Datasheet

LTC2053/LTC2053-SYNC
12
2053syncfc
applicaTions inForMaTion
Figure 2. Centered Justified for a Single Line of Text
If a square wave is used to drive the CLK pin, a 5µs RC
time constant should be placed in front of the CLK pin to
maintain low offset voltage performance (see Figure 2).
This avoids internal and external coupling of the high
frequency components of the external clock at the instant
the LTC2053-SYNC holds the sampled input.
–
+
–
+
V
D
V
+IN
V
OUT
EXTERNAL
CLOCK
V
–IN
3
2053 F02
8
5V
4
5
1
6
R2
1k
R1
7
2
LTC2053-SYNC
CLK
5V
4.7nF
0V
The LTC2053-SYNC is tested with a sample clock of 3kHz
(f
CLK
= 24kHz) to the same specifications as the LTC2053.
In addition, the LTC2053-SYNC is tested at one-half and
2x this frequency to verify proper operation. The curves
in the Typical Performance Characteristics section of this
data sheet apply to the LTC2053-SYNC when driving it
with a 24kHz clock at Pin 1 (f
CLK
= 24kHz, 3kHz sample
clock rate). Below are three curves that show the behavior
of the LTC2053-SYNC as the clock frequency is varied.
The offset is essentially unaffected over a 2:1 increase or
decrease of the typical LTC2053 sample clock speed. The
bias current is directly proportional to the clock speed.
The noise is roughly proportional to the square root of
the clock frequency. For optimum noise and bias current
performance, drive the LTC2053-SYNC with a nominal
24kHz external clock (3kHz sample clock).
Figure 3. LTC2053-SYNC Input
Offset vs Sample Frequency
SAMPLE FREQUENCY (Hz) (= F
CLK
/8)
0
INPUT OFFSET (µV)
20
15
10
5
0
–5
–10
–15
–20
2000
4000 6000 8000
2053 F03
10000
V
S
= ±5V
V
S
= 5V
V
S
= 3V
TYP LTC2053
SAMPLE FREQUENCY
SAMPLE FREQUENCY (Hz) (= F
CLK
/8)
0
INPUT BIAS CURRENT (nA)
14
12
10
8
6
4
2
0
2000
4000 6000 8000
2053 F04
10000
V
S
= 5V
V
REF
= 0
V
CM
= 1V
TYP LTC2053
SAMPLE FREQUENCY
SAMPLE FREQUENCY (F
CLK
/8)
0
INPUT REFERRED NOISE VOLTAGE (µV
PP
)
12
10
8
6
4
2
0
2000
4000 6000 8000
2053 F05
10000
TYP LTC2053
SAMPLE FREQUENCY
V
S
= 5V
T
A
= 25°C
NOISE IN 10Hz BANDWIDTH
Figure 4. LTC2053-SYNC Average Input
Bias Current vs Sample Frequency
Figure 5. LTC2053-SYNC Input Referred
Noise vs Sample Frequency