Renesas ISL29021 Digital proximity sensor with interrupt function Datasheet

DATASHEET
ISL29021
FN6732
Rev 0.00
March 3, 2009
Digital Proximity Sensor with Interrupt Function
The ISL29021 is an integrated proximity and infrared sensor
with a built-in IR LED driver and I2C Interface (SMBus
Compatible). This device provides infrared sensing to allow
proximity estimation featured with interrupt function.
For infrared and proximity sensing, an internal ADC has
been designed based on the charge-balancing A/D
conversion technique.
The ADC is used to digitize the output signal from the
photodiode array when the internal IR LED driver is turned
on and off for the programmed time periods under
user-selected modulation frequency to drive the external IR
LED. As this proximity sensor employs a noise cancellation
scheme to highly reject unwanted IR noise, the digital output
of proximity sensing decreases with distance. The driver
output current is user selectable up to 100mA to drive
different types of IR emitters LEDs.
Four different modes of operation can be selected via the I2C
interface: programmable IR sensing once, programmable
proximity sensing once, programmable continuous IR sensing
and programmable continuous proximity sensing. The
programmable one-time operation modes greatly reduce power
because an immediate automatic shutdown reduces overall
supply current less than 0.5µA.
The ISL29021 supports both hardware and software
interrupts that remain asserted until the host clears it through
I2C interface for proximity detection.
Designed to operate on supplies from 2.5V to 3.63V, the
ISL29021 is specified for operation over the -40°C to +85°C
ambient temperature range. It is packaged in a clear, Pb-free
8 Ld ODFN package.
Ordering Information
PART NUMBER
(Note)
ISL29021IROZ-T7*
Proximity Sensing
• Ambient IR Cancellation During Proximity Sensing
- Works Under Direct Sunlight
• IR LED Driver with Programmable Source Current
- Adjustable Current Drive from 100mA to 12.5mA
• Programmable LED current Modulation Frequency
• Variable Conversion Resolution up to 16-bits
• Selectable Range (via I2C)
• Works Under Various Light Sources, Including Sunlight
Ideal Spectral Response for Proximity Sensor
• Proximity sensor range from 850nm to 950nm
- Can use either 850nm or 950nm LED solution
Ultra Low Power
• 90μA Max Operating Current
• Software Shutdown and Automatic Shutdown
- 0.5μA Max Shutdown Current
Easy to Use
• I2C (SMBus Compatible) Output
• No Complex Algorithms Needed
• Temperature Compensated
• Small Form Factor
- 8 Ld 2.0mmx2.1mmx0.7mm ODFN Package
Additional Features
• I2C and SMBus Compatible
• 1.7V to 3.63V Supply for I2C Interface
• 2.25V to 3.63V Sensor Power Supply
TEMP. RANGE
(°C)
PACKAGE
(Pb-Free)
PKG.
DWG. #
-40 to +85
8 Ld ODFN
L8.2.1x2.0
ISL29021IROZ-EVALZ Evaluation Board
*Please refer to TB347 for details on reel specifications.
NOTE: These Intersil Pb-free plastic packaged products employ
special Pb-free material sets; molding compounds/die attach
materials and NiPdAu plate - e4 termination finish, which is RoHS
compliant and compatible with both SnPb and Pb-free soldering
operations. Intersil Pb-free products are MSL classified at Pb-free
peak reflow temperatures that meet or exceed the Pb-free
requirements of IPC/JEDEC J STD-020.
FN6732 Rev 0.00
March 3, 2009
Features
• Pb-Free (RoHS compliant)
Applications
• Display and Keypad Proximity Sensing for:
- Mobile Devices: Smart Phone, PDA, GPS
- Computing Devices: Notebook PC, Webpad
- Consumer Devices: LCD-TV, Digital Picture Frame, Digital
Camera
• Industrial and Medical Proximity Sensing
Page 1 of 12
ISL29021
Pinout
ISL29021
(8 LD ODFN
TOP VIEW)
VDDD 1
8 IRDR
VDDA 2
7 INT
GND 3
6 SDA
REXT 4
5 SCL
EXPOSED PAD CAN BE CONNECTED TO GND OR
ELECTRICALLY ISOLATED
Pin Descriptions
PIN NUMBER PIN NAME
DESCRIPTION
1
VDDD
Positive digital supply: 2.5V to 3.63V.
2
VDDA
Positive analog supply: 2.5V to 3.63V, VDDA and VDDD should be externally shorted.
3
GND
Ground.
4
REXT
External resistor pin setting the internal reference current and the conversion time. 499k with 1% tolerance resistor
is recommended.
5
SCL
I2C serial clock line
6
SDA
I2C serial data line
7
INT
Interrupt pin; LO for interrupt/alarming. The INT pin is an open drain.
