Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsData collecting ICsData acquisition IC - Analog front end (AFE) 22 Bit VQFN 40

LED2 Data

Amb (LED2) Data

LED1 Data

Amb (LED1) Data

AFE

SPI

(LED2 ± Amb) Data

(LED1 ± Amb) Data

Buffer ûADC

TIA

Stage 2

Gain

Photodiode

Digital Filter

SPI Interface

Diagnostic

PD Open or Short

Cable Off

LED Open or Short

LED

Driver

LED Current

Control

DAC

Timing

Controller

OSC

8 MHz

Diagnostic Signals

AFE

LED

Tx Supply

(3.0 V or 5.25 V)

Rx Supply

(2.0 V to 3.6 V)

LED2

AMB

LED2

LED1

AMB

LED1

Filter

AFE4490

www.ti.com

SBAS602F –DECEMBER 2012–REVISED OCTOBER 2013

Integrated Analog Front-End for Pulse Oximeters

Check for Samples: AFE4490

FEATURES

• Fully-Integrated Analog Front-End for

• Package: Compact QFN-40 (6 mm × 6 mm)

Pulse Oximeter Applications:

• Specified Temperature Range: –40°C to +85°C

– Flexible Pulse Sequencing and

Timing Control APPLICATIONS

• Transmit:

• Medical Pulse Oximeter Applications

– Integrated LED Driver

• Industrial Photometry Applications

(H-Bridge or Push/Pull)

DESCRIPTION

– 110-dB Dynamic Range Across Full Range

(Enables Low Noise at Low LED Current)

The AFE4490 is a fully-integrated analog front-end

(AFE) that is ideally suited for pulse-oximeter

– LED Current:

applications. The device consists of a low-noise

– Programmable Ranges of 50 mA, 75 mA,

receiver channel with a 22-bit analog-to-digital

100 mA, 150 mA, and 200 mA,

converter (ADC), an LED transmit section, and

Each with 8-Bit Current Resolution

diagnostics for sensor and LED fault detection. The

AFE4490 is a very configurable timing controller. This

– Low Power:

flexibility enables the user to have complete control of

– 100 µA + Average LED Current

the device timing characteristics. To ease clocking

– LED On-Time Programmability from

requirements and provide a low-jitter clock to the

(50 µs + Settle Time) to 4 ms

AFE4490, an oscillator is also integrated that

functions from an external crystal. The device

– Independent LED2 and LED1 Current

communicates to an external microcontroller or host

Reference

processor using an SPI™ interface.

• Receive Channel with High Dynamic Range:

The AFE4490 is a complete AFE solution packaged

– Input-Referred Noise:

in a single, compact QFN-40 package (6 mm ×

50 pA

RMS

(at 5-µA PD Current)

6 mm) and is specified over the operating

– 13.5 Noise-Free Bits (at 5-µA PD Current)

temperature range of –40°C to +85°C.

– Analog Ambient Cancellation Scheme with

Selectable 1-µA to 10-µA Ambient Current

– Low Power: < 2.3 mW at 3.0-V Supply

– Rx Sample Time: 50 µs to 4 ms

– I-V Amplifier with Seven Separate LED2 and

LED1 Programmable Feedback R and C

Settings

– Integrated Digital Ambient Estimation and

Subtraction

• Integrated Fault Diagnostics:

– Photodiode and LED Open and

Short Detection

– Cable On/Off Detection

• Supplies:

– Rx = 2.0 V to 3.6 V

– Tx = 3.0 V or 5.25 V

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2SPI is a trademark of Motorola.

3All other trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (84 pages)

