TI1 LDC1314RGHT Multi-channel 12-bit inductance to digital converter (ldc) for inductive sensing Datasheet

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LDC1312, LDC1314
SNOSCZ0 – DECEMBER 2014
LDC1312, LDC1314 Multi-Channel 12-Bit Inductance to Digital Converter (LDC) for
Inductive Sensing
1 Features
3 Description
•
•
•
The LDC1312 and LDC1314 are 2- and 4-channel,
12-bit inductance to digital converters (LDCs) for
inductive sensing solutions. With multiple channels
and support for remote sensing, the LDC1312 and
LDC1314 enable the performance and reliability
benefits of inductive sensing to be realized at minimal
cost and power. The products are easy to use, only
requiring that the sensor frequency be within 1 kHz
and 10 MHz to begin sensing. The wide 1 kHz to 10
MHz sensor frequency range also enables use of
very small PCB coils, further reducing sensing
solution cost and size.
1
•
•
•
•
•
•
•
Easy-to-use – minimal configuration required
Measure up to 4 sensors with one IC
Multiple channels support environmental and
aging compensation
Multi-channel remote sensing provides lowest
system cost
Pin-compatible medium and high-resolution
options
– LDC1312/4: 2/4-ch 12-bit LDC
– LDC1612/4: 2/4-ch 28-bit LDC
Supports wide sensor frequency range of 1kHz to
10MHz
Power consumption:
– 35 µA Low Power Sleep Mode
– 200 nA Shutdown Mode
3.3V operation
Support internal or external reference clock
Immune to DC magnetic fields and magnets
2 Applications
•
•
•
•
•
•
•
•
Knobs in consumer, appliances, and automotive
Linear and rotational encoders
Buttons in home electronics, wearables,
manufacturing, and automotive
Keypads in manufacturing and appliances
Slider buttons in consumer products
Metal detection in industrial and automotive
POS and EPOS
Flow meters in consumer and appliances
The LDC1312 and LDC1314 offer well-matched
channels, which allow for differential and ratiometric
measurements. This enables designers to use one
channel
to
compensate
their
sensing
for
environmental and aging conditions such as
temperature, humidity, and mechanical drift. Given
their ease of use, low power, and low system cost
these products enable designers to greatly improve
on existing sensing solutions and to introduce brand
new sensing capabilities to products in all markets,
especially consumer and industrial applications.
Inductive sensing offers better performance,
reliability, and flexibility than competitive sensing
technologies at lower system cost and power.
The LDC1312 and LDC1314 are easily configured via
an I2C interface. The two-channel LDC1312 is
available in a WSON-12 package and the fourchannel LDC1314 is available in a WQFN-16
package.
Device Information(1)
PART NUMBER
PACKAGE
BODY SIZE (NOM)
LDC1312
WSON-12
4 mm × 4 mm
LDC1314
WQFN-16
4 mm × 4 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Simplified Schematic
3.3 V
2.5
MCU
CLKIN
VDD
SD
GPIO
INTB
GPIO
IN0A
Target
IN0B
Sensor 0
Core
GND
IN1A
Target
IN1B
SDA
I2C
GND
I 2C
Peripheral
SCL
ADDR
Sensor 1
2.25
VDD
3.3 V
Measurement Precision (µm)
40 MHz
Measurement Precision vs. Target Distance
3.3 V
LDC1312
2
1.75
1.5
1.25
1
0.75
0.5
0.25
0
0
10%
20%
30%
40%
50%
60%
Sensing Range (Target Distance / ‡SENSOR)
70%
D001
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LDC1312, LDC1314
SNOSCZ0 – DECEMBER 2014
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Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
6.6
6.7
4
4
4
4
5
6
7
Absolute Maximum Ratings ......................................
ESD Ratings ............................................................
Recommended Operating Conditions.......................
Thermal Information .................................................
Electrical Characteristics...........................................
Switching Characteristics - I2C .................................
Typical Characteristics ..............................................
7.5 Programming........................................................... 18
7.6 Register Maps ......................................................... 18
8
8.1 Application Information............................................ 36
8.2 Typical Application ................................................. 39
9 Power Supply Recommendations...................... 43
10 Layout................................................................... 43
10.1 Layout Guidelines ................................................. 43
10.2 Layout Example .................................................... 43
11 Device and Documentation Support ................. 48
11.1
11.2
11.3
11.4
11.5
11.6
Detailed Description .............................................. 9
7.1
7.2
7.3
7.4
Application and Implementation ........................ 36
Overview ................................................................... 9
Functional Block Diagram ......................................... 9
Feature Description................................................... 9
Device Functional Modes........................................ 17
Device Support......................................................
Documentation Support ........................................
Related Links ........................................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
48
48
48
48
48
48
12 Mechanical, Packaging, and Orderable
Information ........................................................... 48
4 Revision History
2
DATE
REVISION
NOTES
December 2014
*
Initial release.
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5 Pin Configuration and Functions
CLKIN
3
10
ADDR
4
INTB
SD
IN3A
IN2B
IN2A
15
14
13
IN1B
11
IN1A
3
10
IN0B
4
9
IN0A
1
IN0B
SDA
2
9
IN0A
CLKIN
5
8
GND
ADDR
6
7
VDD
DAP
IN3B
12
SCL
DAP
8
IN1A
GND
11
7
2
VDD
SDA
6
IN1B
SD
12
5
1
INTB
SCL
16
Top View
LDC1314 WQFN-16
LDC1312 WSON-12
Pin Functions
PIN
NAME
NO.
TYPE (1)
DESCRIPTION
SCL
1
I
SDA
2
I/O
CLKIN
3
I
Master Clock input. Tie this pin to GND if internal oscillator is selected
4
I
I2C Address selection pin: when ADDR=L, I2C address = 0x2A, when ADDR=H, I2C address =
0x2B.
INTB
5
O
Configurable Interrupt output pin
SD
6
I
Shutdown input
VDD
7
P
Power Supply
GND
8
G
Ground
IN0A
9
A
External LC sensor 0 connection
IN0B
10
A
External LC sensor 0 connection
IN1A
11
A
External LC sensor 1 connection
IN1B
12
A
External LC sensor 1 connection
IN2A
13
A
External LC sensor 2 connection (LDC1314 only)
IN2B
14
A
External LC sensor 2 connection (LDC1314 only)
IN3A
15
A
External LC sensor 3 connection (LDC1314 only)
16
A
External LC sensor 3 connection (LDC1314 only)
DAP
N/A
ADDR
IN3B
DAP (2)
(1)
(2)
I2C Clock input
I2C Data input/output
Connect to Ground
I = Input, O = Output, P=Power, G=Ground, A=Analog
There is an internal electrical connection between the exposed Die Attach Pad (DAP) and the GND pin of the device. Although the DAP
can be left floating, for best performance the DAP should be connected to the same potential as the device's GND pin. Do not use the
DAP as the primary ground for the device. The device GND pin must always be connected to ground.
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6 Specifications
6.1 Absolute Maximum Ratings
MIN
MAX
UNIT
5
V
VDD
Supply Voltage Range
Vi
Voltage on any pin
-0.3
VDD+0.3
V
IA
Input current on any INx pin
-8
8
mA
ID
Input current on any Digital pin
-5
5
mA
Tj
Junction Temperature
-55
150
°C
Tstg
Storage temperature range
-65
150
°C
(1)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
6.2 ESD Ratings
VALUE
UNIT
LDC1312 in WSON-12 package
V(ESD)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±1000
Charged-device model (CDM), per JEDEC specification JESD22C101 (2)
±250
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±1000
Charged-device model (CDM), per JEDEC specification JESD22C101 (2)
±250
V
LDC1314 in QFN-16 package
V(ESD)
(1)
(2)
Electrostatic discharge
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
Unless otherwise specified, all limits ensured for TA = 25°C, VDD = 3.3 V
MIN
NOM
MAX
UNIT
VDD
Supply Voltage
2.7
3.6
V
TA
Operating Temperature
-40
125
°C
6.4 Thermal Information
LDC1312
THERMAL METRIC (1)
RθJA
(1)
4
Junction-to-ambient thermal resistance
LDC1314
WSON
WQFN
12 PINS
16 PINS
50
38
UNIT
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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6.5 Electrical Characteristics (1)
Unless otherwise specified, all limits ensured for TA = 25°C, VDD = 3.3 V
PARAMETER
TEST CONDITIONS (2)
MIN (3)
TYP (4)
MAX (3)
VDD
Supply Voltage
TA = -40°C to +125°C
IDD
Supply Current (not including
sensor current) (5)
CLKIN = 10MHz
IDDSL
Sleep Mode Supply Current (5)
35
60
µA
ISD
Shutdown Mode Supply
Current (5)
0.2
1
µA
UNIT
POWER
2.7
3.6
V
(6)
2.1
mA
SENSOR
ISENSORMAX
Sensor Maximum Current drive
RP
Sensor RP
IHDSENSORMAX
High current sensor drive mode:
Sensor Maximum Current
RP_HD_MIN
Minimum sensor RP
fSENSOR
Sensor Resonance Frequency
VSENSORMAX
Maximum oscillation amplitude
(peak)
NBITS
Number of bits
HIGH_CURRENT_DRV = b0
DRIVE_CURRENT_CHx = 0xF800
1.5
1
HIGH_CURRENT_DRV = b1
DRIVE_CURRENT_CH0 = 0xF800
Channel 0 only
TA = -40°C to +125°C
CIN
Sensor Pin input capacitance
mA
Ω
250
0.001
10
MHz
1.8
V
12
RCOUNT ≥ 0x0400
Maximum Channel Sample Rate
kΩ
6
RESET_DEV.OUTPUT_GAIN=b00
fCS
mA
100
single active channel continuous
conversion, SCL=400kHz
13.3
bits
kSPS
4
pF
MASTER CLOCK
fCLKIN
External Master Clock Input
Frequency (CLKIN)
TA = -40°C to +125°C
CLKINDUTY_MIN
External Master Clock minimum
acceptable duty cycle (CLKIN)
40%
CLKINDUTY_MAX
External Master Clock maximum
acceptable duty cycle (CLKIN)
60%
VCLKIN_LO
CLKIN low voltage threshold
VCLKIN_HI
CLKIN high voltage threshold
fINTCLK
Internal Master Clock Frequency
range
TCf_int_μ
Internal Master Clock
Temperature Coefficient mean
2
40
MHz
0.3*VDD
V
0.7*VD
D
35
V
43.4
55
-13
MHz
ppm/°C
TIMING CHARACTERISTICS
tWAKEUP
(1)
(2)
(3)
(4)
(5)
(6)
Wake-up Time from SD high-low
transition to I2C readback
2
ms
Electrical Characteristics Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions
result in very limited self-heating of the device such that TJ = TA. No guarantee of parametric performance is indicated in the electrical
tables under conditions of internal self-heating where TJ > TA. Absolute Maximum Ratings indicate junction temperature limits beyond
which the device may be permanently degraded, either mechanically or electrically.
Register values are represented as either binary (b is the prefix to the digits), or hexadecimal (0x is the prefix to the digits). Decimal
values have no prefix.
Limits are ensured by testing, design, or statistical analysis at 25°C. Limits over the operating temperature range are ensured through
correlations using statistical quality control (SQC) method.
Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary
over time and will also depend on the application and configuration. The typical values are not tested and are not guaranteed on
shipped production material.
I2C read/write communication and pull-up resistors current through SCL, SDA not included.
Sensor inductor: 2 layer, 32 turns/layer, 14mm diameter, PCB inductor with L=19.4µH, RP=5.7kΩ at 2MHz Sensor capacitor: 330pF 1%
COG/NP0 Target: Aluminum, 1.5mm thickness Channel = Channel 0 (continuous mode) CLKIN = 40MHz, CHx_FIN_DIVIDER = b0000,
CHx_FREF_DIVIDER = b00 0000 0001 CH0_RCOUNT = 0xFFFF, SETTLECOUNT_CH0 = 0x0100 RP_OVERRIDE = b1,
AUTO_AMP_DIS = b1, DRIVE_CURRENT_CH0 = 0x9800
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Electrical Characteristics(1) (continued)
Unless otherwise specified, all limits ensured for TA = 25°C, VDD = 3.3 V
TEST CONDITIONS (2)
PARAMETER
tWD-TIMEOUT
MIN (3)
TYP (4)
Sensor recovery time (after
watchdog timeout)
MAX (3)
5.2
UNIT
ms
6.6 Switching Characteristics - I2C
Unless otherwise specified, all limits ensured for TA = 25°C, VDD = 3.3 V
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VOLTAGE LEVELS
VIH
Input High Voltage
VIL
Input Low Voltage
0.7ˣVDD
VOL
Output Low Voltage (3mA sink
current)
HYS
Hysteresis
V
0.3ˣVDD
V
0.4
V
0.1ˣVDD
V
I2C TIMING CHARACTERISTICS
fSCL
Clock Frequency
10
tLOW
Clock Low Time
1.3
μs
tHIGH
Clock High Time
0.6
μs
tHD;STA
Hold Time (repeated) START
condition
0.6
μs
tSU;STA
Set-up time for a repeated START
condition
0.6
μs
tHD;DAT
Data hold time
0
μs
tSU;DAT
Data setup time
100
ns
tSU;STO
Set-up time for STOP condition
0.6
μs
tBUF
Bus free time between a STOP
and START condition
1.3
μs
tVD;DAT
Data valid time
0.9
μs
tVD;ACK
Data valid acknowledge time
0.9
μs
tSP
Pulse width of spikes that must be
suppressed by the input filter (1)
50
ns
(1)
After this period, the first clock
pulse is generated
400
kHz
This parameter is specified by design and/or characterization and is not tested in production.
