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LMP91300
SNOSCS3B – SEPTEMBER 2013 – REVISED MARCH 2014
LMP91300 Industrial Inductive Proximity Sensor AFE
1 Features
3 Description
•
•
•
•
•
•
•
The LMP91300 is a complete analog front end (AFE)
optimized for use in industrial inductive proximity
sensors. The LMP91300 directly converts the RP of
the external LC tank into a digital value.
1
•
•
•
•
•
•
Post Production Configuration and Calibration
Programmable Decision Thresholds
Programmable Hysteresis
Flexible Overload Protection
Digital Temperature Compensation
Integrated LED driver
Small Form Factor, Supports 4mm Sensors
(DSBGA Package)
Low Power Consumption
Integrated Voltage Regulator
3-Wire Capability
Supports NPN and PNP Modes
Normally Open (NO) and Normally Closed (NC)
Supported
16-bit Resolution Threshold Setting
Post-manufacturing configuration and calibration is
fully supported. The temperature dependence of the
sensor is digitally compensated, using an external
temperature sensor. The LMP91300 provides
programmable
thresholds,
programmable
temperature compensation and programmable
oscillation
frequency
range.
Due
to
its
programmability, the LMP91300 can be used with a
wide variety of external inductors and its detection
thresholds can be adjusted to the desired detection
distances.
An internal voltage regulator allows the device to
operate with a supply from 6.5V to 40V. The output
can be programmed to drive an external transistor in
either NPN or PNP mode.
2 Applications
•
•
•
Available in 4mm × 5mm 24-terminal WQFN and
2.05mm × 2.67mm 20-terminal DSBGA packages,
the LMP91300 operates from -40°C to +125°C.
Industrial Proximity Detection
Industrial Production Lines
Industrial Automation
Device Information
ORDER NUMBER
PACKAGE
BODY SIZE
LMP91300NHZ
WQFN (24)
4mm x 5mm
LMP91300YZR
DSBGA (20)
2.05mm x 2.67mm
3-Wire PNP Configuration
6.5V to 40V
REXT B
C1
RSENSE
+
R1
-
CFB
LED
CFA
CF
EXT B
CV+/EXT E
Load
V+/EXT E
SWDRV
INA
LMP91300 SENSE1+
INB
NTC
SENSE2+
CBY
TEMP+
GND
SENSECBY
3-Wire PNP
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.
LMP91300
SNOSCS3B – SEPTEMBER 2013 – REVISED MARCH 2014
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Terminal Configuration and Functions................
Specifications.........................................................
1
1
1
2
3
5
6.1
6.2
6.3
6.4
6.5
6.6
6.7
5
5
5
5
6
7
8
Absolute Maximum Ratings .....................................
Handling Ratings.......................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics ..........................................
Timing Requirements ................................................
Typical Characteristics ..............................................
Detailed Description ............................................ 11
7.1 Overview ................................................................. 11
7.2 Functional Block Diagram ....................................... 11
7.3
7.4
7.5
7.6
8
Feature Description.................................................
Device Functional Modes........................................
Programming...........................................................
Register Maps .........................................................
11
14
14
18
Application and Implementation ........................ 28
8.1 Application Information............................................ 28
8.2 Typical Application .................................................. 28
9 Power Supply Recommendations...................... 35
10 Layout................................................................... 35
10.1 Layout Guidelines ................................................. 35
10.2 Layout Example .................................................... 36
11 Device and Documentation Support ................. 37
11.1 Trademarks ........................................................... 37
11.2 Electrostatic Discharge Caution ............................ 37
11.3 Glossary ................................................................ 37
12 Mechanical, Packaging, and Orderable
Information ........................................................... 37
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision A (September 2013) to Revision B
Page
•
Changed layout to new datasheet format............................................................................................................................... 1
•
Added Burn Current Specification. ......................................................................................................................................... 6
•
Added additional information to Low RP, Close Target, Under Range Switch Enable section. .......................................... 12
•
Changed typo. ..................................................................................................................................................................... 31
•
Added additional information to REXTB section. .................................................................................................................... 31
Changes from Original (September 2013) to Revision A
Page
•
Changed to Production Data ................................................................................................................................................. 1
•
Added CSP package ............................................................................................................................................................. 3
2
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SNOSCS3B – SEPTEMBER 2013 – REVISED MARCH 2014
5 Terminal Configuration and Functions
CBY
TEMP+
TEMP-
INB
INA
24
23
22
21
20
LMP91300 WQFN
Top View
P1
1
19
GND
P2
2
18
CFA
P3
3
17
CFB
P4
4
16
NC
DAP
(GND)
13
SENSE2+/SWIF RX
12
7
SENSE1+
LED
11
NC
SENSE-
14
10
6
SWDRV
GND
9
GND
EXT B
15
8
5
V+/EXT E
P5
LMP91300 WQFN Terminal Functions
TERMINAL
NUMBER
NAME
TYPE
DESCRIPTION
1-5
P1-5
G
Connect to Ground
6
GND
G
Board Ground
7
LED
O
LED Driver Output
8
V+/EXT E
P
Chip V+/External transistor, emitter
9
EXT B
P
External transistor, base
10
SWDRV
O
Drive for external transistor switch
11
SENSE-
I
Negative sense Input
12
SENSE1+
I
Positive sense Input
13
SENSE2+/SWIF RX
I
Positive sense Input and Single Wire Interface receive
14
NC
N/A
15
GND
G
16
NC
N/A
17
CFB
I
Filter capacitor value based on sensor oscillation frequency
No connect
Board ground
No connect
18
CFA
I
Filter capacitor value based on sensor oscillation frequency
19
GND
G
Board ground
20
INA
I
External LC tank
21
INB
I
External LC tank
22
TEMP-
G
NTC ground, connect to board ground
23
TEMP+
I
Analog Temperature Sensor Input
24
CBY
O
Bypass capacitor (56nF)
DAP
DAP
G
Connect to Ground
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LMP91300
SNOSCS3B – SEPTEMBER 2013 – REVISED MARCH 2014
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LMP91300 DSBGA
1
2
3
4
4
3
2
1
INA
INB
TEMP+
CBY
CBY
TEMP+
INB
INA
A1
A2
A3
A4
A4
A3
A2
A1
CFA
P2
TEMP-
P1
P1
TEMP-
P2
CFA
B3
B2
B1
A
B1
B2
B3
B4
B4
CFB
P5
P4
P3
P3
P4
P5
CFB
C1
C2
C3
C4
C4
C3
C2
C1
S2+
S-
GND
LED
LED
GND
S-
S2+
D1
D2
D3
D4
D4
D3
D2
D1
S1+
SWDRV
EXT B
V+/EXT E
V+/EXT E
EXT B
SWDRV
S1+
E1
E2
E3
E4
E4
E3
E2
E1
B
C
D
E
A
B
C
D
E
Bottom View
Top View
LMP91300 DSBGA Terminal Functions
4
TERMINAL
NUMBER
NAME
TYPE
A1
INA
I
External LC tank
A2
INB
I
External LC tank
A3
TEMP+
I
Analog Temperature Sensor Input
A4
CBY
O
Bypass capacitor (56nF)
B1
CFA
I
Filter capacitor value based on sensor oscillation frequency
B2
P2
G
Connect to Ground
B3
TEMP-
G
NTC ground, connect to board ground
DESCRIPTION
B4
P1
G
Connect to Ground
C1
CFB
I
Filter capacitor value based on sensor oscillation frequency
C2
P5
G
Connect to Ground
C3
P4
G
Connect to Ground
C4
P3
G
Connect to Ground
D1
SENSE2+/SWIF RX
I
Positive sense Input and Single Wire Interface receive
D2
SENSE-
I
Negative sense Input
D3
GND
G
Board ground
D4
LED
O
LED Driver Output
E1
SENSE1+
I
Positive sense Input
E2
SWDRV
O
Drive for external transistor switch
E3
EXT B
P
External transistor, base
E4
V+/EXT E
P
Chip V+/External transistor, emitter
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6 Specifications
6.1 Absolute Maximum Ratings
(1)
Over operating free-air temperature range (unless otherwise noted)
MIN
Voltage at Terminals 1-5, 7, 10, 11, 17, 18 (B1, B2, B4, C1, C2, C3, C4, D2, D4, E2)
MAX
UNIT
(V+) + 0.3
V
Voltage at Terminals 6, 15, 19, 22 (B3, D3)
0.3
V
Voltage at Terminal 8 (E4)
6
V
Voltage at Terminal 9 (E3)
7
V
Voltage at Terminals 12, 13 (D1, E1)
48
V
Current at Terminals 20, 21 (A1, A2)
8
mA
Voltage at Terminals 23, 24 (A3, A4)
1.6
V
+125
°C
+150
°C
−40
Operating Temperature, TA
Junction Temperature, TJ (2)
(1)
(2)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating
Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
The maximum power dissipation is a function of TJ(MAX), θJA, and TA. The maximum allowable power dissipation at any ambient
temperature is PD = (TJ(MAX) - TA)/ θJA . All numbers apply for packages soldered directly onto a PC board.
6.2 Handling Ratings
TSTG
HBM
(1) (2)
CDM (1) (3)
(1)
(2)
(3)
MIN
MAX
UNIT
−65
+150
°C
Human Body Model
2000
V
Charge-Device Model
500
V
Storage Temperature
Electrostatic discharge (ESD) to measure device sensitivity and immunity to damage caused by assembly line electrostatic discharges in
to the device.
Level listed above is the passing level per ANSI, ESDA, and JEDEC JS-001. JEDEC document JEP155 states that 500-V HBM allows
safe manufacturing with a standard ESD control process.
Level listed above is the passing level per EIA-JEDEC JESD22-C101. JEDEC document JEP157 states that 250-V CDM allows safe
manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
Over operating free-air temperature range (unless otherwise noted)
MIN
VLOOP
Loop Voltage
NOM
MAX
6.5
UNIT
40
V
MAX
UNIT
6.4 Thermal Information (1) (2)
Over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
θJA
Package Thermal Impedance
24-Terminal WQFN
θJA
Package Thermal Impedance
20-Terminal DSBGA
(1)
(2)
MIN
TYP
33.2
°C/W
46
°C/W
The maximum power dissipation is a function of TJ(MAX), θJA, and TA. The maximum allowable power dissipation at any ambient
temperature is PD = (TJ(MAX) - TA)/ θJA . All numbers apply for packages soldered directly onto a PC board.
