EPC EPC600 Time-of-flight range-finder chip Datasheet

DATASHEET – epc600
Time-of-flight range-finder chip
General Description
Features
The epc600 chip is a general purpose, monolithic, fully integrated
photoelectric CMOS device for optical distance measurement and
object detection. Its working principle is based on the three-dimensional (3D) time-of-flight (TOF) measurement.
The system-on-chip (SOC) contains:
■ A full data acquisition path with the driver for the LED, the photoreceiver, the signal conditioning, the A/D converter and the signal
processing.
■ An on-chip controller managing the data acquisition and the data
communication.
■ A 2-wire interface for the command and data communication.
■ A supply-voltage power management unit.
■ Complete data acquisition system for distance measurement or
object detection on chip. Allows for minimum part count designs.
■ On-chip high power LED driver.
■ Easy to use operation in combination with a tiny microprocessor.
■ Absolute distance measurement with digital data output.
■ Integrated signal-processing.
■ High sensitivity and resolution for measured distances up to 15m.
■ Response time of less than 1ms possible.
■ Digital data output with 12 bit distance data.
■ Excellent ambient-light suppression up to >100kLux.
■ Integrated ambient-light meter (“Luxmeter”)
e.g. for brightness control or dimmer functions.
■ Voltage supply with low power consumption.
■ Easy to use 2-wire interface with simple command set.
■ Fully SMD-compatible flip-chip CSP24 package with very small
footprint.
Together with a tiny microprocessor and few external components,
a fully functional TOF range-finder can be built.
The working principle is based on the elapsed time-of-flight (TOF)
of a photon (modulated light) emitted by the transmitter (LED) and
reflected back by the object to the photosensitive receiver.
The very high photosensitivity allows operating ranges up to several meters and an accuracy down to a centimeter depending on the
lens and the illumination power.
Possible Applications
■ Light barrier with powerful ambient-light suppression
■ People and object counting sensor
■ Door opening and safety sensor
■ Limit and proximity switch
■ Machine control and safety sensor
■ Water tap and toilet flushing sensor
■ Single spot parking sensor
■ Distance measurement gauge
Functional Block Diagram
XTAL
CX1
CX2
VDD 8.5V
VDDBS -5.0V
Voltage
regulator
LED
Modulator
Controller
RAM
EEPROM
LED driver
Phase shifter
2-wire
serial
interface
SCLK
Signalprocessing
SDATA
A
D
Correlator
Figure 1: epc600 on-chip data acquisition system for range-finders
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
1 / 30
Datasheet epc600 - V1.3
www.espros.ch
Table of Contents
General Description............................................................................................................................................................................................1
Features............................................................................................................................................................................................................. 1
Possible Applications......................................................................................................................................................................................... 1
Functional Block Diagram.................................................................................................................................................................................. 1
Absolute Maximum Ratings (Note 1, 2) ............................................................................................................................................................ 3
Operating Ratings.............................................................................................................................................................................................. 3
Electrical Characteristics....................................................................................................................................................................................3
Timing and optical Characteristics..................................................................................................................................................................... 4
Other Parameters...............................................................................................................................................................................................5
Pin Configuration................................................................................................................................................................................................6
Layout information..............................................................................................................................................................................................7
CSP-24 Package (all measures in mm, ).................................................................................................................................................... 7
Design precautions...................................................................................................................................................................................... 7
ESD protection.............................................................................................................................................................................................7
Reflow Solder Profile..........................................................................................................................................................................................8
Packaging Information (all measures in mm).....................................................................................................................................................8
Ordering information...........................................................................................................................................................................................8
Functional Description........................................................................................................................................................................................9
1. Operation.................................................................................................................................................................................................. 9
1.1. Introduction............................................................................................................................................................................................ 9
1.2. General overview................................................................................................................................................................................... 9
1.3. Operational mode................................................................................................................................................................................ 10
1.3.1. Distance measurement.....................................................................................................................................................................10
1.3.2. System sensitivity, integration time and operating range ................................................................................................................. 11
1.3.3. Ambient-light suppression................................................................................................................................................................ 12
1.3.4. Quality of the measurement result ....................................................................................................................................................12
1.3.5. Ambient-light measurement (optical power-meter) .......................................................................................................................... 14
1.3.6. Temperature metering.......................................................................................................................................................................14
1.3.7. Measurement sequence................................................................................................................................................................... 15
1.3.8. Calibration and compensations ........................................................................................................................................................ 16
1.3.9. Extended operating range ................................................................................................................................................................ 16
1.3.10. Multi range-finder application......................................................................................................................................................... 16
2. Hardware Design.................................................................................................................................................................................... 17
2.1. What performance can be achieved? ..................................................................................................................................................17
2.2. General Hardware Configuration.........................................................................................................................................................18
2.3. Power Supply, Clock generation..........................................................................................................................................................18
2.4. On-chip LED driver.............................................................................................................................................................................. 19
LEDs with a +5V supply.............................................................................................................................................................................19
Short range application design (LED supply from +8.5V) ......................................................................................................................... 19
Mid range application design (LED supply from +8.5V) ............................................................................................................................ 20
2.5. External LED driver..............................................................................................................................................................................20
3. Instruction Set......................................................................................................................................................................................... 21
3.1. 2-wire serial interface...........................................................................................................................................................................21
3.1.1. SCLK line.......................................................................................................................................................................................... 21
3.1.2. SDATA line........................................................................................................................................................................................ 21
3.2. Commands & responses..................................................................................................................................................................... 23
3.2.1. Command: Commands & Integration times ..................................................................................................................................... 23
3.2.2. Response: Distance..........................................................................................................................................................................24
3.2.3. Response: Valid & saturated pixels .................................................................................................................................................. 24
3.2.4. Response: Q-subsample QSx.......................................................................................................................................................... 24
3.2.5. Response: Ambient-light level.......................................................................................................................................................... 25
3.2.6. Response: Temperature................................................................................................................................................................... 25
3.3. Communication tasks.......................................................................................................................................................................... 26
3.3.1. Measurement sequence (Distance or ambient-light) ....................................................................................................................... 26
3.3.2. Read sequence (Valid & saturated pixels, Q-subsample QSx, Temperature) ................................................................................. 26
3.3.3. Error detection by the microprocessor ............................................................................................................................................. 26
3.3.4. Reset and recovery sequence sequence ......................................................................................................................................... 27
3.3.5. Error detection by the epc600 chip ...................................................................................................................................................27
3.3.6. Cycle times & response time............................................................................................................................................................ 28
Integration time.......................................................................................................................................................................................... 28
Measurement time..................................................................................................................................................................................... 28
Communication time.................................................................................................................................................................................. 28
Data processing time................................................................................................................................................................................. 28
Measurement cycle time............................................................................................................................................................................28
Response time........................................................................................................................................................................................... 28
LED on-time and LED duty cycle...............................................................................................................................................................28
4. Optical Design Considerations............................................................................................................................................................... 29
Photosensitive area................................................................................................................................................................................... 29
Signal sensitivity........................................................................................................................................................................................ 29
Ambient-light suppression..........................................................................................................................................................................29
Operating range......................................................................................................................................................................................... 29
IMPORTANT NOTICE...................................................................................................................................................................................... 30
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
2 / 30
Datasheet epc600 - V1.3
www.espros.ch
Absolute Maximum Ratings (Note 1, 2)
Operating Ratings
Supply Voltage V DD
Voltage to any pin except V DD
according voltage class V SC (Note 3)
-0.5V to +9.5V
-0.3V to V SC+0.3V
Operating temperature (T A)
Humidity, non-condensing
Storage temperature (T A)
Soldering Lead Temperature (T L), 4 sec
-65°C to +150°C
+260°C
-20°C to +65°C
5% to 95%
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating conditions indicate condi tions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and
test conditions, see Electrical Characteristics.
Note 2: This is a highly sensitive CMOS mixed signal device with an ESD rating of JEDEC HBM class 2 ( 2kV to < 4kV) except for the pins
VDD, VDDIO and SCLK with an ESD rating of JEDEC HBM class 1B ( 0.5kV to < 1kV). Handling and assembly of this device should only
be done at ESD protected workstat ions.
Note 3: For voltage classes V SC refer to Figure 4 and Table 4.
Electrical Characteristics
Operational Ratings - unless otherwise specified.
Symbol
Parameter
Conditions / Comments
VSC
Min.
Typ.
Max.
Unit
VDD
Supply voltage at VDD
8.5V
+8.0
+8.5
+9.0
V
VDD-PP
Ripple on VDD
peak-to-peak
8.5V
100
mV
IDD-Average
Supply current
IDD-Peak
Supply current
DC average , excl. LED driver current
8.5V
20
mA
peak, excl. LED driver current
8.5V
30
mA
VDDBS
Bias voltage
no drift allowed
-5.0V
-5.1
V
VDDBS-PP
Ripple on VDDBS
peak-to-peak
-5.0V
50
mV
IDDBS
Bias current
-5.0V
1.0
mA
VLED
Voltage at LED
maximum
+5.0V
5.0
V
ILED-ON
Sink current at LED
open drain driver
+5.0V
180
mA
VLED-ON
Forward voltage at LED
@ ILED-ON = 180mA
+5.0V
VDigital-OH
Output high voltage
at SDATA
+5.0V
4.5
5.2
V
VDigital-OL
Output low voltage
at SDATA
+5.0V
0
0.5
V
IDigital-OH
Output current
at SDATA, DC, average
+5.0V
0.1
mA
IDigital-OL
Output current
at SDATADC, sink current
+5.0V
8.0
mA
CDigital-Out
Load capacitance
+5.0V
30
pF
VDigital-IH
Input high voltage
at SDATA and SCLK
+5.0V
4.0
5.0
V
VDigital-IL
Input low voltage
at SDATA and SCLK
+5.0V
0
1.0
V
IDigital-In
Input leakage current
except VDDT, DC
+5.0V
1.0
μA
IDigital-In
Input current
at VDDT; DC
+5.0V
42
μA
RDOWN
Termination resistor
at VDDT; pull-down resistor
+5.0V
120
kΩ
CDigital-In
Input capacitance
+5.0V
-4.9
-5.0
200
mV
3
pF
Table 1: Electrical characteristics
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
3 / 30
Datasheet epc600 - V1.3
www.espros.ch
Timing and optical Characteristics
Operational Ratings - unless otherwise specified.
