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agilent hcms-29xx series high performance cmos 5 x 7 alphanumeric displays data sheet features ? easy to use ? interfaces directly with microprocessors ? 0.15" character height in 4, 8, and 16 (2x8) character packages ? 0.20" character height in 4 and 8 character packages ? rugged x- and y-stackable package ? serial input ? convenient brightness controls ? wave solderable ? offered in five colors ? low power cmos technology ? ttl compatible applications ? telecommunications equipment ? portable data entry devices ? computer peripherals ? medical equipment ? test equipment ? business machines ? avionics ? industrial controls device selection guide algaas her orange yellow green package description hcms- hcms- hcms- hcms- hcms- drawing 1 x 4 0.15" character 2905 2902 2904 2901 2903 a 1 x 8 0.15" character 2915 2912 2914 2911 2913 b 2 x 8 0.15" character 2925 2922 2924 2921 2923 c 1 x 4 0.20" character 2965 2962 2964 2961 2963 d 1 x 8 0.20" character 2975 2972 2974 2971 2973 e esd warning: standard cmos handling precautions should be observed to avoid static discharge. description the hcms-29xx series are high performance, easy to use dot matrix displays driven by on- board cmos ics. each display can be directly interfaced with a microprocessor, thus eliminating the need for cumbersome interface components. the serial ic interface allows higher char- acter count information displays with a minimum of data lines. a variety of colors, font heights, and character counts gives designers a wide range of prod- uct choices for their specific applications and the easy to read 5 x 7 pixel format allows the display of uppercase, lower case, katakana, and custom user-defined characters. these displays are stackable in the x- and y- directions, making them ideal for high character count displays.
2 hcms-291x hcms-290x notes: 1. dimensions are in mm (inches). 2. unless otherwise specified, tolerance on dimensions is ?0.38 mm (0.015 inch). 3. lead material: solder plated copper alloy. xz coo 2.11 (0.083) typ. 0.25 (0.010) 7.62 (0.300) pin # 1 identifier 4 3 2 1 17.78 (0.700) max. 3.71 (0.146) typ. 4.45 (0.175) typ. 2.22 (0.087) sym. 10.16 (0.400) max. pin # 1 light intensity category date code color bin country of origin part number 5.08 (0.200) 2.54 (0.100) sym. typ. 0.51 ?0.13 (0.020 ?0.005) 2.54 ?0.13 (0.100 ?0.005) (non accum.) typ. 4.32 (0.170) typ. 1.27 (0.050) sym. 1 12 0.51 (0.020) data out osc v led data in rs clk ce blank gnd sel v logic reset pin function assignment table 1 2 3 4 5 6 7 8 9 10 11 12 pin # function hcms-290x yyww notes: 1. dimensions are in mm (inches). 2. unless otherwise specified, tolerance on dimensions is ?0.38 mm (0.015 inch). 3. lead material: solder plated copper alloy. 2.54 ?0.13 (0.100 ?0.005) (non accum.) typ. 35.56 (1.400) max. 7 6 5 4 3 2 1 0 0.25 (0.010) 7.62 (0.300) pin # 1 identifier xz coo intensity category date code (year, week) color bin country of origin part number 5.08 (0.200) 2.54 (0.100) sym. 0.51 (0.020) typ. 0.51 ?0.13 (0.020 ?0.005) 2.22 (0.087) sym. 10.16 (0.400) max. 2.11 (0.083) typ. 4.32 (0.170) typ. 1.27 (0.050) sym. 4.45 (0.175) typ. 3.71 (0.146) typ. no pin no pin v led no pin no pin no pin gnd led no pin no pin v led no pin no pin no pin data in rs no pin clock ce blank gnd logic sel v logic no pin reset osc data out pin function assignment table 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 pin # function 3 26 hcms-291x yyww