8
IRDR
The I2C bus lines can be pulled from 1.7V to above VDD, 3.63V max.
IR LED driver pin connecting to the anode of the external IR LED. The source current of the IR LED driver can be
programmed through I2C.
Exposed pad connected to ground or electrically isolated.
Block Diagram
VDDA
2
VDDD
1
COMMAND
REGISTER
IR DATA
PROCESS
INTEGRATION
ADC
DATA
REGISTER
6
SDA
5
SCL
INTERRUPT
7
INT
IR DRIVER
8
IRDR
I2C
IR PHOTODIODE
ARRAY
IREF
FOSC
4
3
REXT
GND
ISL29021
FN6732 Rev 0.00
March 3, 2009
Page 2 of 12
ISL29021
Absolute Maximum Ratings (TA = +25°C)
Thermal Information
VSUP(VDDD,VDDA) Supply Voltage between VDD and GND . . . . . .4V
VDDA Supply Voltage between VDDA and GND . . . . VDDD +/- 0.5V
I2C Bus (SCL, SDA) and INT Pin Voltage . . . . . . . . . . . . -0.2V to 4V
I2C Bus (SCL, SDA) and INT Pin Current . . . . . . . . . . . . . . . <10mA
IRDR Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . -0.2V to VDD + 0.5V
REXT Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . -0.2V to VDD + 0.5V
ESD Rating
Human Body Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kV
Thermal Resistance (Typical, Note 1)
JA (°C/W)
8 Ld ODFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
88
Maximum Die Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . +90°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +100°C
Operating Temperature . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C
Pb-Free Reflow Profile. . . . . . . . . . . . . . . . . . . . . . . . .see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and
result in failures not covered by warranty.
NOTE:
1. JA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See
Tech Brief TB379.
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests
are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
Electrical Specifications
PARAMETER
VSUP(VDDD,VDDA) = 3V, TA = +25°C, REXT = 499k1% tolerance, 16-bit ADC operation, unless otherwise
specified.
DESCRIPTION
CONDITION
MIN
VSUP
Power Supply Range for VDDD, VDDA
(Note 2)
ISUP(OFF)
Supply Current when Powered Down
Software disabled or auto power-down
ISUP(ON)
Supply Current of IR Sensing
VI2C
Supply Voltage Range for I2C Interface
1.7
fOSC
Internal Oscillator Frequency
675
tint
ADC Integration/Conversion Time
FI2C
I2C Clock Rate Range
DATA_IR0
Count Output When Dark
DATA_FS
Full Scale ADC Code
DATA_IR1
Infrared Count Output
E = 210 lux, Sunlight (Note 3), IR sensing, Range 1
DATA_IR2
Infrared Count Output
DATA_IR3
TYP
MAX
UNIT
3.63
V
0.1
0.5
µA
70
90
µA
3.63
V
825
kHz
2.25
16-bit ADC data
E = 0 lux
750
90
ms
1 to 400
kHz
1
6
Counts
65535 Counts
15000
20000
25000 Counts
E = 210 lux, Sunlight (Note 3), IR sensing, Range 2
5000
Counts
Infrared Count Output
E = 210 lux, Sunlight (Note 3), IR sensing, Range 3
1250
Counts
DATA_IR4
Infrared Count Output
E = 210 lux, Sunlight (Note 3), IR sensing, Range 4
312
Counts
VREF
Voltage of REXT Pin
0.52
V
VIL
SCL and SDA Input Low Voltage
VIH
SCL and SDA Input High Voltage
ISDA, IINT
SDA and INT Current Sinking Capability
IIRDR1
IRDR Source Current
IS<1:0> = 0 (Note 4)
IIRDR2
IRDR Source Current
IS<1:0> = 1 (Note 4)
IIRDR3
IRDR Source Current
IS<1:0> = 2 (Note 4)
IIRDR4
IRDR Source Current
IS<1:0> = 3 (Note 4)
VIRLED
Voltage Head Room of IRDR Pin
tr
Rise Time for IRDR Source Current
tf
0.55
V
1.25
4
15 at IRDR pin
44
V
5
mA
100
mA
50
58
mA
25
mA
12.5
mA
VDD - 0.6
V
RLOAD = 15 at IRDR pin, 20% to 80%
35
ns
Fall Time for IRDR Source Current
RLOAD = 15 at IRDR pin, 80% to 20%
10
ns
fIRLED1
IR LED Modulation Frequency
Freq = 0 (Note 4)
DC
kHz
fIRLED2
IR LED Modulation Frequency
Freq = 1 (Note 4)
360
kHz
FN6732 Rev 0.00
March 3, 2009
Page 3 of 12
ISL29021
Electrical Specifications
PARAMETER
VSUP(VDDD,VDDA) = 3V, TA = +25°C, REXT = 499k1% tolerance, 16-bit ADC operation, unless otherwise
specified. (Continued)
DESCRIPTION
CONDITION
MIN
TYP
MAX
UNIT
ISUP (IRLED1) Supply Current of Proximity Sensing
IS<1:0> = 0, Freq = 0 (Note 4)
101
mA
ISUP (IRLED2) Supply Current of Proximity Sensing
IS<1:0> = 0, Freq = 1 (Note 4)
51
mA
Duty Cycle
Duty Cycle of IR LED Modulation
50
%
PROX-IR
PROX
Differential ADC Output of IR and Proximity IR and proximity sensing with Range 2; 15 @ IRDR
Sensing With Object Far Away to Provide pin, IS<1:0> = 0, Freq = 0; E = 210 lux, Sunlight.