The package thermal impedance is calculated in accordance with JESD 51-7.
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6.5 Electrical Characteristics
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(1) (2)
Unless otherwise specified, all limits are ensured at TA = TJ = 25°C, Loop Voltage = 24V. (3). Boldface limits apply at the
temperature extremes.
SYMBOL
PARAMETER
CONDITIONS
MIN
(4)
TYP
(5)
MAX
(4)
UNIT
POWER SUPPLY
IV+
Supply Current
Does not include external currents
such as LED, SWDRV, and LC tank
current (6) (3)
IBURN
Burn Current
Additional current needed to burn
registers
tSTART
Power On Start Time
LC Tank oscillation = 1MHz,
RESPONSE_TIME = 001b (96),
measured time starting from when
supply is at 90% of operational
value. (7)
3
mA
3.6
mA
50
ms
OSCILLATOR
fMIN
Minimum Oscillation Frequency
0.005
MHz
fMAX
Maximum Oscillation Frequency
5
MHz
OSCAMP1V Oscillator Amplitude
OSC_AMP = 00b
1
VPP
OSCAMP2V Oscillator Amplitude
OSC_AMP = 01b
2
VPP
OSCAMP4V Oscillator Amplitude
OSC_AMP = 10b
4
VPP
trec
Recovery Time
Oscillation start up time after low RP
is removed.
10
oscillator
periods
RPMIN
Minimum RP Value of LC Tank
See OSC_CONFIG_2 entry in the
Register Maps section.
798
RPMAX
Maximum RP Value of LC Tank
See OSC_CONFIG_2 entry in the
Register Maps section.
3.93M
Response time
Settling time of digital filter to RP
step. See RESPONSE_TIME in
registers 0x71 and 0x77.
SENSOR
Ω
Ω
DETECTOR
tRESP
96
6144
oscillator
periods
OUTPUT DRIVER
ISOURCE,
SINK
Current source and sink capability on
SWDRV Terminal
SWDRV_CURRENT = 00b
2
2.5
3
SWDRV_CURRENT = 01b
3.25
3.75
4.25
SWDRV_CURRENT = 10b
4.5
5
5.5
SWDRV_CURRENT = 11b
9
10
11
mA
OVERLOAD PROTECTION
(1)
(2)
(3)
(4)
(5)
(6)
(7)
6
Over Current Detection Threshold
NPN Configuration, Using external
SENSE resistor
279
310
341
Over Current Detection Threshold
PNP Configuration, Using external
SENSE resistor
248
310
376
Over Current Limit
NPN Configuration
432
480
528
mV
Over Current Limit
PNP Configuration
413
480
547
mV
mV
mV
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. Parametric performance shown in the electrical tables is not ensured
under conditions of internal self-heating where TJ > TA.
Electrical Characteristics apply only when SWIF is inactive. Glitches may appear on SWDRV during a SWIF transmission.
There are tradeoffs between power consumption, switching speed, RP to Digital conversion and oscillation frequency.
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 ensured on shipped
production material.
Supply current is higher when there is not an LC tank connected to Terminals INA and INB because an internal protection circuit is
enabled. See the Supply Current vs Supply Voltage graphs in the Typical Characteristics section.
The loop supply must be able to momentarily supply 30mA.
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Electrical Characteristics (1)(2) (continued)
Unless otherwise specified, all limits are ensured at TA = TJ = 25°C, Loop Voltage = 24V.(3). Boldface limits apply at the
temperature extremes.
SYMBOL
PARAMETER
CONDITIONS
MIN
(4)
TYP
MAX
UNIT
30
35
µs
(5)
(4)
INPUT SHORT CONDITION
tOUT
Output Switching
Output high time in short condition
duty0.1%
Output duty cycle during short
condition
During short,
SHORTCKT_DUTY_CYCLE = 0b
25
0.1%
duty0.8%
Output duty cycle during short
condition
During short,
SHORTCKT_DUTY_CYCLE = 1b
0.8%
LEDBLINK
LED Blinking Rate
Blinking rate of the LED during a
short condition or ECC error
2
Hz
LED DRIVER
Sink Current
LED_CURRENT = 0b
2
2.5
3
mA
Sink Current
LED_CURRENT = 1b
4
5
6
mA
-2.5
1
2.5
TEMPERATURE SENSOR
Accuracy
Accuracy of the LMP91300 only,
does not include the accuracy of
the NTC
°C
6.6 Timing Requirements
SWIF TIMING
MIN
Communication rate
TYP
1
“D” symbol duty cycle: THD/TP
½
“0” symbol duty cycle: TH0/TP
¼
“1” symbol duty cycle: TH1/TP
¾
MAX
UNIT
10
kbits/s
³0´
TH0
³'´
THD
³1´
TH1
TP
Figure 1. Single-Wire Interface (SWIF) Timing Diagram
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6.7 Typical Characteristics
At TA = TJ = 25°C, Loop Voltage = 20V to 36V, unless otherwise specified.
14500
5.0
Temperature Sensor Accuracy
4.0
14000
3.0
Accuracy (C)
RP (Dec)
13500
13000
12500
Register Settings
RP_MAX = 0x12
RP_MIN = 0x18
RESONATOR_MIN_FREQ = 0x91
OSC_AMP = 4V
RESPONSE_TIME = 6144
12000
11500
3.959mm
5000
10000
15000
25000
0.0
±1.0
±3.0
4.04mm
20000
1.0
±2.0
4mm
±4.0
11000
0
2.0
30000
Samples
Using Murata NTC: NCP03WF104F05RL
±5.0
±40.0 ±20.0
20.0
40.0
60.0
80.0 100.0 120.0
Temperature (C)
Figure 2. RP Resolution
C004
Figure 3. Temperature Accuracy
4.5
4.5
LC Tank connected to INA and INB
RP_MAX = 0x12
RP_MIN = 0x18
RESONATOR_MIN_FREQ = 0x91
OSC_AMP = 1V
LC Tank Oscillation Frequency with
no Target = 317kHz
3.5
LC Tank connected to INA and INB
RP_MAX = 0x12
RP_MIN = 0x18
RESONATOR_MIN_FREQ = 0x91
OSC_AMP = 2V
LC Tank Oscillation Frequency with
no Target = 317kHz
4.0
Supply Current (mA)
4.0
Supply Current (mA)
0.0
C003
-40C
3.0
+25C
2.5
3.5
-40C
3.0
+25C
2.5
+85C
+85C
+125C
+125C
2.0
2.0
5
10
15
20
25
30
35
Supply (V)
40
5
10
Figure 4. Supply Current vs Supply Voltage
15
20
25
30
35
Supply (V)
C005
40
C005
Figure 5. Supply Current vs Supply Voltage
4.5
-40C
SENSE- Pin
+25C
Supply Current (mA)
4.0
SWDRV Pin
+85C
3.5
2mA/DIV
+125C
LC Tank connected to INA and INB
RP_MAX = 0x12
RP_MIN = 0x18
RESONATOR_MIN_FREQ = 0x91
OSC_AMP = 4V
LC Tank Oscillation Frequency with
no Target = 317kHz
3.0
2.5
200mV/DIV
2.0
5
10
15
20
25
30
35
Supply (V)
C001
C005
Figure 6. Supply Current vs Supply Voltage
8
10µs/DIV
40
Figure 7. SWDRV and SENSE- Waveforms During Short
Condition, SHORTCKT_DUTY_CYCLE = 0.1% Or 0.8%
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Typical Characteristics (continued)
At TA = TJ = 25°C, Loop Voltage = 20V to 36V, unless otherwise specified.
600
400
Loop Voltage = 24V
Frequency (Count)
250
200
150
100
350
300
250
200
150
Duty Cycle (%)
0.1
0.09998
0.09996
0.09992
0.0999
0.09988
0.09986
0.09994
Duty Cycle (%)
C013
Figure 10. 0.8% Duty Cycle Distribution, PNP Mode
0.8
0.7998
0.7996
0.7994
0.8
0.7998
0.7996
0.7994
0.7992
0.799
0.7988
0.7986
0.7984
50
0.7992
100
0.799
150
0.7988
200
0.7986
250
Loop Voltage = 24V
0.7984
300
700
650
600
550
500
450
400
350
300
250
200
150
100
50
0
0.7982
Frequency (Count)
400
0.7982
0.09984
Figure 9. 0.1% Duty Cycle Distribution, NPN Mode
Loop Voltage = 24V
350
C012
Duty Cycle (%)
Figure 8. 0.1% Duty Cycle Distribution, PNP Mode
0.798
0.09982
C011
500
450
0.0998
0
0.1
0.09998
0.09996
0.09994
0.09992
0.0999
0.09988
0.09986
0.09984
0.09982
0.0998
50
Duty Cycle (%)
Frequency (Count)
400
100
50
0
450
0.798
Frequency (Count)
500
300
0
Loop Voltage = 24V
550
350
C014
Figure 11. 0.8% Duty Cycle Distribution, NPN Mode
SENSE- Pin
SWDRV Pin
2mA/DIV
200mV/DIV
2ms/DIV
C009
Figure 12. SWDRV and SENSE- Waveforms During Short Condition, SHORTCKT_DUTY_CYCLE = 0.1%
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SENSE- Pin
SWDRV Pin
2mA/DIV
200mV/DIV
500µs/DIV
C010
Figure 13. SWDRV and SENSE- Waveforms During Short Condition, SHORTCKT_DUTY_CYCLE = 0.8%
10
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7 Detailed Description
7.1 Overview
The LMP91300 is a complete analog front end (AFE) optimized for use in inductive proximity sensors. The
LMP91300 detects the presence of a metal object based on the RP change of an LC oscillator, depending on the
distance of the metal object.
The LMP91300 is based on a novel architecture that directly converts the RP of the external LC tank to a digital
value. Post manufacturing configuration and calibration is fully supported by the architecture of the LM91300.
