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_______________________________________________________________ maxim integrated products 1 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxims website at www.maxim-ic.com. industrys lowest-power ambient light sensor with adc max9635 19-5284; rev 1; 2/11 general description the max9635 ambient light sensor features an i 2 c digi - tal output that is ideal for a number of portable applica - tions such as smartphones, notebooks, and industrial sensors. at less than 1a operating current, it is the lowest power ambient light sensor in the industry and features an ultra-wide 22-bit dynamic range from 0.045 lux to 188,000 lux. low-light operation allows easy operation in dark glass applications. the on-chip photodiodes spectral response is optimized to mimic the human eyes perception of ambient light and incorporates ir and uv blocking capability. the adaptive gain block automatically selects the correct lux range to optimize the counts/lux. the ic is designed to operate from a 1.7v to 3.6v sup - ply voltage range and consumes only 0.65a in full operation. it is available in a small, 2mm x 2mm x 0.6mm otdfn package. applications tablet pcs/notebook computers tvs/projectors/displays digital lighting management portable devices cellular phones/smartphones security systems features s wide 0.045 lux to 188,000 lux range s small, 2mm x 2mm x 0.6mm otdfn s v cc = 1.7v to 3.6v s i cc = 0.65a operating current s -40 n c to +85n c temperature range ordering information + denotes a lead(pb)-free/rohs-compliant package. * ep = exposed pad. block diagram evaluation kit available part pin-package temp range max9635edt+ 6 otdfn-ep* -40n c to +85nc digital signal processing 6-bit range cdr, tim control visible +ir photodiode ir photodiode i 2 c v cc max9635 n gnd ao scl sda int 16-bit adc 16-bit adc
industrys lowest-power ambient light sensor with adc max9635 2 stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. int to gnd ............................................... -0.3v to (v cc + 0.3v) all other pins to gnd ............................................. -0.3v to +4v int short-circuit current duration ........................................ 10s all other pins short-circuit current duration ............ continuous continuous input current into any terminal ................... q20ma continuous power dissipation 6 otdfn (derate 11.9mw/ n c above +70nc) .............. 953mw operating temperature range .......................... -40n c to +85nc electrical characteristics (v cc = 1.8v, t min to t max = -40 n c to +85n c, unless otherwise noted.) (note 1) absolute maximum ratings parameter symbol conditions min typ max units optical characteristics maximum lux sensitivity fluorescent light 0.045 lux/lsb saturation ambient lux level sunlight 188,000 lux total error te green led 538nm response, t a = +25 n c (note 2) 15 % light source matching fluorescent/incandescent light 10 % infrared transmittance at 940nm irr t a = +25 n c (note 3) 0 0.5 % ultraviolet transmittance at 363nm uvr t a = +25 n c (note 3) 1.2 % dark level count 0lux 0 lux, t a = +25 n c, 800ms range 0 0.045 lux maximum signal integration time has 50/60hz rejection 800 ms minimum signal integration time automatic mode, has 50/60hz rejection 100 ms manual mode only 6.25 adc conversion time act 100ms range, t a = +25 nc 99.6 100 100.4 ms 100ms range 97 103 107 power supply power-supply voltage v cc guaranteed by te test 1.7 3.6 v power-supply current i cc t a = +25 n c, 90 lux, i 2 c inputs inactive 0.65 1.2 fa t a = -40 n c to +85nc 1.6 digital i/o characteristics output low voltage sda, int v ol i sink = 6ma 0.06 0.4 v int leakage current t a = +25 nc 0.01 20 na scl, sda, a0 input current i ih , i il t a = +25 nc 0.01 20 na i 2 c input low voltage v il_i2c sda, scl 0.3 x v cc v i 2 c input high voltage v ih_i2c sda, scl 0.7 x v cc v address input low voltage v il_a0 a0 0.3 v address input high voltage v ih_a0 a0 v cc - 0.3v v input capacitance 3 pf
