LTC2220IUP-1#PBF Linear Technology, LTC2220IUP-1#PBF Datasheet - Page 21

• Manufacturer Part Number: LTC2220IUP-1#PBF
• Description: IC ADC 12BIT 185MSPS 64-QFN
• Manufacturer: Linear Technology

Specifications of LTC2220IUP-1#PBF

• Number Of Bits: 12
• Sampling Rate (per Second): 185M
• Data Interface: Parallel
• Number Of Converters: 1
• Power Dissipation (max): 1.18W
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-WFQFN, Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
The A
package inductance. The two A
should be shorted together.
For input frequencies above 100MHz the input circuits of
Figure 6, 7 and 8 are recommended. The balun trans-
former gives better high frequency response than a flux
coupled center tapped transformer. The coupling capaci-
tors allow the analog inputs to be DC biased at 1.6V. In
Figure 8 the series inductors are impedance matching
elements that maximize the ADC bandwidth.
IN
Figure 6. Recommended Front End Circuit for
Input Frequencies Between 100MHz and 250MHz
ANALOG
Figure 7. Recommended Front End Circuit for
Input Frequencies Between 250MHz and 500MHz
+
ANALOG
INPUT
Figure 8. Recommended Front End Circuit for
Input Frequencies Above 500MHz
ANALOG
INPUT
and A
INPUT
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
IN
T1 = MA/COM ETC1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
T1 = MA/COM ETC1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
–
T1 = MA/COM ETC1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
T1
T1
inputs each have two pins to reduce
U
T1
25Ω
25Ω
25Ω
25Ω
U
25Ω
25Ω
0.1µF
4.7nH
4.7nH
0.1µF
0.1µF
12Ω
12Ω
IN
+
and the two A
W
2.2µF
2pF
2.2µF
V
A
A
A
A
CM
2.2µF
V
IN
IN
IN
IN
8pF
A
A
A
A
CM
IN
IN
IN
IN
+
+
–
–
V
A
A
A
A
CM
+
+
–
–
IN
IN
IN
IN
+
+
–
–
LTC2220/
LTC2221
LTC2220/
LTC2221
LTC2220/
LTC2221
22201 F08
22201 F07
U
22201 F06
IN
–
pins
Reference Operation
Figure 9 shows the LTC2220/LTC2221 reference circuitry
consisting of a 1.6V bandgap reference, a difference
amplifier and switching and control circuit. The internal
voltage reference can be configured for two pin selectable
input ranges of 2V (±1V differential) or 1V (±0.5V differ-
ential). Tying the SENSE pin to V
typing the SENSE pin to V
The 1.6V bandgap reference serves two functions: its
output provides a DC bias point for setting the common
mode voltage of any external input circuitry; additionally,
the reference is used with a difference amplifier to gener-
ate the differential reference levels needed by the internal
ADC circuitry. An external bypass capacitor is required for
the 1.6V reference output, V
frequency low impedance path to ground for internal and
external circuitry.
The difference amplifier generates the high and low refer-
ence for the ADC. High speed switching circuits are
connected to these outputs and they must be externally
bypassed. Each output has four pins: two each of REFHA
and REFHB for the high reference and two each of REFLA
and REFLB for the low reference. The multiple output pins
are needed to reduce package inductance. Bypass capaci-
tors must be connected as shown in Figure 9.
TIE TO V
TIE TO V
RANGE = 2 • V
CM
0.5V < V
DD
FOR 1V RANGE;
FOR 2V RANGE;
Figure 9. Equivalent Reference Circuit
SENSE
SENSE
1.6V
1µF
1µF
< 1V
FOR
LTC2220/LTC2221
2.2µF
2.2µF
0.1µF
0.1µF
SENSE
REFHA
REFHB
REFLB
REFLA
V
CM
CM
LTC2220/LTC2221
CONTROL
4Ω
DETECT
selects the 1V range.
RANGE
CM
AND
DD
. This provides a high
1.6V BANDGAP
DIFF AMP
REFERENCE
selects the 2V range;
INTERNAL ADC
HIGH REFERENCE
INTERNAL ADC
LOW REFERENCE
1V
BUFFER
0.5V
22201 F09
21
22201fa