3 hcms-292x hcms-296x no pin no pin v led no pin no pin no pin gnd led no pin no pin v led no pin no pin no pin data in rs no pin clock ce blank gnd logic sel v logic no pin reset osc data out pin function assignment table no pin no pin v led no pin no pin no pin gnd led no pin no pin v led no pin no pin no pin data in rs no pin clock ce blank gnd logic sel v logic no pin reset osc data out 1a 2a 3a 4a 5a 6a 7a 8a 9a 10a 11a 12a 13a 14a 15a 16a 17a 18a 19a 20a 21a 22a 23a 24a 25a 26a pin # function notes: 1. dimensions are in mm (inches). 2. unless otherwise specified, tolerance on dimensions is ?0.38 mm (0.015 inch). 3. lead material: solder plated copper alloy. 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 1.27 (0.050) 0.25 (0.010) 7.62 (0.300) 2.03 (0.080) 4.83 (0.190) pin # 1 identifier row a row b 35.56 (1.400) max. 3.71 (0.146) typ. 2.22 (0.088) sym. 4.45 (0.175) max. 19.81 (0.780) max. 9.65 (0.380) xz coo intensity category date code (year, week) color bin country of origin part number 5.08 (0.200) 2.54 (0.100) sym. 0.51 (0.020) 0.51 ?0.13 (0.020 ?0.005) typ. 2.54 ?0.13 (0.100 ?0.005) (non accum.) typ. 3a 26a 3b 26b 2.11 (0.083) typ. 1b 2b 3b 4b 5b 6b 7b 8b 9b 10b 11b 12b 13b 14b 15b 16b 17b 18b 19b 20b 21b 22b 23b 24b 25b 26b pin # function hcms-292x yyww notes: 1. dimensions are in mm (inches). 2. unless otherwise specified, the tolerance on dimensions is ?0.38 mm (0.015 inch). 3. lead material: solder plated copper alloy. 3 2 1 0 pin # 1 identifier part number 5.31 (0.209) 0.169 (4.28) sym. typ. 0.51 ?0.13 (0.020 ?0.005) 2.54 ?0.13 (0.100 ?0.005) typ. 2.67 (0.105) sym. 2.54 (0.100) typ. 11.43 (0.450) max. 5.36 (0.211) typ. 0.25 (0.010) 7.62 (0.300) 3.71 (0.146) typ. 0.072 (1.83) sym. 4.57 (0.180) typ. xz coo intensity category date code (year, week) color bin country of origin 21.46 (0.845) max. 0.50 (0.020) data out osc v led data in rs clk ce blank gnd sel v logic reset 1 2 3 4 5 6 7 8 9 10 11 12 pin function assignment table pin # function hcms-296x yyww
4 absolute maximum ratings logic supply voltage, v logic to gnd logic -0.3 v to 7.0 v led supply voltage, v led to gnd led -0.3 v to 5.5 v input voltage, any pin to gnd -0.3 v to v logic +0.3 v free air operating temperature range t a [1] -40 c to +85 c relative humidity (noncondensing) 85% storage temperature, t s -55 c to 100 c soldering temperature [1.59 mm (0.063 in.) below body] solder dipping 260 c for 5 secs wave soldering 250 c for 3 secs esd protection @ 1.5 k ? , 100 pf (each pin) class 1, 0-1999 v total package power dissipation at t a = 25 c [2] 4 character 1.2 w 8 character 2.4 w 16 character 4.8 w notes: 1. for operation in high ambient temperatures, see appendix a, thermal considerations. hcms-297x recommended operating conditions over temperature range (-40 c to +85 c) parameter symbol min. typ. max. units logic supply voltage v logic 3.0 5.0 5.5 v led supply voltage v led 4.0 5.0 5.5 v gnd led to gnd logic -0.3 0 +0.3 v pin function assignment table notes: 1. dimensions are in mm (inches). 