AD5233BRU50 Analog Devices Inc, AD5233BRU50 Datasheet - Page 25

• Manufacturer Part Number: AD5233BRU50
• Description: IC POT QUAD 50K 64POS 24-TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD5233BRU50

• Rohs Status: RoHS non-compliant
• Taps: 64
• Resistance (ohms): 50K
• Number Of Circuits: 4
• Temperature Coefficient: 600 ppm/°C Typical
• Memory Type: Non-Volatile
• Interface: 4-Wire SPI Serial
• Voltage - Supply: 2.7 V ~ 5.5 V, ±2.25 V ~ 2.75 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-TSSOP
• Resistance In Ohms: 50K

PROGRAMMABLE STATE-VARIABLE FILTER
One of the standard circuits used to generate a low-pass, high-
pass, or band-pass filter is the state-variable active filter. The
AD5233 digital potentiometer allows full programmability
of the frequency, the gain, and the Q of the filter outputs.
Figure 52 shows a filter circuit using a 2.5 V virtual ground,
which allows a ±2.5 V peak input and output swing. RDAC2
and RDAC3 set the low-pass, high-pass, and band-pass cutoff
and center frequencies, respectively. RDAC2 and RDAC3
should be programmed with the same data (as with ganged
potentiometers) to maintain the best Circuit Q.
V
The transfer function of the band-pass filter is
where A
For R
IN
B
Q
ω
V
A =
WB2(D2)
RDAC1
V
O
O
BP
=
i
O
=
is the gain.
R
R
=
R
R
R
WA4
WB4
2.5V
= R
A1
Figure 52. Programmable Stable-Variable Filter
S
WB2
WA1
WB1
2
1
RDAC4
B
+
WB3(D3)
×
C1
A
ω
R
O
Q
R1
WB1
O
ω
Q
S
, R1 = R2, and C1 = C2:
O
A2
10kΩ
+
R1
S
OP279 × 2
ω
O
RDAC2
2
10kΩ
R2
B
A3
0.01µF
RDAC3
B
0.01µF
A3
LOW-PASS
BAND-PASS
HIGH-PASS
(10)
(11)
(12)
Rev. B | Page 25 of 32
(9)
Figure 53 shows the measured filter response at the band-pass
output as a function of the RDAC2 and RDAC3 settings, which
produce a range of center frequencies from 2 kHz to 20 kHz.
The filter gain response at the band-pass output is shown in
Figure 54. At a center frequency of 2 kHz, the gain is adjusted
over the −20 dB to +20 dB range, determined by RDAC1.
Circuit Q is adjusted by RDAC4 and RDAC1. Suitable op amps
for this application are OP4177, AD8604, OP279, and AD824.
Figure 53. Programmed Center Frequency Band-Pass Response
–20
–40
–60
–80
–20
–40
–60
–80
40
20
40
20
0
0
Figure 54. Programmed Amplitude Band-Pass Response
20
20
100
100
–19.01
–16
FREQUENCY (Hz)
FREQUENCY (Hz)
1k
1k
20k
2.0k
10k
10k
*
100k 200k
100k 200k
AD5233