industrys lowest-power ambient light sensor with adc max9635 3 electrical characteristics (continued) (v cc = 1.8v, t min to t max = -40 n c to +85n c, unless otherwise noted.) (note 1) note 1: all devices are 100% production tested at t a = +25 n c. temperature limits are guaranteed by design. note 2: green 538nm led chosen for production is such that the ic responds to 100 lux fluorescent light with 100 lux. note 3: with respect to green led 538nm response. note 4: a master device must provide a hold time of at least 300ns for the sda signal (referred to v il of the scl signal) to bridge the undefined region of scls falling edge. parameter symbol conditions min typ max units i 2 c timing serial-clock frequency f scl 400 khz bus free time between a stop and a start condition t buf 1.3 fs hold time (repeated) start condition t hd,sta 0.6 fs low period of the scl clock t low 1.3 fs high period of the scl clock t high 0.6 fs setup time for a repeated start condition t su,sta 0.6 fs data hold time t hd,dat (note 4) 0 0.9 fs data setup time t su,dat 100 ns fall time of sda transmitting t f i sink p 6ma, t r and t f are measured between 0.3 x v dd and 0.7 x v dd 100 ns setup time for stop condition t su,sto 0.6 fs pulse width of spike suppressed t sp input filters on the sda and scl inputs suppress noise spikes 0 50 ns
industrys lowest-power ambient light sensor with adc max9635 4 typical operating characteristics (v cc = 1.8v, default power upsetting; unless otherwise noted.) spectrum response max9635 toc01 wavelength (nm) cie normalized response 900 800 700 600 500 400 20 40 60 80 100 120 0 300 1000 max9635 response radiation pattern max9635 toc02 luminosity angle () relative sensitivity (% from 0) 60 30 0 -30 -60 10 20 30 40 50 60 70 80 90 100 0 -90 90 auto mode, incandescent lamp spectrum of light sources for measurement max9635 toc03 wavelength (nm) normalized response 900 800 400 500 600 700 20 40 60 80 100 120 140 160 0 300 1000 incandescent sunlight fluorescent supply current vs. supply voltage max9635 toc04 supply voltage (v) supply current (a) 3.3 3.0 2.7 2.4 2.1 1.8 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0 1.5 3.6 0 lux and 100 lux, cont = 1 5000 lux, cont = 0 100 lux, cont = 0 auto mode, fluorescent lamp output code error vs. supply voltage max9635 toc05 supply voltage (v) output code error (ratio from 1.8v) 3.3 3.0 2.4 2.7 2.1 1.8 0.92 0.94 0.96 0.98 1.00 1.02 1.04 1.06 1.08 1.10 0.90 1.5 3.6 50 and 300 lux auto mode, fluorescent lamp supply current vs. temperature max9635 toc06 temperature (c) supply current (a) 60 35 10 -15 0.2 0.4 0.6 0.8 1.0 1.2 0 -40 85 100 lux auto mode, fluorescent lamp v cc = 1.8v v cc = 2.5v v cc = 3.3v
industrys lowest-power ambient light sensor with adc max9635 5 typical operating characteristics (continued) (v cc = 1.8v, default power upsetting; unless otherwise noted.) pin configuration pin description supply current vs. lux reading max9635 toc07 lux reading (lux) supply current (a) 10k 1k 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 100 100k sunlight light sensitivity vs. lux level max9635 toc08 reference meter reading (lux) max9635 reading (lux) 250 200 150 100 50 50 100 150 200 250 300 350 0 0 300 fluorescent lamp incandescent lamp sda, int output low voltage vs. sink current max9635 toc09 i sink (ma) v ol (mv) 9 8 6 7 2 3 4 5 1 10 20 30 40 50 60 70 80 90 100 110 120 0 0 10 int sda 1 6 v cc sda 2 5 + gnd scl 3 ep 4 a0 int otdfn (2mm x 2mm) top view max9635 pin name function 1 v cc power supply 2 gnd ground 3 a0 address select. pull high to select address 0x96 or low to select address 0x94. 4 int interrupt output. use an external pullup resistor. 5 scl i 2 c clock bus 6 sda i 2 c data bus ep exposed pad. connect ep to ground.