2. unless otherwise specified, tolerance on dimensions is ?0.38 mm (0.015 inch). 3. lead material: solder plated copper alloy. 8 7 6 5 4 3 2 1 xz coo pin # 1 identifier intensity category date code (year, week) color bin country of origin part number 5.31 (0.209) 6.22 (0.245) sym. 0.51 (0.020) typ. 0.51 ?0.13 (0.020 ?0.005) 2.54 ?0.13 (0.100 ?0.005) (non accum.) typ. 42.93 (1.690) max. 2.67 (0.105) sym. 5.36 (0.211) typ. 11.43 (0.450) max. 2.54 (0.100) typ. 0.25 (0.010) 7.62 (0.300) 3.71 (0.146) typ. 1.90 (0.075) sym. no pin no pin v led no pin no pin no pin gnd led no pin no pin v led no pin no pin no pin data in rs no pin clock ce blank gnd logic sel v logic no pin reset osc data out 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 pin # function 4.57 (0.180) typ. 3 26 hcms-297x yyww
5 electrical characteristics over operating temperature range (-40 c to +85 c) t a = 25 c -40 c < t a < 85 c v logic = 5.0 v 3.0 v < v logic < 5.5 v parameter symbol typ. max. min. max. units test conditions input leakage current i i av in = 0 v to v logic hcms-290x/296x (4 char) +7.5 -2.5 +50 hcms-291x/297x (8 char) +15 -5.0 +100 hcms-292x (16 char) +15 -5.0 +100 i logic operating i logic (opt) ma v in = v logic hcms-290x/296x (4 char) 0.4 2.5 5 hcms-291x/297x (8 char) 0.8 5 10 hcms-292x (16 char) 0.8 5 10 i logic sleep [1] i logic (slp) av in = v logic hcms-290x/296x (4 char) 5 15 25 hcms-291x/297x (8 char) 10 30 50 hcms-292x (16 char) 10 30 50 i led blank i led (bl) ma bl = 0 v hmcs-290x/296x (4 char) 2.0 4 4.0 hcms-291x/297x (8 char) 4.0 8 8 hcms-292x (16 char) 4.0 8 8 i led sleep [1] i led (slp) a hcms-290x/296x (4 char) 1 3 50 hcms 291x/297x (8 char) 2 6 100 hcms-292x (16 char) 2 6 100 peak pixel current [2] i pixel v led = 5.5 v hcms-29x5 (algaas) 15.4 17.1 18.7 ma all pixels on, hcms-29xx (other colors) 14.0 15.9 17.1 ma average value per pixel high level input voltage v ih 2.0 v 4.5 v < v logic < 5.5 v 0.8 v logic v 3.0 v < v logic < 4.5 v low level input voltage v il 0.8 v 4.5 v < v logic < 5.5 v 0.2 v logic v 3.0 v < v logic < 4.5 v high level output voltage v oh 2.0 v v logic = 4.5 v, i oh = -40 a 0.8 v logic v 3.0 v < v logic < 4.5 v low level output voltage v ol 0.4 v v logic = 5.5 v, i ol = 1.6 ma [3] 0.2 v logic v 3.0 v < v logic < 4.5 v thermal resistance r q j-p 70 c/w ic junction to pin notes: 1. in sleep mode, the internal oscillator and reference current for led drivers are off. 2. average peak pixel current is measured at the maximum drive current set by control register 0. individual pixels may exceed t his value. 3. for the oscillator output, i ol = 40 a.