No Reflection
1.0
%
NOTES:
2. VSUP is the common voltage to VDDD and VDDA.
3. 850nm infrared LED is used in production test. The 850nm LED irradiance is calibrated to produce the same DATA_IR count against an illuminance
level of 210 lux sunlight at sea level.
4. See “Register Set” on page 6.
Principles of Operation
Photodiodes and ADC
The ISL29021 contains a photodiode array which converts
infrared energy into current. The spectral response for IR sensing
is shown in Figure 6 in the performance curves section. After IR
radiation is converted to current during the infrared signal
processing, the current output is converted to digital by a built-in
16-bit Analog-to-Digital Converter (ADC). An I2C command reads
the infrared light intensity in counts.
The converter is a charge-balancing integration type 16-bit ADC.
The chosen method for conversion is best for converting small
current signals in the presence of an AC periodic noise. A 100ms
integration time, for instance, highly rejects 50Hz and 60Hz power
line noise simultaneously. See “Integration and Conversion Time”
on page 7.
The built-in ADC offers user flexibility in integration time or
conversion time. Integration time is determined by an internal
oscillator (fOSC), and the n-bit (n = 4, 8, 12,16) counter inside the
ADC. A good balancing act of integration time and resolution
depending on the application is required for optimal results.
The ADC has I2C programmable range select to dynamically
accommodate various IR conditions. For very dim conditions,
the ADC can be configured at its lowest range (Range 1). For
very bright conditions, the ADC can be configured at its highest
range (Range 4) in the proximity sensing.
Low-Power Operation
The ISL29021 initial operation is at the power-down mode after
a supply voltage is provided. The data registers contain the
default value of 0. When the ISL29021 receives an I2C
command to do a one-time measurement from an I2C master, it
will start ADC conversion with proximity sensing. It will go to the
power-down mode automatically after one conversion is finished
and keep the conversion data available for the master to fetch
anytime afterwards. The ISL29021 will continuously do ADC
conversion with proximity sensing if it receives an I2C command
of continuous measurement. It will continuously update the data
FN6732 Rev 0.00
March 3, 2009
registers with the latest conversion data. It will go to the powerdown mode after it receives the I2C command of power-down.
Infrared and Proximity Sensing
There are four operational modes in ISL29021: programmable
IR sensing once with auto power-down, programmable proximity
sensing once with auto power-down, programmable continuous
IR sensing and programmable continuous proximity sensing.
These four modes can be programmed in series to fulfill the
application needs. The detailed program configuration is listed in
“Register Set” on page 6.
When the part is programmed for infrared (IR) sensing, the IR
light with wavelength within the “IR or Proximity Sensing”
spectral response curve on Figure 6 is converted into current.
With ADC, the current is converted to an unsigned n-bit (up to
16 bits) digital output.
When the part is programmed for proximity sensing, the
external IR LED is turned on by the built-in IR LED driver
through the IRDR pin. The amplitude of the IR LED current and
the IR LED modulation frequency can be programmed through
Command Register II. When the IR from the LED reaches an
object and gets reflected back, the reflected IR light with
wavelength within the “IR or Proximity Sensing” spectral
response curve in Figure 6 is converted into current. With
ADC, the current is converted to an unsigned n-bit (up to 16
bits) digital output. The output reading is inversely proportional
to the square of the distance between the sensor and the
object.
Interrupt Function
The active low interrupt pin is an open drain pull-down
configuration. There is also an interrupt bit in the I2C register.
The interrupt serves as an alarm or monitoring function to
determine whether the infrared light level or the proximity
detection level exceeds the upper threshold or goes below the
lower threshold. The user can also configure the persistency of
the interrupt. An unexpected camera flash, for example, can be
ignored by setting the persistency to 8 integration cycles.