PAGE 1
AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 Integrated Analog Front-End for Pulse Oximeters Check for Samples: AFE4490 FEATURES 1 • • Package: Compact QFN-40 (6 mm × 6 mm) Specified Temperature Range: –40°C to +85°C APPLICATIONS • • Medical Pulse Oximeter Applications Industrial Photometry Applications DESCRIPTION The AFE4490 is a fully-integrated analog front-end (AFE) that is ideally suited for pulse-oximeter applications.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 RECOMMENDED OPERATING CONDITIONS Over operating free-air temperature range, unless otherwise noted. PARAMETER VALUE UNIT SUPPLIES RX_ANA_SUP AFE analog supply 2.0 to 3.6 V RX_DIG_SUP AFE digital supply 2.0 to 3.6 V TX_CTRL_SUP Transmit controller supply 3.0 to 5.25 LED_DRV_SUP Transmit LED driver supply H-bridge or common anode configuration Difference between LED_DRV_SUP and TX_CTRL_SUP V (1) (2) (3) [3.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com ELECTRICAL CHARACTERISTICS Minimum and maximum specifications are at TA = –40°C to +85°C. Typical specifications are at +25°C. All specifications are at RX_ANA_SUP = RX_DIG_SUP = 3 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, stage 2 amplifier disabled, and fCLK = 8 MHz, unless otherwise noted.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 ELECTRICAL CHARACTERISTICS (continued) Minimum and maximum specifications are at TA = –40°C to +85°C. Typical specifications are at +25°C. All specifications are at RX_ANA_SUP = RX_DIG_SUP = 3 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, stage 2 amplifier disabled, and fCLK = 8 MHz, unless otherwise noted.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com ELECTRICAL CHARACTERISTICS (continued) Minimum and maximum specifications are at TA = –40°C to +85°C. Typical specifications are at +25°C. All specifications are at RX_ANA_SUP = RX_DIG_SUP = 3 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, stage 2 amplifier disabled, and fCLK = 8 MHz, unless otherwise noted. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT DIAGNOSTICS EN_SLOW_DIAG = 0 Start of diagnostics after the DIAG_EN register bit is set.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 ELECTRICAL CHARACTERISTICS (continued) Minimum and maximum specifications are at TA = –40°C to +85°C. Typical specifications are at +25°C. All specifications are at RX_ANA_SUP = RX_DIG_SUP = 3 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, stage 2 amplifier disabled, and fCLK = 8 MHz, unless otherwise noted. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT SUPPLY CURRENT Receiver analog supply current RX_ANA_SUP = 3.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com ELECTRICAL CHARACTERISTICS (continued) Minimum and maximum specifications are at TA = –40°C to +85°C. Typical specifications are at +25°C. All specifications are at RX_ANA_SUP = RX_DIG_SUP = 3 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, stage 2 amplifier disabled, and fCLK = 8 MHz, unless otherwise noted. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT POWER DISSIPATION PD(q) 2.84 mW 0.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 PARAMETRIC MEASUREMENT INFORMATION SERIAL INTERFACE TIMING tCLK XIN tSTECLK SPI STE tSPICLK tCLKSTEH 31 SCLK 7 23 0 tCLKSTEL tSIMOHD tSIMOSU SPI SIMO A7 A6 A1 A0 tSOMIHD tSOMIPD tSOMIPD D23 SPI SOMI D22 D17 D16 D7 D6 D1 D0 }v[ , can be high or low. (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].
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com PARAMETRIC MEASUREMENT INFORMATION (continued) tSTECLK SPI STE 31 SCLK 23 0 tSIMOHD tSIMOSU A7 SPI SIMO A6 A1 A0 D23 D22 D1 D0 Figure 2. Serial Interface Timing Diagram, Write Operation Table 1. Timing Requirements for Figure 1 and Figure 2 PARAMETER tCLK Clock frequency on XIN pin tSCLK Serial shift clock period tSTECLK tCLKSTEH,L MIN TYP 8 MAX UNIT MHz 62.
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AFE4490 www.ti.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com PIN DESCRIPTIONS (continued) NAME 12 NO. FUNCTION DESCRIPTION PD_ALM/ADC Reset 23 Digital Output signal that indicates a PD sensor or cable fault. Can be connected to the port pin of an external microcontroller. In ADC bypass mode, the PD_ALM pin can be used to bring out the ADC reset signal. RESET 29 Digital AFE-only reset input, active low. Can be connected to the port pin of an external microcontroller.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 TYPICAL CHARACTERISTICS 800 800 700 700 600 600 RX Current ( A) RX Current ( A) At TA = +25°C, RX_ANA_SUP = RX_DIG_SUP = 3.0 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, and fCLK = 8 MHz, unless otherwise noted. 