industrys lowest-power ambient light sensor with adc max9635 6 detailed description the max9635 is an ambient light sensor with integrated photodiode and adc with an i 2 c digital interface. to measure ambient light, the die is placed inside an optically transparent (otdfn) package. a photodi - ode inside the ic converts the light to a current that is then processed by low-power circuitry into a digital bit stream. this is digitally processed and stored in an out - put register that is read by an i 2 c interface. an on-chip programmable interrupt function eliminates the need for continually polling the device for data and results in sig - nificant power saving. a package-level optical filter prevents ultraviolet and infrared from reaching the photodiode. its opti - cal response is also designed to match the spectral response of the human eye. a second photodiode array, sensitive primarily to the infrared spectrum, is then used to match flourescent and incandescent light response from the part. two key features of the ic analog design are its ultra-low current consumption (typically 0.65a) and an extremely wide dynamic light range that extends from 0.045 lux to 188,000 luxmore than a 4,000,000 to 1 range. the on- chip autoranging scheme requires no user intervention for the gain-range setting. the ic can be customized to operate at enhanced sen - sitivity in applications where it needs to operate behind a dark glass. the default integration time of the adc is 100ms, giving it inherent rejection of 50hz and 60hz ripple common in certain line-powered light sources. human eye cie curve and different light sources the ic is designed to detect brightness in the same way as human eyes do. to achieve this, the sensor needs to have a spectral sensitivity that is similar to that of human eyes. figure 1 shows the spectral sensitivity of the ic and the human eye (cie curve). as can be seen, the human eye has its peak sensitivity at 555nm (green), while that of blue (~470nm) and red (~630nm) is much lower. the human eye also is blind to infrared (> 700nm) and ultraviolet (< 400nm) radiation. light sources can have similar visible brightness (lux), but different ir radiation content (because the human eye is blind to it). the differences in the light spectra affect bright - ness measurement because some of this infrared radiation is picked up by silicon photodiodes. for example, light sources with high ir content, such as an incandescent bulb or sunlight, would suggest a much brighter environ - ment than our eyes would perceive them to be. other light sources, such as fluorescent and led-based systems, have very little infrared content. the ic exhibits good ir rejection and internal ir compensation scheme to minimize these effects and give an accurate lux response. figure 1. spectral sensitivity of the max9635 and human eye wavelength (nm) cie normalized response 900 800 700 600 500 400 20 40 60 80 100 120 0 300 1000 max9635 response
industrys lowest-power ambient light sensor with adc max9635 7 table 1. register map table 2. interrupt status register if the inte bit is set to 1, then the ints status bit is asserted if the light intensity exceeds either upper or lower threshold limits (as specified by registers 0x05 and 0x06, respectively) for a period longer than that defined by the threshold timer register (0x07). this bit resets to 0 after the host reads this register. see table 2. this bit is also reflected on the int pin. when the ints bit is set, the int pin is asserted low, and when the ints bit is set to 0, the int pin is pulled high by an external resistor. once this bit is set, it can be cleared either by reading the interrupt status register 0x00 or by writing a 0 to the interrupt enable register 0x01. interrupt status 0x00 interrupt enable 0x01 register and bit descriptions bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 register address ints 0x01 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 register address ints 0x01 bit 0 operation 0 no interrupt trigger event has occurred. 1 ambient light intensity is outside the threshold window range for a longer than specified time. register bit register address power-on reset state r/w 7 6 5 4 3 2 1 0 status interrupt status ints 0x00 0x00 r interrupt enable inte 0x01 0x00 r/w configuration configuration cont manual cdr tim[2:0] 0x02 0x03 r/w lux reading lux high byte e3 e2 e1 e0 m7 m6 m5 m4 0x03 0x00 r lux low byte m3 m2 m1 m0 0x04 0x00 r threshold set upper threshold high byte ue3 ue2 ue1 ue0 um7 um6 um5 um4 0x05 0xff r/w lower threshold high byte le3 le2 le1 le0 lm7 lm6 lm5 lm4 0x06 0x00 r/w threshold timer t7 t6 t5 t4 t3 t2 t1 t0 0x07 0xff r/w
industrys lowest-power ambient light sensor with adc max9635 8 current division ratio (cdr) the cdr bit controls the current division ratio. the photodiode current is divided as shown in table 6. manual configuration mode in automatic mode (manual = 0), reading the contents of tim[2:0] and cdr bits reflects the automatically generated values from an internal timing register and are read-only. in manual mode (manual = 1), the contents of tim[2:0] and cdr bits can be modified by the users through the i 2 c bus. continuous mode configuration 0x02 interrupt events set the ints bit (register 0x00, bit 0) and the int pin only if the inte bit is set to 1. if the inte bit is set (interrupt is enabled) and the interrupt condition is triggered, then the int pin is pulled low (asserted) and the ints bit in the interrupt status register is set to 1. see table 3. table 3. interrupt enable register table 4. continuous mode register table 5. manual configuration register table 6. current division ratio register note: continuous mode is independent of the manual configuration mode setting. bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 register address cont manual cdr tim[2:0] 0x02 bit 0 operation 0 the int pin and the ints bit are not asserted even if an interrupt event has occurred. 1 detection of an interrupt event triggers a hardware interrupt ( int pin is pulled low) and sets the ints bit (register 0x00, bit 0). bit 7 operation 0 default mode. the ic measures lux intensity only once every 800ms regardless of integration time. this mode allows the part to operate at its lowest possible supply current. 1 continuous mode. the ic continuously measures lux intensity. that is, as soon as one reading is finished, a new one begins. if integration time is 6.25ms, readings are taken every 6.25ms. if integration time is 800ms, readings are taken every 800ms. in this mode, the part consumes slightly higher power than in the default mode. bit 6 operation 0 default mode of configuration is used for the ic. in this mode, cdr and tim[2:0] bits are automatically deter - mined by the internal autoranging circuitry of the ic. 1 manual mode of configuration is used for the ic. in this mode, cdr and tim[2:0] bits can be programmed by the user. bit 3 operation 0 current not divided. all of the photodiode current goes to the adc. 1 current divided by 8. only 1/8 of the photodiode current goes to the adc. this mode is used in high-brightness situations.