The temperature dependence of the sensor is digitally compensated, using an external temperature sensor. The
LMP91300 provides programmable thresholds, programmable temperature compensation and programmable
oscillation frequency range. Due to its programmability, the LMP91300 can be used with a wide variety of
external inductors and its detection thresholds can be adjusted to the desired detection distances. The internal
LDO has a high input voltage capability, while the architecture enables the use of a low supply as well. The
output can be programmed to drive an external transistor in either NPN or PNP mode.
EXT B
V+/EXT E
7.2 Functional Block Diagram
OTP Memory
Direct RP to
Digital Converter
Digital Temp
Correction
TEMP
CFB
CFA
Temp
Sensor
Comparator
SENSE1+
SENSE1+
SENSE2+
SENSE2+/
SWIF RX
Driver
LED
Drive
Serial
Interface
DRIVE
SWDRV
SENSE-
SENSE-
GND
INB
CBY
Oscillator
LED
INA
Voltage Regulator
7.3 Feature Description
7.3.1 Oscillator
The oscillator, using an external LC tank (the detector), provides a wide oscillation range from 5kHz to 5MHz.
The RP upper and lower limits are programmable, to support a wide range of LC combinations. Within the RP
range of the LC tank, the oscillator amplitude is kept constant. When the LC tank RP drops below the lower
programmed limit of RP the LMP91300 detects that the target is too close, the amplitude is reduced and the
detector output will rail. See Figure 14.
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Feature Description (continued)
Oscillator
dies
Normal
operation
ADC saturated,
RXWSXWLQJ³RQHV´
ADC saturated,
2XWSXWLQJ³]HURV´,
Oscillator running
Switch opens
Switch closes
Hysteresis
1
2
RP = 1.25k
RP_MIN
Threshold open
4
RP_MAX
RP = 5M
Threshold close
ADC Out
Full Scale
3
0
0
f
Distance to target :
Figure 14. Operating Region
7.3.2 Detection
The RP of the external LC tank is directly converted to a digital signal. With this approach the only temperature
compensation needed is that for RP, which is done through the Look Up Table (Registers 0x00 to 0x5D).
7.3.3 Comparator
The internal digital comparator accepts the signal from the RP to digital converter, after temperature
compensation, and makes a decision, based on the value written to the DET_H_MSB and DET_H_ LSB
registers. Programmable hysteresis is set by the value in the DET_L_MSB and DET_L_ LSB registers. The
detection threshold can be set within the programmed RP range.
7.3.4 Low RP, Close Target, Under Range Switch Enable
If RP drops below the detectable range, the LMP91300 remains functional. The following applies if at least one
temperature conversion has been completed:
For low RP start up (for example, if the target is in contact with the sensing coil when the part is powered on)
UNDER_RANGE_SWITCH_EN must be set to 1 for the switch to be enabled. If UNDER_RANGE_SWITCH_EN
is set to 0, the startup state is undefined when the sensor RP < RPMIN (for example, if the target is in contact with
the sensing coil).
1. If RP < 798Ω (for example, the metal plate is against the sensor) before the fourth conversion of the RP to
digital converter (after Power On Reset) the switch will be activated regardless of the
UNDER_RANGE_SWITCH_EN setting.
2. If RP < 798Ω after the fourth conversion the switch state depends on the setting of
UNDER_RANGE_SWITCH_EN.
(a) If UNDER_RANGE_SWITCH_EN = 1: The switch will be enabled.
(b) If UNDER_RANGE_SWITCH_EN = 0: The previous switch state will be held until the oscillation restarts
(RP > 798Ω) and enough time has passed for a conversion to update the switch status.
If a temperature conversion has not been completed the switch state will not be changed.
The LMP91300 oscillator will begin to oscillate in less than 10 oscillator periods once the low RP condition is
removed.
12
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Feature Description (continued)
7.3.5 Programming The Switching Point And Hysteresis
The typical procedure is that the user puts a target metal at the target distance in front of the manufactured
sensor system. The PROXIMITY_MSB and Proximity LSB registers are read and the DET_H_MSB and DET_H_
LSB registers are written with a value that causes the LMP91300 to switch. The metal target is then moved to
another distance, farther away than the first distance, the PROXIMITY_MSB and Proximity LSB registers are
read and a value is written to the DET_L_MSB and DET_L_ LSB registers that causes the LMP91300 to switch
the external transistor off.
7.3.6 Temperature Compensation
As most of the integrated electronics are in the digital domain, close to perfect performance of the LMP91300
over temperature can be expected. As the RP factor of the external LC tank is measured, only the temperature
coefficient of the LC tank losses need to be compensated for. The LMP91300 offers a digital temperature
compensation feature that provides an accurate RP detection of the external LC tank when losses are introduced
due to ambient temperature changes in the operating environment. This can be done by calibrating the
Temperature Look-Up Table (LUT) located in registers 0x00 to 0x5D. The calibration involves the user
generating gain correction factor coefficients (GCF) and is discussed in detail in the Look-Up Table Calibration
section. These registers hold 2 bytes of information representing temperatures ranging from -48°C to 136°C in
4°C increments. The LMP91300 uses linear interpolation to provide 1°C temperature steps in between these 4°C
points to improve accuracy. After the LUT has been properly programmed, the Detection Threshold registers
need to be programmed for the switching distances desired. The external temperature sensor and the
temperature coefficients stored in the LUT produce a functional temperature compensation system. The LUT was
designed for an NTC with a beta factor β = 4250 such as the Murata NCP03WF104F05RL. Any other NTC used
in the design will require additional adjustments which are explained in the Look-Up Table Calibration section.
7.3.7 Power Supply
An internal regulator with an external NPN transistor is used to power the LMP91300 directly from the loop.
7.3.8 LED Drive
An external LED can be driven with the LED terminal. Red and Green LEDs are supported. The LED current can
be programmed to 2.5mA or 5 mA. This LED indicates the state of the sensor. Typically the LED is on if the
switch is closed, but this is programmable in the OUT_CONFIG_INIT and OUT_CONFIG_FNL registers. This
LED will also indicate an output overload condition situation or ECC error.
7.3.9 SWDRV
The LMP91300 drives an external transistor, to implement a NPN or PNP function. During power up the drive
terminal (SWDRV) is pulled down using a high resistance to avoid turning on the external transistor, until the
LMP91300 is fully functional.
7.3.10 Overload Protection
Short circuit detection and overload protection are implemented in the LMP91300, using an external SENSE
resistor, RSENSE. When the voltage drop across RSENSE exceeds about 310 mV the LMP91300 detects a short
circuit condition. If this condition persists, the switch is toggled between being open and closed. The switch will
be on for about 30µs, with a duty cycle as set in OUT_CONFIG_INIT (0x72) bit 0 (SHORTCKT_DUTY_CYCLE)
or OUT_CONFIG_FNL (0x78) bit 0 (SHORTCKT_DUTY_CYCLE) to protect the external BJT. For example, if
SHORTCKT_DUTY_CYCLE is set to 0.1% the switch drive will be on for 30µs and off for 29.97ms (tOFF =
(30µs/0.1%) - 30µs). During a short circuit event, the load current is limited to I=480mV/RSENSE. The LMP91300
will come out of the overload protection mode once the drop across RSENSE is less than 310mV.
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Feature Description (continued)
When designing the overload protection circuitry the user must select the appropriate transistors, SWDRV
current setting, RSENSE resistor and short circuit duty cycle. The transistor should be selected to handle the load
current and supply voltage both during normal operation and during an overload situation to ensure that it
remains in the safe operating region at all times. The RSENSE resistor should be chosen to set the current limit
and over current threshold. The SWDRV current should be selected to ensure that during a short circuit condition
the SWDRV current is capable of sourcing or sinking the programmed current depending on NPN or PNP
configuration. This ensures that the short circuit control loop remains regulated and enforces the current limit and
over current threshold. Once overload protection design is complete the user has the option to choose between
the two duty cycle options.
7.4 Device Functional Modes
NPN and PNP 3 wire configurations as shown in the Typical Application section are supported by the LMP91300.
7.5 Programming
Through the 2-wire loop connection, all parameters such as the LUT, operation modes, output modes and
detection thresholds can be programmed after the sensor manufacturing process is finished. The LMP91300 is
one time programmable in a 3 step process. During the manufacturing process the configuration and calibration
data will be written to the device and then a special code will be written that disables communication.
7.5.1 Burning Programmed Values Into The Registers
There are three steps to burning values into the registers.
1. Burn the Temperature Look Up Table data (0x00 – 0x5D), initial registers, device information registers, and
configuration registers (0x66 – 0x72).
(a) Use SWIF to program values into these registers (0x00 – 0x72).
(b) Use SWIF to write 0x08 to register 0x7F to permanently burn the values into the registers.
(c) Optional: Wait 300ms and read back the status register (0x7E). It should read 0x21 if the registers have
been successfully burned.
2. Burn final registers (0x73 – 0x78).
(a) Use SWIF to program values into these registers (0x73 – 0x78).
(b) Use SWIF to write 0x10 to register 0x7F to permanently burn the values into the registers.
(c) Optional: Wait 300ms and read back the status register (0x7E). It should read 0x23 if the registers have
been successfully burned.
3. Burn SWIF mode. After the device has been programmed the write function using SWIF needs to be
disabled.
(a) Read Only. The SWIF write function is disabled but registers can still be read back using SWIF. Use
SWIF to write 0x40 to address 0x7F. After the device is power cycled it will be read only.
(b) Disabled. The SWIF is completely disabled, both write and read functions are disabled. Use SWIF to
write 0x80 to address 0x7F. After the device is power cycled SWIF will be disabled.
(c) Optional: Before power cycling the device wait 300ms and read back the status register (0x7E). It should
read 0x27 for read only or 0x2F for SWIF disabled.
4. 4. It is possible to combine steps 1 and 2 and burn the Look Up Table, initial registers, device information
registers, configuration registers, and final registers (0x00 – 0x78) at one time.
(a) Use SWIF to program values into these registers (0x00 – 0x78).
(b) Use SWIF to write 0x20 to register 0x7F to permanently burn the values into the registers.
(c) Optional: Wait 300ms and read back the status register (0x7E). It should read 0x23 if the registers have
been successfully burned.
14
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Programming (continued)
7.5.2 Single-Wire Interface (SWIF)
The LMP91300 uses a bi-directional Single Wire Interface protocol to program and read registers. To
communicate with the LMP91300 (slave) through the SWIF interface, the micro controller (master) must transmit
(write) data through the DC loop supply voltage that should be set to +8V during programming or communication.
This superimposed signal of pulses transitions between 8V and 12V is on top of the +8V DC loop supply voltage.
When the master transmits data into the LMP91300 the signal propagates into the SENSE2+ terminal through
the supply. The master receives data from the LMP91300 through the LED terminal in the form of alternating
current pulses. These current pulses will be 5mA in amplitude. The LED terminal must be connected to ground,
either through an LED or directly connected to ground for the LMP91300 to talk to the master.
The communication scheme utilizes various pulse width waveforms to represent different symbols as shown in
Figure 15. The binary representation of a zero bit is represented by a 25% pulse duty cycle, a one bit is
represented by a 75% pulse duty cycle, and idle bit is represented by a 50% duty cycle. All pulses transmitted
must fall within the pulse width specifications provided within the electrical characteristics table.
ZERO Bit
IDLE Bit
ONE Bit
1 Time Unit
1 Time Unit
1 Time Unit
25% Duty Cycle
50% Duty Cycle
75% Duty Cycle
Figure 15. Single Wire Interface (SWIF) Symbol Diagram
The LMP91300 can be programmed at an input transfer bit rate between 1kbps to 10kbps. There is no
acknowledge signal during the input data transfer so the master should read back the data to ensure data
integrity and a successful data transfer has occurred. A read transaction is executed by the master transmitting
data to configure the pointer register resulting in data output transfer by the slave. The LMP91300 transmits read
back data at a speed of about 7kbps.
7.5.2.1 Write Operation
A frame begins with a minimum of one IDLE bit. To perform a write operation, the master must send an IDLE bit
followed by the R/W bit set to 0 and the 7-bit address of the register that is intended to be programmed. The data
to be written into the address location follows with the Most Significant Bit first and the write operation is
terminated with an IDLE bit. There are 8 bits in each data byte and the maximum number of data bytes can be
up to 8 bytes. Data being transmitted from the master to the slave can be terminated by the master by sending
an IDLE bit after any data byte. After communication, to initiate another communication, the master must transmit
another IDLE. When an invalid bit that violates the SWIF symbol protocol is transferred, the SWIF will reset and
wait for the IDLE bit.
k: The total number of
bytes, k = 8 (max)
Complete frame for a Write Operation
8*k bits
8 bits
IDLE
R/W = 0
8 bits
7-bit Address
D7
DATA
C DATA
D0
IDLE
Figure 16. Complete Frame For A Write Command
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Programming (continued)
7.5.2.2 Read Operation
The read signal is made by modulating the supply current. This can be read by using a SENSE resistor in the
supply line. The LMP91300 modulates the supply current by sinking current into the LED terminal. The V+/EXT
and LED terminals need to be connected by either an LED, resistor, or directly shorted for the Read operation to
work. To perform a read operation, the master must send an IDLE bit to initiate communication, a R/W bit that
should be set to 1, a 7-bit address, and another IDLE bit. Data is written back after the R/W and address byte are
received so there must be a 9th rising edge to ensure that this condition is satisfied. After the last bit, A0, of the
address is sent there should only be one rising edge to perform the IDLE bit. There are two valid methods of
providing one rising edge, (1) a single pulse, or (2) a rising edge with the signal held high. See Figure 17 for a
timing example of both cases.
9TH Rising Edge
IDLE
IDLE
7-bit Address
R/W = 1
A6
A5
A4
A3
A2
A1
A0
(1)
R/W = 1
A6
A5
A4
A3
A2
A1
A0
(2)
End of Read Command: LMP91300
Enters Transmit Mode
Start of Read Command
Figure 17. Read Timing Example: (1) Single Pulse, (2) Hold Signal High After Last Rising Edge
The LMP91300 goes into transmit mode 10μs plus a symbol length after the IDLE rising edge and no longer
accepts any data until transmission is done. The master is not allowed to send anything until the slave has
finished sending the data. Data is always written back on a read command with an IDLE bit, 8 bytes of data, and
another IDLE bit. All transmitting is done in 8 byte blocks with the exception that only one byte is transmitted
when the STATUS register (0x7E) is read. Since data transfer is always 8 bytes maximum (except for when
register 0x7E, STATUS is read), there is a maximum wait time (8 bits*8 bytes + IDLE + IDLE + 10us) that the
master must wait before taking ownership of the bus. The amount of time it takes for SWIF to switch from input
to output is about one symbol.
k: The total number of
bytes, k = 8 (max)
Complete frame for a Read Operation
8 bits
IDLE
R/W = 1
7-bit Address
Symbol + 10 s
IDLE
Master Initiates a Read Operation
8*k bits
8 bits
IDLE
D7
DATA
D0
C DATA
IDLE
LMP91300 Enters Transmit Mode and Returns DATA
Figure 18. Complete Frame For A Read Command
The user has the option to set the LMP91300 into a read-only mode or SWIF disabled mode. When placed in
read-only mode, the SWIF can only be used to read back the registers but all write capability is disabled. When
placed in SWIF disabled mode, both read and write capabilities are disabled.
16
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Programming (continued)
7.5.3 Usage Priority Of Registers
When a LMP91300 is powered on the register values that are used depends on if the LMP91300 has had values
burned into the registers. See register 0x7F, BURN_REQ.
1. No values have been burned into registers:
(a) When powered on the LMP91300 will use the default values in registers 0x00-0x5D and 0x66-0x72.
(b) If a value is written to any of these registers (0x00-0x5D and 0x66-0x72) the LMP91300 will use the
value written instead of the power on default value.
(c) If a value is written into a FNL register (0x73-0x78) the LMP91300 will continue to use the value in the
INIT register instead of the corresponding FNL register. For example, if register OSC_CONFIG_3_FNL
(0x77) has a value written to it, the LMP91300 will continue using the OSC_CONFIG_3_INIT (0x71)
register and not use the value in the OSC_CONFIG_3_FNL (0x77) register.
(d) If the LMP91300 is powered off and back on it will use the default values in registers 0x00-0x5D and
0x66-0x72.
2. Values have been burned into the LMP91300 memory using burn request 0x08.
(a) When powered on the LMP91300 will use the burned values in registers 0x00-0x5D and 0x66-0x72.
(b) If a value is written to any of these registers (0x00-0x5D and 0x66-0x72) the LMP91300 will use the
written value instead of the burned value.
(c) If a value is written into a FNL register (0x73-0x78) the LMP91300 will continue to use the value in the
INIT register instead of the corresponding FNL register. For example, if register OSC_CONFIG_3_FNL
(0x77) has a value written to it, the LMP91300 will continue using the OSC_CONFIG_3_INIT (0x71)
register and not use the value in the OSC_CONFIG_3_FNL (0x77) register.
(d) If the LMP91300 is powered off and back on the LMP91300 will use the burned values in registers 0x000x5D and 0x66-0x72.
3. Values have been burned into the LMP91300 memory using burn request 0x10 or 0x20.
(a) When powered on the LMP91300 will use the burned values in registers 0x00-0x5D, 0x6A-0x70 and
0x73-0x78.
(b) If a value is written to an INIT register (0x66-0x69, 0x71-0x72) it will be ignored and the corresponding
FNL register (0x73-0x78) will be used.
(c) If a value is written to a FNL register (0x73-0x78) the LMP91300 will use the written value instead of the
burned value.
(d) If the LMP91300 is powered off and then back on the LMP91300 will use the burned values in registers
0x00-0x5D, 0x6A-0x70 and 0x73-0x78.
It is important to remember that the LMP91300 will always use the values in the initial registers (either temporary
written values or permanently burned values) if the final registers have not had values burned into them. If the
final registers have had values burned into them, the LMP91300 will always use the final registers (either the
permanently burned value or a value that has been temporally written in a final register).
The burn status of the LMP91300 can be determined by reading the STATUS register (0x7E) as long as a 0x80
burn request has not been issued.
Each register can only have a value burned into it one time. It is not possible to burn a value into a register
multiple times.
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7.6 Register Maps
Name
Description
Address
Type
Default
LUT_x_GAIN_MSB, LSB
Temperature Look Up Table, -48°C to
+136°C in 4°C steps, 2 bytes - gain
0x00-0x5D
RW
0x40 - even addresses,
0x00 - odd addresses
RESERVED
Reserved
0x5E-0x65
RO
0x00
DET_H_MSB_INIT
Detection High Threshold MSB (Initial)
0x66
RW
0x00
DET_H_LSB_INIT
Detection High Threshold LSB (Initial)
0x67
RW
0x00
DET_L_MSB_INIT
Detection Low Threshold MSB (Initial)
0x68
RW
0x00
DET_L_LSB_INIT
Detection Low Threshold LSB (Initial)
0x69
RW
0x00
INFO0
Device Information 0
0x6A
RW
0x00
INFO1
Device Information 1
0x6B
RW
0x00
INFO2
Device Information 2
0x6C
RW
0x00
INFO3
Device Information 3
0x6D
RW
0x00
OSC_CONFIG_0
Oscillator Configuration 0
0x6E
RW
0x0E
OSC_CONFIG_1
Oscillator Configuration 1
0x6F
RW
0x14
OSC_CONFIG_2
Oscillator Configuration 2
0x70
RW
0x45
OSC_CONFIG_3_INIT
Oscillator Configuration 3 (Initial)
0x71
RW
0x1B
OUT_CONFIG_INIT
Output Configuration (Initial)
0x72
RW
0xA2
DET_H_MSB_FNL
Detection High Threshold MSB (Final)
0x73
RW
0x00
DET_H_LSB_FNL
Detection High Threshold LSB (Final)
0x74
RW
0x00
DET_L_MSB_ FNL
Detection Low Threshold MSB (Final)
0x75
RW
0x00
DET_L_ LSB_ FNL
Detection Low Threshold LSB (Final)
0x76
RW
0x00
OSC_CONFIG_3_FNL
Oscillator Configuration 3 (Final)
0x77
RW
0x1B
OUT_CONFIG_FNL
Output Configuration (Final)
0x78
RW
0xA2
TEMP64
Temperature in °C + 64
0x79
RO
NA
PROXIMITY_MSB
Proximity MSB
0x7A
RO
NA
PROXIMITY_LSB
Proximity LSB
0x7B
RO
NA
RESERVED
Reserved
0x7C-0x7D
RO
0x00
STATUS
Device Status
0x7E
RO
NA
BURN_REQ
Burn Request
0x7F
WO
NA
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Register Maps (continued)
DET_H_MSB_INIT – Detection High Threshold MSB (Initial) (Address 0x66)
Bit
Name
Function (Default values in bold)
[7:0]
DET_H_MSB_INIT
0x00: Detection High Threshold MSB (Initial)
See the Usage Priority Of Registers section.