6 electrical description pin function description reset (rst) sets control register bits to logic low. the dot register contents are unaffected by the reset pin. (logic low = reset; logic high = normal operation). data in (d in ) serial data input for dot or control register data. data is entered on the rising edge of the clock input. data out (d out ) serial data output for dot or control register data. this pin is used for cascading multiple displays. clock (clk) clock input for writing dot or control register data. when chip enable is logic low, data is entered on the rising clock edge. register select (rs) selects dot register (rs = logic low) or control register (rs = logic high) as the destination for serial data entry. the logic level of rs is latched on the falling edge of the chip enable input. chip enable (ce) this input must be a logic low to write data to the display. when ce returns to logic high and clk is logic low, data is latched to either the led output drivers or a control register. oscillator select selects either an internal or external display oscillator source. (sel) (logic low = external display oscillator; logic high = internal display oscillator). oscillator (osc) output for the internal display oscillator (sel = logic high) or input for an external display oscillator (sel = logic low). blank (bl) blanks the display when logic high. may be modulated for brightness control. gnd led ground for led drivers. gnd logic ground for logic. v led positive supply for led drivers. v logic positive supply for logic. optical characteristics at 25 c [1] v led = 5.0 v, 50% peak current, 100% pulse width peak dominant luminous intensity per led [2] wavelength wavelength character average ( cd) l peak (nm) l d [3] (nm) display color part number min. typ. typ. typ. algaas red hcms-29x5 95 230 645 637 high efficiency red hcms-29x2 29 64 635 626 orange hcms-29x4 29 64 600 602 yellow hcms-29x1 29 64 583 585 green hcms-29x3 57 114 568 574 notes: 1. refers to the initial case temperature of the device immediately prior to measurement. 2. measured with all leds illuminated. 3. dominant wavelength, l d , is derived from the cie chromaticity diagram and represents the single wavelength which defines the perceived led color.
7 ac timing characteristics over temperature range (-40 c to +85 c) timing diagram ref. 4.5 v < v logic <5.5 v v logic = 3 v number description symbol min. max. min. max. units 1 register select setup time to chip enable t rss 10 10 ns 2 register select hold time to chip enable t rsh 10 10 ns 3 rising clock edge to falling t clkce 20 20 ns chip enable edge 4 chip enable setup time to rising clock edge t ces 35 55 ns 5 chip enable hold time to rising clock edge t ceh 20 20 ns 6 data setup time to rising clock edge t ds 10 10 ns 7 data hold time after rising clock edge t dh 10 10 ns 8 rising clock edge to d out [1] t dout 10 40 10 65 ns 9 propagation delay d in to d out t doutp 18 30 ns simultaneous mode for one ic [1,2] 10 ce falling edge to d out valid t cedo 25 45 ns 11 clock high time t clkh 80 100 ns 12 clock low time t clkl 80 100 ns reset low time t rstl 50 50 ns clock frequency frequency f cyc 5 4 mhz internal display oscillator f inosc 80 210 80 210 khz internal refresh frequency f rf 150 410 150 400 hz external display oscillator f exosc prescaler = 1 51.2 1000 51.2 1000 khz prescaler = 8 410 8000 410 8000 khz notes: 1. timing specifications increase 0.3 ns per pf of capacitive loading above 15 pf. 2. this parameter is valid for simultaneous mode data entry of the control register.
8 reset reset initializes the control registers (sets all control register bits to logic low) and places the display in the sleep mode. the reset pin should be connected to the system power-on reset circuit. the dot registers are not cleared upon power-on or by reset. after power-on, the dot register contents are random; however, reset will put the display in sleep mode, thereby blanking the leds. the control register and the control words are cleared to all zeros by reset. to operate the display after being reset, load the dot register with logic lows. then load control word 0 with the desired brightness level and set the sleep mode bit to logic high. dot register the dot register holds the pattern to be displayed by the leds. data is loaded into the dot register according to the display overview the hcms-29xx series is a family of led displays driven by on-board cmos ics. the leds are configured as 5 x 7 font characters and are driven in groups of 4 characters per ic. each ic consists of a 160-bit shift