View TC7106_2437.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

TC7106 TC7106A TC7107 TC7107A 3-1/2 DIGIT A/D CONVERTERS
FEATURES
s Internal Reference with Low Temperature Drift TC7106/7 ....................................... 80ppm/C Typical TC7106A/7A .................................. 20ppm/C Typical s Drives LCD (TC7106) or LED (TC7107) Display Directly s Guaranteed Zero Reading With Zero Input s Low Noise for Stable Display s Auto-Zero Cycle Eliminates Need for Zero Adjustment s True Polarity Indication for Precision Null Applications s Convenient 9 V Battery Operation (TC7106A) s High Impedance CMOS Differential Inputs .... 1012 s Differential Reference Inputs Simplify Ratiometric Measurements s Low Power Operation ..................................... 10mW
1
GENERAL DESCRIPTION
The TC7106A and TC7107A 3-1/2 digit direct-display drive analog-to-digital converters allow existing 7106/7107 based systems to be upgraded. Each device has a precision reference with a 20ppm/C max temperature coefficient. This represents a 4 to 7 times improvement over similar 3-1/2 digit converters. Existing 7106 and 7107 based systems may be upgraded without changing external passive component values. The TC7107A drives common anode light emitting diode (LED) displays directly with 8mA per segment. A low-cost, high-resolution indicating meter requires only a display, four resistors, and four capacitors. The TC7106A low power drain and 9V battery operation make it suitable for portable applications. The TC7106A/TC7107A reduces linearity error to less than 1 count. Rollover error - the difference in readings for equal magnitude but opposite polarity input signals - is below 1 count. High impedance differential inputs offer 1pA leakage current and a 1012 input impedance. The differential reference input allows ratiometric measurements for ohms or bridge transducer measurements. The 15VP-P noise performance guarantees a "rock solid" reading. The auto-zero cycle guarantees a zero display reading with a zero-volts input.
2 3 4 5 6 7
ORDERING INFORMATION PART CODE TC710X X X XXX
6 = LCD 7 = LED
}
A or blank* R (reversed pins) or blank (CPL pkg only) * "A" parts have an improved reference TC Package Code (see below):
0.1F 34 33 C- LCD DISPLAY (TC7106/A) OR COMMON ANODE LED DISPLAY (TC7107/A) 2-19 22-25 POL BP V+ SEGMENT DRIVE 20 21 1 24k 28 V BUFF 47k 0.47F 29 CAZ VINT 39 MINUS SIGN BACKPLANE DRIVE
Package Code Package
CKW CLW CPL IPL IJL 44-Pin PQFP 44-Pin PLCC 40-Pin PDIP 40-Pin PDIP 40-Pin CerDIP
Pin Layout
Formed Leads -- Normal Normal Normal
Temperature Range
0C to +70C 0C to +70C 0C to +70C - 25C to +85C - 25C to +85C
1M + ANALOG INPUT - 0.01F
31
+ C REF V+
IN
REF
30 32
- V IN ANALOG COMMON
TC7106/A TC7107/A
+ VREF 1k 9V
36 V+ REF
AVAILABLE PACKAGES
0.22F
35 100mV V- REF
- 26
27
V OSC2 OSC3 OSC1
38 COSC 40 R OSC 100pF 100k
TO ANALOG COMMON (PIN 32) 3 CONVERSIONS/SEC 200mV FULL SCALE
40-Pin Plastic DIP
40-Pin CERDIP
Figure 1. TC7106/A/7/A Typical Operating Circuit
44-Pin Plastic Quad Flat Package Formed Leads
44-Pin Plastic Chip Carrier PLCC
TC7106/6A/7/7A-7 11/4/96
8
3-183
TELCOM SEMICONDUCTOR, INC.
