SBAS601H December   2012  – July 2014 AFE4400

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Family Options
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 Handling Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Timing Requirements: Supply Ramp and Power-Down
    8. 7.8 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Receiver Channel
        1. 8.3.1.1 Receiver Front-End
        2. 8.3.1.2 Ambient Cancellation Scheme and Second Stage Gain Block
        3. 8.3.1.3 Receiver Control Signals
        4. 8.3.1.4 Receiver Timing
      2. 8.3.2 Clocking and Timing Signal Generation
      3. 8.3.3 Timer Module
        1. 8.3.3.1 Using the Timer Module
      4. 8.3.4 Receiver Subsystem Power Path
      5. 8.3.5 Transmit Section
        1. 8.3.5.1 Transmitter Power Path
        2. 8.3.5.2 LED Power Reduction During Periods of Inactivity
    4. 8.4 Device Functional Modes
      1. 8.4.1 ADC Operation and Averaging Module
        1. 8.4.1.1 Operation
      2. 8.4.2 Diagnostics
        1. 8.4.2.1 Photodiode-Side Fault Detection
        2. 8.4.2.2 Transmitter-Side Fault Detection
        3. 8.4.2.3 Diagnostics Module
    5. 8.5 Programming
      1. 8.5.1 Serial Programming Interface
      2. 8.5.2 Reading and Writing Data
        1. 8.5.2.1 Writing Data
        2. 8.5.2.2 Reading Data
        3. 8.5.2.3 Multiple Data Reads and Writes
        4. 8.5.2.4 Register Initialization
        5. 8.5.2.5 AFE SPI Interface Design Considerations
    6. 8.6 Register Maps
      1. 8.6.1 AFE Register Map
      2. 8.6.2 AFE Register Description
  9. 9 Applications and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7 Specifications

7.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)(1)
MIN MAX UNIT
RX_ANA_SUP, RX_DIG_SUP to RX_ANA_GND, RX_DIG_GND –0.3 4 V
TX_CTRL_SUP, LED_DRV_SUP to LED_DRV_GND –0.3 6 V
RX_ANA_GND, RX_DIG_GND to LED_DRV_GND –0.3 0.3 V
Analog inputs RX_ANA_GND – 0.3 RX_ANA_SUP + 0.3 V
Digital inputs RX_DIG_GND – 0.3 RX_DIG_SUP + 0.3 V
TXP, TXN pins –0.3 Minimum [6, (LED_DRV_SUP + 0.3)] V
Input current to any pin except supply pins(2) ±7 mA
Input current Momentary ±50 mA
Continuous ±7 mA
Operating temperature range 0 70 °C
Maximum junction temperature, TJ 125 °C
(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) Input terminals are diode-clamped to the power-supply rails. Input signals that can swing beyond the supply rails must be current-limited to 10 mA or less.

7.2 Handling Ratings

MIN MAX UNIT
Tstg Storage temperature range –60 150 °C
V(ESD) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins(1) –1000 1000 V
Charged device model (CDM), per JEDEC specification JESD22-C101, all pins(2) –250 250
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

7.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)
PARAMETER MIN MAX UNIT
SUPPLIES
RX_ANA_SUP AFE analog supply 2.0 3.6 V
RX_DIG_SUP AFE digital supply 2.0 3.6 V
TX_CTRL_SUP Transmit controller supply 3.0 5.25 V
LED_DRV_SUP Transmit LED driver supply H-bridge or common anode configuration [3.0 or (1.0 + VLED + VCABLE)(1)(2), whichever is greater] 5.25 V
Difference between LED_DRV_SUP and TX_CTRL_SUP –0.3 0.3 V
TEMPERATURE
Specified temperature range 0 70 °C
Storage temperature range –60 150 °C
(1) VLED refers to the maximum voltage drop across the external LED (at maximum LED current) connected between the TXP and TXN pins (in H-bridge mode) and from the TXP and TXN pins to LED_DRV_SUP (in the common anode configuration).
(2) VCABLE refers to voltage drop across any cable, connector, or any other component in series with the LED.

7.4 Thermal Information

THERMAL METRIC(1) AFE4400 UNIT
RHA (VQFN)
40 PINS
RθJA Junction-to-ambient thermal resistance 35 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 31
RθJB Junction-to-board thermal resistance 26
ψJT Junction-to-top characterization parameter 0.1
ψJB Junction-to-board characterization parameter n/a
RθJC(bot) Junction-to-case (bottom) thermal resistance n/a
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.

