AFE4490 datasheet(55/70 Pages) TI

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AFE4490

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SBAS602B – DECEMBER 2012 – REVISED FEBRUARY 2013

TIA_AMB_GAIN: Transimpedance Amplifier and Ambient Cancellation Stage Gain Register

(Address = 21h, Reset Value = 0000h)

D23

D22

D21

D20

D19

D18

D17

D16

D15

D14

D13

D12

FLTR

STAGE2

AMBDAC[3:0]

CNRSEL

D11

D10

STG2GAIN[2:0]

CF_LED2[4:0]

RF_LED2[2:0]

This register configures the ambient light cancellation amplifier gain, cancellation current, and filter corner

frequency.

Bits D[23:20]

Must be '0'

Bits D[19:16]

AMBDAC[3:0]: Ambient DAC value

These bits set the value of the cancellation current.

0000 = 0 µA (default after reset)

1000 = 8 µA

0001 = 1 µA

1001 = 9 µA

0010 = 2 µA

1010 = 10 µA

0011 = 3 µA

1011 = Do not use

0100 = 4 µA

1100 = Do not use

0101 = 5 µA

1101 = Do not use

0110 = 6 µA

1110 = Do not use

0111 = 7 µA

1111 = Do not use

Bit D15

FLTRCNRSEL: Filter corner selection

0 = 500-Hz filter corner (default after reset)

1 = 1000-Hz filter corner

Bit D14

STAGE2EN: Stage 2 enable

0 = Stage 2 is bypassed (default after reset)

1 = Stage 2 is enabled with the gain value specified by the STG2GAIN[2:0] bits

Bits D[13:11]

Must be '0'

Bits D[10:8]

STG2GAIN[2:0]: Stage 2 gain setting

000 = 0 dB, or linear gain of 1 (default after

100 = 12 dB, or linear gain of 4

reset)

101 = Do not use

001 = 3 dB, or linear gain of 1.414

110 = Do not use

010 = 6 dB, or linear gain of 2

111 = Do not use

011 = 9 dB, or linear gain of 2.818

Bits D[7:3]

CF_LED2[4:0]: Program CF for LED2

00000 = 5 pF (default after reset)

00100 = 25 pF + 5 pF

00001 = 5 pF + 5 pF

01000 = 50 pF + 5 pF

00010 = 15 pF + 5 pF

10000 = 150 pF + 5 pF

Note that any combination of these CF settings is also supported by setting multiple bits to

'1'. For example, to obtain CF = 100 pF, set D[7:3] = 01111.

Bits D[2:0]

RF_LED2[2:0]: Program RF for LED2

000 = 500 k

100 = 25 k

001 = 250 k

101 = 10 k

010 = 100 k

110 = 1 M

011 = 50 k

111 = None

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