ICU-20201
Long-Range Ultrasonic Time-of-Flight Range Sensor
ICU-20201 HIGHLIGHTSAPPLICATIONSICU-20201 is a miniature, ultra-low power, long-range
ultrasonic Time-of-Flight (ToF) transceiver. Based on Chirp’s
patented MEMS technology, the ICU-20201 is a system-inpackage that integrates a nominally 85kHz PMUT
(Piezoelectric Micromachined Ultrasonic Transducer) together
with a 2nd generation ultra-low power SoC (System on Chip) ina miniature, reflowable package.
The SoC is designed for overall low system power and for easeof use with external host processors. Low power is achieved
through custom digital circuitry to process and buffer the raw
sensor readings. This keeps the integrated microcontroller in alow power idle state until needed. For ease of use, themicrocontroller can process the raw sensor readings into highlevel signals, such as range to nearby target(s), or events, suchas presence, which can be directly read by the host processor.
The SoC communicates with the host processor over SPI at up
to 13MHz.
Complementing Chirp’s other ultrasonic ToF sensor products,
ICU-20201 provides accurate range measurements to targets
at distances up to 5m. Based on ultrasonic pulse-echomeasurements, the sensor works in any lighting condition,
including full sunlight, and provides millimeter-accurate range
measurements independent of the target’s color and opticaltransparency. The sensor’s Field-Of-View (FOV) can becustomized and enables simultaneous range measurements tomultiple objects in the FOV. Several available algorithms canfurther process the echo information for a variety of usage
cases in a range of applications (listed below).

DEVICE INFORMATIONPART NUMBER

PACKAGE

LID OPENING

ICU-20201

3.5 x 3.5 x 1.26 mm
LGA

1-HoleRoHS and Green-Compliant Package

This document contains information on a preproduction
product. Specifications and information herein are
subject to change without notice.

•
•
•
•
•

Low power user presence in consumer electronics
Parking lot sensors for vehicle counting
Smart door lock wake-on-approach
Obstacle avoidance and wall following
Ground level measurement in drones

FEATURES•

Fast, accurate range-finding• 40MHz integrated CPU enables on-chip
algorithms including rangefinding, humanpresence, and wake-on approach• Operating range from 20 cm to 5m• Detection of moving objects closer than 20cm
• Programmable modes optimized for long or
short-range sensing applications• Customizable field of view (FoV) up to 180°
• Multi-object detection• Works in any lighting condition, including fullsunlight to complete darkness• Insensitive to object color, detects opticallytransparent surfaces (glass, clear plastics etc.)• Easy to integrate• Single sound port for receive and transmit• Flexible 1.71V to 3.63V I/O voltage• Low power 1.8V core operating voltage• 13MHz SPI interface allows baseband data
stream out at full measurement rate
• Optional 32kHz reference clock input• Two programmable open drain I/O for
triggering the sensor or waking the host
• Platform-independent software driver enables
turnkey range-finding• Miniature integrated package• 3.5 mm x 3.5mm x 1.26mm, 14-pin LGA• Compatible with standard SMD reflow• Operating temperature range: -40°C to 85°C
• Low supply current• 1 sample/s:o 18 µA (1 m max range)o 26 µA (5 m max range)• 25 samples/s:
o 130 µA (1 m max range)o 300 µA (5 m max range)

InvenSense, a TDK Group Company
1745 Technology Drive, San Jose, CA 95110 U.S.A+1(408) 988–7339
invensense.tdk.com

Document Number: DS-000478
Revision: 1.5
Release Date: 03/15/2023

ICU-20201
TABLE OF CONTENTS
ICU-20201 Highlights ........................................................................................................................................................ 1
Device Information ........................................................................................................................................................... 1
Applications ..................................................................................................................................................................... 1
Features ........................................................................................................................................................................... 1
Table of Contents ............................................................................................................................................................. 2
1

Simplified Block Diagram & Pin OUT ............................................................................................................................ 4
1.1

2

3

Electrical Characteristics .............................................................................................................................................. 5
2.1

Absolute Maximum Ratings................................................................................................................................... 5

2.2

Ultrasonic Transceiver Characteristics ................................................................................................................... 6

2.3

I/O Characteristics................................................................................................................................................. 7

2.4

SPI TIming characteristics – 4-wire spi mode ......................................................................................................... 7

2.5

SPI TIming characteristics – 3-wire spi mode ......................................................................................................... 8

