T3902
Bottom Port PDM Low‐Power Multi‐Mode
Microphone With High AOP ModeAPPLICATIONSGENERAL DESCRIPTIONThe T3902 is a low‐power, low‐noise digital MEMS
microphone in a small package. The T3902 consists of a
MEMS microphone element and an impedance converter
amplifier followed by a fourth‐order Σ‐Δ modulator. The pulse
density modulated (PDM) interface allows two microphones
to be time multiplexed on a data line using a single clock.
The T3902 has multiple modes of operation: High
Performance, Low Power (AlwaysOn), Standard and Sleep.
The T3902 has low power and high SNR in all operationalmodes. It has 126 dB SPL AOP in High Performance mode, and120 dB SPL AOP in Standard and Low‐Power modes.
The T3902 is available in a small 3.5 × 2.65 × 0.98 mm
surface‐mount package. It is reflow solder compatible withno sensitivity degradation.

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FEATURESSPEC

LOW‐POWER
MODE

STANDARD
MODE

HIGH
PERFORMANCE
MODE

Sensitivity
SNR
Current
AOP
Clock−26 dB FS ±1 dB
63 dBA
185 µA
120 dB SPL
400 – 800 kHz−26 dB FS ±1 dB
64.5 dBA
430 µA
120 dB SPL
1.0 – 3.3 MHz−32 dB FS ±1 dB
64 dBA
650 µA
126 dB SPL
4.1 – 4.8 MHz

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FUNCTIONAL BLOCK DIAGRAM

InvenSense, Inc. reserves the right to change the detailspecifications as may be required to permit
improvements in the design of its products.

Smartphones
Microphone Arrays
Tablets
CamerasBluetooth Headsets
Notebook PCs
Security and Surveillance

3.5 × 2.65 × 0.98 mm surface‐mount package
Low power: 185 µA in Low‐Power Mode
Extended frequency response from 36 Hz to >20 kHz
Sleep Mode: 12 µA
High power supply rejection (PSR): −97 dB FS
Fourth‐order Σ‐Δ modulator
Digital pulse density modulation (PDM) output
Compatible with Sn/Pb and Pb‐free solder processes
RoHS/WEEE compliant

ORDERING INFORMATIONPARTTEMP RANGEPACKAGING

MMICT3902‐00‐012
EV_T3902‐FX−40°C to +85°C—

13” Tape and Reel

InvenSense Inc.
1745 Technology Drive, San Jose, CA 95110 U.S.A+1(408) 988–7339
www.invensense.com

Document Number: DS‐000357
Revision: 1.0
Rev Date: 4/15/2020

T3902TABLE OF CONTENTS
General Description ..................................................................................................................................................................... 1
Applications ................................................................................................................................................................................. 1
Features ....................................................................................................................................................................................... 1
Functional Block Diagram ............................................................................................................................................................ 1
Ordering Information................................................................................................................................................................... 1
Table of Contents .................................................................................................................................................................................... 2
Specifications .......................................................................................................................................................................................... 4
Table 1. Acoustical/Electrical Characteristics – General .............................................................................................................. 4
Table 2. Acoustical/Electrical Characteristics – High‐Performance Mode ................................................................................... 4
Table 3. Acoustical/Electrical Characteristics – Standard Mode.................................................................................................. 5
Table 4. Acoustical/Electrical Characteristics – Low‐Power Mode .............................................................................................. 5
Table 5. Digital Input/Output Characteristics .............................................................................................................................. 6
Table 6. PDM Digital Input/Output .............................................................................................................................................. 6
Timing Diagram ............................................................................................................................................................................ 7
Absolute Maximum Ratings .................................................................................................................................................................... 8
Table 7. Absolute Maximum Ratings ........................................................................................................................................... 8ESD Caution ................................................................................................................................................................................. 8
Soldering Profile........................................................................................................................................................................... 9
Table 8. Recommended Soldering Profile*.................................................................................................................................. 9
Pin Configurations And Function Descriptions ..................................................................................................................................... 10
Table 9. Pin Function Descriptions............................................................................................................................................. 10
Typical Performance Characteristics..................................................................................................................................................... 11
Theory Of Operation ............................................................................................................................................................................. 12
PDM Data Format ...................................................................................................................................................................... 12
Table 10. T3902 Channel Setting ............................................................................................................................................... 12
PDM Microphone Sensitivity ..................................................................................................................................................... 12
Applications Information ...................................................................................................................................................................... 14
Low Power Mode ....................................................................................................................................................................... 14
Dynamic Range Considerations ................................................................................................................................................. 14
Connecting PDM Microphones .................................................................................................................................................. 14
Sleep Mode ................................................................................................................................................................................ 16
Start‐Up Time............................................................................................................................................................................. 16
Supporting Documents ......................................................................................................................................................................... 17
Application Notes ...................................................................................................................................................................... 17
PCB Design And Land Pattern Layout ................................................................................................................................................... 18
PCB Material And Thickness ...................................................................................................................................................... 18
Handling Instructions ............................................................................................................................................................................ 19
Pick And Place Equipment ......................................................................................................................................................... 19
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T3902
Reflow Solder ............................................................................................................................................................................. 19
Board Wash ............................................................................................................................................................................... 19
Outline Dimensions............................................................................................................................................................................... 20
Ordering Guide .......................................................................................................................................................................... 20
Revision History ......................................................................................................................................................................... 21
Compliance Declaration Disclaimer ...................................................................................................................................................... 22