industrys lowest-power ambient light sensor with adc max9635 9 bits in lux high-byte register 0x03 give the 4 bits of exponent e3:e0 and 4 most significant bits of the mantissa byte m7:m4, and represent the lux reading of ambient light. the remaining 4 bits of the mantissa byte m3:m0 are in the lux low-byte register 0x04 and enhance resolution of the lux reading from the ic. exponent (e[3:0]): exponent bits of the lux reading (0000 to 1110). note: a reading of 1111 represents an overrange condition. mantissa (m[7:4]): four most significant bits of mantissa byte of the lux reading (0000 to 1111). lux = 2 (exponent) x mantissa x 0.72 exponent = 8xe3 + 4xe2 + 2xe1 + e0 mantissa = 8xm7 + 4xm6 + 2xm5 + m4 a code of 0000 0001 calculates to be 0.72 lux. a code of 1110 1111 calculates to be 176,947 lux. a code of 1110 1110 calculates to be 165,151 lux. update of the contents of this register is internally disabled during i 2 c read operations to ensure proper data transfer between internal adc and i 2 c registers. update of i 2 c registers is resumed when the master sends a stop command. if user wants to read both the lux high-byte register 0x03 and lux low-byte register 0x04, then the master should not send a stop command between the reads of the two registers. instead a repeated start command should be used. this ensures accurate data is obtained from the i 2 c registers (by disabling internal updates during the read process). integration timer bits (tim[2:0]) the tim[2:0] bits can be used to program the signal integration time. in automatic mode (manual = 0), integration time is automatically selected by the on-chip algorithm to be either 100ms/200ms/400ms/800ms. in manual mode (manual = 1), integration time can be varied by the user all the way from 6.25ms to 800ms. see table 7. lux high-byte register 0x03 table 7. integration time tim[2:0] integration time (ms) comments 000 800 this is a preferred mode for boosting low-light sensitivity. 001 400 010 200 011 100 this is a preferred mode for high-brightness applications. 100 50 manual mode only. 101 25 manual mode only. 110 12.5 manual mode only. 111 6.25 manual mode only. bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 register address e3 e2 e1 e0 m7 m6 m5 m4 0x03
industrys lowest-power ambient light sensor with adc max9635 10 the upper threshold register exponent with the four most significant bits of the mantissa sets the upper trip level for interrupt functionality. this upper limit is relevant only if the inte bit in the interrupt enable register is set. if the lux level is greater than this light level for a time greater than that specified in the threshold timer register, the ints bit in the interrupt status register is set and the int pin is pulled low. mantissa (um[7:4]): four most significant bits of mantissa upper threshold exponent (ue[3:0]): exponent bits upper threshold upper lux threshold = 2 (exponent) x mantissa x 0.045 exponent = 8xue3 + 4xue2 + 2xue1 + ue0 mantissa = 128xum7 + 64xum6 + 32xum5 + 16xum4 + 15 upper threshold high-byte register 0x05 bits in lux low-byte register 0x04 give the 4 least significant bits of the mantissa byte representing the lux reading of ambient light. combined with the lux high-byte register 0x03, it extends the resolution and dynamic range of lux measurements of the ic. e3Ce0: exponent bits of lux reading m7Cm0: mantissa byte of lux reading lux = 2 (exponent) x mantissa x 0.045 exponent = 8xe3 + 4xe2 + 2xe1 + e0 mantissa = 128xm7 + 64xm6 + 32xm5 + 16xm4 + 8xm3 + 4xm2 + 2xm1 + m0 combining contents of register 0x03 and 0x04: a code of 0000 0000 0001 calculates to be 0.045 lux. a code of 0000 0001 0000 calculates to be 0.72 lux. a code of 0001 0001 0001 calculates to be 0.765 lux. a code of 1110 1111 1111 calculates to be 188,006 lux. a code of 1110 1111 1110 calculates to be 187, 269 lux. the lux high-byte 0x03 and lux low-byte 0x04 register updates are internally disabled at the start of a valid address transmission from the master. updating reinitiates at the next valid stop condition. this prevents erroneous readings, in the event an update occurs between readings of registers 0x03 and 0x04. update of the contents of this register is internally disabled during i 2 c read operations to ensure proper data transfer between internal adc and i 2 c registers. update of i 2 c registers is resumed when the master sends a stop command. if the user wants to read both the lux high-byte register 0x03 and lux low-byte register 0x04, then the master should not send a stop command between the reads of the two registers. instead a reapeated start command should be used. this ensures accurate data is obtained from the i 2 c registers (by disabling internal updates during the read process). lux low-byte register 0x04 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 register address ue3 ue2 ue1 ue0 um7 um6 um5 um4 0x05 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 register address m3 m2 m1 m0 0x04
