TC826 TELCOM | Alldatasheet
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3-171TELCOM SEMICONDUCTOR, INC. TC826 A/D CONVERTER WITH BAR GRAPH DISPLAY OUTPUT
FEATURES
n 2.5% Resolution n Direct LCD Display Drive n ‘Thermometer’ Bar or Dot Display n 40 Data Segments Plus Zero n Overrange Plus Polarity Indication n Differential Analog Input n Display Flashes on Overrange n Display Hold Mode n Auto–Zero Cycle Eliminates Zero Adjust Potentiometer n 9V Battery Operation n 20mV to 2.0 V Full–Scale Operation n Non–Multiplexed LCD Drive for Maximum Viewing Angle GENERAL DESCRIPTION In many applications a graphical display is preferred over a digital display. Knowing a process or system oper- ates, for example, within design limits is more valuable than a direct system variable readout. A bar or moving dot display supplies information precisely without requiring further inter- pretation by the viewer. The TC826 is a complete analog–to–digital converter with direct liquid crystal (LCD) display drive. The 40 LCD data segments plus zero driver give a 2.5% resolution bar display. Full–scale differential input voltage range extends from 20mV to 2V. The TC826 sensitivity is 500µv. A low drift 35 ppm/°C internal reference, LCD backplane oscillator and driver, input polarity LCD driver, and overrange LCD driver make designs simple and low cost. The CMOS design required only 125µA from a 9V battery. In +5V systems a TC7660 DC to DC converter can supply the –5V supply. The differential analog input leakage is a low 10pA. Two display formats are possible. The BAR mode display is like a ‘thermometer’ scale. The LCD segment driver that equals the input plus all below it are on. The DOT mode activates only the segment equal to the input. In either mode the polarity signal is active for negative input signals. An overrange input signal causes the display to flash and activates the overrange annunciator. A hold mode can be selected that freezes the display and prevents updating. The dual slope integrating conversion method with auto–zero phase maximizes noise immunity and eliminates zero–scale adjustment potentiometers. Zero–scale drift is a low 5 µV/°C. Conversion rate is typically 5 per second and is adjustable by a single external resistor. A compact, 0.5" square, flat package minimizes PC board area. The high pin count LSI package makes multi- plexed LCD displays unnecessary. Low cost, direct drive LCD displays offer the widest viewing angle and are readily available. A standard display is available now for TC826 prototyping work. PIN CONFIGURATION
ORDERING INFORMATION
Part No. Package Temperature TC826CBU 64–Pin PFP 0 °C to +70°C TC826-6 11/6/96 302928 5051 BAR 35 BAR 36 BAR 37 BAR 38 BAR 39 BAR 40 OR POL – BAR/DOT HOLD TEST 626364 49 BAR 15 NC BAR 34 4 45 BAR 30 BAR 14 BAR 13 BAR 12 BAR 11 BAR 10 BAR 9 BAR 8 BAR 7 BAR 6 BAR 5 BAR 4 BAR 3 BAR 2 BAR 1 BAR 29 BAR 28 BAR 27 BAR 26 BAR 25 BAR 24 BAR 23 BAR 22 BAR 21 BAR 20 BAR 19 BAR 18 NC OSC1 BP ANALOG COMMON +IN – IN REF IN VDD VSS OSC2 BAR 0 C + REF C – REF VBUF C AZ VINT NC NC BAR 17 BAR 16 BAR 32 BAR 33 BAR 31 TC826CBU
3-172 TELCOM SEMICONDUCTOR, INC. ABSOLUTE MAXIMUM RATINGS* Power Dissipation (TA ≤ 70°C) Operating Temperature *Static-sensitive device. Unused devices must be stored in conductive material. Protect devices from static discharge and static fields. Stresses above those listed under Absolute Maximum Ratings may cause perma- nent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to Absolute Maximum Rating Conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS: unless otherwise stated VS = 9V; ROSC = 430 kΩ ; TA = 25°C; Full–Scale = 20 mV. No. Symbol Parameter Test Conditions Min Typ Max Unit 1 — Zero Input V IN = 0.0V – 0 ±0 +0 Display 2 — Zero Reading Drift V IN = 0.0V — 0.2 1 µV/°C 0°C ≤ TA ≤ +70°C 3 NL Linearity Error Max Deviation From – 1 0.5 +1 Count Best Straight Line