register (the dot register), two 7-bit control words, and refresh circuitry. the dot regis- ter contents are mapped on a one-to-one basis to the display. thus, an individual dot register bit uniquely controls a single led. 8-character displays have two ics that are cascaded. the data out line of the first ic is internally connected to the data in line of the second ic forming a 320-bit dot register. the dis- plays other control and power lines are connected directly to both ics. in 16-character displays, each row functions as an independent 8-character display with its own 320-bit dot register. procedure shown in table 1 and the write cycle timing diagram. first rs is brought low, then ce is brought low. next, each successive rising clk edge will shift in the data at the d in pin. loading a logic high will turn the corresponding led on; a logic low turns the led off. when all 160 bits have been loaded (or 320 bits in an 8-digit display), ce is brought to logic high. when clk is next brought to logic low, new data is latched into the display dot drivers. loading data into the dot register takes place while the previous data is displayed and eliminates the need to blank the display while loading data. pixel map in a 4-character display, the 160-bits are arranged as 20 columns by 8 rows. this array can be conceptualized as four 5 x 8 dot matrix character loca- table 1. register truth table function clk ce rs select dot register not rising # l load dot register d in = high led = "on" ! lx d in = low led = "off" copy data from dot register to dot latch l h x select control register not rising # h load control register [1,3] ! lx latch data to control word [2] l ! x notes: 1. bit d 0 of control word 1 must have been previously set to low for serial mode or high for simultaneous mode. 2. selection of control word 1 or control word 0 is set by d 7 of the control shift register. the unselected control word retains its previous value. 3. control word data is loaded most significant bit (d 7 ) first.
9 successive rising clk edge will shift in the data on the d in pin. finally, when 8 bits have been loaded, the ce line is brought to logic high. when clk goes to logic low, new data is copied into the selected control word. loading data into the control register takes place while the previous control word configures the display. control word 0 loading the control register with d 7 = logic low selects control word 0 (see table 2). bits d 0 -d 3 adjust the display brightness by pulse width modulating the led on-time, while bits d 4 -d 5 adjust the display brightness by changing the peak pixel current. bit d 6 selects normal operation or sleep mode. control register the control register allows software modification of the ics operation and consists of two independent 7-bit control words. bit d 7 in the shift register selects one of the two 7-bit control words. control word 0 performs pulse width modula- tion brightness control, peak pixel current brightness control, and sleep mode. control word 1 sets serial/simultaneous data out mode, and external oscilla- tor prescaler. each function is independent of the others. control register data loading data is loaded into the control register, msb first, according to the procedure shown in table 1 and the write cycle timing diagram. first, rs is brought to logic high and then ce is brought to logic low. next, each tions, but only 7 of the 8 rows have leds (see figures 1 & 2). the bottom row (row 0) is not used. thus, latch location 0 is never displayed. column 0 controls the left-most column. data from dot latch locations 0-7 determine whether or not pixels in column 0 are turned-on or turned-off. therefore, the lower left pixel is turned-on when a logic high is stored in dot latch location 1. characters are loaded in serially, with the left-most character being loaded first and the right-most character being loaded last. by loading one character at a time and latching the data before loading the next character, the figures will appear to scroll from right to left. hcms-29xx write cycle diagram note: 1. data is copied to the control register or the dot latch and led outputs when ce is high and clk is low. t rss rsh t t clkce ces t clkh t clkl t ceh t ds t dh t cedo t dout t doutp t previous data new data new data latched here [1] ce rs clk d in led outputs, control registers (simultaneous) out d d (serial) out 2 1 3 4 11 12 6 7 8 10 9 5
10 figure 2. figure 1. 40 bit s.r. do di data in oscillator ? clk chip enable register select reset osc osc select blank data in clr data out control register refresh control rst prescale value h l h l l h d q rs (latched) l h current reference pwm brightness control l h l h rs (latched) ser/par mode 3:8 decoder 40 bit s.r. do di 40 bit s.r. do di 40 bit s.r. do di anode current sources v led + gnd (led) 0 char 0 column 0 column 19 char 1 char 2 char 3 row 7 dot register bit # 159 row 1 row 0 (no leds) dot registers and latches data out cathode field drivers xxxx xxxxx xxxxx xxxxx row 0 (not used) data to next character pixel data from previous character row 7 row 6 row 5 row 4 row 3 row 2 row 1
11 are connected in series to form a 320-bit dot shift register. the location of pixel 0 has not changed. however, dot shift register bit 0 of ic2 becomes bit 160 of the 320-bit dot shift register. the control registers of the two ics are independent of each other. this means that to adjust the display brightness the same control word must be entered into both ics, unless the control registers are set to simultaneous mode. longer character string systems can be built by cascading multi- ple displays together. this is accomplished by creating a five line bus. this bus consists of ce, rs, bl, reset, and clk. the display pins are connected to the corresponding bus line. thus, all ce pins are connected to the ce bus line. similarly, bus lines for rs, bl, reset, and clk are created. then d in is connected to the right-most display. d out from this display is connected to the next display. the left-most display receives its d in from the d out of the display to its right. d out from the left-most display is not used. each display may be set to use its internal oscillator, or the displays may be synchronized by setting up one display as the master and the others as slaves. the slaves are set to receive their oscillator input from the masters oscillator output. sleep mode (control word 0, bit d 6 = low) turns off the internal display oscillator and the led pixel drivers. this mode is used when the ic needs to be powered up, but does not need to be active. current draw in sleep mode is nearly zero. data in the dot register and control words are retained during sleep mode. control word 1 loading the control register with d 7 = logic high selects control word 1. this control word performs two functions: serial/simultaneous data out mode and external oscillator prescale select (see table 2). serial/simultaneous data output d 0 bit d 0 of control word 1 is used to switch the mode of d out between serial and simultaneous data entry during control register writes. the default mode (logic low) is the serial d out mode. in serial mode, d out is connected to the last bit (d 7 ) of the control shift register. storing a logic high to bit d 0 changes d out to simultaneous mode which affects the control register only. in simultaneous mode, d out is logically con- nected to d in . this arrangement allows multiple ics to have their control registers written to simultaneously. for example, for n ics in the serial mode, n * 8 clock pulses are needed to load the same data in all control registers. in the simultaneous mode, n ics only need 8 clock pulses to load the same data in all control registers. the propagation delay from the first ic to the last is n * t doutp . external oscillator prescaler bit d 1 bit d 1 of control word 1 is used to scale the frequency of an external display oscillator. when this bit is logic low, the external display oscillator directly sets the internal display clock rate. when this bit is a logic high, the external oscillator is divided by 8. this scaled frequency then sets the internal display clock rate. it takes 512 cycles of the display clock (or 8 x 512 = 4096 cycles of an external clock with the divide by 8 prescaler) to completely refresh the display once. using the prescaler bit allows the designer to use a higher external oscillator frequency without extra circuitry. this bit has no affect on the internal display oscillator frequency. bits d 2 -d 6 these bits must always be pro- grammed to logic low. cascaded ics figure 3 shows how two ics are connected within an hcms-29xx display. the first ic controls the four left-most characters and the second ic controls the four right-most characters. the dot registers