Page 4 of 12
ISL29021
I2C Interface
Figure 1 shows a sample one-byte read. Figure 2 shows a
sample one-byte write. The I2C bus master always drives the
SCL (clock) line, while either the master or the slave can drive
the SDA (data) line. Figure 2 shows a sample write. Every I2C
transaction begins with the master asserting a start condition
(SDA falling while SCL remains high). The following byte is
driven by the master, and includes the slave address and
read/write bit. The receiving device is responsible for pulling
SDA low during the acknowledgement period. Every I2C
transaction ends with the master asserting a stop condition
(SDA rising while SCL remains high).
There are eight 8-bit registers available inside the ISL29021. The
two command registers define the operation of the device. The
command registers do not change until the registers are
overwritten. The two 8-bit data Read Only registers are for the
ADC output and the Timer output. The data registers contain the
ADC's latest digital output, or the number of clock cycles in the
previous integration period. The four 8-bit interrupt registers hold
16-bit interrupt high and low thresholds.
The ISL29021’s I2C interface slave address is internally hardwired as 1000100. When 1000100x with x as R or W is sent after
the Start condition, this device compares the first seven bits of this
byte to its address and matches.
I2C DATA
DEVICE ADDRESS
START
I2C SDA
IN
I2C SDA
OUT
I2C CLK
For more information about the I2C standard, please consult
the Philips™ I2C specification documents.
REGISTER ADDRESS
W A
A6 A5 A4 A3 A2 A1 A0 W A R7 R6 R5 R4 R3 R2 R1 R0 A
A
SDA DRIVEN BY MASTER
1
2
3
4
5
7
6
8
2
3
5
4
6
7
8
1
2
3
4
5
SDA DRIVEN BY ISL29021
A
SDA DRIVEN BY MASTER
9
DATA BYTE0
A
A6 A5 A4 A3 A2 A1 A0 W
A
SDA DRIVEN BY MASTER
1
9
DEVICE ADDRESS
STOP START
A D7 D6 D5 D4 D3 D2 D1 D0
6
7
9
8
1
2
4
3
5
6
7
8
9
FIGURE 1. I2C READ TIMING DIAGRAM SAMPLE
DEVICE ADDRESS
START
A
REGISTER ADDRESS
FUNCTIONS
W
A
W
A
R7 R6 R5 R4 R3 R2 R1 R0
A
B7 B6 B5 B4 B3 B2 B1 B0
A
SDA DRIVEN BY MASTER
A
SDA DRIVEN BY MASTER
STOP
A
I2C DATA
I2C SDA IN
A6 A5 A4 A3 A2 A1 A0
A
I2C SDA OUT
SDA DRIVEN BY MASTER
A
I2C CLK IN
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
FIGURE 2. I2C WRITE TIMING DIAGRAM SAMPLE
FN6732 Rev 0.00
March 3, 2009
Page 5 of 12
ISL29021
Register Set
There are eight registers that are available in the ISL29021. Table 1 summarizes their functions.
TABLE 1. REGISTER SET
BIT
ADDR
REG NAME
7
6
5
4
3
2
1
0
DEFAULT
00h
COMMANDI
OP2
OP1
OP0
0
0
FLAG
PRST1
PRST0
00h
01h
COMMANDII
1
FREQ
IS1
IS0
RES1
RES0
RANGE1
RANGE0
00h
02h
DATALSB
D7
D6
D5
D4
D3
D2
D1
D0
00h
03h
DATAMSB
D15
D14
D13
D12
D11
D10
D9
D8
00h
04h
INT_LT_LSB
TL7
TL6
TL5
TL4
TL3
TL2
TL1
TL0
00h
05h
INT_LT_MSB
TL15
TL14
TL13
TL12
TL11
TL10
TL9
TL8
00h
06h
INT_HT_LSB
TH7
TH6
TH5
TH4
TH3
TH2
TH1
TH0
FFh
07h
INT_HT_MSB
TH15
TH14
TH13
TH12
TH11
TH10
TH9
TH8
FFh
.
Command Register I 00(hex)
TABLE 4. INTERRUPT PERSIST
The first command register has the following functions:
BITS 1 TO 0
NUMBER OF INTEGRATION CYCLES
1. Operation Mode: Bits 7, 6, and 5.These three bits
determines the operation mode of the device.
00
1
01
4
TABLE 2. OPERATION MODE
BITS 7 TO 5
OPERATION
10
8
11
16
000
Power-down the device
Command Register II 01(hex)
001
Reserved (Do not use)
The second command register has the following functions:
010
IR once
011
Proximity once
100
Reserved (Do not use)
101
Reserved (Do not use)
110
IR continuous
111
Proximity continuous
1. Proximity Sensing Scheme: Bit 7. This bit programs the
function of the proximity detection. Logic 1 of this bit,
Scheme 1, makes n-1 (3, 7, 11, 15) bits (2’s
complementary) proximity_less_ambient detection. The
range of Scheme 1 proximity count is from -2(n-1) to 2(n-1),
Scheme 1 proximity detection is less affected by the
ambient IR noise variation.
