LTC1069-6

7

10696fa

APPLICATIONS INFORMATION

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

passband behavior which is temperature independent.

Clock Feedthrough

The clock feedthrough is defined as the RMS value of the

clock frequency and its harmonics that are present at the

filter’s Output (Pin 8). The clock feedthrough is tested with

the Input (Pin 4) shorted to AGND (Pin 1) and depends on

PC board layout and on the value of the power supplies.

With proper layout techniques the values of the clock

feedthrough are shown in Table 2.

Table 2. Clock Feedthrough

CLOCK FEEDTHROUGH

3.3V

5V

10V

Any parasitic switching transients during the rising and

falling edges of the incoming clock are not part of the

clock feedthrough specifications. Switching transients

have frequency contents much higher than the applied

clock; their amplitude strongly depends on scope probing

techniques as well as grounding and power supply

bypassing. The clock feedthrough can be reduced by adding

a single RC lowpass filter at the Output (Pin 8).

FREQUENCY (kHz)

1

1

2

17

1069-6 F04a

0

–1

–2

5

9

13

319

7

11

15

21

85°C

–40°C

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

FREQUENCY (kHz)

1

1

2

25

1069-6 F04c

0

–1

–2

7

13

19

428

10

16

22

31

85°C

–40°C

Figure 4b

Figure 4c