ADC10154BIWM National Semiconductor, ADC10154BIWM Datasheet - Page 18

• Manufacturer Part Number: ADC10154BIWM
• Description: IC ADC 10BIT W/4-8 CH MX SO20
• Manufacturer: National Semiconductor

Specifications of ADC10154BIWM

• Number Of Bits: 10
• Sampling Rate (per Second): 166k
• Number Of Converters: 1
• Power Dissipation (max): 33mW
• Voltage Supply Source: Analog and Digital, Dual ±
• Operating Temperature: -65°C ~ 150°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (0.300", 7.50mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *ADC10154BIWM

www.national.com
2.0 Applications Information
2.2 REFERENCE CONSIDERATIONS
The voltage difference between the V
defines the analog input voltage span (the difference be-
tween V
the programmed resolution) possible output codes apply. In
the pseudo-differential and differential modes the actual volt-
age applied to V
the AV
When using the single-ended multiplexer mode the voltage
at V
the “zero” reference voltage and, with V
voltage span.
The value of the voltage on the V
anywhere between AV
V
can be used in either ratiometric applications or in systems
requiring absolute accuracy. The reference pins must be
connected to a voltage source capable of driving the mini-
mum reference input resistance of 4.5 k .
The internal 2.5V bandgap reference in the ADC10154 and
ADC10158 is available as an output on the VREFOut pin. To
ensure optimum performance this output needs to be by-
passed to ground with 330 µF aluminum electrolytic or tan-
talum capacitor. The reference output is unstable with ca-
pacitive loads greater than 100 pF and less than 100 µF. Any
capacitive loads
reference to oscillate. Lower output noise can be obtained by
increasing the output capacitance. The 330 µF capacitor will
yield a typical noise floor of 200 nVrms/
REF
REF
+
+
is greater than V
−
and V
IN
has a dual function. It simultaneously determines
(Max) and V
−
. Only the difference voltage is of importance.
REF
3 Pseudo-Differential
100 pF or
+
4 Single-Ended
and V
+
IN
REF
+ 50 mV and V
(Min)) over which the 2
−
. The ADC10154 and ADC10158
REF
−
100 µF will not cause the
REF
can lie anywhere between
DS011225-42
DS011225-40
+
REF
or V
−
FIGURE 4. Analog Input Multiplexer Options
− 50 mV, so long as
+
REF
and V
REF
.
−
+
inputs can be
n
, the analog
REF
(where n is
(Continued)
− inputs
18
The 2.5V reference output is referred to the negative supply
pin (V
2.5V greater than the voltage applied to V
voltage to V
voltage span of 2.5V. In bipolar operation the voltage at
VREFOut will be at −2.5V when V
single-ended multiplexer mode the analog input voltage
range will be from −5V to −2.5V. The pseudo-differential and
differential multiplexer modes allow for more flexibility in the
analog input voltage range since the “zero” reference volt-
age is set by the actual voltage applied to the assigned
negative input pin. The drawback of using the internal refer-
ence in the bipolar mode is that any noise on the −5V tied to
the V
reference is specified and tested in unipolar operation with
V
In a ratiometric system ( Figure 5 (a)), the analog input volt-
age is proportional to the voltage used for the A/D reference.
This voltage may also be the system power supply, so V
can also be tied to AV
requirements of the system reference as the analog input
and A/D reference move together maintaining the same
output code for a given input condition.
For absolute accuracy ( Figure 5 (b)), where the analog input
varies between very specific voltage limits, the reference pin
can be biased with a time- and temperature-stable voltage
source that has excellent initial accuracy. The LM4040 and
LM185 references are suitable for use with the ADC10154
and ADC10158.
−
tied to the system ground.
−
−
2 Single Ended and 1 Differential
). Therefore, the voltage at VREFOut will always be
pin will affect the conversion result. The bandgap
REF
+
with V
2 Differential
+
. This technique relaxes the stablity
REF
−
tied to V
DS011225-41
DS011225-43
−
is tied to −5V. For the
−
will yield an analog
−
. Applying this
REF
+