500 RX_ANA_SUP_CURR ( A) 400 RX_DIG_SUP_CURR ( A) RX_ANA_CURR_STG2EN ( A) 300 500 RX_ANA_SUP_CURR ( A) 400 RX_DIG_SUP_CURR ( A) RX_ANA_CURR_STG2EN ( A) 300 200 200 RX_ANA_SUP = RX_DIG_SUP = 2.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RX_ANA_SUP = RX_DIG_SUP = 3.0 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, and fCLK = 8 MHz, unless otherwise noted. 800 Duty Cycle = 1% Duty Cycle = 5% Duty Cycle = 10% Duty Cycle = 15% Duty Cycle = 20% Duty Cycle = 25% 600 500 400 300 200 For each setting RF adjusted for Full-Scale Output. Amb Cancellation & stage 2 Gain = 4 used for Low Pleth currents (0.125uA, 0.25uA & 0.5uA.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RX_ANA_SUP = RX_DIG_SUP = 3.0 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, and fCLK = 8 MHz, unless otherwise noted. 1200 Duty Cycle 1% Duty Cycle 5% Duty Cycle 10% Duty Cycle 15% Duty Cycle 20% Duty Cycle 25% 800 700 600 500 400 300 200 For each setting RF adjusted for Full-Scale Output. Amb Cancellation & stage 2 Gain = 4 used for Low Pleth currents (0.125uA, 0.25uA & 0.5uA.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RX_ANA_SUP = RX_DIG_SUP = 3.0 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, and fCLK = 8 MHz, unless otherwise noted. 16 For each setting RF adjusted for Full-Scale Output. Amb Cancellation & stage 2 Gain = 4 used for Low Pleth currents (0.125uA, 0.25uA & 0.5uA). RMS noise is calculated in 5Hz B/W & NFB is calculated using 6.6 u RMS noise.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RX_ANA_SUP = RX_DIG_SUP = 3.0 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, and fCLK = 8 MHz, unless otherwise noted. 16 For each setting RF adjusted for Full-Scale Output. Amb Cancellation & stage 2 Gain = 4 used for Low Pleth currents (0.125uA, 0.25uA & 0.5uA). RMS noise is calculated in 20Hz B/W & NFB is calculated using 6.6 u RMS noise.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com TYPICAL CHARACTERISTICS (continued) 500 500 400 400 300 300 DAC Step Error ( A) DAC Step Error ( A) At TA = +25°C, RX_ANA_SUP = RX_DIG_SUP = 3.0 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, and fCLK = 8 MHz, unless otherwise noted. 200 100 0 ±100 ±200 ±300 100 0 ±100 ±200 ±300 ±400 ±400 TX_REF = 0.5V ±500 TX_REF = 0.5V ±500 0 50 100 150 200 0 250 TX LED DAC Setting 150 200 250 TX LED DAC Setting C032 Figure 34.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RX_ANA_SUP = RX_DIG_SUP = 3.0 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, and fCLK = 8 MHz, unless otherwise noted. 100 100 Expected + 1% Expected + 1% Actual DAC Current Actual DAC Current 80 Expected - 1% TX Current (mA) TX Current (mA) 80 60 40 20 60 40 20 TX Reference Voltage = 0.5V 0 0 50 100 150 200 0 50 100 150 200 250 TX LED DAC Setting C037 Figure 39.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RX_ANA_SUP = RX_DIG_SUP = 3.0 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, and fCLK = 8 MHz, unless otherwise noted. 1200 Number of Occurences 1000 165 163 161 159 157 151 149 0 147 0 145 200 143 200 141 400 139 400 600 137 600 800 135 800 63.0 63.5 64.0 64.5 65.0 65.5 66.0 66.5 67.0 67.5 68.0 68.5 69.0 69.5 70.0 70.5 71.0 71.5 72.0 72.5 73.0 73.5 74.0 74.5 75.0 75.5 76.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RX_ANA_SUP = RX_DIG_SUP = 3.0 V, TX_CTRL_SUP = LED_DRV_SUP = 5 V, and fCLK = 8 MHz, unless otherwise noted.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com OVERVIEW BG DNC DNC RX_DIG_SUP RX_ANA_SUP RX_ANA_SUP TX_CTRL_SUP LED_DRV_SUP LED_DRV_SUP 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.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 RECEIVER CHANNEL This section describes the receiver channel functionality. Receiver Front-End The receiver consists of a differential current-to-voltage (I-V) transimpedance amplifier that converts the input photodiode current into an appropriate voltage, as shown in Figure 54. The feedback resistor of the amplifier (RF) is programmable to support a wide range of photodiode currents.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com The sampling duration is termed the Rx sample time and is programmable for each signal, independently. Sampling can start after the I-V amplifier output is stable (to account for LED and cable settling times). The Rx sample time is used for all dynamic range calculations; the minimum time supported is 50 µs. A single, 22-bit ADC converts the sampled LED2, LED1, and ambient signals sequentially.