LT6650

9

6650f

Figure 9. Typical Configuration of LT6650 as Adjustable Positive

Shunt Reference

Figure 10. Typical Configuration of LT6650 as Adjustable

Negative Shunt Reference

APPLICATIO S I FOR ATIO

stepbetween100

µAand200µAinFigure7.Loadstepsettling

occurs in about 0.5ms or less (to

±0.2%).

Output Adjustment

If the LT6650 is to be used as a 400mV reference, then the

output and feedback pins may be tied together without any

scale-setting components as shown in the front-page

application circuit. Setting the output to any higher voltage

is a simple matter of selecting two feedback resistors to

configure the non-inverting gain of the internal operational

connected between the OUT pin and the FB pin, and a gain

resistor values are related to the output voltage by the

following relationship:

increases at twice the resistor tolerance, high accuracy

resistors or resistor networks are recommended. The

output voltage may be set to any level from 400mV up to

350mV below the supply voltage with source or sink

capability.

Noise Reduction Capacitor

In applications involving the use of resistive feedback for

reference scaling, the intrinsic reference noise is amplified

along with the DC level. To minimize noise amplification,

the use of a 1nF feedback capacitor is recommended, as

shown in Figure 8 and other circuits with scaling resistors.

Shunt Reference Operation

The circuits shown in Figure 9 and Figure 10 form adjust-

able shunt references. Along with the external bias resistor

operation for outputs between 1.4V and 18V (positive or

somewhat higher in magnitude than the desired reference

6650 F09

10

µF

OUT

IN

FB

GND

LT6650

2

45

1

1nF

6650 F10

10

µF

OUT

IN

FB

GND

LT6650

2

45

1

1nF

Figure 8. Typical Configuration for Output Voltages

Greater than 0.4V

6650 F08

1

µF

1

µF

1nF

OUT

IN

FB

GND

LT6650

2

45

1

1k

Figure 7. Output Response to Current-Sinking Load Step

(100

µA to 200µA)

6650 F07

10mV/DIV

AC

200

µA

100

µA