LTC1407CMSE Linear Technology, LTC1407CMSE Datasheet - Page 13

• Manufacturer Part Number: LTC1407CMSE
• Description: IC ADC 12BIT 3MSPS SAMPLE 10MSOP
• Manufacturer: Linear Technology

Specifications of LTC1407CMSE

• Number Of Bits: 12
• Sampling Rate (per Second): 3M
• Data Interface: Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 14mW
• Voltage Supply Source: Single Supply
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS INFORMATION
INPUT RANGE
The analog inputs of the LTC1407/LTC1407A may be driven
fully differentially with a single supply. Either input may
swing up to 3V, provided the differential swing is no greater
than 2.5V. In the valid input range, the noninverting input
of each channel should always be more positive than the
inverting input of each channel. The 0V to 2.5V range is
also ideally suited for single-ended input use with single
supply applications. The common mode range of the
inputs extend from ground to the supply voltage V
the difference between the CH0
CH1
stay fi xed at all ones, and if this difference goes below 0V,
the ouput code will stay fi xed at all zeros.
INTERNAL REFERENCE
The LTC1407/LTC1407A have an on-chip, temperature
compensated, bandgap reference that is factory trimmed
near 2.5V to obtain a precise 2.5V input span. The refer-
ence amplifi er output V
a capacitor to ground. The reference amplifi er is stable
with capacitors of 1μF or greater. For the best noise per-
formance, a 10μF ceramic or a 10μF tantalum in parallel
with a 0.1μF ceramic is recommended. The V
+
and CH1
–
3V REF
inputs exceeds 2.5V, the output code will
REF
Figure 2
, (Pin 3) must be bypassed with
10μF
+
and CH0
11
3
V
GND
REF
LTC1407A
LTC1407/
–
REF
inputs or the
1407 F02
pin can be
DD
. If
overdriven with an external reference as shown in Figure 2.
The voltage of the external reference must be higher than
the 2.5V of the open-drain P-channel output of the internal
reference. The recommended range for an external refer-
ence is 2.55V to V
see a DC quiescent load of 0.75mA and as much as 3mA
during conversion.
INPUT SPAN VERSUS REFERENCE VOLTAGE
The differential input range has a unipolar voltage span that
equals the difference between the voltage at the reference
buffer output V
Pad ground. The differential input range of ADC is 0V to
2.5V when using the internal reference. The internal ADC
is referenced to these two nodes. This relationship also
holds true with an external reference.
DIFFERENTIAL INPUTS
The ADC will always convert the unipolar difference of
CH0
nus CH1
either set of inputs. The common mode rejection holds up
at high frequencies (see Figure 3.) The only requirement
is that both inputs not go below ground or exceed V
+
minus CH0
–
–100
–120
, independent of the common mode voltage at
–20
–40
–60
–80
0
100
REF
Figure 3. CMRR vs Frequency
LTC1407/LTC1407A
–
1k
DD
or the unipolar difference of CH1
(Pin 3) and the voltage at the Exposed
. An external reference at 2.55V will
10k
FREQUENCY (Hz)
CH0
100k
1M
CH1
10M
1407 G08
100M
13
+
1407fb
mi-
DD
.