12 bit d 7 on-time duty relative set low pwm brightness oscillator factor brightness to select control cycles (%) (%) control word 0 llll 0 0 0 lllh 1 0.2 1.7 llhl 2 0.4 3.3 llhh 3 0.6 5.0 lhll 4 0.8 6.7 lhlh 5 1.0 8.3 l h h l 7 1.4 11.7 lhhh 9 1.8 15 hlll 11 2.1 18 hllh 14 2.7 23 hlhl 18 3.5 30 hlhh 22 4.3 37 hhl l 28 5.5 47 hhlh 36 7.0 60 hhhl 48 9.4 80 hhhh 60 11.7 100 table 2. control shift register control word 0 ld 6 d 5 d 4 d 3 d 2 d 1 d 0 peak current typical peak relative full brightness pixel current scale current control (ma) (relative brightness, %) hl 4.0 31 lh 6.4 50 l l 9.3 73 (default at power up) h h 12.8 100 sleep mode l ?disables internal oscillator-display blank h ?normal operation serial/simultaneous data out l ?d out holds contents of bit d 7 h ?d out is functionally tied to d in external display oscillator prescaler l ?oscillator freq 1 h ?oscillator freq 8 bit d 7 set high to select control word 1 reserved for future use (bits d 2 -d 6 must be set low) control word 1 hllllld 1 d 0
13 figure 3. cascaded ics. ce ic2 bits 160-319 characters 4-7 rs bl sel osc clk d out d in ic1 bits 0-159 characters 0-3 d in rs bl sel osc clk d out ce reset reset rs bl sel osc clk d out ce reset d in
14 p d can be calculated as equation 2 below. figure 4 shows how to derate the power of one ic versus ambient temperature. operation at high ambient temperatures may require the power per ic to be reduced. the power con- sumption can be reduced by changing either the n, i pixel , osc cyc or v led . changing v logic has very little impact on the power consumption. appendix a. thermal considerations the display ic has a maximum junction temperature of 150 c. the ic junction temperature can be calculated with equation 1 below. a typical value for r q ja is 100 c/w. this value is typical for a display mounted in a socket and covered with a plastic filter. the socket is soldered to a .062 in. thick pcb with .020 inch wide, one ounce copper traces. equation 1: t j max = t a + p d * r q ja where: t j max = maximum ic junction temperature t a = ambient temperature surrounding the display r q ja = thermal resistance from the ic junction to ambient p d = power dissipated by the ic equation 2: p d = (n * i pixel * duty factor * v led ) + i logic * v logic where: p d = total power dissipation n = number of pixels on (maximum 4 char * 5 * 7 = 140) i pixel = peak pixel current. duty factor = 1/8 * osccyc/64 osc cyc = number of on oscillator cycles per row i logic = ic logic current v logic = logic supply voltage equation 3: i peak = m * 20 * i pixel where: i peak = maximum instantaneous peak current for the display m = number of ics in the system 20 = maximum number of leds on per ic i pixel = peak current for one led equation 4: i led (avg) = n * i pixel * 1/8 * (oscillator cycles)/64 (see variable definitions above) appendix b. electrical considerations current calculations the peak and average display current requirements have a significant impact on power supply selection. the maximum peak current is calculated with equation 3 below. the average current required by the display can be calculated with equation 4 below. the power supply has to be able to supply i peak transients and supply i led (avg) continuously. the range on v led allows noise on this supply without signifi- cantly changing the display brightness. v logic and v led considerations the display uses two indepen- dent electrical systems. one system is used to power the displays logic and the other to power the displays leds. these two systems keep the logic supply clean. separate electrical systems allow the voltage applied to v led and v logic to be varied independently. thus, v led can figure 4. p d max maximum power dissipation per ic w 0 25 t a ambient temperature c 0.7 0.6 0.5 0.4 0.3 0.2 0.1 60 55 50 45 40 35 30 0.8 0.9 1.0 1.1 1.2 85 80 75 70 65 90 1.3 r = 100 c/w j-a
15 vary from 0 to 5.5 v without affecting either the dot or the control registers. v led can be varied between 4.0 to 5.5 v with- out any noticeable variation in light output. however, operating v led below 4.0 v may cause objectionable mismatch between the pixels and is not recommended. dimming the display by pulse width modulat- ing v led is also not recommended. v logic can vary from 3.0 to 5.5 v without affecting either the displayed message or the display intensity. however, operation below 4.5 v will change the timing and logic levels and operation below 3 v may cause the dot and control registers to be altered. the logic ground is internally connected to the led ground by a substrate diode. this diode becomes forward biased and conducts when the logic ground is 0.4 v greater then the led ground. the led ground and the logic ground should be connected to a common ground which can withstand the current introduced by the switching led drivers. when separate ground connections are used, the led ground can vary from -0.3 v to +0.3 v with