參數(shù)資料
型號(hào): LP2978AIM5X-3.8
廠商: NATIONAL SEMICONDUCTOR CORP
元件分類: 基準(zhǔn)電壓源/電流源
英文描述: SUBMINIATURE PC BOARD RELAY
中文描述: 3.8 V FIXED POSITIVE LDO REGULATOR, 0.225 V DROPOUT, PDSO5
封裝: SOT-23, SOP-5
文件頁(yè)數(shù): 6/7頁(yè)
文件大小: 102K
代理商: LP2978AIM5X-3.8
Application Hints
(Continued)
It should also be noted that the ESR of a typical Tantalum will
increase about 2:1 as the temperature goes from 25C down
to 40C, so some guard band must be allowed.
ON/OFF INPUT OPERATION
The LP2978 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
. To prevent
mis-operation, the turn-on (and turn-off) voltage signals ap-
plied 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 Electri-
cal Characteristics).
REVERSE INPUT-OUTPUT VOLTAGE
The PNP power transistor used as the pass element in the
LP2978 has an inherent diode connected between the regu-
lator output and input. During normal operation (where the
input voltage is higher than the output) this diode is
reverse-biased.
However, if the output is pulled above the input, this diode
will turn ON and current will flow into the regulator output. In
such cases, a parasitic SCR can latch which will allow a high
current to flow into V
IN
(and out the ground pin), which can
damage the part.
In any application where the output may be pulled above the
input, an external Schottky diode must be connected from
V
to V
(cathode on V
, anode on V
), to limit the re-
verse voltage across the LP2978 to 0.3V (see Absolute
Maximum Ratings).
L
www.national.com
6
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