industrys lowest-power ambient light sensor with adc max9635 11 applications information auto and manual modes in auto mode configuration (default setting), cdr and tim bits are internally generated. the autoranging circuit uses two different methods to change its sensitivity. for light intensities greater than 700 lux, a current divider reduces the photodiodes current by a factor of 8. the default, as in the previous example, is a division of 1: current goes directly into the i to f converter. as light intensity decreases, the autoranging circuit increases the integration time from 100ms to 200ms to 400ms, or to 800ms. the combination of the current divider and the different integration times give the a/d a range 8 times higher, as well as 8 times lower, than its nominal 16-bit range. this gives a dynamic range of 22 bits or slightly over 4,000,000 to 1. in manual mode, the user has access to 4 bits (cdr and tim[2:0]) to override the autoranging circuitry. these affect the integration time of the a/d and the current division ratio. see the register description for manual configuration mode (0x02, bit 6). data format of lux reading the ic has a user-friendly digital output format. it con - sists of a 4-bit exponent followed by an 8-bit mantissa. in its highest sensitivity mode, 1 count represents 0.045 lux. the mantissa has a maximum value of 255, and the exponent has a maximum value of 14. this gives a maxi - mum range: 255 x 2 14 = 4,177,920. at 0.045 lux/lsb, the maximum lux reading is 188,000 lux. any reading greater than that (i.e., exponent = 15) is considered to be an overload. no conversion formulas are needed as in the case of dual-diode ambient light sensors. the ics output (registers 0x03 and 0x04) comprises a 12-bit result that represents the ambient light expressed in units of lux. here is how lux is calculated: lux = (2 (exponent) x mantissa) x 0.045 the exponent is a 4-bit number ranging from 0000 to 1110 (zero to 14). the mantissa is an 8-bit number ranging from 0000 0000 to 1111 1111 (zero to 255). i f the int e bit = 1 and the ambient light level exceeds either threshold limit for a time longer than that specified by the threshold timer register, then the ints bit is set to 1 and the int pin is pulled low. the value in this register sets the time used to control this delay. a value of 0x00 in this register (with inte bit = 1 in the interrupt enable register) configures the ic to assert the interrupt pin as soon as the light level exceeds either threshold. time delay = (128xt7 + 64xt6 + 32xt5 + 16xt4 + 8xt3 + 4xt2 + 2xt1 + t0) x 100ms. threshold timer register 0x07 the lower threshold register exponent with the four most significant bits of the mantissa sets the lower trip level for interrupt functionality. this lower limit is relevant only if the inte bit in the interrupt enable register is set. if the lux level is below this light level for a time greater than that specified in the threshold timer register, the ints bit in the interrupt status register is set and the int pin is pulled low. mantissa (lm[7:4]): four most significant bits of mantissa lower threshold exponent (le[3:0]): exponent bits lower threshold lower lux threshold = 2 (exponent) x mantissa x 0.045 exponent = 8xle3 + 4xle2 + 2xle1 + le0 mantissa = 128xlm7 + 64xlm6 + 32xlm5 + 16xlm4 lower threshold high-byte register 0x06 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 register address le3 le2 le1 le0 lm7 lm6 lm5 lm4 0x06 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 register address t7 t6 t5 t4 t3 t2 t1 t0 0x07