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T3902
SPECIFICATIONSTABLE 1. ACOUSTICAL/ELECTRICAL CHARACTERISTICS – GENERALTA = 25°C, VDD = 1.8 to 3.3 V, SCK = 2.4 MHz, 50× decimation, CLOAD = 30 pF unless otherwise noted. Typical specifications are notguaranteed.
PARAMETERCONDITIONS
MIN
TYP
MAX
UNITS
NOTES
PERFORMANCE
Directionality
Omni
Output Polarity
Input acoustic pressure vs.
Non‐Inverted
output data
Supply Voltage (VDD)
1.65
3.63
V
Sleep Mode Current (IS)SCK < 200 kHz
12
20
µA

TABLE 2. ACOUSTICAL/ELECTRICAL CHARACTERISTICS – HIGH‐PERFORMANCE MODE
TA = 25°C, VDD = 1.8 to 3.3 V, SCK = 4.8 MHz, 50× decimation, CLOAD = 30 pF unless otherwise noted. Typical specifications are notguaranteed.
PARAMETERCONDITIONS
MIN
TYP
MAX
UNITS
NOTES
Sensitivity
1 kHz, 94 dB SPL
−33
−32
−31
dB FS
1, 2
Signal‐to‐Noise Ratio (SNR)
20 kHz bandwidth, A‐weighted
64dBA
Equivalent Input Noise (EIN)
20 kHz bandwidth, A‐weighted
30
dBA SPL
Dynamic Range
Derived from EIN and AOP
96
dB
Low frequency −3 dB point
36
Hz
3
Total Harmonic Distortion (THD)
105 dB SPL
0.2
1%Power Supply Rejection (PSR)
217 Hz, 100 mV p‐p square wave
superimposed on VDD = 1.8 V, A‐
−97
dB FS
weighted
Power Supply Rejection—Swept
1 kHz sine wave
−100
dB FS
Sine
Acoustic Overload Point
10% THD126
dB SPL
Full‐Scale Acoustic Level
0 dB FS output
126
dB SPL
Supply Current (IS)VDD = 1.8 V, no load
650
750
µA
Note 1: Sensitivity is relative to the RMS level of a sine wave with positive amplitude equal to 100% 1s density and negative amplitude equal to 0% 1s density.
Note 2: The sensitivity shall not deviate more than 1.0 dB from its initial value after reliability tests.
Note 3: See Figure 4.