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
ABSOLUTE MAXIMUM RATINGS* TC7106A
Supply Voltage (V+ to V-) ........................................... 15 V Analog Input Voltage (either input) (Note 1) ......... V+ to V- Reference Input Voltage (either input) ................. V+ to V- Clock Input ........................................................ Test to V+ Package Power Dissipation (Note 2) (TA 70C) CerDIP ..............................................................2.29W Plastic DIP ........................................................1.23W PLCC ................................................................1.23W PQFP ................................................................1.00W Operating Temperature "C" Devices ............................................ 0C to +70C "I" Devices ........................................ - 25C to +85C Storage Temperature ............................ - 65C to +150C Lead Temperature (Soldering, 60 sec) ................... 300C Analog Input Voltage (either input) (Note 1) ......... V+ to V- Reference Input Voltage (either input) ................. V+ to V- Clock Input ....................................................... GND to V+ Power Dissipation (Note 2) (TA 70C) 40-Pin CerDIP Package ...................................2.29W 40-Pin Plastic DIP ............................................. 1.23W 44-Pin PLCC .....................................................1.23W 44-Pin PQFP .................................................... 1.00W Operating Temperature "C" Devices ............................................ 0C to +70C "I" Devices ........................................ - 25C to +85C Storage Temperature ............................ - 65C to +150C Lead Temperature (Soldering, 10 sec) ................. +300C
*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 permanent 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.
TC7107A
Supply Voltage V+ ................................................................................................ +6 V V- ............................................................................................... - 9 V
ELECTRICAL CHARACTERISTICS (Note 3)
Parameters
Zero Input Reading Ratiometric Reading Roll-Over Error (Difference in Reading for Equal Positive and Negative Reading Near Full-Scale) Linearity (Max. Deviation From Best Straight Line Fit) Common-Mode Rejection Ratio (Note 4) Noise (Pk - Pk Value Not Exceeded 95% of Time) Leakage Current @ Input Zero Reading Drift
Test Conditions
VIN = 0.0 V Full-Scale = 200.0mV VIN = VREF VREF = 100 mV - VIN = +V+ 200mV IN
TC7106/A & TC7107/A Min Typ Max
- 000.0 999 -1 000.0 999/1000 0.2 +000.0 1000 +1
Unit
Digital Reading Digital Reading Counts
Scale Factor Temperature Coefficient
Supply Current (Does Not Include LED Current For TC7107/A)
Full-Scale = 200mV or Full-Scale = 2.000 V VCM = 1V, VIN = 0V, Full Scale = 200.0 mV VIN = 0 V Full-Scale = 200.0mV VIN = 0 V VIN = 0 V "C" Device = 0C to +70C VIN = 0 V "I" Device = - 25C to +85C VIN = 199.0mV, "C" Device = 0C to +70C (Ext. Ref = 0ppmC) VIN = 199.0mV "I" Device = - 25C to +85C VIN = 0
-1 -- -- -- -- -- -- -- --
0.2 50 15 1 0.2 1.0 1 -- 0.8
+1 -- -- 10 1 2 5 20 1.8
Counts V/V V pA V/C V/C ppm/C ppm/C mA
3-184
TELCOM SEMICONDUCTOR, INC.
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
ELECTRICAL CHARACTERISTICS (Cont.) (Note 3)
Parameters
Analog Common Voltage (With Respect to Pos. Supply) Temp. Coeff. of Analog Common (With Respect to Pos. Supply) Temp. Coeff. of Analog Common (With Respect to Pos. Supply) TC7106A ONLY Pk - Pk Segment Drive Voltage (Note 5) TC7106A ONLY Pk - Pk Backplane Drive Voltage (Note 5) TC7107A ONLY Segment Sinking Current (Except Pin 19) TC7107A ONLY Segment Sinking Current (Pin 19)
1
Test Conditions
25k Between Common and Pos. Supply 25k Between Common and Pos. Supply 0C TA +70C ("C", Commercial Temp. Range Devices) 25k Between Common and Pos. Supply - 25C TA 85C ("I," Industrial Temp. Range Devices) V+ to V- = 9V V+ to V- = 9V V+ = 5.0V Segment Voltage = 3V V+ = 5.0V Segment Voltage = 3V
TC7106/A & TC7107/A Min Typ Max
2.7 3.05 3.35
Unit
V
2 3 4 5 6 7
7106A/7A 7106/7
20 80
50 --
ppm/C ppm/C
-- 4 4 5 10
-- 5 5 8.0 16
75 6 6 -- --
ppm/C V V mA mA
NOTES: 1. Input voltages may exceed the supply voltages provided the input current is limited to 100A. 2. Dissipation rating assumes device is mounted with all leads soldered to printed circuit board. 3. Unless otherwise noted, specifications apply to both the TC7106/A and TC7107/A at TA = 25C, fCLOCK = 48 kHz. Parts are tested in the circuit of Figure 1. 4. Refer to "Differential Input" discussion. 5. Backplane drive is in phase with segment drive for "OFF" segment, 180 out of phase for "ON" segment. Frequency is 20 times conversion rate. Average DC component is less than 50mV.
