6

LTC1069-6

only. Table 1 shows the clock’s low and high level thresh-

old value for a dual or single supply operation. A pulse

generator can be used as a clock source provided the high

level ON time is greater than 0.42

waves less than 100kHz are not recommended for clock

frequencies because, excessive slow clock rise or fall

times generate internal clock jitter. The maximum clock

rise or fall time is 1

µs. The clock signal should be routed

from the right side of the IC package to avoid coupling into

any input or output analog signal path. A 1k resistor

between the clock source and the Clock Input (Pin 5) will

slow down the rise and fall times of the clock to further

reduce charge coupling (Figure 1).

Table 1. Clock Source High and Low Thresholds

POWER SUPPLY

HIGH LEVEL

LOW LEVEL

Dual Supply =

±5V

1.5V

0.5V

Single Supply = 10V

6.5V

5.5V

Single Supply = 5V

1.5V

0.5V

Single Supply = 3.3V

1.2V

0.5V

filter, and it can source 8mA or sink 1mA. The total

harmonic distortion of the filter will degrade when driving

coaxial cables or loads less than 20k without an output

buffer.

AGND

NC

1

2

3

4

8

7

6

5

1k

NC

CLK

LTC1069-6

ANALOG GROUND PLANE

DIGITAL

GROUND

PLANE

STAR

SYSTEM

GROUND

0.1

µF

0.1

µF

1069-6 F03

CLOCK

SOURCE

Figure 3. Connections for Dual Supply Operation

NC (Pins 3, 6): No Connection. Pins 3 and 6 are not

connected to any internal circuitry; they should be tied to

ground.

connected to the inverting input of an op amp through a

50k resistor.

CLK (Pin 5): Clock Input Pin. Any TTL or CMOS clock

source with a square wave output and 50% duty cycle

(

±10%) is an adequate clock source for the device. The

power supply for the clock source should not necessarily

be the filter’s power supply. The analog ground of the filter

should be connected to the clock’s ground at a single point

Temperature Behavior

The power supply current of the LTC1069-6 has a positive

temperature coefficient. The GBW product of its internal

op amps is nearly constant and the speed of the device

does not degrade at high temperatures. Figures 4a, 4b and

4c show the behavior of the passband of the device for

various supplies and temperatures. The filter has a pass-

band behavior which is temperature independent.

Figure 4a

FREQUENCY (kHz)

1

1

2

17

1069-6 F04a

0

–1

–2

5

9

13

319

7

11

15

21

85

°C

–40

°C