GM6486 1 GM6486 33 output led driver general description the GM6486 is a monolithic mos integrated circuit produced with high voltage cmos technology. it is available in a 40 - pin dual in - line plastic package. a sin - gle pin controls the led display brightness by setting a reference current through a variable resistor connect - ed to vdd or to a separated supply of 13.2v maximum. features l 33 output, 15ma sink capability l current generator outputs (no external resistros required) l continous brightness control l s erial data input - output l external load input l cascade operation capability l wide supply voltage range l ttl compatibility block diagram application l microprocessor displays l industrial control indicator l relay driver l instrumentation r eadouts pin configuration 40 pin dip 44 pin plcc ss v out bit 16 out bit 15 out bit 14 out bit 13 out bit 12 out bit 11 out bit 10 out bit 9 out bit 8 out bit 7 out bit 6 out bit 5 out bit 4 out bit 3 out bit 2 data out brightness control out bit 17 out bit 18 out bit 19 out bit 20 out bit 21 out bit 22 out bit 23 out bit 24 out bit 25 out bit 26 out bit 27 out bi t 28 out bit 29 out bit 30 out bit 31 out bit 32 out bit 33 load data in clock in dd v 1 2 3 4 5 6 7 8 9 10 11 12 17 18 19 20 13 14 15 16 40 39 38 37 36 35 34 33 32 31 3 0 29 24 23 22 21 28 27 26 25 GM6486 top view out bit 1 33 output buffes 33 latches 33 bit shift register brightness control output bit 33 output bit 1 serial data load clock data out inf v dd 750 m 100k w typ 1 v ss 20 24 17 18 23 22 21 out bit 12 out bit 11 out bit 10 out bit 9 out bit 8 out bit 7 out bit 6 out bit 5 out bit 4 out bit 3 out bit 2 out bit 21 out bit 22 out bit 23 out bit 24 out bit 25 out bit 26 out bit 27 out bit 28 out bit 29 out bit 30 out bit 31 out bit 20 out bit 19 out bit 18 out bit170 out bit 16 out bit 15 out bit 14 out bit 13 out bit 20 out bit 20 nc nc nc nc out bit 1 load data out bright nes control s data in clock in v dd v ss GM6486 - 44
GM6486 2 absolute maximum rating symbol parame ter ratings unit dd v supply voltage - 0.3 to 15 v in v input voltage - 0.3 to 15 v ) off ( v o off state output voltage 15 v o i output sink current 40 ma 1 (at 25 c ) w tot p tot al package power dissipation 560 (at 85 c ) mw j t junction temperature 150 c op t operating temperature range - 25 to 85 c stg t storage temperature range - 65 to 150 c electrical characteristics ( amb t within operating range, dd v =4.75v to 13.2v ss v =0, unless otherwis e specified) symbol parameter test condition min typ max unit dd v supply voltage 4.75 13.2 v dd i supply current dd v =13.2v all control inputs at ss v =0v 50 1000 a m il v ih v input voltage logical ? 0 ? level logical ? 1 ? level a 10 m input bias 25 . 5 v 75 . 4 dd dd v >5.25 - 0.3 2.2 dd v - 2 0.8 dd v dd v v v v b i brightness input current (note 1) 0.75 ma b v brightness input voltage (pin 19) input current=750 a m 3 4.3 v ) off ( v o off state out. voltage 13.2 v oh i ol i output sink current (note 2) segment off segment on v 3 v o = v 1 v o = (note 3) bright in =0 a m bright in =100 a m bri ght in =750 a m 0 2 12 2.7 15 10 10 4 25 a m a m ma ma o i maximum segment current 40 ma
GM6486 3 symbol parameter test condition min typ max unit m o output matching (note 4) 20 % ol v oh v data output logical ? 0 ? level logical ? 1 ? level ma 5 . 0 i out = a 100 i out m = ss v 2.4 0.4 dd v v v c f th l t clock input frequency high time low time (notes 5 and 6) 950 950 500 khz ns ns ds t dh t data input set - up time hold time 300 300 ns ns des t data enable input set - up time 100 ns note: 1. with a fixed resistor on the brightness input, some variation in brightness will occur from one device to another. 2. absolute maximum for each output should be limited to 40 ma. 3. the o v voltage should be regulated by the user. see figures 6 and 7 for allowable o v versus o i operation. 4. output matching is calculated as the percent variation (lmax+lmin)/2. 