A starting value to put in the DET_H_MSB_INIT and DET_H_LSB_INIT registers can be determined by first
setting the correct values in the OSC_CONFIG_0, OSC_CONFIG_1, OSC_CONFIG_2, OSC_CONFIG_3_INIT,
OUT_CONFIG_INIT registers, putting the target at the distance away from the target that it is supposed to switch
on at, reading the values in the PROXIMITY_MSB and Proximity LSB registers, and writing these values into the
DET_H_MSB_INIT and DET_H_LSB_INIT registers. This value can be then adjusted as needed.
DET_H_LSB_INIT – Detection High Threshold LSB (Initial) (Address 0x67)
Bit
Name
Function (Default values in bold)
[7:0]
DET_H_LSB_INIT
0x00: Detection High Threshold LSB (Initial)
See the Usage Priority Of Registers section.
DET_L_MSB_INIT – Detection Low Threshold MSB (Initial) (Address 0x68)
Bit
Name
Function (Default values in bold)
[7:0]
DET_L_MSB_INIT
0x00: Detection Low Threshold MSB (Initial)
See the Usage Priority Of Registers section.
A starting value to put in the DET_L_MSB_INIT and DET_L_LSB_INIT registers can be determined by first
setting the correct values in the OSC_CONFIG_0, OSC_CONFIG_1, OSC_CONFIG_2, OSC_CONFIG_3_INIT,
OUT_CONFIG_INIT registers, putting the target at the distance away from the target that it is supposed to switch
off at, reading the values in the PROXIMITY_MSB and Proximity LSB registers, and writing these values into the
DET_L_MSB_INIT and DET_L_LSB_INIT registers. This value can be then adjusted as needed.
DET_L_LSB_INIT – Detection Low Threshold LSB (Initial) (Address 0x69)
Bit
Name
Function (Default values in bold)
[7:0]
DET_L_LSB_INIT
0x00: Detection Low Threshold LSB (Initial)
See the Usage Priority Of Registers section.
INFO0 – Device Information 0 (Address 0x6A)
Bit
Name
Function (Default values in bold)
[7:0]
INFO0
0x00: Device Information 0
This register can be used to store information such as assembly date, model number, revision number or any
other data.
INFO1 – Device Information 1 (Address 0x6B)
Bit
Name
Function (Default values in bold)
[7:0]
INFO1
0x00: Device Information 1
This register can be used to store information such as assembly date, model number, revision number or any
other data.
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INFO2 – Device Information 2 (Address 0x6C)
Bit
Name
Function (Default values in bold)
[7:0]
INFO2
0x00: Device Information 2
This register can be used to store information such as assembly date, model number, revision number or any
other data.
INFO3 – Device Information 3 (Address 0x6D)
Bit
Name
Function (Default values in bold)
[7:0]
INFO3
0x00: Device Information 3
This register can be used to store information such as assembly date, model number, revision number or any
other data.
OSC_CONFIG_0 – Oscillator Configuration 0 Register (Address 0x6E)
Bit
Name
Function (Default values in bold)
[7:5]
Reserved
000
[4:0]
RP_MAX
01110: Maximum RP, logarithmic scale
The optimal setting for RP_MAX is the highest value for which the correct amplitude is maintained, with the
target set at the maximum switching distance.
1. Determine RLCTANK as shown in the Determining The RP of an LC Tank section.
2. Multiply RPLCTANK by 2 and use the next higher value from the chart below. For example, if RPLCTANK
measured at 4mm is 11113, 11113x2 = 22226, so 12 (27704) would be used for RP_MAX.
3. This value can be adjusted up or down as needed.
Register Setting
(Hex)
RP (Ω)
Register Setting
(Hex)
RP (Ω)
Register Setting
(Hex)
RP (Ω)
0
3926991
B
193926
16
9235
1
3141593
C
145444
17
7182
2
2243995
D
109083
18
5387
3
1745329
E
83111
19
4309
4
1308997
F
64642
1A
3078
5
981748
10
48481
1B
2394
6
747998
11
38785
1C
1796
7
581776
12
27704
1D
1347
8
436332
13
21547
1E
1026
9
349066
14
16160
1F
798
A
249333
15
12120
20
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OSC_CONFIG_1 – Oscillator Configuration 1 Register (Address 0x6F)
Bit
Name
Function (Default values in bold)
[7:5]
PADC_TIMEC
000: Sensor time constant range
[4:0]
RP_MIN
10100: Minimum RP, logarithmic scale
The PADC_TIMEC (time constant), sets the damping of the readout circuitry. The higher this Parameter is set,
the more damping it has. If programmed to zero (0), it has no damping, and the system is almost unstable. The
oscillation amplitude (envelope) will vary a lot. If this parameter is set to max (7), the damping is maximum, but
that also means the response becomes slow. The optimal setting is what in control theory is called "critical
damping", that is the least damping required to prevent overshoot in the step response. In most cases set
PADC_TIMEC = 1.
The optimal setting for RP_MIN is the highest value for which the correct amplitude is maintained, with the target
at the minimum switching distance. Some margin is given to the value.
1. Determine RPLCTANK as shown in the Determining The RP of an LC Tank section.
2. Divide the RPLCTANK value by 2 and then select the next lower RP value from the chart above. For example, if
the finished Proximity Sensor is to detect at 4mm and the RPLCTANK measured at 4mm is 11113, 11113/2 =
5556.5, so 18 (5387) would be used for RP_MIN.
3. This value can be adjusted up or down as needed.
OSC_CONFIG_2 – Oscillator Configuration 2 Register (Address 0x70)
Bit
Name
Function (Default values in bold)
[7:0]
RESONATOR_MIN_FREQ
01000101: Minimum frequency setting, logarithmic scale
Determine the minimum oscillation frequency (fMIN) of the LC tank. This is when there is no target in front of the
LC tank. Calculate a value 20% below the minimum oscillation frequency, f80% = fMIN x 0.8. Use the following
formula to calculate the value for RESONATOR_MIN_FREQ:
f80%
2000
255 ×
log 5000
log
(1)
Take this value, round up to the next integer and convert to hex.
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OSC_CONFIG_3_INIT – Oscillator Configuration 3 Register (Initial) (Address 0x71)
Bit
Name
Function (Default values in bold)
[7:6]
RESERVED
00
[5]
UNDER_RANGE_SWITCH_EN
0: Off
1: On
[4:3]
OSC_AMP
00: 1V
01: 2V
10: 4V
11: Reserved
[2:0]
RESPONSE_TIME
000: Reserved
001: 96
010: 192
011: 384
100: 768
101: 1536
110: 3072
111: 6144
See the Usage Priority Of Registers section.
UNDER_RANGE_SWITCH_EN: The following applies if at least one temperature conversion has been
completed:
1. If RP < 798Ω (for example, the metal plate is against the sensor) before the fourth conversion of the RP to
digital converter (after Power On Reset) the switch will be activated regardless of the
UNDER_RANGE_SWITCH_EN setting.
2. If RP < 798Ω after the fourth conversion the switch state depends on the setting of
UNDER_RANGE_SWITCH_EN.
(a) If UNDER_RANGE_SWITCH_EN = 1: The switch will be enabled.
(b) If UNDER_RANGE_SWITCH_EN = 0: The previous switch state will be held until the oscillation restarts
(RP > 798Ω) and enough time has passed for a conversion to update the switch status.
If a temperature conversion has not been completed the switch state will not be changed.
OSC_AMP: The oscillation amplitude at terminals INA and INB can be set to 1V, 2V, or 4V. If the LMP91300 has
not been burned with user values, the power on value for OSC_AMP is 11: Reserved. This will need to be
changed to either 1V, 2V or 4V before the LMP91300 is used.
RESPONSE_TIME: Using a lower response time will shorten the settling time of the digital filter and give faster
readings from the RP to digital converter but will increase the noise in the reading. A higher setting gives the
digital filter more time to settle and will decrease the noise in the reading.
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OUT_CONFIG_INIT – Output Configuration Register (Initial) (Address 0x72)
Bit
Name
Function (Default values in bold)
[7:6]
SWDRV_CURRENT
00: 2.5mA
01: 3.75mA
10: 5mA
11: 10mA
5
OUTPUT_MODE
0: 3-Wire NPN
1: 3-Wire PNP
4
DRIVE_MODE
0: Normally open
1: Normally closed
3
LED_ENABLE
0: On
1: Off
2
LED_MODE
0: Normally off
1: Normally on
1
LED_CURRENT
0: 2.5mA
1: 5mA
0
SHORTCKT_DUTY_CYCLE
0: 0.1%
1: 0.8%
See the Usage Priority Of Registers section.
SWDRV_CURRENT: Used to set the amplitude of current from the SWDRV terminal used to control the external
transistor.
DRIVE_MODE: Normally open and normally closed refer to the external NPN or PNP switch when a target is far
away from the inductive sensor. When the switch is normally open the transistor is not conducting when the
target is far away from the target (the distance is greater than the value in DET_L_MSB and DET_L_ LSB). The
switch is conducting when the target is close to the sensor (the distance is less than the value in DET_H_MSB
and DET_H_ LSB). When the switch is normally closed the transistor is conducting when the target is far away
from the target (the distance is greater than the value in DET_L_MSB and DET_L_ LSB). The switch is not
conducting when the target is close to the sensor (the distance is less than the value in DET_H_MSB and
DET_H_ LSB).
