Datasheet

LM4132-4.1
DAC104S085
DIN
SCLK
SYNC
V
OUT
= 0V to 4.092V
C1
0.1 PF
C2
2.2 PF
Input
Voltage
V
A
V
REFIN
C3
0.1 PF
DAC104S085
SNAS362F –MAY 2006–REVISED MARCH 2013 www.ti.com
POWER-DOWN MODES
The DAC104S085 has four power-down modes, two of which are identical. In power-down mode, the supply
current drops to 20 µA at 3V and 30 µA at 5V. The DAC104S085 is set in power-down mode by setting OP1 and
OP0 to 11. Since this mode powers down all four DACs, the address bits, A1 and A0, are used to select different
output terminations for the DAC outputs. Setting A1 and A0 to 00 or 11 causes the outputs to be tri-stated (a high
impedance state). While setting A1 and A0 to 01 or 10 causes the outputs to be terminated by 2.5 kΩ or 100 kΩ
to ground respectively (see Table 1).
Table 1. Power-Down Modes
A1 A0 OP1 OP0 Operating Mode
0 0 1 1 High-Z outputs
0 1 1 1 2.5 kΩ to GND
1 0 1 1 100 kΩ to GND
1 1 1 1 High-Z outputs
The bias generator, output amplifiers, resistor strings, and other linear circuitry are all shut down in any of the
power-down modes. However, the contents of the DAC registers are unaffected when in power-down. Each DAC
register maintains its value prior to the DAC104S085 being powered down unless it is changed during the write
sequence which instructed it to recover from power down. Minimum power consumption is achieved in the
power-down mode with SYNC and D
IN
idled low and SCLK disabled. The time to exit power-down (Wake-Up
Time) is typically t
WU
µsec as stated in the A.C. and Timing Characteristics table.
Applications Information
USING REFERENCES AS POWER SUPPLIES
While the simplicity of the DAC104S085 implies ease of use, it is important to recognize that the path from the
reference input (V
REFIN
) to the VOUTs will have essentially zero Power Supply Rejection Ratio (PSRR).
Therefore, it is necessary to provide a noise-free supply voltage to V
REFIN
. In order to utilize the full dynamic
range of the DAC104S085, the supply pin (V
A
) and V
REFIN
can be connected together and share the same supply
voltage. Since the DAC104S085 consumes very little power, a reference source may be used as the reference
input and/or the supply voltage. The advantages of using a reference source over a voltage regulator are
accuracy and stability. Some low noise regulators can also be used. Listed below are a few reference and power
supply options for the DAC104S085.
LM4130
The LM4130, with its 0.05% accuracy over temperature, is a good choice as a reference source for the
DAC104S085. The 4.096V version is useful if a 0 to 4.095V output range is desirable or acceptable. Bypassing
the LM4130 VIN pin with a 0.1µF capacitor and the VOUT pin with a 2.2µF capacitor will improve stability and
reduce output noise. The LM4130 comes in a space-saving 5-pin SOT23.
Figure 31. The LM4130 as a power supply
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