industrys lowest-power ambient light sensor with adc max9635 12 table 8. lux per lsb in automatic mode the count is multiplied by 0.045, which is the lsb. because of the logarithmic nature of autoranging cir - cuitry implemented on the ic, resolution of ambient lux readings scale with the absolute measurement. table 8 lists the lux resolution and the lux ranges obtained from the ic. interrupt settings interrupt is enabled by setting bit 0 of register 0x01 to 1 (see table 1). int , an open-drain output, pulls low when an interrupt condition occurs (lux readings that exceed threshold limits for a period greater than that set by the time register). the interrupt status bit is cleared automatically if register 0x00 is read or if the interrupt is disabled (inte = 0). threshold register data format the ics interrupt circuit requires the upper and lower limit thresholds to be in a specific format to be properly interpreted. the upper and lower limits, from registers 0x05 and 0x06 must match the lux high-byte format. this consists of the 4 bits of the exponent and the 4 most sig - nificant bits of the mantissa (e3 e2 e1 e0 m7 m6 m5 m4). in this case, there is the following formula: lower lux threshold = (2 (exponent) x mantissa) x 0.045 the exponent is a 4-bit number ranging from 0000 to 1110 (zero to 14). the mantissa is an 8-bit number ranging from 0000 0000 to 1111 0000 (zero to 240). upper lux threshold = ( 2 (exponent) x mantissa) x 0.045 the exponent is a 4-bit number ranging from 0000 to 1110 (zero to 14). the mantissa is an 8-bit number ranging from 0000 1111 to 1111 1111 (15 to 255). in the auto range mode (manual = 0), the upper thresh - old and lower threshold bytes must be in a format that matches the format used in register 0x03, the lux high byte. there are only two rules to follow: ? for very low lux levels (light levels below 11.5 lux), set the exponent to zero, the code is merely: 0000 mmmm where the 4 zeroes are the exponent, and the mmmm represent the 4 most significant bits of the mantissa. ? for all other conditions (light levels above 11.5 lux) where the exponent is not zero, the format is: eeee 1mmm. notice that bit m7 (most significant bit) must always be a 1. the other bits do not matter. eeee is limited to a maximum value of 1110. the maximum usable setting is a code of 1110 1111. in manual mode (manual = 1), table 9 gives the range of exponent (e3 e2 e1 e0) that can be used for each tim[2:0] and cdr bit setting. lux (min) lux (max) lux per lsb in automatic mode counts (min) counts (ma x) 0 11.5 0.045 0 256 11.5 23.0 0.09 256 512 23.0 46.1 0.18 512 1024 46.1 92.2 0.36 1024 2048 92.2 184.3 0.72 2048 4096 184.3 368.6 1.44 4096 8192 368.6 737.3 2.88 8192 16,384 737.3 1474.6 5.76 16,384 32,768 1474.6 2949.1 11.52 32,768 65,536 2949.1 5898.2 23.04 65,536 131,072 5898.2 11,796.5 46.08 131,072 262,144 11,796.5 23,593.0 92.16 262,144 524,288 23,593.0 47,185.9 184.32 524,288 1,048,576 47,185.9 94,371.8 368.64 1,048,576 2,097,152 94,371.8 188,006.4 737.28 2,097,152 4,177,920
industrys lowest-power ambient light sensor with adc max9635 13 table 9. recommended manual mode settings for configuration register (0x02) and threshold registers (0x05, 0x06) note: in manual mode, exceeding the lux (max) causes an overload error (exponent = 1111). typical operating sequence to utilize the ultra-low power consumption of the ic in end applications, an interrupt pin is provided to eliminate the need for the system to poll the device continuously. since every clock and data bit transmitted on i 2 c can consume up to 1ma (assuming 1.8k i pullup resistor to a 1.8v rail), minimizing the number of i 2 c transactions on the data bus can save a lot of power. in addition, eliminating the need to poll the device frees up process - ing resources for the master, improving overall system performance. the typical sequence of communication with the ic is as follows: 1) master reads lux reading from registers 0x03 and 0x04. 2) master sets the upper lux threshold and lower lux threshold in registers 0x05 and 0x06 so that a user- programmed window is defined around the current lux readings. 3) master sets suitable threshold timer data in register 0x07. 4) master works on other tasks until alerted by the int pin going low. this is where the master spends much of its time. 5) when alerted by the int pin going low, the master reads the interrupt status register 0x00 to confirm the source of interrupt was the ic. the master takes appropriate action. 6) repeat from step 1. application conditions recommended settings for configuration register (0x02) range of e x ponents for upper and lower threshold registers (0x05 and 0x06) lux lsb (min) lux (max) lux lsb (max) integration time (ms) tim[2:0] cdr exponent (min) exponent (max) 0.045 2938 11.52 800 000 0 0000 1000 0.09 5875 23.04 400 001 0 0001 1001 0.18 11,750 46.08 200 010 0 0010 1010 0.36 23,501 92.16 100 011 0 0011 1011 800 000 1 0.72 47,002 184.32 50 100 0 0100 1100 400 001 1 1.44 94,003 368.64 25 101 0 0101 1101 200 010 1 2.88 188,006 737.28 12.5 110 0 0110 1110 100 011 1 5.76 188,006 737.28 6.25 111 0 0111 1110 50 100 1 11.52 188,006 737.28 25 101 1 1000 1110 23.04 188,006 737.28 12.5 110 1 1001 1110 46.08 188,006 737.28 6.25 111 1 1010 1110
