LTC2484CDD#PBF Linear Technology, LTC2484CDD#PBF Datasheet - Page 33

• Manufacturer Part Number: LTC2484CDD#PBF
• Description: IC ADC 24BIT 10-DFN
• Manufacturer: Linear Technology

Specifications of LTC2484CDD#PBF

• Number Of Bits: 24
• Sampling Rate (per Second): 6.8
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 480µW
• Voltage Supply Source: Single Supply
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 10-WFDFN Exposed Pad
• Number Of Elements: 1
• Resolution: 24Bit
• Architecture: Delta-Sigma
• Sample Rate: 0.0075KSPS
• Input Polarity: Bipolar
• Input Type: Voltage
• Rated Input Volt: ±2.75V
• Differential Input: Yes
• Power Supply Requirement: Single
• Single Supply Voltage (typ): 3.3/5V
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 5.5V
• Dual Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Integral Nonlinearity Error: 10ppm of Vref
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 10
• Package Type: DFN EP
• Input Signal Type: Differential
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
at the 3dB frequency. When the internal oscillator is used,
the shape of the LTC2484 input bandwidth is shown in
Figure 28. When an external oscillator of frequency f
is used, the shape of the LTC2484 input bandwidth can
be derived from Figure 28, 60Hz mode curve in which the
horizontal axis is scaled by f
The conversion noise (600nV
can be modeled by a white noise source connected to
a noise free converter. The noise spectral density is
47nV√Hz for an infinite bandwidth source and 64nV√Hz
for a single 0.5MHz pole source. From these numbers,
it is clear that particular attention must be given to
the design of external amplification circuits. Such
circuits face the simultaneous requirements of very
low bandwidth (just a few Hz) in order to reduce the
output referred noise and relatively high bandwidth (at
least 500kHz) necessary to drive the input switched-
capacitor network. A possible solution is a high gain, low
bandwidth amplifier stage followed by a high bandwidth
unity-gain buffer.
When external amplifi ers are driving the LTC2484, the
ADC input referred system noise calculation can be
simplifi ed by Figure 29. The noise of an amplifi er driving
Figure 28. Input Signal Bandwidth Using the Internal Oscillator
–1
–2
–4
–5
–6
–3
0
0
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
1
50Hz MODE
2
EOSC
RMS
3
/307200.
50Hz AND
60Hz MODE
typical for V
60Hz MODE
4
2484 F28
5
REF
= 5V)
EOSC
the LTC2484 input pin can be modeled as a band limited
white noise source. Its bandwidth can be approximated
by the bandwidth of a single pole lowpass fi lter with a
corner frequency f
is n
can fi nd on the y-axis the noise equivalent bandwidth freq
of the input driving amplifi er. This bandwidth includes
the band limiting effects of the ADC internal calibration
and fi ltering. The noise of the driving amplifi er referred
to the converter input and including all these effects can
be calculated as N = n
(referred to the LTC2484 input) can now be obtained by
summing as square root of sum of squares the three ADC
input referred noise sources: the LTC2484 internal noise,
the noise of the IN
IN
If the f
f
the x-axis is scaled by f
the ratio f
to decrease, but at the same time the LTC2484 noise fl oor
rises and the noise contribution of the driving amplifi ers
lose signifi cance.
EOSC
–
i
driving amplifi er.
. From Figure 29, using f
Figure 29. Input Referred Noise Equivalent Bandwidth
of an Input Connected White Noise Source
, Figure 29 can still be used for noise calculation if
O
pin is driven by an external oscillator of frequency
EOSC
100
0.1
10
1
/307200, the Figure 29 plot accuracy begins
0.1
+
INPUT NOISE SOURCE SINGLE POLE
i
. The amplifi er noise spectral density
1
driving amplifi er and the noise of the
EQUIVALENT BANDWIDTH (Hz)
10
i
EOSC
• √freq
100
60Hz MODE
50Hz MODE
/307200. For large values of
i
as the x-axis selector, we
i
1k
. The total system noise
10k 100k
LTC2484
2484 F29
1M
33
2484fc
i