參數(shù)資料
型號: LM2991WG-QML
廠商: NATIONAL SEMICONDUCTOR CORP
元件分類: 基準電壓源/電流源
英文描述: Negative Low Dropout Adjustable Regulator
中文描述: 2 V-25 V ADJUSTABLE NEGATIVE LDO REGULATOR, 1 V DROPOUT, CDSO16
封裝: CERAMIC, SOIC-16
文件頁數(shù): 5/11頁
文件大?。?/td> 338K
代理商: LM2991WG-QML
Typical Performance Characteristics
(Continued)
Application Hints
EXTERNAL CAPACITORS
The LM2991 regulator requires an output capacitor to main-
tain stability. The capacitor must be at least 10 μF aluminum
electrolytic or 1 μF solid tantalum. The output capacitor’s
ESR must be less than 10
, or the zero added to the regu-
lator frequency response by the ESR could reduce the
phase margin, creating oscillations. The shaded area in the
Output Capacitor ESR graph indicates the recommended
ESR range.An input capacitor, of at least 1 μF solid tantalum
or 10 μF aluminum electrolytic, is also needed if the regulator
is situated more than 6 inches from the input power supply
filter.
MINIMUM LOAD
A minimum load current of 500 μA is required for proper op-
eration. The external resistor divider can provide the mini-
mum load, with the resistor from the adjust pin to ground set
to 2.4 k
.
SETTING THE OUTPUT VOLTAGE
The output voltage of the LM2991 is set externally by a resis-
tor divider using the following equation:
V
OUT
= V
REF
x (1 + R
2
/R
1
) (I
ADJ
x R
2
)
where V
= 1.21V. The output voltage can be pro-
grammed within the range of 3V to 24V, typically an even
Adjust Pin Current
DS011260-25
Low Voltage Behavior
DS011260-26
Maximum Power
Dissipation (TO-220)
DS011260-27
Maximum Power Dissipation
(TO-263) (See Note 3)
DS011260-28
Output Capacitor ESR Range
DS011260-5
www.national.com
5
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