ISL29027 Datasheet, PDF (7/13 Pages) Intersil Corporation – Proximity Sensor with Intelligent Interrupt and Sleep Modes

ISL29027
BIT #
7:0
ACCESS
RW
TABLE 6. REGISTER 0x04 (PROX_HT) - INTERRUPT HIGH THRESHOLD FOR PROXIMITY SENSOR
DEFAULT
BIT NAME
FUNCTION/OPERATION
0xFF
PROX_HT
8-bit interrupt high threshold for proximity sensing
(Prox Threshold)
BIT #
7:0
ACCESS
RO
TABLE 7. REGISTER 0x08 (PROX_DATA) - PROXIMITY SENSOR DATA
DEFAULT
BIT NAME
FUNCTION/OPERATION
0x00
PROX_DATA
(Proximity Data)
Results of 8-bit proximity sensor ADC conversion
BIT #
7:0
BIT #
7:0
ACCESS
RW
DEFAULT
0x00
ACCESS
RW
DEFAULT
0x00
TABLE 8. REGISTER 0x0E (TEST1) - TEST MODE
BIT NAME
FUNCTION/OPERATION
(Write as 0x00) Test mode register. When 0x00, in normal operation
TABLE 9. REGISTER 0x0F (TEST2) - TEST MODE 2
BIT NAME
FUNCTION/OPERATION
(Write as 0x00) Test mode register. When 0x00, in normal operation
I²C DATA ^START
DEVICE ADDRESS W A REGISTER ADDRESS
STOP START DEVICE ADDRESS
A
DATA BYTE0
I²C SDA
MASTER
I²C SDA
SLAVE (ISL29027)
A6 A5 A4 A3 A2 A1 A0 W A R7 R6 R5 R4 R3 R2 R1 R0 A
SDA DRIVEN BY MASTER A SDA DRIVEN BY MASTER A
A6 A5 A4 A3 A2 A1 A0 W A
SDA DRIVEN BY ISL29027
SDA DRIVEN BY MASTER
A D7 D6 D5 D4 D3 D2 D1 D0
I²C CLK
12 3456 789123456 789
123 45 67 89123456789
FIGURE 3. I²C DRIVER TIMING DIAGRAM FOR MASTER AND SLAVE CONNECTED TO COMMON BUS
Principles of Operation
I²C Interface
The ISL29027’s I²C interface slave address is internally hardwired
as 0b100010<x>, where “0b” signifies binary notation and x
represents the logic level on pin ADDR0.
Figure 3 shows a sample one-byte read. The I²C bus master
always drives the SCL (clock) line, while either the master or the
slave can drive the SDA (data) line. Every I²C transaction begins
with the master asserting a start condition (SDA falling while SCL
remains high). The first transmitted byte is initiated by the
master and includes 7 address bits and a R/W bit. The slave is
responsible for pulling SDA low during the ACK bit after every
transmitted byte.
Each I²C transaction ends with the master asserting a stop
condition (SDA rising while SCL remains high).
For more information about the I²C standard, please consult the
Philips™ I²C specification documents.
Photodiodes and ADCs
The ISL29027 contains photodiode arrays which convert photons
(light) into current. The proximity sensor is an 8-bit ADC. When
proximity sensing is enabled, the IRDR pin will drive a user-
supplied infrared LED, the emitted IR reflects off an object (i.e., a
human head) back into the ISL29027, and a sensor converts the
reflected IR wave to a current signal in 0.54ms. The ADC
subtracts the IR reading before and after the LED is driven (to
remove ambient IR such as sunlight), and converts this value to a
digital count stored in Register 0x8. Because of the conversion
times, the user must let the ADCs perform one full conversion
first before reading from I²C Registers PROX_DATA (wait
0.54ms). The proximity sensor runs continuously with a time
between conversions decided by PROX_SLP (Register 1 Bits
[6:4]).(as shown in Figure 4).
PROX
SENSOR
ACTIVE
IRDR
(CURRENT
DRIVER)
0.54ms FOR
PROX
CONVERSION
SERIES OF
CURRENT
PULSES
TOTALING 0.1ms
TIME
TIME
SLEEP TIME
(PROX_SLP)
FIGURE 4. CURRENT DRIVE MODE OPTIONS
Proximity Sensing
When proximity sensing is enabled (PROX_EN = 1), the external
IR LED is driven for 0.1ms by the built-in IR LED driver through
the IRDR pin. The amplitude of the IR LED current depends on
Register 1 bit 3: PROX_DR. If this bit is low, the load will see a
7
FN7815.0
February 7, 2011