Detailed Description .................................................................................................................................................... 9
3.1

5

Theory of Operation.............................................................................................................................................. 9

3.1.1

Ultrasonic Transducer ......................................................................................................................................................... 9

3.1.2

Measurement process......................................................................................................................................................... 9

3.1.3

I/Q Baseband data............................................................................................................................................................ 10

3.1.4

Rangefinding .................................................................................................................................................................... 10

3.1.5

Low power systems........................................................................................................................................................... 11

3.1.6

Clock Calibration............................................................................................................................................................... 11

3.2
4

Pin Descriptions .................................................................................................................................................... 4

Device Configuration ........................................................................................................................................... 11

Applications ............................................................................................................................................................... 12
4.1

Typical Operating Characteristics ........................................................................................................................ 12

4.2

Soniclib Driver ..................................................................................................................................................... 12

4.3

Object Detection ................................................................................................................................................. 12

4.4

Device Modes of Operation................................................................................................................................. 12

4.4.1

Free-Running Mode .......................................................................................................................................................... 12

4.4.2

Hardware-Triggered Mode................................................................................................................................................ 13

4.4.3

Software-Triggered Mode ................................................................................................................................................. 13

4.5

Coexistence Near other ICU-20201 ...................................................................................................................... 14

4.6

PCB Reflow Recommendations:........................................................................................................................... 14

4.7

Typical Operating Circuits.................................................................................................................................... 15

4.8

Recommended PCBA Layout ............................................................................................................................... 16

Package Information .................................................................................................................................................. 17
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ICU-20201

65.1

Pin Configuration ................................................................................................................................................ 17

5.2

Package Dimensions............................................................................................................................................ 17

Ordering Information ................................................................................................................................................. 18
6.1

Part Number Designation .................................................................................................................................... 18

6.2

Package Marking ................................................................................................................................................. 18

6.3

Tape & Reel Specification .................................................................................................................................... 18

6.4

Shipping Label ..................................................................................................................................................... 19

7

SmartSonic™ Family................................................................................................................................................... 20

8

Revision History ......................................................................................................................................................... 21

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ICU-20201
1 SIMPLIFIED BLOCK DIAGRAM & PIN OUT

Figure 1. Simplified Block Diagram

1.1 PIN DESCRIPTIONS
PIN

NAME

DESCRIPTION

1

GND

Ground2

SCLK

SPI Interface Clock (from external SPI host) CPOL=1, CPHA=1

3

MOSI

MCU Out Sensor In serial data (from external SPI host)

4

MISO

MCU In Sensor Out serial data (to external SPI host)

5

CS_B

SPI Chip Select (active-low, from external SPI host)

6

INT1

Interrupt Request Open Drain Input/Output 1

7

INT2

Interrupt Request Open Drain Input/Output 2

8

GND

9

LFCLK

GroundExternal Input/Output Low Frequency Reference Clock - 32.768kHz typical(optional)

10

MUTCLK

External Input/Output 16x Operating Frequency Reference Clock (optional)

11

GND

12

VDD

GroundDigital Logic Supply. Suggest common connection to AVDD. If not connected
locally to AVDD, bypass with a 0.1μF capacitor close to VDD & GND pad.

13

AVDD

Analog Power Supply. Bypass with a 0.1μF capacitor close to AVDD & GND pad.

14

VDDIO

I/O Power Supply. Bypass with a 1.0μF capacitor close to VDDIO & GND pad.
Table 1. Pin Descriptions

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2 ELECTRICAL CHARACTERISTICS
2.1 ABSOLUTE MAXIMUM RATINGS
MAX.

UNIT

AVDD/VDD to GND

PARAMETER

MIN.
-0.3

2.2

V

VDDIO to GND

-0.3

4.0

V

Digital I/O pins to GND-0.3

Digital I/O pins to VDDIO

TYP.

V
0.3

V

Electrostatic Discharge (ESD)
Human Body Model (HBM)(1)

-2

2

kV

Charge Device Model (CDM)(2)

-500

500

V

Latchup

-100

100

mA

Temperature, Operating

-40

85

°C

90

%RH

20

mA

260

°C

Relative Humidity, Storage
Continuous Input Current (Any Pin)

-20

Soldering Temperature (reflow)
1.
2.

HBM Tests conducted in compliance with ANSI/ESDA/JEDEC JS-001-2024 Or JESD22-A114E
CDM Tests conducted in compliance with JESD22-C101.

