA MOUNTING

The DSBGA package requires specific mounting techniques which are detailed in Application Note AN-1112,

(SNVA009).

Referring to the section PCB Layout, it should be noted that the pad style which must be used with the 5 pin

package is NSMD (non-solder mask defined) type.

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

DSBGA device.

DSBGA LIGHT SENSITIVITY

Exposing the DSBGA device to direct sunlight may cause mis-operation of the device. Light sources such as

Halogen lamps can effect electrical performance if brought near to the device.

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

fluorescent lighting used inside most buildings has very little effect on the output voltage of the device. Tests

carried out on a DSBGA test board showed a negligible effect on the regulated output voltage when brought

within 1cm of a fluorescent lamp. A deviation of less than 0.1% from nominal output voltage was observed.

8

Submit Documentation Feedback

Copyright © 2004–2013, Texas Instruments Incorporated

Product Folder Links: LP3983