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T3902TABLE 3. ACOUSTICAL/ELECTRICAL CHARACTERISTICS – STANDARD MODE
TA = 25°C, VDD = 1.8 to 3.3 V, SCK = 2.4 MHz, 50× decimation, CLOAD = 30 pF unless otherwise noted. Typical specifications are notguaranteed.
PARAMETERCONDITIONS
MIN
TYP
MAX
UNITS
NOTES
Sensitivity
1 kHz, 94 dB SPL
−27
−26
−25
dB FS
1, 2
Signal‐to‐Noise Ratio (SNR)
20 kHz bandwidth, A‐weighted
64.5
dBA
Equivalent Input Noise (EIN)
20 kHz bandwidth, A‐weighted
29.5
dBA SPL
Dynamic Range
Derived from EIN and AOP
90.5
dB
Low frequency −3 dB point
36
Hz
3
Total Harmonic Distortion (THD)
105 dB SPL
0.2
1%Power Supply Rejection (PSR)
217 Hz, 100 mV p‐p square wave
superimposed on VDD = 1.8 V, A‐
−97
dB FS
weighted
Power Supply Rejection—Swept
1 kHz sine wave
−104
dB FS
Sine
Acoustic Overload Point
10% THD120
dB SPL
Full‐Scale Acoustic Level
0 dB FS output
120
dB SPL
Supply Current (IS)VDD = 1.8 V, no load
430
500
µA
Note 1: Sensitivity is relative to the RMS level of a sine wave with positive amplitude equal to 100% 1s density and negative amplitude equal to 0% 1s density.
Note 2: The sensitivity shall not deviate more than 1.0 dB from its initial value after reliability tests.
Note 3: See See Figure 4.

TABLE 4. ACOUSTICAL/ELECTRICAL CHARACTERISTICS – LOW‐POWER MODE
TA = 25°C, VDD = 1.8 to 3.3 V, SCK = 768 kHz, 50× decimation, CLOAD = 30 pF unless otherwise noted. Typical specifications are notguaranteed.
PARAMETERCONDITIONS
MIN
TYP
MAX
UNITS
NOTES
Sensitivity
1 kHz, 94 dB SPL
−27
−26
−25
dB FS
1, 2
Signal‐to‐Noise Ratio (SNR)
8 kHz bandwidth, A‐weighted
63dBA
Equivalent Input Noise (EIN)
8 kHz bandwidth, A‐weighted
31
dBA SPL
Dynamic Range
Derived from EIN and AOP
89
dB
Low frequency −3 dB point
36
Hz
3
Total Harmonic Distortion (THD)
105 dB SPL
0.2
1%Power Supply Rejection (PSR)
217 Hz, 100 mV p‐p square wave
superimposed on VDD = 1.8 V, A‐
−97
dB FS
weighted
Power Supply Rejection—Swept
1 kHz sine wave
−98
dB FS
Sine
Acoustic Overload Point
10% THD120
dB SPL
Full‐Scale Acoustic Level
0 dB FS output
120
dB SPL
Supply Current (IS)VDD = 1.8 V, no load
185
225
µA
Note 1: Sensitivity is relative to the RMS level of a sine wave with positive amplitude equal to 100% 1s density and negative amplitude equal to 0% 1s density.
Note 2: The sensitivity shall not deviate more than 1.0 dB from its initial value after reliability tests.
Note 3: See Figure 4.

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T3902TABLE 5. DIGITAL INPUT/OUTPUT CHARACTERISTICS
TA = 25°C, 1.8 V < VDD < 3.3 V, unless otherwise noted.
PARAMETERCONDITIONSMINInput Voltage High (VIH)

0.65 x VDD

TYP

MAX

UNITS

NOTES

V

Input Voltage Low (VIL)

0.35 x VDD

Output Voltage High (VOH)

ILOAD = 0.5 mA

Output Voltage Low (VOL)ILOAD = 0.5 mA

0Output DC Offset
Latency

Percent of full scale

3<30

0.7 x VDD

VV

VDD
0.3 x VDD

V%
µs

TABLE 6. PDM DIGITAL INPUT/OUTPUT
TA = 25°C, 1.8 V < VDD < 3.3 V, unless otherwise noted.
PARAMETERCONDITIONS