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ICU-20201
2.2 ULTRASONIC TRANSCEIVER CHARACTERISTICS(AVDD = VDD = 1.8VDC, VDDIO=3.3V, GND = 0V, TA = +25°C, min/max are from TA = -40°C to +85°C, unless otherwise specified.)
PARAMETER
POWER SUPPLY
Analog Power Supply
Digital Power Supply
IO Power Supply
Operating Temperature

SYMBOL

CONDITIONS

AVDD
VDD
VDDIO

ULTRASONIC TRANSMIT CHANNEL
Operating Frequency
fop

MIN

TYP

MAX

UNITS

1.71
1.71
1.71
-40

1.8
1.8
25

1.89
1.89
3.63
85

V
V
V
°C

70(1)

85

95(1)

kHz

TxRx OPERATION(2)Maximum Range

Max Range

Minimum Range

Min Range

Baseband I/Q Output Sample
Rate

Measuring Rate (Sample/sec)MR

Field of View

FoV

Current Consumption (AVDD +VDD) (5)IS

Idle Current (AVDD+VDD)

Ii

Measurement Latency(6)5(3)
2.7(3)

Wall Target
58mm Diameter Postmmm

0.2(4)
Output Data Rate
ODR=2
ODR=3
ODR=4
ODR=5
ODR=6
5m max range
1m max range
MR=1Meas/s, Range=1m
MR=1Meas/s, Range=5m
MR=25Meas/s, Range=1m
MR=25Meas/s, Range=5m
T=+25°C, VDD=AVDD=1.8V
Sensor Idle, FW programmed.
1m max range
5m max range

Programming Time

fop/32
fop/16
fop/8
fop/4
fop/2

Samples/s

32
150
Configurable up to 180°
18
26
132
296

Measurements/s
Measurements/s
deg
μA
μA
μA
μA

9

μA

6.5
30
5(7)

18

ms
ms
ms

Notes:
1.
2.
3.
4.
5.
6.
7.

100% tested; some shift is normal after SMT
General Purpose Transceiver Firmware loaded; ODR=4 unless otherwise noted
By characterization, tested using 45° FoV conical horn with a particle ingress filter (PIF). The type of horn & PIF used can influence the maximum
range.
By characterization, tested with a stationary target. While objects closer than 20 cm can be detected, the range measurement is not ensured.
ODR = 4
By characterization, from start of measurement to data ready signal on INT line
By characterization, tested with SCLK frequency of 12.5MHz

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ICU-20201
2.3 I/O CHARACTERISTICS(AVDD = VDD = 1.8VDC, VDDIO=3.3V, GND = 0V, TA = +25°C, min/max are from TA = -40°C to +85°C, unless otherwise specified.)
PARAMETERSYMBOL
CONDITIONSDIGITAL INPUTS (MOSI, CS_B, SCLK, MUTCLK, LFCLK, INT1, INT2)
VIH, High Level Input Voltage
VIH
VIL, Low Level Input Voltage
VIL

MIN

TYP

MAX

0.7*VVDDIO

UNITS
V
V

0.3*VVDDIO
Input CapacitanceCI
DIGITAL OUTPUT (MISO, MUTCLK, LFCLK, INT1, INT2)High Level Output Voltage
VOH
RLOAD=1 MΩ
Low Level Output Voltage
VOL
RLOAD=1 MΩ

<10

pF

0.9*VVDDIO

V
V

0.1*VVDDIO
Output Leakage Current

OPEN=1±100

nA

2.4 SPI TIMING CHARACTERISTICS – 4-WIRE SPI MODE
(AVDD = VDD = 1.8VDC, VDDIO=1.8V or 3.3V, GND = 0V, TA = +25°C, min/max are from TA = -40°C to +85°C,
unless otherwise specified.)
PARAMETER
DIGITAL I/O CHARACTERISTICSSYMBOLSCLK Clock Frequency
SCLK Low Period
SCLK High Period
CS_B Setup Time
CS_B Hold TimeMOSI Setup TimeMOSI Hold TimeMISO Valid TimeMISO Hold TimeMISO Output Disable Time

fCLK
tLOW
tHIGH
tSU.CSB
tHD.CSB
tSU.MOSI
tHD.MOSI
tVD.MISO
tHD.MISO
tDIS.MISOCONDITIONS

MIN

TYP

MAX

UNITS

13

MHz
ns
ns
ns
ns
ns
ns
ns
ns
ns

11
11

80
80
2

2
Cload = 20pF
Cload = 20pF

28

2
3

Note: Based on characterization of 10 parts from 3 typical and 2 corner lots. Measured over temperature and voltage as mounted in sockets.