LED_ENABLE: When set to On the LED will function as set in Bit 2, LED_MODE. When set to Off the LED will
always be off.
LED_MODE: Normally off means that the LED is off when the target is far away from the sensor (the distance is
greater than the value in DET_L_MSB and DET_L_ LSB). The LED will turn on when the target is close (the
distance is less than the value in DET_H_MSB and DET_H_ LSB). Normally on means that the LED is on when
the target is far away from the sensor (the distance is greater than the value in DET_L_MSB and DET_L_
LSB). ). The LED will turn off when the target is close (the distance is less than the value in DET_H_MSB and
DET_H_ LSB).
LED_CURRENT: Sets the current through the LED.
SHORTCKT_DUTY_CYCLE: When the LMP91300 is in overload protection mode it will test to determine if the
overload condition is still present. The switch will be on for about 30µs, with an on to off duty cycle as set by
SHORTCKT_DUTY_CYCLE to protect the external BJT. For example, if SHORTCKT_DUTY_CYCLE is set to
0.1% the switch drive will be on for 30µs and off for 29.97ms (tOFF = (30µs/0.1%) - 30µs).
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DET_H_MSB_FNL – Detection High Threshold MSB (Final) (Address 0x73)
Bit
Name
Function (Default values in bold)
[7:0]
DET_H_MSB_FNL
0x00: Detection High Threshold MSB (Final)
See the Usage Priority Of Registers section.
A starting value to put in the DET_H_MSB_FNL and DET_H_LSB_FNL registers can be determined by first
setting
the
correct
values
in
the
OSC_CONFIG_0,
OSC_CONFIG_1,
OSC_CONFIG_2,
OSC_CONFIG_3_INIT/FNL, OUT_CONFIG_INIT/FNL registers, putting the target at the distance away from the
target that it is supposed to switch on at, reading the values in the PROXIMITY_MSB and Proximity LSB
registers, and writing these values into the DET_H_MSB_INIT/FNL and DET_H_LSB_INIT/FNL registers. This
value can be then adjusted as needed.
DET_H_LSB_FNL – Detection High Threshold LSB (Final) (Address 0x74)
Bit
Name
Function (Default values in bold)
[7:0]
DET_H_LSB_FNL
0x00: Detection High Threshold LSB (Final)
See the Usage Priority Of Registers section.
DET_L_MSB_FNL – Detection Low Threshold MSB (Final) (Address 0x75)
Bit
Name
Function (Default values in bold)
[7:0]
DET_L_MSB_FNL
0x00: Detection Low Threshold MSB (Final)
See the Usage Priority Of Registers section.
A starting value to put in the DET_L_MSB_FNL and DET_L_LSB_FNL registers can be determined by first
setting
the
correct
values
in
the
OSC_CONFIG_0,
OSC_CONFIG_1,
OSC_CONFIG_2,
OSC_CONFIG_3_INIT/FNL, OUT_CONFIG_INIT/FNL registers, putting the target at the distance away from the
target that it is supposed to switch off at, reading the values in the PROXIMITY_MSB and Proximity LSB
registers, and writing these values into the DET_L_MSB_INIT/FNL and DET_L_LSB_INIT/FNL registers. This
value can be then adjusted as needed.
DET_L_LSB_FNL – Detection Low Threshold LSB (Final) (Address 0x76)
Bit
Name
Function (Default values in bold)
[7:0]
DET_L_LSB_FNL
0x00: Detection Low Threshold LSB (Final)
See the Usage Priority Of Registers section.
24
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OSC_CONFIG_3_FNL – Oscillator Configuration 3 Register (Final) (Address 0x77)
Bit
Name
Function (Default values in bold)
[7:6]
RESERVED
00
[5]
UNDER_RANGE_SWITCH_EN
0: Off
1: On
[4:3]
OSC_AMP
00: 1V
01: 2V
10: 4V
11: Reserved
[2:0]
RESPONSE_TIME
000: Reserved
001: 96
010: 192
011: 384
100: 768
101: 1536
110: 3072
111: 6144
See the Usage Priority Of Registers section.
UNDER_RANGE_SWITCH_EN: The following applies if at least one temperature conversion has been
completed:
1. If RP < 798Ω (for example, the metal plate is against the sensor) before the fourth conversion of the RP to
digital converter (after Power On Reset) the switch will be activated regardless of the
UNDER_RANGE_SWITCH_EN setting.
2. If RP < 798Ω after the fourth conversion the switch state depends on the setting of
UNDER_RANGE_SWITCH_EN.
(a) If UNDER_RANGE_SWITCH_EN = 1: The switch will be enabled.
(b) If UNDER_RANGE_SWITCH_EN = 0: The previous switch state will be held until the oscillation restarts
(RP > 798Ω) and enough time has passed for a conversion to update the switch status.
If a temperature conversion has not been completed the switch state will not be changed.
OSC_AMP: The oscillation amplitude at terminals INA and INB can be set to 1V, 2V, or 4V. If the LMP91300 has
not been burned with user values, the power on value for OSC_AMP is 11: Reserved. This will need to be
changed to either 1V, 2V or 4V before the LMP91300 is used.
RESPONSE_TIME: Using a lower response time will shorten the settling time of the digital filter and give faster
readings from the RP to digital converter but will increase the noise in the reading. A higher setting gives the
digital filter more time to settle and will decrease the noise in the reading.
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OUT_CONFIG_FNL – Output Configuration Register (Final) (Address 0x78)
Bit
Name
Function (Default values in bold)
[7:6]
SWDRV_CURRENT
00: 2.5mA
01: 3.75mA
10: 5mA
11: 10mA
5
OUTPUT_MODE
0: 3-Wire NPN
1: 3-Wire PNP
4
DRIVE_MODE
0: Normally open
1: Normally closed
3
LED_ENABLE
0: On
1: Off
2
LED_MODE
0: Normally off
1: Normally on
1
LED_CURRENT
0: 2.5mA
1: 5mA
0
SHORTCKT_DUTY_CYCLE
0: 0.1%
1: 0.8%
See the Usage Priority Of Registers section.
SWDRV_CURRENT: Used to set the amplitude of current from the SWDRV terminal used to control the external
transistor.
DRIVE_MODE: Normally open and normally closed refer to the external NPN or PNP switch when a target is far
away from the inductive sensor. When the switch is normally open the transistor is not conducting when the
target is far away from the target (the distance is greater than the value in DET_L_MSB and DET_L_ LSB). The
switch is conducting when the target is close to the sensor (the distance is less than the value in DET_H_MSB
and DET_H_ LSB). When the switch is normally closed the transistor is conducting when the target is far away
from the target (the distance is greater than the value in DET_L_MSB and DET_L_ LSB). The switch is not
conducting when the target is close to the sensor (the distance is less than the value in DET_H_MSB and
DET_H_ LSB).
LED_ENABLE: When set to On the LED will function as set in Bit 2, LED_MODE. When set to Off the LED will
always be off.
LED_MODE: Normally off means that the LED is off when the target is far away from the sensor (the distance is
greater than the value in DET_L_MSB and DET_L_ LSB). The LED will turn on when the target is close (the
distance is less than the value in DET_H_MSB and DET_H_ LSB). Normally on means that the LED is on when
the target is far away from the sensor (the distance is greater than the value in DET_L_MSB and DET_L_
LSB). ). The LED will turn off when the target is close (the distance is less than the value in DET_H_MSB and
DET_H_ LSB).
LED_CURRENT: Sets the current through the LED.
SHORTCKT_DUTY_CYCLE: When the LMP91300 is in overload protection mode it will test to determine if the
overload condition is still present. The switch will be on for about 30µs, with an on to off duty cycle as set by
SHORTCKT_DUTY_CYCLE to protect the external BJT. For example, if SHORTCKT_DUTY_CYCLE is set to
0.1% the switch drive will be on for 30µs and off for 29.97ms (tOFF = (30µs/0.1%) - 30µs).
26
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TEMP64 – Temperature In °C + 64 (Address 0x79)
Bit
Name
Function (Default values in bold)
[7:0]
TEMP64
Temperature in °C + 64
Convert the value read from this register to decimal and subtract 64 to determine the temperature in °C.
PROXIMITY_MSB – Proximity MSB (Address 0x7A)
Bit
Name
Function (Default values in bold)
[7:0]
PROXIMITY_MSB
Proximity MSB
When a command is issued to read the PROXIMITY_MSB register, values from the RP to Digital converter are
placed in the PROXIMITY_MSB and Proximity LSB registers. The value in the Proximity LSB register will not
change until another read command of PROXIMITY_MSB is given. It is recommended that both the
PROXIMITY_MSB and Proximity LSB registers be read together.
PROXIMITY_LSB – Proximity LSB (Address 0x7B)
Bit
Name
Function (Default values in bold)
[7:0]
Proximity LSB
Proximity LSB
Bit
Name
Function (Default values in bold)
7
PADC_TIMEOUT
0: No timeout
1: Timeout
6
ECC_ERR
0: No error
1: Error
5
BUSY
0: Part is busy
1: Part is not busy
4
BURN_PROG
0: No burn in progress
1: Burn in progress
[3:0]
SWIF_STATUS
0x0: No burn has occurred, full SWIF access
0x1: Addresses 0x00 to 0x72 burned, full SWIF access
0x3: Addresses 0x00 to 0x78 burned, full SWIF access
0x7: Addresses 0x00 to 0x78 burned, SWIF is read only
0xF: Addresses 0x00 to 0x78 burned, SWIF is disabled
STATUS – Device Status (Address 0x7E)
When register 0x7E is read only one byte of data is transmitted from the LMP91300.
BURN_REQ – Burn Request (Address 0x7F)
Bit
Name
Function (Default values in bold)
[7:0]
BURN_REQ
0x08: Burn Temperature Look Up Table data (0x00 – 0x5D), initial
registers, device information registers, and configuration registers
(0x66 – 0x72).
0x10: Burn final registers (0x73 – 0x78).
0x20: Burn all registers (0x00 – 0x78).
0x40: Set SWIF to read back mode.
0x80: Disable SWIF.