Symbol
Parameter
Conditions / Comments
Min.
Typ.
Max.
Unit
tON
Power-up rise time
at VDD
1
10
ms
tINIT
Start-up time
tOFF
Power drop-down time
at VDD
1
100
ms
10
ms
fXTAL
Center frequency
of the crystal oscillator (or ceramic resonator)
ΔfXTAL
Frequency deviation
of the oscillator,
any deviation is added as a linear distance error
ΔφXTAL
Phase jitter
of the oscillator, peak-to-peak, cycle to cycle
fSCLK
Clock frequency
of SCLK, 2-wire interface
tSCLK
Cycle time
of SCLK2, 2-wire interface, SCLK = 1/fSCLK
100
tH / tL
HIGH / LOW period
of SCLK2, 2-wire interface, refer to Table 8
50ns
fMOD
LED modulation
frequency at pin LED
see Figure 14,
standard products fixed 10MHz,
(customer specific factory setting possible:
1.25 - 10MHz)
tLED-rise/fall
Required rise/fall time
of the illumination LED
@ 50 ohm load
Remark: Use high speed LEDs with short switch ing times e.g. Osram SFH4059,
Vishay VSMB2000, Stanley DNK5306, etc.
ASENSOR
Photosensitive area
of the sensor
SAC
AC sensitivity
(conversion rate)
for distance measurement (modulated light), refer
to Table 3 and Figure 14.
@ λ = 850±50nm, Integration time = 103 μsec.
Note: The chip does internal an averaging over
the sensitive area, refer to chapter 1.3.4.
SDC
DC sensitivity
(conversion rate)
for ambient-light measurement (unmodulated
light), refer to Table 3 and Figure 14
@ λ = 850±50nm, Integration time = 103 μsec.
Note: The chip does internal an averaging over
the sensitive area, refer to chapter 1.3.4.
AAC
Received modulated light dynamic range for distance measurement
amplitude
50
1'000
LSB
ADC
Ambient-light
amplitude
dynamic range for ambient-light measurement
50
1'000
LSB
ESup
Ambient-light suppression
@ λ = 850±50nm, Integration time = 103 μsec,
total power on sensor area
40
4
λmax
Peak wavelength
maximum sensitivity, see Figure 2
λ
Wavelength range
operating range
φ50%
Half angle
see Figure 3
4
MHz
±100
ppm
50
ps
10
MHz
ns
1.0ms
10
ns
MHz
12
ns
320x320
μm
31
nW/ cm
LSB
12.3
nW/ cm
LSB
2
2
W/m2
μW/Sensor
850
550
nm
1'000
±60
nm
deg
Table 2: Timing and optical characteristics
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
4 / 30
Datasheet epc600 - V1.3
www.espros.ch
Symbol
Parameter
Conditions / Comments
Min.
tINT
Integration time
refer to Figure 14,
programmable in 16 binary steps
1.60
tMEAS
Measurement time
refer to Figure 14
0.8
DR
Dynamic range
fixed integration time
using integration times 1.6μs, 13.2μs, 205μs
using the full range of integration times
32
DUA
Operating range
unambiguity range,
@10MHz LED modulation frequency
ΔDRES
Distance resolution
@10MHz LED modulation frequency, ≙ 1 LSB
ΔD
Distance noise
single shot, 1σ value,
ratio ambient-light : modulated light < 60dB
ratio ambient-light : modulated light < 70dB
for amplitude values inside AC dynamic range
Typ.
1.2
Max.
Unit
52'600
μs
212
ms
110
dB
dB
dB
15.0
m
80
0.5
cm
2.5
12.0
DOFFSET
Distance offset
compensation to be done by the external micro processor
ΔDDRIFT
Distance drift
@ temperature range from -20°C to +65°C;
compensation to be done by the external micro processor
mm
mm
Table 2 cont.: Timing and optical characteristics
Other Parameters
Operational Ratings and λ = 850±50nm, AOI = 0°, LED modulation frequency = 10MHz - unless otherwise specified.
Sensitivity: epc600
with bandpass filter
@ integration time 103μs
max. AC amplitude (1'000 LSB)
without filter
640nm
± 27.5nm
860nm
± 32.5nm
940nm
± 30nm
sunlight
equivalent
407 nW/mm 2
310 nW/mm2
407 nW/mm 2
53 W/m2
70 klx
min. ambient-light suppression E Sup
40 W/m
69 klx
2
53 W/m
192 klx
2
Table 3: Sensitivity and ambient-light suppression vs. wavelength
500nm
1
630nm
850nm
950nm
100.00
0.8
0.7
0.6
Reflectance (%)
Relative Sensitivity
0.9
0.5
0.4
0.3
10.00
0.2
0.1
0
1.00
500
600
700
800
900
0
1000
Figure 2: Relative spectral sensitivity (S λ)
sensitivity S AC vs. wavelength
Characteristics subject to change without notice
20
30
40
50
60
70
80
90
Angle of incidence (deg)
Wavelength [nm]
© 2014 ESPROS Photonics Corporation
10
Figure 3: Reflectance vs. illumination angle (AOI)
5 / 30
Datasheet epc600 - V1.3
www.espros.ch
Pin Configuration
Voltage classes
XTAL2
XTAL1
NC4
NC3
LED
VDDCP
12V
16
15
14
13
12
11
10
VDD
15
16
8.5V
VDDPLL
10V
17
NC1
24
23
GNDPLL
GNDLED
18
10
VDDHPX
3
8
GND
1.8V
20
SCLK
1
22
3
HLLED VDDCORE VDDT
NC2
7
20
VDDIO
4
5
6
GNDM
VREF
VDDBS
18
Pin No. Type
VSC
SDATA
SCLK
VDDPX
VDDHPX
HLLED/NC2
VDDCP
NC1
VDDBS
GND GNDA GNDPLL
21
22
24
Figure 4: Pin configuration
Pin Name
VDDPLL
VDDIO
19
GNDA
21
2
VDDT
VDDCORE
VDDPX
1
-5V
GNDM
NC4
VREF
19
SDATA
NC3
epc600
Top View
5V
LED
XTAL2
VDD
4
9
XTAL1
12
13
14
2
17
5
7
8
9
11
6
GNDLED
23
Figure 5: Schematic symbol
Description
SDATA
19
DOUT
DIN
+5.0V
Serial data, bidirectional data transmission of the 2-wire interface
SCLK
20
DIN
+5.0V
Serial clock input SCLK of the 2-wire interface
LED
12
AOUT
+5.0V
LED driver output, high current, open drain, square-wave signal
XTAL1
15
AIN
+1.8V
Oscillator input, use only with crystal (or ceramic) oscillator
XTAL2
16
AOUT
+1.8V
Oscillator output, use only with crystal (or ceramic) oscillator
VDD
10
SUPPLY
+8.5V
Power supply +8.5V
VDDCORE
2
SUPPLY
+1.8V
Decoupling of internal digital core supply +1.8V
VDDPLL
17
SUPPLY
+1.8V
Decoupling of internal PLL supply +1.8V
VREF
5
SUPPLY
+5.0V
Attention: Do not connect this pin
VDDIO
7
SUPPLY
+5.0V
Decoupling of the internal internal I/O supply +5.0V
VDDPX
8
SUPPLY
+5.0V
Decoupling of the internal pixel reference voltage +5.0V
VDDHPX
9
SUPPLY
+10V
Decoupling of the internal pixel reference voltage +10V
VDDCP
11
SUPPLY
+12V
Filter capacitor pin for the charge pump circuit +12V
VDDBS
6
SUPPLY
-5.0V
Power supply: Bias voltage -5.0V
VDDT
3
DIN
+5.0V
With pull-down resistor 120kOhm; connect to +5.0V.
GND
21
SUPPLY
---
Ground for digital circuitry +1.8V
GNDA
22
SUPPLY
---
Ground for analog circuitry, charge pumps and +5.0V I/O circuit
GNDPLL
24
SUPPLY
---
Ground for PLL
GNDLED
23
SUPPLY
---
Ground for LED driver
GNDM
4
DIN
NC1
+5.0V
Connect to GND
18
+5.0V
Attention: Do not connect this pin
HLLED/NC2
1
+5.0V
Connect this pin with a 1kOhm resistor to GND
NC3
13
+5.0V
Attention: Do not connect this pin
NC4
14
+5.0V
Connect this pin with zero ohm resistor to GND
Table 4: Pin function descriptions
Abbreviations to Table 4:
VSC
Supply class for matching components and I/O voltage levels
DOUT
Digital output
DIN
Digital input
AOUT
Analog output
AIN
Analog input
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
6 / 30
Datasheet epc600 - V1.3
www.espros.ch
CSP-24 Package (all measures in mm,
)
0.200
1.325
0.450
0.200
0.450
Designed
<Name>
Approved
<Name>
<Data>
M 1:1
DIN A4
Scale
Page
Part Name
26.02.2009
1
Part No.