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ICU-20201
2.5 SPI TIMING CHARACTERISTICS – 3-WIRE SPI MODE
(AVDD = VDD = 1.8VDC, VDDIO=1.8V or 3.3V, GND = 0V, T A = +25°C, min/max are from TA = -40°C to +85°C, unless otherwise
specified.)
PARAMETER
DIGITAL I/O CHARACTERISTICSSYMBOLSCLK Clock Frequency
SCLK Low Period
SCLK High Period
CS_B Setup Time
CS_B Hold Time
SDIO Input Setup Time
SDIO Input Hold Time
SDIO Output Valid Time
SDIO Output Hold Time
SDIO Output Disable Time

fCLK
tLOW
tHIGH
tSU.CSB
tHD.CSB
tSU.SDIO
tHD.SDIO
tVD.SDIO
tHD.SDIO
tDIS.SDIOCONDITIONS

MIN

TYP

MAX

UNITS

13

MHz
ns
ns
ns
ns
ns
ns
ns
ns
ns

11
11

80
80
2
2
Cload = 20pF
Cload = 20pF

21.5

2
3

Note: Based on characterization of 10 parts from 3 typical and 2 corner lots. Measured over temperature and voltage as mounted in sockets.

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ICU-20201
3 DETAILED DESCRIPTION
3.1 THEORY OF OPERATIONThe ICU-20201 is an autonomous, digital output ultrasonic transceiver. The Simplified Block Diagram in Figure 1 shows themain components at the package-level. The package includes a piezoelectric micro-machined ultrasonic transducer (PMUT)
and system-on-chip (SoC). The SoC controls the PMUT to produce pulses of ultrasound at an operational frequency fop thatreflect off targets in the sensor’s Field of View (FoV). The reflections are received by the same PMUT after a short timedelay, amplified by sensitive electronics, digitized, and stored as I/Q baseband data in the on-chip data memory. Software
defined algorithms can process the I/Q data to detect targets using the on-chip microcontroller (MCU), and thesealgorithms can be tuned to detect stationary or moving targets preferentially. I/Q data can also be transferred to a larger
host or application processor (AP) for further processing.

3.1.1 Ultrasonic Transducer
The PMUT within ICU-20201 is positioned directly below the acoustic port on the top of the device. The PMUT can transmit
and receive ultrasound. During the transmitting process, a high voltage pulse train is applied to the PMUT and the PMUT
transmits a sound wave into the air in front of ICU-20201. During the receive process, the sound waves impinging on the
PMUT create a small current which is amplified and digitized and stored in the on-chip memory.
The frequency of the PMUT varies as a function of the MEMS process; TDK’s patented frequency locking algorithm ensuresthat the transmitting and receiving operational frequency fop is tuned to the PMUT frequency and the transmitting andreceiving sensitivities are optimized.
ICU-20201’s acoustic port provides a nearly hemispherical radiation pattern. Most applications require a narrower FoV andso will use a horn to focus the sound. Somewhat unintuitively, wider diameter horns provide narrower FoV beam patterns.
TDK has several horn 3D models readily available for customer design-in.

3.1.2 Measurement process
ICU-20201’s measurement state machine (MSM) is the core of the ultrasonic transceiver measurement process. The MSM,
once triggered by the MCU, fetches specialized instructions from memory and executes those instructions, causing specificactions to be performed by the transceiver. Instructions consist of a command, interrupt configuration, command specificconfiguration, and a length. The supported commands are transmit, receive, count, and end-of-file (EOF). Each command is
executed for the length of the instruction, which is specified in counts of the measurement clock, which operates at 16fop.
Taken together, several instructions form a measurement queue, which defines the measurement to be taken by thetransceiver. The measurement queue can be adapted to address specific requirements posed by an application. Typically,
the penultimate instruction will consist of a receive instruction with the DONE_IEN bit set, and the last instruction will be
EOF. The MCU will then wake up at the conclusion of the measurement and process the I/Q data or forward it to the hostfor processing.
CMD[1:0]

