DAC8801_16 Datasheet, PDF (10/22 Pages) Texas Instruments – 14-Bit, Serial Input Multiplying Digital-to-Analog Converter

DAC8801
SLAS403B – NOVEMBER 2004 – REVISED FEBRUARY 2007
APPLICATION INFORMATION
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Stability Circuit
For a current-to-voltage design as shown in Figure 20, the DAC8801 current output (I_OUT) and the connection
with the inverting node of the op amp should be as short as possible and according to correct PCB layout
design. For each code change there is a step function. If the GBP of the op amp is limited and parasitic
capacitance is excessive at the inverting node then gain peaking is possible. Therefore, for circuit stability, a
compensation capacitor C1 (4 pF to 20 pF typ) can be added to the design as shown in Figure 20.
V_DD
V_REF
V_DD
R_FB
V_REF U1
I_OUT
GND
C1
_
U2
+
V_OUT
Figure 20. Gain Peaking Prevention Circuit With Compensation Capacitor
Positive Voltage Output Circuit
As shown in Figure 21, in order to generate a positive voltage output, a negative reference is input to the
DAC8801. This design is suggested instead of using an inverting amp to invert the output due to tolerance
errors of the resistor. For a negative reference, V_OUT and GND of the reference are level-shifted to a virtual
ground and a -2.5 V input to the DAC8801 with an op amp.
+2.5V Reference ^VDD
V_OUT
V_IN
GND _VDD R_FB
−
V_REF
+
−2.5 V
OPA277
DAC8801
GND
C1
I_OUT
OPA277
−
+
V_OUT
0 3 V_OUT 3 +2.5 V
Figure 21. Positive Voltage Output Circuit
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