UTCLD1117 datasheet(11/12 Pages) UTC

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UTCLD1117/A LINEAR INTEGRATED CIRCUIT

UTC UNISONIC TECHNOLOGIES CO., LTD.

QW-R102-006,H

LD1117/A ADJUSTABLE APPLICATION NOTE

The LD1117/A ADJUSTABLE has a thermal stabilized 1.25

±0.012V reference voltage between the OUT and ADJ

pins. IADJ is 60µA typ. (120µA max.) and ∆IADJ is 1µA typ. (5µA max.).

R1 is normally fixed to 120

Ω. From figure 7 we obtain:

VOUT=VREF+R2(IADJ + IR1)=VREF + R2(IADJ + VREF / R1)=VREF(1+R2/R1) + R2 x IADJ.

In normal application R2 value is in the range of few Kohm,, so the R2 X IADJ product could not be considered in the

VOUT calculation; then the above expression becomes: VOUT=VREF(1+R2/R1)

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 Fig. 8)

FIG.7 Adjustable Output Voltage Application Circuit

FIG.8 Adjustable Output Voltage Application with improved Ripple Rejection.

UTCLD1117 Datasheet(PDF) 11 Page - Unisonic Technologies