Description

00

Count

01

Transmit

10

Receive11

End of file

Table 2. PMUT Commands
Byte

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

Byte 0X

X

RX_BIAS_EN

RX_RESETDONE_IEN

RDY_IEN

00

Byte 1

X

X

X

X

X

X

X

X

Byte 2

LENGTH[7:0]

Byte 3

LENGTH[15:8]

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ICU-20201
Table 3. Count instruction format

Byte

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

Byte 0X

X

RX_BIAS_EN

RX_RESETDONE_IEN

RDY_IEN

0

1

Byte 1

Phase[3:0]X

Byte 2

LENGTH[7:0]

Byte 3

LENGTH[15:8]

Pulse_Width[2:0]

Table 4. TX instruction format
Byte

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

Byte 001

RX_BIAS_EN=1

RX_RESETDONE_IEN

RDY_IEN

10

Byte 1X

RX_ATTEN[1:0]

RX_GAIN_REDUCTION[4:0]

Byte 2

LENGTH[7:0]

Byte 3

LENGTH[15:8]

Table 5. RX instruction format
Byte

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

Byte 0X

X

X

X

DONE_IEN

RDY_IEN

1

1

Byte 1

X

X

X

X

X

X

X

X

Byte 20xXX

Byte 30xXX

Table 6. EOF instruction format

3.1.3 I/Q Baseband data
The received signal is amplified, digitized, and downconverted (multiplied) to the baseband (dc) by sine and cosine
components of a digital carrier signal at the operational frequency fop. The component of the signal that is in-phase with thecosine demodulator is called in-phase (I) and the component that is in-phase with the sine demodulator is called quadrature(Q). I and Q signals are then filtered and downsampled to a lower sample rate by a digital comb filter.
The I/Q baseband data contains amplitude (calculated by √𝐼2 + 𝑄2 ), representing the envelope of the signal, and phase(atan2(Q, I)), representing the relative contribution of the I and Q parts of the signal. I/Q data contains all the informationnecessary to reconstruct the ultrasonic signal; however, efficient digital signal processing is best done in the complex
baseband. Many algorithms calculate amplitude and discard the phase information, detecting rising edge(s) in theamplitude data which correspond to echoes or pulses from other transceivers. In certain applications, the phase data may
provide additional information (i.e., to refine the range estimate) or provide the primary source of information (e.g., in an
ultrasonic interferometer).
After the comb filter outputs a sample of the I/Q data, the measurement state machine (MSM) writes the I/Q data directly
to the data memory as two signed 16-bit integers. The sample rate of the I/Q data is set by the ODR setting and can be
fop/32, /16, /8, /4, or /2. Generally, lower ODR is used for low-power presence sensing applications; medium ODR is used forrangefinding up to 5m, and higher ODR is used for short range sensing.

3.1.4 Rangefinding
The time it takes the ultrasound pulse to propagate from the PMUT to a target and back is called the time-of-flight (ToF).
The distance to the target is found by calculating the time-of-flight using a rangefinding algorithm, multiplying the time-offlight by the speed of sound, and dividing by two (to account for the round-trip). The speed of sound in air is approximately
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ICU-20201
343 m/s. The speed of sound is not a constant, but it is stable enough (0.2%/OC) to give measurement accuracies within a
few percent error.
The rangefinding algorithm typically looks for a rising edge in the amplitude (envelope) of the I/Q data; as the data issmooth at nearly all sample rates except the lowest ODR, interpolation is typically used to refine the ToF estimate. The
general-purpose transceiver (GPT) firmware outputs an unsigned 16-bit integer to represent time-of-flight; the time1
resolution of the time-of-flight is 8∗2𝑂𝐷𝑅𝑓 or 92ns for ODR=4 and fop=85kHz.
𝑜𝑝

3.1.5 Low power systems
ICU-20201 has several features that enable low power operation of a system. A low-power, on-chip real-time clock (RTC)
sets the sample rate and provides the reference for the time-of-flight measurement. The host processor does not need toprovide any stimulus to the ICU-20201 during normal operation, allowing the host processor to be shut down into its lowest
power mode until the ICU-20201 generates a wake-up interrupt. There are also two general-purpose input/output (INT1
and INT2) pins that can be used as a system wake-up source. The interrupt pins can be configured to wake up the hostwhen a target is detected.