TABLE 5. PROXIMITY SENSING SCHEME
2. Interrupt flag; Bit 2. This is the status bit of the interrupt. The
bit is set to logic high when the interrupt thresholds have
been triggered, and logic low when not yet triggered. Once
triggered, INT pin stays low and the status bit stays high.
Both interrupt pin and the status bit are automatically cleared
at the end of Command Register I transfer.
TABLE 3. INTERRUPT FLAG
BIT 2
BIT 7
0
Reserved
1
Sensing IR from LED with ambient IR rejection
2. Modulation Frequency: Bits 6. This bit sets the IR LED
driver’s modulation frequency.
TABLE 6. MODULATION FREQUENCY
OPERATION
0
Interrupt is cleared or not triggered yet
1
Interrupt is triggered
3. Interrupt persist; Bits 1 and 0. The interrupt pin and the
interrupt flag is triggered/set when the data sensor reading
is out of the interrupt threshold window after m consecutive
number of integration cycles. The interrupt persist bits
determine m.
FN6732 Rev 0.00
March 3, 2009
OPERATION
BITS 6
MODULATION FREQUENCY
(kHz)
0
DC
1
360
3. Amplitude of IR driver current: Bits 5 and 4. This device
provides current source to drive an external IR LED. The
drive capability can be programmed through Bits 5 and 4.
For example, the device sources 12.5mA out of the IRDR
pin if Bits 5 and 4 are 0.
Page 6 of 12
ISL29021
.
TABLE 7. CURRENT SOURCE CAPABILITY AT IRDR PIN
BITS 5 TO 4
IRDR PIN SOURCE CURRENT
Registers 06 and 07 hex set the high (HI) threshold for the
interrupt pin and the interrupt flag. 06 hex is the LSB and 07
hex is the MSB. By default, the Interrupt threshold HI is FF hex
for both LSB and MSB.
00
12.5mA IR LED driver
01
25mA IR LED driver
10
50mA IR LED driver
Integration and Conversion Time
11
100mA IR LED driver
The ADC resolution and fOSC determines the integration time,
tint.
4. Resolution: Bits 3 and 2. Bits 3 and 2 determine the ADC’s
resolution and the number of clock cycles per conversion in
Internal Timing Mode. Changing the number of clock cycles
does more than just change the resolution of the device. It
also changes the integration time, which is the period the
device’s analog-to-digital (A/D) converter samples the
photodiode current signal for a measurement.
.
R EXT
n
n
1
t int = 2  -------------- = 2  ---------------------------------------------725kHz  499k
f OSC
where n is the number of bits of resolution and n = 4, 8, 12 or
16. 2n, therefore, is the number of clock cycles. n can be
programmed at the command register 01(hex) bits 3 and 2.
TABLE 11. INTEGRATION TIME OF n-BIT ADC
TABLE 8. RESOLUTION/WIDTH
BITS 3 TO 2
NUMBER OF CLOCK CYCLES
n-BIT ADC
00
216 = 65,536
16
01
212 = 4,096
12
10
28 = 256
8
11
24 = 16
4
5. Range: Bits 1 and 0. The Full Scale Range (FSR) can be
adjusted via I2C using Bits 1 and 0. Table 9 lists the possible
values of FSR for the 499kREXT resistor.
TABLE 9. RANGE/FSR
BITS 1:0
k
RANGE(k)
FSR @ IR SENSING
00
1
Range1
Refer to page 3
01
2
Range2
Refer to page 3
10
3
Range3
Refer to page 3
11
4
Range4
Refer to page 3
Data Registers (02 hex and 03 hex)
The device has two 8-bit read-only registers to hold the data
from LSB to MSB for ADC. The most significant bit (MSB) is
accessed at 03 hex, and the least significant bit (LSB) is
accessed at 02 hex. For 16-bit resolution, the data is from D0
to D15; for 12-bit resolution, the data is from D0 to D11; for 8bit resolution, the data is from D0 to D7. The registers are
refreshed after every conversion cycle.
TABLE 10. DATA REGISTERS
ADDRESS
(hex)
CONTENTS
02
D0 is LSB for 4, 8, 12 or 16-bit resolution, D3 is MSB
for 4-bit resolution, D7 is MSB for 8-bit resolution
03
D15 is MSB for 16-bit resolution, D11 is MSB for
12-bit resolution
Interrupt Registers (04, 05, 06 and 07 hex)
Registers 04 and 05 hex set the low (LO) threshold for the
interrupt pin and the interrupt flag. 04 hex is the LSB and 05
hex is the MSB. By default, the Interrupt threshold LO is 00 hex
for both LSB and MSB.
