Datasheet

Resistor
StringDAC
Amplifier
Power-down
Circuitry
Resistor
Network
V
OUT
DAC5311
DAC6311
DAC7311
www.ti.com SBAS442B –AUGUST 2008–REVISED MAY 2013
POWER-ON RESET TO ZERO-SCALE is also internally switched from the output of the
amplifier to a resistor network of known values. The
The DACx311 contains a power-on reset circuit that
advantage of this architecture is that the output
controls the output voltage during power-up. On
impedance of the part is known while the part is in
power-up, the DAC register is filled with zeros and
power-down mode. There are three different options.
the output voltage is 0V. The DAC register remains
The output is connected internally to GND either
that way until a valid write sequence is made to the
through a 1kΩ resistor or a 100kΩ resistor, or is left
DAC. This design is useful in applications where it is
open-circuited (High-Z). Figure 80 illustrates the
important to know the state of the output of the DAC
output stage.
while it is in the process of powering up.
The occurring power-on glitch impulse is only a few
millivolts (typically, 17mV; see Figure 33).
POWER-DOWN MODES
The DACx311 contains four separate modes of
operation. These modes are programmable by setting
two bits (PD1 and PD0) in the control register.
Table 5 shows how the state of the bits corresponds
to the mode of operation of the device.
Table 5. Modes of Operation for the DACx311
Figure 80. Output Stage During Power-Down
PD1 PD0 OPERATING MODE
Normal Mode
All linear circuitry is shut down when the power-down
0 0 Normal Operation
mode is activated. However, the contents of the DAC
register are unaffected when in power-down. The
Power-Down Modes
time to exit power-down is typically 50μs for AV
DD
=
0 1 Output 1kΩ to GND
5V and AV
DD
= 3V.
1 0 Output 100kΩ to GND
1 1 High-Z
DAC NOISE PERFORMANCE
When both bits are set to '0', the device works
Typical noise performance for the DACx311 is shown
normally with a standard power consumption of
in Figure 34 and 35. Output noise spectral density at
typically 80μA at 2.0V. However, for the three power-
the V
OUT
pin versus frequency is depicted in Figure
down modes, the typical supply current falls to 0.5μA
34 for full-scale, midscale, and zero-scale input
at 5V, 0.4μA at 3V, and 0.1μA at 2.0V. Not only does
codes. The typical noise density for midscale code is
the supply current fall, but the output stage
110nV/√Hz at 1kHz and at 1MHz.
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