<x000 000>
<Partname>
This document is confidential and protected by law and international tra des. It must not be shown t o any third part y nor be copied in any f orm without our written pe.rmission
Layout information
0.450
∅ 0.300
0.450
0.150
0.200
0.450
0.200
File:
0.450
2.650 ±0.1
0.450
Via GND
min. ∅ 1.00
1.325
Hole
∅ 0.50 - 0.60
0.450
0.320
2.77 +0.00/-0.16
Solder stop
∅ 1.40
0.320
Pin 1
2.76 +0.00/-0.16
2.650 ±0.1
Pin 1
Photosensitive area
on the backside of the chip
no solder stop inside this area
0.23 ±0.04
0.050
Solder balls
Sn97.5Ag2.5
Circuit side (Frontside)
Figure 6: Mechanical dimensions
Figure 7: Layout recommendation
Recommendations for a strong ground connection and for reliable soldering of solder balls:
■ Use a pad layout similar to Figure 7. Notice, all tracks should go underneath the solder mask areas.
■ To keep the noise floor low in the sensitive receiver path of the chip, a low ohmic and low inductive connection to the supply ground is
needed. Figure 7 suggests a recommended grounding of the chip (if a ground plane is not feasible):
Feed all grounds into a central via-hole with a drill diameter 0.5 - 0.60mm.
■ No additional connects to any pins inside of the opening of the solder mask.
■ The open via underneath the chip must be covered with a solder-stop lid, to prevent ascending solder during the soldering process.
■ Refer also to our application note AN04 and AN08 Assembly of Wafer Level Chip Scale (WL-CSP) Packages.
Design precautions
The sensitivity of the sensor area is very high in order to achieve a long operational range of the range-finder. Thus, the epc600 device is
very sensitive to EMI. Special care should be taken to keep the chip away from the IR LED signal tracks and other sources which may in duce unwanted signals.
ESD protection
VDDPLL
VDDCORE
VDDBS
VDD
VREF
VDDPX
VDDHPX
VDDCP
VDDIO
Highly sensitive CMOS mixed signal devices are sensible to electrostatic discharge (ESD). Figure 8 shows the principle how each pin of
the chip is protected against ESD over-voltages by the corresponding safety elements.
VDDCORE
epc600
XTAL1
XTAL2
SDATA
SCLK
HLLED/NC2
NC1
GNDM
VDDT
LED
NC3
LEDF
GND
GNDPLL
GNDLED
GNDLED
GNDPLL
GND
GNDA
GNDA
Figure 8: ESD protection of the pins
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
7 / 30
Datasheet epc600 - V1.3
www.espros.ch
Reflow Solder Profile
For infrared or conventional soldering, the solder profile has to follow the recommendations of IPC/JEDEC J-STD020C (revision C and
later) for lead-free assembly. The peak soldering temperature (T L) should not exceed +260°C for a maximum of 4 sec.
Packaging Information
(all measures in mm)
Tape & Reel Information
The devices are packaged into embossed tapes for automatic placement systems. The tape is wound on 178mm (7inch) or 330mm
(13inch) reels and individually packaged for shipment. General tape-and-reel specification data are available in a separate datasheet and
indicate the tape size for various package types. Further tape-and-reel specifications can be found in the Electronic Industries Association
EIA-Standard 481-1, 481-2, 481-3.
8mm
Pin 1 / Solder balls bottom side
4mm
Figure 9: Tape dimensions
epc does not guarantee that there are no empty cavities in the tape. Thus, the pick-and-place machine should check the presence of a
chip during picking.
Raster
Ordering information
2.5mm
2.5mm
LST
Part number
Part name
Package
File:
RoHS compliance
27.07.2011
Page 1
Packaging method
This document is confidential and protected by law and international trades. It must not be shown to any third party nor be copied in any form without our written permission .
P100 037
epc600-CSP24
CSP24
Yes
Reel
Table 5: Ordering information
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
8 / 30
Datasheet epc600 - V1.3
www.espros.ch
Functional Description
This manual is arranged in the following sections:
■ Operation
This general description of the operation and the functionalities is targeted at the user and application level.
■ Hardware Design
All information regarding hardware design aspects are covered here.
■ Instruction Set
Contains a detailed description of the data communication and the command set.
■ Optical Design Considerations
The chapter where the user finds some design guidelines for developing appropriate optics and illumination for the device.
1. Operation
1.1. Introduction
The epc600 chip is based on the 3D-TOF principle. Modulated light is sent out by a transmitter. This light is then reflected by the object to
be detected and the returning light is sampled by a photosensitive sensor. The receiver compares the phase difference between the emitted and the received light and computes the time difference of the “time-of-flight”. This value multiplied by the speed of light (ca.
300'000km/sec) and divided by 2 corresponds directly to the distance.
Object
epc600
device
Backscattered light with a time delay
dependent on the distance between
the object and the device
Figure 10: The time-of-flight principle
1.2. General overview
The epc600 chip is designed to enable simple and cost effective system designs. Together with a tiny microprocessor and few external
components, a very low cost but fully functional TOF sensor system can be built (refer to Figure 11).
The epc600 system-on-chip contains:
■ A full data acquisition path with a power driver for the LED, the photo-receiver, the signal conditioning, the A/D converter and the signal
processing.
■ An on-chip controller managing the data acquisition and the data communication.
■ A 2-wire serial interface for the command and data communication.
■ A supply-voltage power management unit.
epc600
Microprocessor
IR LED
DIST
OUT
SCLK
SCLK
SDATA
SDATA
CCD
LED
< 180mA
2-wire interface
Figure 11: Basic application
The measurement functionality supports distance and ambient-light measurement with variable integration times and on-chip temperature
measurement for drift compensation.
The sensitivity of the system can be adjusted o n the fly to the object reflectivity, the object distance and the ambient-light conditions by
means of integration time. The longer the integration time, the higher the sensitivity.
In cases where the illumination power of the built-in driver is not sufficient, the epc600 chip can also be used with an external LED driver.
This allows longer operational ranges or faster measurements, resulting in a faster response time and a reduced ambient-light sensitivity.
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
9 / 30
Datasheet epc600 - V1.3
www.espros.ch
1.3. Operational mode
This chapter lists the available features for the epc600-device.
The range-finder works in combination with a tiny microprocessor. It operates according to a single shot principle. A command sent by the
microprocessor sets the user parameters in the chip and stimulates either a distance or ambient-light measurement. The device executes
the requested task standalone and sends back the answer (data) according to Figure 12.
Measure n-1
Measure n
Measure n+1
measurement cycle time tCYCLE
Command:
Set parameters
Trigger capture
Measurement n-1
Response:
Read data
Calculation n-1
Distances & Quality
Command:
Set parameters
Trigger capture
communication and data processing time
Measurement n
Response:
Read data
Calculation n
Distances & Quality
Command:
Set parameters
Trigger capture
measurement time t MEAS
Measurement n+1
Response:
Read data
Figure 12: Basic measurement cycle e.g. distance (or ambient-light)
The microprocessor controls the parameter settings for the measurement and the start. It computes from the read-out data the final distance. This also includes applying the necessary correction algorithms based on quality, ambient-light and temperature data and to adapt
the epc600 settings to the useful operational range and present scenery conditions.
The epc600 chip supports range finding as a single spot distance measurement, ambient-light measurement (similar to an optical pow er-meter or “Luxmeter”) and temperature metering.
1.3.1. Distance measurement
The distance measurement is done by single shots following the protocol in Figure 13, first section.
Microprocessor
Request measurement:
- Select type
- Select integration time
- Send command
2-wire interface
epc600
Idle
Tx
Command:
1a) Measurement of distance
2a) Measurement of ambient-light
Set measurement type
Set integration time
Wait for response
Do measurement
Rx
Read measurement data
Send data
Response:
1b) Distance
2b) Ambient-light
Idle
Calculate result
Idle
Request data:
- Send command
Tx
Fetch data
Command:
3a) Read pixel status
4a) Read Q-subsample QSx
5a) Read temperature
Wait for response
Read measurement data
Send data
Rx
Idle
Response:
3b) Valid & saturated pixels
4b) Q-subsample QSx
5b) Temperature
Figure 13: 2-wire communication sequences:
measurement (above) and data reading (below)
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
10 / 30
Datasheet epc600 - V1.3
www.espros.ch
A command, including the measurement type and integration time, sent by the microprocessor to the 2-wire interface, sets the epc600-chip
configuration and triggers the measurement. The device operates standalone to perform the distance measurement. When it is finished,
the chip responds by sending the results: the distance value. It is without any calibration, correction or offset compensation. Based on this
data, the microprocessor computes the final measurement result in regards to the necessary correction factors e.g. quality, offset, ambientlight and temperature drift. The actual result must be read first before starting the next capture cycle. The detailed method of communica tion and the instruction set are described in chapter 3.: Instruction Set. For more details refer also the the epc600 Handbook.
The epc600 range-finder uses the time-of-flight principle. It is implemented with a repeating, continuous-mode modulation signal during the
measurement phase (refer to Figure 14). Consequently, only signals returning within the maximum time slots can be detected unambiguously. This corresponds for the epc600 to a maximum operating range of 15m. Strongly reflected signals outside of this range may there fore interfere with the measurement.
1.3.2. System sensitivity, integration time and operating range
The operational range of the complete system is limited by the sensitivity of the receiver as well as by the illumination power emitted by the
modulating light source (e.g. LED).