FN6732 Rev 0.00
March 3, 2009
(EQ. 1)
REXT
(k
n = 16-BIT
n = 12-BIT
n = 8-BIT
n = 4-BIT
250
45ms
2.812ms
175.5µs
10.8µs
499**
90ms
5.63ms
351µs
21.6µs
**Recommended REXT resistor value
External Scaling Resistor REXT for fOSC and Range
The ISL29021 uses an external resistor REXT to fix its internal
oscillator frequency, fOSC. Range. fOSC and Range are
inversely proportional to REXT. For user simplicity, the
proportionality constant is referenced to 499k:
499k
Range = ------------------  Range  k 
R EXT
(EQ. 2)
499k
f OSC = ------------------  725 kHz
R EXT
(EQ. 3)
Noise Rejection
In general, integrating type ADC’s have excellent
noise-rejection characteristics for periodic noise sources
whose frequency is an integer multiple of the conversion rate.
For instance, a 60Hz AC unwanted signal’s sum from 0ms to
k*16.66ms (k = 1,2...ki) is zero. Similarly, setting the device’s
integration time to be an integer multiple of the periodic noise
signal, greatly improves the proximity sensor output signal in
the presence of noise.
ADC Output in IR Sensing
The ISL29021’s ADC output codes, DATA, are directly
proportional to the IR intensity received in the IR sensing.
DATA IR =   E IR
(EQ. 4)
Here, EIR is the received IR intensity. The constant  changes
with the spectrum of background IR noise like sunlight and
incandescent light. The also changes with the ADC’s range
and resolution selections.
ADC Output in Proximity Sensing
In the proximity sensing, the ADC output codes, DATA, are
directly proportional to the total IR intensity from the
Page 7 of 12
ISL29021
background IR noise and from the IR LED driven by the
ISL29021 as shown in Equation 5.
DATA PROX =   E IR +   E LED
(EQ. 5)
Here, andEIR have the same meanings as in Equation 4.
The constant  depends on the spectrum of the used IR LED
and the ADC’s range and resolution selections. ELED is the IR
intensity which is emitted from the IR LED and reflected by a
specific objector to the ISL29021. ELED depends on the
current to the IR LED and the surface of the object. ELED
decreases with the square of the distance between the object
and the sensor.
If background IR noise is small, EIR can be neglected, and the
ADC output directly decreases with the distance. If there is
significant background IR noise, ISL29021 is to do a proximity
sensing using Scheme 1 to do on-chip background IR noise
subtraction.
Figure 9 shows ISL29021 configured at 12-bit ADC resolution
and sensitivity range select at 16000 (range 3) for the proximity
reading. A 12.5mA external LED current at 360kHz modulation
frequency detects three different sensing objects: 92%
brightness paper, 18% gray card and ESD black foam. Figure
10 shows ISL29021 configured at 12-bit ADC resolution and
sensitivity range select at 1000 (range 1) for the proximity
reading, with a programmed external LED at 360kHz
modulation frequency, detecting the same sensing object: 18%
gray card under four different external LED current: 12.5mA,
25mA, 50mA and 100mA to compare the proximity readout
versus distance.
ISL29021 Proximity sensing relies on the amount of IR reflected
back from the objects to be detected. Clearly, it can not detect
an optically black object that reflects no light. However,
ISL29021 is sensitive enough to detect a black ESD foam, which
reflects slightly less than 1% of IR, as shown in Figure 9. For
biological objects, blonde hair reflects more than brunette hair,
as expected and shown in Figure 11. Also notice that skin tissue
is much more reflective than hair. IR penetrates into the skin and
is reflected or scattered back from within. As a result, the
proximity count peaks at contact and monotonically decreases
as skin moves away. This characteristic is very different from
that of a plain paper reflector.
of register 01h. At the IRDR pin, there are four different IRDR
LED currents; 12.5, 25, 50, and 100mA outputs selectable by
bits 4 and 5 of register 01h. With the LED running in the DC
mode, the proximity detection is twice as sensitive but
consumes 2x more current. The sensitivity of LED 50mA, DC
50mA is identical to that of 100mA, 360kHz modulation. Please
note that the ISL29021 does not include a LED.
Current Consumption Estimation
The low power operation is achieved through sequential
readout in the serial fashion, as shown in Figure 3, the device
requires three different phases in serial during the entire
detection cycle to do infrared sensing and proximity sensing.