MIN

TYP

MAX

UNITS

1

ms

20

ms

20

ms

10

ms

10

ms

2500

ns

200

kHz

NOTES

MODE SWITCHING
Sleep Time
Wake‐Up Time

Wake‐Up Time

Switching time
Switching time
INPUT
tCLKINTime from fCLK falling <200 kHz
High‐Performance & Standard modes,
Sleep Mode to fCLK >1 MHz, output
within 0.5 dB of final sensitivity, poweron
Low‐Power Mode, Sleep Mode to fCLK
>400 kHz, output within 0.5 dB of final
sensitivity, power on
Between Low‐Power and Standard
Modes
Between Low‐Power and High‐
Performance Modes
Input clock period

208

Sleep Mode
Clock Frequency (CLK)

Clock Duty Cycle
tRISE
tFALL
OUTPUT
t1OUTEN
t1OUTDIS
t2OUTEN
t2OUTDIS

Low‐Power Mode

400

800

kHz

Standard Mode

1.0

3.3

MHz

High‐Performance ModefCLK <3.3 MHz
fCLK >4.1 MHz
CLK rise time (10% to 90% level)
CLK fall time (90% to 10% level)

4.1

4.8

40
48

60
52
25
25

MHz
%
%
ns
ns

DATA1 (right) driven after falling clockedge
DATA1 (right) disabled after risingclock edge
DATA2 (left) driven after rising clockedge
DATA2 (left) disabled after falling clock
edge

50

Note 1: Guaranteed by design

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5

ns
40

50
5

ns
ns

40

ns

1
1

T3902TIMING DIAGRAM
tCLKIN
CLK

tFALL

tRISE
t1OUTEN

t1OUTDISDATA1t2OUTDISDATA2t2OUTEN

Figure 1. Pulse Density Modulated Output Timing

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T3902
ABSOLUTE MAXIMUM RATINGS
Stress above those listed as Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only
and functional operation of the device at these conditions is not implied. Exposure to the absolute maximum ratings conditions forextended periods may affect device reliability.

TABLE 7. ABSOLUTE MAXIMUM RATINGSPARAMETERRATING−0.3 V to +3.63 V

Supply Voltage (VDD)
Digital Pin Input Voltage
Mechanical Shock−0.3 V to VDD + 0.3 V or 3.63 V, whichever is less
10,000 g

Vibration

Per MIL‐STD‐883 Method 2007, Test Condition B

Temperature Range
Biased−40°C to +85°C

Storage−55°C to +150°C

ESD CAUTION
ESD (electrostatic discharge) sensitive device.
Charged devices and circuit boards candischarge without detection. Although thisproduct features patented or proprietary
protection circuitry, damage may occur on
devices subjected to high energy ESD.
Therefore proper ESD precautions should betaken to avoid performance degradation orloss of functionality.

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T3902SOLDERING PROFILE
CRITICAL ZONETL TO TPtP

TP

TEMPERATURE

RAMP-UP
TL

tL

TSMAX
TSMIN

tS

RAMP-DOWNPREHEAT

t25°C TO PEAK TEMPERATURE
TIME

Figure 2. Recommended Soldering Profile Limits

TABLE 8. RECOMMENDED SOLDERING PROFILE*PROFILE FEATURE
Average Ramp Rate (TL to TP)
Minimum Temperature(TSMIN)
Maximum
PreheatTemperature (TSMAX)Time (TSMIN to TSMAX), tS
Ramp‐Up Rate (TSMAX to TL)Time Maintained Above Liquidous (tL)
Liquidous Temperature (TL)
Peak Temperature (TP)Sn63/Pb37
1.25°C/sec max

Pb‐Free
1.25°C/sec max

100°C

100°C

150°C

200°C

60 sec to 75 sec
1.25°C/sec
45 sec to 75 sec
183°C

60 sec to 75 sec
1.25°C/sec~50 sec
217°C

215°C +3°C/−3°C

260°C +0°C/−5°C

Time Within +5°C of Actual Peak
Temperature (tP)

20 sec to 30 sec

20 sec to 30 sec

Ramp‐Down Rate

3°C/sec max

3°C/sec max

Time +25°C (t25°C) to Peak Temperature

5 min max

5 min max

*The reflow profile in Table 8 is recommended for board manufacturing with InvenSense MEMS microphones. All microphones arealso compatible with the J‐STD‐020 profile