4 R/O Rollover Error –V IN = +VIN – 1 0 +1 Count
5 EN Noise V IN = 0V — 60 — µVP–P
6 ILK Input Leakage Current V IN = 0V — 10 20 pA
7 CMRR Common–Mode VCM = ±1V — 50 — µV/V
Rejection Ratio V IN = 0V 8 — Scale Factor 0 ≤ TA ≤ +70°C — 1 — ppm/ °C Temperature Coefficient External Ref. Temperature Coefficient = 0 ppm/°C
9 VCTC Analog Common 250k Ω Between — 35 100 ppm/ °C
Temperature Coefficient Common and V + 0°C ≤ TA ≤ +70°C 10 V COM Analog Common 250k Ω Between 2.7 2.9 3.35 V Voltage Common and V DD
11 VSD LCD Segment 4 5 6 V P–P
12 VBD LCD Backplane 4 5 6 V P–P
13 I DD Power Supply Current — 125 175 µA
NOTES: 1. Input voltages may exceed the supply voltages when the input current is limited to 100µA. 2. Static sensitive device. Unused devices should be stored in conductive material to protect devices from static discharge and static fields. 3. Backplane drive is in phase with segment drive for ‘off’ segment and 180°C out of phase for ‘on’ segment. Frequency is 10 times conversion rate. 4. Logic input pins 58, 59, and 60 should be connected through 1MΩ series resistors to VSS for logic 0. TC826 A/D CONVERTER WITH BAR GRAPH DISPLAY OUTPUT
3-173TELCOM SEMICONDUCTOR, INC. TC826 A/D CONVERTER WITH BAR GRAPH DISPLAY OUTPUT PIN DESCRIPTION Pin No. (64-Plastic Quad Flat Package) Symbol Description 1N C 2 ANALOG Establishes the internal analog ground point. Analog common is set to 2.9V below the positive supply COMMON by an internal zener reference circuit. The voltage difference beween VDD and analog-common can be used to supply the TC826 voltage reference input at REF IN (Pin 5). 3 +IN Positive analog signal input. 4 -IN Negative analog signal input. 5 REF IN Reference voltage positive input. Measured relative ato analog-common. REF IN ≈ Full-Scale/2. 6 CREF + Reference capacitor connection. 7 CREF – Reference capacitor connection. 8V DD Positive supply terminal. 9V BUF Buffer output. Integration resistor connection. 10 C AZ Negative comparator input. Auto-zero capacitor connection. 11 V INT Integrator output. Integration capacitor connection. 12 V SS Negative supply terminal. 13 OSC1 Oscillator resistor (ROSC) connection. 14 OSC2 Oscillator resistor (ROSC) connection. 15 BP LCD Backplane driver.
16 BAR 0 LCD Segment driver: Bar 0
18 BAR 1 LCD Segment driver: Bar 1
19 BAR 2 LCD Segment driver: Bar 2
20 BAR 3 LCD Segment driver: Bar 3
21 BAR 4 LCD Segment driver: Bar 4
22 BAR 5 LCD Segment driver: Bar 5
23 BAR 6 LCD Segment driver: Bar 6
24 BAR 7 LCD Segment driver: Bar 7
25 BAR 8 LCD Segment driver: Bar 8
26 BAR 9 LCD Segment driver: Bar 9
27 BAR 10 LCD Segment driver: Bar 10
28 BAR 11 LCD Segment driver: Bar 11
29 BAR 12 LCD Segment driver: Bar 12
30 BAR 13 LCD Segment driver: Bar 13
31 BAR 14 LCD Segment driver: Bar 14
32 BAR 15 LCD Segment driver: Bar 15
33 BAR 16 LCD Segment driver: Bar 16
34 BAR 17 LCD Segment driver: Bar 17
35 BAR 18 LCD Segment driver: Bar 18
36 BAR 19 LCD Segment driver: Bar 19
37 BAR 20 LCD Segment driver: Bar 20
38 BAR 21 LCD Segment driver: Bar 21
39 BAR 22 LCD Segment driver: Bar 22
40 BAR 23 LCD Segment driver: Bar 23
3-174 TELCOM SEMICONDUCTOR, INC. TC826 A/D CONVERTER WITH BAR GRAPH DISPLAY OUTPUT PIN DESCRIPTION (Cont.) Pin No. (64-Plastic Quad Flat Package) Symbol Description
41 BAR 24 LCD Segment driver: Bar 24
42 BAR 25 LCD Segment driver: Bar 25
43 BAR 26 LCD Segment driver: Bar 26
44 BAR 27 LCD Segment driver: Bar 27
45 BAR 28 LCD Segment driver: Bar 28
46 BAR 29 LCD Segment driver: Bar 29
47 BAR 30 LCD Segment driver: Bar 30
49 BAR 31 LCD Segment driver: Bar 31
