Datasheet

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Z
O
+
R1ȀR3
(
R1)R2
)
R1
(
R2Ȁ)R3Ȁ
)
* R1Ȁ
(
R2)R3
)
(4)
V
DD
V
DD
V
REF
V
REF
DAC8811
U1
R
FB
OPA277
U2
I
OUT
GND
150 kW
R14
15 kW
R24
C1 10 pF
OPA277
U2
15 kW
R2
50 kW
R34
50 W
R3
V
OUT
150 kW
R1
I
L
LOAD
−
+
+
−
Cross-Reference
DAC8811
SLAS411B – NOVEMBER 2004 – REVISED FEBRUARY 2007
APPLICATION INFORMATION (continued)
The value of R3 in the previous equation can be reduced to increase the output current drive of U3. U3 can
drive ± 20 mA in both directions with voltage compliance limited up to 15 V by the U3 voltage supply. Elimination
of the circuit compensation capacitor C1 in the circuit is not suggested as a result of the change in the output
impedance Z
O
, according to Equation 4 :
As shown in Equation 4 , with matched resistors, Z
O
is infinite and the circuit is optimum for use as a current
source. However, if unmatched resistors are used, Z
O
is positive or negative with negative output impedance
being a potential cause of oscillation. Therefore, by incorporating C1 into the circuit, possible oscillation
problems are eliminated. The value of C1 can be determined for critical applications; for most applications,
however, a value of several pF is suggested.
Figure 23. Programmable Bidirectional Current Source Circuit
The DAC8811 has an industry-standard pinout. Table 3 provides the cross-reference information.
Table 3. Cross-Reference
SPECIFIED
TEMPERATURE PACKAGE PACKAGE CROSS-
PRODUCT INL (LSB) DNL (LSB) RANGE DESCRIPTION OPTION REFERENCE PART
DAC8811ICDGK ± 1 ± 1 -40°C to +85°C 8-Lead MicroSOIC MSOP-8 N/A
DAC8811IBDGK ± 2 ± 1 -40 ° C to +85 ° C 8-Lead MicroSOIC MSOP-8 AD5543BRM
DAC8811ICDRB ± 1 ± 1 -40 ° C to +85 ° C 8-Lead Small Outline SON-8 N/A
DAC8811IBDRB ± 2 ± 1 -40 ° C to +85 ° C 8-Lead Small Outline SON-8 N/A
N/A ± 2 ± 1 -40 ° C to +85 ° C 8-Lead SOIC SOIC-8 AD5543BR
11
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