6

LTC1065

CC

HARA TERISTICS

A

TYPICALPERFOR

CE

INPUT FREQUENCY (kHz)

0

45

40

35

30

25

20

15

10

5

0

1065 G17

621

3

918

15

12

HORIZONTAL: 0.1ms/DIV, VERTICAL: 2V/DIV

SQUARE WAVE

1065 G16

Transient Response

Group Delay

PI FU CTIO S

Power Supply Pins (Pins 6, 3, N Package)

The positive and negative supply pin should be bypassed

with a high quality 0.1

µFceramiccapacitor.Inapplications

where the clock pin (5) is externally swept to provide

several cutoff frequencies, the output DC offset variation

is minimized by connecting an additional 1

µF solid tanta-

lum capacitor in parallel with the 0.1

µF disc ceramic. This

technique was used to generate the graphs of the output

DC offset variation versus clock; they are illustrated in the

Typical Performance Characteristics section.

When the power supply voltage exceeds

±7V, and when

ground) connect a signal diode between the positive

supply pin and ground to prevent latch-up (see Typical

Applications).

Ground Pin (Pin 2, N Package)

The ground pin merges the internal analog and digital

ground paths. The potential of the ground pin is the

reference for the internal switched-capacitor resistors,

and the reference for the external clock. The positive input

of the internal op amp is also tied to the ground pin.

For dual supply operation, the ground pin should be

connected to a high quality AC and DC ground. A ground

plane, if possible, should be used. A poor ground will

degrade DC offset and it will increase clock feedthrough,

noise and distortion.

A small amount of AC current flows out of the ground pin

whether or not the internal oscillator is used. The fre-

quency of the ground current equals the frequency of the

clock. The average value of this current is approximately

55

µA, 110µA, 170µA for ±2.5V, ±5V and ±7.5V supplies

respectively.

For single supply operation, the ground pin should be

preferably biased at half supply (see Typical Applications).

of output DC offset voltage or to introduce a desired output

output pin equals two.

Any DC voltage applied to this pin will reflect at the output

pin of the filter multiplied by two.

pin is typically 10pA.

ground; AC signals applied to this pin will degrade the filter

response.