3.1.6 Clock Calibration
ICU-20201 has 3 internal clocks, the LFCLK, the MUTCLK, and the CPUCLK. The LFCLK is nominally 30kHz and can bemeasured using the pulse timer peripheral. Alternatively, a crystal-derived 32.768kHz (or other known frequency) low
frequency clock can be input through the LFCLK pin of ICU-20201. Once the LFCLK frequency is known, it can be used tomeasure the frequency of MUTCLK and CPUCLK using the frequency timer peripheral.
The CPUCLK is nominally 40MHz and can be tuned to increase algorithm runtime consistency between ICU-20201.
The MUTCLK is digitally controlled to 16 times the operating (transmit and receive) frequency fop, and the PMUT is mostsensitive at the PMUT resonant frequency fn, which ranges between 70kHz and 95kHz; therefore, MUTCLK is typically in therange of 1.12MHz to 1.52MHz.
The ICU-20201’s SonicLib C driver includes a method to measure the LFCLK frequency using the pulse timer feature. The
host MCU will configure the pulse timer, pulse the INT1 line low, wait for a known duration (this delay, typically 100ms,
must be generated by a crystal or a trimmed oscillator), and then pulse the INT1 line low again. The LFCLK frequency willthen be known to the driver.
The SonicLib driver also includes methods to measure the CPUCLK and MUTCLK frequencies (relative to the LFCLK
frequency) using the frequency counter feature in ICU-20201.
Ultimately, the time-of-flight and I/Q data read from ICU-20201 is produced from the MUTCLK time base, and the MUTCLK
frequency (and by extension the LFCLK frequency) must be known to have an accurate time-of-flight measurement.

3.2 DEVICE CONFIGURATIONAn ICU-20201 program file must be loaded into the on-chip memory at initial power-on. The program, or firmware, isloaded through the SPI interface by the SonicLib C driver. The GPT firmware enables autonomous range finding operation of
the ICU-20201. It also supports hardware-triggering of the ICU-20201 for applications requiring multiple transceivers. Chip
configuration can also be tailored to the customer’s application using the ICU-20201 EVK. Contact TDK support for more
information.

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ICU-20201
4 APPLICATIONS
4.1 TYPICAL OPERATING CHARACTERISTICS
AVDD = VDD = VDDIO= 1.8VDC, GND = 0V, TA = +25°C, unless otherwise specified.

Figure 2. Typical Beam Pattern – MOD-ICU-20201-00-01 45 deg FoV module(Measured with a 1 m2 flat plate target at a 1m range)

4.2 SONICLIB DRIVER
Chirp provides a compiler- and microcontroller-independent C driver for the ICU-20201 which greatly simplifies integration.
The ICU-20201 driver implements high-level control of one or more ICU-20201s attached to one or more SPI ports on thehost processor. The ICU-20201 driver allows the user to program, configure, trigger, and readout data from the ICU-20201
through use of C function calls without direct interaction with the ICU-20201 SPI registers. The ICU-20201 driver only
requires the customer to implement an I/O layer which communicates with the host processor’s SPI hardware and GPIO
hardware. Chirp highly recommends that all designs use the ICU-20201 driver.

4.3 OBJECT DETECTION
Detecting the presence of objects or people can be optimized via software, by setting the sensor’s full-scale range (FSR),
and via hardware, using an acoustic housing to narrow or widen the sensor’s field-of-view. The former means that the user
may set the maximum distance at which the sensor will detect an object. FSR values refer to the one-way distance to a
detected object.
In practice, the FSR setting controls the amount of time that the sensor spends in the listening (receiving) period during ameasurement cycle. Therefore, the FSR setting affects the time required to complete a measurement. Longer full-scale
range values will require more time for a measurement to complete.
Ultrasonic signal processing using the ICU-20201’s GPT Firmware will detect echoes that bounce off the first target in the
Field-of-View. The size, position, and material composition of the target will affect the maximum range at which the sensor
can detect the target. Large targets, such as walls, are much easier to detect than smaller targets. Thus, the associatedoperating range for smaller targets will be shorter. The range to detect people will be affected by a variety of factors suchas a person’s size, clothing, orientation to the sensor and the sensor’s field-of-view. In general, given these factors, people
can be detected at a maximum distance of 3-4m away from the ICU-20201 sensor.

