TSA1203IFT-E データシートの表示（PDF） - STMicroelectronics

部品番号

コンポーネント説明

メーカー

TSA1203IFT-E

Dual-channel 12-bit 40Msps 215mW A/D converter

STMicroelectronics 

TSA1203

Figure 24. External reference setting

1kΩ

1.2V

330pF 10nF 4.7μF

VCCA VREFP

VIN

TSA1203

TS821

TS4041

VINB

VREFM

external

reference

Application information

8.3

Driving the differential analog inputs

The TSA1203 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 describes the schematics. The input signal is fed to the primary of the transformer,

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 0.46V. 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 Mini

circuits. You might also use a higher impedance ratio (1:2 or 1:4) to reduce the driving

requirement on the analog source.

Each analog input can drive a 1.4 Vpp amplitude input signal, so the resulting differential

amplitude is 2.8 Vpp.

Figure 25. Differential input configuration with transformer

Analog source

ADT1-1

1:1

50Ω

33pF

VIN

TSA1203

channels

VINB I or Q

INCM

330pF 10nF 470nF

17/30

Share Link: