MODEL 1521



ANALOG SURFACE MOUNT ACCELEROMETER•••••••••••___Low Noise: 7 μg/√Hz typical for 2g Full Scale Version
Responds to frequencies from zero (DC) to 2000+ Hz
High Stability and Durability-55 to +125°C Operation±4V Differential Output+5 VDC, 5 mA Power (Typical)
Integrated Sensor & Amplifier
Internal Temperature Sensor
Nitrogen Damped & Hermetically Sealed
Serialized for Traceability
RoHS Compliant

0.350"L" SUFFIXPACKAGE

0.350

PositiveAcceleration

0.350

AVAILABLE G-RANGESFULL SCALE
ACCELERATION±2g20 PIN
JLCC
1521J-002

20 PIN
LCC
1521L-002±5g

1521J-005

1521L-005± 10 g

1521J-010

1521L-010± 25 g

1521J-025

1521L-025± 50 g

1521J-050

1521L-050± 100 g

1521J-100

1521L-100± 200 g

1521J-200

1521L-200± 400 g

1521J-400

1521L-400"J" SUFFIXPACKAGE

0.105

PositiveAcceleration

0.350

0.165

The Model 1521 is a low-cost, general-purpose integrated MEMS accelerometer for use in zero to medium frequency
industrial applications that require extremely low noise and reliable long-term stability. Each miniature, hermeticallysealed package combines a MEMS capacitive sense element and a custom integrated circuit that includes a sense
amplifier and differential output stage. It is relatively insensitive to temperature changes and gradients. Each device
is marked with a serial number on its top and bottom surfaces for traceability. An optional calibration test report(1521-TST) is also available for every unit showing the measured bias, scale factor, linearity, operating current, &frequency response.

ZERO (DC) TO MEDIUM FREQUENCY APPLICATIONSPERFORMANCEINPUTRANGEgSENSITIVITY,DIFFERENTIAL
mV/g

FREQUENCYRESPONSE(TYPICAL, 5%)Hz

FREQUENCYRESPONSE(TYPICAL, 3 DB)
Hz

FREQUENCYRESPONSE(MINIMUM, 3 DB)Hz

OUTPUT NOISE,DIFFERENTIAL(RMS, TYPICAL)
μg/(root Hz)±2±5±10±25±50±100±200±400

2000
800
400
160
80
4020
100 – 250
0 – 400
0 – 700
0 – 1300
0 – 1600
0 – 1700
0 – 1900
0 – 2000

0 – 525
0 – 800
0 – 1100
0 – 1750
0 – 2100
0 – 30000 – 3600
0 – 4200

0 – 300
0 – 420
0 – 660
0 – 1050
0 – 1400
0 – 1700
0 – 21000 – 2400

712182550100200400

By Model: VDD=VR=5.0 VDC, TC=25°C

MAX.
MECHANICALSHOCK (0.1 MS)
g (peak)
2000

5000

Single ended sensitivity is half of values shown.



SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc. • 13905 NE 128th Street, Kirkland WA 98034 • Phone: 425-391-8329 • Fax: 425-391-0446
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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETERPERFORMANCE - ALL VERSIONSAll Models: Unless otherwise specified VDD=VR=5.0 VDC, TC=25°C, Differential. Span = ±g range = 8000 mVPARAMETERMINTYPMAXUNITS

Bias Calibration Error (mV)
1640± mV
Bias Calibration Error (Span)
0.20.5± % of span
Bias Temperature Shift (TC= -55 to +125°C) 1-2000+200(PPM of span)/°C
Scale Factor Calibration Error 2
0.5
1±%
1Scale Factor Temperature Shift (TC= -55 to +125°C)
-200
0+200
PPM/°C
Non-Linearity (-90 to +90% of Full Scale) 1, 2
0.150.5± % of spanLong Term Bias Stability
1000
2000
± PPM of spanLong Term Scale Factor Stability
500
1000± PPM
Cross Axis Sensitivity
23±%
Input Axis Misalignment
510± mrad
Turn-On Transient (in less than 0.5ms)
75± PPM of FS
Output Impedance
90
Ohms
Operating Voltage 3
4.75
5.0
5.25
volts
Operating Current (IDD+IVR)
5.5
6.5
mA
Mass: ‘L’ package (add 0.06 grams for ‘J’ package)
0.62
grams
Case Operating Temperature-55 to +125°C
Voltage on VDD to GND-0.5V to 6.0V
Storage Temperature-55 to +125°C
Voltage on any Pin (except DV) to GND3 -0.5V to VDD+0.5VMax Reflow Solder Temperature+239°C
Voltage on DV to GND (Self-Test)±15V
Power Dissipation 35 mW
Note 1: Tighter tolerances are available on other SDI accelerometers.
Note 2: For 2g thru 50g only; 100g and greater versions are tested and specified from -65 to +65g.
Note 3: Voltages on pins other than DV, GND or VDD may exceed 0.50 volt above or below the supply voltages provided
the current is limited to 1 mA.
NOTICE: Minimize exposure above 125°C for maximum lifespan. Stresses greater than those listed above may cause permanentdamage to the device. These are maximum stress ratings only. Functional operation of the device at or above these conditions isnot implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability and lifespan.

OPERATION
The Model 1521 produces a differential +/-4 volts output voltage or single ended mode, 0.5 – 4.5 volts full scale, thevalue of which varies with acceleration as shown in the figures below. The sensitive axis is perpendicular to the bottomof the package, with positive acceleration resulting from a positive force pushing on the bottom of the package. The
seismic center is located on a centerline through the dual sense elements and halfway between them. The internal
electronics effectively cancel any errors due to rotation. Two reference voltages, +5.0 and +2.5 volts (nominal), arerequired; scale factor is ratiometric to the +5.0 volt reference voltage relative to GND, and both outputs at zeroacceleration are the same as the +2.5 volt input.

SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETERJQGground.

*1'VDD and GND (power): Pins (14) and (19) respectively. Power (+5 Volts DC) and95

SIGNAL DESCRIPTIONS






AOP and AON (output): Pins 12 and 16 respectively. Analog output voltages

'9 



proportional to acceleration. The AOP voltage increases (AON decreases) withpositive acceleration; at zero acceleration both outputs are nominally equal tothe +2.5 volt reference. The device experiences positive (+1g) acceleration withits lid facing up in the earth’s gravitational field. Use of differential mode isstrongly recommended for both lowest noise and highest accuracy operation.
Voltages can be measured ratio-metrically to VR for good repeatability without
requiring a separate precision reference voltage for an A/D.

JQG 9JQG



7239,(: $21,7 



$23YGG

YGG

 9''DV (input): Pin 4. Deflection Voltage. Connect to the 2.5 Volt pin for bestJQGrepeatability. A test input that applies an electrostatic force to the sense element, simulating a positive acceleration.
The nominal voltage at this pin is ½ VDD. DV voltages higher than required to bring the output to positive full scale may
cause device damage to 2g, 5g, and 10g devices.
VR (input): Pin 3. Voltage Reference. Tie to a good reference (not directly to VDD) for best scale factor repeatability. A
0.1μF bypass capacitor is recommended at this pin. The current is less than 100 μA.
2.5 Volt (input): Pin 17. Sets internal and output common mode value. Tie to a resistive voltage divider from +5 volts.
A 0.1μF bypass capacitor is recommended at this pin. The current is less than 50 μA.
IT (output): Pin 8. Temperature dependent current source. May be tied to VDD or left disconnected if not used.
Special Use Pins: Pins 9 and 11 should be tied to VDD, Pins 2, 5, 6, and 18 to GND.
** Pins 1, 7, 10, 13, 15, and 20 are reserved for future use and should remain unused **RECOMMENDED CONNECTIONSDEFLECTION VOLTAGE (DV) TESTINPUT: This test input applies anelectrostatic force to the senseelement, simulating a positive
acceleration of up to +10g. It has anominal input impedance of 32 kΩ
and a nominal open circuit voltage of½ VDD. For best accuracy during
normal operation, this input shouldbe left unconnected or connected toa voltage source equal to ½ of the VDD
supply.

+ 5V
115K
TEST INPUT(OPTIONAL)

14

3

0.1 uF

9VDD VR
417AOPDV

AON
2.5V
IT0.01uF

5K
2GND
5196

1216
8

OUTPUT (POSITIVE)OUTPUT (NEGATIVE)
TEMPERATURE DEPENDENTCURRENT SOURCE

181§·Δ ( AOP − AON ) ≈ k ¨ V DV − V DD ¸2©
¹

The change in differential output voltage (AOP - AON) is proportional to the square of the difference between thevoltage applied to the DV input (VDV) and ½ VDD. Only positive shifts in the output voltage may be generated by applying
voltage to the DV input. When voltage is applied to the DV input on 2g, 5g, or 10g devices, it should be applied graduallyto avoid damage. The application of DV voltages greater than required to bring the output to positive full scale may
cause device damage. The proportionality constant (k) varies for each device and is not characterized.
ESD and LATCH-UP CONSIDERATIONS: The model 1521 accelerometer is a CMOS device subject to damage fromlarge electrostatic discharges. Diode protection is provided on the inputs and outputs, and it is not easily damaged,
but care should be exercised during handling. However, individuals and tools should be grounded before coming incontact with the device. Although the 1521 is resistant to latch-up, inserting a 1521 into or removing it from a powered
socket may cause damage.
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc. • 13905 NE 128th Street, Kirkland WA 98034 • Phone: 425-391-8329 • Fax: 425-391-0446
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2

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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETEROPTIONAL INTERNAL TEMPERATURE SENSING
The model 1521 accelerometer contains a temperature
VT ≈ RT [(500 μA ) + [(1.5μA )(T − 25)]]
dependent current source that is output on pin 8. This signal isuseful for measuring the internal temperature of theΔVT= RT (1.5μA)
accelerometer so that any previously characterized bias andΔT
scale factor temperature dependence, for a particularªVºaccelerometer, can be corrected.
VT ≈ − RG « OFF + (500 μA) + [(1.5μA)(T − 25)]»¬ ROFFThe nominal output current at 25°C is ≈500 (±200) μA and thenominal sensitivity is 1.5 (±0.5) μA/°C. Fluctuations in VDD & VR
have little effect on the temperature reading. A reduction of 0.10
V to both VDD & VR will reduce the current about 1 μA, whichcorresponds to less than a 1°C change in reading. With a single
resistor RT = 2K between IT (pin 8) and GND the output voltage VT
will vary between +0.76 and +1.3 volts from -55 to +125°C, which
equates to a sensitivity of ≈+3 mV/°C.

ROFF =RG =¼− VOFFV§ T·¨ R ¸ + (500 μA) + [(1.5μA)(T − 25)]
G¹
©

− ΔVT
(1.5μA)(ΔT )ΔV= − RG (1.5μA)
ΔTIf a greater voltage change versus temperature or lower signal source impedance is needed, add the amplifier
as shown on the right side in Figure 2. With offset voltage VOFF = -5V, gain resistor RG = 15.0K and offset resistor
ROFF = 7.32K, the output voltage VT will vary between +4.5 and +0.5 Volts from -55 to +125°C, which equates to asensitivity of ≈ -29 mV/°C.
Figure 3 shows the voltage compliance of the temperature dependent current source (IT) at room temperature.
The voltage at pin 8 must be kept in the 0 to +3V range in order to achieve proper temperature readings.
+ 5VRG
115K41714
VDD

3VR

0.1 uF

9+ 5 to + 15V
ITDVAOP
2.5V
AON.01uF

5K25GND
19Figure 28VT

1216R OFF
- 5 to - 15 V

618
VOFF

SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc. • 13905 NE 128th Street, Kirkland WA 98034 • Phone: 425-391-8329 • Fax: 425-391-0446
www.silicondesigns.com[page 4]29-July-2020