7.5 Electrical Characteristics

Minimum and maximum specifications are at TA = 0°C to 70°C, typical specifications are at TA = 25°C. All specifications are at RX_ANA_SUP = RX_DIG_SUP = 3 V, TX_CTRL_SUP = LED_DRV_SUP = 3.3 V, stage 2 amplifier disabled, and fCLK = 8 MHz, unless otherwise noted.
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
PERFORMANCE (Full-Signal Chain)
IIN_FS Full-scale input current RF = 10 kΩ 50 µA
RF = 25 kΩ 20 µA
RF = 50 kΩ 10 µA
RF = 100 kΩ 5 µA
RF = 250 kΩ 2 µA
RF = 500 kΩ 1 µA
RF = 1 MΩ 0.5 µA
PRF Pulse repetition frequency 62.5 5000 SPS
DCPRF PRF duty cycle 25%
CMRR Common-mode rejection ratio fCM = 50 Hz and 60 Hz, LED1 and LED2 with RSERIES = 500 kΩ, RF = 500 kΩ 75 dB
fCM = 50 Hz and 60 Hz, LED1-AMB and LED2-AMB with RSERIES = 500 kΩ,
RF = 500 kΩ		 95 dB
PSRR Power-supply rejection ratio fPS = 50 Hz, 60 Hz at PRF = 200 Hz 100 dB
fPS = 50 Hz, 60 Hz at PRF = 600 Hz 106 dB
PSRRLED PSRR, transmit LED driver With respect to ripple on LED_DRV_SUP 75 dB
PSRRTx PSRR, transmit control With respect to ripple on TX_CTRL_SUP 60 dB
PSRRRx PSRR, receiver With respect to ripple on RX_ANA_SUP and RX_DIG_SUP 60 dB
Total integrated noise current, input-referred (receiver with transmitter loop back,
0.1-Hz to 5-Hz bandwidth)		 RF = 100 kΩ, PRF = 600 Hz, duty cycle = 5% 36 pARMS
RF = 500 kΩ, PRF = 600 Hz, duty cycle = 5% 13 pARMS
NFB Noise-free bits (receiver with transmitter loop back, 0.1-Hz to 5-Hz bandwidth) RF = 100 kΩ, PRF = 600 Hz, duty cycle = 5% 14.3 Bits
RF = 500 kΩ, PRF = 600 Hz, duty cycle = 5% 13.5 Bits
RECEIVER FUNCTIONAL BLOCK LEVEL SPECIFICATION
Total integrated noise current, input referred (receiver alone) over 0.1-Hz to 5-Hz bandwidth RF = 500 kΩ, ambient cancellation enabled, stage 2 gain = 4, PRF = 1200 Hz,
LED duty cycle = 25%		 1.4 pARMS
RF = 500 kΩ, ambient cancellation enabled, stage 2 gain = 4, PRF = 1200 Hz,
LED duty cycle = 5%		 5 pARMS
I-V TRANSIMPEDANCE AMPLIFIER
G Gain RF = 10 kΩ to 1 MΩ See the Receiver Channel section for details V/µA
Gain accuracy ±7%
Feedback resistance RF 10k, 25k, 50k, 100k, 250k,
500k, and 1M		 Ω
Feedback resistor tolerance RF ±20%
Feedback capacitance CF 5, 10, 25, 50, 100, and 250 pF
Feedback capacitor tolerance CF ±20%
Full-scale differential output voltage 1 V
Common-mode voltage on input pins Set internally 0.9 V
External differential input capacitance Includes equivalent capacitance of photodiode, cables, EMI filter, and so forth 10 1000 pF
Shield output voltage, VCM With a 1-kΩ series resistor and a 10-nF decoupling capacitor to ground 0.9 V
AMBIENT CANCELLATION STAGE
Gain 0, 3.5, 6, 9.5, and 12 dB
Current DAC range 0 10 µA
Current DAC step size 1 µA
LOW-PASS FILTER
Low-pass corner frequency 3-dB attenuation 500 Hz
Pass-band attenuation, 2 Hz to 10 Hz Duty cycle = 25% 0.004 dB
Duty cycle = 10% 0.041 dB
Filter settling time After diagnostics mode 28 ms
ANALOG-TO-DIGITAL CONVERTER
Resolution 22 Bits
Sample rate See the ADC Operation and Averaging Module section 4 × PRF SPS
ADC full-scale voltage ±1.2 V
ADC conversion time See the ADC Operation and Averaging Module section 50 PRF / 4 µs
ADC reset time 2 tCLK
TRANSMITTER
Output current range Selectable, 0 to 50
(see the LEDCNTRL: LED Control Register for details)		 mA
LED current DAC error ±10%
Output current resolution 8 Bits
Transmitter noise dynamic range,
over 0.1-Hz to 5-Hz bandwidth		 At 5-mA output current 95 dB
At 25-mA output current 95 dB
At 50-mA output current 95 dB
Voltage on TXP (or TXN) pin when low-side switch connected to TXP (or TXN) turns on At 50-mA output current 1.0 + (voltage drop across LED, cable, and so forth) to 5.25 V
Minimum sample time of LED1 and LED2 pulses 50 µs