The external IR LED will only be turned on during the proximity
sensing phase under user program controlled current at
modulated frequency depends on user selections. Figure 3
also shows the current consumption during each IR sensing
and Proximity sensing phase. For example, at 8-bit ADC
resolution the integration time is 0.4ms. If user programed
50mA current to supply external IR LED at 360kHz modulated
frequency, during the entire operation cycle that includes IR
sensing and Proximity sensing three different serial phases,
the detection occurs once every 30ms, the average current
consumption including external IR LED drive current can be
calculated from Equation 6:
  0.05mA + 0.05mA + 1mA + (50mA 50%)) 0.4ms  /30ms = 0.35mA
(EQ. 6)
If at a 12-bit ADC resolution where the integration time for each
serial phase becomes 7ms and the total detection time
becomes 100ms, the average current can be calculated from
Equation 7:
  0.05mA + 0.05mA + 1mA + (50mA 50%)) 7 ms  /100ms = 1.83mA
(EQ. 7)
Suggested PCB Footprint
It is important that the users check the “Surface Mount
Assembly Guidelines for Optical Dual FlatPack No Lead
(ODFN) Package” before starting ODFN product board
mounting.
http://www.intersil.com/data/tb/TB477.pdf
Layout Considerations
Interrupt Function
Depending on the mode of operation set by Bits 7, 6 and 5 of
command register 00 hex, the upper and lower interrupt
thresholds are for either infrared signal level or proximity
detection. After each change of mode of operation, it is
expected a new set of thresholds are loaded to interrupt
registers 04, 05, 06 and 07 hex for proper interrupt detection.
Also, the interrupt persist counter will be reset to 0 when the
mode of operation is changed.
LED Modulation for Proximity Detection
ISL29021 offers two ways to modulate the LED in the Proximity
Detection mode - DC or 360kHz (with 50% duty cycle) by bit 6
FN6732 Rev 0.00
March 3, 2009
The ISL29021 is relatively insensitive to layout. Like other I2C
devices, it is intended to provide excellent performance even in
significantly noisy environments. There are only a few
considerations that will ensure best performance.
Route the supply and I2C traces as far as possible from all
sources of noise. Use two power-supply decoupling capacitors
1µF and 0.1µF, placed close to the device.
Typical Circuit
A typical application for the ISL29021 is shown in Figure 4. The
ISL29021’s I2C address is internally hardwired as 1000100.
Page 8 of 12
ISL29021
The device can be tied onto a system’s I2C bus together with
other I2C compliant devices.
Soldering Considerations
package does not require a custom reflow soldering profile,
and is qualified to +260°C. A standard reflow soldering profile
with a +260°C maximum is recommended.
Convection heating is recommended for reflow soldering;
direct-infrared heating is not recommended. The plastic ODFN
30ms
1µ
IR
50µ
0.4ms
PROXIMITY
0.4ms
1mA
IR LED
50mA
360 kHz
FIGURE 3. CURRENT CONSUMPTION FOR EACH INTEGRATION PHASE AND DETECTION CYCLE
1.7V TO 3.63V
R1
10k
R2
10k
I2C MASTER
R3
10k
MICROCONTROLLER
INT
SDA
SCL
2.25V TO 3.63V
SLAVE_0
1
2
3
4
REXT
499k
C1
1µ
VDDD
IRDR
VDDA
INT
GND
SDA
REXT
SCL
SLAVE_1
8
7
I2C SLAVE_n
SDA
SDA
SCL
SCL
6
5
ISL29021
C2
0.1µ
FIGURE 4. ISL29021 TYPICAL CIRCUIT
FN6732 Rev 0.00
March 3, 2009
Page 9 of 12
ISL29021
Typical Performance Curves
VSUP (VDDD, VDDA) = 3V, REXT = 499k
1.2
1.2
INCANDESCENT
1.0
0.8
HALOGEN
0.6
FLUORESCENT
0.4
0.2
0
300
400
500
600
700
800
WAVELENGTH (nm)
900
1000
1.0
NORMALIZED RESPONSE
NORMALIZED LIGHT INTENSITY
SUN
1100
0.6
0.4
0.2
0
-0.2
300
0¬
10¬