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T3902PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS

34SELECT
CLK

GND

2

DATA
5

1
VDD

Figure 3. Pin Configuration (Top View, Terminal Side Down)

TABLE 9. PIN FUNCTION DESCRIPTIONS
PIN

NAME

FUNCTION

1

DATA

Digital Output Signal (DATA1 or DATA2)2

SELECT

3

GND

Left Channel or Right Channel Select:
DATA 1 (right): SELECT tied to GNDDATA 2 (left): SELECT tied to VDD. In this setting, SELECT should be tied to the same voltage
source as the VDD pin.
Ground4

CLK

Clock Input to Microphone

5

VDD

Power Supply. For best performance and to avoid potential parasitic artifacts, place a 0.1 µF(100 nF) ceramic type X7R capacitor between Pin 5 (VDD) and ground. Place the capacitor as
close to Pin 5 as possible.

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T3902TYPICAL PERFORMANCE CHARACTERISTICS
20.0

High Performance Mode
Standard Mode

10.0

Low Power Mode
THD+N (%)

NORMALIZED AMPLITUDE (dB)

10.00

0.0

1.00

0.10

‐10.0

‐20.0

0.01
10

100

1000
FREQUENCY (Hz)

10000

90

100

110
120
INPUT AMPLITUDE (dB SPL)

130

Figure 5. THD + N vs. Input Level

Figure 4. Typical Frequency Response

0.0

0.00
‐5.00

‐20.0
OUTPUT AMPLITUDE (dBFS)‐10.00

PSRR (dB)

‐40.0
‐60.0
‐80.0
‐100.0‐15.00‐20.00High Performance Mode

‐25.00‐30.00Standard Mode

‐35.00

Low Power Mode

‐40.00‐120.0100

1000
FREQUENCY (Hz)

10000

100

110
120
INPUT AMPLITUDE (dB SPL)

Figure 7. Linearity

Figure 6. Power Supply Rejection (PSR) vs. Frequency

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90

130

T3902
THEORY OF OPERATIONPDM DATA FORMATThe output from the DATA pin of the T3902 is in pulse density modulated (PDM) format. This data is the 1‐bit output of a fourth‐order Σ‐Δ modulator. The data is encoded so that the left channel is clocked on the falling edge of CLK, and the right channel is clockedon the rising edge of CLK. After driving the DATA signal high or low in the appropriate half frame of the CLK signal, the DATA driver ofthe microphone tristates. In this way, two microphones, one set to the left channel and the other to the right, can drive a single DATA
line. See Figure 1 for a timing diagram of the PDM data format; the DATA1 and DATA2 lines shown in this figure are two halves of thesingle physical DATA signal. Figure 8 shows a diagram of the two stereo channels sharing a common DATA line.
CLK

DATA2 (L)DATA

DATA1 (R)DATA2 (L)DATA1 (R)

Figure 8. Stereo PDM Format

If only one microphone is connected to the DATA signal, the output is only clocked on a single edge (Figure 9). For example, a leftchannel microphone is never clocked on the rising edge of CLK. In a single microphone application, each bit of the DATA signal istypically held for the full CLK period until the next transition because the leakage of the DATA line is not enough to discharge the line
while the driver is tristated.

CLK

DATA

DATA1 (R)DATA1 (R)DATA1 (R)

Figure 9. Mono PDM Format

See Table 10 for the channel assignments according to the logic level on the SELECT pin.

TABLE 10. T3902 CHANNEL SETTINGSELECT Pin Setting
Low (tie to GND)
High (tie to VDD)

ChannelRight (DATA1)
Left (DATA2)

For PDM data, the density of the pulses indicates the signal amplitude. A high density of high pulses indicates a signal near positive
full scale, and a high density of low pulses indicates a signal near negative full scale. A perfect zero (dc) audio signal shows analternating pattern of high and low pulses.
The output PDM data signal has a dc offset of about 3% of full scale. A high‐pass filter in the codec that is connected to the digital
microphone and does not affect the performance of the microphone typically removes this dc signal.

