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LTC1278

12-Bit, 500ksps Sampling A/D Converter with Shutdown

Linear Technology 

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TI I G CHARACTERISTICS (Note 5)

The q indicates specifications which apply over the full operating

temperature range; all other limits and typicals TA = 25°C.

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

Note 2: All voltage values are with respect to ground with DGND and

AGND wired together (unless otherwise noted).

Note 3: When these pin voltages are taken below VSS (ground for unipolar

mode) or above VDD, they will be clamped by internal diodes. This product

can handle input currents greater than 60mA below VSS (ground for

unipolar mode) or above VDD without latch-up.

Note 4: When these pin voltages are taken below VSS (ground for unipolar

mode), they will be clamped by internal diodes. This product can handle

input currents greater than 60mA below VSS (ground for unipolar mode)

without latch-up. These pins are not clamped to VDD.

Note 5: AVDD = DVDD = VDD = 5V, (VSS = – 5V for bipolar mode), fSAMPLE =

400kHz (LTC1278-4), 500kHz (LTC1278-5), tr = tf = 5ns unless otherwise

specified.

Note 6: Linearity, offset and full-scale specifications apply for unipolar and

bipolar modes.

LTC1278

Note 7: Integral nonlinearity is defined as the deviation of a code from a

straight line passing through the actual endpoints of the transfer curve. The

deviation is measured from the center of the quantization band.

Note 8: Bipolar offset is the offset voltage measured from – 1/2LSB when

the output code flickers between 0000 0000 0000 and 1111 1111 1111.

Note 9: Guaranteed by design, not subject to test.

Note 10: Recommended operating conditions.

Note 11: AIN must not exceed VDD or fall below VSS by more than 50mV for

specified accuracy. Therefore the minimum supply voltage for the unipolar

mode is 4.95V. The minimum for the bipolar mode is 4.75V, – 2.45V.

Note 12: The falling CONVST edge starts a conversion. If CONVST returns

high at a bit decision point during the conversion it can create small errors.

For best performance ensure that CONVST returns high either within 120ns

after conversion start (i.e., before the first bit decision) or after BUSY rises

(i.e., after the last bit test). See mode 1a and 1b (Figures 12 and 13) timing

diagrams.

TYPICAL PERFORMANCE CHARACTERISTICS

Integral Nonlinearity vs

Output Code

1.0

fSAMPLE = 500kHz

0.5

Differential Nonlinearity vs

Output Code

1.0

fSAMPLE = 500kHz

0.5

0

0

–0.5

–0.5

–1.0

0 512 1024 1536 2048 2560 3072 3584 4096

CODE

LT1278 G1

–1.0

0 512 1024 1536 2048 2560 3072 3584 4096

CODE

LT1278 G2

ENOBs and S/(N + D) vs

Input Frequency

12

11

10

NYQUIST

9

FREQUENCY

8

7

6

5

4

3

2

1 fSAMPLE = 500kHz

0

10k

100k

INPUT FREQUENCY (Hz)

74

68

62

56

1M 2M

LT1278 G4

5

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