LED current DAC leakage current LED_ON = 0 1 µA
LED_ON = 1 50 µA
LED current DAC linearity Percent of full-scale current 0.5%
Output current settling time
(with resistive load)		 From zero current to 50 mA 7 µs
From 50 mA to zero current 7 µs
DIAGNOSTICS
Duration of diagnostics state machine Start of diagnostics after the DIAG_EN register bit is set.
End of diagnostic is indicated by DIAG_END going high.		 16 ms
Open fault resistance > 100 kΩ
Short fault resistance < 10 kΩ
INTERNAL OSCILLATOR
fCLKOUT CLKOUT frequency With an 8-MHz crystal connected to the XIN, XOUT pins 4 MHz
CLKOUT duty cycle 50%
Crystal oscillator start-up time With an 8-MHz crystal connected to the XIN, XOUT pins 200 µs
EXTERNAL CLOCK
Maximum allowable external clock jitter For SPO2 applications 50 ps
For optical heart rate only 1000 ps
External clock input frequency ±10% 8 MHz
External clock input voltage Voltage input high (VIH) 0.75 × RX_DIG_SUP V
Voltage input low (VIL) 0.25 × RX_DIG_SUP V
TIMING
Wake-up time from complete power-down 1000 ms
Wake-up time from Rx power-down 100 µs
Wake-up time from Tx power-down 1000 ms
tRESET Active low RESET pulse duration 1 ms
tDIAGEND DIAG_END pulse duration at the completion of diagnostics 4 CLKOUT cycles
tADCRDY ADC_RDY pulse duration 1 CLKOUT cycle
DIGITAL SIGNAL CHARACTERISTICS
VIH Logic high input voltage AFE_PDN, SCLK, SPISIMO, SPISTE, RESET 0.8 DVDD DVDD + 0.1 V
VIL Logic low input voltage AFE_PDN, SCLK, SPISIMO, SPISTE, RESET –0.1 0.2 DVDD V
IIN Logic input current 0 V < VDigitalInput < DVDD –10 10 µA
VOH Logic high output voltage DIAG_END, LED_ALM, PD_ALM, SPISOMI, ADC_RDY, CLKOUT 0.9 DVDD > (RX_DIG_SUP –
0.2 V)		 V
VOL Logic low output voltage DIAG_END, LED_ALM, PD_ALM, SPISOMI, ADC_RDY, CLKOUT < 0.4 0.1 DVDD V
SUPPLY CURRENT
Receiver analog supply current RX_ANA_SUP = 3.0 V, with 8-MHz clock running, Rx stage 2 disabled 0.6 mA
RX_ANA_SUP = 3.0 V, with 8-MHz clock running, Rx stage 2 enabled 0.7 mA
Receiver digital supply current RX_DIG_SUP = 3.0 V 0.27 mA
LED_DRV_SUP LED driver supply current With zero LED current setting 55 µA
TX_CTRL_SUP Transmitter control supply current 15 µA
Complete power-down (using AFE_PDN pin) Receiver current only
(RX_ANA_SUP)		 3 µA
Receiver current only
(RX_DIG_SUP)		 3 µA
Transmitter current only
(LED_DRV_SUP)		 1 µA
Transmitter current only
(TX_CTRL_SUP)		 1 µA
Power-down Rx alone Receiver current only
(RX_ANA_SUP)		 220 µA
Receiver current only
(RX_DIG_SUP)		 220 µA
Power-down Tx alone Transmitter current only
(LED_DRV_SUP)		 2 µA
Transmitter current only
(TX_CTRL_SUP)		 2 µA
POWER DISSIPATION
Quiescent power dissipation Normal operation (excluding LEDs) 2.84 mW
Power-down 0.1 mW
Power-down with the AFE_PDN pin LED_DRV_SUP LED_DRV_SUP current value.
Does not include LED current.		 1 µA
TX_CTRL_SUP 1 µA
RX_ANA_SUP 5 µA
RX_DIG_SUP 0.1 µA
Power-down with the PDNAFE register bit LED_DRV_SUP LED_DRV_SUP current value.
Does not include LED current.		 1 µA
TX_CTRL_SUP 1 µA
RX_ANA_SUP 15 µA
RX_DIG_SUP 20 µA
Power-down Rx LED_DRV_SUP LED_DRV_SUP current value.
Does not include LED current.		 50 µA
TX_CTRL_SUP 15 µA
RX_ANA_SUP 220 µA
RX_DIG_SUP 220 µA
Power-down Tx LED_DRV_SUP LED_DRV_SUP current value.
Does not include LED current.		 2 µA
TX_CTRL_SUP 2 µA
RX_ANA_SUP 600 µA
RX_DIG_SUP 230 µA
After reset, with 8-MHz clock running LED_DRV_SUP LED_DRV_SUP current value.
Does not include LED current.		 55 µA
TX_CTRL_SUP 15 µA
RX_ANA_SUP 600 µA
RX_DIG_SUP 230 µA
With stage 2 mode enabled and 8-MHz clock running LED_DRV_SUP LED_DRV_SUP current value.
Does not include LED current.		 55 µA
TX_CTRL_SUP 15 µA
RX_ANA_SUP 700 µA
RX_DIG_SUP 270 µA

