Datasheet
AFE5808
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SLOS688C –SEPTEMBER 2010–REVISED APRIL 2012
Table 4. VCA Register Map (continued)
ADDRESS ADDRESS Default
FUNCTION DESCRIPTION
(DEC) (HEX) Value
57[1:0] 0x39[1:0] 0 CH1_LNA_GAIN_CNTL 00: 18dB;
01: 24dB;
57[3:2] 0x39[3:2] 0
10: 12dB;
CH2_LNA_GAIN_CNTL
11: Reserved
REG52[15] should be set as '1'
57[5:4] 0x39[5:4] 0 CH3_LNA_GAIN_CNTL 00: 18dB;
01: 24dB;
57[7:6] 0x39[7:6] 0 CH4_LNA_GAIN_CNTL
10: 12dB;
57[9:8] 0x39[9:8] 0 CH5_LNA_GAIN_CNTL
11: Reserved
REG52[15] should be set as '1'
57[11:10] 0x39[11:1 0 CH6_LNA_GAIN_CNTL
0]
57[13:12] 0x39[13:1 0 CH7_LNA_GAIN_CNTL
2]
57[15:14] 0x39[15:1 0 CH8_LNA_GAIN_CNTL
4]
59[3:2] 0x3B[3:2] 0 HPF_LNA 00: 100KHz;
01: 50Khz;
10: 200Khz;
11: 150KHz with 0.015uF on INMx
59[6:4] 0x3B[6:4] 0 DIG_TGC_ATT_GAIN 000: 0dB attenuation;
001: 6dB attenuation;
N: ~N×6dB attenuation when 59[7] = 1
59[7] 0x3B[7] 0 DIG_TGC_ATT 0: disable digital TGC attenuator;
1: enable digital TGC attenuator
59[8] 0x3B[8] 0 CW_SUM_AMP_PDN 0: Power down;
1: Normal operation
Note: 59[8] is only effective in TGC test mode.
59[9] 0x3B[9] 0 PGA_TEST_MODE 0: Normal CW operation;
1: PGA outputs appear at CW outputs
AFE5808 VCA Register Description
LNA Input Impedances Configuration (Active Termination Programmability)
Different LNA input impedances can be configured through the register 52[4:0]. By enabling and disabling the
feedback resistors between LNA outputs and ACTx pins, LNA input impedance is adjustable accordingly. Table 5
describes the relationship between LNA gain and 52[4:0] settings. The input impedance settings are the same for
both TGC and CW paths.
The AFE5808 also has 4 preset active termination impedances as described in 52[7:6]. An internal decoder is
used to select appropriate resistors corresponding to different LNA gain.
Table 5. Register 52[4:0] Description
52[4:0]/0x34[4:0] FUNCTION
00000 No feedback resistor enabled
00001 Enables 450 Ω feedback resistor
00010 Enables 900 Ω feedback resistor
00100 Enables 1800 Ω feedback resistor
01000 Enables 3600 Ω feedback resistor
10000 Enables 4500 Ω feedback resistor
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