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8 Application and Implementation
8.1 Application Information
The LMP91300 is a complete analog front end (AFE) optimized for use in inductive proximity sensors. The
LMP91300 detects the presence of a metal object based on the RP change of an LC oscillator, depending on the
distance of the metal object.
The LMP91300 can be used in 3 wire NPN or PNP inductive sensors.
8.2 Typical Application
6.5V to 40V
C1
REXT B
CFB
LED
CFA
CF
EXT B
CV+/EXT E
V+/EXT E
SENSE1+
SENSE2+
Load
SWDRV
+
INA
LMP91300
SENSE-
INB
CBY
RSENSE
TEMP+
NTC
GND
CBY
3-Wire NPN
Figure 19. 3-Wire NPN Configuration
6.5V to 40V
REXT B
C1
RSENSE
+
R1
-
CFB
LED
CFA
CF
EXT B
CV+/EXT E
Load
V+/EXT E
SWDRV
INA
LMP91300 SENSE1+
INB
NTC
CBY
TEMP+
SENSE2+
GND
SENSECBY
3-Wire PNP
Figure 20. 3-Wire PNP Configuration
For operation above 40V a series resistance must be added to SENSE1+ and SENSE2+. The mismatch in these
resistors will affect the overload protection accuracy for the PNP configuration. These resistors must be chosen
so that the SENSE1+ and SENSE2+ terminals do not operate above 40V.
28
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Typical Application (continued)
8.2.1 Design Requirements
1. Loop Voltage: 6.5V to 40V
2. LC Tank Oscillation Frequency: 0.005MHz to 5MHz
3. LC Tank RP: 798Ω to 3.93MΩ
8.2.2 Detailed Design Procedure
8.2.2.1 Quick Start
When a new sensor is being used the registers should be setup using the following procedure. Instructions on
how to determine the value to put in each register are described in the Register Maps section.
1. Set RP_MAX in the OSC_CONFIG_0 register.
2. Set PADC_TIMEC and RP_MIN in the OSC_CONFIG_1 register.
3. Set RESONATOR_MIN_FREQ in the OSC_CONFIG_2 register.
4. Set UNDER_RANGE_SWITCH_EN, OSC_AMP, and RESPONSE_TIME in the OSC_CONFIG_3_INIT and
OSC_CONFIG_3_FNL registers. The same values should be written to both registers. Setting OSC_AMP to
4V and RESPONSE_TIME to 6144 should give the most accurate results. Note that the power on default for
OSC_AMP is 11:Reserved so OSC_AMP must be changed to either 1V, 2V, or 4V.
5. Select the value of the CF capacitor as described in the CF (CFA and CFB Terminals) section.
6. Set the values in the OUT_CONFIG_INIT and OUT_CONFIG_FNL registers as needed. The same values
should be written to both registers.
7. Put the sensor at the target distance that the switch is supposed to turn on. Read the PROXIMITY_MSB and
Proximity LSB multiple times. If needed, RP_MAX or RP_MIN can be adjusted up or down one step at a time
to determine the combination that gives the most accurate setting for this specific sensor.
8. Put the sensor at the target distance that the switch is supposed to turn on. Read the PROXIMITY_MSB and
Proximity LSB multiple times, take an average, and write this value into the DET_H_MSB_INIT and
DET_H_LSB_INIT and DET_H_MSB_FNL and DET_H_LSB_FNL registers. This value may need to be
adjusted.
9. Put the sensor at the target distance that the switch is supposed to turn off. Read the PROXIMITY_MSB and
Proximity LSB multiple times, take an average, and write this value into the DET_L_MSB_INIT and
DET_L_LSB_INIT and DET_L_MSB_FNL and DET_L_LSB_FNL registers. This value may need to be
adjusted.
8.2.2.2 Determining The RP of an LC Tank
The method in the Quick Start section for setting the values in the LMP91300 registers requires that the RP of the
LC tank be known at the switching point (the point that the switch is changed from the normal condition to the
triggered condition). It is best to use an impedance analyzer to characterize the RP of the LC tank over distance.
If an impedance analyzer is not available the RP of the LC tank can be determined using the method below.
1. Set the target at the switching distance from the sensor.
2. Set PADC_TIMEC = 1, RESONATOR_MIN_FREQ as described in the Register Maps section, OSC_AMP =
4V, and RESPONSE_TIME = 6144.
3. Put a scope probe on INA or INB.
4. Step RP_MIN up one step at a time until the amplitude of the signal on the oscilloscope becomes variable as
shown in Figure 21 and Figure 22. Increase RP_MIN by two, for example if the amplitude becomes variable
at 17, set RP_MIN to 19.
5. Step RP_MAX up one step at a time until the amplitude of the signal on the oscilloscope becomes steady.
Decrease RP_MAX by two steps, for example if amplitude became steady at 16, set RP_MAX to 14.
6. Set the CF capacitor as described in the CF (CFA and CFB Terminals) section.
7. Read the Proximity value in registers 0x7A and 0x7B and convert this value to decimal.
8. Use the formula RPLCTANK (Ω) = (RP_MAX × RP_MIN ) / ( RP_MIN × (1-Y) + RP_MAX × Y ), where Y =
Proximity Data / 2^15 and RP_MAX and RP_MIN are the impedance values shown in Register Maps section.
This value can have a tolerance of ±25% when compared to the value from an impedance analyzer.
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Typical Application (continued)
8.2.2.3 Component Selection And Layout
The following PCB layout guidelines and suggested components should be used when designing a PCB.
8.2.2.4 CF (CFA and CFB Terminals)
10pF to 100nF, ≥10V, X7R ceramic capacitor. The traces connecting CFA and CFB to the capacitor should be as
short as possible to minimize the parasitic capacitance. The value of this capacitor will be based on the time
constant and resonating frequency of the LC tank.
For optimal performance, the value of CF, needs to be as small as possible, but large enough such that the
active filter does not saturate. The size of this capacitor depends on the time constant of the SENSE coil, which
is given by L/RS, (L = inductance, RS = series resistance of the inductor at oscillation frequency). The larger this
time constant becomes, the larger the value of filter capacitor that is required. Hence, this time constant reaches
its maximum when there is no target present in front of the sensing coil.
The following procedure can be used to determine CF:
1. Start with a default value of 10nF for CF.
2. Set RP_MAX, PADC_TIMEC, RP_MIN, RESONATOR_MIN_FREQ, OSC_AMP, and RESPONSE_TIME to
the desired values as described in the Register Maps section.
3. Move the metal target far away from the LC tank.
4. Connect a scope probe to the INB (terminal 21) and CFB (terminal 17) terminals. Since the CFB terminal is
very sensitive to capacitive loading, it is recommended to use an active probe. As an alternative, a passive
probe with a 1kΩ series resistance between the tip and the CFB terminal can be used.
5. Set the time scale of the oscilloscope so that many periods of the signal on the INA terminal can be seen.
See Figure 21.
6. Set the CF capacitor value so that the AC portion of the waveform is about 1VPP maximum. Decreasing the
capacitor value will make the AC portion of the waveform larger. This signal scales linearly with the
reciprocal of the filter capacitance. For example, if a 100pF filter capacitor is used and the signal observed
on the CFB terminal has a peak-to-peak value of 200mV, the desired 1V peak-to-peak value is obtained
using a 200mV / 1V × 100pF = 20pF filter capacitor. Figure 21 shows the waveforms on CFB and INA and
Figure 22 shows the waveforms using a zoomed in horizontal scale. Note that the waveforms on CFB and
INA are not a constant amplitude. The waveform on CFB should be adjusted so that the maximum value is
1VPP.
CFB
1 V/DIV
INA
1 V/DIV
50 µs/DIV
Figure 21. Determining the Value of CF
30
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Typical Application (continued)
CFB
1 V/DIV
INA
1 V/DIV
20 µs/DIV
Figure 22. Determining the Value of CF
8.2.2.5 NTC (TEMP+ Terminal)
The thermistor, such as the Murata NCP03WF104F05RL, should be placed as close to the LC tank as possible
to minimize error introduced by temperature variation within the operating environment. The NTC should also be
close to the LMP91300 to minimize the parasitic capacitance. It is connected between terminals 22 and 23.
There should be a ground trace separating the thermistor from the LC tank, to minimize the coupling from the
signal on the LC tank. Ideally, the thermistor could be on one side of the PCB and the LC tank on the other side
of the PCB with a ground plane between them.
8.2.2.6 C1
0.1µF to 1µF, ≥50V, X7R ceramic capacitor. This is a bypass capacitor for the regulator. The value of this
capacitor will also affect the rising and falling edges of the SWIF signal. A good value to start with is 0.1µF.
8.2.2.7 CV+/EXT
E
100nF, ≥10V, X7R ceramic capacitor. If the loop voltage is ≤ 8V, 100nF is the maximum value that can be used.
8.2.2.8 CBY (CBY Terminal)
56nF, ≥5V, X7R ceramic capacitor. Connect between the CBY terminal and ground.
8.2.2.9 RSENSE
The value of this resistor and power rating of the RSENSE resistor depends on the amount of current allowed
through the switch transistor. The LMP91300 has an Over Current Detection Threshold of 310mV typical. When
the LMP91300 detects ≥ 310mV across the sense resistor it will go into Overload Protection mode. In this mode
it will periodically turn on the switch for 30µs to check if the overload condition is still there. If the LMP91300
detects a value ≥ 310mV (typical) across the sense resistor it will limit the current through the switch so that the
voltage across RSENSE is ≤ 480mV. See the OVERLOAD PROTECTION entries in the ELECTRICAL
CHARACTERISTICS section and Figure 7, Figure 12, and Figure 13.
8.2.2.10 REXT B (EXT B Terminal):
The internal regulator along with the external NPN transistor will develop 5V on the V+/EXT E terminal. The EXT
B terminal will be one diode drop above this at about 5.6V. The voltage across REXT B will be the difference
between the loop voltage and the 5.6V on the EXT B terminal. The value of REXT B depends on the minimum loop
voltage and the minimum temperature that the LMP91300 will be used at. The values shown in Figure 23 show
the largest typical value for REXT B that can be used for a specific minimum loop voltage and minimum
temperature. For example, if the LMP91300 is being used in a proximity sensor that has a specification of 10V
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Typical Application (continued)
minimum for the loop voltage and an operating temperature minimum of 0°C, a value of 26kΩ or smaller can be
used for REXT B. The data shown in Figure 23 depends on several variables, such as the external transistor used
and the value of CV+/EXT E. A SMBTA06 transistor was used when taking the data in Figure 23. The user must
ensure that the resistor has the correct power rating and that the regulated 5V on the V+/EXT E terminal comes
up correctly and is stable for the entire loop voltage and temperature range in the intended application.