50 BAR 32 LCD Segment driver: Bar 32
51 BAR 33 LCD Segment driver: Bar 33
52 BAR 34 LCD Segment driver: Bar 34
53 BAR 35 LCD Segment driver: Bar 35
54 BAR 36 LCD Segment driver: Bar 36
55 BAR 37 LCD Segment driver: Bar 37
56 BAR 38 LCD Segment driver: Bar 38
57 BAR 39 LCD Segment driver: Bar 39
58 BAR 40 LCD Segment driver: Bar 40
59 OR LCD segment driver that indicated input out–of–range condition. 60 POL– LCD segment driver that indicates input signal is negative. 61 Input logic signal that selects bar or dot display format. Normally in bar mode. Connect to VSS through 1M Ω resistor for Dot format. 62 Input logic signal that prevents display from changing. Pulled high internally to inactive state. Connect to VSS through 1MΩ series resistor for HOLD mode operation. 63 Input logic signal. Sets TC826 to BAR display mode. BAR 0 to 40, plus OR flash on and off. The POL– LCD driver is on. Pulled high internally to inactive state. Connect to VSS with 1 MΩ series resistor to activate. 64 NC
3-175TELCOM SEMICONDUCTOR, INC.
41 SEGMENT
Figure 1. Typical TC826 Circuit Connection
3-177TELCOM SEMICONDUCTOR, INC. Figure 4. TC826 Analog Section (internal analog ground) to establish a zero input condition. lished on CAZ compensates for device offset voltages. The auto-zero cycle length is 19 counts minimum.
3-178 TELCOM SEMICONDUCTOR, INC. The final phase is reference integrate or deintegrate. independent of input signal magnitude.
- Auto-Zero Phase: 19 to 59 Counts For signals less than full-scale the auto-zero is as- signed the unused reference integrate time period.
- Signal Integrate: 20 Counts This time period is fixed. The integration period is: Where F OSC is the externally set clock frequency.
- Reference Integrate: 0 to 41 Counts Reference Voltage Selection A full-scale reading requires the input signal be twice the reference voltage. The reference potential is measured between REF IN (Pin 5) and ANALOG COMMON Pin 2). Required Full-Scale Voltage V REF 20mV 10mV 2V 1V INTERNAL SYSTEM CLOCK (FSYS) AUTO–ZERO PHASE (AZ) SIGNAL INTEGRATE PHASE (SI) REFERENCE INTEGRATE PHASE (RI) (DEINTEGRATE) INTEGRATOR OUTPUT INTERNAL DATA LATCH UPDATE SIGNAL
19 COUNTS
41 COUNTS
Figure 5. TC826 Conversion Has Three Phases
3-179TELCOM SEMICONDUCTOR, INC. values from 0.14µF to 0.068 µF are satisfactory. such as polypropylene are recommended. full-scale input conditions are given in Table 1. NOTES: Approximately 5 conversions/second. voltage range (VCM). The typical range is V+ –1 to V– +1V. DD or VSS without increased linearity error. input signal. Adjust for proper LCD display readout. Figure 6. External Reference S+ or VS– without saturating. pylene capacitors are suggested.
3-181TELCOM SEMICONDUCTOR, INC. Figure 10. Display Option Formats displayed with BAR 0 to BAR 20 on.
13 OSCILLATOR POWER
Figure 9. External Oscillator Connection (Figure 10). The BAR/DOT input (Pin 61) selects the format.
3-182 TELCOM SEMICONDUCTOR, INC. dard TC826 LCD display is available from Varitronix.
- Part No.: VBG-413-DP Other standard LCD displays suitable for development work are available in both linear and circular formats. One manufacturer is: UCE Inc.
24 Fitch Street
- Part No. 5040: 50 segment circular display with 3 digit numeric scale.
- Part No. 5020: 50 segment linear display. LCD BACKPLANE DRIVER (PIN 15) Additional drive electronics is not required to interface the TC826 to an LCD display. The TC826 has an on-chip backplane generator and driver. The backplane frequency is: FBP = FOSC/256 Figure 11 gives typical backplane driver rise/fall time versus backplane capacitance. 0 123456780 1 0 BACKPLANE CAPACITANCE (X 100pf) RISE/FALL TIME (X 100ns) TA = 25°C VS = 9V
Figure 11. Backplane Driver Rise/Fall Time vs. Capacitance