industrys lowest-power ambient light sensor with adc max9635 14 figure 2. typical operating sequence n n y y star t read max9635 ambient lux, set appropriate backlight strengt h wr it e to upper lux threshold, lower lu x threshold, an d lux th resh ol d timer register s work on tasks/sleep until woken by hard wa re interrup t woken by inte rrupt? read ints bi t to conf ir m check other interrupt sources max9635 caused interrupt?
industrys lowest-power ambient light sensor with adc max9635 15 smbus is a trademark of intel corp. figure 3. 2-wire interface timing diagram i 2 c serial interface the ic features an i 2 c/smbus?-compatible, 2-wire serial interface consisting of a serial-data line (sda) and a serial-clock line (scl). sda and scl facilitate com - munication between the ic and the master at clock rates up to 400khz. figure 3 shows the 2-wire interface timing diagram. the master generates scl and initiates data transfer on the bus. a master device writes data to the ic by transmitting the proper slave address followed by the register address and then the data word. each trans - mit sequence is framed by a start (s) or repeated start (sr) condition and a stop (p) condition. each word transmitted to the ic is 8 bits long and is followed by an acknowledge clock pulse. a master reading data from the ic transmits the proper slave address followed by a series of nine scl pulses. the ic transmits data on sda in sync with the master-generated scl pulses. the master acknowledges receipt of each byte of data. each read sequence is framed by a start or repeated start condition, a not acknowledge, and a stop condi - tion. sda operates as both an input and an open-drain output. a pullup resistor, typically greater than 500 i , is required on the sda bus. scl operates as only an input. a pullup resistor, typically greater than 500 i , is required on scl if there are multiple masters on the bus, or if the master in a single-master system has an open-drain scl output. series resistors in line with sda and scl are optional. series resistors protect the digital inputs of the ic from high-voltage spikes on the bus lines, and mini - mize crosstalk and undershoot of the bus signals. bit transfer one data bit is transferred during each scl cycle. the data on sda must remain stable during the high period of the scl pulse. changes in sda while scl is high are control signals (see the start and stop conditions section). sda and scl idle high when the i 2 c bus is not busy. start and stop conditions sda and scl idle high when the bus is not in use. a master initiates communication by issuing a start con - dition. a start condition is a high-to-low transition on sda with scl high. a stop condition is a low-to-high transition on sda while scl is high (figure 4). a start condition from the master signals the beginning of a transmission to the ic. the master terminates transmis - sion, and frees the bus, by issuing a stop condition. the bus remains active if a repeated start condition is generated instead of a stop condition. early stop conditions the ic recognizes a stop condition at any point during data transmission except if the stop condition occurs in the same high pulse as a start condition. for proper operation, do not send a stop condition during the same scl high pulse as the start condition. scl sda start condition stop condition repeated start condition start condition t hd,sta t su,sta t hd,sta t sp t buf t su,sto t low t su,dat t hd,dat t high t r t f