4.4 DEVICE MODES OF OPERATION
4.4.1 Free-Running ModeIn the free-running measurement mode, the ICU-20201 runs autonomously at a user specified measurement rate derived
from either the internal LFCLK or the external LFCLK pin. In this mode, the INT1 or INT2 pin is configured as an output. The
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ICU-20201
ICU-20201 pulses the INT pin low when a new range sample is available. At this point, the host processor may read thesample data from the ICU-20201 over the SPI interface. When in free-running mode using the internal LFCLK, there mustnot be another ICU-20201 within range of the device, otherwise interference may occur, as each device will operate atslightly different measurement rates.

4.4.2 Hardware-Triggered ModeIn the hardware triggered mode, one of the INT1/2 pins is used to trigger the start of a measurement. The ICU-20201
remains in an idle condition until triggered by pulsing the INT pin low. The measurement will start with deterministic
latency relative to the falling edge on INT. This mode is most useful for synchronizing several ICU-20201 transceivers. The
host controller can use the individual INT pins of several transceivers to coordinate the exact timing. A single INT1/2 pin canbe used bi-directionally, or the transceiver can be configured to accept a trigger on one INT pin and indicate data ready on
another.

4.4.3 Software-Triggered ModeIn the software triggered mode, the host processor triggers the start of a measurement by a SPI write to the transceiver.
INT1 or INT2 are pulsed low by ICU-20201 when the measurement is complete. By chip selecting and writing to several ICU20201 simultaneously, it is possible to synchronize the start of a measurement using this method as well; however,
hardware trigger mode is recommended for best performance.

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4.5 COEXISTENCE NEAR OTHER ICU-20201
Nearby ICU-20201 which have similar fop can receive sound from one another if they are within <10m of each other. Since
fop varies from part-to-part, it is not possible to design a system that relies on detection between two ICU-20201 (for theseapplications, please consider CH101 or ICU-10201). However, two ICU-20201 of a similar frequency will interfere, causing
the received I/Q data to have a pulse from the other transceiver, in addition to whatever pulse-echo response was
expected.
When ICU-20201 has an algorithm loaded that ignores stationary targets (e.g., static target rejection mode or presenceFW), it is possible for multiple ICU-20201 to co-exist in the same space without detecting the other device as a target, if
each ICU-20201 is triggered at a precise measurement rate (such as 10Hz).
The measurement rate must be derived from a quality crystal- or MEMS-based oscillator. When ICU-20201 receives a pulse
from a nearby ICU-20201, it will interpret it as a stationary target. The reason is that both ICU-20201 will be running at
nearly the same measurement rate (excepting the tolerance of the crystals used), so the receiving ICU-20201 will hear theother ICU-20201’s pulse at nearly the same time during each measurement.
There are two recommended methods to operate ICU-20201 at a precise measurement rate to ensure good coexistence
behavior are a) to use Hardware-triggered mode with a timer driven by a crystal-derived clock; or b) to use Free-runningmode with a crystal-derived clock input to the LFCLK pin and ICU-20201 configured appropriately. In both cases, the crystalderived clock must match the clock used by the 2nd ICU-20201 to ensure that ICU-20201 will not detect the nearby device.

4.6 PCB REFLOW RECOMMENDATIONS:
See App Note AN-000159 CH101 and CH201 Ultrasonic Transceiver Handling and Assembly Guidelines.

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4.7 TYPICAL OPERATING CIRCUITS

Figure 3. Single Transceiver Operation. Dashed connections are optional.

Figure 4. Multi-Transceiver Operation. Dashed connections are optional. Add additional transceivers by adding CS_B and INT1 for each
additional transceiver and sharing common MOSI/MISO/SCLK connections.

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4.8 RECOMMENDED PCBA LAYOUT

Figure 5. Recommended SMT dimensions for solder mask and PCB land pads

The PCB layout for ICU-20201 should adhere to the following recommendations:•

PCB design should be as symmetrical as possibleoSince the transceiver has very low power consumption, large VDD and GND traces are not requiredo

Do not place vias or traces on the top metal layer within the transceiver footprint•

PCB land and connecting traces should be symmetrical•

PCB land height and width should be equal the transceiver pad height and width (Figure 5)•

Solder mask opening should exceed PCB land height and width by 0.1mm (Figure 5)•

Placement of the transceiver on the PCB should avoid locations close to hot spots such as microprocessors andpoints of mechanical stress such as pushbuttons and screws

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ICU-20201
5 PACKAGE INFORMATION
5.1 PIN CONFIGURATION

Figure 6. ICU-20201 Package Bottom View

5.2 PACKAGE DIMENSIONS

Note: All dimensions and tolerances conform to ANSI Y14.5M-1994.