7.6 Timing Requirements

PARAMETER MIN TYP MAX UNIT
tCLK Clock frequency on the XIN pin 8 MHz
tSCLK Serial shift clock period 62.5 ns
tSTECLK STE low to SCLK rising edge, setup time 10 ns
tCLKSTEH,L SCLK transition to SPI STE high or low 10 ns
tSIMOSU SIMO data to SCLK rising edge, setup time 10 ns
tSIMOHD Valid SIMO data after SCLK rising edge, hold time 10 ns
tSOMIPD SCLK falling edge to valid SOMI, setup time 17 ns
tSOMIHD SCLK rising edge to invalid data, hold time 0.5 tSCLK
tim_serial_read_bas601.gif
1. The SPI_READ register bit must be enabled before attempting a register read.
2. Specify the register address whose contents must be read back on A[7:0].
3. The AFE outputs the contents of the specified register on the SPISOMI pin.
Figure 1. Serial Interface Timing Diagram, Read Operation123(1)(2)(3)
tim_serial_write_bas601.gifFigure 2. Serial Interface Timing Diagram, Write Operation

7.7 Timing Requirements: Supply Ramp and Power-Down

PARAMETER VALUE
t1 Time between Rx and Tx supplies ramping up Keep as small as possible (for example, ±10 ms)
t2 Time between both supplies stabilizing and high-going RESET edge > 100 ms
t3 RESET pulse duration > 0.5 ms
t4 Time between RESET and SPI commands > 1 µs
t5 Time between SPI commands and the ADC_RESET which corresponds to valid data > 3 ms of cumulative sampling time in each phase(1)(2)(3)
t6 Time between RESET pulse and high-accuracy data coming out of the signal chain > 1 s(3)
t7 Time from AFE_PDN high-going edge and RESET pulse(4) > 100 ms
t8 Time from AFE_PDN high-going edge (or PDN_AFE bit reset) to high-accuracy data coming out of the signal chain > 1 s(3)
(1) This time is required for each of the four switched RC filters to fully settle to the new settings. The same time is applicable whenever there is a change to any of the signal chain controls (for example, LED current setting, TIA gain, and so forth).
(2) If the SPI commands involve a change in the TX_REF value from its default, then there is additional wait time of approximately 1 s (for a 2.2-µF decoupling capacitor on the TX_REF pin).
(3) Dependent on the value of the capacitors on the BG and TX_REF pins. The 1-s wait time is necessary when the capacitors are 2.2 µF and scale down proportionate to the capacitor value. A very low capacitor (for example, 0.1 µF) on these pins causes the transmitter dynamic range to reduce to approximately 100 dB.
(4) After an active power-down from AFE_PDN, the device should be reset using a low-going RESET pulse.
spply_rmp_hrdwr_pwr_dwn_tmng_SBAS602.gifFigure 3. Supply Ramp and Hardware Power-Down Timing
spply_rmp_sftwr_SBAS602.gifFigure 4. Supply Ramp and Software Power-Down Timing

