LD2127AL-AD-AA3-D-R datasheet(4/6 Pages) UTC

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LD2127/A

Preliminary

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

4 of 6

www.unisonic.com.tw

QW-R102-054.a



APPLICATION NOTE of LD2127/A ADJUSTABLE

The LD2127/A adjustable has a reference voltage of between the OUT and ADJ pins. IADJ is 7μA typ. (10μA

max.) and

IADJ is 0.3μA typ. (2µA max.).

R1 is normally fixed to 1.2kΩ.

From figure 1 we obtain:

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

Usually R2 value is in the range of few KΩ, 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. 2)

The UTC LD2127/A also supports MLCC. See Fig.3 for adjustable output.

OUT

ADJ

UTC LD2127/A

10µF

1.2kΩ

VIN

VOUT

VREF

Fig.1 Adjustable Output Voltage Application Circuit

Fig.2 Adjustable Output Voltage Application with improved Ripple Rejection.

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