1 standard ics fl tube driver BU2879AK the BU2879AK is a driver ic for fluorescent displays. it is equipped with 26 high-voltage withstand outputs and can display from 11 segments of 15 characters to 16 segments of 8 characters. this ic is equipped with a key scanning function, and general-purpose input pins, and is ideal for front panels in vtrs and other equipment. a serial interface allows functions to be controlled from a microcomputer. applications vcrs absolute maximum ratings (ta = 25?, v ss = 0v) parameter applied voltage 1 applied voltage 2 input voltage power dissipation v dd v ee v in pd ?0.3 ~ + 7.0 v dd + 0.3 ~ v dd ?40 ?0.3 ~ v dd + 0.3 850 * v symbol limits unit v v mw operating temperature topr ?25 ~ + 75 c storage temperature tstg ?55 ~ + 125 c note) operation is not guaranteed at these values. note) power dissipation is reduced by 8.5mw for each increase in ta of 1 c over 25 c. * when mounted on a 70 70 1.6mm glass epoxy board features 1) high withstanding voltage output. 2) display modes: 11s 15g ~ 16s 8g. 3) variable display luminance (7 steps). 4) 3-wire serial interface. 5) key scanning function (6 4). 6) internal pull-down resistance (high voltage withstand output). 7) qfp 44 package. recommended operating conditions (ta = 25?, v ss = 0v) parameter operating power supply voltage 1 v dd 4.5 5.0 5.5 v operating power supply voltage 2 v ee v dd ?37 v dd ?35 v dd ?0 v symbol min. typ. max. unit
2 standard ics BU2879AK block diagram cs sck si so s1 s11 s12 / g15 s16 / g11 v ee sw4 sw1 k4 k1 osc g1 g10 v ss 8bit shift-reg. 16bit latch segment driver s / g driver key data latch (4 6) v dd 16bit 15word display data ram osc control logic 4bit data grid driver
3 standard ics BU2879AK pins descriptions pin no. pin name i / o function 14, 38 v dd power supply pin 1 oscillation pin ground pin input input / output input connected to system power supply. osc capacitor connection pin for oscillation 44 v ss connected to system ground. 7, 43 serial data input input si serial data input starting from msb 6 serial clock input input sck serial data read at rising edge. 8 serial chip select input cs serial initialization when low, valid at high. 9 high-voltage withstand output pin for segment; output is output pin for segment output pch open drain + pull-down resistance. s1 ~ s11 15 ~ 25 power supply pin 2 input v ee pull-down resistance connection for flp driver output. 27 high-voltage withstand output pin for grid; output is pch output pin for grid output open drain + pull-down resistance. g1 ~ g10 42 ~ 39, 37 ~ 32 high-voltage withstand s12 / g15 used to switch output between segment and grid; 26, output pin for segment / grid output output is pch open drain + pull-down resistance. s16 / g11 28 ~ 31 key data input pin data input pin for key scanning. input k1 ~ k4 10 ~ 13 general-purpose input pin; input data can be general-purpose input pin input transmitted serially to microcomputer. sw1 ~ sw4 1 ~ 4 serial data output output so serial data output starting from msb; output is nch open drain. 5 ~ electrical characteristics (unless otherwise noted, ta = 25?, v dd = 5v, v ss = 0v, v dd ?v ee = 35v) parameter symbol conditions i dd supply current 44-pin attachment, at 1000pf oscillation v in input threshold voltage pins 1 to 4, 6, 8, 9 to 13 i in input current pins 1 to 4, 6, 8, 9 to 13 f osc osc oscillation frequency 44-pin attachment, at 1000pf oscillation i o seg segment output current pins 15 to 26, 28 to 31, v o = v dd ? 2v * i o grd grid output current pins 26, 28 to 37, 39 to 42, v o = v dd ? 2v * i off leakage current when off pins 15 to 26, 28 to 37, v o = v dd ? v ee r d output pull-down resistance pins 15 to 26, 28 to 37 f max maximum operating frequency design guarantee value serial transmission ? t sh input data hold t ss input data setup t d output data delay t scyc input clock cycle t sw input clock "h" width min. 1.5 130 6 18 35 0.16 0.16 0.5 40 typ. 200 70 max. 5 3.5 10 300 10 140 1 0.3 60 unit ma v m a khz ma ma m a k w mhz m s m s m s m s % at minimum input clock cycle measurement circuit fig.1 fig.4 fig.2 fig.3 fig.2 fig.2 fig.2 fig.2 fig.3 * for the high voltage withstand output pins for the segment / grid of pins 26 and 28 to 31, when segment output is specified, se gment output current is output, and when grid output is specified, grid current is output.
4 standard ics BU2879AK measurement circuits 1000p osc v ee v dd v ss a fig.1 n = test pin n v v ee v ss v dd a fig.2 1000p osc g1 monitor v ee v dd v ss fig.3 v ee v dd v ss fig.4 electrical characteristic curves 3.8 3.7 3.6 3.5 3.4 3.3 3.2 ? 25 25 75 circuit current: i dd (ma) temperature: ta ( c) fig. 5 supply current temperature characteristics 54 50 46 42 38 34 30 ? 25 25 75 ??grid output current: i oh grd (ma) temperature: ta ( c) fig. 6 ??grid output current temperature characteristics 16 15 14 13 12 11 10 ? 25 25 75 output current: i oh seg (ma) ??segment temperature: ta ( c) fig.7 ??segment output current temperature characteristics
5 standard ics BU2879AK external dimensions (units: mm) 0.15 33 23 22 12 1 34 44 10.0 0.2 14.0 0.3 0.35 0.1 10.0 0.2 14.0 0.3 1.2 0.05 2.15 0.1 0.15 0.1 0.8 11 qfp44
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