LTC1061_09 Datasheet, PDF (6/16 Pages) Linear Technology – High Performance Triple Universal Filter Building Block

LTC1061
U
UU
PI DESCRIPTIO A D APPLICATIO HI TS
+
1µF
R1
R3
R2
2.49k
2.49k
1
20
2
19
3
18
4
17
5
16
LTC1061
6
15
7
14
8
13
9
12
V_OUT
R3
R2
R1
R4
R3
R2
Clock Feedthrough
This is defined as the amplitude of the clock frequency
appearing at the output pins of the device, Figure 2. Clock
feedthrough is measured with all three sides of the LTC1061
connected as filters. The clock feedthrough mainly de-
pends on the magnitude of the power supplies and it is
independent from the input clock levels, clock frequency
and modes of operation.
The Table 2 illustrates the typical clock feedthrough num-
bers for various power supplies.
5V
T²L CLOCK
IN
f_CLK < 1MHz
10
0.1µF
11
R1
C_IN
1061 F01
V_IN
Figure 1. The 6th Order LP Butterworth Filter of Figure 5
Operating with a Single 5V Supply
A = 2V/DIV
50/100/Hold (Pin 7)
By tying Pin 7 to V⁺, the filter operates with a clock-to-
center frequency internally set at 50:1. When Pin 7 is at
mid-supplies, the filter operates with a 100:1 clock-to-
center frequency ratio. Table 1 shows the allowable varia-
tion of the potential at Pin 7 when the 100:1 mode is
sought.
When Pin 7 is shorted to the negative supply pin, the filter
operation is stopped and the bandpass and lowpass
output act as a sample-and-hold circuit holding the last
sample of the input voltage. The hold step is around 2mV
and the droop rate is 150µV/sec.
Table 1
TOTAL POWER SUPPLY
(V)
5
10
15
VOLTAGE RANGE OF PIN 7
FOR 100:1 OPERATION (V)
2.5 ± 0.5
5 ±1
7.5 ±1.5
B = 10mV/DIV
HORIZONTAL = 10µs/DIV
1061 F02
Figure 2. Typical Clock Feedthrogh of the LTC1061 Operating
with ±5V Supplies. Top Trace is the Input Clock Swinging 0V to
5V and Bottom Trace is One of the Lowpass Outputs with Zero or
DC Input Signals.
POWER SUPPLY (V)
±2.5
±5
±8
Table 2
CLOCK FEEDTHROUGH (V_RMS)
0.2
0.4
0.8
Definition of Filter Functions
Refer to LTC1060 data sheet.
1061fe
6