ld1117dtc STMicroelectronics, ld1117dtc Datasheet - Page 26

• Manufacturer Part Number: ld1117dtc
• Description: Low Drop Fixed And Adjustable Positive Voltage Regulators
• Manufacturer: STMicroelectronics

7
Figure 11. Adjustable output voltage application
Figure 12. Adjustable output voltage application with improved ripple rejection
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LD1117 adjustable: application note
The LD1117 Adjustable has a thermal stabilized 1.25 ± 0.012 V reference voltage between
the OUT and ADJ pins. I
R1 is normally fixed to 120 Ω . From
V
I
In normal application R2 value is in the range of few kΩ , so the R2 x I
be considered in the V
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 10 µF electrolytic capacitor
placed in parallel to the R2 resistor (see
ADJ
OUT
OUT
.
= V
= V
REF
REF
+ R2 (I
(1 + R2 / R1).
ADJ
OUT
ADJ
+I
R1
calculation; then the above expression becomes:
is 60 µA typ. (120 µA max.) and ΔI
) = V
REF
Figure 10
+ R2 (I
Figure
ADJ
we obtain:
11).
+V
REF
/R
1
) = V
ADJ
REF
is 1 µA typ. (5 µA max.).
(1 + R2 / R
ADJ
product could not
1
) + R2 x