Light
Intensity
Measurement time tMEAS = 4x integration time tINT + system time tSYS
Integration time tINT
Ambient-light DC EDC
Modulated light EAC-PP
(peak-to-peak)
Time
Figure 14: The light detected by the receiver
The system sensitivity consists of two factors: The hardware sensitivity SAC of the photo-sensor (refer to chapter: Timing and optical Characteristics) and the integration time t INT (exposure time).
The measurement evaluation is done by computing the distance out of 4 samples received in one measurement cycle t MEAS. A sample is
the collected power of the receiving light signal during the integration time (refer to E AC in Figure 14). This means the system's sensitivity
relates to the integration time: The longer the integration time, the more sensitive the measurement.
The measured irradiance EAC (uncalibrated) at the sensor surface can be calculate out of the AC sensitivity S AC, the used integration time
tINT-AC, the reference integration time t INT-REF-AC and the amplitude AAC of the received modulated signal (refer to chapter 1.3.4.Quality of the
measurement result) in the following way:
E AC = S AC ⋅
t INT-REF-AC
⋅ A AC
t INT-AC
e.g.
E AC = 31
2
nW/ cm 103 μ s
⋅
⋅1'000 LSB = 16 μ W /cm2
LSB
205 μ s
Illumination power, remission of the object (reflectivity), sensitivity of the sensor together with the integration time are limiting the distance
operational range. For more detailed information, refer to epc's application note: AN02 Reflected power calculation.
It will probably not be possible to cover the full operational range within one integration time step due to the dynamic range of the receiver's electronics. The possibilities to extend the operating range or to influence the response time are:
■ to adapt the integration time correspondingly to the necessary sensitivity as demonstrated in Figure 15.
■ or alternatively: use an additional, external LED driver to adjust the illumination to the needed system sensitivity level (refer to
chapter 1.3.9.: Extended operating range).
The easiest way is to adapt the integration time to the current illumination situation (e.g. in Figure 15). With the command formats, which
allow adjusting of the integration time, it is easy to do. It is simple to change the integration time on the fly: a capture is initiated by a com mand sent to the chip.
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
11 / 30
Datasheet epc600 - V1.3
www.espros.ch
Exposure time (Integration time)
4⋅T0
range
n+2
2⋅T0
range
n+1
T0
operational
range
n
0.5⋅T0
0.25⋅T 0
range
n-1
range
n-2
R0
2√2
Distance R
R0
2
R0
√2
R0
R0⋅√ 2
R0⋅2
Figure 15: Example of operating ranges as a function of distance and exposure time
based on doubling the light power to the sensor per range
1.3.3. Ambient-light suppression
An important function of the range-finder is the ability to separate the self-emitted and reflected modulated light E AC from the ambient light
EDC (refer to Figure 14). The built-in ambient-light suppression E Sup removes the DC or low frequent signal distortions, caused by foreign
light sources e.g. sunlight, daylight, room illumination, etc., from the measuring signal. The user has not to take care of this, it is done by
the chip automatically. To see the capability of this function, refer to Table 3 for example values as a function of the wavelength and compared to sunlight.
Similar to the system's sensitivity of the modulated light, is the ambient-light suppression a function of the integration time. The longer the
integration time, the more the measurement becomes sensitive to the ambient-light.
Notes:
■ The ambient-light suppression of the chip must not be confused with the ambient-light measurement command. It is a fixed built-in functionality, which is removing the DC light component from the AC measurement signal only.
■ A DC or AC photo-signal can be generated by ambient-light (e.g. sunlight) or by cross-talk from the IR-LEDs. If this signal is above the
stated maximum value, then the sensor or the input electronics are saturated. This blocks the detection of the AC modulation signal.
1.3.4. Quality of the measurement result
The epc600 provides information on the quality and the validity of the received optical signal. This reflects the confidence level of the mea surement result. The better the received signal, the better and more precise the distance measurement will be.
The primary quality indicator for the measured distance data is the amplitude value of the received modulated light A AC.
After each measurement this needs to be calculated from the Q-subsamples QSx delivered by the chip(r efer to chapter 3.2.4. Response:
Q-subsample QSx). This amplitude value is the feedback parameter that is used to set the integration time for the next measure ment.
A AC =
√
2
(QS1+QS3)2
1 (QS0+QS2)
⋅
+
4
4
4
Quality indicator:
Status & reason:
Weak illumination:
e.g.
A AC < 50 LSB
The signal has a reduced accuracy, because it is above, but close to the noise level.
Action:
Increase integration time for the next measurement
Quality indicator:
Status & reason:
Sufficient illumination:
e.g.
50 LSB < A AC < 100 LSB
The signal quality and the accuracy is sufficient and not close to any limits. Noise level may be increased.
Action:
No action necessary. See note below
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
12 / 30
Datasheet epc600 - V1.3
www.espros.ch
Quality indicator:
Status & reason:
Excellent illumination:
e.g. 100 LSB < A AC < 1'000 LSB
The signal quality and the accuracy is excellent and not close to any limits.
Action:
No action necessary. See note below
Quality indicator:
Status & reason:
Too bright illumination:
e.g. 1'000 LSB < A AC
The signal is close to or above the limit of too much light (maximum signal limit).
Action:
Decrease integration time for the next measurement. See note below
Note:
Generally, the higher the received signal, the better and more precise the distance measurement will be. However, it is good practice to
control the integration time such that an amplitude value between 100 ... 200 LSB is achieved. Higher values will only slow down the acqui sition rate due to longer integration times, but are not significantly improving signal to noise ratio.
The quality indicator for the ambient-light measurement is the ambient-light amplitude ADC.
The rules to apply are the same as for the modulated light amplitude.
The quality indicator for the distance noise is the ratio AMR of ambient-light to the modulated light. This value may be calculated and used
additionally to the above amplitude value if the respective application is subject to intense ambient light.
Quality indicator:
Ratio AMR of ambient-light to modulated light
AMR[dB ] = 20⋅log
( )
EDC
EAC
e.g.
AMR[dB ] = 20⋅log
(
)
792μ W /cm2
= 34dB
2
16μ W /cm
Refer for EDC to chapter 1.3.5. Ambient-light measurement (optical power-meter) and for EAC to chapter 1.3.1. Distance measurement.
Status & reason:
Action:
This ratio is one of the influencing factors on the distance noise (refer to Table 2, section Distance noise)
< 60 dB: excellent
No action necessary.
< 70 dB: sufficient
> 70 dB: weak
Is a lower noise level needed, do the next measurement with a longer integration
time or an increased illumination power.
Do the next measurement with a longer integration time or an increased illumination
power.
There are also validity indicators delivered by the chip after a measurement. These will help to detect saturated pixels as a result of too
much illumination or too long integration time.
Validity indicator:
Meaning:
How to use:
MIN_VALID_PIX (refer to chapter 3.2.3.Response: Valid & saturated pixels )
The chip internally detects saturation of pixels and internal signal electronics and flags them non-valid. Since there
are four samples for one measurement, a different number of saturated pixels may internally be detected for each of
the samples. However, the chip output number is the valid pixel count from the sample with the least valid pixels.
The subsequent distance calculation routine uses only this subset of valid pixels. Therefore, the higher the
MIN_VALID_PIX value, the higher the accuracy and reliability of the distance data will be.
A low MIN_VALID_PIX value most likely indicates a global saturation of the pixel field resulting from a too long inte gration time and/or a too bright illumination. Such a state will also display in the amplitude value (see above).
However, there may be situations where the global illumination is appropriate but there are individual pixels driven into
saturation. This can occur if very bright (high-reflecting) areas are within the scene and blind individual pixels(e.g. a
painted machine part with a small, chrome-polished area). In such a situation, the MIN_VALID_PIX count may help to
differentiate if the shot is still containing enough valid pixels for a reliable distance calculation.
What values are acceptable has to be established within the context of the respective application. As a safe value we
recommend to use only measurements with a value of MIN_VALID_PIX>60.
Validity indicator:
MAX_SAT_PIX (refer to chapter 3.2.3.Response: Valid & saturated pixels )
Meaning:
The MAX_SAT_PIX is a complementary value to the above MIN_VALID_PIX value. But it counts only the saturated
pixels (not the subsequent signal electronics). The lower the MAX_SAT_PIX value, the higher the accuracy and reliability of the distance data will be.
Like above.
As a safe value we recommend to use only measurements with a value of MIN_SAT_PIX<5.
How to use:
Remember, the epc600 chip is using a sensor array with 64 pixels and the single distance output is an average of these pixels. The two
parameters above indicate how many of these pixels are actually used for this average calculation. Refer to the epc600 Handbook for
more details on the averaging algorithm.
Table 6 shows a quality decision matrix as a summary of the validity and quality parameters for the distance measurement.
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
13 / 30
Datasheet epc600 - V1.3
www.espros.ch
Step
Sensor status
Saturated pixels
Valid pixels
Modulated light
amplitude
Ambient to
modulated light
MAX_SAT_PIX
MIN_VALID_PIX
AAC
AMR
Action
1
Saturation or bright object within scene
> max. limit (e.g. 5)
Repeat measurement with
decreased integration time and/or illumination
2
Saturation or bright object within scene
< max. limit
< min. limit (e.g. 60)
3
Over-exposure or bright
object within scene
< max. limit
> min. limit
> 1'000 LSB
Repeat measurement with
decreased integration time or illumination
4
No object detected
< max. limit
> min. limit
<
Repeat measurement with
increased integration time or illumination
5
Too much ambient-light
< max. limit
> min. limit
50 LSB … 1'000 LSB
> 60 db (or > 70 dB)
Repeat measurement with
increased integration time or illumination
6
Object detected
< max. limit
> min. limit
Excellent: 100 … 1'000 LSB
Sufficient
50 … 100 LSB
< 60 db (or < 70 dB)
No action necessary
Repeat measurement with
decreased integration time and/or illumination
50 LSB
Note: min. and max limits are customer defined acceptable values depending on the application
Table 6: Quality decision matrix
1.3.5. Ambient-light measurement (optical power-meter)
Instead of reading distance data, the epc600 chip can measure the ambient-light level (Refer to 3.2.1.: Command: Commands & Integration times and 3.2.5.: Response: Ambient-light level). Functions of this feature are:
■ Use to compensate deviations in the distance measurement caused by the presence of ambient-light.
