7

This equation is correct due to the configuration of the bandgap reference. The bandgap voltage is relative to

the output, as seen in the block diagram. Traditional regulators normally have the reference voltage relative to

ground and have a different V

equation.

OUT

Resistor values are not critical because ADJ(adjust) has a high input impedance, but use resistors of 470kW or

less for best results. A capacitor from ADJ to ground provides greatly improved noise performance.

Figure 5. Ultra-Low- Noise Adjustable Voltage Application

Figure 5 includes the optional 470pF noise bypass capacitor from ADJ to GND to reduce output noise.

Dual-Supply Operation

When used in dual supply systems where the regulator load is returned to a negative supply, the output voltage

must be diode clamped to ground.

Typical Characteristics

0

-20

-40

-60

-80

-100

10

100

1k

10k

100k

1M

10M

Figure 6. Power Supply Rejection Ratio

FREQUENCY(Hz)

V

= 6V

IN

V

= 5V

OUT

I

=100mA

OUT

C

= 1µF

OUT

0

-20

-40

-60

-80

-100

10

100

1k

10k

100k

1M

10M

Figure 7. Power Supply Rejection Ratio

FREQUENCY(Hz)

V

= 6V

IN

V

= 5V

OUT

I

=100mA

OUT

C

= 2.2µF

OUT

C

= 0.01µF

BYP

320

280

240

200

160

120

80

40

0

0

40

80

120

160

Figure 8. Dropout Voltage vs.

Output Current

OUTPUT CURRENT (mA)

125°C

25°C

-40°C

Figure 9. Noise Performance

FREQUENCY(Hz)

10

1

0.1

0.01

0.001

0.0001

10

100

1k

10k

100k

1M

10M

100mA

10mA

1mA

V

=5V

OUT

C

=10µF

OUT

electrolytic

C

=10nF

BYP

R1

R2

1

2

3

4

5

470pF

FC6156 150mA Low - Noise LDO Regulator