Datasheet

AFE4490
www.ti.com SBAS602F –DECEMBER 2012–REVISED OCTOBER 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
0 0 0 0 AMBDAC[3:0] 0 0
CNRSEL EN
D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
0 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 = 3.5 dB, or linear gain of 1.5 110 = Do not use
010 = 6 dB, or linear gain of 2 111 = Do not use
011 = 9.5 dB, or linear gain of 3
Bits D[7:3] CF_LED2[4:0]: Program C
F
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 C
F
settings is also supported by setting multiple bits to
'1'. For example, to obtain C
F
= 100 pF, set D[7:3] = 01111.
Bits D[2:0] RF_LED2[2:0]: Program R
F
for LED2
000 = 500 kΩ 100 = 25 kΩ
001 = 250 kΩ 101 = 10 kΩ
010 = 100 kΩ 110 = 1 MΩ
011 = 50 kΩ 111 = None
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