DAC8551-Q1 Datasheet, PDF (13/28 Pages) Texas Instruments – Automotive 16-Bit, Ultralow-Glitch, Voltage-Output DAC

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DAC8551-Q1
SLASEB8A – FEBRUARY 2016 – REVISED MARCH 2016
Feature Description (continued)
7.3.1.1 Resistor String
The resistor string section is shown in Figure 28. It is simply a string of resistors, each of value R. The code
loaded into the DAC register determines at which node on the string the voltage is tapped off to be fed into the
output amplifier by closing one of the switches connecting the string to the amplifier. Monotonicity is ensured
because of the string resistor architecture.
7.3.1.2 Output Amplifier
The output buffer amplifier is capable of generating rail-to-rail voltages on its output, giving an output range of
0 V to V_DD. It is capable of driving a load of 2 kΩ in parallel with 1000 pF to GND. The source and sink
capabilities of the output amplifier can be seen in the Typical Characteristics. The slew rate is 1.4 V/μs with a full-
scale setting time of 8 μs with the output unloaded.
The inverting input of the output amplifier is brought out to the V_FB pin. This configuration allows for better
accuracy in critical applications by tying the V_FB point and the amplifier output together directly at the load. Other
signal conditioning circuitry may also be connected between these points for specific applications.
V_REF
R_DIVIDER
V_REF
2
R
R
To Output Amplifier
(2x Gain)
R
R
Figure 28. Resistor String
7.3.2 Power-On Reset
The DAC8551-Q1 contains a power-on-reset circuit that controls the output voltage during power up. On power
up, the DAC registers are filled with zeros and the output voltages are 0 V; they remain that way until a valid
write sequence is made to the DAC. The power-on reset is useful in applications where it is important to know
the state of the output of the DAC while it is in the process of powering up.
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