Datasheet

Device
Digital
Filter
SPI
+
Buffer
4GADC
+
TIA
+
Stage 2
Gain
Photodiode
C
PD
Filter
SPI Interface
Diagnostics
Timing
Controller
OSC
8 MHz
Diagnostic
Signals
INN
INP
RX_ANA_GND
VCM
DNC
(1)
DNC
(1)
BG
VSS
TX_REF
TX_CTRL_SUP
LED_DRV_GND LED_DRV_GND
TXN
TXP
LED_DRV_GND
LED_DRV_SUP LED_DRV_SUP
RX_DIG_GND
AFE_PDN
DIAG_END
LED_ALM
PD_ALM
SCLK
SPISOMI
SPISIMO
SPISTE
ADC_RDY
RESET
CLKOUT
RX_DIG_SUP
RX_DIG_GND
RX_ANA_SUP DNC DNC
RX_ANA_GND
XOUT
XIN
RX_ANA_SUP
RX_ANA_GND
DNC
(1)
Control
Reference
C
F
C
F
R
F
R
F
LED
Driver
LED Current
Control DAC
LED
C
r1.2 V
C
AFE4490
SBAS602F –DECEMBER 2012–REVISED OCTOBER 2013 www.ti.com
OVERVIEW
The AFE4490 is a complete analog front-end (AFE) solution targeted for pulse-oximeter applications. The device
consists of a low-noise receiver channel, an LED transmit section, and diagnostics for sensor and LED fault
detection. To ease clocking requirements and provide the low-jitter clock to the AFE, an oscillator is also
integrated that functions from an external crystal. The device communicates to an external microcontroller or host
processor using an SPI interface. Figure 53 shows a detailed block diagram for the AFE4490. The blocks are
described in more detail in the following sections.
Figure 53. Detailed Block Diagram
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