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HI-8050 Datasheet(PDF) 3 Page - Holt Integrated Circuits |
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HI-8050 Datasheet(HTML) 3 Page - Holt Integrated Circuits |
3 / 8 page HI-8050/51, HI-8150/51 FUNCTIONAL DESCRIPTION INPUT LOGIC BPOSC and BPIN The data is clocked intoa serial shift register from the DIN in- put on the negative edge of while is held low. LD is normally held low and pulsed high only when data from the shift register is parallel latched to the segment outputs. must be low when LD is pulsed. The latches are transparent while LD is high. A logic "1" in the shift register causes the corresponding segment output to be out of phase with the BP output. All four logic inputs are TTL compatible on the HI-8050/51and CMOS compatible on the HI-8150/51. The user has the option of creating the backplane frequency internally or providinga signal from an external source. For an internal oscillator, BPIN and BPOSC are connected to- gether and the appropriateR&C combination is applied as shown in Figure 1. The resulting backplane frequency is ap- proximately: f = 1 . (R= 220K , C= 220pF, f 100HZ) The value of the resistor must be greater than 30K . Alternatively, BPOSC is left open and an external backplane signal of the desired frequency is applied to the BPIN input. CL CS CS BP BP » Ω Ω VEE & NEGATIVE VOLTAGE CONVERTER VEE can be connected toa negative power supply. Alterna- tively, the HI-8050& HI-8150 have the option of generating the VEE voltage witha built-in -25 volt negative voltage con- verter (See Figure 2). When not used, the open CONVOSC pin is detected and all power consuming circuitry is dis- abled. The converter will survivea short between two seg- ments and stillmaintaina VEE voltage of -20V. DOUT The DOUT30, DOUT32, and DOUT38 pins are available for cascading devices to drive more segments (See Figure 3) and for verifying the integrity of the shift register data. The outputs can drive2 TTL loads. They change on the positive edge of . CL AUTOMATIC SEGMENTS OFF TEST INPUTS A threshold device detects when the 5V supply is below ap- proximately 1V and forces all the segments and the backplane to the same level. This feature is used to discharge the VEE capacitor when the 5V power is switched off, to prolong the life of the LCD display. The and inputs function the same as the HI-8010 and HI-8110 product (See Figure 5) if this pin is left open or held high. If held low, the two pins function the same as the HI-8020 and HI-8120 product (See Figure 6). This input is available only on the HI-8050 (TTL) and HI-8150 (CMOS) products. The test functions available are: 0 0 Normal 01 All Off 10 All On 1 1 Alternating On/Off Segments The test inputs must be tied to the appropriate logic level for correct circuit operation. Both test inputs are TTL compatible on the HI-8050/51 and CMOS compatible on the HI-8150/51. 8020OPT CL CS T2 T1 Display ode M 256 RC Figure 2. OPTIONAL VOLTAGE CONVERTER CONVOSC CONVOUT VEE Control OSC VDD 68K Ω IN5818, IN5819 330µH 10µF VDD VSS VSS SENSE R Figure 1. INTERNAL OSCILLATOR CIRCUIT BPIN TO BACKPLANE TRANSLATOR AND DRIVER ÷ 256 R C VSS BPOSC C R Q VDD HOLT INTEGRATED CIRCUITS 3 |
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