7.8 Typical Characteristics

Minimum and maximum specifications are at TA = 0°C to 70°C. Typical specifications are at TA = 25°C, RX_ANA_SUP = RX_DIG_SUP = 3.0 V, TX_CTRL_SUP = LED_DRV_SUP = 3.3 V, and fCLK = 8 MHz, unless otherwise noted.
C001_SBAS601.png
Figure 5. Total Rx Current vs Rx Supply Voltage
C003_SBAS601.png
Figure 7. LED_DRV_SUP Current vs
LED_DRV_SUP Voltage
C005_SBAS601.png
Figure 9. Input-Referred Noise Current vs
Pleth Current (PRF = 300 Hz)
C007_SBAS601.png
Figure 11. Input-Referred Noise Current vs
Pleth Current (PRF = 1200 Hz)
C009_SBAS601.png
Figure 13. Input-Referred Noise Current vs
Pleth Current (PRF = 5000 Hz)
C011_SBAS601.png
Figure 15. Noise-Free Bits vs Pleth Current
(PRF = 300 Hz)
C013_SBAS601.png
Figure 17. Noise-Free Bits vs Pleth Current
(PRF = 1200 Hz)
C015_SBAS601.png
Figure 19. Noise-Free Bits vs Pleth Current
(PRF = 5000 Hz)
C021_SBAS601.png
Figure 21. Transmitter DAC Current Step Error
(50 mA, Max)
C023_SBAS601.png
Figure 23. LED Current with Tx DAC Setting = 10
(2 mA)
C025_SBAS601.png
Figure 25. LED Current with Tx DAC Setting = 51
(10 mA)
C027_SBAS601.png
Figure 27. LED Current with Tx DAC Setting = 255
(50 mA)
C029_SBAS601.png
Figure 29. Transmitter Supplies vs TX_REF
C031_SBAS601.png
Figure 31. Input-Referred Noise vs Temperature
C033_SBAS601.png
Figure 33. Filter Response vs Duty Cycle
C002_SBAS601.png
Figure 6. TX_CTRL_SUP Current vs
TX_CTRL_SUP Voltage
C004_SBAS601.png
Figure 8. Input-Referred Noise Current vs
Pleth Current (PRF = 100 Hz)
C006_SBAS601.png
Figure 10. Input-Referred Noise Current vs
Pleth Current (PRF = 600 Hz)
C008_SBAS601.png
Figure 12. Input-Referred Noise Current vs
Pleth Current (PRF = 2500 Hz)
C010_SBAS601.png
Figure 14. Noise-Free Bits vs Pleth Current
(PRF = 100 Hz)
C012_SBAS601.png
Figure 16. Noise-Free Bits vs Pleth Current
(PRF = 600 Hz)
C014_SBAS601.png
Figure 18. Noise-Free Bits vs Pleth Current
(PRF = 2500 Hz)
C016_SBAS601.png
Figure 20. Transmitter Dynamic Range
(5-Hz BW)
C022_SBAS601.png
Figure 22. Transmitter Current Linearity
(50-mA Range)
C024_SBAS601.png
Figure 24. LED Current with Tx DAC Setting = 25
(5 mA)
C026_SBAS601.png
Figure 26. LED Current with Tx DAC Setting = 102
(20 mA)
C028_SBAS601.png
Figure 28. Receiver Supplies vs PRF
C030_SBAS601.png
Figure 30. Power Supplies vs Temperature
C032_SBAS601.png
Figure 32. Noise-Free Bits vs Temperature