AD5233BRUZ50-R7 Analog Devices Inc, AD5233BRUZ50-R7 Datasheet - Page 27

• Manufacturer Part Number: AD5233BRUZ50-R7
• Description: IC DGTL POT QUAD 64POS 24-TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD5233BRUZ50-R7

• 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
• Number Of Elements: 4
• # Of Taps: 64
• Resistance (max): 50KOhm
• Power Supply Requirement: Single/Dual
• Interface Type: Serial (4-Wire/SPI)
• Single Supply Voltage (typ): 3/5V
• Dual Supply Voltage (typ): ±2.5V
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 5.5V
• Dual Supply Voltage (min): ±2.25V
• Dual Supply Voltage (max): ±2.75V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 24
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PROGRAMMABLE CURRENT SOURCE
A programmable current source can be implemented with the
circuit shown in Figure 58.
REF191 is a unique low supply headroom precision reference
that can deliver the 20 mA needed at 2.048 V. The load current
is simply the voltage across Terminal B to Terminal W of the
digital potentiometer divided by R
The circuit is simple, but be aware that there are two issues.
First, dual-supply op amps are ideal, because the ground
potential of REF191 can swing from −2.048 V at zero scale
to V
circuit works under single supply, the programmable resolution
of the system is reduced. Second, the voltage compliance at V
is limited to 2.5 V or equivalently a 125 Ω load. If higher voltage
compliance is needed, users can consider digital potentiometers
AD5260, AD5280, and AD7376. Figure 58 shows an alternative
circuit for high voltage compliance.
To achieve higher current, such as when driving a high power
LED, the user can replace the U1 with an LDO, reduce R
add a resistor in series with the AD5233’s A terminal. This
limits the potentiometer’s current and enhances the current
adjustment resolution.
L
at full scale of the potentiometer setting. Although the
3
–2.048V TO V
SLEEP
GND
+5V
2
4
V
S
REF191
Figure 58. Programmable Current Source
U1
AD5233
OUTPUT
L
6
0 TO (2.048 + V
C1
1µF
V+
V–
OP1177
+5V
–5V
U2
S
.
B
A
–
+
L
W
)
100Ω
R
L
R
102Ω
S
V
L
I
L
S
, and
Rev. B | Page 27 of 32
L
PROGRAMMABLE BIDIRECTIONAL CURRENT
SOURCE
For applications that require bidirectional current control or
higher voltage compliance, a Howland current pump can be
used (see Figure 59).
If the resistors are matched, the load current is
R2B, in theory, can be made as small as necessary to achieve the
current needed within the A2 output current-driving capability.
In this circuit, OP2177 delivers ±5 mA in both directions, and
the voltage compliance approaches 15 V. Without C1, it can be
shown that the output impedance is
Z
with R1 and R2A + R2B, respectively. On the other hand, Z
be negative if the resistors are not matched. As a result, C1 in
the range of 1 pF to 10 pF is needed to prevent oscillation from
the negative impedance.
RESISTANCE SCALING
AD5233 offers 10 kΩ, 50 kΩ, and 100 kΩ nominal resistance.
Users who need lower resistance but want to maintain the
number of adjustment steps can parallel multiple devices. For
example, Figure 60 shows a simple scheme of paralleling two
AD5233 channels. To adjust half the resistance linearly per step,
users need to program both devices concurrently with the same
settings.
Figure 60. Reduce Resistance by Half with Linear Adjustment Characteristics
O
AD5233
can be infinite if the R1´ and R2´ resistors match precisely
I
Z
L
O
=
=
Figure 59. Programmable Bidirectional Current Source
+2.5V
–2.5V
A
B W
(
R1
R2A
R1
×
R2B
'
R1
R2
+
×
A1
R2B
'
+
–
R2B
−
OP2177
+15V
–15V
V+
V–
R1
LD
A1
B1
)
( '
(
×
R1
R2A
V
W1
W
+
V
R2A
DD
+
150kΩ
150kΩ
R2B
R1
R1
A2
B2
)
)
W2
–
+
OP2177
+15V
–15V
V+
V–
15kΩ
14.95kΩ
R2
R2A
A2
10pF
C1
AD5233
R2B
50Ω
500Ω
R
L
V
L
I
L
O
(17)
(18)
can