shangh ai belling corp., ltd BL55028 zip: 200233 tel: 86-021-64850700 fax: 86-021-64855865 1 lcd driver for 76 display units BL55028 1 general description the BL55028 is a general lcd driver ic for 76 units lcd panel. it features a wide operating supply voltage range, incorporates simple communication interface with microcomputer and is suitable for multiple applicat ion. 2 features advanced low power cmos technology selection of 1/2 or 1/3 bias, selection of 1/2 or 1 /3 or 1/4 duty. operation voltage: 2.5~5.5v serial data interface 76(19x4) display units low power dissipation design: power saving mode: i dd=14ua at 5v and idd=9ua at 3.3v; on-chip rc oscillator vlcd for adjusting lcd operating voltage excellent emc immunity compatible with general microcomputer sop28 package 3 pin assignment fig 1 s18 sda scl vdd vss vlcd bp0 bp2 bp1 bp3 s0 s1 s2 s3 s17 s16 s15 s14 s13 s12 s11 s10 s9 s8 s7 s6 s5 s4 12 3 4 56 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15
shangh ai belling corp., ltd BL55028 zip: 200233 tel: 86-021-64850700 fax: 86-021-64855865 2 4 pin description pin no. pin name function 2 sda serial data input/output 3 sci serial clock input 4 vdd supply voltage 5 vss ground 6 vlcd lcd supply voltage 7-10 com0 com2 com1 com3 common terminal driving output 11-28 1 s0 s18 segment terminal driving output tab.1 5 function description 1.function circuit the bl550028 has all function circuits that can dir ectly drive any static or multiplexed lcd containing up to four commons and up to 19 segm ents. the function circuits include:power-on reset, lcd bias generator, lcd vol tage selector, oscillator, display ram, timing, display latch, shift register, common/segme nt outputs, input/output bank selector, blinker, data pointer, etc. 2.display function decription the display ram is a static 19x 4-bit ram which sto res lcd data. a logic 1 in the ram bit-map indicates the on state of the correspon ding lcd segment; similarly, a logic 0 indicates the off state. there is a one-to-one corr espondence between the ram addresses and the segment outputs, and between the individual bit s of a ram word and the common outputs. (see fig.2). display ram address and segment s0~s18 output 0 1 2 3 15 16 17 18 0 1 2 com (com0~ com3) 3 fig2 when display data is transmitted to the bl550 28, the display bytes received are stored in the display ram in accordance with the selected lcd drive mode. to illustrate the filling order, an example of a 7-segment numeric display sh owing all drive modes is given in fig.3; the ram filling organization depicted applies equal ly to other lcd types.
shangh ai belling corp., ltd BL55028 zip: 200233 tel: 86-021-64850700 fax: 86-021-64855865 3 fig 3 3. i 2 c-bus protocol i 2 c-bus slave addresses (0111110) are reserved for th e BL55028 the i2c-bus protocol is shown in fig.4. the se quence is initiated with a start condition (s) from the i2c-bus master which is foll owed by the BL55028 slave addresses available. after acknowledgement, one or more comma nd bytes (m) follow which define the status of the addressed BL55028. the last command b yte is tagged with a cleared most significant bit, the continuation bit c. the comman d bytes are also acknowledged by the addressed BL55028 on the bus. after the last comman d byte, a series of display data bytes(n) may follow. these display bytes are stored in the d isplay ram at the address specified by the data pointer. data pointer are automatically update d and the data is directed to the intended BL55028 device. after the last display byte, the i2 c-bus master issues a stop condition (p).
shangh ai belling corp., ltd BL55028 zip: 200233 tel: 86-021-64850700 fax: 86-021-64855865 4 fig 4 4. command decoder the command decoder identifies command bytes that a rrive on the i 2 c-bus. all available commands carry a continuation bit c in th eir most significant bit position. the four commands available to the BL55028 are defined in fi g 5. fig 5
shangh ai belling corp., ltd BL55028 zip: 200233 tel: 86-021-64850700 fax: 86-021-64855865 5 6 absolute maximum rating parameter symbol rating unit supply voltage vdd -0.5 +6.0 v lcd operating voltage vlcd 0 vdd v input voltage vi vss-0.5 vdd+0.5 v output voltage vo vlcd-0.5 vdd+0.5 v vdd,vss,vlcd current idd,iss,ilcd -50 +50 ma maximum power consumption ptot 400 mw operating temperature topr -40 +75 o c storage temperature tstg -65 +150 o c 7 dc characteristic symbol parameter test condition min typ max unit vdd ic operating voltage 2.5 - 5.5 v vlcd lcd operating voltage 0 - vdd-2 v idd1 supply current vdd=5v,vlcd=0v,normal mode,internal oscillator - 25 50 ua idd2 supply current vdd=5v,vlcd=0v,power saving mode,internal oscillator - 14 30 ua idd3 supply current vdd=3.3v,vlcd=0v,normal mode,internal oscillator - 16 30 ua idd4 supply current vdd=3.3v,vlcd=0v,power saving mode,internal oscillator - 9 15 ua vil low voltage input sda,scl vss - 0.3vdd v vih high voltage input sda,scl 0.7vdd - 6.0 v 8 ac characteristic ta=25 o c symbol parameter test condition min typ max unit fclk oscillator frequency vdd=5v,normal mode 125 180 300 khz fclk oscillator frequency vdd=3.3v, power saving mode 21 31 48 khz tclk half oscillator cycle 1 - 3 ua tsh1 cs start hold time 5 - us tsh2 scl start hold time 5 - us tlow high time 5 - us thig low time 4 - us thd scl hold time 250 ns
shangh ai belling corp., ltd BL55028 zip: 200233 tel: 86-021-64850700 fax: 86-021-64855865 6 fig 6 9 typical application circuit no te: 1/ when i 2 c are idle mode,sda and scl must be connect to high level(by pull up resistor),otherwise the device maybe can no t go into power saving mode. 2/ in power-saving mode, scl frequency must be l ess than 21khz. 3/ work at 1/3 bias, vdd C vlcd must be more than 2.9v fig 7
shangh ai belling corp., ltd BL55028 zip: 200233 tel: 86-021-64850700 fax: 86-021-64855865 7 10 package outline sop28 unit: inches (mm) fig 8
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