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 Using the set value, the ambient cancellation stage subtracts the ambient component and gains up only the pleth component of the received signal, as shown in Figure 56. The amplifier gain is programmable to 0 dB, 3.5 dB, 6 dB, 9.5 dB, and 12 dB. ICANCEL Cf Rg Rf IPLETH + IAMB Ri Rx VDIFF Ri Rf Rg ICANCEL Cf Value of ICANCEL set using the SPI interface. Figure 56.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com RG values with various gain settings are listed in Table 2. Table 2. RG Values RG (dB) GAIN (kΩ) 0 (x1) 100 3.5 (x1.5) 150 6 (x2) 200 9.5 (x3) 300 12 (x4) 400 Receiver Control Signals LED2 sample phase (SLED2): When this signal is high, the amplifier output corresponds to the LED2 on-time. The amplifier output is filtered and sampled into capacitor CLED2.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 RED LED On Signal tLED LED On-Time d 0.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com CLOCKING AND TIMING SIGNAL GENERATION The crystal oscillator generates a master clock signal using an external 8-MHz crystal. A divide-by-2 block converts the 8-MHz clock to 4 MHz, which is used by the AFE to operate the timer modules, ADC, and diagnostics. The 4-MHz clock is buffered and output from the AFE in order to clock an external microcontroller. The clocking functionality is shown in Figure 58.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 LED2(Red LED) ON signal tLED LED On-Time d 0.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com For the 11 signals in Figure 57, the start and stop edge positions are programmable with respect to the PRF period. Each signal uses a separate timer compare module that compares the counter value with preprogrammed reference values for the start and stop edges. All reference values can be set using the SPI interface. When the counter value equals the start reference value, the output signal is set.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 Using the Timer Module The timer module registers can be used to program the start and end instants in units of 4-MHz clock cycles. These timing instants and the corresponding registers are listed in Table 3. Note that the device does not restrict the values in these registers; thus, the start and end edges can be positioned anywhere within the pulse repetition period.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 CONVLED2, Convert LED2 (RED) Sample t14 t13 CONVLED2_amb, Convert Ambient Sample LED2 (RED) Phase t16 t15 CONVLED1, Convert LED1 (IR) Sample t18 t17 CONVLED1_amb, Convert Ambient Sample LED1 (IR) Phase t20 t19 ADC Conversion Two 4-MHz Clock Cycles t21 t23 t22 ADC Reset t0 t25 t24 t27 t28 t26 Pulse Repetition Period (PRP), One Cycle t29 (1) RED = LED2, IR = LED1. Figure 63.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com ADC OPERATION AND AVERAGING MODULE The ADC reset signal must be positioned at 25% intervals of the pulse repetition period (that is, 0%, 25%, 50%, and 75%). After the falling edge of the ADC reset signal, the ADC conversion phase starts (refer to Figure 63). Each ADC conversion takes 50 µs. There are two modes of operation: without averaging and with averaging.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 The number of samples to be used per conversion phase is specified in the CONTROL1 register (NUMAV[7:0]). The user must specify the correct value for the number of averages, as described in Equation 3: 0.25 ´ Pulse Repetition Period NUMAV[7:0] + 1 = -1 50 ms (3) When the number of averages is '0', the averaging is disabled and only one ADC sample is written to the result registers.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com ADC Conversion ADC Data 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ADC Reset 25% 0% Average of ADC data 1 to 3 are written into register 42. Average of ADC data 5 to 7 are written into register 43. 0% 75% 50% Average of ADC data 9 to 11 are written into register 44. Average of ADC data 13 to 15 are written into register 45. Register 42 register 43 are written into register 46.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 AFE ANALOG OUTPUT MODE (ADC Bypass Mode) This mode is only intended for use in system debug. Note that this function is not recommended for production use because of the minimal device production testing performed on this function. The ADC bypass mode brings out the analog output voltage of the receiver front-end on two pins (RXOUTP, RXOUTN), around a common-mode voltage of approximately 0.9 V.