LTC1069-6

6

Rev. B

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PIN FUNCTIONS

for single supply operation, the internal biasing of Pin 1

allows optimum output swing. The AGND pin should be

buffered if used to bias other ICs. Figure 2 shows the

connections for single supply operation.

AGND

V+

V+

NC

VIN

VIN

VOUT

VOUT

V–

1

2

3

4

8

7

6

5

1k

NC

CLK

LTC1069-6

ANALOG GROUND PLANE

DIGITAL

GROUND

PLANE

0.47µF

0.1µF

1069-6 F02

CLOCK

SOURCE

STAR

SYSTEM

GROUND

V+, V– (Pins 2, 7): Power Supply Pins. The V+ (Pin 2)

and the V– (Pin 7, if used) should be bypassed with a

0.1µF capacitor to an adequate analog ground. The filter’s

power supplies should be isolated from other digital or

high voltage analog supplies. A low noise linear supply is

recommended. Switching power supplies will lower the

signal-to-noise ratio of the filter. Unlike previous mono-

lithic filters, the power supplies can be applied in any

order, that is, the positive supply can be applied before

the negative supply and vice versa. Figure 3 shows the

connection for dual supply operation.

AGND

V+

V+

NC

VIN

VIN

VOUT

VOUT

V–

V–

1

2

3

4

8

7

6

5

1k

NC

CLK

LTC1069-6

ANALOG GROUND PLANE

DIGITAL

GROUND

PLANE

STAR

SYSTEM

GROUND

0.1µF

0.1µF

1069-6 F03

CLOCK

SOURCE

Figure 2. Connections for Single Supply Operation

Figure 3. Connections for Dual Supply Operation

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

nected to any internal circuitry; they should be tied to

ground.

VIN (Pin 4): Filter Input Pin. The Filter Input pin is internally

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

threshold 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 0.42µs (VS = ±5V).

Sine 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 1µs. The clock signal should be

routed from the right side of the IC package to avoid cou-

pling 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

VOUT (Pin 8): Filter Output Pin. Pin 8 is the output of

the 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.