industrys lowest-power ambient light sensor with adc max9635 16 figure 4. start, stop, and repeated start conditions figure 5. acknowledge table 10. slave address chip information process: bicmos slave address the slave address is controlled by the a0 pin. connect a0 to either ground or v cc to set the address. table 10 shows the two possible addresses for the ic. acknowledge the acknowledge bit (ack) is a clocked 9th bit that the ic uses to handshake receipt each byte of data when in write mode (see figure 5). the ic pulls down sda dur - ing the entire master-generated ninth clock pulse if the previous byte is successfully received. monitoring ack allows for detection of unsuccessful data transfers. an unsuccessful data transfer occurs if a receiving device is busy or if a system fault has occurred. in the event of an unsuccessful data transfer, the bus master can retry communication. the master pulls down sda during the ninth clock cycle to acknowledge receipt of data when the ic is in read mode. an acknowledge is sent by the master after each read byte to allow data transfer to continue. a not acknowledge is sent when the master reads the final byte of data from the ic, followed by a stop condition. write data format a write to the ic includes transmission of a start condi - tion, the slave address with the r/ w bit set to 0, one byte of data to configure the internal register address pointer, one or more bytes of data, and a stop condition. figure 6 illustrates the proper frame format for writing one byte of data to the ic. the slave address with the r/ w bit set to 0 indicates that the master intends to write data to the ic. the ic acknowledges receipt of the address byte during the master-generated ninth scl pulse. the second byte transmitted from the master configures the ics internal register address pointer. the pointer tells the ic where to write the next byte of data. an acknowledge pulse is sent by the ic upon receipt of the address pointer data. the third byte sent to the ic contains the data that is writ - ten to the chosen register. the master signals the end of transmission by issuing a stop condition. read data format to read a byte of data, the register pointer must first be set through a write operation (figure 7). send the slave address with the r/ w set to 0, followed by the address of the register that needs to be read. after a repeated start condition, send the slave address with the r/ w bit set to 1 to initiate a read operation. the ic then sends an acknowledge pulse followed by the contents of the register to be read. transmitted data is valid on the rising edge of the master-generated serial clock (scl). sensor position the photo sensitive area of the ic is 0.37mm x 0.37mm and much smaller than the device itself. when placing the part behind a light guide, only this sensitive area has to be taken into account. figure 8 shows the position and size of the photo sensitive area within the package. scl sda s sr p 1 scl start condition sda 2 8 9 clock pulse for acknowledgment acknowledge not acknowledge a0 slave address for writing slave address for reading gnd 0x94 0x95 v cc 0x96 0x97
industrys lowest-power ambient light sensor with adc max9635 17 figure 6. writing 1 byte of data to the ic figure 7. reading one indexed byte of data from the ic figure 8. sensor position a 0 slave address register address data byte acknowledge from max9635 1 byte acknowledge from max9635 acknowledge from max9635 b1 b0 b3 b2 b5 b4 b7 b6 s a a p r/w acknowledge from max9635 1 byte acknowledge from max9635 not acknowledge from master a a p a 0 acknowledge from max9635 r/w s a r/w repeated start sr 1 slave address register address slave address data byte top view 0.13mm 0.24mm 0.12mm 0.25mm center of max9635 max9635 1 6 v cc sda 2 5 gnd scl 3 4 a0 int 0.88mm 0.75mm 2mm 0.76mm 0.87mm 2mm
industrys lowest-power ambient light sensor with adc max9635 18 typical application circuit 1.7v to 3.6v 1f v cc to 3.6v 0v to v cc 10ki 10ki 10ki sda micro- controller (i 2 c master) scl sda i 2 c slave_n v cc gnd a0* *device address is 0x94. connect a0 to v cc for slave address 0x96. see the pin description. int scl sda scl int max9635 scl sda i 2 c slave_1
industrys lowest-power ambient light sensor with adc max9635 19 package information for the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. package type package code outline n o. land pattern no. 6 otdfn d622n+1 21-0490 90-0344
industrys lowest-power ambient light sensor with adc max9635 maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 20 maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2011 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 8/10 initial release 1 2/11 updated test time and repeatability 2

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