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LD1117EL-18-TA3-B-R View Datasheet(PDF) - Unisonic Technologies

Part NameLD1117EL-18-TA3-B-R UTC
Unisonic Technologies UTC
DescriptionLOW DROP FIXED AND ADJUSTABLE POSITIVE VOLTAGE REGULATORS
LD1117EL-18-TA3-B-R Datasheet PDF : 13 Pages
First Prev 11 12 13
LD1117E
LINEAR INTEGRATED CIRCUIT
„ APPLICATION NOTE of LD1117E ADJUSTABLE
The LD1117E adjustable has a reference voltage of between the OUT and ADJ pins. IADJ is 60μA typ. (120µA
max.) and ΔIADJ is 1μA typ. (5µA max.).
R1 is normally fixed to 120Ω.
From figure 4 we obtain:
VOUT=VREF+R2(IADJ+IR1)=VREF + R2(IADJ+VREF/R1)=VREF(1+R2/R1) + R2 x IADJ.
Usually R2 value is in the range of few K, so the R2 X IADJ product could be neglected; then the above
expression becomes: VOUT=VREF(1+R2/R1)
For better load regulation, realize a good Kelvin connection of R1 and R2 is important. Particularly R1
connection must be realized very close to OUT and ADJ pin, while R2 ground connection must be placed as
near as possible to the negative Load pin. Ripple rejection can be improved by introducing a 10μF electrolytic
capacitor placed in parallel to the R2 resistor (See Fig. 5)
VIN
+
10µF
UTC LD1117E
IN
OUT
ADJ
R1
120
+
VREF
VOUT
10µF
R2
Fig.4 Adjustable Output Voltage Application Circuit
VIN
+
10µF
UTC LD1117E
IN
OUT
ADJ
R1
120
+
VREF
VOUT
10µF
+
10µF
R2
Fig.5 Adjustable Output Voltage Application with improved Ripple Rejection.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
11 of 13
QW-R102-040.A
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