TSA1401IF View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

TSA1401IF

14-BIT, 20MSPS, 85mW A/D CONVERTER

STMicroelectronics 

APPLICATION INFORMATION

TSA1401

Fig. 11: Distortion vs. VREFP

Fin=5MHz;Fs=20Mhz;Icca=26mA;INCM=0.46V

-70

-75

-80

-85

THD

-90

SFDR

-95

-100

0.8 0.9

1

1.1 1.2 1.3 1.4

REFP (V)

An external reference voltage device may be used

for specific applications requiring even better

linearity, accuracy or enhanced temperature

behavior.

Using the STMicroelectronics TS821, TS4041-1.2

or TS431 Voltage Reference devices leads to

optimum performances when configured as

shown in Figure 12. The full scale is increased to

2.5Vpp differential and SNR and SINAD are

enhanced as shown in Figure 13 .

Fig. 12: External reference setting

1kΩ

REFMODE AVCC VREFP

VIN

TSA1401

VINB

VREFM

330pF 10nF 4.7µF

100Ω

TS4041

TS821 external

reference

In multi-channel applications, the high impedance

input of the references permits to drive several

ADCs with only one Voltage Reference device.

Fig. 13: Linearity vs. Fs at Fin=5MHz, using

TS4041 Icca optimised; VREFP=1.225V;

VREFM=GND; INCM=0.65V,

80

77

74

71

68

65

3

12.1

12

ENOB

11.9

11.8

SNR

11.7

SINAD

11.6

11.5

11.4

11.3

11.2

11.1

5 7 9 11 13 15 17 19 21

Fs (Mhz)

Fig. 14: Distortion vs. Fs at Fin=5MHz, using

TS4041 Icca optimised; VREFP=1.225V;

VREFM=GND; INCM=0.65V

-70

-75

-80

-85

THD

-90

SFDR

-95

-100

3 5 7 9 11 13 15 17 19 21

Fs (Mhz)

The magnitude of the analog input common

mode, CM should stay close to VREFP/2. Higher

level will introduce more distortion.

5.1.2 - Driving the analog input

The TSA1401 has been designed to be

differentially driven for better noise immunity.

Some measurements have been done with

single-ended signals. It degrades a little bit the

performances, with an SFDR of -75dBc and an

ENOB of 11.2 bits at 20Msps, Fin at 10MHz.

The switch-capacitor input structure of TSA1401,

presents a high input impedance (3.3kΩ at

Fs=20MHz) but not constant in time (see

equivalent input circuit Figure 15). Indeed at the

end of each conversion, the charge update of the

13/19

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