LP2983

www.ti.com

SNVS170C – OCTOBER 2001 – REVISED APRIL 2013

Ceramic to ESR Pin

Figure 22.

The LP2983 requires a minimum of 2.2 µF on the output (output capacitor size can be increased without limit).

It is important to remember that capacitor tolerance and variation with temperature must be taken into

consideration when selecting an output capacitor so that the minimum required amount of output capacitance is

provided over the full operating temperature range. It should be noted that ceramic capacitors can exhibit large

changes in capacitance with temperature (see next section, Capacitor Characteristics).

The output capacitor must be located not more than 1 cm from the output pin and returned to a clean analog

ground via the ESR pin.

CAPACITOR CHARACTERISTICS

The LP2983 was designed to work with ceramic capacitors on the output to take advantage of the benefits they

offer: for capacitance values in the 2.2 µF to 4.7 µF range, ceramics are the least expensive and also have the

lowest ESR values (which makes them best for eliminating high-frequency noise).

One disadvantage of ceramic capacitors is that their capacitance can vary with temperature. Most large value

ceramic capacitors (

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

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

This could cause problems if a 2.2 µF capacitor were used on the output since it will drop down to approximately

1 µF at high ambient temperatures (which could cause the LP2983 to oscillate). If Z5U or Y5V capacitors are

used on the output, a minimum capacitance value of 4.7 µF must be observed.

A better choice for temperature coefficient in ceramic capacitors is X7R, which holds the capacitance within

±15%. Unfortunately, the larger values of capacitance are not offered by all manufacturers in the X7R dielectric.

ON/OFF INPUT OPERATION

The LP2983 is shut off by driving the ON/OFF input low, and turned on by pulling it high. If this feature is not to

To assure proper operation, the signal source used to drive the ON/OFF input must be able to swing above and

below the specified turn-on/turn-off voltage thresholds listed in the Electrical Characteristics section under

have a slew rate which is

≥ 40 mV/µs.

Caution: The regulator output voltage can not be guaranteed if a slow-moving AC (or DC) signal is applied that

(see Electrical Characteristics).

Copyright © 2001–2013, Texas Instruments Incorporated

Submit Documentation Feedback

9

Product Folder Links: LP2983