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com LED2 (RED LED) On Signal t3 LED1 (IR LED) On Signal SLED2_amb, Sample Ambient LED2 (RED) Phase t9 t4 t10 t6 t5 SLED1, Sample LED1 (IR) t7 t8 SLED1_amb, Sample Ambient LED1 (IR) Phase t11 t12 SLED2, Sample LED2 (RED) t1 ADC Reset (Pin 23) t22 t27 t25 t23 t21 t24 t2 t28 t26 ADC_RDY (Pin 28) t0 Pulse Repetition Period (PRP), One Cycle t29 NOTE: RED = LED2, IR = LED1. Figure 69.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 In ADC bypass mode, the ADC reset signal can be used to start conversions with the external ADC. Use registers 15h through 1Ch to position the ADC reset signal edges appropriately. Also, use the CLKALMPIN[2:0] bits on the PD_ALM pin register bit to bring out the ADC reset signal to the PD_ALM pin. ADC_RDY can be used to indicate the start of the pulse repetition period to the external ADC.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com TRANSMIT SECTION The transmit section integrates the LED driver and the LED current control section with 8-bit resolution. This integration is designed to meet a dynamic range of better than 105 dB (based on a 1-sigma LED current noise). The RED and IR LED reference currents can be independently set. The current source (ILED) locally regulates and ensures that the actual LED current tracks the specified reference.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 LED_DRV_SUP TX_CTRL_SUP External Supply Tx CBULK H-Bridge LED2_ON H-Bridge Driver LED1_ON LED2_ON or LED1_ON LED2 Current Reference ILED LED Current Control 8-Bit Resolution LED1 Current Reference Register LED2 Current Reference Register LED1 Current Reference Figure 71.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com TX_CTRL_SUP External Supply LED_DRV_SUP CBULK Tx LED2_ON H-Bridge Driver LED1_ON LED2_ON or LED1_ON LED2 Current Reference ILED LED Current Control 8-Bit Resolution LED1 Current Reference Register RED Current Reference Register IR Current Reference Figure 72.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 Transmitter Power Path The block diagram in Figure 73 shows the AFE4490 Tx subsystem power routing. TX_CTRL_SUP Tx Reference and Control LED Current Control DAC Tx LED Bridge LED_DRV_SUP Device Figure 73. Transmit Subsystem Power Routing LED Power Reduction During Periods of Inactivity The diagram in Figure 74 shows how LED bias current passes 50 µA whenever LED_ON occurs.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com DIAGNOSTICS The device includes diagnostics to detect open or short conditions of the LED and photosensor, LED current profile feedback, and cable on or off detection. Photodiode-Side Fault Detection Figure 75 shows the diagnostic for the photodiode-side fault detection. Internal TX_CTRL_SUP 10 k 10 k 1k Cable Rx On/Off INM To Rx Front-End INP Rx On/Off LED Wires 100 PA PD Wires 100 PA GND Wires Legend for Cable Figure 75.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 Transmitter-Side Fault Detection Figure 76 shows the diagnostic for the transmitter-side fault detection. Internal TX_CTRL_SUP SW1 Cable SW3 10 k 10 k TXP D C SW2 SW4 TXN PD Wires LED Wires 100 PA 100 PA GND Wires LED DAC Legend for Cable Figure 76.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com Diagnostics Module The diagnostics module, when enabled, checks for nine types of faults sequentially. The results of all faults are latched in 11 separate flags. At the end of the sequence, the state of the 11 flags are combined to generate two interrupt signals: PD_ALM for photodiode-related faults and LED_ALM for transmit-related faults. The status of all flags can also be read using the SPI interface.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 After completion of the diagnostics function, time must be allowed for the AFE4490 filter to settle. See the Electrical Characteristics for the filter settling time. The slow diagnostics feature is provided for use in systems where high-capacitance sensors (such as photodiodes, capacitors, cables, and so forth) are connected to the INP, INN, TXP, or TXN pins.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com Reading Data The SPI_READ register bit must be first set to '1' before reading from a register. The AFE4490 includes a mode where the contents of the internal registers can be read back on the SPISOMI pin. This mode may be useful as a diagnostic check to verify the serial interface communication between the external controller and the AFE.