8
TELCOM SEMICONDUCTOR, INC.
3-185
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
PIN CONFIGURATIONS
V+ D1 C1 B1 1's A1 F1 G1 E1 D2
1 2 3 4 5 6 7 8 9
40 OSC 1 NORMAL PIN CONFIGURATION 39 OSC 2 38 OSC 3 37 TEST + 36 V REF - 35 VREF + 34 CREF - 33 CREF 32 ANALOG COMMON + 31 V IN 30 V - IN 29 CAZ 28 VBUFF 27 V INT 26 V - 25 G 2 24 C 3 23 A 3 22 G 3 21 BP/GND (7106A/7107A)
OSC 1 OSC 2 OSC 3
1 2 3
40 V + REVERSE PIN CONFIGURATION 39 D1 38 C1 37 B 1 36 A 1 35 F1 1's
C2 10 10's B 2 11 A 2 12 F2 13 E 2 14 D3 15 100's B 3 16 F3 17 E 3 18 1000's AB 4 19 POL 20 (MINUS SIGN)
TC7106ACPL TC7107AIPL
TEST 4 + V REF 5 - VREF 6 + CREF 7 - CREF 8 ANALOG 9 COMMON + V IN 10 V - 11 IN CAZ 12
34 G1 33 E 1 32 D2 31 C2
TC7106AIJL TC7107AIJL
30 B 2 29 A 2 28 F2
10's
VBUFF 13 V INT 14 V - 15 G 2 16
27 E 2 26 D3 25 B 3 24 F3
100's
100's
C 3 17 A 3 18 G 3 19
100's
23 E 3 22 AB 4 1000's 21 POL (MINUS SIGN)
BP/GND 20 (7106A/7107A)
REF LO
REF HI
REF HI
OSC1
OSC2
OSC3
CREF
CREF
IN LO
BUFF
TEST
COM
IN HI
INT 35
A/Z
NC
C1
D1
V+
A1
B1
6
5
4
3
2
1
44
43
42
41
40
44
43
42
41
40
39
38
37
36
F1 G1 E1 D2 C2 NC B2 A2 F2 E2 D3
7 8 9 10 11 12 13 14 15 16 17 TC7106ACLW TC7107ACLW (PLCC)
39 38 37 36 35 34 33 32 31 30 29
REF LO CREF CREF COMMON IN HI NC IN LO A/Z BUFF INT V-
NC NC TEST OSC3 NC OSC2 OSC1 V+ D1 C1 B1
1 2 3 4 5 6 7 8 9 10 11 TC7106ACKW TC7107ACKW (FLAT PACKAGE)
V- 34
33 32 31 30 29 28 27 26 25 24 23
NC G2 C3 A3 G3 BP/GND POL AB4 E3 F3 B3
18 B3
19 F3
20 E3
21 AB4
22 POL
23 NC
24 BP/GND
25 G3
26 A3
27 C3
28 G2
12 A1
13 F1
14 G1
15 E1
16 D2
17 C2
18 B2
19 A2
20 F2
21 E2
22 D3
3-186
TELCOM SEMICONDUCTOR, INC.