Figure 7.Package dimensions

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6 ORDERING INFORMATION
6.1 PART NUMBER DESIGNATIONThis datasheet specifies the following part numbers:
PART NUMBER
ICU-20201

PACKAGE BODY
3.5 mm x 3.5 mm x 1.26 mm LGA-14L

QUANTITY
1,000

PACKAGING
7” Tape and Reel

Table 7. ICU-20201 Part Number

6.2 PACKAGE MARKING

Figure 8. Packaging Marking

6.3 TAPE & REEL SPECIFICATION

Dimensions in mm

Figure 9. Tape & Reel Specifications

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ICU-20201
6.4 SHIPPING LABELA Shipping Label will be attached to the reel, bag and box. The information provided on the label is as follows:
•
•
•
•
•

Device: This is the full part number
Lot Number: TDK/InvenSense manufacturing lot number
Date Code: Date the lot was sealed in the moisture proof bag
Quantity: Number of components on the reel
2D Barcode: Contains Lot No., quantity and reel/bag/box number

Figure 10. Shipping Label

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ICU-20201
7 SMARTSONIC™ FAMILY
Time-of-Flight Vision Platform
TDK’s ultrasonic Time-of-Flight (ToF) sensors integrate a MEMS PMUT (Piezoelectric Micromachined Ultrasonic Transducer)
with an ultra-low power SoC (System on Chip) in a miniature reflowable package.
These sensor solutions are capable of ranging to targets of any composition up to 5 meters in any lighting condition, making
them ideal for a variety of applications including: obstacle avoidance, presence detection, robotics, security & surveillance,
AR/VR, drones, liquid level sensing, smart home/building, and general IoT.
For more information on SmartSonic products, please visit invensense.tdk.com.

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ICU-20201
8 REVISION HISTORYDATEREVISION

CHANGES

09/14/2021

1.0

Initial Release

01/03/2022

1.1

Fix typo in section 6.1 Package Body description

01/12/2022

1.2

07/27/2022

1.3

2/28/2023

1.4

Update VDDIO range in Ultrasonic Transceiver Characteristics to include VDDIO=1.8V andnote about 1.9V to 2.96V operation
Update VDDIO decoupling capacitor from 0.1µF to 1µF
Added 3-wire SPI Spec Table and Timing Diagram.
Filled in the SPI Spec Table TBDs.
Update VDDIO range in Ultrasonic Transceiver Characteristics to VDDIO = 1.71V to 3.63V.
Safe Launch Release

3/15/2023

1.5

Corrected maximum idle current typoThis information furnished by InvenSense or its affiliates (“TDK InvenSense”) is believed to be accurate and reliable. However, no responsibility is assumed
by TDK InvenSense for its use, or for any infringements of patents or other rights of third parties that may result from its use. Specifications are subject tochange without notice. TDK InvenSense reserves the right to make changes to this product, including its circuits and software, in order to improve its
design and/or performance, without prior notice. TDK InvenSense makes no warranties, neither expressed nor implied, regarding the information andspecifications contained in this document. TDK InvenSense assumes no responsibility for any claims or damages arising from information contained in thisdocument, or from the use of products and services detailed therein. This includes, but is not limited to, claims or damages based on the infringement ofpatents, copyrights, mask work and/or other intellectual property rights.
Certain intellectual property owned by InvenSense and described in this document is patent protected. No license is granted by implication or otherwise
under any patent or patent rights of InvenSense. This publication supersedes and replaces all information previously supplied . Trademarks that areregistered trademarks are the property of their respective companies. TDK InvenSense sensors should not be used or sold in the development, storage,
production or utilization of any conventional or mass-destructive weapons or for any other weapons or life threatening applications, as well as in any otherlife critical applications such as medical equipment, transportation, aerospace and nuclear instruments, undersea equipment, power plant equipment,
disaster prevention and crime prevention equipment.
©2023 InvenSense. All rights reserved. InvenSense, SmartMotion, MotionProcessing, MotionProcessor, SensorStudio, UltraPrint, MotionTracking, CHIRP
Microsystems, SmartBug, SonicLink, Digital Motion Processor, AAR, and the InvenSense logo are registered trademarks of InvenSense, Inc. The TDK logo isa trademark of TDK Corporation. Other company and product names may be trademarks of the respective companies with which they are associated.

©2023 InvenSense. All rights reserved.

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