■ Monitor the ambient-light level during the distance measurement to prevent faulty conditions.
■ Use the ecp600 as an optical power-meter (“Luxmeter”) e.g. for brightness control.
■ or in combination e.g. where the presence or absence of an object in the environmental illumination needs to be controlled.
The measured irradiance E DC (uncalibrated) of the received ambient-light at the sensor surface can be calculate out of the DC sensitivity
SDC, the used integration time t INT-DC, the reference integration time t INT-REF-DC and the amplitude A DC of the received modulated signal (refer to
chapter 3.2.5.: Response: Ambient-light level) in the following way:
E DC = S DC⋅
t INT-REF-DC
⋅ A DC
t INT-DC
e.g.
E DC = 12.3
2
nW/cm 103 μ s
⋅
⋅1'000 LSB = 792 μ W /cm2
LSB
1.6 μ s
Notes:
■ The quality indicator for the ambient-light measurement i s the ambient-light amplitude A DC. The rules to apply are the same as for the
modulated light amplitude.
■ The ambient-light measurement is a metering functionality only, which can be used for distance correction or ambient-light reading. It is
completely independent of the chip internal ambient-light suppression function that eliminates DC light components from the measure ment signal (refer to chapter 1.3.3.: Ambient-light suppression).
1.3.6. Temperature metering
An on-chip temperature sensor provides uncalibrated temperature readings. The data access follows the protocol in Figure 13, second
section.
■ This allows compensation of signal drifts caused by changing thermal conditions in the light source and the sensor.
■ If the user does his own calibration (e.g. °C or F), he can use it as a temperature sensor too.
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
14 / 30
Datasheet epc600 - V1.3
www.espros.ch
1.3.7. Measurement sequence
A basic possible measurement flow is given in Figure 16:
■ Execute a distance measurement and check the validity and quality of the signals. If action is needed, act accordingly.
■ If the camera operates in an ambient-light changing condition, occasionally read the ambient-light for quality check and compensation.
■ In thermally changing conditions, occasionally read the temperature for compensation.
■ Calculate, based on the correction data, the final distance value – or whatever is needed.
START
measurement
increase
integration time
MEASUREMENT
distance
decrease
integration time
READ
pixel status
validity?
sat. pixel > max. limit (e.g. 5)
all other
validity?
valid pixel < min. limit (e.g. 60)
READ
Q-subsample QSx
Calculate
mod. amplitude AAC
AAC < 50 LSB
No object ?
quality?
AAC > 1'000 LSB
all other
MEASUREMENT
ambient-light
Calculate ratio AMR
ambient to mod. light
AMR > 60 dB (or >70dB)
optional
quality?
all other
READ
temperature
optional, e.g. once per second
AAC < 100 LSB
all other
Calculate
corrected distance
quality?
yes
continue?
no
END
measurement
Figure 16: Principle measurement flow
This flow is not only for detecting objects: It is also possible to observe and track the object (once captured).
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
15 / 30
Datasheet epc600 - V1.3
www.espros.ch
1.3.8. Calibration and compensations
Due to the fact that the range-finder chip does not know its surrounding environment and the phase-shifts caused by the electronic implementation and also due to manufacturing tolerances, a calibration of the sensor is necessary.
Whereas a simple light barrier doesn't need the same accuracy as a range-finder, the compensation and the required calibration is depen dent on the application.
Influencing variables for various attributes are:
■ Distance: Offset, Slope scaling, Linearity, Reflectivity, Quality, Ambient-light, Integration time, Temperature.
■ Reflectivity of the object: Quality, Ambient-light.
■ Ambient-light: Offset, Slope scaling, Linearity, Integration time, Temperature.
■ Temperature: Offset, Slope scaling, Linearity.
These compensations are necessary for the microprocessor to correct the raw distance data in the final measurement.
1.3.9. Extended operating range
The epc600 is a range-finder designed as a system-on-chip for minimum part count circuits. Therefore, a LED driver is integrated on-chip.
In cases where the illumination, achieved with the built-in driver, is not sufficient to detect near and far objects in the expected operational
range or in the necessary response time, the epc600 chip can be used with a more powerful external LED driver (refer to chapter 2.5. External LED driver).
1.3.10. Multi range-finder application
Light barriers are not always operating in a single sensor application. In some applications, more than one sensor is deployed to partially
or entirely cover the same observation field. The epc600 range-finder uses signal-processing based on the sinusoidal modulation theory of
the time-of-flight principle.The LEDs are modulated with 10MHz square-wave and a duty cycle of 1:1. There is no coding in the modulation
signal to make each device unique. To date, in multi range-finder applications, cross-talk between the signals of closely placed individual
sensors can occur.
The single shot principle of the epc600 chip allows an easy synchronization of multiple sensors by a fixed time synchronization between
range-finder devices (sequencing of sensors).
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
16 / 30
Datasheet epc600 - V1.3
www.espros.ch
2. Hardware Design
2.1. What performance can be achieved?
A typical example of an application is a very small, single spot distance gauge (refer to Figure 17).
Illumination LEDs
Figure 17: Low power, high performance distance gauge.
Size: 32 x 22 x 25 mm
epc600 chip
with IR filter on top
Figure 18: Chip on PCB board
In this example, a range of up to 4m can be expected on white targets when using: two SFH4059 LEDs directly driven by the LED pin with
a collimator lens of 17mm focal length, a receiver lens of approx. 15x15mm with a focal length of 17 mm and an integration time t int of
410µs.
t RESPONSE = 2⋅(4⋅t INT+0.798ms) + 0.1ms = 4.976ms
The response time in this application is:
(refer also to chapter: Response time).
D1A
BAV99
D1B
BAV99
VDD +8.5V
C2
1μ
C10
27p
+
C1
10μ
+5V
Microprocessor
Y1
4MHz
16
XTAL1
LED1
XTAL2
NC3
epc600
C11
27p
D1
BAS40
10
VDD
15
4
3
GNDM
NC4
VDDCORE
VDDT
VDDPLL
R4
10k
VREF
VDDIO
19
SDATA
20
SCLK
1
R4
1k
18
SDATA
VDDPX
SCLK
VDDHPX
HLLED/NC2
VDDCP
NC1
VDDBS
GND GNDA GNDPLL
21
22
24
LED1
SFH4059
LED2
SFH4059
12
13
R3
0R
14
2
17
5
7
8
9
11
6
C4
1μ
C5
3μ3
C7
3μ3
C9
10n
R1
27R
C3
1μ
R2
4k7
C12
100n
C6
3μ3
C8
100n
GNDLED
23
VDDBS -5.0V
GND
GND
Low Z, fast switching connection (as short and wide conductors as possible)
Figure 19: Minimum part count application
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
17 / 30
Datasheet epc600 - V1.3
www.espros.ch
2.2. General Hardware Configuration
The general hardware configuration section covers all design aspects for an epc600 circuit.
2.3. Power Supply, Clock generation
The external voltage supplies are +8.5V DC as a main supply and -5.0V DC as a bias voltage. Both supplies need to be stable, well regu lated and with a low level of noise and ripple voltage (because the epc600 chip is a sensitive, highly amplifying device).
All other necessary voltages are generated on-chip. The internally generated voltage levels V SC (see Table 4) have to be taken into consideration in order to choose the right components for the design.
All necessary power supply decouplings and the supply of the external reference clock have to be designed according to Figure 20 and
Table 7. Capacitors C3 – C9 are used for decoupling of the internally generated voltages.
The Schottky diode D1 is vital to ensure a correct power-up of the device.
VDD +8.5V
+
C1
C2
D1
10
VDD
C10
15
Y1
16
C11
XTAL1
LED
XTAL2
NC3
epc600
+5V
4
3
GNDM
NC4
VDDCORE
VDDT
VDDPLL
R3
VREF
VDDIO
19
20
1
18
R1
SDATA
VDDPX
SCLK
VDDHPX
HLLED/NC2
VDDCP
NC1
VDDBS
GND GNDA GNDPLL
21
22
24
12
13
R2
14
2
C3
17
C4
5
7
C5
8
C6
9
C7
11
C8
6
C9
VDDBS -5.0V
GNDLED
23
GND
Figure 20: Main power supply decoupling and clock supply
Part No. Pin
Pin No.
Component value
Min.
Nom.
Max.
10μF
VSC
Type
C1
VDD
10
+8.5V
C2
VDD
10
+8.5V
Ceramic X7R
C3
VDDCORE
2
1μF
1μF
3.3μF
+1.8V
Ceramic X7R
C4
VDDPLL
17
1μF
1μF
3.3μF
+1.8V
Ceramic X7R
C5
VDDIO
7
3.3μF
3.3μF
10μF
+5.0V
Ceramic X7R
C6
VDDPX
8
3.3μF
3.3μF
10μF
+5.0V
Ceramic X7R
C7
VDDPXH
9
3.3μF
3.3μF
6.8μF
+10V
Ceramic X7R
C8
VDDCP
11
10nF
100nF
100nF
+12V
Ceramic X7R
C9
VDDBS
6
10nF
10nF
20nF
-5.0V
Ceramic X7R
C10
XTAL1
15
27pF
+1.8V
Ceramic NP0
C11
XTAL2
16
27pF
+1.8V
Ceramic NP0
Y1
XTAL1 & XTAL2
15 & 16
4 MHz
D1
VDD & VDDCP
10 & 11
R1
HLLED
1
R2
NC4
R3
SDATA
1μF
Crystal-oscillator
Schottky diode
1kOhm
+5.0V
Resistor
14
zero Ohm
+5.0V
Resistor
19
see chapter 2-wire serial interface
+5.0V
Resistor
Leave open the pins NC1, NC3 and VREF. They do not require any termination.