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
PIN DESCRIPTION
Pin No. 40-Pin PDIP (Normal)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
1
Pin No. 40-Pin PDIP (Reverse)
(40) (39) (38) (37) (36) (35) (34) (33) (32) (31) (30) (29) (28) (27) (26) (25) (24) (23) (22) (21) (20) (19) (18) (17) (16) (15) (14) (13) (12)
2
Symbol
V+ D1 C1 B1 A1 F1 G1 E1 D2 C2 B2 A2 F2 E2 D3 B3 F3 E3 AB4 POL BP GND G3 A3 C3 G2 V- VINT VBUFF CAZ
Description
Positive supply voltage. Activates the D section of the units display. Activates the C section of the units display. Activates the B section of the units display. Activates the A section of the units display. Activates the F section of the units display. Activates the G section of the units display. Activates the E section of the units display. Activates the D section of the tens display. Activates the C section of the tens display. Activates the B section of the tens display. Activates the A section of the tens display. Activates the F section of the tens display. Activates the E section of the tens display. Activates the D section of the hundreds display. Activates the B section of the hundreds display. Activates the F section of the hundreds display. Activates the E section of the hundreds display. Activates both halves of the 1 in the thousands display. Activates the negative polarity display. LCD Backplane drive output (TC7106A). Digital ground (TC7107A). Activates the G section of the hundreds display. Activates the A section of the hundreds display. Activates the C section of the hundreds display. Activates the G section of the tens display. Negative power supply voltage. Integrator output. Connection point for integration capacitor. See INTEGRATING CAPACITOR section for more details Integration resistor connection. Use a 47k resistor for a 200mV fullscale range and a 470k resistor for 2V full-scale range. The size of the auto-zero capacitor influences system noise. Use a 0.47F capacitor for 200mV full scale, and a 0.047F capacitor for 2V full scale. See Paragraph on AUTO-ZERO CAPACITOR for more details. The analog LOW input is connected to this pin. The analog HIGH input signal is connected to this pin. This pin is primarily used to set the analog common-mode voltage for battery operation or in systems where the input signal is referenced to the power supply. It also acts as a reference voltage source. See paragraph on ANALOG COMMON for more details. See pin 34.
3 4 5 6 7
30 31 32
(11) (10) (9)
V- IN V+ IN ANALOG COMMON
33
(8)
C- REF
8
TELCOM SEMICONDUCTOR, INC.
3-187
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
PIN DESCRIPTION (Cont.)
Pin No. Pin No. 40-Pin PDIP 40-Pin PDIP (Normal) (Reverse)
34 (7)
Symbol
+ C REF
Description
A 0.1F capacitor is used in most applications. If a large commonmode voltage exists (for example, the V - pin is not at analog IN common), and a 200mV scale is used, a 1F capacitor is recommended and will hold the roll-over error to 0.5 count. See pin 36. The analog input required to generate a full-scale output (1999 counts). Place 100mV between pins 35 and 36 for 199.9mV full-scale. Place 1V between pins 35 and 36 for 2V full scale. See paragraph on REFERENCE VOLTAGE. Lamp test. When pulled HIGH (to V+) all segments will be turned on and the display should read -1888. It may also be used as a negative supply for externally-generated decimal points. See paragraph under TEST for additional information. See pin 40. See pin 40. Pins 40, 39, 38 make up the oscillator section. For a 48kHz clock (3 readings per section), connect pin 40 to the junction of a 100k resistor and a 100pF capacitor. The 100k resistor is tied to pin 39 and the 100pF capacitor is tied to pin 38.
35 36
(6) (5)
- VREF + V REF
37
(4)
Test
38 39 40
(3) (2) (1)
OSC3 OSC2 OSC1
GENERAL THEORY OF OPERATION DUAL SLOPE CONVERSION PRINCIPLES
(All Pin Designations Refer to the 40-Pin DIP)
The TC7106A and TC7107A are dual slope, integrating analog-to-digital converters. An understanding of the dual slope conversion technique will aid in following the detailed operation theory. The conventional dual slope converter measurement cycle has two distinct phases: * Input Signal Integration * Reference Voltage Integration (Deintegration) The input signal being converted is integrated for a fixed time period (TSI). Time is measured by counting clock pulses. An opposite polarity constant reference voltage is then integrated until the integrator output voltage returns to zero. The reference integration time is directly proportional to the input signal (TRI). (Figure 2A). In a simple dual slope converter a complete conversion requires the integrator output to "ramp-up" and "rampdown." A simple mathematical equation relates the input signal, reference voltage and integration time: TSI VRTRI 1 VIN(t)dt = RC RC 0
where: VR = Reference Voltage TSI = Signal Integration Time (Fixed) TRI = Reference Voltage Integration Time (Variable) For a constant VIN: T VIN = VR RI TSI
C ANALOG INPUT SIGNAL INTEGRATOR - +/- SWITCH DRIVER REF VOLTAGE PHASE CONTROL CONTROL LOGIC POLARITY CONTROL CLOCK
INTEGRATOR OUTPUT
COMPARATOR -
DISPLAY VIN VIN VARIABLE REFERENCE INTEGRATE TIME
VFULL SCALE 1/2 VFULL SCALE
FIXED SIGNAL INTEGRATE TIME
Figure 2A. Basic Dual Slope Converter
3-188
TELCOM SEMICONDUCTOR, INC.