PDM MICROPHONE SENSITIVITY
The sensitivity of a PDM output microphone is specified with the unit dB FS (decibels relative to digital full scale). A 0 dB FS sine
wave is defined as a signal whose peak just touches the full‐scale code of the digital word (see Figure 10). This measurement
convention also means that signals with a different crest factor may have an RMS level higher than 0 dB FS. For example, a full‐scalesquare wave has an RMS level of 3 dB FS.
This definition of a 0 dB FS signal must be understood when measuring the sensitivity of the T3902. A 1 kHz sine wave at a 94 dB SPL
acoustic input to the T3902 results in an output signal with a −26 dB FS level in Standard Mode and −32 dB FS in High Performance
Mode. In the Standard Mode example, the output digital word peaks at −26 dB below the digital full‐scale level. A common
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T3902
misunderstanding is that the output has an RMS level of −29 dB FS; however, this is not true because of the definition of the 0 dB FS
sine wave.
1.0
0.8

DIGITAL AMPLITUDE (D)

0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

TIME (ms)Figure 10. 1 kHz, 0 dB FS Sine Wave

There is not a commonly accepted unit of measurement to express the instantaneous level, as opposed to the RMS level of thesignal, of a digital signal output from the microphone. Some measurement systems express the instantaneous level of an individual
sample in units of D, where 1.0 D is digital full scale. In this case, a −26 dB FS sine wave has peaks at 0.05 D.

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T3902
APPLICATIONS INFORMATIONLOW POWER MODE
Low Power Mode (LPM) enables the T3902 to be used in an AlwaysOn listening mode for keyword spotting and ambient soundanalysis. The T3902 will enter LPM when the frequency of SCK is between 400 and 800 kHz. In this mode, the microphone consumes
only 185 µA while retaining high electro‐acoustic performance.
When one microphone is in LPM for AlwaysOn listening, a second microphone sharing the same data line may be powered down. In
this case, where one microphone is powered up and another is powered down by disabling the VDD supply or in sleep mode by
reducing the frequency of a separate clock source, the disabled microphone does not present a load to the signal on the LPM
microphone’s DATA pin.

DYNAMIC RANGE CONSIDERATIONS
The full‐scale digital output (0 dB FS) of the T3902 is mapped to an acoustic input of 126 dB SPL in high‐performance mode. The
microphone clips (THD = 10%) at 126 dB SPL (see Figure 5); however, it continues to output an increasingly distorted signal abovethat point. The peak output level, which is controlled by the modulator, limits at 0 dB FS (see Figure 7).
To fully use the 96 dB dynamic range of the output data of the T3902 in a design, the digital signal processor (DSP), analog‐to‐digitalconverter (ADC), or codec circuit following it must be chosen carefully. The decimation filter that inputs the PDM signal from the T3902
must have a dynamic range sufficiently better than the dynamic range of the microphone so that the overall noise performance ofthe system is not degraded. If the decimation filter has a dynamic range of 10 dB better than the microphone, the overall system
noise only degrades by 0.4 dB. This 106 dB filter dynamic range requires the filter to have at least 18 bit resolution.

CONNECTING PDM MICROPHONESA PDM output microphone is typically connected to a codec with a dedicated PDM input. This codec separately decodes the left and rightchannels and filters the high sample rate modulated data back to the audio frequency band. This codec also generates the clock for the
PDM microphones or is synchronous with the source that is generating the clock. Figure 11 and Figure 12 show mono and stereo
connections of the T3902 to a codec. The mono connection shows an T3902 set to output data on the right channel. To output on theleft channel, tie the SELECT pin to VDD instead of tying it to GND.
1.8V TO 3.3V
0.1µF

