LTC2487



2487fa

Rejection Mode (FA, FB)

The LTC2487 includes a high accuracy on-chip oscillator

with no required external components. Coupled with an

integrated fourth order digital low pass filter, the LTC2487

rejects line frequency noise. In the default mode, the

LTC2487 simultaneously rejects 50Hz and 60Hz by at least

87dB. If more rejection is required, the LTC2487 can be

configured to reject 50Hz or 60Hz to better than 110dB.

Speed Mode (SPD)

Every conversion cycle, two conversions are combined

to remove the offset (default mode). This result is free

from offset and drift. In applications where the offset is

not critical, the auto-calibration feature can be disabled

with the benefit of twice the output rate.

While operating in the 2x mode (SPD = 1), the linearity

and full-scale errors are unchanged from the 1x mode

performance. In both the 1x and 2x mode there is no

latency. This enables input steps or multiplexer changes

to settle in a single conversion cycle, easing system over-

head and increasing the effective conversion rate. During

temperature measurements, the 1x mode is always used

independent of the value of SPD.

GAIN (GS2, GS1, GS0)

The input referred gain of the LTC2487 is adjustable

from 1 to 256 (see Tables 5a and 5b). With a gain of 1,

mode input range is rail-to-rail. As the gain is increased,

but the common mode input range remains rail-to-rail.

As the differential gain is increased, low level voltages

are digitized with greater resolution. At a gain of 256, the

LTC2487 digitizes an input signal range of ±9.76mV with

over 16,000 counts.

Temperature Sensor

The LTC2487 includes an integrated temperature sen-

sor. The temperature sensor is selected by setting

IM = 1. The ADC internally connects to the temperature

sensor and performs a conversion.

The digital output is proportional to the absolute tem-

perature of the device. This feature allows the converter

to perform cold junction compensation for external

thermocouples or continuously remove the temperature

effects of external sensors.

The internal temperature sensor output is 28mV at 27°C

applicaTions inForMaTion

GAIN

1

4

8

16

32

64

128

256

UNIT

Input Span

±2.5

±0.625

±0.312

±0.156

±78m

±39m

±19.5m

±9.76m

V

LSB

38.1

9.54

4.77

2.38

1.19

0.596

0.298

0.149

µV

Noise Free Resolution*

65536

65536

65536

65536

65536

65536

32768

16384

Counts

Gain Error

5

5

5

5

5

5

5

8

ppm of FS

Offset Error

0.5

0.5

0.5

0.5

0.5

0.5

0.5

0.5

µV

GAIN

1

2

4

8

16

32

64

128

UNIT

Input Span

±2.5

±1.25

±0.625

±0.312

±0.156

±78m

±39m

±19.5m

V

LSB

38.1

19.1

9.54

4.77

2.38

1.19

0.596

0.298

µV

Noise Free Resolution*

65536

65536

65536

65536

65536

65536

45875

22937

Counts

Gain Error

5

5

5

5

5

5

5

5

ppm of FS

Offset Error

200

200

200

200

200

200

200

200

µV

*The resolution in counts is calculated as the FS divided by LSB or the RMS noise value, whichever is larger.