respect to the logic ground. voltages below -0.3 v can cause all the dots to be on. voltage above +0.3 v can cause dimming and dot mismatch. the led ground for the led drivers can be routed separately from the logic ground until an appropriate ground plane is available. on long interconnections between the display and the host system, voltage drops on the analog ground can be kept from affecting the display logic levels by isolating the two grounds. electrostatic discharge the inputs to the ics are pro- tected against static discharge and input current latchup. how- ever, for best results, standard cmos handling precautions should be used. before use, the hcms-29xx should be stored in antistatic tubes or in conductive material. during assembly, a grounded conductive work area should be used and assembly personnel should wear conduc- tive wrist straps. lab coats made of synthetic material should be avoided since they are prone to static buildup. input current latchup is caused when the cmos inputs are subjected to either a voltage below ground (v in < ground) or to a voltage higher then v logic (v in > v logic ) and when a high current is forced into the input. to prevent input current latchup and esd damage, unused inputs should be connected to either ground or v logic . voltages should not be applied to the inputs until v logic has been applied to the display. appendix c. oscillator the oscillator provides the internal refresh circuitry with a signal that is used to synchron- ize the columns and rows. this ensures that the right data is in the dot drivers for that row. this signal can be supplied from either an external source or the internal source. a display refresh rate of 100 hz or faster ensures flicker-free operation. thus for an external oscillator the frequency should be greater than or equal to 512 x 100 hz = 51.2 khz. operation above 1 mhz without the prescaler or 8 mhz with the prescaler may cause noticeable pixel to pixel mismatch. appendix d. refresh circuitry this display driver consists of 20 one-of-eight column decoders and 20 constant current sources, 1 one-of-eight row decoder and eight row sinks, a pulse width modulation control block, a peak current control block, and the circuit to refresh the leds. the refresh counters and oscillator are used to synchronize the columns and rows. the 160 bits are organized as 20 columns by 8 rows. the ic illuminates the display by sequentially turning on each of the 8 row-drivers. to refresh the display once takes 512 oscillator cycles. because there are eight row drivers, each row driver is selected for 64 (512/8) oscillator cycles. four cycles are used to briefly blank the display before the following row is switched on. thus, each row is on for 60 oscillator cycles out of a possible 64. this corresponds to the maximum led on time. appendix e. display brightness two ways have been shown to control the brightness of this led display: setting the peak current and setting the duty factor. both values are set in control word 0. to compute the resulting display brightness when both pwm and peak current control are used, simply multiply the two relative bright- ness factors. for example, if control register 0 holds the word 1001101, the peak current is 73% of full scale (bit d 5 = l, bit d 4 = l) and the pwm is set to 60% duty factor (bit d 3 = h, bit d 2 = h, bit d 1 = l, bit d 0 = h). the resulting brightness is 44% (.73 x .60 = .44) of full scale.
www.agilent.com/semiconductors for product information and a complete list of distributors, please go to our web site. for technical assistance call: americas/canada: +1 (800) 235-0312 or (916) 788-6763 europe: +49 (0) 6441 92460 china: 10800 650 0017 hong kong: (+65) 6756 2394 india, australia, new zealand: (+65) 6755 1939 japan: (+81 3) 3335-8152(domestic/interna- tional), or 0120-61-1280(domestic only) korea: (+65) 6755 1989 singapore, malaysia, vietnam, thailand, philippines, indonesia: (+65) 6755 2044 taiwan: (+65) 6755 1843 data subject to change. copyright ?2004-2005 agilent technologies, inc. obsoletes 5988-4161en may 30, 2005 5989-3181en the temperature of the display will also affect the led bright- ness as shown in figure 5. appendix f. reference material application note 1027: soldering led components application note 1015: contrast enhancement techniques for led displays figure 5. relative luminous intensity (normalized to 1 at 25 c) yellow her/orange 0.2 -55 t a ambient temperature c 3.0 2.6 2.2 1.8 1.4 1.0 0.6 85 65 45 25 5 -15 -35 green algaas

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