LTC2172CUKG-14#PBF Linear Technology, LTC2172CUKG-14#PBF Datasheet - Page 22

• Manufacturer Part Number: LTC2172CUKG-14#PBF
• Description: IC ADC 14BIT SER/PAR 65M 52-QFN
• Manufacturer: Linear Technology

Specifications of LTC2172CUKG-14#PBF

• Number Of Bits: 14
• Sampling Rate (per Second): 65M
• Data Interface: Serial, Parallel
• Number Of Converters: 4
• Power Dissipation (max): 419mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 52-WFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC2172-14/
LTC2171-14/LTC2170-14
APPLICATIONS INFORMATION
Reference
The LTC2172-14/LTC2171-14/LTC2170-14 has an internal
1.25V voltage reference. For a 2V input range using the
internal reference, connect SENSE to V
range using the internal reference, connect SENSE to
ground. For a 2V input range with an external reference,
apply a 1.25V reference voltage to SENSE (Figure 9).
The input range can be adjusted by applying a voltage to
SENSE that is between 0.625V and 1.30V. The input range
will then be 1.6 • V
The reference is shared by all four ADC channels, so it is
not possible to independently adjust the input range of
individual channels.
The V
shown in Figure 8. The 0.1μF capacitor between REFH and
REFL should be as close to the pins as possible (not on
the backside of the circuit board).
TIE TO GND FOR 1V RANGE;
22
TIE TO V
RANGE = 1.6 • V
0.625V < V
DD
REF
2.2μF
FOR 2V RANGE;
SENSE
0.1μF
0.1μF
, REFH and REFL pins should be bypassed, as
1.25V
SENSE
< 1.300V
FOR
Figure 8. Reference Circuit
SENSE
0.1μF
1μF
SENSE
REFH
V
REFL
REF
.
LTC2172-14
CONTROL
5Ω
DETECT
RANGE
AND
1.25V BANDGAP
DIFF AMP
REFERENCE
INTERNAL ADC
HIGH REFERENCE
0.8x
INTERNAL ADC
LOW REFERENCE
DD
. For a 1V input
0.625V
BUFFER
217214 F08
Encode Input
The signal quality of the encode inputs strongly affects
the A/D noise performance. The encode inputs should
be treated as analog signals—do not route them next to
digital traces on the circuit board. There are two modes
of operation for the encode inputs: the differential encode
mode (Figure 10), and the single-ended encode mode
(Figure 11).
ENC
ENC
1.8V TO 3.3V
Figure 9. Using an External 1.25V Reference
+
–
Figure 10. Equivalent Encode Input Circuit
for Differential Encode Mode
Figure 11. Equivalent Encode Input Circuit
for Single-Ended Encode Mode
REFERENCE
EXTERNAL
LTC2172-14
0V
1.25V
15k
30k
V
DD
ENC
ENC
V
DD
+
–
SENSE
1μF
1μF
V
LTC2172-14
REF
30k
LTC2172-14
CMOS LOGIC
BUFFER
DIFFERENTIAL
COMPARATOR
217214 F09
217214 F11
217214 F10
21721014fa