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ver 4.0 1 LD1970 16 segment x 12 grid vfd driver with key scan LD1970 16 segment x 12 grid vfd driver with keyscan ver. 4 .0 / dec. 20 12 this document is a general product description and is subject to change without notice. ldt inc. does not assume any responsibility for use of circuits described.
ver 4.0 2 LD1970 16 segment x 12 grid vfd driver with key scan description LD1970 is a vacuum fluorescent display (vfd) controller driven on a 1/4 to 1/12 duty factor. 16 segment output lines, 4 grid output lines, 8 segment/grid output drive lines, one display memory, control circuit and key scan circuit are all incorporated into a single chip to build a highly reliable peripheral device for a single chip micro computer. serial data is fed to LD1970 via a three - line serial interface. it is housed in a 48qfn, 44lqfp & 44mqfp package. features ? cmos technology ? low power consumption ? key scanning (16x2) matrix ? multiple display modes (16 segments, 12 digits to 24 segments, 4 digits) ? 8 - step dimming circuitry ? led ports provide (4 channels, 20ma max.) ? serial interface for clock, data input, data output, strobe pins ? no external resistors needed for driver outputs ? available in 48 qfn , 44lqfp, 44mqfp device name package type LD1970 48 qfn, 44lqfp, 44mqfp device name LD1970 package type 48 qfn (include 4nc), 44lqfp, 44mqfp power / ground vdd1, vdd2, vee / vss(2) di / do / aio di:3 ea, do:1ea, aio:1ea fip output 34 ea (led1~4, k1,k2,sg1~24, gr1~4) applications ? microcomputer peripheral devices ? digital audio/video system : cd/md/vcd/dvd players ? car audio ? vcr ? electric scale meter ? p.o.s ? electronic equipment with instructional display ordering information device name segment grid key scanning pkg type LD1970 - qfn 16~ 24 segment 12~4grid 16x2 matrix 48qfn LD1970 - lqfp 16~24 segment 12~4grid 16x2 matrix 44lqfp LD1970 - mqfp 16~24 segment 12~4grid 16x2 matrix 44mqfp
ver 4.0 3 LD1970 16 segment x 12 grid vfd driver with key scan pin description pin name type description pin no. qfn lqfp,mqfp led1 ~ led4 o led output pin 1~4 1~4 osc i/o oscillator i/o pin a resistor is connected to this pin to determine the oscillation frequency. 5 5 dout o data output pin (n - channel, open - drain) this pin outputs serial data at the falling edge of the shift clock (starting from the lower bit) 7 6 din (schmitt trigger) i data input pin this pin inputs serial data at the rising edge of the shift clock (starting from the lower bit) 8 7 clk (schmitt trigger) i clock input pin this pin reads serial data at the rising edge and outputs data at the falling edge of the shift clock 9 8 stb (schmitt trigger) i serial interface strobe pin the data input after the stb has fallen is processed as a command. when this pin is high, clk is ignored. 10 9 k1, k2 i key data input pins the data inputted to these pins is latched at the end of the display cycle. 11,12 10,11 vss g logic ground pin 13,48 12,44 vdd1, vdd2 p(+) logic positive power pin 47,14 43, 13 sg1/ks1 ~ sg16/ks16 o high - voltage segment output pins, also acts as the key source. 15~32 14~29 vee p( - ) pull - down level / negative power pin 33 30 sg17/gr12 ~ sg24/gr5 o high - voltage segment/grid output pins 34~41 31~38 gr1~gr4 o high - voltage grid output pins 43~46 39~42