SDA
tLOW
tf
tHD;STA
tr
tf
tr
tBUF
tSP
SCL
tSU;STA
tHD;STA
tHIGH
tHD;DAT
START
tSU;STO
tSU;DAT
REPEATED
START
STOP
START
Figure 1. I2C Timing
6
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6.7 Typical Characteristics
Common test conditions (unless specified otherwise): Sensor inductor: 2 layer, 32 turns/layer, 14mm diameter, PCB inductor
with L=19.4µH, RP=5.7kΩ at 2MHz; Sensor capacitor: 330pF 1% COG/NP0; Target: Aluminum, 1.5mm thickness; Channel =
Channel 0 (continuous mode); CLKIN = 40MHz, CHx_FIN_DIVIDER = 0x1, CHx_FREF_DIVIDER = 0x001 CH0_RCOUNT =
0xFFFF, SETTLECOUNT_CH0 = 0x0100, RP_OVERRIDE = 1, AUTO_AMP_DIS = 1, DRIVE_CURRENT_CH0 = 0x9800
3.25
3.25
IDD CH0 Current (mA)
3.225
3.2
IDD CH0 Current (mA)
VDD = 2.7 V
VDD = 3 V
VDD = 3.3 V
VDD = 3.6 V
3.175
3.15
3.125
3.1
3.2
3.15
3.1
-40°C
-20°C
0°C
25°C
3.075
3.05
-40
-20
0
20
40
60
Temperature (°C)
80
100
3.05
2.7
120
2.8
Includes 1.57 mA sensor coil current
-40°C to +125°C
Figure 2. Active Mode IDD vs. Temperature
3.3
3.4
3.5
3.6
D004
Figure 3. Active Mode IDD vs. VDD
VDD = 2.7 V
VDD = 3 V
VDD = 3.3 V
VDD = 3.6 V
-40°C
-20°C
60
0°C
25°C
50°C
85°C
100°C
125°C
55
45
40
35
50
45
40
35
30
25
-40
3.1
3.2
VDD (V)
65
Sleep Current (µA)
Sleep Current (µA)
50
3
Includes 1.57 mA sensor coil current
60
55
2.9
D003
50°C
85°C
100°C
125°C
30
-20
0
20
40
60
Temperature (°C)
80
100
25
2.7
120
2.8
2.9
3
D005
3.1
3.2
VDD (V)
3.3
3.4
3.5
3.6
D006
-40°C to +125°C
Figure 4. Sleep Mode IDD vs. Temperature
Figure 5. Sleep Mode IDD vs. VDD
1.4
1
0.8
0.6
0.4
0.2
0
-40
-40°C
-20°C
1.4
Shutdown Current (µA)
Shutdown Current (µA)
1.2
1.6
VDD = 2.7 V
VDD = 3 V
VDD = 3.3 V
VDD = 3.6 V
0°C
25°C
50°C
85°C
100°C
125°C
1.2
1
0.8
0.6
0.4
0.2
-20
0
20
40
60
Temperature (°C)
80
100
120
0
2.7
2.8
D007
2.9
3
3.1
3.2
VDD (V)
3.3
3.4
3.5
3.6
D008
-40°C to +125°C
Figure 6. Shutdown Mode IDD vs. Temperature
Figure 7. Shutdown Mode IDD vs. VDD
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Typical Characteristics (continued)
Common test conditions (unless specified otherwise): Sensor inductor: 2 layer, 32 turns/layer, 14mm diameter, PCB inductor
with L=19.4µH, RP=5.7kΩ at 2MHz; Sensor capacitor: 330pF 1% COG/NP0; Target: Aluminum, 1.5mm thickness; Channel =
Channel 0 (continuous mode); CLKIN = 40MHz, CHx_FIN_DIVIDER = 0x1, CHx_FREF_DIVIDER = 0x001 CH0_RCOUNT =
0xFFFF, SETTLECOUNT_CH0 = 0x0100, RP_OVERRIDE = 1, AUTO_AMP_DIS = 1, DRIVE_CURRENT_CH0 = 0x9800
43.41
43.4
VDD = 2.7 V
VDD = 3 V
VDD = 3.3 V
VDD = 3.6 V
43.38
43.37
43.36
43.35
43.34
43.33
43.32
-40
0°C
25°C
50°C
85°C
100°C
125°C
43.39
43.38
43.37
43.36
43.35
43.34
43.33
-20
0
20
40
60
Temperature (°C)
80
100
120
43.32
2.7
2.8
2.9
D009
-40°C to +125°C
3
3.1
3.2
VDD (V)
3.3
3.4
3.5
3.6
D010
Data based on 1 unit
Figure 8. Internal Oscillator Frequency vs. Temperature
8
-40°C
-20°C
43.4
Internal Oscillator (MHz)
Internal Oscillator (MHz)
43.39
Figure 9. Internal Oscillator Frequency vs. VDD
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7 Detailed Description
7.1 Overview
Conductive objects brought in contact with an AC electromagnetic (EM) field will induce field changes that can be
detected using a sensor such as an inductor. Conveniently, an inductor, along with a capacitor, can be used to
construct an L-C resonator, also known as an L-C tank, which can be used to produce an EM field. In the case of
an L-C tank, the effect of the field disturbance is an apparent shift in the inductance of the sensor, which can be
observed as a shift in the resonant frequency. Using this principle, the LDC1312/1314 is an inductance-to-digital
converter (LDC) that measures the oscillation frequency of an LC resonator. The device outputs a digital value
that is proportional to frequency. This frequency measurement can be converted to an equivalent inductance.
7.2 Functional Block Diagram
40 MHz
40 MHz
CLKIN
VDD
SD
INTB
fREF
IN0A
IN0B
Resonant
Circuit
Driver
IN1B
Resonant
Circuit
Driver
VDD
IN0A
Resonant
Circuit
Driver
Core
I2C
fIN
SDA
SCL
SD
INTB
fREF
IN0B
fIN
IN1A
CLKIN
IN3A
IN3B
Resonant
Circuit
Driver
Core
SDA
I2C
SCL
ADDR
ADDR
GND
GND
Figure 10. Block Diagrams for the LDC1312 (left) and LDC1314 (right)
The LDC1312/LDC1314 is composed of front-end resonant circuit drivers, followed by a multiplexer that
sequences through the active channels, connecting them to the core that measures and digitizes the sensor
frequency (fSENSOR). The core uses a reference frequency (fREF) to measure the sensor frequency. fREF is derived
from either an internal reference clock (oscillator), or an externally supplied clock. The digitized output for each
channel is proportional to the ratio of fSENSOR/fREF. The I2C interface is used to support device configuration and
to transmit the digitized frequency values to a host processor. The LDC can be placed in shutdown mode, saving
current, using the SD pin. The INTB pin may be configured to notify the host of changes in system status.
7.3 Feature Description
7.3.1 Clocking Architecture
Figure 11 shows the clock dividers and multiplexers of the LDC.
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Feature Description (continued)
IN0A
Sensor 0
÷m
fSENSOR0
fIN0
IN0B
CH0_FIN_DIVIDER (0x14)
IN1A
Sensor 1
÷m
fSENSOR1
fIN1
IN1B
tfINt
CH1_FIN_DIVIDER (0x15)
IN2A(1)
Sensor 2(1)
÷m
fSENSOR2(1)
IN2B
fIN2(1)
(1)
CH2_FIN_DIVIDER (0x16)(1)
IN3A(1)
Sensor 3(1)
fSENSOR3(1)
÷m
IN3B(1)
CONFIG (0x1A)
MUX_CONFIG
(0x1B)
CH3_FIN_DIVIDER (0x17)(1)
÷n
CLKIN
fIN3(1)
Core
Data
Output
fREF0
CH0_FREF_DIVIDER (0x14)
REF_CLK_SRC
(0x1A)
÷n
fREF1
tfCLKINt
tfCLKt
tfREFt
CH1_FREF_DIVIDER (0x15)
tfINTt
÷n
fREF2(1)
Int. Osc.
CH2_FREF_DIVIDER (0x16)(1)
÷n
fREF3(1)
CH3_FREF_DIVIDER (0x17)(1)
CONFIG (0x1A)
MUX_CONFIG
(0x1B)
Figure 11. Clocking Diagram
(1) LDC1314 only
In Figure 11, the key clocks are fIN, fREF, and fCLK. fCLK is selected from either the internal clock source or external
clock source (CLKIN) . The frequency measurement reference clock, fREF, is derived from the fCLK source. It is
recommended that precision applications use an external master clock that offers the stability and accuracy
requirements needed for the application. The internal oscillator may be used in applications that require low cost
and do not require high precision. The fINx clock is derived from sensor frequency for a channel x, fSENSORx. fREFx
and fINx must meet the requirements listed in Table 1, depending on whether fCLK (master clock) is the internal or
external clock.
Table 1. Clock Configuration Requirements
MODE (1)
Multi-Channel
Single-Channel
(1)
(2)
10
CLKIN SOURCE
VALID fREFx
RANGE (MHz)
Internal
fREFx < 55
External
fREFx < 40
Either external or
internal
fREFx < 35
VALID fINx
RANGE
< fREFx /4
SET
CHx_FIN_DIVIDE
R to
> b0001
(2)
SET
CHx_SETTLECO
UNT to
SET
CHx_RCOUNT to
>3
>8
Channels 2 and 3 are only available for LDC1314
If fSENSOR ≥ 8.75 MHz, then CHx_FIN_DIVIDER must be ≥ 2
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Table 2 shows the clock configuration registers for all channels.
Table 2. Clock Configuration Registers
CHANNEL
(1)
REGISTER
FIELD [ BIT(S) ]
VALUE
CONFIG, addr
0x1A
REF_CLK_SRC [9]
b0 = internal oscillator is used as the
master clock
b1 = external clock source is used as the
master clock
0
fREF0
CLOCK_DIVIDER
S_CH0, addr 0x14
CH0_FREF_DIVIDER [9:0]
fREF0 = fCLK / CH0_FREF_DIVIDER
1
fREF1
CLOCK_DIVIDER
S_CH1, addr 0x15
CH1_FREF_DIVIDER [9:0]
fREF1 = fCLK / CH1_FREF_DIVIDER
2
fREF2
CLOCK_DIVIDER
S_CH2, addr 0x16
CH2_FREF_DIVIDER [9:0]
fREF2 = fCLK / CH2_FREF_DIVIDER
3
fREF3
CLOCK_DIVIDER
S_CH3, addr 0x17
CH3_FREF_DIVIDER [9:0]
fREF3 = fCLK / CH3_FREF_DIVIDER
0
fIN0
CLOCK_DIVIDER
S_CH0, addr 0x14
CH0_FIN_DIVIDER [15:12]
fIN0 = fSENSOR0 / CH0_FIN_DIVIDER
1
fIN1
CLOCK_DIVIDER
S_CH1, addr 0x15
CH1_FIN_DIVIDER [15:12]
fIN1 = fSENSOR1 / CH1_FIN_DIVIDER
2
fIN2
CLOCK_DIVIDER
S_CH2, addr 0x16
CH2_FIN_DIVIDER [15:12]
fIN2 = fSENSOR2 / CH2_FIN_DIVIDER
3
fIN3
CLOCK_DIVIDER
S_CH3, addr 0x17
CH3_FIN_DIVIDER [15:12]
fIN3 = fSENSOR3 / CH3_FIN_DIVIDER
All
(1)
CLOCK
fCLK = Master
Clock Source
Channels 2 and 3 are only available for LDC1314
7.3.2 Multi-Channel and Single Channel Operation
The multi-channel package of the LDC enables the user to save board space and support flexible system design.
For example, temperature drift can often cause a shift in component values, resulting in a shift in resonant
frequency of the sensor. Using a 2nd sensor as a reference provides the capability to cancel out a temperature
shift. When operated in multi-channel mode, the LDC sequentially samples the active channels. In single channel
mode, the LDC samples a single channel, which is selectable. The following table shows the registers and values
that are used to configure either multi-channel or single channel modes.
Table 3. Single and Multi-Channel Configuration Registers
MODE
REGISTER
VALUE (1)
FIELD [ BIT(S) ]
00 = chan 0
CONFIG, addr 0x1A
ACTIVE_CHAN [15:14]
Single channel
01 = chan 1
10 = chan 2
11 = chan 3
MUX_CONFIG addr 0x1B
AUTOSCAN_EN [15]
0 = continuous conversion on a
single channel (default)
MUX_CONFIG addr 0x1B
AUTOSCAN_EN [15]
1 = continuous conversion on
multiple channels
MUX_CONFIG addr 0x1B
RR_SEQUENCE [14:13]
00 = Ch0, Ch 1
Multi-channel
01 = Ch0, Ch 1, Ch 2
10 = Ch0, CH1, Ch2, Ch3
(1)
Channels 2 and 3 are only available for LDC1314
The digitized sensor measurement for each channel (DATAx) represents the ratio of the sensor frequency to the
reference frequency. The data outputs represent the 12 MSBs of a 16-bit result:
DATAx/ 212 = fSENSORx/fREFx
(1)
The sensor frequency can be calculated from:
'$7$[ ¦REFx
¦ sensorx
212
(2)
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The following table illustrates the registers that contain the fixed point sample values for each channel.
Table 4. LDC1314/1312 Sample Data Registers
Channel
(1)
Register
Field name [bits(s) ]
Value
0
DATA_MSB_CH0, addr 0x00
DATA0 [11:0]
12 MSBs of the 12 bit result.
0x000 = under range
0xfff = over range
1
DATA_MSB_CH1, addr 0x02
DATA1 [11:0]
12 MSBs of the 12 bit result.
0x000 = under range
0xfff = over range
2
DATA_MSB_CH2, addr 0x04
DATA2 [11:0]
12 MSBs of the 12 bit result.
0x000 = under range
0xfff = over range
3
DATA_MSB_CH3, addr 0x06
DATA3 [11:0]
12 MSBs of the 12 bit result.
0x000 = under range
0xfff = over range
(1)
Channels 2 and 3 available for LDC1314 only.
When the LDC sequences through the channels in multi-channel mode, the dwell time interval for each channel
is the sum of 3 parts: sensor activation time + conversion time + channel switch delay.
The sensor activation time is the amount of settling time required for the sensor oscillation to stabilize, as shown
in Figure 12. The settling wait time is programmable and should be set to a value that is long enough to allow
stable oscillation. The settling wait time for channel x is given by:
tSx = (CHX_SETTLECOUNTˣ16)/fREFx
(3)
Table 5 illustrates the registers and values for configuring the settling time for each channel.
Channel 0
Sensor
Activation
Channel 0
Conversion
Channel
switch delay
Channel 1
Conversion
Channel 1
Sensor
Activation
Channel
switch delay
Channel 0
Sensor
Activation
Channel 0
Channel 1
Figure 12. Multi-channel Mode Sequencing
Active Channel
Sensor Signal
Sensor
Activation
Conversion
Conversion
Amplitude
Correction
Conversion
Amplitude
Correction
Amplitude
Correction
Figure 13. Single-channel Mode Sequencing
12
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Table 5. Settling Time Register Configuration
Register
Field
Conversion time (2)
0
SETTLECOUNT_CH0, addr 0x10
CH0_SETTLECOUNT (15:0)
(CH0_SETTLECOUNT*16)/fREF0
1
SETTLECOUNT_CH1, addr 0x11
CH1_SETTLECOUNT (15:0)
(CH1_SETTLECOUNT*16)/fREF1
2
SETTLECOUNT_CH2, addr 0x12
CH2_SETTLECOUNT (15:0)
(CH2_SETTLECOUNT*16)/fREF2
3
SETTLECOUNT_CH3, addr 0x13
CH3_SETTLECOUNT (15:0)
(CH3_SETTLECOUNT*16)/fREF3
Channel
(1)
(2)
(1)
Channels 2 and 3 are available only in the LDC1314.
fREFx is the reference frequency configured for the channel.
The SETTLECOUNT for any channel x must satisfy:
CHx_SETTLECOUNT ≥ QSENSORx × fREFx / (16 × fSENSORx)
where
•
•
•
Q
fSENSORx = Frequency of the Sensor on Channel x
fREFx = Reference frequency for Channel x
QSENSORx = Quality factor of the sensor on Channel x. Q is estimated by:
RP
(4)
C
L
(5)
Round the result to the next highest integer (for example, if Equation 4 recommends a minimum value of 6.08,
program the register to 7 or higher).
L, RP and C values can be obtained by using Texas Instrument’s WEBENCH® for the coil design.
The conversion time represents the number of reference clock cycles used to measure the sensor frequency. It is
set by the CHx_RCOUNT register for the channel. The conversion time for any channel x is:
tCx = (CHx_RCOUNT ˣ 16 + 4) /fREFx
(6)
The reference count value must be chosen to support the required number of effective bits (ENOB). For
example, if an ENOB of 13 bits is required, then a minimum conversion time of 213 = 8192 clock cycles is
required. 8192 clock cycles correspond to a CHx_RCOUNT value of 0x0200.
Table 6. Conversion Time Configuration Registers, Channels 0 - 3 (1)
CHANNEL
(1)
REGISTER
FIELD [ BIT(S) ]
CONVERSION TIME
0
RCOUNT_CH0, addr 0x08
CH0_RCOUNT (15:0)
(CH0_RCOUNT*16)/fREF0
1
RCOUNT_CH1, addr 0x09
CH1_RCOUNT (15:0)
(CH1_RCOUNT*16)/fREF1
2
RCOUNT_CH2, addr 0x0A
CH2_RCOUNT (15:0)
(CH2_RCOUNT*16)/fREF2
3
RCOUNT_CH3, addr 0x0B
CH3_RCOUNT (15:0)
(CH3_RCOUNT*16)/fREF3
Channels 2 and 3 are available only for LDC1314.
The typical channel switch delay time between the end of conversion and the beginning of sensor activation of
the subsequent channel is:
Channel Switch Delay = 692 ns + 5 / fref
(7)
The deterministic conversion time of the LDC allows data polling at a fixed interval. A data ready flag (DRDY) is
also available for interrupt driven system designs (see the STATUS register description in Register Maps).
An offset value may be subtracted from each DATA value to compensate for a frequency offset or maximize the
dynamic range of the sample data. The offset values should be < fSENSORx_MIN / fREFx. Otherwise, the offset might
be so large that it masks the LSBs which are changing.
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Table 7. Frequency Offset Registers
CHANNEL
REGISTER
(1)
(1)
FIELD [ BIT(S) ]
VALUE
0
OFFSET_CH0, addr 0x0C
CH0_OFFSET [ 15:0 ]
fOFFSET0 = CH0_OFFSET * (fREF0/216)
1
OFFSET_CH1, addr 0x0D
CH1_OFFSET [ 15:0 ]
fOFFSET1 = CH1_OFFSET * (fREF1/216)
2
OFFSET_CH2, addr 0x0E
CH2_OFFSET [ 15:0 ]
fOFFSET2 = CH2_OFFSET * (fREF2/216)
3
OFFSET_CH3, addr 0x0F
CH3_OFFSET [ 15:0 ]
fOFFSET3 = CH3_OFFSET * (fREF3/216)
Channels 2 and 3 are only available for LDC1314
Internally, the LDC measures with 16bits of resolution, while the conversion output word width is only 12bits. For
systems in which the sensor signal variation is less than 25% of the full scale range, the LDC can report
conversion results with higher resolution by setting the Output Gain. The Output Gain is applied to all device
channels. An output gain can be used to apply a 2-bit, 3-bit, or 4-bit shift to the output code for all channels,
allowing access to the 4LSBs of the original 16-bit result. The MSBs of the sample are shifted out when a gain is
applied. Do not use the output gain if the MSBs of any active channel are toggling, as the MSBs for that channel
will be lost when gain is applied.
Table 8. Output Gain Register
CHANNEL
(1)
All
(1)
REGISTER
FIELD [ BIT(S) ]
RESET_DEV, addr
0x1C
EFFECTIVE
RESOLUTION (BITS)
VALUES
OUTPUT RANGE
OUTPUT_GAIN [ 10:9 ] 00 (default): Gain =1 (0
bits shift)
12
100% full scale
01: Gain = 4 (2 bits left
shift)
14
25% full scale
10: Gain = 8 (3 bits left
shift)
15
12.5% full scale
11 : Gain = 16 (4 bits left
shift)
16
6.25% full scale
Channels 2 and 3 are available for LDC1314 only.
Example: If the conversion result for a channel is 0x07A3, with OUTPUT_GAIN=0x0, the reported output code is
0x07A. If OUTPUT_GAIN is set to 0x3 in the same condition, then the reported output code is 0x7A3. The
original 4 MSBs (0x0) are no longer accessible. Figure 14 illustrates the segments of the 16-bit sample that is
reported for each possible gain setting.
MSB
Conversion result
LSB
15
12
Output_gain = 0x3
8
7
4
3
0
11
Output_gain = 0x2
0
11
Output_gain = 0x1
Output_gain = 0x0
(default)
11
0
11
0
11
11
0
0
Data available in DATA_MSB_CHx.DATA_CHx [11:0]
Figure 14. Conversion Data Output Gain
14
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The sensor frequency can be determined by:
¦SENSORx
DATAx
CHx_OFFSET ·
§
&+[B),1B',9,'(5 ¦REFx ¨ (12OUTPUT_GAIN) ¸
216
©2
¹
where
•
•
•
DATAx = Conversion result from the DATA_CHx register
CHx_OFFSET = Offset value set in the OFFSET_CHx register
OUTPUT_GAIN = output multiplication factor set in the RESET_DEVICE.OUTPUT_GAIN register
(8)
7.3.3 Current Drive Control Registers
The registers listed in Table 9 are used to control the sensor drive current. The recommendations listed in the
last column of the table should be followed.
Auto-calibration mode is used to determine the optimal sensor drive current for a fixed sensor design. This mode
should only be used during system prototyping.
The auto-amplitude correction attempts to maintain the sensor oscillation amplitude between 1.2V and 1.8V by
adjusting the sensor drive current between conversions. When auto-amplitude correction is enabled, the output
data may show non-monotonic behavior due to an adjustment in drive current. Auto-amplitude correction is only
recommended for low-precision applications.
A high sensor current drive mode can be enabled to drive sensor coils with > 1.5mA on channel 0, only in single
channel mode. This feature can be used when the sensor RP is lower than 1kΩ. Set the HIGH_CURRENT_DRV
register bit to b1 to enable this mode.
Table 9. Current Drive Control Registers
CHANNEL
(1)
REGISTER
CONFIG, addr 0x1A
All
CONFIG, addr 0x1A
FIELD [ BIT(S) ]
SENSOR_ACTIVATE_SEL [11]
Sets current drive for sensor activation.
Recommended value is b0 (Full Current
mode).
RP_OVERRIDE_EN [12]
Set to b1 for normal operation (RP over
ride enabled)
AUTO_AMP_DIS [10]
Disables Automatic amplitude correction.
Set to b1 for normal operation (disabled)
HIGH_CURRENT_DRV [6]
b0 = normal current drive (1.5 mA)
b1 = Increased current drive (> 1.5 mA)
for Ch 0 in single channel mode only.
Cannot be used in multi-channel mode.
0
DRIVE_CURRENT_CH0, addr 0x1E CH0_IDRIVE [15:11]
0
CH0_INIT_IDRIVE [10:6]
DRIVE_CURRENT_CH1, addr 0x1F CH1_IDRIVE [15:11]
1
CH1_INIT_IDRIVE [10:6]
DRIVE_CURRENT_CH2, addr 0x20 CH2_IDRIVE [15:11]
2
CH2_INIT_IDRIVE [10:6]
(1)
VALUE
Drive current used during the settling and
conversion time for Ch. 0 (auto-amplitude
correction must be disabled and RP over
ride=1 )
Initial drive current stored during autocalibration. Not used for normal operation.
Drive current used during the settling and
conversion time for Ch. 1 (auto-amplitude
correction must be disabled and RP over
ride=1 )
Initial drive current stored during autocalibration. Not used for normal operation.
Drive current used during the settling and
conversion time for Ch. 2 (auto-amplitude
correction must be disabled and RP over
ride=1 )
Initial drive current stored during autocalibration. Not used for normal operation.
Channels 2 and 3 are available for LDC1314 only.
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Table 9. Current Drive Control Registers (continued)
CHANNEL
(1)
REGISTER
FIELD [ BIT(S) ]
VALUE
DRIVE_CURRENT_CH3, addr 0x21 CH3_IDRIVE [15:11]
Drive current used during the settling and
conversion time for Ch. 3 (auto-amplitude
correction must be disabled and RP over
ride=1 )
3
CH3_INIT_IDRIVE [10:6]
Initial drive current stored during autocalibration. Not used for normal operation.
If the RP value of the sensor attached to channel x is known, Figure 15 can be used to select the 5-bit value to
be programmed into the IDRIVE field for the channel. Find the known RP value on the vertical axis, and then
read the corresponding decimal value on the horizontal axis. Program the hexadecimal equivalent of the x-axis
value into the IDRIVE field. Note that IDRIVE = b00000 corresponds to 16 µA, and IDRIVE = b11111
corresponds to 1563 µA.
100000
90000
80000
Rp (:)
70000
60000
50000
40000
30000
20000
10000
0
0
4
8
12
16
20
24
IDRIVE Field Value (decimal)
28
32
D023
Figure 15. IDRIVE vs Rp
7.3.4 Device Status Registers
The registers listed in Table 10 may be used to read device status.
Table 10. Status Registers
CHANNEL
(1)
(1)
REGISTER
FIELDS [ BIT(S) ]
VALUES
All
STATUS, addr 0x18
Refer to Register Maps section
12 fields are available that
for a description of the individual
contain various status bits [ 15:0 ]
status bits.
All
ERROR_CONFIG, addr 0x19
12 fields are available that are
Refer to Register Maps section
used to configure error reporting [ for a description of the individual
15:0 ]
error configuration bits.
Channels 2 and 3 are available for LDC1314 only.
See the STATUS and ERROR_CONFIG register description in the Register Map section. These registers can be
configured to trigger an interrupt on the INTB pin for certain events. The following conditions must be met:
1. The error or status register must be unmasked by enabling the appropriate register bit in the
ERROR_CONFIG register
2. The INTB function must be enabled by setting CONFIG.INTB_DIS to 0
When a bit field in the STATUS register is set, the entire STATUS register content is held until read or until the
DATA_CHx register is read. Reading also de-asserts INTB.
Interrupts are cleared by one of the following events:
1. Entering Sleep Mode
2. Power-on reset (POR)
3. Device enters Shutdown Mode (SD is asserted)
16
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4. S/W reset
5. I2C read of the STATUS register: Reading the STATUS register will clear any error status bit set in STATUS
along with the ERR_CHAN field and de-assert INTB
Setting register CONFIG.INTB_DIS to b1 disables the INTB function and holds the INTB pin high.
7.3.5 Input Deglitch Filter
The input deglitch filter suppresses EMI and ringing above the sensor frequency. It does not impact the
conversion result as long as its bandwidth is configured to be above the maximum sensor frequency. The input
deglitch filter can be configured in MUX_CONFIG.DEGLITCH register field as shown in Table 11. For optimal
performance, it is recommended to select the lowest setting that exceeds the sensor oscillation frequency. For
example, if the maximum sensor frequency is 2.0 MHz, choose MUX_CONFIG.DEGLITCH = b100 (3.3 MHz).
Table 11. Input deglitch filter register
CHANNEL
(1)
(1)
MUX_CONFIG.DEGLITCH REGISTER VALUE
DEGLITCH FREQEUNCY
ALL
001
1 MHz
ALL
100
3.3 MHz
ALL
101
10 MHz
ALL
011
33 MHz
Channels 2 and 3 are available for LDC1314 only.
7.4 Device Functional Modes
7.4.1 Startup Mode
When the LDC powers up, it enters into Sleep Mode and will wait for configuration. Once the device is
configured, exit Sleep Mode by setting CONFIG.SLEEP_MODE_EN to b0.
It is recommended to configure the LDC while in Sleep Mode. If a setting on the LDC needs to be changed,
return the device to Sleep Mode, change the appropriate register, and then exit Sleep Mode.
7.4.2 Normal (Conversion) Mode
When operating in the normal (conversion) mode, the LDC is periodically sampling the frequency of the sensor(s)
and generating sample outputs for the active channel(s).
7.4.3 Sleep Mode
Sleep Mode is entered by setting the CONFIG.SLEEP_MODE_EN register field to 1. While in this mode, the
register contents are maintained. To exit Sleep Mode, set the CONFIG.SLEEP_MODE_EN register field to 0.
After setting CONFIG.SLEEP_MODE_EN to b0, sensor activation for the first conversion will begin after 16,384
fINT clock cycles. While in Sleep Mode the I2C interface is functional so that register reads and writes can be
performed. While in Sleep Mode, no conversions are performed. In addition, entering Sleep Mode will clear any
error condition and de-assert the INTB pin.
7.4.4 Shutdown Mode
When the SD pin is set to high, the LDC will enter Shutdown Mode. Shutdown Mode is the lowest power state.
To exit Shutdown Mode, set the SD pin to low. Entering Shutdown Mode will return all registers to their default
state.
While in Shutdown Mode, no conversions are performed. In addition, entering Shutdown Mode will clear any
error condition and de-assert the INTB pin. While the device is in Shutdown Mode, is not possible to read to or
write from the device via the I2C interface.
7.4.4.1 Reset
The LDC can be reset by writing to RESET_DEV.RESET_DEV. Conversion will stop and all register values will
return to their default value. This register bit will always return 0b when read.
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7.5 Programming
The LDC device uses an I2C interface to access control and data registers.
7.5.1 I2C Interface Specifications
The LDC uses an extended start sequence with I2C for register access. The maximum speed of the I2C interface
is 400kbit/s. This sequence follows the standard I2C 7bit slave address followed by an 8bit pointer register byte
to set the register address. When the ADDR pin is set low, the LDC I2C address is 0x2A; when the ADDR pin is
set high, the LDC I2C address is 0x2B. The ADDR pin must not change state after the LDC exits Shutdown
Mode.
1
9
1
9
SCL
A6
SDA
A5
A4
A3
A2
A1
A0 R/W
Start by
Master
R7
R6
R5
Ack by
Slave
Frame 1
Serial Bus Address Byte
from Master
1
9
R4
R3
R2
R1
R0
Ack by
Slave
Frame 2
Slave Register
Address
1
9
SCL
D15 D14 D13 D12 D11 D10 D9
SDA
D8
D7
D6
D5
Ack by
Slave
Frame 3
Data MSB from
Master
D4
D3
D2
D1
D0
Ack by
Slave
Frame 4
Data LSB from
Master
Stop by
Master
Figure 16. I2C Write Register Sequence
1
9
1
9
SCL
A6
SDA
A5
A4
A3
A2
A1
A0 R/W
Start by
Master
R7
R6
Ack by
Slave
Frame 1
Serial Bus Address Byte
from Master
1
R5
R4
R3
R2
R1
R0
Ack by
Slave
Frame 2
Slave Register
Address
1
9
9
1
9
SCL
A6
SDA
A5
A4
A3
A2
A1
A0 R/W
Start by
Master
D15 D14 D13 D12 D11 D10 D9
Ack by
Slave
Frame 4
Data MSB from
Slave
Frame 3
Serial Bus Address Byte
from Master
D8
D7
D6
Ack by
Master
D5
D4
D3
D2
Frame 5
Data LSB from
Slave
D1
D0
Nack by Stop by
Master Master
Figure 17. I2C Read Register Sequence
7.6 Register Maps
7.6.1 Register List
Fields indicated with Reserved must be written only with indicated values. Improper device operation may occur
otherwise. The R/W column indicates the Read-Write status of the corresponding field. A ‘R/W’ entry indicates
read and write capability, a ‘R’ indicates read-only, and a ‘W’ indicates write-only.
Figure 18. Register List
ADDRESS
NAME
0x00
DATA_CH0
0x02
DATA_CH1
0x04
DATA_CH2
18
DEFAULT VALUE
0x0000
0x0000
0x0000
DESCRIPTION
Channel 0 Conversion Result and Error Status
Channel 1 Conversion Result and Error Status
Channel 2 Conversion Result and Error Status (LDC1314 only)
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ADDRESS
0x06
0x08
0x09
0x0A
0x0B
0x0C
0x0D
0x0E
0x0F
0x10
0x11
0x12
0x13
0x14
0x15
0x16
0x17
0x18
0x19
0x1A
0x1B
0x1C
0x1E
0x1F
0x20
0x21
0x7E
0x7F
SNOSCZ0 – DECEMBER 2014
NAME
DATA_CH3
RCOUNT_CH0
RCOUNT_CH1
RCOUNT_CH2
RCOUNT_CH3
OFFSET_CH0
OFFSET_CH1
OFFSET_CH2
OFFSET_CH3
SETTLECOUNT_CH0
SETTLECOUNT_CH1
SETTLECOUNT_CH2
SETTLECOUNT_CH3
CLOCK_DIVIDERS_C
H0
CLOCK_DIVIDERS_C
H1
CLOCK_DIVIDERS_C
H2
CLOCK_DIVIDERS_C
H3
STATUS
ERROR_CONFIG
CONFIG
MUX_CONFIG
RESET_DEV
DRIVE_CURRENT_CH
0
DRIVE_CURRENT_CH
1
DRIVE_CURRENT_CH
2
DRIVE_CURRENT_CH
3
MANUFACTURER_ID
DEVICE_ID
DEFAULT VALUE
0x0000
0x0080
0x0080
0x0080
0x0080
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
0x0000
DESCRIPTION
Channel 3 Conversion Result and Error Status (LDC1314 only)
Reference Count setting for Channel 0
Reference Count setting for Channel 1
Reference Count setting for Channel 2. (LDC1314 only)
Reference Count setting for Channel 3.(LDC1314 only)
Offset value for Channel 0
Offset value for Channel 1
Offset value for Channel 2 (LDC1314 only)
Offset value for Channel 3 (LDC1314 only)
Channel 0 Settling Reference Count
Channel 1 Settling Reference Count
Channel 2 Settling Reference Count (LDC1314 only)
Channel 3 Settling Reference Count (LDC1314 only)
Reference and Sensor Divider settings for Channel 0
0x0000
Reference and Sensor Divider settings for Channel 1
0x0000
Reference and Sensor Divider settings for Channel 2 (LDC1314 only)
0x0000
Reference and Sensor Divider settings for Channel 3 (LDC1314 only)
0x0000
0x0000
0x2801
0x020F
0x0000
0x0000
Device Status Report
Error Reporting Configuration
Conversion Configuration
Channel Multiplexing Configuration
Reset Device
Channel 0 sensor current drive configuration
0x0000
Channel 1 sensor current drive configuration
0x0000
Channel 2 sensor current drive configuration (LDC1314 only)
0x0000
Channel 3 sensor current drive configuration (LDC1314 only)
0x5449
0x3054
Manufacturer ID
Device ID
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7.6.2 Address 0x00, DATA_CH0
Figure 19. Address 0x00, DATA_CH0
15
CH0_ERR_UR
14
CH0_ERR_OR
13
CH0_ERR_WD
12
CH0_ERR_AE
11
7
6
5
4
3
10
9
8
1
0
DATA0[11:0]
2
DATA0[11:0]
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 12. Address 0x00, DATA_CH0 Field Descriptions
Bit
Field
Type
Reset
Description
15
CH0_ERR_UR
R
0
Channel 0 Conversion Under-range Error Flag. Cleared by
reading the bit.
14
CH0_ERR_OR
R
0
Channel 0 Conversion Over-range Error Flag. Cleared by
reading the bit.
13
CH0_ERR_WD
R
0
Channel 0 Conversion Watchdog Timeout Error Flag. Cleared by
reading the bit.
12
CH0_ERR_AE
R
0
Channel 0 Conversion Watchdog Timeout Error Flag. Cleared by
reading the bit.
DATA0[11:0]
R
0000 0000 Channel 0 Conversion Result
0000
11:0
7.6.3 Address 0x02, DATA_CH1
Figure 20. Address 0x02, DATA_CH1
15
CH1_ERR_UR
14
CH1_ERR_OR
13
CH1_ERR_WD
12
CH1_ERR_AE
11
7
6
5
4
3
10
9
8
1
0
DATA1[11:0]
2
DATA1[11:0]
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 13. Address 0x02, DATA_CH1 Field Descriptions
Bit
Field
Type
Reset
Description
15
CH1_ERR_UR
R
0
Channel 1 Conversion Under-range Error Flag. Cleared by
reading the bit.
14
CH1_ERR_OR
R
0
Channel 1 Conversion Over-range Error Flag. Cleared by
reading the bit.
13
CH1_ERR_WD
R
0
Channel 1 Conversion Watchdog Timeout Error Flag. Cleared by
reading the bit.
12
CH1_ERR_AE
R
0
Channel 1 Conversion Watchdog Timeout Error Flag. Cleared by
reading the bit.
DATA1[11:0]
R
0000 0000 Channel 1 Conversion Result
0000
11:0
20
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7.6.4 Address 0x04, DATA_CH2 (LDC1314 only)
Figure 21. Address 0x04, DATA_CH2
15
CH2_ERR_UR
14
CH2_ERR_OR
13
CH2_ERR_WD
12
CH2_ERR_AE
11
7
6
5
4
3
10
9
8
1
0
DATA2[11:0]
2
DATA2[11:0]
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 14. Address 0x04, DATA_CH2 Field Descriptions
Bit
Field
Type
Reset
Description
15
CH2_ERR_UR
R
0
Channel 2 Conversion Under-range Error Flag. Cleared by
reading the bit.
14
CH2_ERR_OR
R
0
Channel 2 Conversion Over-range Error Flag. Cleared by
reading the bit.
13
CH2_ERR_WD
R
0
Channel 2 Conversion Watchdog Timeout Error Flag. Cleared by
reading the bit.
12
CH2_ERR_AE
R
0
Channel 2 Conversion Watchdog Timeout Error Flag. Cleared by
reading the bit.
DATA2[11:0]
R
0000 0000 Channel 2 Conversion Result
0000
11:0
7.6.5 Address 0x06, DATA_CH3 (LDC1314 only)
Figure 22. Address 0x06, DATA_CH3
15
CH3_ERR_UR
14
CH3_ERR_OR
13
CH3_ERR_WD
12
CH3_ERR_AE
11
7
6
5
4
3
10
9
8
1
0
DATA3[11:0]
2
DATA3[11:0]
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 15. Address 0x06, DATA_CH3 Field Descriptions
Bit
Field
Type
Reset
Description
15
CH3_ERR_UR
R
0
Channel 3 Conversion Under-range Error Flag. Cleared by
reading the bit.
14
CH3_ERR_OR
R
0
Channel 3 Conversion Over-range Error Flag. Cleared by
reading the bit.
13
CH3_ERR_WD
R
0
Channel 3 Conversion Watchdog Timeout Error Flag. Cleared by
reading the bit.
12
CH3_ERR_AE
R
0
Channel 3 Conversion Watchdog Timeout Error Flag. Cleared by
reading the bit.
DATA3[11:0]
R
0000 0000 Channel 3 Conversion Result
0000
11:0
7.6.6 Address 0x08, RCOUNT_CH0
Figure 23. Address 0x08, RCOUNT_CH0
15
14
13
12
11
CH0_RCOUNT
10
9
8
7
6
5
4
2
1
0
3
CH0_RCOUNT
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
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Table 16. Address 0x08, RCOUNT_CH0 Field Descriptions
Bit
15:0
Field
Type
Reset
Description
CH0_RCOUNT
R/W
0000 0000
1000 0000
Channel 0 Reference Count Conversion Interval Time
0x0000-0x0004: Reserved
0x0005-0xFFFF: Conversion Time (tC0) =
(CH0_RCOUNTˣ16)/fREF0
7.6.7 Address 0x09, RCOUNT_CH1
Figure 24. Address 0x09, RCOUNT_CH1
15
14
13
12
11
CH1_RCOUNT
10
9
8
7
6
5
4
2
1
0
3
CH1_RCOUNT
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 17. Address 0x09, RCOUNT_CH1 Field Descriptions
Bit
15:0
Field
Type
Reset
Description
CH1_RCOUNT
R/W
0000 0000
1000 0000
Channel 1 Reference Count Conversion Interval Time
0x0000-0x0004: Reserved
0x0005-0xFFFF: Conversion Time (tC1)=
(CH1_RCOUNTˣ16)/fREF1
7.6.8 Address 0x0A, RCOUNT_CH2 (LDC1314 only)
Figure 25. Address 0x0A, RCOUNT_CH2
15
14
13
12
11
CH2_RCOUNT
10
9
8
7
6
5
4
2
1
0
3
CH2_RCOUNT
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 18. Address 0x0A, RCOUNT_CH2 Field Descriptions
Bit
15:0
Field
Type
Reset
Description
CH2_RCOUNT
R/W
0000 0000
1000 0000
Channel 2 Reference Count Conversion Interval Time
0x0000-0x0004: Reserved
0x0005-0xFFFF: Conversion Time (tC2)=
(CH2_RCOUNTˣ16)/fREF2
7.6.9 Address 0x0B, RCOUNT_CH3 (LDC1314 only)
Figure 26. Address 0x0B, RCOUNT_CH3
15
14
13
12
11
CH3_RCOUNT
10
9
8
7
6
5
4
2
1
0
3
CH3_RCOUNT
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
22
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Table 19. Address 0x0B, RCOUNT_CH3 Field Descriptions
Bit
15:0
Field
Type
Reset
Description
CH3_RCOUNT
R/W
0000 0000
1000 0000
Channel 3 Reference Count Conversion Interval Time
0x0000-0x0004: Reserved
0x0005-0xFFFF: Conversion Time (tC3)=
(CH3_RCOUNTˣ16)/fREF3
7.6.10 Address 0x0C, OFFSET_CH0
Figure 27. Address 0x0C, CH0_OFFSET
15
14
13
12
11
10
9
8
3
2
1
0
CH0_OFFSET
7
6
5
4
CH0_OFFSET
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 20. CH0_OFFSET Field Descriptions
Bit
15:0
Field
Type
Reset
Description
CH0_OFFSET
R/W
0000 0000
0000 0000
Channel 0 Conversion Offset. fOFFSET_0 =
(CH0_OFFSET/216)*fREF0
7.6.11 Address 0x0D, OFFSET_CH1
Figure 28. Address 0x0D, OFFSET_CH1
15
14
13
12
11
10
9
8
3
2
1
0
CH1_OFFSET
7
6
5
4
CH1_OFFSET
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 21. Address 0x0D, OFFSET_CH1 Field Descriptions
Bit
15:0
Field
Type
Reset
Description
CH1_OFFSET
R/W
0000 0000
0000 0000
Channel 1 Conversion Offset. fOFFSET_1 =
(CH1_OFFSET/216)*fREF1
7.6.12 Address 0x0E, OFFSET_CH2 (LDC1314 only)
Figure 29. Address 0x0E, OFFSET_CH2
15
14
13
12
11
10
9
8
3
2
1
0
CH2_OFFSET
7
6
5
4
CH2_OFFSET
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 22. Address 0x0E, OFFSET_CH2 Field Descriptions
Bit
15:0
Field
Type
Reset
Description
CH2_OFFSET
R/W
0000 0000
0000 0000
Channel 2 Conversion Offset. fOFFSET_2 =
(CH2_OFFSET/216)*fREF2
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7.6.13 Address 0x0F, OFFSET_CH3 (LDC1314 only)
Figure 30. Address 0x0F, OFFSET_CH3
15
14
13
12
11
10
9
8
3
2
1
0
CH3_OFFSET
7
6
5
4
CH3_OFFSET
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 23. Address 0x0F, OFFSET_CH3 Field Descriptions
Bit
15:0
Field
Type
Reset
Description
CH3_OFFSET
R/W
0000 0000 Channel 3 Conversion Offset. fOFFSET_3 =
0000 0000 (CH3_OFFSET/216)*fREF3
7.6.14 Address 0x10, SETTLECOUNT_CH0
Figure 31. Address 0x10, SETTLECOUNT_CH0
15
14
13
12
11
CH0_SETTLECOUNT
10
9
8
7
6
5
4
3
CH0_SETTLECOUNT
2
1
0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 24. Address 0x11, SETTLECOUNT_CH0 Field Descriptions
Bit
15:0
Field
Type
Reset
CH0_SETTLECOUNT
R/W
0000 0000 Channel 0 Conversion Settling
0000 0000 The LDC will use this settling time to allow the LC sensor to
stabilize before initiation of a conversion on Channel 0.
If the amplitude has not settled prior to the conversion start, an
Amplitude error will be generated if reporting of this type of error
is enabled.
b0000 0000 0000 0000: Settle Time (tS0)= 32 ÷ fREF0
b0000 0000 0000 0001: Settle Time (tS0)= 32 ÷ fREF0
b0000 0000 0000 0010 - b1111 1111 1111 1111: Settle Time
(tS0)= (CH0_SETTLECOUNTˣ16) ÷ fREF0
Description
7.6.15 Address 0x11, SETTLECOUNT_CH1
Figure 32. Address 0x11, SETTLECOUNT_CH1
15
14
13
12
11
CH1_SETTLECOUNT
10
9
8
7
6
5
4
3
CH1_SETTLECOUNT
2
1
0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
24
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Table 25. Address 0x12, SETTLECOUNT_CH1 Field Descriptions
Bit
15:0
Field
Type
Reset
CH1_SETTLECOUNT
R/W
0000 0000 Channel 1 Conversion Settling
0000 0000 The LDC will use this settling time to allow the LC sensor to
stabilize before initiation of a conversion on a Channel 1.
If the amplitude has not settled prior to the conversion start, an
Amplitude error will be generated if reporting of this type of error
is enabled.
b0000 0000 0000 0000: Settle Time (tS1)= 32 ÷ fREF1
b0000 0000 0000 0001: Settle Time (tS1)= 32 ÷ fREF1
b0000 0000 0000 0010 - b1111 1111 1111 1111: Settle Time
(tS1)= (CH1_SETTLECOUNTˣ16) ÷ fREF1
Description
7.6.16 Address 0x12, SETTLECOUNT_CH2 (LDC1314 only)
Figure 33. Address 0x12, SETTLECOUNT_CH2
15
14
13
12
11
CH2_SETTLECOUNT
10
9
8
7
6
5
4
3
CH2_SETTLECOUNT
2
1
0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 26. Address 0x12, SETTLECOUNT_CH2 Field Descriptions
Bit
15:0
Field
Type
Reset
Description
CH2_SETTLECOUNT
R/W
0000 0000 Channel 2 Conversion Settling
0000 0000 The LDC will use this settling time to allow the LC sensor to
stabilize before initiation of a conversion on Channel 2.
If the amplitude has not settled prior to the conversion start, an
Amplitude error will be generated if reporting of this type of error
is enabled.
b0000 0000 0000 0000: Settle Time (tS2)= 32 ÷ fREF2
b0000 0000 0000 0001: Settle Time (tS2)= 32 ÷ fREF2
b0000 0000 0000 0010 - b1111 1111 1111 1111: Settle Time
(tS2)= (CH2_SETTLECOUNTˣ16) ÷ fREF2
7.6.17 Address 0x13, SETTLECOUNT_CH3 (LDC1314 only)
Figure 34. Address 0x13, SETTLECOUNT_CH3
15
14
13
12
11
CH3_SETTLECOUNT
10
9
8
7
6
5
4
3
CH3_SETTLECOUNT
2
1
0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 27. Address 0x13, SETTLECOUNT_CH3 Field Descriptions
Bit
15:0
Field
Type
Reset
CH3_SETTLECOUNT
R/W
0000 0000 Channel 3 Conversion Settling
0000 0000 The LDC will use this settling time to allow the LC sensor to
stabilize before initiation of a conversion on Channel 3.
If the amplitude has not settled prior to the conversion start, an
Amplitude error will be generated if reporting of this type of error
is enabled
b0000 0000 0000 0000: Settle Time (tS3)= 32 ÷ fREF3
b0000 0000 0000 0001: Settle Time (tS3)= 32 ÷ fREF3
b0000 0000 0000 0010 - b1111 1111 1111 1111: Settle Time
(tS3)= (CH3_SETTLECOUNTˣ16) ÷ fREF3
Description
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7.6.18 Address 0x14, CLOCK_DIVIDERS_CH0
Figure 35. Address 0x14, CLOCK_DIVIDERS_CH0
15
14
13
CH0_FIN_DIVIDER
7
6
12
11
10
RESERVED
5
4
3
CH0_FREF_DIVIDER
2
9
8
CH0_FREF_DIVIDER
1
0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 28. Address 0x14, CLOCK_DIVIDERS_CH0 Field Descriptions
Bit
Field
Type
15:12
CH0_FIN_DIVIDER
R/W
11:10
RESERVED
R/W
9:0
CH0_FREF_DIVIDER
Reset
Description
0000
Channel 0 Input Divider Sets the divider for Channel 0 input.
Must be set to ≥2 if the Sensor frequency is ≥ 8.75MHz
b0000: Reserved. Do not use.
CH0_FIN_DIVIDER≥b0001:
fin0 = fSENSOR0/CH0_FIN_DIVIDER
00
Reserved. Set to b00.
00 0000
0000
Channel 0 Reference Divider Sets the divider for Channel 0
reference. Use this to scale the maximum conversion frequency.
b00’0000’0000: Reserved. Do not use.
CH0_FREF_DIVIDER≥b00’0000’0001:
fREF0 = fCLK/CH0_FREF_DIVIDER
R/W
7.6.19 Address 0x15, CLOCK_DIVIDERS_CH1
Figure 36. Address 0x15, CLOCK_DIVIDERS_CH1
15
14
13
CH1_FIN_DIVIDER
7
6
12
11
10
RESERVED
5
4
3
CH1_FREF_DIVIDER
2
9
8
CH1_FREF_DIVIDER
1
0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 29. Address 0x15, CLOCK_DIVIDERS_CH1 Field Descriptions
Bit
Field
Type
15:12
CH1_FIN_DIVIDER
R/W
11:10
RESERVED
R/W
9:0
CH1_FREF_DIVIDER
Reset
Description
0000
Channel 1 Input Divider Sets the divider for Channel 1 input.
Used when the Sensor frequency is greater than the maximum
FIN.
b0000: Reserved. Do not use.
CH1_FIN_DIVIDER≥b0001:
fin1 = fSENSOR1/CH1_FIN_DIVIDER
00
Reserved. Set to b00.
00 0000
0000
Channel 1 Reference Divider Sets the divider for Channel 1
reference. Use this to scale the maximum conversion frequency.
b00’0000’0000: Reserved. Do not use.
CH1_FREF_DIVIDER≥ b00’0000’0001:
fREF1 = fCLK/CH1_FREF_DIVIDER
R/W
7.6.20 Address 0x16, CLOCK_DIVIDERS_CH2 (LDC1314 only)
Figure 37. Address 0x16, CLOCK_DIVIDERS_CH2
15
7
26
14
13
CH2_FIN_DIVIDER
6
5
12
11
10
RESERVED
4
3
CH2_FREF_DIVIDER
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2
9
8
CH2_FREF_DIVIDER
1
0
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LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 30. Address 0x16, CLOCK_DIVIDERS_CH2 Field Descriptions
Field
Type
Reset
Description
15:12
Bit
CH2_FIN_DIVIDER
R/W
0000
Channel 2 Input Divider Sets the divider for Channel 2 input.
Must be set to ≥2 if the Sensor frequency is ≥ 8.75MHz.
b0000: Reserved. Do not use.
CH2_FIN_DIVIDER≥b0001:
fIN2 = fSENSOR2/CH2_FIN_DIVIDER
11:10
RESERVED
R/W
00
Reserved. Set to b00
CH2_FREF_DIVIDER
R/W
00 0000
0000
Channel 2 Reference Divider Sets the divider for Channel 2
reference. Use this to scale the maximum conversion frequency.
b00’0000’0000: Reserved. Do not use.
CH2_FREF_DIVIDER ≥ b00’0000’0001: fREF2 =
fCLK/CH2_FREF_DIVIDER
9:0
7.6.21 Address 0x17, CLOCK_DIVIDERS_CH3 (LDC1314 only)
Figure 38. Address 0x17, CLOCK_DIVIDERS_CH3
15
14
13
CH3_FIN_DIVIDER
7
6
12
11
10
9
8
CH3_FREF_DIVIDER
RESERVED
5
4
3
CH3_FREF_DIVIDER
2
1
0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 31. Address 0x17, CLOCK_DIVIDERS_CH3
Field
Type
Reset
Description
15:12
Bit
CH3_FIN_DIVIDER
R/W
0000
Channel 3 Input Divider Sets the divider for Channel 3 input.
Must be set to ≥2 if the Sensor frequency is ≥ 8.75MHz.
b0000: Reserved. Do not use.
CH3_FIN_DIVIDER≥b0001:
fIN3 = fSENSOR3/CH3_FIN_DIVIDER
11:10
RESERVED
R/W
00
Reserved. Set to b00
CH3_FREF_DIVIDER
R/W
00 0000
0000
Channel 3 Reference Divider Sets the divider for Channel 3
reference. Use this to scale the maximum conversion frequency.
b00’0000’0000: reserved
CH3_FREF_DIVIDER ≥ b00’0000’0001: fREF3 =
fCLK/CH3_FREF_DIVIDER
9:0
7.6.22 Address 0x18, STATUS
Figure 39. Address 0x18, STATUS
15
14
13
ERR_UR
12
ERR_OR
11
ERR_WD
6
DRDY
5
4
3
CH0_UNREA
DCONV
ERR_CHAN
7
RESERVED
RESERVED
10
ERR_AHE
9
ERR_ALE
8
ERR_ZC
2
1
0
CH1_
CH2_
CH3_
UNREADCONV UNREADCONV UNREADCONV
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
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Table 32. Address 0x18, STATUS Field Descriptions
Bit
Field
Type
Reset
Description
ERR_CHAN
R
00
Error Channel
Indicates which channel has generated a Flag or Error. Once
flagged, any reported error is latched and maintained until either
the STATUS register or the DATA_CHx register corresponding
to the Error Channel is read.
b00: Channel 0 is source of flag or error.
b01: Channel 1 is source of flag or error.
b10: Channel 2 is source of flag or error (LDC1314 only).
b11: Channel 3 is source of flag or error (LDC1314 only).
13
ERR_UR
R
0
Conversion Under-range Error
b0: No Conversion Under-range error was recorded since the
last read of the STATUS register.
b1: An active channel has generated a Conversion Under-range
error. Refer to STATUS.ERR_CHAN field to determine which
channel is the source of this error.
12
ERR_OR
R
0
Conversion Over-range Error.
b0: No Conversion Over-range error was recorded since the last
read of the STATUS register.
b1: An active channel has generated a Conversion Over-range
error. Refer to STATUS.ERR_CHAN field to determine which
channel is the source of this error.
11
ERR_WD
R
0
Watchdog Timeout Error
b0: No Watchdog Timeout error was recorded since the last
read of the STATUS register.
b1: An active channel has generated a Watchdog Timeout error.
Refer to STATUS.ERR_CHAN field to determine which channel
is the source of this error.
10
ERR_AHE
R
0
Amplitude High Error
b0: No Amplitude High error was recorded since the last read of
the STATUS register.
b1: An active channel has generated an Amplitude High error.
Refer to STATUS.ERR_CHAN field to determine which channel
is the source of this error.
9
ERR_ALE
R
0
Amplitude Low Error
b0: No Amplitude Low error was recorded since the last read of
the STATUS register.
b1: An active channel has generated an Amplitude Low error.
Refer to STATUS.ERR_CHAN field to determine which channel
is the source of this error.
8
ERR_ZC
R
0
Zero Count Error
b0: No Zero Count error was recorded since the last read of the
STATUS register.
b1: An active channel has generated a Zero Count error. Refer
to STATUS.ERR_CHAN field to determine which channel is the
source of this error.
6
DRDY
R
0
Data Ready Flag.
b0: No new conversion result was recorded in the STATUS
register.
b1: A new conversion result is ready. When in Single Channel
Conversion, this indicates a single conversion is available. When
in sequential mode, this indicates that a new conversion result
for all active channels is now available.
3
CH0_UNREADCONV
R
0
Channel 0 Unread Conversion b0: No unread conversion is
present for Channel 0.
b1: An unread conversion is present for Channel 0.
Read Register DATA_CH0 to retrieve conversion results.
2
CH1_ UNREADCONV
R
0
Channel 1 Unread Conversion b0: No unread conversion is
present for Channel 1.
b1: An unread conversion is present for Channel 1.
Read Register DATA_CH1 to retrieve conversion results.
15:14
28
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Table 32. Address 0x18, STATUS Field Descriptions (continued)
Bit
Field
Type
Reset
Description
1
CH2_ UNREADCONV
R
0
Channel 2 Unread Conversion b0: No unread conversion is
present for Channel 2.
b1: An unread conversion is present for Channel 2.
Read Register DATA_CH2 to retrieve conversion results
(LDC1314 only)
0
CH3_ UNREADCONV
R
0
Channel 3 Unread Conversion
b0: No unread conversion is present for Channel 3.
b1: An unread conversion is present for Channel 3.
Read Register DATA_CH3 to retrieve conversion results
(LDC1314 only)
7.6.23 Address 0x19, ERROR_CONFIG
Figure 40. Address 0x19, ERROR_CONFIG
15
UR_ERR2OUT
14
OR_ERR2OUT
13
WD_
ERR2OUT
12
AH_ERR2OUT
11
AL_ERR2OUT
10
9
RESERVED
8
7
UR_ERR2INT
6
OR_ERR2INT
5
WD_ERR2INT
4
AH_ERR2INT
3
AL_ERR2INT
2
ZC_ERR2INT
1
Reserved
0
DRDY_2INT
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 33. Address 0x19, ERROR_CONFIG
Bit
Field
Type
Reset
Description
15
UR_ERR2OUT
R/W
0
Under-range Error to Output Register
b0: Do not report Under-range errors in the DATA_CH x
registers.
b1: Report Under-range errors in the DATA_CHx.CHx_ERR_UR
register field corresponding to the channel that generated the
error.
14
OR_ERR2OUT
R/W
0
Over-range Error to Output Register
b0: Do not report Over-range errors in the DATA_CHx registers.
b1: Report Over-range errors in the DATA_CHx.CHx_ERR_OR
register field corresponding to the channel that generated the
error.
13
WD_ ERR2OUT
R/W
0
Watchdog Timeout Error to Output Register
b0: Do not report Watchdog Timeout errors in the DATA_CHx
registers.
b1: Report Watchdog Timeout errors in the
DATA_CHx.CHx_ERR_WD register field corresponding to the
channel that generated the error.
12
AH_ERR2OUT
R/W
0
Amplitude High Error to Output Register
b0:Do not report Amplitude High errors in the DATA_CHx
registers.
b1: Report Amplitude High errors in the
DATA_CHx.CHx_ERR_AE register field corresponding to the
channel that generated the error.
11
AL_ERR2OUT
R/W
0
Amplitude Low Error to Output Register
b0: Do not report Amplitude High errors in the DATA_CHx
registers.
b1: Report Amplitude High errors in the
DATA_CHx.CHx_ERR_AE register field corresponding to the
channel that generated the error.
7
UR_ERR2INT
R/W
0
Under-range Error to INTB
b0: Do not report Under-range errors by asserting INTB pin and
STATUS register.
b1: Report Under-range errors by asserting INTB pin and
updating STATUS.ERR_UR register field.
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Table 33. Address 0x19, ERROR_CONFIG (continued)
Bit
Field
Type
Reset
Description
6
OR_ERR2INT
R/W
0
Over-range Error to INTB
b0: Do not report Over-range errors by asserting INTB pin and
STATUS register.
b1: Report Over-range errors by asserting INTB pin and
updating STATUS.ERR_OR register field.
5
WD_ERR2INT
R/W
0
Watchdog Timeout Error to INTB b0: Do not report Under-range
errors by asserting INTB pin and STATUS register.
b1: Report Watchdog Timeout errors by asserting INTB pin and
updating STATUS.ERR_WD register field.
4
AH_ERR2INT
R/W
0
Amplitude High Error to INTB b0: Do not report Amplitude High
errors by asserting INTB pin and STATUS register.
b1: Report Amplitude High errors by asserting INTB pin and
updating STATUS.ERR_AHE register field.
3
AL_ERR2INT
R/W
0
Amplitude Low Error to INTB b0: Do not report Amplitude Low
errors by asserting INTB pin and STATUS register.
b1: Report Amplitude Low errors by asserting INTB pin and
updating STATUS.ERR_ALE register field.
2
ZC_ERR2INT
R/W
0
Zero Count Error to INTB b0: Do not report Zero Count errors by
asserting INTB pin and STATUS register.
b1: Report Zero Count errors by asserting INTB pin and
updating STATUS. ERR_ZC register field.
1
Reserved
R/W
0
Reserved (set to b0)
0
DRDY_2INT
R/W
0
Data Ready Flag to INTB b0: Do not report Data Ready Flag by
asserting INTB pin and STATUS register.
b1: Report Data Ready Flag by asserting INTB pin and updating
STATUS. DRDY register field.
7.6.24 Address 0x1A, CONFIG
Figure 41. Address 0x1A, CONFIG
15
14
ACTIVE_CHAN
7
INTB_DIS
13
SLEEP_MODE
_EN
12
RP_OVERRID
E_EN
5
4
6
HIGH_CURRE
NT_DRV
11
10
SENSOR_ACTI AUTO_AMP_DI
VATE_SEL
S
3
9
REF_CLK_SR
C
8
RESERVED
1
0
2
RESERVED
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 34. Address 0x1A, CONFIG Field Descriptions
Bit
15:14
13
30
Field
Type
Reset
Description
ACTIVE_CHAN
R/W
00
Active Channel Selection
Selects channel for continuous conversions when
MUX_CONFIG.SEQUENTIAL is 0.
b00: Perform continuous conversions on Channel 0
b01: Perform continuous conversions on Channel 1
b10: Perform continuous conversions on Channel 2 (LDC1314
only)
b11: Perform continuous conversions on Channel 3 (LDC1314
only)
SLEEP_MODE_EN
R/W
1
Sleep Mode Enable
Enter or exit low power Sleep Mode.
b0: Device is active.
b1: Device is in Sleep Mode.
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Table 34. Address 0x1A, CONFIG Field Descriptions (continued)
Bit
Field
Type
Reset
Description
12
RP_OVERRIDE_EN
R/W
0
Sensor RP Override Enable
Provides control over Sensor current drive used during the
conversion time for Ch. x, based on the programmed value in
the CHx_IDRIVE field.
b0: Override off
b1: RP Override on
11
SENSOR_ACTIVATE_SEL
R/W
1
Sensor Activation Mode Selection.
Set the mode for sensor initialization.
b0: Full Current Activation Mode – the LDC will drive maximum
sensor current for a shorter sensor activation time.
b1: Low Power Activation Mode – the LDC uses the value
programmed in DRIVE_CURRENT_CHx during sensor
activation to minimize power consumption.
10
AUTO_AMP_DIS
R/W
0
Automatic Sensor Amplitude Correction Disable
Setting this bit will disable the automatic Amplitude correction
algorithm and stop the updating of the CHx_INIT_IDRIVE field.
b0: Automatic Amplitude correction enabled
b1: Automatic Amplitude correction is disabled. Recommended
for precision applications.
9
REF_CLK_SRC
R/W
0
Select Reference Frequency Source b0: Use Internal oscillator
as reference frequency b1: Reference frequency is provided
from CLKIN pin.
8
RESERVED
R/W
0
Reserved. Set to b0.
7
INTB_DIS
R/W
0
INTB Disable
b0: INTB pin will be asserted when status register updates.
b1: INTB pin will not be asserted when status register updates
6
HIGH_CURRENT_DRV
R/W
0
High Current Sensor Drive
b0: The LDC will drive all channels with normal sensor current
(1.5mA max).
b1: The LDC will drive channel 0 with current >1.5mA.
This mode is not supported if AUTOSCAN_EN = b1 (multichannel mode)
RESERVED
R/W
00 0001
Reserved Set to b00’0001
5:0
7.6.25 Address 0x1B, MUX_CONFIG
Figure 42. Address 0x1B, MUX_CONFIG
15
AUTOSCAN_E
N
7
14
13
RR_SEQUENCE
12
11
10
RESERVED
9
8
6
4
3
2
1
DEGLITCH
0
5
RESERVED
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 35. Address 0x1B, MUX_CONFIG Field Descriptions
Bit
Field
Type
Reset
Description
15
AUTOSCAN_EN
R/W
0
Auto-Scan Mode Enable
b0: Continuous conversion on the single channel selected by
CONFIG.ACTIVE_CHAN register field.
b1: Auto-Scan conversions as selected by
MUX_CONFIG.RR_SEQUENCE register field.
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Table 35. Address 0x1B, MUX_CONFIG Field Descriptions (continued)
Field
Type
Reset
Description
14:13
Bit
RR_SEQUENCE
R/W
00
Auto-Scan Sequence Configuration Configure multiplexing
channel sequence. The LDC will perform a single conversion on
each channel in the sequence selected, and then restart the
sequence continuously.
b00: Ch0, Ch1
b01: Ch0, Ch1, Ch2 (LDC1314 only)
b10: Ch0, Ch1, Ch2, Ch3 (LDC1314 only)
b11: Ch0, Ch1
12:3
RESERVED
R/W
00 0100
0001
Reserved. Must be set to 00 0100 0001
2:0
DEGLITCH
R/W
111
Input deglitch filter bandwidth.
Select the lowest setting that exceeds the oscillation tank
oscillation frequency.
b001: 1MHz
b100: 3.3MHz
b101: 10MHz
b111: 33MHz
7.6.26 Address 0x1C, RESET_DEV
Figure 43. Address 0x1C, RESET_DEV
15
RESET_DEV
14
7
6
13
12
11
10
9
OUTPUT_GAIN
3
2
RESERVED
5
4
8
RESERVED
1
0
RESERVED
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 36. Address 0x1C, RESET_DEV Field Descriptions
Bit
Field
Type
Reset
Description
15
RESET_DEV
R/W
0
Device Reset
Write b1 to reset the device. Will always readback 0.
14:11
RESERVED
R/W
0000
Reserved. Set to b0000
10:9
OUTPUT_GAIN
R/W
000
Output gain control 00:
Gain =1 (0 bits shift) 01:
Gain = 4 (2 bits shift) 10:
Gain = 8 (3 bits shift) 11 :
Gain = 16 (4 bits shift)
8:0
RESERVED
R/W
0 0000
0000
Reserved, Set to b0 0000 0000
7.6.27 Address 0x1E, DRIVE_CURRENT_CH0
Figure 44. Address 0x1E, DRIVE_CURRENT_CH0
15
14
13
CH0_IDRIVE
12
11
5
4
3
7
6
CH0_INIT_IDRIVE
10
9
CH0_INIT_IDRIVE
8
2
1
0
RESERVED
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
32
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Table 37. Address 0x1E, DRIVE_CURRENT_CH0 Field Descriptions
Field
Type
Reset
Description
15:11
Bit
CH0_IDRIVE
R/W
0 0000
Channel 0 L-C Sensor drive current
This field defines the Drive Current used during the settling +
conversion time of Channel 0 sensor clock.
RP_OVERRIDE_EN bit must be set to 1.
10:6
CH0_INIT_IDRIVE
R
0 0000
Channel 0 Sensor Current Drive
This field stores the Initial Drive Current calculated during the
initial Amplitude Calibration phase.
It is updated after each Amplitude Correction phase of the
sensor clock if the AUTO_AMP_DIS field is NOT set.
5:0
RESERVED
–
00 0000
Reserved
7.6.28 Address 0x1F, DRIVE_CURRENT_CH1
Figure 45. Address 0x1F, DRIVE_CURRENT_CH1
15
14
7
6
CH1_INIT_IDRIVE
13
CH1_IDRIVE
12
11
5
4
3
10
9
CH1_INIT_IDRIVE
8
2
1
0
RESERVED
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 38. Address 0x1F, DRIVE_CURRENT_CH1 Field Descriptions
Bit
Field
Type
Reset
Description
15:11
CH1_IDRIVE
R/W
0 0000
Channel 1 L-C Sensor drive current
This field defines the Drive Current used during the settling +
conversion time of Channel 1 sensor clock.
RP_OVERRIDE_EN bit must be set to 1.
10:6
CH1_INIT_IDRIVE
R
0 0000
Channel 1 Sensor Current Drive
This field stores the Initial Drive Current calculated during the
initial Amplitude Calibration phase.
It is updated after each Amplitude Correction phase of the
sensor clock if the AUTO_AMP_DIS field is NOT set.
5:0
RESERVED
-
00 0000
Reserved
7.6.29 Address 0x20, DRIVE_CURRENT_CH2 (LDC1314 only)
Figure 46. Address 0x20, DRIVE_CURRENT_CH2
15
14
7
6
CH2_INIT_IDRIVE
13
CH2_IDRIVE
12
11
5
4
3
10
9
CH2_INIT_IDRIVE
8
2
1
0
RESERVED
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 39. Address 0x20, DRIVE_CURRENT_CH2 Field Descriptions
Bit
15:11
Field
Type
Reset
Description
CH2_IDRIVE
R/W
0 0000
Channel 2 L-C Sensor drive current
This field defines the Drive Current to be used during the settling
+ conversion time of Channel 2 sensor clock.
RP_OVERRIDE_EN bit must be set to 1.
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Table 39. Address 0x20, DRIVE_CURRENT_CH2 Field Descriptions (continued)
Field
Type
Reset
Description
10:6
Bit
CH2_INIT_IDRIVE
R
0 0000
Channel 2 Sensor Current Drive
This field stores the Initial Drive Current calculated during the
initial Amplitude Calibration phase.
It is updated after each Amplitude Correction phase of the
sensor clock if the AUTO_AMP_DIS field is NOT set.
5:0
RESERVED
–
00 0000
Reserved
7.6.30 Address 0x21, DRIVE_CURRENT_CH3 (LDC1314 only)
Figure 47. Address 0x21, DRIVE_CURRENT_CH3
15
14
13
CH3_IDRIVE
12
11
5
4
3
7
6
CH3_INIT_IDRIVE
10
9
CH3_INIT_IDRIVE
8
2
1
0
RESERVED
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 40. DRIVE_CURRENT_CH3 Field Descriptions
Field
Type
Reset
Description
15:11
Bit
CH3_IDRIVE
R/W
0 0000
Channel 3 L-C Sensor drive current
This field defines the Drive Current to be used during the settling
+ conversion time of Channel 3 sensor clock.
RP_OVERRIDE_EN bit must be set to 1.
10:6
CH3_INIT_IDRIVE
R
0 0000
Channel 3 Sensor Current Drive
This field stores the Initial Drive Current calculated during the
initial Amplitude Calibration phase.
It is updated after each Amplitude Correction phase of the
sensor clock if the AUTO_AMP_DIS field is NOT set.
5:0
RESERVED
–
00 0000
Reserved
7.6.31 Address 0x7E, MANUFACTURER_ID
Figure 48. Address 0x7E, MANUFACTURER_ID
15
14
13
12
11
MANUFACTURER_ID
10
9
8
7
6
5
4
3
MANUFACTURER_ID
2
1
0
1
0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 41. Address 0x7E, MANUFACTURER_ID Field Descriptions
Bit
15:0
Field
Type
Reset
MANUFACTURER_ID
R
0101 0100 Manufacturer ID = 0x5449
0100 1001
Description
7.6.32 Address 0x7F, DEVICE_ID
Figure 49. Address 0x7F, DEVICE_ID
7
6
5
4
3
2
DEVICE_ID
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
34
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Table 42. Address 0x7F, DEVICE_ID Field Descriptions
Bit
Field
Type
Reset
7:0
DEVICE_ID
R
0011 0000 Device ID = 0x3054
0101 0100
Description
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
8.1.1 Theory of Operation
8.1.1.1 Conductive Objects in an EM Field
An AC current flowing through an inductor will generate an AC magnetic field. If a conductive material, such as a
metal object, is brought into the vicinity of the inductor, the magnetic field will induce a circulating current (eddy
current) on the surface of the conductor.
Conductive
Target
Eddy
Current
d
Figure 50. Conductor in AC Magnetic Field
The eddy current is a function of the distance, size, and composition of the conductor. The eddy current
generates its own magnetic field, which opposes the original field generated by the sensor inductor. This effect is
equivalent to a set of coupled inductors, where the sensor inductor is the primary winding and the eddy current in
the target object represents the secondary inductor. The coupling between the inductors is a function of the
sensor inductor, and the resistivity, distance, size, and shape of the conductive target. The resistance and
inductance of the secondary winding caused by the eddy current can be modeled as a distance dependent
resistive and inductive component on the primary side (coil). Figure 50 shows a simplified circuit model of the
sensor and the target as coupled coils.
8.1.1.2 L-C Resonators
An EM field can be generated using an L-C resonator, or L-C tank. One topology for an L-C tank is a parallel RL-C construction, as shown in Figure 51.
36
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Application Information (continued)
Distance-dependent
coupling
M(d)
Eddy
Current
CPAR
Distance (d)
Target
Resistance
Coil Series
Resistance (Rs)
I
RP(d)
L(d)
CPAR + CTANK
Parallel Electrical
Model, L-C Tank
Figure 51. Electrical Model of the L-C Tank Sensor
In brief, an oscillator is constructed by combining a frequency selective circuit with a gain block in a closed loop.
The criteria for oscillation are: (1) loop gain > 1, and (2) closed loop phase shift of 2π radians. In the context of
an oscillator, the R-L-C resonator provides the frequency selectivity and contributes to the phase shift. At
resonance, the impedance of the reactive components (L and C) cancels, leaving only RP, the lossy (resistive)
element in the circuit, and the voltage amplitude is maximized. The RP can be used to determine the sensor drive
current. A lower RP requires a larger sensor current to maintain a constant oscillation amplitude. The sensor
oscillation frequency fSENSOR is given by:
1
¦SENSOR
2S LC
1
Q
2
5 10 9
Q LC
|
1
2S LC
where
•
•
C is the sensor capacitance (CTANK + CPAR)
L is the inductance
(9)
The value of RP can be approximated using:
Q
RP
C
L
where
•
RS is the AC series resistance of the inductor
(10)
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Application Information (continued)
Texas Instruments' WEBENCH design tool can be used for coil design, in which the parameter values for RP, L
and C are calculated. See http://www.ti.com/webench.
RP is a function of target distance, target material, and sensor characteristics. Figure 52 shows that RP is directly
proportional to the distance between the sensor and the target. The graph represents a 14-mm diameter PCB
coil (23 turns, 4-mil trace width, 4-mil spacing between traces, 1-oz copper thickness, FR4).
18
16
14
RP (kΩ)
12
10
8
6
4
2
0
0
1
2
3
4
5
Distance (mm)
6
7
8
Figure 52. Example RP vs. Distance with a 14-mm PCB Coil and 2mm Thick Stainless Steel Target
It is important to configure the LDC current drive so that the sensor will still oscillate at the minimum RP value.
As an example, if the closest target distance in a system with the response shown in Figure 52 is 1mm, then the
LDC RP value is 5 kΩ. The objective is to maintain a sufficient sensor oscillation voltage so that the sensor
frequency can be measured even at the minimum operating distance. See section Current Drive Control
Registers for details on setting the current drive.
The inductance that is measured by the LDC is
1
L(d) Linf M(d)
(2S ¦SENSOR )2 C
where
•
•
•
•
•
L(d) is the measured sensor inductance, for a distance d between the sensor coil and target
Linf is the inductance of the sensing coil without a conductive target (target at infinite distance)
M(d) is the mutual inductance
fSENSOR = sensor oscillation frequency for a distance d between the sensor coil and target
C = CTANK + CPAR
(11)
Figure 53 shows an example of variation in sensor frequency and inductance as a function of distance for a 14mm diameter PCB coil (23 turns, 4-mil trace width, 4-mil spacing between traces, 1-oz copper thickness, FR4).
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Application Information (continued)
4
24
Target D = 1 x coil ‡
3.5
21
3
18
2.5
15
2
12
1.5
Inductance (µH)
Sensor Frequency (MHz)
Target D = 0.5 x coil ‡
9
Sensor Frequency (MHz)
Inductance (µH)
1
0
1
2
3
4
6
5 6 7 8 9 10 11 12 13 14
Target Distance D (mm)
D011
Figure 53. Example Sensor Frequency, Inductance vs. Target Distance
with 14-mm PCB Coil and 1.5 mm Thick Aluminum Target
In the absence of magnetic materials, such as ferrous metals and ferrites, the inductance shift, and therefore the
measured frequency shift, depends only on current flow geometries. Temperature drift is dominated by physical
expansion of the inductor and other mechanical system components over temperature which alter current flow
geometries. Note that the additional temperature drift of the sensor capacitor must also be taken into account.
For additional information on temperature effects and temperature compensation, see LDC1000 Temperature
Compensation (SNAA212)
8.2 Typical Application
Example of a multi-channel implementation using the LDC1312. This example is representative of an axial
displacement application, in which the target movement is perpendicular to the plane of the coil. The second
channel can be used to sense proximity of a second target, or it can be used for temperature compensation by
connecting a reference coil.
3.3 V
3.3 V
LDC1312
MCU
CLKIN
40 MHz
SD
GPIO
INTB
GPIO
IN0A
Target
VDD
VDD
IN0B
Sensor 0
Core
GND
IN1A
Target
IN1B
SDA
I2C
ADDR
Sensor 1
I 2C
Peripheral
SCL
3.3 V
GND
Figure 54. Example Multi-Channel Application - LDC1312
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Typical Application (continued)
8.2.1 Design Requirements
•
•
•
•
•
•
•
•
Design example in which Sensor 0 is used for proximity measurement and Sensor 1 is used for temperature
compensation:
using WEBENCH for coil design
Target distance = 0.1 cm
Distance resolution = 0.2 µm
Target diameter = 1 cm
Target material = stainless steel (SS416)
Number of PCB layers for the coil = 2
The application requires 1kSPS ( TSAMPLE = 1000 µs)
8.2.2 Detailed Design Procedure
1.
2.
3.
4.
5.
6.
7.
40
The target distance, resolution and diameter are used as inputs to WEBENCH to design the sensor coil, The
resulting coil design is a 2 layer coil, with an area of 2.5 cm2, diameter of 1.77 cm, and 39 turns. The values
for RP, L and C are: RP = 6.6 kΩ, L = 43.9 µH, C = 100 pF.
Using L and C, fSENSOR = 1/2π√(LC) = 1/2π√(43.9*10-6 * 100*10-12) = 2.4 MHz
Using a system master clock of 40 MHz applied to the CLKIN pin allows flexibility for setting the internal
clock frequencies. The sensor coil is connected to channel 0 (IN0A and IN0B pins).
After powering on the LDC, it will be in Sleep Mode. Program the registers as follows (example sets registers
for channel 0 only; channel 1 registers can use equivalent configuration):
Set the dividers for channel 0.
(a) Because the sensor freqeuncy is less than 8.75 MHz, the sensor divider can be set to 1, which means
setting field CH0_FIN_DIVIDER to 0x1. By default, fIN0 = fSENSOR = 2.4MHz.
(b) The design constraint for fREF0 is > 4 × fSENSOR. A 20 MHz reference frequency satisfies this constraint,
so the reference divider should be set to 2. This is done by setting the CH0_FREF_DIVIDER field to
0x02.
(c) The combined value for Chan. 0 divider register (0x14) is 0x1002.
Program the settling time for Channel 0. The calculated Q of the coil is 10(see Multi-Channel and Single
Channel Operation).
(a) CH0_SETTLECOUNT ≥ Q × fREF0 / (16 × fSENSOR0) → 5.2, rounded up to 6. To provide margin to account
for system tolerances, a higher value of 10 is chosen.
(b) Register 0x10 should be programmed to a minimum of 10.
(c) The settle time is: (10 x 16)/20,000,000 = 8 µs
(d) The value for Chan. 0 SETTLECOUNT register (0x10) is 0x000A.
The channel switching delay is ~1μs for fREF = 20 MHz (see Multi-Channel and Single Channel Operation)
Set the conversion time by the programming the reference count for Channel 0. The budget for the
conversion time is : TSAMPLE – settling time – channel switching delay = 1000 – 8 – 1 = 991 µs
(a) To determine the conversion time register value, use the following equation and solve for
CH0_RCOUNT: Conversion Time (tC0)= (CH0_RCOUNTˣ16)/fREF0.
(b) This results in CH0_RCOUNT having a value of 1238 decimal (rounded down)
(c) Set the CH0_RCOUNT register (0x08) to 0x04D6.
Use the default values for the ERROR_CONFIG register (address 0x19). By default, no interrupts are
enabled
Sensor drive current: to set the CH0_IDRIVE field value, read the value from Figure 15 using RP = 6.6 kΩ. In
this case the IDRIVE value should be set to 18 (decimal). The INIT_DRIVE current field should be set to
0x00. The combined value for the DRIVE_CURRENT_CH0 register (addr 0x1E) is 0x9000.
Program the MUX_CONFIG register
(a) Set the AUTOSCAN_EN to b1 bit to enable sequential mode
(b) Set RR_SEQUENCE to b00 to enable data conversion on two channels (channel 0, channel 1)
(c) Set DEGLITCH to b100 to set the input deglitch filter bandwidth to 3.3MHz, the lowest setting that
exceeds the oscillation tank frequency.
(d) The combined value for the MUX_CONFIG register (address 0x1B) is 0x820C
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Typical Application (continued)
8. Finally, program the CONFIG register as follows:
(a) Set the ACTIVE_CHAN field to b00 to select channel 0.
(b) Set SLEEP_MODE_EN field to b0 to enable conversion.
(c) Set RP_OVERRIDE_EN to b1 to disable auto-calibration.
(d) Set SENSOR_ACTIVATE_SEL = b0, for full current drive during sensor activation
(e) Set the AUTO_AMP_DIS field to b1 to disable auto-amplitude correction
(f) Set the REF_CLK_SRC field to b1 to use the external clock source.
(g) Set the other fields to their default values.
(h) The combined value for the CONFIG register (address 0x1A) is 0x1601.
We then read the conversion results for channel 0 and channel 1 every 1000 µs from register addresses
0x00 and 0x02.
8.2.3 Recommended Initial Register Configuration Values
Based on the example configuration in section Detailed Design Procedure, the following register write sequence
is recommended:
Table 43. Recommended Initial Register Configuration Values (Single-channel operation)
Address
Value
Register Name
Comments
0x08
0x04D6
RCOUNT_CH0
Reference count calculated from timing requirements (1 kSPS) and resolution
requirements
0x10
0x000A
SETTLECOUNT_ Minimum settling time for chosen sensor
CH0
0x14
0x1002
CLOCK_DIVIDER CH0_FIN_DIVIDER = 1, CH0_FREF_DIVIDER = 2
S_CH0
0x19
0x0000
ERROR_CONFIG Can be changed from default to report status and error conditions
0x1B
0x020C
MUX_CONFIG
0x1E
0x9000
DRIVE_CURREN Sets sensor drive current on ch 0
T_CH0
0x1A
0x1601
CONFIG
Enable Ch 0 (continuous mode), set Input deglitch bandwidth to 3.3MHz
Select active channel = ch 0, disable auto-amplitude correction and autocalibration, enable full current drive during sensor activation, select external
clock source, wake up device to start conversion. This register write must
occur last because device configuration is not permitted while the LDC is in
active mode.
Table 44. Recommended Initial Register Configuration Values (Multi-channel operation)
Address
Value
Register Name
Comments
0x08
0x04D6
RCOUNT_CH0
Reference count calculated from timing requirements (1 kSPS) and resolution
requirements
0x09
0x04D6
RCOUNT_CH1
Reference count calculated from timing requirements (1 kSPS) and resolution
requirements
0x10
0x000A
SETTLECOUNT_ Minimum settling time for chosen sensor
CH0
0x11
0x000A
SETTLECOUNT_ Minimum settling time for chosen sensor
CH1
0x14
0x1002
CLOCK_DIVIDER CH0_FIN_DIVIDER = 1, CH0_FREF_DIVIDER = 2
S_CH0
0x15
0x1002
CLOCK_DIVIDER CH1_FIN_DIVIDER = 1, CH1_FREF_DIVIDER = 2
S_CH1
0x19
0x0000
ERROR_CONFIG Can be changed from default to report status and error conditions
0x1B
0x820C
MUX_CONFIG
0x1E
0x9000
DRIVE_CURREN Sets sensor drive current on ch 0
T_CH0
0x1F
0x9000
DRIVE_CURREN Sets sensor drive current on ch 1
T_CH1
Enable Ch 0 and Ch 1 (sequential mode), set Input deglitch bandwidth to
3.3MHz
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Table 44. Recommended Initial Register Configuration Values (Multi-channel operation) (continued)
Address
Value
Register Name
Comments
0x1A
0x1601
CONFIG
disable auto-amplitude correction and auto-calibration, enable full current
drive during sensor activation, select external clock source, wake up device
to start conversion. This register write must occur last because device
configuration is not permitted while the LDC is in active mode.
8.2.4 Application Curves
Common test conditions (unless specified otherwise):
• Sensor inductor: 2 layer, 32 turns/layer, 14mm diameter, PCB inductor with L=19.4 µH, RP=5.7 kΩ at 2 MHz
• Sensor capacitor: 330pF 1% COG/NP0
• Target: Aluminum, 1.5 mm thickness
• Channel = Channel 0 (continuous mode)
• CLKIN = 40MHz, CHx_FIN_DIVIDER = 0x01, CHx_FREF_DIVIDER = 0x001
• CH0_RCOUNT = 0xFFFF, SETTLECOUNT_CH0 = 0x0100
• RP_OVERRIDE = 1, AUTO_AMP_DIS = 1, DRIVE_CURRENT_CH0 = 0x9800
3500
2.5
2.25
Measurement Precision (µm)
Output Code - DATA_CH0 (DEC)
Average Code (DEC)
3000
2500
Target Distance =
0.5 x coil diameter
Target Distance =
1 x coil diameter
2000
1500
2
1.75
1.5
1.25
1
0.75
0.5
0.25
1000
0
20%
40%
60%
Target Distance / ‡SENSOR
80%
0
0.1
100%
0.2
D012
Figure 55. Typical Output Code vs. Target Distance (0 to
14mm)
0.3
0.4
0.5
Target Distance / ‡SENSOR
0.6
0.7
D013
Figure 56. Measurement precision in Distance vs. Target
Distance (0 to 10mm)
8.2.5 Inductor Self-Resonant Frequency
Every inductor has a distributed parasitic capacitance, which is dependent on construction and geometry. At the
Self-Resonant Frequency (SRF), the reactance of the inductor cancels the reactance of the parasitic
capacitance. Above the SRF, the inductor will electrically appear to be a capacitor. Because the parasitic
capacitance is not well-controlled or stable, it is recommended that: fSENSOR < 0.8 × fSR.
175.0
150.0
Ls (µH)
125.0
100.0
75.0
50.0
25.0
0.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
Frequency (MHz)
Figure 57. Example Coil Inductance vs. Frequency
42
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In Figure 57, the inductor has a SRF at 6.38 MHz; therefore the inductor should not be operated above 0.8×6.38
MHz, or 5.1 MHz.
9 Power Supply Recommendations
•
•
The LDC requires a voltage supply within 2.7 V and 3.6 V. A multilayer ceramic bypass X7R capacitor of 1μF
between the VDD and GND pins is recommended. If the supply is located more than a few inches from the
LDC, additional bulk capacitance may be required in addition to the ceramic bypass capacitor. An electrolytic
capacitor with a value of 10μF is a typical choice.
The optimum placement is closest to the VDD and GND terminals of the device. Care should be taken to
minimize the loop area formed by the bypass capacitor connection, the VDD terminal, and the GND terminal
of the IC. See Figure 58 and Figure 58 for a layout example.
10 Layout
10.1 Layout Guidelines
Avoid long traces to connect the sensor to the LDC. Short traces reduce parasitic capacitances between sensor
inductor and offer higher system performance.
10.2 Layout Example
Figure 58 to Figure 61 show the LDC1312 evaluation module (EVM) layout.
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Layout Example (continued)
Figure 58. Example PCB Layout: Top Layer (Signal)
44
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Layout Example (continued)
Figure 59. Example PCB Layout: Mid-layer 1 (GND)
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Layout Example (continued)
Figure 60. Example PCB Layout: Mid-layer 2 (Power)
46
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Layout Example (continued)
Figure 61. Example PCB Layout: Bottom Layer (Signal)
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11 Device and Documentation Support
11.1 Device Support
11.1.1 Development Support
For related links, see the following:
• Texas Instruments' WEBENCH tool: http://www.ti.com/webench
11.2 Documentation Support
11.2.1 Related Documentation
For related documentation, refer to the following:
• LDC1000 Temperature Compensation (SNAA212)
11.3 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 45. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
LDC1312
Click here
Click here
Click here
Click here
Click here
LDC1314
Click here
Click here
Click here
Click here
Click here
11.4 Trademarks
WEBENCH is a registered trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.5 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
48
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PACKAGE OPTION ADDENDUM
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18-Dec-2014
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
LDC1312DNTR
ACTIVE
WSON
DNT
12
4500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
LDC1312
LDC1312DNTT
ACTIVE
WSON
DNT
12
250
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
LDC1312
LDC1314RGHR
ACTIVE
WQFN
RGH
16
4500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
LDC1314
LDC1314RGHT
ACTIVE
WQFN
RGH
16
250
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
LDC1314
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
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18-Dec-2014
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
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.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
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18-Dec-2014
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
LDC1312DNTR
WSON
DNT
12
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
4500
330.0
12.4
4.3
4.3
1.3
8.0
12.0
Q1
LDC1312DNTT
WSON
DNT
12
250
178.0
12.4
4.3
4.3
1.3
8.0
12.0
Q1
LDC1314RGHR
WQFN
RGH
16
4500
330.0
12.4
4.3
4.3
1.3
8.0
12.0
Q1
LDC1314RGHT
WQFN
RGH
16
250
178.0
12.4
4.3
4.3
1.3
8.0
12.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
18-Dec-2014
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LDC1312DNTR
WSON
DNT
12
4500
367.0
367.0
35.0
LDC1312DNTT
WSON
DNT
12
250
210.0
185.0
35.0
LDC1314RGHR
WQFN
RGH
16
4500
367.0
367.0
35.0
LDC1314RGHT
WQFN
RGH
16
250
210.0
185.0
35.0
Pack Materials-Page 2
MECHANICAL DATA
DNT0012B
WSON - 0.8mm max height
SON (PLASTIC SMALL OUTLINE - NO LEAD)
SDA12B (Rev A)
4214928/A 03/2013
NOTES: 1. All linear dimensions are in millimeters. Dimensions in parenthesis are for reference only.
Dimensioning and tolerancing per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. This package is designed to be soldered to a thermal pad on the board for thermal and mechanical performance.
For more information, refer to QFN/SON PCB application note in literature No. SLUA271 (www.ti.com/lit/slua271).
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PACKAGE OUTLINE
RGH0016A
WQFN - 0.8 mm max height
SCALE 3.500
WQFN
4.1
3.9
B
A
PIN 1 INDEX AREA
0.5
0.3
0.3
0.2
4.1
3.9
DETAIL
OPTIONAL TERMINAL
TYPICAL
C
0.8 MAX
SEATING PLANE
(0.1)
TYP
2.6 0.1
5
8
SEE TERMINAL
DETAIL
12X 0.5
4
9
4X
1.5
1
12
16X
PIN 1 ID
(OPTIONAL)
13
16
16X
0.3
0.2
0.1
0.05
C A
C
B
0.5
0.3
4214978/A 10/2013
NOTES:
1. All linear dimensions are in millimeters. Dimensions in parenthesis are for reference only. Dimensioning and tolerancing
per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance.
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EXAMPLE BOARD LAYOUT
RGH0016A
WQFN - 0.8 mm max height
WQFN
( 2.6)
SYMM
16
13
SEE DETAILS
16X (0.6)
16X (0.25)
1
12
(0.25) TYP
SYMM
(3.8)
(1)
9
4
12X (0.5)
5X ( 0.2)
VIA
8
5
(1)
(3.8)
LAND PATTERN EXAMPLE
SCALE:15X
0.07 MIN
ALL AROUND
0.07 MAX
ALL AROUND
METAL
SOLDER MASK
OPENING
METAL
SOLDER MASK
OPENING
NON SOLDER MASK
DEFINED
(PREFERRED)
SOLDER MASK
DEFINED
SOLDER MASK DETAILS
4214978/A 10/2013
NOTES: (continued)
4. This package is designed to be soldered to a thermal pad on the board. For more information, see QFN/SON PCB application report
in literature No. SLUA271 (www.ti.com/lit/slua271).
www.ti.com
EXAMPLE STENCIL DESIGN
RGH0016A
WQFN - 0.8 mm max height
WQFN
SYMM
(0.675)
METAL
TYP
13
16
16X (0.6)
16X (0.25)
12
1
(0.25) TYP
(0.675)
SYMM
(3.8)
12X (0.5)
9
4
8
5
4X
(1.15)
(3.8)
SOLDER PASTE EXAMPLE
BASED ON 0.125 mm THICK STENCIL
EXPOSED PAD
78% PRINTED SOLDER COVERAGE BY AREA
SCALE:15X
4214978/A 10/2013
NOTES: (continued)
5. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
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