LD1117 ST Microelectronics, LD1117 Datasheet - Page 17

• Manufacturer Part Number: LD1117
• Description: LOW DROP FIXED AND ADJUSTABLE POSITIVE VOLTAGE REGULATORS
• Manufacturer: ST Microelectronics

Figure 10: Post-Regulated Dual Supply
LD1117 ADJUSTABLE: APPLICATION NOTE
The LD1117 ADJUSTABLE has a thermal
stabilized 1.25±0.012V reference voltage between
the OUT and ADJ pins. I
max.) and I
R1 is normally fixed to 120 . From figure 7 we
obtain:
V
+V
In normal application R2 value is in the range of
few kohm, so the R2 x I
considered in the V
above expression becomes:
OUT
REF
= V
/R1) = V
REF
ADJ
+ R2 (I
REF
is 1µA typ. (5µA max.).
(1 + R2 / R1) + R2 x I
ADJ
OUT
ADJ
DJ
+I
R1
calculation; then the
product could not be
is 60µA typ. (120µA
) = V
REF
+ R2 (I
ADJ
.
ADJ
V
In order to have the better load regulation it is
important to realize a good Kelvin connection of
R1 and R2 resistors. In particular 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.8).
OUT
= V
REF
(1 + R2 / R1).
LD1117 SERIES
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