ver 4.0 4 LD1970 16 segment x 12 grid vfd driver with key scan block diagram l e d 1 k 2 k 1 s t b c l k d i n d o u t o s c l e d 4 l e d 3 l e d 2 v d d 2 s g 1 9 / g r 1 0 v e e s g 1 7 / g r 1 2 s g 1 8 / g r 1 1 v s s s g 2 2 / g r 7 s g 2 3 / g r 6 s g 2 4 / g r 5 g r 4 g r 3 g r 2 g r 1 v d d 1 s e g m e n t d r i v e r g r i d d r i v e r k e y s c a n o u t p u t c o n t r o l l e d d r i v e r g r i d d r i v e r o s c p o r s g 9 / k s 9 s g 8 / k s 8 s g 7 / k s 7 s g 6 / k s 6 s g 5 / k s 5 s g 4 / k s 4 s g 3 / k s 3 s g 2 / k s 2 s g 1 / k s 1 s g 1 0 / k s 1 0 s g 1 1 / k s 1 1 s g 1 2 / k s 1 2 s g 1 3 / k s 1 3 s g 1 4 / k s 1 4 s g 1 5 / k s 1 5 s g 1 6 / k s 1 6 s g 2 0 / g r 9 s g 2 1 / g r 8
ver 4.0 5 LD1970 16 segment x 12 grid vfd driver with key scan pin configuration 48 qfn l d 1 9 7 0 [ 4 8 q f n ] 1 1 2 1 1 1 0 9 8 7 6 5 4 3 2 3 6 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2 3 3 3 4 3 5 1 3 2 4 2 3 2 2 2 1 2 0 1 9 1 8 1 7 1 6 1 5 1 4 4 8 3 7 3 8 3 9 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 l e d 1 k 2 k 1 s t b c l k d i n d o u t n c o s c l e d 4 l e d 3 l e d 2 v s s s g 9 / k s 9 s g 8 / k s 8 s g 7 / k s 7 s g 6 / k s 6 s g 5 / k s 5 s g 4 / k s 4 n c s g 3 / k s 3 s g 2 / k s 2 s g 1 / k s 1 v d d 2 s g 1 9 / g r 1 0 s g 1 0 / k s 1 0 s g 1 1 / k s 1 1 s g 1 2 / k s 1 2 s g 1 3 / k s 1 3 s g 1 4 / k s 1 4 n c s g 1 5 / k s 1 5 s g 1 6 / k s 1 6 v e e s g 1 7 / g r 1 2 s g 1 8 / g r 1 1 v s s s g 2 0 / g r 9 s g 2 1 / g r 8 s g 2 2 / g r 7 s g 2 3 / g r 6 s g 2 4 / g r 5 n c g r 4 g r 3 g r 2 g r 1 v d d 1 g r i d p o w e r l o g i c p o w e r
ver 4.0 6 LD1970 16 segment x 12 grid vfd driver with key scan LD1970 [44lqfp/44mqfp] pin configuration 44 lqfp & 44mqfp vdd2 vdd1
ver 4.0 7 LD1970 16 segment x 12 grid vfd driver with key scan i/o pins schematic diagram i n p u t p i n s : c l k , s t b , d i n i n p u t p i n s : k 1 , k 2 v d d v d d v d d v d d v e e o u t p u t p i n : d o u t o u t p u t p i n s : s g n , g r n o u t p u t p i n s : l e d 1 ~ l e d 4 v d d
ver 4.0 8 LD1970 16 segment x 12 grid vfd driver with key scan absolute maximum ratings (unless otherwise stated, ta=25 c, gnd=0v) parameters symbol ratings unit logic supply voltage vdd - 0.3 ~ +7.0 v driver supply voltage vee vdd+0.3 ~ vdd - 40 v logic input voltage vi - 0.3 ~ vdd+0.3 v vfd driver output voltage vo vee - 0.3 ~ vdd+0.3 v led driver output current ioled 20 ma vfd drive output current iovfd - 40 @ grid, - 15 @ segment ma operating temperature topr - 40 ~ 85 c storage temperature tstg - 65 ~ 150 c recommended operating range (unless otherwise stated, ta=25 c, gnd=0v) parameters symbol ratings unit min. typ. max. logic supply voltage vdd 3.0 5.0 5.5 v high - level input voltage vih 0.7*vdd - vdd v low - level input voltage vil 0 - 0.3*vdd v driver supply voltage vee vdd - 35 - 0 v