Table 7: Component values
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
18 / 30
Datasheet epc600 - V1.3
www.espros.ch
2.4. On-chip LED driver
A feature for the minimum part count system is the on-chip LED driver. Figure 21, Figure 22 & Figure 23 show examples for possible circuits. The design has to take in consideration that these LEDs are switched very fast (e.g. 10MHz square-wave) and with high power
(<180mA). Suggested are high speed LEDs with short switching times e.g. Osram SFH4059, Vishay VSMB2000, Stanley DNK5306. The
layout needs to be well decoupled and with low Z conductors.
Notes:
■ Take care that the voltage at pin LED do not exceed the specified operational range of maximum +5V.
■ The signal processing of the epc600 chip is based on a sine-wave modulated light-signal. All descriptions in this manual are related to
this. However, to simplify the LED driver circuit as well to reduce the power-losses of the LED, the chip uses a square-wave modulated
signal for the LED. This change together with all the other non-linear influences on the signal path leads to only a small error, which can
easily be corrected in the measurement data (refer to chapter 1.3.8. Calibration and compensations).
LEDs with a +5V supply
If a +5V supply is available, the LEDs can simply be supplied by this as shown in Figure 21. Resistor R1 limits the LED current <180mA.
For the LED power dissipation calculation, refer to chapter 3.3.6.: Cycle times & response time.
VLED = 5V
LED1
SFH4059
LED2
SFH4059
epc600
+
LED
R1
9R
GND
C3
100nF
C4
10μF
GNDLED
GND_LED
GND
Low Z, fast switching connection
Figure 21: Short range application
with +5Vdecoupled LED supply
Short range application design (LED supply from +8.5V)
The circuit in Figure 22 drives two power IR LEDs. The output LED is driven by an open drain switching transistor. The illumination intensi ty of the LEDs is defined by the current flowing through the resistor R1. For the output LED = on, the current of the resistor R1 is <180mA.
In order to have safe voltage operating conditions for the output LED (max. +5V), there is a minimum current of <1mA flowing through the
LED diodes and the D1 diodes in the off-state. This also gives the advantage of the enhanced switching performance for the LEDs. This
off-current is set by the resistor R2. C3 and C4 are the charge capacitors to supply the LEDs. In order to support the required fast switch ing, C3 shall be of a ceramic type. The decoupling of the supply of the epc600 chip is done by C1 and C2 (ceramic type). The resistor R3
decouples the LED feeding circuit from the ep600 supply. The voltage drop of the diodes D1A and D1B adjust the voltage supply level to
the LED supply level. The advantage of this concept is that it gives a good decoupling between the epc600- and the LED-supply.
For the LED power dissipation calculation, refer to chapter 3.3.6.: Cycle times & response time.
VDD = 8.5V
VDD = 8.5V
+
C1
10μF
R3
15R
GND
GND
VDD
R1
27R
GND
GNDLED
C3
100nF
C2
100nF
C4
10μF
R2
4k7
R4
27R
GND
Figure 22: Short range application
with a decoupled LED supply
Characteristics subject to change without notice
C3
100nF
LED
GND
Low Z, fast switching connection
© 2014 ESPROS Photonics Corporation
LED3
SFH4059
epc600
+
LED
GND
LED1
SFH4059
LED2
SFH4059
LED2
SFH4059
epc600
C2
100nF
D1B
BAV99
LED1
SFH4059
VDD
+
C1
10μF
D1A
BAV99
GNDLED
R3
4k7
Low Z, fast switching connection
Figure 23: Mid range application
with a minimum part count circuit
19 / 30
Datasheet epc600 - V1.3
www.espros.ch
Mid range application design (LED supply from +8.5V)
The circuit of Figure 23 is a minimum part count design for a more powerful illumination (3 LEDs are equal to 50% more illumination ener gy).
The design considerations are exactly the same as before. The difference is the additional third LED3, which replaces the diodes D1A and
D1B, in order to have more powerful illumination. As it is used as a minimum part count design, the decoupling between the LED supply
circuit and the epc600 supply is not of the same quality as in the short range example before. Therefore, the layout design regarding the
noise and ripple voltage has to be done very carefully.
2.5. External LED driver
For a more powerful, sensitive or fast system application with an epc600 chip, the use of an external LED driver is an option. The design
has to take into consideration that the LEDs are modulated at high frequencies (e.g. 10MHz) and with high power. So far, the layout needs
to be well decoupled and with low Z conductors. The schematic has to follow the correct signal inversions as given in Figure 24. This is important in order to have the correct phase for the modulation.
Note: Take care that the voltage at pin LED do not exceed the specified operational range of maximum +5V.
epc600's pin LED is driven by an open drain switching transistor. The pull-up termination resistor R1 tied to the V_LOGIC supply (+5V)
guarantees safe voltage operating conditions for the output LED. The modulation signal of output LED feeds a fast inverting digital buffer
IC1. It drives the fast switching transistor T1. T1 switches the current through LED1-LEDn on/off in order to modulate the light. Output LED
= low corresponds to light = on.
As opposed to the on-chip driver, such a design can have additional light levels as the circuit in Figure 24 shows. An I/O port of the microprocessor switches the intensity to the LOW or HIGH level. IC1 and IC2 are the necessary selecting logics to drive the transistors T1 and
T2. The illumination (current through LED1-LEDn) is controlled by R2 and R3 for the high and the low illumination level.
V_LED
LED1
VDD +8.5V
C1
100nF
VDD
LEDn
V_LOGIC
epc600
R2
R1
Microprocessor
LED
SCLK
SDATA
2-wire interface
GND
C2
+
C3
IC1
T1
SCLK
SDATA
R3
IC2
GNDLED
T2
GND_LED
GND
HIGH
LOW
Figure 24: Long range or fast response application (principal schematic)
Advantages of this circuit are: the free design of the illumination power (number of LEDs), the additional selectable light levels for extend ing the operational range, the independent voltage supply for the LEDs and the strong decoupling of the epc600 supply and LED circuitry.
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
20 / 30
Datasheet epc600 - V1.3
www.espros.ch
3. Instruction Set
The 2-wire serial interface allows the user to communicate with the epc600 chip. The graph of the principle communication flow is in
Figure 13.
Starting a measurement, reading the result and setting the correct user parameters for operation are the main functions. All configurations
are set at run-time, are loaded immediately and are not stored in the chip.
3.1. 2-wire serial interface
The interface is for single slave use. It is targeted to operate up to a 10MHz clock frequency. Only 2 wires, one bidirectional data transmis sion SDATA and a clock line SCLK, are needed (refer to Figure 25). This allows the use of a tiny microprocessor as a controller for the
chip. Based on a handshake protocol the chip is either receiving or transmitting data during active clock cycles.
+5.0V
VDD +8.5V
VDD
VDD
XTAL1
LED
XTAL2
NC3
Microprocessor
epc600
+5.0V
VDDT
VDDCORE
GNDM
VDDPLL
VREF
R1
VDDIO
I/O1
SDATA
I/O2
SCLK
2-wire interface
LEDF
VDDPX
VDDHPX
HLLED/NC2
VDDCP
NC1
GND
GND
GND
GND
VDDBS
GNDA
GNDPLL
GNDLED
Figure 25: 2-wire interface wiring (Note: For details to R1 see section SDATA line)
3.1.1. SCLK line
SCLK is the serial clock signal. It is unidirectional and always driven by the microprocessor. It is switched between LOW and HIGH state.
The maximum 'HIGH' pulse length is not defined. The maximum 'LOW' pulse length must be < 1ms.
ERROR handling: A 'LOW' pulse > 1ms will reset the epc600 chip.
3.1.2. SDATA line
SDATA is the serial data line. It is used in a bidirectional way. It is switched between LOW and high-ohmic state.
Depending on the communication direction, it is either driven to LOW by the microprocessor or the epc600 chip (refer to Figure 25). A
“wired-OR” compatible I/O circuitry on either side is used to handle unexpected error situations. It avoids permanent damage of each party
in case they drive opposite logic values.
The microprocessor can achieve the Wired-OR connection by using programmable open-drain I/O pads, or writing a permanent logic LOW
to the output and switching the line between the high-ohmic and transparent modes. A pull-up resistor R1 to +5.0V will terminate the line to
logic HIGH during the high-ohmic state. If the rise time of the SDATA line is not fast enough, the user may either enable an embedded pullup resistor in the microprocessor or add on each side of the line, close to the pins, external resistors in parallel.
ERROR handling: If the epc600 device detects a communication error, it will pull the SDATA line permanently to LOW until the interface will
be reset.
The general waveform definition and timing are listed in Figure 26 and Table 8.
In the idle state, the SCLK and SDATA lines are in the high state (outputs are in tristate mode terminated with a pull-up resistor). The trans mission is always initiated with a start bit on the SDATA line: SDATA = low. This forces the microprocessor to clock the SCLK line with the
necessary number of cycles for sending or reading the data. The falling edge of the clock puts the data to the SDATA line. At the time of
the rising edge, the data is valid and readable. After the last rising clock edge the sender unlocks the SDATA line and both lines remain in
the high state.