60
REXT B Max (k)
50
40
30
20
-40C
-20C
10
0C
0
5
10
15
20
25
30
35
40
Loop Voltage (V)
C001
Figure 23. Maximum REXT B Value
8.2.2.11 R1
33kΩ, 1/8W resistor.
8.2.2.12 SENSE1+ And SENSE2+ Terminals (RSENSE1+, RSENSE2+)
If the supply is ≤ 40V these terminals can be shorted to the supply. If the supply is > 40V resistors must be
placed between the SENSE1+ and SENSE2+ terminals and the supply. These resistors must drop enough
voltage so that the terminals of the LMP91300 are < 40V. The resistors will have 100µA going through them. For
example, if the supply is at 50V, 10V will need to be dropped across these resistors so the resistance will be
10V/100µV = 100kΩ. These resistors must be matched resistors, 0.1% or better. Keep the trace between the
LMP91300 and the resistors short.
In NPN mode the SENSE1+ terminal is not used. It should be connected to the supply as described above.
8.2.2.13 NPN
A SMBTA06 or similar transistor.
8.2.2.14 PNP
A FMMT593 or similar transistor.
8.2.2.15 LED
The LMP91300 can be programmed to supply 2.5 or 5mA. The LED chosen should have a voltage drop of less
than 3V. If an LED is not needed the LED terminal can be connected directly to the V+/EXT E terminal. The
LMP91300 uses the LED terminal to talk back to the device controlling the SWIF interface by sinking current into
the LED terminal.
32
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Typical Application (continued)
8.2.2.16 LC Tank and INA and INB Terminals
There should be a ground trace between the INA and INB terminals and the rest of the terminals of the
LMP91300 to decrease the coupling of the signal on the INA and INB terminals to the other terminals of the
LMP91300. The trace between the LC tank and the INA and INB terminals should be as short as possible as
shown in part A of Figure 24. Longer traces between the LC tank and the INA and INB terminals can cause
ringing at the INA and INB terminals which can produce very noisy proximity readings. If longer traces need to be
used split the LC tank so that the capacitor is close to the LMP91300 as shown in part B of Figure 24. If both the
L an C have to be located a longer distance away from the LMP91300 small capacitors (15 to 22pF) can be
connected between INA and ground and INB and ground as shown in part C of Figure 24.
Short
Traces
L
Long
Traces
INA
LMP91300
C
Short
Traces
L
C
INB
A
Long
Traces
INA
LMP91300
L
INA
LMP91300
C
INB
INB
B
C
Figure 24. LC Tank Traces
8.2.2.17 SWDRV Terminal
Keep the trace between the SWDRV terminal and the transistor short.
8.2.2.18 P1 To P5 Terminals
Connect to ground using short traces.
8.2.2.19 GND Terminals
Connect to ground using short traces.
8.2.2.20 NC Terminals
These terminals do not connect to the silicon and can be left unconnected.
8.2.2.21 Exposed DAP
Connect to ground. The DAP area on the PCB can be used as the center of a star ground with all other ground
terminals connecting to it.
8.2.2.22 SENSEIn PNP mode the SENSE- terminal is not used. It should be connected to ground.
8.2.3 Look-Up Table Calibration
1. RP Measurement: Take RP measurements by reading the Proximity registers 0x7A and 0x7B from the
lowest temperature of interest to the highest temperature within the predefined LUT values. The temperature
range should fall within the LUT preset values of -48°C to 136°C in 4°C increments. Convert all the
measured values from hex to decimal.
(a) Proximity measurements at all temperatures between -48°C to 136°C will give the most accurate results.
If the proximity measurement at some temperatures are skipped a value will need to be interpolated from
the measured values. This is described in step 4.
(b) To avoid uncertain conditions outside the temperature range of interest the user should duplicate the
same value of RP for the temperature below and above those limits. For example, if the lowest
temperature that a proximity measurement was made was -28°C, this value should be used for all lower
temperatures. The same applies at the high temperature range of the LUT.
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Typical Application (continued)
2. Temperature Correlation: For every RP measurement the temperature register TEMP64 (0x79) should be
read to ensure that the ambient temperature correlates to the intended LUT preset temperature. The
TEMP64 register is an 8 bit unsigned register that contains the temperature (in °C) + 64. Any discrepancy
between ambient temperature and preset LUT temperature during calibration will result in a temperature
calibration error.
3. Normalizing RP: Once all RP values have been read and logged for the whole LUT temperature range as
illustrated in Figure 25 the data must be normalized to the intended ambient operating temperature T0. This
is done by dividing each RP data point by R0, the measured RP at the ambient operating temperature for
each temperature of the LUT register. This ratio provides the gain correction factor coefficients (GCF) as
shown in Figure 26. If the ambient operating temperature T0 does not fall on one of the 4°C incremental
points of the LUT then R0 will need to be interpolated.
RP
T0: Temperature of operating environment
R0: RP at operating environment
R-1
R0
R1
-48°C
-44°C
-40°C
T-1
T0
T1 128°C
132°C
136°C
Temperature
Figure 25. RP Measurement Example
GCF
GCF-1 =
R-1
R0
GCF1 =
R1
R0
T0: Temperature of operating environment
GCF0: Normalized to 1 at operating environment
1
-48°C
-44°C
-40°C
T-1
T0
T1 128°C
132°C
136°C
Temperature
Figure 26. GCF Normalized Example
4. Interpolating GCF values that have not been measured: Plot the measured GCF values vs temperature
and then make a polynomial trend line of the data. Use the formula of the trend line to determine the GCF
values for all temperatures that were not measured.
5. LUT Data Entry: Each GCF needs to be converted from decimal to a 16 bit binary word representing a
decimal number between 0 and 4. An example illustrating this binary representation of the decimal number is
shown in Figure 27. The conversion equation that scales the GCF into the 16 bit binary GCFBINARY is shown
in Equation 2. Once the conversion has been calculated for each temperature the values are programmed
34
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Typical Application (continued)
into the appropriate registers in the LUT. The MSB of the LUT value consists of bits D15 to D8 as shown in
Figure 27, the LSB are bits D7 to D0.
D15
D14
D13
D12
D7
D6
D5
D4
D3
D2
D1
D0
Decimal Representation
Figure 27. Binary Representation Of Gain Correction Factor
GCFBINARY = GCF ×
216
4
(2)
6. NTCs with a β ≠ 4250: The temperature LUT has been internally hard coded based on a specific NTC with a
β factor of 4250 (Murata NCP03WF104F05RL). The user must recalibrate the LUT when an NTC with a β
factor other than 4250 is used. The LUT temperature range is extended past the LMP91300 operating range
to facilitate recalibrating the LUT if using other off the shelf NTC components. The process for using a NTC
that has β ≠ 4250 is as follows:
(a) Put the finished system including the LC tank, NTC and LMP91300 into a temperature chamber.
(b) Set the temperature of the chamber to a value, for this example we will use -40°C.
(c) Read the temperature from register 0x79. For this example we will use -44°C.
(d) Follow the process above to determine the gain.
(e) The gain value will go into the -44°C position of the LUT.
(f) Connect terminals P1 - P5 to ground using short traces.
(g) Connect the Ground terminal to the main ground point using short traces.
9 Power Supply Recommendations
An internal voltage regulator allows the LMP91300 to operate with a supply from 6.5V to 40V. The values of C1
and CV+/EXT E must be chosen as described in the Detailed Design Procedure section.
10 Layout
10.1 Layout Guidelines
•
•
•
•
•
The traces connecting pins CFA and CFB to the CF capacitor should be as short as possible to minimize the
parasitic capacitance.
The NTC should be placed as close to the LC tank as possible to minimize error introduced by temperature
variation within the operating environment. The NTC should also be close to the LMP91300 to minimize the
parasitic capacitance. There should be a ground trace separating the thermistor from the LC tank, to minimize
the coupling from the signal on the LC tank. Ideally, the thermistor could be on one side of the PCB and the
LC tank on the other side of the PCB with a ground plane between them.
There should be a ground trace between the INA and INB terminals and the rest of the terminals of the
LMP91300 to decrease the coupling of the signal on the INA and INB terminals to the other terminals of the
LMP91300. The trace between the LC tank and the INA and INB terminals should be as short as possible as
shown in part A of Figure 24. Longer traces between the LC tank and the INA and INB terminals can cause
ringing at the INA and INB terminals which can produce very noisy proximity readings. If longer traces need
to be used split the LC tank so that the capacitor is close to the LMP91300 as shown in part B of Figure 24. If
both the L an C have to be located a longer distance away from the LMP91300 small capacitors (15 to 22pF)
can be connected between INA and ground and INB and ground as shown in part C of Figure 24.
Keep the trace between the SWDRV terminal and the transistor short.
The DAP area on the PCB can be used as the center of a star ground with all other ground terminals
connecting to it.
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10.2 Layout Example
Top Layer
NTC
LMP91300
RSENSE REXT B
NPN
R1 C1
Bottom Layer
LC Tank
CF CBY
CV+/EXT E
NPN
PNP
LED
Figure 28. LMP91300 PNP Layout Example
36
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11 Device and Documentation Support
11.1 Trademarks
All trademarks are the property of their respective owners.
11.2 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.
11.3 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.
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LMP91300NHZJ
ACTIVE
WQFN
NHZ
24
4500
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 125
L91300
LMP91300NHZR
ACTIVE
WQFN
NHZ
24
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 125
L91300
LMP91300NHZT
ACTIVE
WQFN
NHZ
24
250
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 125
L91300
LMP91300YZRR
ACTIVE
DSBGA
YZR
20
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
ATAA
LMP91300YZRT
ACTIVE
DSBGA
YZR
20
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
ATAA
(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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