+ COUNTER
+
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
The dual slope converter accuracy is unrelated to the integrating resistor and capacitor values as long as they are stable during a measurement cycle. An inherent benefit is noise immunity. Noise spikes are integrated or averaged to zero during the integration periods. Integrating ADCs are immune to the large conversion errors that plague successive approximation converters in high-noise environments. Interfering signals with frequency components at multiples of the averaging period will be attenuated. Integrating ADCs commonly operate with the signal integration period set to a multiple of the 50/60 Hz power line period. (Figure 2B)
30
NORMAL MODE REJECTION (dB)
1
Signal Integrate Cycle
When the auto-zero loop is opened, the internal differ+ - ential inputs connect to V IN and VIN. The differential input signal is integrated for a fixed time period. The signal integration period is 1000 counts. The externally set clock frequency is divided by four before clocking the internal counters. The integration time period is: TSI = where: fOSC = External Clock Frequency The differential input voltage must be within the device common-mode range (1V of either supply) when the converter and measured system share the same power supply common (ground). If the converter and measured system do - not share the same power supply common, VIN should be tied to analog common. Polarity is determined at the end of the signal integrate phase. The sign bit is a true polarity indication in that signals less than 1 LSB are correctly determined. This allows precision null detection, limited only by device noise and auto-zero residual offsets. 4 fOSC x 1000
2 3 4 5 6 7
20
10
T = MEASUREMENT PERIOD 0 0.1/T 1/T INPUT FREQUENCY 10/T
Reference Integrate Cycle
The final phase is reference integrate or de-integrate. - + VIN is internally connected to analog common and V IN is connected across the previously charged reference capacitor. Circuitry within the chip ensures that the capacitor will be connected with the correct polarity to cause the integrator output to return to zero. The time required for the output to return to zero is proportional to the input signal and is between 0 and 2000 counts. The digital reading displayed is: 1000 x VIN VREF
Figure 2B. Normal-Mode Rejection of Dual Slope Converter
ANALOG SECTION
In addition to the basic signal integrate and deintegrate cycles discussed, the circuit incorporates an auto-zero cycle. This cycle removes buffer amplifier, integrator, and comparator offset voltage error terms from the conversion. A true digital zero reading results without adjusting external potentiometers. A complete conversion consists of three cycles: an auto-zero, signal-integrate and reference-integrate cycle.
DIGITAL SECTION (TC7106A)
The TC7106A (Figure 3) contains all the segment drivers necessary to directly drive a 3 -1/2 digit liquid crystal display (LCD). An LCD backplane driver is included. The backplane frequency is the external clock frequency divided by 800. For three conversions/second the backplane frequency is 60Hz with a 5V nominal amplitude. When a segment driver is in phase with the backplane signal the segment is "OFF." An out of phase segment drive signal causes the segment to be "ON" or visible. This AC drive configuration results in negligible DC voltage across each LCD segment. This insures long LCD display life. The polarity segment driver is "ON" for negative analog inputs. If + - V IN and VIN are reversed, this indicator will reverse.
3-189
Auto-Zero Cycle
During the auto-zero cycle the differential input signal is disconnected from the circuit by opening internal analog gates. The internal nodes are shorted to analog common (ground) to establish a zero-input condition. Additional analog gates close a feedback loop around the integrator and comparator. This loop permits comparator offset voltage error compensation. The voltage level established on CAZ compensates for device offset voltages. The offset error referred to the input is less than 10V. The auto-zero cycle length is 1000 to 3000 counts. TELCOM SEMICONDUCTOR, INC.