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
21 / 30
Datasheet epc600 - V1.3
www.espros.ch
Idle
Sender writes to SDATA
SCLK
CLK1
LOW
CLK2
high-ohmic
LOW
IDLE
S
trfSCLK
tH
MSB
tLSBH
CLKn
tDH
tL
≈≈
tDR
SDATA
trfSCLK
tSCKL
≈
tS
HIGH
Idle
LSB
Sender pulls SDATA to low:
Hand-shake signal for WRITE
IDLE
Sender changes mode:
from WRITE to IDLE
Figure 26: General waveforms for 2-wire transmission (telegram)
Symbol
Parameter
Min.
SCLK
2-wire serial clock
SDATA
Serial data, bidirectional transmission
tSCLK
Cycle time of SCLK
100
ns
tH
High period of SCLK
50
ns
tL
Low period of SCLK (refer to ERROR handling)
trfSCLK
Rise or fall time of SCLK (20% - 80% of signal amplitude)
tS
First negative SCLK edge after negative edge of SDATA
100
ns
tDR
Data ready before positive SCLK edge
50
ns
tDH
Data hold after positive SCLK edge
0
ns
tLSBH
Data hold after positive SCLK edge of last bit transmitted (LSB)
0
ns
50ns
Typ.
Max.
Unit
1.0ms
10
ns
Table 8: General timing 2-wire transmission
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
22 / 30
Datasheet epc600 - V1.3
www.espros.ch
3.2. Commands & responses
The epc600 device works on a task principle: The chip is in a idle state and performs a single measurement or a read-out on command
only (refer to Figure 13).
The microprocessor sends a command to the chip. It is processed immediately. The tasks are: Execute a measurement or read data.
When the processing of the instruction is finished, then the chip sends back the answer to the controller by default. Refer to Figure 12 and
Figure 13.
The command format always has 8 bits, including 4 bits for command itself (C0-C3) and 4 bits to set the integration length (I0-I3). Bit 7
(MSB) is transmitted first, bit 0 (LSB) last.
The response format is always 16 bits. Bit 15 (MSB) is transmitted first, bit 0 (LSB) last.
3.2.1. Command: Commands & Integration times
Name:
Bit
Command & Integration time
7
6
5
4
3
2
1
0
C3
C2
C1
C0
I3
I2
I1
I0
Description
CMD:
INT:
CMD [3:0]
INT [3:0]
Command to start the measurement with a defined integration time or to read data.
Description
Read Q-subsample QS0
CMD
0001
INT
0000
epc600 response
Q-subsample QS0
Waiting time
tACC = 3μs
Read Q-subsample QS1
Read Q-subsample QS2
0010
0011
0000
0000
Q-subsample QS1
Q-subsample QS2
tACC = 3μs
tACC = 3μs
Read Q-subsample QS3
Read temperature
0100
0101
0000
0000
Q-subsample QS3
Temperature
tACC = 3μs
tACC = 3μs
Read pixel status
Measurement of distance
Note: Modulated light is emitted
0110
1000
0100
see INT
Valid & saturated pixels
Distance
tACC = 3μs
tMEAS
Measurement of ambient-light level
Note: No light is emitted
Don't use
1101
see INT
Ambient-light level
tMEAS
Others
Sets the integration time for the measurement. T he measurement time is tMEAS = 4x integration time + 770μs.
Note: A doubling of the integration time is equal to a doubling of the illumination in the scenery.
The integration times below in the table are for a LED modulation frequency of 10MHz.
Time
INT
Time
INT
Time
408 μs
INT
Time
INT
1000
6.56 ms
1100
1.60 μs
0000
25.6 μs
0100
3.20 μs
0001
51.2 μs
0101
818 μs
1001
13.2 ms
1101
6.40 μs
0010
103 μs
0110
1.64 ms
1010
26.3 ms
1110
12.8 μs
0011
205 μs
0111
3.28 ms
1011
52.6 ms
1111
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
23 / 30
Datasheet epc600 - V1.3
www.espros.ch
3.2.2. Response: Distance
Name:
Bit
Distance
15
Q3
Description
DIST:
14
Q2
13
Q1
12
Q0
11
10
9
8
7
6
5
4
3
2
1
0
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
Don't care
DIST [11:0]
Distance value
Data format: unsigned 12 bit integer; Unit: LSB
For 10MHz LED modulation frequency the following values and formulas apply:
1 LSB = 0.5 cm. Minimum DIST = 0d ≙ 0m. Maximum DIST = 3'000d ≙ 15m.
D [cm] = DIST ⋅
The basic calculation formula is
D
DOFFSET
1'500 cm
+ DOFFSET
3'000LSB
Distance in centimeters
Offset compensation, needs to be evaluated by a calibration of the sensor. Refer also to
chapter Calibration and compensations.
Note:
The epc600 chip is using a sensor array with 64 pixels. The distance value output is an average calculation. Refer also to
the epc600 Handbook for more details.
3.2.3. Response: Valid & saturated pixels
Name:
Bit
Description
MIN_VALID_
PIX:
Valid & saturated pixels
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Q0
D6
D5
D4
D3
D2
D1
D0
Q0
D6
D5
D4
D3
D2
D1
D0
0
MAX_SAT_PIX [6:0]
0
MIN_VALID_PIX [6:0]
During the measurement, one of the 4 samples has used only this number of valid pixels per sample for the averaging. The
remaining pixels were detected as non-valid. A pixel is valid if the measurement value is: not in the pixel saturation and be low the input electronics saturation. Refer to chapter 1.3.4.: Quality of the measurement result.
Data format: unsigned 7 bit integer; Output range: 0d ... 64d.
Note: Distance values are valid as long as MIN_VALID_PIX >0 (minimum condition).
MAX_SAT_
PIX :
During the measurement, one of the 4 samples has skipped / not used this number of saturated pixels during averaging. A
pixel is marked as saturated if the sensor has detected a pixel signal value that exceeds the linear range of the pixel. Refer
to chapter 1.3.4.: Quality of the measurement result.
Data format: unsigned 7 bit integer; Output range: 0d … 64d
3.2.4. Response: Q-subsample QSx
Name:
Bit
Description
QSx:
Q-subsample QSx
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Q1
Q0
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
0
0
QSx [13:0]
Q-subsample x of the last measurement.
Data format: signed 14 bit integer (two's complement); Unit: LSB
For the calculation of the signal quality refer to chapter 1.3.4.: Quality of the measurement result.
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
24 / 30
Datasheet epc600 - V1.3
www.espros.ch
3.2.5. Response: Ambient-light level
Name:
Bit
Description
AMBIENT:
Ambient-light level
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Q1
Q0
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
0
0
AMBIENT [13:0]
Ambient-light
Data format:
Output range:
signed 14 bit integer (two's complement); Units: LSB; A/D conversion value.
Refer to Table 2: DC sensitivity and DC dynamic range
Note: Small negative numbers can occur due to noise.
A DC [LSB] =
The basic calculation formula for the amplitude A DC is
AMBIENT
4
Note:
The epc600 chip is using a sensor array with 64 pixels. The ambient-light value output is an average calculation. Refer also
to the epc600 Handbook for more details.
3.2.6. Response: Temperature
Name:
Bit
Description
TEMP:
Temperature
15
14
13
12
11
10
9
8
7
Q3
Q2
Q1
Q0
D11
D10
D9
D8
D7
0
0
0
0
6
5
4
3
2
1
0
D6
D5
D4
D3
D2
D1
D0
TEMP [11:0]
Temperature value
Data format: unsigned 12 bit integer; Units: LSB; A/D conversion value
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
25 / 30
Datasheet epc600 - V1.3
www.espros.ch
3.3. Communication tasks
3.3.1. Measurement sequence (Distance or ambient-light)
uP polls SDATA
epc600: idle
Response:
epc600 writes SDATA
uP reads SDATA
Idle
S
SDATA
C3
C2
C1
C0
I3
I2
I1
MSB
uP checks SDATA:
high = continue;
low = error
≈
SCLK
≈
uP writes SDATA
epc600 reads SDATA
I0
S
epc600 measures
LSB
uP pulls SDATA to low:
Command hand-shake signal to epc600
Q3
Q2
Q1
Q0
D11
D10
MSB
≈≈
Command:
≈
Idle
D1
D0
LSB
epc600 pulls SDATA to low as soon measurement is finished:
Data ready hand-shake signal to uP
tMEAS
Figure 27: Measurement sequence
■ Before and after, the microprocessor performs an access to the epc600, the SDATA line should be checked for an error according to
Figure 27. If SDATA is LOW, this indicates an ERROR in communication.
■ The microprocessor initiates the communication with a start bit on the SDATA line followed by actively clocking the line SCLK and the
command transmission.
■ After completion of the command, the epc600 chip starts the measurement. Meanwhile, the microprocessor waits for a response.
■ The epc600 chip sets the start bit on SDATA when the measurement is executed and the data are ready ( tMEAS, refer to Table 9).
■ Now the microprocessor can read out the data by active clocking.
Symbol
Parameter
Min.
tMEAS
Measurement duration. Depends on the selected integration time
0.8
tACC
Propagation delay of the epc600 after command transmission
tRST
Reset signal to the epc600. The time SCLK must be pulled low.
tREC
Recovery time after reset of epc600
Typ.
Max.
