DAC124S085EB/NOPB National Semiconductor, DAC124S085EB/NOPB Datasheet - Page 16

• Manufacturer Part Number: DAC124S085EB/NOPB
• Description: BOARD EVALUATION DAC124S085
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of DAC124S085EB/NOPB

• Number Of Dac's: 4
• Number Of Bits: 12
• Outputs And Type: 4, Single Ended
• Data Interface: Serial
• Settling Time: 6µs
• Dac Type: Voltage
• Voltage Supply Source: Single
• Operating Temperature: -40°C ~ 105°C
• Utilized Ic / Part: DAC124S085
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: DAC124S085EB

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2.1.2 LM4050
Available with accuracy of 0.44%, the LM4050 shunt refer-
ence is also a good choice as a reference for the
DAC124S085. It is available in 4.096V and 5V versions and
comes in a space-saving 3-pin SOT23.
The minimum resistor value in the circuit of Figure 6 must be
chosen such that the maximum current through the LM4050
does not exceed its 15 mA rating. The conditions for maxi-
mum current include the input voltage at its maximum, the
FIGURE 6. The LM4050 as a power supply
FIGURE 5. The LM4130 as a power supply
FIGURE 7. Using the LP3985 regulator
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LM4050 voltage at its minimum, and the DAC124S085 draw-
ing zero current. The maximum resistor value must allow the
LM4050 to draw more than its minimum current for regulation
plus the maximum DAC124S085 current in full operation. The
conditions for minimum current include the input voltage at its
minimum, the LM4050 voltage at its maximum, the resistor
value at its maximum due to tolerance, and the DAC124S085
draws its maximum current. These conditions can be sum-
marized as
and
where V
voltages ± the LM4050 output tolerance over temperature, I
(max) is the maximum allowable current through the LM4050,
I
proper
DAC124S085 supply current.
2.1.3 LP3985
The LP3985 is a low noise, ultra low dropout voltage regulator
with a 3% accuracy over temperature. It is a good choice for
applications that do not require a precision reference for the
DAC124S085. It comes in 3.0V, 3.3V and 5V versions, among
others, and sports a low 30 µV noise specification at low fre-
quencies. Since low frequency noise is relatively difficult to
filter, this specification could be important for some applica-
tions. The LP3985 comes in a space-saving 5-pin SOT23 and
5-bump micro SMD packages.
Z
(min) is the minimum current required by the LM4050 for
R(max) = ( V
Z
regulation,
(min) and V
R(min) = ( V
IN
(min) − V
Z
and
(max) are the nominal LM4050 output
IN
(max) − V
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Z
(max) ) / ( (I
I
DAC
(max)
Z
(min) ) /I
DAC
is
(max) + I
Z
(max)
the
maximum
Z
(min) )
Z