8
TC7106 TC7106A TC7107 TC7107A
3-190
TYPICAL SEGMENT OUTPUT + V 0.5mA SEGMENT OUTPUT 2mA LCD DISPLAY
TC7106A
INTERNAL DIGITAL GROUND BACKPLANE 21
+ C REF
+ VREF 34 36
CREF
- VREF 35
RINT - C REF V BUFF 33 28 V + 1
CAZ
CINT VINT LCD SEGMENT DRIVERS
Figure 3. TC7106A Block Diagram
29 INTEGRATOR
27 TO DIGITAL SECTION 7 SEGMENT DECODE 7 SEGMENT DECODE 7 SEGMENT DECODE
/ 200
- 10 A 31 INT A/Z ANALOG COMMON - V IN 32 30 INT DE (+) DE (-) DE (-) DE (+) - + V+- 3.0V LOW TEMPCO VREF A/Z A/Z +
- +
+ -
DATA LATCH
A/Z + V IN COMPARATOR
THOUSANDS HUNDREDS TENS UNITS
TO SWITCH DRIVERS FROM COMPARATOR OUTPUT CLOCK fOSC
1 /4 6.2V 37
V+
3-1/2 DIGIT A/D CONVERTERS
AZ & DE () 26 - V 40 OSC 1 39 OSC 2 ROSC 38 OSC 3 COSC
CONTROL LOGIC
INTERNAL DIGITAL GOUND
TEST VTH = 1V 500 26 V-
TELCOM SEMICONDUCTOR, INC.
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
When the TEST pin on the TC7106A is pulled to V+, all segments are turned "ON." The display reads -1888. During this mode the LCD segments have a constant DC voltage impressed. DO NOT LEAVE THE DISPLAY IN THIS MODE FOR MORE THAN SEVERAL MINUTES! LCD displays may be destroyed if operated with DC levels for extended periods. The display font and the segment drive assignment are shown in Figure 4.
DISPLAY FONT
1
*
Signal Integrate: 1000 Counts (4000 Clock Pulses) This time period is fixed. The integration period is: TSI = 4000
2 3 4 5
[]
1 fOSC
Where fOSC is the externally set clock frequency. * Reference Integrate: 0 to 2000 Counts (0 to 8000 Clock Pulses)
The TC7106A/7107A are drop-in replacements for the 7106/7107 parts. External component value changes are not required to benefit from the low drift internal reference.
1000's 100's 10's 1's
Clock Circuit
Three clocking methods may be used: 1. An external oscillator connected to pin 40. 2. A crystal between pins 39 and 40. 3. An R-C oscillator using all three pins.
Figure 4. Display Font and Segment Assignment
In the TC7106A, an internal digital ground is generated from a 6 volt zener diode and a large P channel source follower. This supply is made stiff to absorb the large capacitive currents when the backplane voltage is switched.
/4
TO COUNTER
40 CRYSTAL
39
38
DIGITAL SECTION (TC7107A)
Figure 5 shows the TC7107A. It is designed to drive common anode LEDs. It is identical to the TC7106A except that the regulated supply and backplane drive have been eliminated and the segment drive is typically 8mA. The 1000's output (pin 19) sinks current from two LED segments, and has a 16mA drive capability. In both devices, the polarity indication is "ON" for nega- + tive analog inputs. If VIN and V IN are reversed, this indication can be reversed also, if desired. The display font is the same as the TC7106A.
EXT OSC
RC NETWORK TO TEST PIN ON TSC7106A TO GND PIN ON TSC7107A
Figure 6. Clock Circuits
TC7106A TC7107A
COMPONENT VALUE SELECTION Auto-Zero Capacitor - CAZ
The CAZ capacitor size has some influence on system noise. A 0.47F capacitor is recommended for 200mV fullscale applications where 1 LSB is 100V. A 0.047F capacitor is adequate for 2.0V full-scale applications. A mylar dielectric capacitor is adequate.
6 7
System Timing
The oscillator frequency is divided by 4 prior to clocking the internal decade counters. The three-phase measurement cycle takes a total of 4000 counts or 16000 clock pulses. The 4000 count cycle is independent of input signal magnitude. Each phase of the measurement cycle has the following length: * Auto-Zero Phase: 1000 to 3000 Counts (4000 to 12000 Clock Pulses) For signals less than full-scale, the auto-zero phase is assigned the unused reference integrate time period. TELCOM SEMICONDUCTOR, INC.