CODEC

VDD
ICS‐41350
T3902
SELECT

CLK

CLOCK OUTPUTDATADATA INPUT

GND

Figure 11. Mono PDM Microphone (Right Channel) Connection to Codec

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T3902
1.8V TO 3.3V
0.1µF

CODEC

VDD
CLK

CLOCK OUTPUTDATADATA INPUT

ICS‐41350
T3902
SELECT

GND

1.8V TO 3.3V
0.1µF

VDD
ICS‐41350
T3902
SELECT

CLK
DATA
GND

Figure 12. Stereo PDM Microphone Connection to Codec

Decouple the VDD pin of the T3902 to GND with a 0.1 µF capacitor. Place this capacitor as close to VDD as the printed circuit board(PCB) layout allows.
Do not use a pull‐up or pull‐down resistor on the PDM data signal line because it can pull the signal to an incorrect state during the periodthat the signal line is tristated.
The DATA signal does not need to be buffered in normal use when the T3902 microphone(s) is placed close to the codec on the PCB. If the
DATA signal must be driven over a long cable (>15 cm) or other large capacitive load, a digital buffer may be required. Only use a signal
buffer on the DATA line when one microphone is in use or after the point where two microphones are connected (see Figure 13). The
DATA output of each microphone in a stereo configuration cannot be individually buffered because the two buffer outputs cannot
drive a single signal line. If a buffer is used, take care to select one with low propagation delay so that the timing of the data
connected to the codec is not corrupted.
CODEC

ICS‐41350
T3902
CLK

CLOCK OUTPUTDATADATA INPUT

ICS‐41350
T3902
CLK

DATA

Figure 13. Buffered Connections Between Stereo T3902s and a Codec

When long wires are used to connect the codec to the T3902, a source termination resistor can be used on the clock output of thecodec instead of a buffer to minimize signal overshoot or ringing. Match the value of this resistor to the characteristic impedance ofPage 15 of 22
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T3902
the CLK trace on the PCB. Depending on the drive capability of the codec clock output, a buffer may still be needed, as shown in Figure
13.

SLEEP MODE
The microphone enters sleep mode when the clock frequency falls below 200 kHz. In this mode, the microphone data output is in a highimpedance state. The current consumption in sleep mode is less than 20 µA.
The T3902 enters sleep mode within 1 ms of the clock frequency falling below 200 kHz. The microphone wakes up from sleep modeand begins to output data within 20 ms of when the clock becomes active.
In sleep mode:
If the SELECT signal is logic high, the DATA pin will be pulled low to GND.
If the SELECT signal is logic low, the DATA pin will be high impedance (floating).

CLK

SELECT

DATA<200kHz or float

VDD

GND

<200kHz or float

GND

HiZ

START‐UP TIME
The start‐up time of the T3902 is less than 20 ms. The PDM data from the microphone is valid to be used as soon as the data is being
output.

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T3902SUPPORTING DOCUMENTS
For additional information, see the following documents.

APPLICATION NOTES
AN‐000048, PDM Digital Output MEMS Microphone Flex Evaluation Board User Guide
AN‐100, MEMS Microphone Handling and Assembly Guide
AN‐1003, Recommendations for Mounting and Connecting the Invensense, Bottom‐Ported MEMS Microphones
AN‐1112, Microphone Specifications Explained
AN‐1124, Recommendations for Sealing InvenSense Bottom‐Port MEMS Microphones from Dust and Liquid Ingress
AN‐1140, Microphone Array Beamforming

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T3902
PCB DESIGN AND LAND PATTERN LAYOUT
The recommended PCB land pattern for the T3902 is a 1:1 ratio of the solder pads on the microphone package, as shown in Figure 14.
Avoid applying solder paste to the sound hole in the PCB. A suggested solder paste stencil pattern layout is shown in Figure 15.
The response of the T3902 is not affected by the PCB hole size as long as the hole is not smaller than the sound port of the
microphone (0.375 mm in diameter). A 0.5 mm to 1 mm diameter for the hole is recommended. Take care to align the hole in the
microphone package with the hole in the PCB. The exact degree of the alignment does not affect the microphone performance as longas the holes are not partially or completely blocked.
0.522x0.725(4X)Ø1.625
Ø1.025

1.675

0.838

0.822

1.252

Figure 14. Recommended PCB Land Pattern Layout

0.422x0.625(4X)Ø1.625

Ø1.125

1.675

0.1(4x)

0.822

1.252

Figure 15. Suggested Solder Paste Stencil Pattern Layout

PCB MATERIAL AND THICKNESSThe performance of the T3902 is not affected by PCB thickness. The T3902 can be mounted on either a rigid or flexible PCB. A
flexible PCB with the microphone can be attached directly to the device housing with an adhesive layer. This mounting method
offers a reliable seal around the sound port while providing the shortest acoustic path for good sound quality.

