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TC826 Datasheet(PDF) 10 Page - TelCom Semiconductor, Inc |
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TC826 Datasheet(HTML) 10 Page - TelCom Semiconductor, Inc |
10 / 12 page 3-180 TELCOM SEMICONDUCTOR, INC. TC826 A/D CONVERTER WITH BAR GRAPH DISPLAY OUTPUT voltage across each LCD segment. This insures long LCD display life. The polarity segment drive, –POL, is ‘ON’ for negative analog inputs. If +IN and –IN are reversed this indicator would reverse. The TC826 transfer function is shown in Figure 7. 40 39 2 1 0 –1 –2 1 2 3 39 39.5 40 40.5 –0.5 0.5 OVERRANGE INDICATION ANALOG INPUT (X VFS 40 ) Figure 7. TC826 Transfer Function BAR/DOT Input (Pin 61) The BAR/DOT input allows the user to select the display format. The TC826 powers up in the BAR mode. Select the DOT display format by connecting BAR/DOT to the negative supply (Pin 12) through a 1M Ω resistor. HOLD Input (Pin 62) The TC826 data ouput latches are not updated at the end of each conversion if HOLD is tied to the negative supply (Pin 12) through a 1 M Ωresistor.TheLCDdisplaycontinously displays the previous conversion results. The HOLD pin is normally pulled high by an internal pull- up. TEST Input (Pin 63) The TC826 enters a test mode with the TEST input connected to the negative supply (Pin 12). The connection must be made through a 1M Ω resistor. The TEST input is normally internally pulled high. A low input sets the output data latch to all ones. The BAR display mode is set. The 41 LCD output segments (zero plus 40 data segments) and overrange annuniciator flash on and off at 1/4 the conversion rate. The polarity annunciator (POL–) segment will be on but not flashing Overrange Display Operation (OR, Pin 59) An out–of–range input signal will be indicated on the LCD display by the OR annunciator driver (Pin 59) becoming active. In the BAR display format the 41 bar segments and the overrange annunciator, OR, will flash ON and OFF. The flash rate is on fourth the conversion rate (FOSC/2560). In the DOT display mode, OR flashes and all other data segment drivers are off. Polarity Indication (POL– Pin 60) The TC826 converts and displays data for positive and negative input signals. The POL– LCD segment driver (Pin 60) is active for negative signals. Oscillator Operation The TC826 external oscillator frequency, FOSC, is set by resistor ROSC connected between pins 13 and 14. The oscillator frequency versus resistance curve is shown in Figure 8. 20 18 16 14 12 10 8 6 4 2 0 50 40 30 20 10 0 0 2468 10 12 14 16 18 20 TA = 25°C VDDTO VSS= 9V ROSC (X 100kΩ) Figure 8. Oscillator Frequency vs. ROSC FOSC is divided by 32 to provide an internal system clock, FYSY. Each conversion requires 80 internal clock cycles. The internal system clock is divided by 8 to provide the LCD backplane drive frequency. The display flash rate during an input out-of-range signal is set by dividing FSYS by 320. The internal oscillator may be bypassed by driving OSCI (Pin 13) with an external signal generator. OSC2 (Pin 14) should be left unconnected. The oscillator should swing from VDD to VSS in single supply operation (Figure 9). In dual supply operation the signal should swing from power supply ground to VDD. |
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Similar Description - TC826 |
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