Reference Voltage Capacitor - CREF
The reference voltage used to ramp the integrator output voltage back to zero during the reference-integrate cycle is stored on CREF. A 0.1F capacitor is acceptable - when VIN is tied to analog common. If a large common-mode - voltage exists (VREF analog common) and the application requires 200mV full-scale, increase CREF to 1.0 F. Rollover error will be held to less than 1/2 count. A mylar dielectric capacitor is adequate.
3-191
8
TC7106 TC7106A TC7107 TC7107A
3-192
TYPICAL SEGMENT OUTPUT + V 0.5mA SEGMENT OUTPUT 8mA LED DISPLAY
TC7107A
INTERNAL DIGITAL GROUND
+ C REF
+ VREF 34 36
CREF
- VREF 35
RINT - C REF V BUFF 33 28 V + 1
CAZ
Figure 5. TC7107A Block Diagram
CINT VINT LCD SEGMENT DRIVERS
29 INTEGRATOR
27 TO DIGITAL SECTION 7 SEGMENT DECODE 7 SEGMENT DECODE 7 SEGMENT DECODE
- 10 A 31 INT A/Z ANALOG COMMON - V IN 32 DE (+) DE (-) DE (-) DE (+) - + V+- 3.0V LOW TEMPCO VREF A/Z A/Z +
- +
+ -
DATA LATCH
A/Z + V IN COMPARATOR
THOUSANDS HUNDREDS TENS UNITS
TO SWITCH DRIVERS FROM COMPARATOR OUTPUT CLOCK fOSC
3-1/2 DIGIT A/D CONVERTERS
1 /4
V+
30 INT
AZ & DE () 26 - V 40 OSC 1 39 OSC 2 ROSC 38 OSC 3 COSC
LOGIC CONTROL 21 DIGITAL GROUND
TELCOM SEMICONDUCTOR, INC.
DIGITAL GOUND
500 37 TEST
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
Integrating Capacitor - CINT
CINT should be selected to maximize the integrator output voltage swing without causing output saturation. Due to the TC7106A/7107A superior temperature coefficient specification, analog common will normally supply the differential voltage reference. For this case a 2V full-scale integrator output swing is satisfactory. For 3 readings/ second (fOSC = 48kHz) a 0.22F value is suggested. If a different oscillator frequency is used, CINT must be changed in inverse proportion to maintain the nominal 2 V integrator swing. An exact expression for CINT is: (4000) ( CINT = 1 fOSC VINT Where: fOSC = Clock frequency at Pin 38 VFS = Full-scale input voltage RINT = Integrating resistor VINT = Desired full-scale integrator output swing CINT must have low dielectric absorption to minimize rollover error. A polypropylene capacitor is recommended. )( VFS ) RINT
1
Oscillator Components
ROSC (Pin 40 to Pin 39) should be 100k. COSC is selected using the equation: fOSC = 0.45 RC
2 3 4 5 6 7
For fOSC of 48kHz, COSC is 100pF nominally. Note that fOSC is divided by four to generate the TC7106A internal control clock. The backplane drive signal is derived by dividing fOSC by 800. To achieve maximum rejection of 60Hz noise pickup, the signal-integrate period should be a multiple of 60Hz. Oscillator frequencies of 240kHz, 120kHz, 80kHz, 60kHz, 48kHz, 40kHz, etc. should be selected. For 50 Hz rejection, oscillator frequencies of 200kHz, 100kHz, 66 2/3kHz, 50kHz, 40kHz, etc. would be suitable. Note that 40kHz (2.5 readings/second) will reject both 50Hz and 60Hz.
Reference Voltage Selection
A full-scale reading (2000 counts) requires the input signal be twice the reference voltage. Required Full-Scale Voltage*
200.0mV 2.000V
* VFS = 2 VREF
VREF
100.0mV 1.000V
Integrating Resistor - RINT
The input buffer amplifier and integrator are designed with class A output stages. The output stage idling current is 100A. The integrator and buffer can supply 20A drive currents with negligible linearity errors. RINT is chosen to remain in the output stage linear drive region but not so large that printed circuit board leakage currents induce errors. For a 200mV full-scale, RINT is 47k. 2.0V full-scale requires 470k. Component Value
CAZ RINT CINT
Note:1.