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 Multiple Data Reads and Writes The device includes functionality where multiple read and write operations can be performed during a single SPISTE event. To enable this functionality, the first eight bits determine the register address to be written and the remaining 24 bits determine the register data.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com Register Initialization After power-up, the internal registers must be initialized to the default values. This initialization can be done in one of two ways: • Through a hardware reset by applying a low-going pulse on the RESET pin, or • By applying a software reset. Using the serial interface, set SW_RESET (bit D3 in register 00h) high. This setting initializes the internal registers to the default values and then self-resets to '0'.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 Table 5.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com Table 5.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 AFE REGISTER DESCRIPTION CONTROL0: Control Register 0 (Address = 00h, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 D15 D14 D13 D12 0 0 0 0 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 0 0 0 0 0 TIM_ COUNT_ RST SPI_ READ SW_RST DIAG_EN This register is write-only. CONTROL0 is used for AFE software and count timer reset, diagnostics enable, and SPI read functions.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com LED2ENDC: Sample LED2 End Count Register (Address = 02h, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D15 D14 D13 D12 LED2ENDC[15:0] D3 D2 D1 D0 LED2ENDC[15:0] This register sets the end timing value for the LED2 signal sample.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 ALED2STC: Sample Ambient LED2 Start Count Register (Address = 05h, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D15 D14 D13 D12 ALED2STC[15:0] D3 D2 D1 D0 ALED2STC[15:0] This register sets the start timing value for the ambient LED2 signal sample.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com LED1ENDC: Sample LED1 End Count (Address = 08h, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D15 D14 D13 D12 LED1ENDC[15:0] D3 D2 D1 D0 LED1ENDC[15:0] This register sets the end timing value for the LED1 signal sample.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 ALED1STC: Sample Ambient LED1 Start Count Register (Address = 0Bh, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D15 D14 D13 D12 ALED1STC[15:0] D3 D2 D1 D0 ALED1STC[15:0] This register sets the start timing value for the ambient LED1 signal sample.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com LED2CONVEND: LED2 Convert End Count Register (Address = 0Eh, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D15 D14 D13 D12 LED2CONVEND[15:0] D3 D2 D1 D0 LED2CONVEND[15:0] This register sets the end timing value for the LED2 conversion.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 LED1CONVST: LED1 Convert Start Count Register (Address = 11h, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D15 D14 D13 D12 LED1CONVST[15:0] D3 D2 D1 D0 LED1CONVST[15:0] This register sets the start timing value for the LED1 conversion.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com ALED1CONVEND: LED1 Ambient Convert End Count Register (Address = 14h, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D15 D14 D13 D12 ALED1CONVEND[15:0] D3 D2 D1 D0 ALED1CONVEND[15:0] This register sets the end timing value for the ambient LED1 conversion.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 ADCRSTSTCT1: ADC Reset 1 Start Count Register (Address = 17h, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D15 D14 D13 D12 ADCRSTSTCT1[15:0] D3 D2 D1 D0 ADCRSTSTCT1[15:0] This register sets the start position of the ADC1 reset conversion signal.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com ADCRSTENDCT2: ADC Reset 2 End Count Register (Address = 1Ah, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D15 D14 D13 D12 ADCRSTENDCT2[15:0] D3 D2 D1 D0 ADCRSTENDCT2[15:0] This register sets the end position of the ADC2 reset conversion signal.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 PRPCOUNT: Pulse Repetition Period Count Register (Address = 1Dh, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D15 D14 D13 D12 PRPCOUNT[15:0] D3 D2 D1 D0 PRPCOUNT[15:0] This register sets the device pulse repetition period count.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com SPARE1: SPARE1 Register For Future Use (Address = 1Fh, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 D15 D14 D13 D12 0 0 0 0 0 0 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 0 0 0 0 0 0 0 0 0 This register is a spare register and is reserved for future use.