LTC1290C(Rev_C) View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LTC1290C
(Rev.:Rev_C)

Single Chip 12-Bit Data Acquisition System

Linear Technology 

LTC1290

APPLICATI S I FOR ATIO

0

fIN = 1kHz

fSAMPLE = 50.6kHz

–20

SNR = 73.25dB

–40

–60

–80

–100

–120

–140

0 4 8 12 16 20 24

FREQUENCY (kHz)

1290 • F17a

Figure 17a. LTC1290 FFT Plot

0 fIN = 25kHz

fSAMPLE = 50.6kHz

–20 SNR = 72.54dB

–40

–60

–80

–100

–120

–140

0 4 8 12 16 20 24

FREQUENCY (kHz)

1290 • F17b

Figure 17b. LTC1290 FFT Plot

12

fSAMPLE = 50.6kHz

11.6

11.2

10.8

10.4

10

9.6

9.2

8.8

0

20

40

60

80 100

FREQUENCY (kHz)

1290 F18

Figure 18. LTC1290 ENOB vs Input Frequency

fundamentals. This is classically referred to as

intermodulation distortion (IMD).

8. Overvoltage Protection

Applying signals to the analog MUX that exceed the

positive or negative supply of the device will degrade the

accuracy of the A/D and possibly damage the device. For

example this condition would occur if a signal is applied to

the analog MUX before power is applied to the LTC1290.

Another example is the input source is operating from

different supplies of larger value than the LTC1290. These

conditions should be prevented either with proper supply

sequencing or by use of external circuitry to clamp or

current limit the input source. As shown in Figure 20, a 1k

resistor is enough to stand off ±15V (15mA for one only

channel). If more than one channel exceeds the supplies

0

fIN1 = 5.1kHz

fIN2 = 5.6kHz

–20

fSAMPLE = 50.6kHz

–40

–60

–80

–100

–120

0 4 8 12 16 20 24

FREQUENCY (kHz)

1290 • F19

Figure 19. LTC1290 FFT Plot

then the following guidelines can be used. Limit the

current to 7mA per channel and 28mA for all channels.

This means four channels can handle 7mA of input current

each. Reducing the ACLK and SCLK frequencies from the

maximum of 4MHz and 2MHz, respectively, (see Typical

Peformance Characteristics curves Maximum ACLK Fre-

quency vs Source Resistance and Sample-and-Hold

Acquisition Time vs Source Resistance) allows the use of

1k

VIN

CH0

VCC

5V

22µF

LTC1290

DGND

V–

AGND

–5V

0.1µF

1290 F20

Figure 20. Overvoltage Protection for MUX

23

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