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T3902
HANDLING INSTRUCTIONSPICK AND PLACE EQUIPMENT
The MEMS microphone can be handled using standard pick‐and‐place and chip shooting equipment. Take care to avoid damage to the
MEMS microphone structure as follows: Use a standard pickup tool to handle the microphone. Because the microphone hole is on the bottom of the package, thepickup tool can make contact with any part of the lid surface.
 Do not pick up the microphone with a vacuum tool that makes contact with the bottom side of the microphone.
Do not pull air out of or blow air into the microphone port.
 Do not use excessive force to place the microphone on the PCB.

REFLOW SOLDER
For best results, the soldering profile must be in accordance with the recommendations of the manufacturer of the solder paste used toattach the MEMS microphone to the PCB. It is recommended that the solder reflow profile not exceed the limit conditions specified
in Figure 2 and Table 8.

BOARD WASH
When washing the PCB, ensure that water does not make contact with the microphone port. Do not use blow‐off procedures orultrasonic cleaning.

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T3902OUTLINE DIMENSIONS
d
3.50

(4X)

0.10

0.522X0.725 (4x)j 0.10 m C A B

APIN 1
CORNER

0.125

PIN 1
CORNER

0.82
Ø1.625
Ø1.025(2.45)

2.65

2.650

1

2

5

4

Ø0.375

0.950
1.675

1.33

3
0.300

0.125

B

(3.30)

1.040
1.513
3.500

BOTTOM VIEWTOP VIEW
f0.10 C

0.98

SIDE VIEW(0.254)C

Figure 16. 5‐Terminal Chip Array Small Outline No Lead Cavity [LGA_CAV]
3.5 mm × 2.65 mm × 0.98 mm Body
Dimensions shown in millimeters
Dimension tolerance is ±0.15 mm unless otherwise specified

3902

Figure 17. Package Marking Specification (Top View)

ORDERING GUIDEPARTMMICT3902‐00‐012

TEMP RANGE−40°C to +85°C

PACKAGE
5‐Terminal LGA_CAVQUANTITY
10,000

EV_T3902‐FX—

Evaluation Board—

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PACKAGING
13” Tape and Reel

T3902REVISION HISTORYREVISION DATEREVISIONDESCRIPTION

12/16/2019

0.1

Initial version

2/12/2020

0.2

Updated Package Marking Specification

4/15/2020

1.0

Initial release

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T3902COMPLIANCE DECLARATION DISCLAIMER
InvenSense believes the environmental and other compliance information given in this document to be correct but cannot
guarantee accuracy or completeness. Conformity documents substantiating the specifications and component characteristics are on
file. InvenSense subcontracts manufacturing, and the information contained herein is based on data received from vendors andsuppliers, which has not been validated by InvenSense.

This information furnished by InvenSense, Inc. (“InvenSense”) is believed to be accurate and reliable. However, no responsibility is assumed by 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 to change without notice. 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. InvenSense makes
no warranties, neither expressed nor implied, regarding the information and specifications contained in this document. InvenSense assumes no responsibility for any
claims or damages arising from information contained in this document, or from the use of products and services detailed therein. This includes, but is not limited to,claims or damages based on the infringement of patents, 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 are registered trademarks are theproperty of their respective companies. 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 other life critical applications such as medical equipment,
transportation, aerospace and nuclear instruments, undersea equipment, power plant equipment, disaster prevention and crime prevention equipment.
©2019 InvenSense. All rights reserved. InvenSense, MotionTracking, MotionProcessing, MotionProcessor, MotionFusion, MotionApps, DMP, AAR, and the InvenSense
logo are trademarks of InvenSense, Inc. The InvenSense logo is a trademark of InvenSense Corporation. Other company and product names may be trademarks of therespective companies with which they are associated.

©2019 InvenSense. All rights reserved.

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