Texas Instruments DRV632EVM - DRV632EVM Evaluation Module DRV632EVM DRV632EVM Datenbogen
Produktcode
DRV632EVM
R
2
R
1
R
3
C
2
C
X
C
1
C
3
DRV632
R
2
R
2
R
1
R
3
C
1
C
1
C
3
R
1
R
3
C
3
-In
+In
C
2
DRV632
Component Selection
www.ti.com
Figure 5. Second-Order, Active Low-Pass Filter
Table 3. DRV632EVM Filter Specifications
Single
Ended
Ended
Differential
Gain
High Pass
Low Pass
C1
C2
C2
C3
R1
R2
R3
–1 V/V
16 Hz
40 kHz
100 pF
680 pF
270 pF
1
m
F
10 k
Ω
10 k
Ω
24 k
Ω
–1.5 V/V
19 Hz
40 kHz
68 pF
680 pF
270 pF
1
m
F
8.2 k
Ω
12 k
Ω
30 k
Ω
–2 V/V
11 Hz
30 kHz
47 pF
470 pF
180 pF
1
m
F
15 k
Ω
30 k
Ω
43 k
Ω
–3.33 V/V
12 Hz
30 kHz
33 pF
470 pF
180 pF
1
m
F
13 k
Ω
43 k
Ω
43 k
Ω
–10 V/V
15 Hz
30 kHz
22 pF
1 nF
330 pF
2.2
m
F
4.7 k
Ω
47k
Ω
27 k
Ω
The resistor values must be low value to achieve low noise, but must be of high enough value to obtain a
small size ac-coupling capacitor. With the proposed values of 15 k
small size ac-coupling capacitor. With the proposed values of 15 k
Ω
, 30 k
Ω
, and 43 k
Ω
, a dynamic range
(DYR) of 102 dB can be achieved with a small 2.2-
m
F input ac-coupling capacitor.
The MFB filter structure demands an operational amplifier that is unity-gain stable at high frequencies; this
requirement can be relaxed by adding the C
requirement can be relaxed by adding the C
X
capacitor value to be equal to C1. The DRV632 is unity-gain
stable, but stray capacitance and inductance from the PCB layout can affect the phase margin. Therefore,
TI recommends adding C
TI recommends adding C
X
.
4.4
Using the DRV632 as a Differential Input, Second-Order Low-Pass Filter
The single-ended input, second-order filter described in
can easily be extended to have a
differential input, as shown in
.
Figure 6. Differential Input, Second-Order Active Low-Pass Filter
6
DRV632EVM Evaluation Module
SLOU301 – January 2010
© 2010, Texas Instruments Incorporated