5. ac input waveform specification for tes t prupose: ns 20 t r . ns 20 t f . f=500khz 10% duty cycle 6. clock input rise and fall times must not exceed 300ns. functional description the GM6486 is specifically designed to operate 4 digit displays wit h minimal interface with the display and the data source. serial data transfer from the data source to the display driver is accomplished with 3 signals, serial data, clock and load. the 33 data bits are latched by a positive pulse, thus providing non - mul tiplexed direct drive to the display. outputs change only if the serial data bits differ from the previous time. display brightness is determined by con - trol of the output current of led drivers. a 1nf capacitor should be connected to brightness control, p in 19, to prevent possible oscillation. a block diagram is shown in figure 1. the output current is typically 20 times greater than the current into pin 19, which is set by an external variable resistor. there is an internal limiting resistor of 400 w nominal value. figure 2 and 3 show the input data format. bit ? 1 ? is the first bit into the data input pin and it will appear on pin 17. a logical ? 1 ? at the input will turn on the appropriate led. the load signal latches the 33 bit of the shift registers into the latches. the data out pin allows for cascading the shift registers for more than 33 output drivers. when power is first applied to the chip an internal power on reset signal is generated which resets all registers and all latches. the first clock return the chip to its normal operation. figure 4 shows the timing relationship between data, clock and load. a max clock frequency of 0.5mhz is assumed. for applications where less number of outputs are used, it is possible to either incre ase the current per output or operate the part at higher than 1v o v . the following equation can be used for calculation. = ) i ( ) v [( t led o j (no. of segments)+(vdd 7ma)](124 c /w)+tamb where = j t junction temperature (+150 c max) 124 c /w=thermal coefficient of package o v =the voltage at the led driver outputs temb=ambient temperature led i =t he led current the above equation was used to plot figure 5, 6 and 7.
GM6486 4 leading clock is necessary after power on and load signal high. reset pulse 1: internal pulse that comes after power on ? effective on both shift register and latches reset pulse 2: internal pulse that comes load pulse ? effective on shift register only. fig. 2. data input format fig. 3. power on reset fig. 4. timing diagram clock leading clo ck leading clock data load reset (internal) bit 1 bit 2 bit 32 bit 33 bit 1 reset pulse 1 reset pulse 2 vdd clock reset (internal) 300ns min clock data load r t t h f t l t dh t ds t des t 1 2 1 32 33
GM6486 5 fig. 5 fig. 6 fig. 7 typical applications basic electronically turned ratio or tv system am fm GM6486 display driver electronig unigng controller key board pll synthesizer 33 segment station detect etc. plot (w) 0.8 0.6 0.4 0.2 0 20 40 60 0 4 8 12 16 20 0.6 1.2 1.8 2.4 24 0 4 8 12 16 20 24 28 32 5 15 25 35 45 55 65 75 85 o v o i (ma) tamb ( c ) led i n (ma) se safe operating area 20segm 33segm 30segm c 85 = tamb ) max ( c 150 = t j v 5 . 1 = v o v 1 = v o v 2 = v o 33 segments v0=1v 15ma/segmen t maxio=40ma
GM6486 6 typical applications (continued) duplexing 8 digits with one GM6486 power dissipations of the ic the power dissipation of the ic can be limited by using different configulation. a) 9 - 15 2 - 8, 40 32 - 39 24 - 31 GM6486 16 21 22 19 20 1 23 17 v cc v led v led v dd v dd load data in clock in brightness control v c v out v d i d
GM6486 7 in this application r must be chosen taking into account the worst operating conditions. r is determined by the maximum number of segment activated. d max omin dmax c i ? n v v v = r the worst case condition for the device is when roughly half of the m aximum number of segments are activated. it must be checked that the total power dissipation does not exceed the absolute maximum ratings. in critical cases more resistors can be used in conjuction with groups of segments. in this case the current variatio n in the single resistor is reduced and plot limited. b) in this configuration the drop on the serial connected diodes is quite stable if the diodes are properly chosen. the total power dissipation of the ics is, in first approximation, depen ding only on the number of segments activated. c) in this configuration v out +v d is constant. the total power dissipation of the ic depends only the number of segments activated. v c v c v out +v d
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