ld1117av28 STMicroelectronics, ld1117av28 Datasheet - Page 14

• Manufacturer Part Number: ld1117av28
• Description: Low Drop Fixed And Adjustable Positive Voltage Regulators
• Manufacturer: STMicroelectronics

6
Figure 9.
Figure 10. Adjustable output voltage application with improved ripple rejection
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LD1117A Adjustable: Application note
The LD1117 Adjustable has a thermal stabilized 1.25±0.012V reference voltage between
the OUT and ADJ pins. I
R1 is normally fixed to 120Ω . 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 10µF electrolytic capacitor
placed in parallel to the R2 resistor (see
Adjustable output voltage application
ADJ
OUT
OUT
.
= V
= V
REF
REF
+ R2 (I
(1 + R2 / R1).
ADJ
OUT
ADJ
+I
R1
calculation; then the above expression becomes:
is 60µA typ. (120µA max.) and ΔI
) = V
REF
Figure 6.
+ R2 (I
Figure
we obtain:
ADJ
9.).
+V
REF
/R
1
) = V
ADJ
REF
is 1µA typ. (5µA max.).
(1 + R2 / R
ADJ
product could not
1
) + R2 x