20¬
40¬
50¬
50¬
60¬
60¬
70¬
70¬
80¬
0.2 0.4
0.6 0.8
RELATIVE SENSITIVITY
1100
18% GRAY CARD
10
1
ESD BLACK FOAM
0
20
40
60
DISTANCE (mm)
80
100
FIGURE 8. ADC OUTPUT vs DISTANCE WITH DIFFERENT
OBJECTS IN PROXIMITY SENSING
350
4500
3500
IIRLED = 100mA
3000
IIRLED = 50mA
DATAPROX - DATAIR (COUNT)
4000
DATAPROX-DATAIR (COUNT)
1000
100
90¬
1.0
FIGURE 7. RADIATION PATTERN
IIRLED = 25mA
2500
IIRLED = 12.5mA
2000
1500
1000
500
0
0
900
1000
80¬
90¬
600
700
800
WAVELENGTH (nm)
92% BRIGHTNESS PAPER
30¬
DATAPROX-DATAIR
10¬
500
10000
RADIATION PATTERN
20¬
400
FIGURE 6. SPECTRAL RESPONSE FOR PROXIMITY
SENSING
FIGURE 5. SPECTRUM OF FOUR LIGHT SOURCES
LUMINOSITY
30¬
ANGLE 40¬
IR AND
PROXIMITY
SENSING
0.8
10
20
30
40
50
60
70
80
90
DISTANCE (mm)
FIGURE 9. ADC OUTPUT vs DISTANCE WITH DIFFERENT
LED CURRENT AMPLITUDES IN PROXIMITY
SENSING
FN6732 Rev 0.00
March 3, 2009
300
PIG'S SKIN
250
200
150
18% GRAY
130 CTS = 500 CTS x 65% x 65%
= 211 CTS
100
BLOND HAIR
50
0
12-BIT ADC
RANGE 3
fLED = 328kHz
ILED = 12.5mA
4mm CENTER-TO-CENTER
FOR ISL29021 AND SFH4650,
ISOLATED BY BARRIER
AND BEHIND A 65%
IR TRANSMITTING GLASS
0
10
BRUNETTE HAIR
20
30
40
DISTANCE (mm)
50
60
FIGURE 10. PROXIMITY DETECTIONS OF VARIOUS
BIOLOGICAL OBJECTS
Page 10 of 12
ISL29021
Typical Performance Curves
VSUP (VDDD, VDDA) = 3V, REXT = 499k (Continued)
105.0
IRDR OUTPUT CURRENT (mA)
104.5
PROXIMITY SENSING
IS<1:0> = 0
104.0
103.5
103.0
102.5
102.0
101.5
101.0
100.5
100.0
-40
-20
0
20
40
60
TEMPERATURE (¬×C
80
100
120
FIGURE 11. OUTPUT CURRENT vs TEMPERATURE IN PROXIMITY SENSING
2.00
SENSOR OFFSET
2.10
1
8
2
7
3
6
4
5
0.40
0.54
0.37
FIGURE 12. 8 LD ODFN SENSOR LOCATION OUTLINE
© Copyright Intersil Americas LLC 2009. All Rights Reserved.
All trademarks and registered trademarks are the property of their respective owners.
For additional products, see www.intersil.com/en/products.html
Intersil products are manufactured, assembled and tested utilizing ISO9001 quality systems as noted
in the quality certifications found at www.intersil.com/en/support/qualandreliability.html
Intersil products are sold by description only. Intersil may modify the circuit design and/or specifications of products at any time without notice, provided that such
modification does not, in Intersil's sole judgment, affect the form, fit or function of the product. Accordingly, the reader is cautioned to verify that datasheets are
current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its
subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
FN6732 Rev 0.00
March 3, 2009
Page 11 of 12
ISL29021
Package Outline Drawing
L8.2.1x2.0
8 LEAD OPTICAL DUAL FLAT NO-LEAD PLASTIC PACKAGE (ODFN)
Rev 0, 10/08
2.10
6
A
PIN #1
INDEX AREA
B
6
PIN 1
INDEX AREA
0.50
2.00
1.50
1.50
0.20±0.0
(2X)
0.10 M C A B
0.10
8X 0 . 35 ± 0 . 0
TOP VIEW
0.75
BOTTOM VIEW
SEE DETAIL "X"
0.10 C
0.70±0.0
C
BASE PLANE
SEATING PLANE
0.08 C
SIDE VIEW
(6x0.50)
(1.50)
(8x0.20)
C
0 . 2 REF
5
(8x0.55)
(0.75)
0 . 00 MIN.
0 . 05 MAX.
TYPICAL RECOMMENDED LAND PATTERN
DETAIL "X"
NOTES:
1. Dimensions are in millimeters.
Dimensions in ( ) for Reference Only.
2. Dimensioning and tolerancing conform to AMSE Y14.5m-1994.
3. Unless otherwise specified, tolerance : Decimal ± 0.0
4. Dimension b applies to the metallized terminal and is measured
between 0.25mm and 0.35mm from the terminal tip.
5. Tiebar shown (if present) is a non-functional feature.
6. The configuration of the pin #1 identifier is optional, but must be
located within the zone indicated. The pin #1 indentifier may be
either a mold or mark feature.
FN6732 Rev 0.00
March 3, 2009
Page 12 of 12