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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETERPACKAGE DIMENSIONS*Dimensions “M,” “T,” and “U” locate sensing element’s center of mass.
Lid is electrically tied to terminal 19 (GND).
Controlling dimension: Inch.
DimTerminals are plated with 60 microinches min gold over 80 microinches
Amin nickel. This plating specification does not apply to the Pin-1
B
identifier mark on the bottom of the J-lead package version.
C
5. Package: 90% min alumina (black), lid: solder sealed kovar.
D"L" SUFFIX PACKAGE (20 PIN LEADLESS CERAMIC CHIP CARRIER)
EKC
F
*TF
GH
TERMINAL 20EJTERMINAL 1PositiveAcceleration
KL
*M
*M
GA
N
DP
"J" SUFFIX PACKAGE (20 PIN LEADED CHIP CARRIER)
RR*T*UInchesMin
Max
0.342 0.358
0.346 0.378
0.055 TYP
0.095 0.115
0.085 TYP
0.050 BSC
0.025 TYP
0.050 TYP
0.004 x 45°
0.010 R TYP
0.016 TYP
0.066 TYP
0.050 0.070
0.017 TYP
0.023 R TYP
0.085 TYP
0.175 TYP

Millimeters
Min
Max
8.69
9.09
8.79
9.60
1.40 TYP
2.41
2.92
2.16 TYP
1.27 BSC
0.64 TYP
1.27 TYP
0.10 x 45°
0.25 R TYP
0.41 TYP
1.68 TYP
1.27
1.78
0.43 TYP
0.58 R TYP
2.16 TYP
4.45 TYP

PBHJA

*UL

1.
2.
3.
4.

N

SOLDERING RECOMMENDATIONSRoHS Compliance:compliant.

The model 1521 does not contain elemental lead and is RoHS

Soldering: Solder reflow should not exceed 239°C, exceeding this temperature may resultin permanent damage.
Pre-Tinning of Accelerometer Leads is Recommended: To prevent gold migration
embrittlement of the solder joints, it is best to pre-tin the accelerometer leads.
LCC Solder Contact Plating Information: The plating composition andthickness for the solder pads and castellations on the “L” suffix (LCC)
package are 60 to 225 micro-inches thick of gold (Au) over 80 to 350
micro-inches thick of nickel (Ni) over a minimum of 5 micro-inches thickof moly-manganese or tungsten refractory material. The J-Lead package
top layer is 100 to 225 micro inches thick of 99.7% gold (Au) over 80 to 350
micro inches thick of electroplated nickel (Ni).

DIM
A
BC
DE
F
G

Inch.230.430.100.033.050.013.120mm
5.84
10.92
2.54
0.84
1.27
0.33
3.05
FGFEARecommended Solder Pad Pattern: The recommended solder pad size andshape for both the LCC and J-Lead packages is shown in the diagram andtable. These dimensions are recommendations only and may or may not
be optimum for your particular soldering process.

CDDo not use ultrasonic cleaners. Ultrasonic cleaning may breakinternal wire bonds and will void the warranty.

B

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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETERTEST REPORT EXAMPLES:
LINEARITY, PHASE & FREQUENCY RESPONSE BY G-LEVELThe optional 1521-TST test reports provide additional information about the linearity, output, phase, andfrequency response as tested for each individual unit. The following are examples of the graphical data
supplied on test reports, by G-level.
NOTE: Frequency response on test reports is documented by simulating frequency response with the DV
pin. This will indicate lower values than the actual performance once soldered or otherwise permanently
installed upon a board.

EXAMPLE 2G: 1521L-002

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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETER

EXAMPLE 5G: 1521L-005

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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETER

EXAMPLE 10G: 1521L-010

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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETER

EXAMPLE 25G: 1521L-025

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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETER

EXAMPLE 50G: 1521L-050

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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETER

EXAMPLE 100G: 1521L-100

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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETEREXAMPLE 200G: 1521L-200

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MODEL 1521 ANALOG SURFACE MOUNT ACCELEROMETER

EXAMPLE 400G: 1521L-400

COMPANION ACCESSORY
The Model EB-L and EB-J Analog Test Sets provide a convenient means of testing andevaluating SDI Model 1521 surface mount accelerometers in the LCC and JLCCpackage formats. The zero-insertion-force socket is pre-fitted to the board, which
includes set jumpers for advanced features of SDI accelerometers. A 10-pin connector
and ribbon cable provide connections to the user's test equipment. The EB-L and EBJ Sets and SDI Surface Mount Accelerometers are each sold separately.

SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
Silicon Designs, Inc. • 13905 NE 128th Street, Kirkland WA 98034 • Phone: 425-391-8329 • Fax: 425-391-0446
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