Unit
212
ms
3.0
μs
1.0
ms
4.0
ms
Table 9: Timing of the measurement, read and reset sequence
3.3.2. Read sequence (Valid & saturated pixels, Q-subsample QSx, Temperature)
uP polls SDATA
epc600: idle
uP checks SDATA:
high = continue;
low = error
S
C3
MSB
C2
C1
C0
I3
I2
I1
≈
SCLK
SDATA
Response:
epc600 writes SDATA
uP reads SDATA
Idle
≈
uP writes SDATA
epc600 reads SDATA
I0
LSB
S
tACC
uP pulls SDATA to low:
Command hand-shake signal to epc600
Q3
MSB
Q2
Q1
Q0
D11
D10
≈≈
Command:
≈
Idle
D1
D0
LSB
epc600 pulls SDATA to low as soon data are ready:
Data ready hand-shake signal to uP
Figure 28: Read sequence
The sequence is identical to the above except for the waiting time tACC of the response of the chip (refer to Table 9).
■ Before and after, the microprocessor performs an access to the epc600, the SDATA line should be checked for an error according to
Figure 28. If SDATA is LOW ,this indicates an ERROR in communication.
■ The microprocessor initiates the communication with a start bit on the SDATA line followed by actively clocking the line SCLK and the
command transmission.
■ After completion of the command, the epc600 chip fetches the data. Meanwhile, the microprocessor waits for a response.
■ The epc600 chip sets the start bit on SDATA when the data are ready ( tACC).
■ Now the microprocessor can read out the data by active clocking.
3.3.3. Error detection by the microprocessor
Idle
Reset by uP
tRST
Command:
uP writes SDATA
epc600 reads SDATA
tREC
≈
SCLK
Idle
normal operation ...
S
SDATA
C3
C2
C1
MSB
uP checks SDATA:
detects error
uP checks SDATA:
high = continue;
low = error
uP pulls SDATA to low:
Command hand-shake signal to epc600
Figure 29: Error detection by the uP and the reset sequence
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
26 / 30
Datasheet epc600 - V1.3
www.espros.ch
Before the microprocessor tries to set a start bit, it first checks the SDATA line according to Figure 29. SDATA = LOW indicates an ERROR.
This means that the epc600 chip signals an error status or the interface is faulty.
At the end of the transmission, the microprocessor can check, if the communication was successful: Reads the microprocessor data from
SDATA, the line must go to HIGH (IDLE) after the positive edge of the last clock cycle (refer to Figure 27 and Figure 28). Is this not the
case, the epc600 chip signals an error status or the interface is faulty. Do not use the received data, because it is uncertain, if the last
transmission was successful.
Use the reset sequence for the recovery.
3.3.4. Reset and recovery sequence sequence
Whenever necessary, the microprocessor can reset the epc600 chip. The reasons for the reset are either due to an error detection during
the transmission or in order to resynchronizing the interface. The epc600 interprets a LOW signal > 1ms on the SCLK line as a reset com mand for the chip (Figure 29). After reset, the communication has to restart.
NOTE: After reset sequence, the microprocessor must wait pre-defined amount of time t REC before starting with measurements (Table 9).
3.3.5. Error detection by the epc600 chip
Error
MSB
epc600 write cycle
uP reads SDATA
normal operation ...
MSB
Error
Reset by uP
uP checks SDATA:
high = continue;
low = error
Idle
uP pulls SDATA to low:
Command hand-shake signal to epc600
Command:
≈
LSB
S
MSB
≈≈
MSB
uP write cycle
epc600 reads SDATA
uP write cycle
epc600 reads SDATA
≈
≈
S
Command:
S
uP checks SDATA:
detects error
uP polls SDATA Response:
epc600: idle
≈
SDATA
uP write cycle
epc600 reads SDATA
≈ ≈≈
SCLK
Idle
LSB
a) epc600 detects error:
writes low to SDATA
Command:
Reset by uP
≈
LSB
≈
MSB
epc600 write cycle
uP reads SDATA
≈
uP polls SDATA Response:
epc600: idle
≈
S
≈ ≈≈
SCLK
SDATA
uP write cycle
epc600 reads SDATA
≈
Command:
normal operation ...
S
LSB
b) epc600 detects error:
writes low to SDATA
MSB
uP checks SDATA:
detects error
uP checks SDATA:
high = continue;
low = error
uP pulls SDATA to low:
Command hand-shake signal to epc600
Figure 30: Error detection by epc600
The epc600 chip detects if there are more falling clock edges than necessary for the transmission (see Figure 30). If it happens, the communication is erroneous and the device puts the interface in an ERROR condition by pulling down SDATA = 0. To leave this state, the mi croprocessor has to reset the epc600 chip.
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
27 / 30
Datasheet epc600 - V1.3
www.espros.ch
3.3.6. Cycle times & response time
For a common understanding, we distinguish between the cycle and the response times.
The following examples use:
■ 10MHz modulation frequency at the LED pin.
■ An integration time of 103μs.
■ A 2-wire serial clock SCLK of 1MHz.
Integration time
The integration time tINT is the timeframe in which the light is sampled by the sensor (refer to chapter 3.2.1.: Command: Commands & Integration times). It is equal the exposure time (where a shutter is open for passing the light to the sensor).
Measurement time
The time the epc600 device needs to execute a measurement from the point of receiving the command until it responds.
t MEAS = 4⋅t INT + 770 μ s
e.g. t meas = 4⋅103 μ s + 770 μ s = 1'182μ s
Communication time
It is the period from the end of the measurement until the next start in a continuous mode manner (refer to Figure 12). It is the real communication time used by the 2-wire interface and all the additional time the microprocessor needs to send the next command to the chip.
Example:
Command write:
1 check bit + 1 start bit + 8 command bits
Read response:
2-wire serial clock SCKL:
1 check bit + 1 start bit + 16 data bits
1MHz
e.g. t com = 10⋅1 μ s + 18⋅1 μ s = 28μ s
Communication time tCOM
Data processing time
It is the period t PROCESS needed by the microprocessor for the final result: “calculation distance & quality” (refer to Figure 12)
Measurement cycle time
The measurement cycle time tCYCLE includes the duration to execute a complete measurement cycle until the next cycle propagation is possible (refer to Figure 12).
t CYCLE = tMEAS + t COM + t PROCESS
e.g. t CYCLE = 1'182 μ s + 28 μ s + 100μ s = 1'310μ s
Response time
The response time denotes the necessary time interval to change the distance output DIST of the microprocessor from one state to the
other (refer to Figure 11). The maximum response time t RESPONSE of the range-finder system is given by
t RESPONSE = 2⋅ tCYCLE
e.g.
t RESPONSE = 2⋅1'310 μ s = 2'620μ s
LED on-time and LED duty cycle
For the power dissipation estimation of the emitter LED (at pin LED), the LED on-time and the duty cycle are of importance. The following
time periods have to be taken into consideration:
■ tINT
■ tMEAS
■ tCOM
: during the integration period, the LED outputs are active for 50% of the time.
: there are 4 integration periods t INT per measurement cycle t MEAS.
: during the communication time the LED outputs are not active.
The formula for the LED on-time is:
t LED−ON = 4 ⋅
t INT
+ 15 μ s
2
The LED duty cycle DC LED-ON for LED on-time versus the cycle time is
t
DC LED−ON = LED−ON
t CYCLE
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Characteristics subject to change without notice
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e.g.
t LED−ON = 4 ⋅
e.g.
DCLED −ON =
103 μ s
+ 15μ s = 221μ s
2
221 μ s
= 17%
1'310 μ s
Datasheet epc600 - V1.3
www.espros.ch
4. Optical Design Considerations
This section summarizes some parameters that are of importance when designing the optical system of a TOF sensor.
Photosensitive area
The photosensitive area is the optical area which has to be well (full) covered by the receiver optics. This is the relevant surface for calcu lating the light sensitivity of the chip. It is also the relevant area for object detection without any gaps. For more details refer to chapter
1.3.4.: Quality of the measurement result.
Note:
Measurement values are reliable only if the object covers the entire photosensitive area. Measurement values are average values over the
sensor array's 64 pixels. Refer to the epc600 Handbook.
Signal sensitivity
The signal sensitivity is defined by the minimum and maximum detectable AC modulation signal (reflected light). It is defined by the light
power (Watt/m2) in relation to:
■ the photo-sensitive area of the sensor.
■ the operating integration time t INT .
■ the operating wavelength λ.
■ the angle of incidence (or reflectance of the sensor surface). Refer to Figure 3.
It is independent of
■ the modulation frequency
Ambient-light suppression
The ability to suppress DC or low-frequency modulation parts of the received light signal. It is defined by the light power (Watt/m 2) in relation to:
■ the photo-sensitive area of the sensor.
■ the operating integration time t INT.
■ the operating wavelength λ.
■ the angle of interest (or reflectance of the sensor surface). Refer to Figure 3.
Refer also to chapter 1.3.3.: Ambient-light suppression.
Operating range
The maximum non-ambiguity distance is < 15m for a modulation frequency of 10MHz @ the pin LED. It is given by the modulation fre quency and the speed of light.
The operating range (dynamic range) of the epc600 receiver for a certain illumination level is given by the photosensor and its electronics:
■ the AC signal sensitivity for the modulated light.
■ the capability of the ambient-light suppression.
■ the level of illumination.
Depending on the optical design, these ranges do not match. The optical engineer has to plan the optical design and the light power in a
way that matches the application best.
For more detailed information refer to epc's application note AN02 - Reflected power calculation.
© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
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Datasheet epc600 - V1.3
www.espros.ch
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© 2014 ESPROS Photonics Corporation
Characteristics subject to change without notice
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Datasheet epc600 - V1.3
www.espros.ch