LP2983_15 Datasheet, PDF (9/18 Pages) Texas Instruments – LP2983 Micropower 150 mA Voltage Regulator in SOT-23 Package For Output Voltages ≤ 1.2V Designed for Use with Very Low ESR Output Capacitors

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C_OUT = 2.2µF
Ceramic to ESR Pin
LP2983
SNVS170C – OCTOBER 2001 – REVISED APRIL 2013
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
be used, the ON/OFF input should be tied to V_IN to keep the regulator output on at all times.
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
V_ON/OFF. To prevent mis-operation, the turn-on (and turn-off) voltage signals applied to the ON/OFF input must
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
is in the range between the specified turn-on and turn-off voltages listed under the electrical specification V_ON/OFF
(see Electrical Characteristics).
Copyright © 2001–2013, Texas Instruments Incorporated
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