TSA1204IFT STMicroelectronics, TSA1204IFT Datasheet - Page 17

• Manufacturer Part Number: TSA1204IFT
• Description: IC CONV A/D 2-CH 12-BIT 48-TQFP
• Manufacturer: STMicroelectronics

Specifications of TSA1204IFT

• Number Of Bits: 12
• Sampling Rate (per Second): 20M
• Data Interface: Parallel
• Number Of Converters: 2
• Power Dissipation (max): 155mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-5435-2; TSA1204IFT

TSA1204
8.3
Driving the differential analog inputs
The TSA1204 is designed to deliver optimum performance when driven on differential
inputs. An RF transformer is an efficient way of achieving this high performance.
Figure 25
while the secondary drives both ADC inputs. The common mode voltage of the ADC (INCM)
is connected to the center-tap of the secondary of the transformer in order to bias the input
signal around this common voltage, internally set to 0.46 V. It determines the DC component
of the analog signal. Being a high impedance input, it acts as an I/O and can be externally
driven to adjust this DC component. The INCM is decoupled to maintain a low noise level on
this node. Our evaluation board is mounted with a 1:1 ADT1-1WT transformer from
Minicircuits. You might also use a higher impedance ratio (1:2 or 1:4) to reduce the driving
requirement on the analog signal source.
Each analog input can drive a 1.4 V
amplitude is 2.8 V
Figure 25. Differential input configuration with transformer
Figure 26. AC-coupled differential input
Figure 26
configuration. Both inputs V
can be let internal or fixed externally.
describes the schematics. The input signal is fed to the primary of the transformer,
represents the biasing of a differential input signal in AC-coupled differential input
Analog source
pp
50Ω
mode
common
.
50Ω
50Ω
IN
ADT1-1
and V
1:1
10nF
10nF
33pF
INB
pp
amplitude input signal, so the resulting differential
are centered around the common mode voltage, that
330pF
100kΩ
100kΩ
33pF
10nF
INCM
VINB
VIN
470nF
VIN
VINB
TSA1204
channels
INCM
I or Q
TSA1204
Application information
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