ver 4.0 9 LD1970 16 segment x 12 grid vfd driver with key scan electrical characteristics (unless otherwise stated, vdd=5.0v, gnd=0v, vee=vdd - 35v, ta=25 c) parameters symbol test conditions min. typ. max. unit high - level output voltage vohled iohled= - 12ma led1 ~ led4 vdd - 1 - - v low - level output voltage volled iohled=+15ma led1 ~ led4 - - 1 v low - level output voltage voldout ioldout=4ma dout - - 0.4 v high - level output current iohsg vo=vdd - 2v sg1/ks1~sg16/ks16 - 3 - - ma high - level output current iohgr vo=vdd - 2v gr1~gr4 sg17/gr12~sg24/gr5 - 15 - - ma oscillation frequency f osc r=82k 350 500 650 khz schmitt - trigger transfer voltage(+) vt+ vdd=5v din, clk, stb 2.7 3.0 3.3 v schmitt - trigger transfer voltage( - ) vt - vdd=5v din, clk, stb 0.7 1.0 1.3 v hysteresis voltage vhys vdd=5v din, clk, stb 1.4 2.0 - v input current ii vi=vdd or vss - - 1 ua dynamic current consumption idddyn under no load display off - - 5 ma
ver 4.0 10 LD1970 16 segment x 12 grid vfd driver with key scan electrical characteristics (unless otherwise stated, vdd=3.3v, gnd=0v, vee=vdd - 35v, ta=25 c) parameters symbol test conditions min. typ. max. unit high - level output voltage vohled iohled= - 6ma led1 ~ led4 vdd - 1 - - v low - level output voltage volled iohled=+15ma led1 ~ led4 - - 1 v low - level output voltage voldout ioldout=4ma dout - - 0.4 v high - level output current iohsg vo=vdd - 2v sg1/ks1~sg16/ks16 - 1.5 - - ma high - level output current iohgr vo=vdd - 2v gr1~gr4 sg17/gr12~sg24/gr5 - 6 - - ma oscillation frequency f osc r=82k 350 500 650 khz schmitt - trigger transfer voltage(+) vt+ vdd=3.3v din, clk, stb 1.8 2.0 2.2 v schmitt - trigger transfer voltage( - ) vt - vdd=3.3v din, clk, stb 0.2 0.4 0.6 v hysteresis voltage vhys vdd=3.3v din, clk, stb 1.0 1.6 - v input current ii vi=vdd or vss - - 1 ua dynamic current consumption idddyn under no load display off - - 3 ma
ver 4.0 11 LD1970 16 segment x 12 grid vfd driver with key scan switching characteristic waveform f osc = oscillation frequency pw stb (strobe pulse width) 1us pw clk (clock pulse width) 400ns t clk - stb (clock - strobe time) 1us tsetup (data setup time) 100ns thold (data hold time) 100ns t pzl (propagation delay time) 100ns t plz (propagation delay time) 400ns t thz (grid fall time) 150us t thz (segment fall time) 150us t tzh1 (segment rise time) < 2.0us(vdd=5.0v) t tzh2 (grid rise time) 0.5us(vdd=5.0v) t tzh1 (segment rise time) < 4.0us(vdd=3.3v) t tzh2 (grid rise time) 1.2us(vdd=3.3v) i n t e r n a l o s c s t b c l k d i n d o u t g r n s e g n f o s c p w s t b t c l k - s t b t p l z t p z l p w c l k p w c l k t s e t u p t h o l d 9 0 % 1 0 % 9 0 % 1 0 % t t h z t t z h 1 t t z h 2 t t h z
ver 4.0 12 LD1970 16 segment x 12 grid vfd driver with key scan functional description commands determine the display mode and status of LD1970. a command is the first byte (b0 to b7) inputted to LD1970 via the din pin after stb pin has changed from high to low state. if for some reason the stb pin is set to high while data or commands are being transmitted, the serial communication is initialized, and the data/commands being transmitted are considered invalid. commands command 1 : display mode setting command LD1970 provides 8 display mode settings as shown in the diagram below : as stated earlier a command is the first one byte(b0 to b7) transmitted to LD1970 via the din pin when stb pin is low. however, for this command, the bits 5 to 6 (b4 to b5) are ignored, bits 7 & 8 (b6 to b7) are given a value of 0. the display mode setting command determines the number of segments and grids to be used(1/4 to 1/12 duty, 16 to 24 segments). when this command is executed, the display is forcibly turned off, the key scanning stops. a display command on must be executed in order to resume display. if the same mode setting is selected, no command execution is taken place, therefore nothing happens. when power is turned on, the 12 - grid, 16 - segment mode is selected. 