Datasheet
V
S
DATA
CLK
V
S
F
0
LD
FL
0
_RF
GND LE
F
IN
_IF V
S
CE
F
IN
B_RF
D
0
_IF
OSC_EN
OSC_OUT/FL
0
_IF
OSC_IN
F
IN
_RF
GND
D
0
_RF
GND
17
16
15
14
13
12
11
1
2
3
4
5
6
7
C
26
0.01 PF
C
27
100 pF
IF_PLL I/O's
RF_PLL PROGRAMMING INPUTS
8
9
10
20
19
18
C
13
0.01 PF
C
14
100 pF
C
10
0.01 PF
C
11
100 pF
C
5
100 pF
C
1
C
2
C
4
R
2
-
+
C
6
100 pF
V
S
_PLL
R
46
100 k:
R
45
100 k:
C
37
0.1 PF
C
39
R
47
C
38
R
50
10:
C
41
0.1 PF
V
S
_OP AMP
3
2
1
16
7
6
5
4
12
13
14
15
8
9
10
11
RF
OUT
V
CC
V
+
C8
0.01 PF
V
S
_RF
L2
C9
100 pF
V586ME04
R
5
18:
R
7
18:
C
7
100 pF
RF_OUT
R
6
18:
C
40
100 pF
V
S
_PLL
R
3
R
41
C
36
C
3
V
S
_PLL
V
S
_PLL
LM6211
LMX2430
LM6211
SNOSAH2C –FEBRUARY 2006–REVISED MARCH 2013
www.ti.com
Figure 41. LM6211 in the Active Loop Filter for LMX2430
ADC INPUT DRIVER
A typical application for a high performance op amp is as an ADC driver, which delivers the analog signal
obtained from sensors and actuators to ADCs for conversion to the digital domain and further processing.
Important requirements in this application are a slew rate high enough to drive the ADC input and low input
referred voltage and current noise. If an op amp is used with an ADC, it is critical that the op amp noise does not
affect the dynamic range of the ADC. The LM6211, with low input referred voltage and current noise, provides a
great solution for this application. For example, the LM6211 can be used to drive an ADS121021, a 12-bit ADC
from TI. If it provides a gain of 10 to a maximum input signal amplitude of 100 mV, for a bandwidth as wide as
100 kHz, the average noise seen at the input of the ADC is only 44.6 µVrms. Hence the dynamic range of the
ADC, measured in Effective Number of Bits or ENOB, is only reduced by 0.3 bits, despite amplifying the input
signal by a gain of 10. Low input bias currents and high input impedance also help as they prevent the loading of
the sensor and allow the measurement system to function over a large range.
Figure 42 shows a circuit for monitoring fluid pressure in a hydraulic system, in which the LM6211 is used to
sense the error voltage from the pressure sensor. Two LM6211 amplifiers are used to make a difference
amplifier which senses the error signal, amplifies it by a gain of 100, and delivers it to the ADC input. The ADC
converts the error voltage into a pressure reading to be displayed and drives the DAC, which changes the
voltage driving the resistance bridge sensor. This is used to control the gain of the pressure measurement circuit,
such that the range of the sensor can be modified to obtain the best resolution possible.
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