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com LEDCNTRL: LED Control Register (Address = 22h, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 0 0 0 0 0 0 D11 D10 D9 D8 D7 D6 D17 D16 D15 LED_RANGE[1:0] D5 LED1[7:0] D14 D13 D12 LED1[7:0] D4 D3 D2 D1 D0 LED2[7:0] This register sets the LED current range and the LED1 and LED2 drive current.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 Bit D2 www.ti.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 RESERVED1: RESERVED1 Register For Factory Use Only (Address = 27h, Reset Value = XXXXh) D23 D22 D21 D20 D19 D18 D17 D16 D15 D14 D13 D12 X X X X X X X X X X X X D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X X X X X X X X X X A. X = don't care. This register is reserved for factory use. Readback values vary between devices.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com LED2VAL: LED2 Digital Sample Value Register (Address = 2Ah, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 D15 D14 D13 D12 D4 D3 D2 D1 D0 LED2VAL[23:0] D11 D10 D9 D8 D7 D6 D5 LED2VAL[23:0] This register contains the digital value of the latest LED2 sample converted by the ADC. The ADC_RDY signal goes high each time that the contents of this register are updated.
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 ALED1VAL: Ambient LED1 Digital Sample Value Register (Address = 2Dh, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 D15 D14 D13 D12 D4 D3 D2 D1 D0 ALED1VAL[23:0] D11 D10 D9 D8 D7 D6 D5 ALED1VAL[23:0] This register contains the digital value of the latest LED1 ambient sample converted by the ADC. The ADC_RDY signal goes high each time that the contents of this register are updated.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com DIAG: Diagnostics Flag Register (Address = 30h, Reset Value = 0000h) D23 D22 D21 D20 D19 D18 D17 D16 D15 D14 D13 D12 0 0 0 0 0 0 0 0 0 0 0 PD_ALM D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 LED_ ALM LED1 OPEN LED2 OPEN LEDSC OUTPSH GND OUTNSH GND PDOC PDSC INNSC GND INPSC GND INNSC LED INPSC LED This register is read only.
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AFE4490 www.ti.com Bit D3 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 INNSCGND: INN to GND diagnostic flag This bit indicates a short from the INN pin to the GND cable. 0 = No fault (default after reset) 1 = Fault present Bit D2 INPSCGND: INP to GND diagnostic flag This bit indicates a short from the INP pin to the GND cable. 0 = No fault (default after reset) 1 = Fault present Bit D1 INNSCLED: INN to LED diagnostic flag This bit indicates a short from the INN pin to the LED cable.
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com REVISION HISTORY NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision E (October 2013) to Revision F Page • Changed LED_DRV_SUP parameter in Recommended Operating Conditions table .......................................................... 3 • Changed VLED footnote and added VHR footnote to Recommended Operating Conditions table .........................................
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AFE4490 www.ti.com SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 • Added last paragraph to the Diagnostics Module section .................................................................................................. 47 • Added first and last sentence to Writing Data section ........................................................................................................ 47 • Changed second to last sentence in Writing Data section .........................................................
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AFE4490 SBAS602F – DECEMBER 2012 – REVISED OCTOBER 2013 www.ti.com • Added Timing, Wake-up time from Rx power-down and Wake-up time from Tx power-down parameters to Electrical Characteristics table ............................................................................................................................................................. 6 • Changed Supply Current section of Electrical Characteristics table ................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 5-Nov-2013 In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant AFE4490RHAR VQFN RHA 40 2500 330.0 16.4 6.3 6.3 1.5 12.0 16.0 Q2 AFE4490RHAT VQFN RHA 40 250 180.0 16.4 6.3 6.3 1.5 12.0 16.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) AFE4490RHAR VQFN RHA 40 2500 367.0 367.0 38.0 AFE4490RHAT VQFN RHA 40 250 210.0 185.0 35.
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