0 0 - - b3 b2 b1 b0 msb lsb 00 : command1 dont care display mode settings 0000 : 4grid, 24segment 0001 : 5grid, 23segment 0010 : 6grid, 22segment 0011 : 7grid, 21segment 0100 : 8grid, 20segment 0101 : 9grid, 19segment 0110 : 10grid, 18segment 0111 : 11grid, 17segment 1xxx : 12grid, 16segment
ver 4.0 13 LD1970 16 segment x 12 grid vfd driver with key scan data transmitted from an external device to LD1970 via the serial interface are stored in the display memory and are assigned addresses. the memory addresses of LD1970 are given below in the 8bits unit. display mode and memory address 00h l 00h h 01h l 01h h 02h l 02h h 03h l 03h h 04h l 04h h 05h l 05h h 06h l 06h h 07h l 07h h 08h l 08h h 09h l 09h h 0ah l 0ah h 0bh l 0bh h 0ch l 0ch h 0dh l 0dh h 0eh l 0eh h 0fh l 0fh h 10h l 10h h 11h l 11h h 12h l 12h h 13h l 13h h 14h l 14h h 15h l 15h h 16h l 16h h 17h l 17h h 18h l 18h h 19h l 19h h 1ah l 1ah h 1bh l 1bh h 1ch l 1ch h 1dh l 1dh h 1eh l 1eh h 1fh l 1fh h 20h l 20h h 21h l 21h h 22h l 22h h 23h l 23h h b0 b3 xxh l xxh h b4 b7 lower 4bits higher 4bits grid1 grid2 grid3 grid4 grid5 grid6 grid7 grid8 grid9 grid10 grid11 grid12 sg1 sg4 sg5 sg8 sg9 sg12 sg13 sg16 sg17 sg20 sg21 sg24
ver 4.0 14 LD1970 16 segment x 12 grid vfd driver with key scan command 2 : data setting command the data setting command executes the data write or data read modes for LD1970. the data setting command, the bits 5 and 6 (b4, b5) are ignored, bit 7 (b6) is given the value of 1 while bit 8 (b7) is given the value of 0. please refer to the diagram below. when power is turned on, the bit 4 to bit1 (b3 to b0) are given the value of 0. 0 1 - - b3 b2 b1 b0 msb lsb 01 : command2 dont care data write mode setting 00 : write data to display mode 01 : write data to led port 10 : read key scan data 11 : dont care address increment mode settings (display mode) 0 : increment address after data has been written 1 : fixes address mode setting 0 : normal operation mode 1 : test mode (user dont use)
ver 4.0 15 LD1970 16 segment x 12 grid vfd driver with key scan LD1970 key matrix consists of 16 x 2 array as shown below. LD1970 key matrix & key input data storage memory sg1/ks1 sg2/ks2 sg3/ks3 sg4/ks4 sg5/ks5 sg6/ks6 sg7/ks7 sg8/ks8 sg9/ks9 sg10/ks10 sg11/ks11 sg12/ks12 sg13/ks13 sg14/ks14 sg15/ks15 sg16/ks16 k1 k2 k1 k2 k1 k2 k1 k2 reading sequence b0 b1 b2 b3 b4 b5 b6 b7 k1 k2 sg1/ks1 sg2/ks2 sg3/ks3 sg4/ks4 sg5/ks5 sg6/ks6 sg7/ks7 sg8/ks8 sg9/ks9 sg10/ks10 sg11/ks11 sg12/ks12 sg13/ks13 sg14/ks14 sg15/ks15 sg16/ks16 each data inputted by each key are stored as follows. they are read by a read command, starting from the least significant bit. when the most significant bit of the data (sg16, b7) has been read, the least significant bit if the next data (sg1, b0) is read.
ver 4.0 16 LD1970 16 segment x 12 grid vfd driver with key scan led display LD1970 provides 4 led display terminals, namely led1 to led4. data is written to the led port starting from the least significant bit (b0) of the port using a write command. each bit starting from the least significant (b0) activates a specific led display terminal C b0 corresponds led1 display,b1 activates led2 and so forth. since there are only 4 led display terminals, bit5 to bit8 (b4 ~ b7) are not used and therefore ignored. this means that b4 to b7 does not in anyway activate any led display and they are totally ignored. when a bit (b0 ~ b3) in the led port is 1, the corresponding led is off. conversely, when the bit is 0, the led display is turned on. for example, bit1 (as designated by b0) has the value of 1, then this means that led1 is off. it must be noted that when power is turned on, bit1 to bit4 (b0 to b3) are given the value of 0 (all leds are turned on). please refer to the diagram below. - - - - b3 b2 b1 b0 msb lsb dont care led1 led3 led4 led2
ver 4.0 17 LD1970 16 segment x 12 grid vfd driver with key scan command 3 : address setting command the display memory is addressed by address setting command. the valid address range is from 00h to 23h. if the address is set to 24h or higher, the data is ignored until a valid address is set. when the power is turned on, the address is set at 00h. please refer to the diagram below. 1 1 b5 b4 b3 b2 b1 b0 msb lsb 11 : command 3 address : 00h to 23h
ver 4.0 18 LD1970 16 segment x 12 grid vfd driver with key scan command 4 : display control command the display control command is used to turn on or off a display. it is also used to set the pulse width. please refer to the diagram below. when the power is turned on, a 1/16 pulse width is selected and the display is turned off (the key scanning is stopped). 1 0 - - b3 b2 b1 b0 msb lsb 10 : command 4 display setting 0 : display off (key scan continues) 1 : display on dont care dimming quantity setting : 000 : pulse width = 1/16 001 : pulse width = 2/16 010 : pulse width = 4/16 011 : pulse width = 10/16 100 : pulse width = 11/16 101 : pulse width = 12/16 110 : pulse width = 13/16 111 : pulse width = 14/16
ver 4.0 19 LD1970 16 segment x 12 grid vfd driver with key scan scanning and display timing the key scanning and display timing diagram is given below. one cycle of key scanning consists of 2 frames. the data of the 16 x 2 matrix is stored in the memory. g1 g2 g3 gn sgn tdisplay=500us 1frame = tdisplay x (n+1) note : tdisplay is the width of segment only key scan data
ver 4.0 20 LD1970 16 segment x 12 grid vfd driver with key scan serial communication format the following diagram shows the LD1970 serial communication format. the dout pin is an n - channel open drain output pin, therefore , it is highly recommended that an external pull - up resistor (1 ? ~ 10 ? ) must be connected to dout. clk din reception (data/command write) stb if data continues 1 2 3 7 8 clk din transmission (data read) stb b0 b1 b2 b3 b4 b5 b6 b7 b0 b1 b6 b7 b0 b1 b6 b7 dout twait data read command set data reading starts where : twait (waiting time) 1us it must be noted that when the data is read, the waiting time (twait) between the rising of the 8 th clock that has set the command and the falling of the 1 st clock that has the data is greater or equal to 1us.
ver 4.0 21 LD1970 16 segment x 12 grid vfd driver with key scan serial communication example serial communication timing diagram for initialization setting command2 command3 data1 data2 command1 command4 stb clk din where : command1 : display mode setting command2 : data setting command command3 : address setting command data1 to n : transfer display data (36 byte max.) command4 : display control command command2 command3 data command3 stb clk din data transmission diagram for new data on specific addresses. where : command2 : data setting command command3 : address setting command data : display data command2 data stb clk din transmission diagram for led data setting diagram. where : command2 : data setting command led data : 4 led (led1 to led4) display data
ver 4.0 22 LD1970 16 segment x 12 grid vfd driver with key scan recommended software programming flow chart note : 1. command1 : display mode setting 2. command2 : data setting command 3. command3 : address setting command 4. command4 : display control command 5. when ic power is applied for the first time, the contents of the display memory are not defined. thus, it is strongly suggested that the contents of the display memory must be cleared during the initial setting. start delay 200ms set command2 (write data) set command3 clear display memory (see note5) set command1 set command4 (88h ~ 8fh : display on) main program set command2 (read key & write data included) set command3 set command1 set command4 end initial setting main loop set test mode initial (command 4bh, parameter 00h)
ver 4.0 23 LD1970 16 segment x 12 grid vfd driver with key scan application circuit note : the capacitor(0.1uf) connected between the gnd and the vdd pins must be located as close as possible to the LD1970 chip. l d 1 9 7 0
ver 4.0 24 LD1970 16 segment x 12 grid vfd driver with key scan package information notes all dimensions refer to jedec standard mo - 220 (vjje) 48 qfn package (bode size : 6mm x 6mm; pitch : 0.4mm; thk body: 0.75mm) unit : mm
ver 4.0 25 LD1970 16 segment x 12 grid vfd driver with key scan 44 - pin lqfp package (bode size : 10mm x 10mm; pitch : 0.8mm; thk body: 1.40mm) unit : mm
ver 4.0 26 LD1970 16 segment x 12 grid vfd driver with key scan 44 - pin mqfp package (bode size : 10mm x 10mm; pitch : 0.8mm; thk body: 2.10mm) unit : mm

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