Nominal Full-Scale Voltage
200.0mV 0.47F 47k 0.22F 2.000V 0.047F 470k 0.22F
fOSC = 48kHz (3 readings/sec)
In some applications a scale factor other than unity may exist between a transducer output voltage and the required digital reading. Assume, for example, a pressure transducer output is 400mV for 2000 lb/in2. Rather than dividing the input voltage by two the reference voltage should be set to 200mV. This permits the transducer input to be used directly. The differential reference can also be used when a digital zero reading is required when VIN is not equal to zero. This is common in temperature measuring instrumentation. A compensating offset voltage can be applied between - analog common and VIN. The transducer output is con+ nected between V IN and analog common. The internal voltage reference potential available at analog common will normally be used to supply the converter's reference. This potential is stable whenever the supply potential is greater than approximately 7V. In applications where an externally-generated reference voltage is desired, refer to Figure 7.
8
TELCOM SEMICONDUCTOR, INC.
3-193
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
V+ + VREF - VREF IZ V+ V+ 6.8k V+
+ VIN - + - + INPUT BUFFER CI RI - VI INTEGRATOR TI VI = V CM - VIN RI CI Where: 4000 T I = INTEGRATION TIME =
6.8V ZENER
TC7106A 20k TC7107A
+ VREF - VREF COMMON TC04 1.2V REF
TC7106A TC7107A
VCM
[
[
f OSC
C I = INTEGRATION CAPACITOR R I = INTEGRATION RESISTOR
Figure 9. Common-Mode Voltage Reduces Available Integrator Swing. (VCOM VIN)
(a)
(b)
Figure 7. External Reference
DEVICE PIN FUNCTIONAL DESCRIPTION Differential Signal Inputs (V+IN (Pin 31), V-IN (Pin 30))
The TC7106A/7017A is designed with true differential inputs and accepts input signals within the input stage common mode voltage range (VCM). The typical range is V+ -1.0 to V- +1 V. Common-mode voltages are removed from the system when the TC7106A/TC7107A operates from a battery or floating power source (isolated from measured - system) and VIN is connected to analog common (VCOM): See Figure 8. In systems where common-mode voltages exist, the 86dB common-mode rejection ratio minimizes error. Common-mode voltages do, however, affect the integrator output level. Integrator output saturation must be prevented. A worst-case condition exists if a large positive VCM exists in conjunction with a full-scale negative differential signal. The negative signal drives the integrator output positive along with VCM (Figure 9). For such applications the integrator output swing can be reduced below the recommended 2.0V
full-scale swing. The integrator output will swing within 0.3V of V+ or V- without increasing linearity errors.
Differential Reference + - (V REF (Pin 36), VREF (Pin 35))
The reference voltage can be generated anywhere within the V+ to V- power supply range. To prevent rollover errors from being induced by large common-mode voltages, CREF should be large compared to stray node capacitance. The TC7106A/TC7107A circuits have a significantly lower analog common temperature coefficient. This gives a very stable voltage suitable for use as a reference. The temperature coefficient of analog common is 20ppm/C typically.
SEGMENT DRIVE
LCD DISPLAY
MEASURED SYSTEM V + GND
VBUF V+IN V -IN
CAZ
VINT
POL BP OSC1 OSC3 OSC2 V-
V- V+ V -
TC7106A ANALOG - + + COMMON VREF VREF V
GND POWER SOURCE
+ 9V
- Figure 8. Common-Mode Voltage Removed in Battery Operation with VIN = Analog Common
3-194
TELCOM SEMICONDUCTOR, INC.
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
Analog Common (Pin 32)
The analog common pin is set at a voltage potential approximately 3.0V below V+. The potential is guaranteed to be between 2.7V and 3.35 V below V+. Analog common is tied internally to the N channel FET capable of sinking 20mA. This FET will hold the common line at 3.0V should an external load attempt to pull the common line toward V+. Analog common source current is limited to 10A. Analog common is therefore easily pulled to a more negative voltage (i.e., below V+ - 3.0V). + - The TC7106A connects the internal V IN and VIN inputs to analog common during the auto-zero cycle. During the - reference-integrate phase, VIN is connected to analog com- mon. If VIN is not externally connected to analog common, a common-mode voltage exists. This is rejected by the converter's 86dB common-mode rejection ratio. In battery - operation, analog common and VIN are usually connected, removing common-mode voltage concerns. In systems where - VIN is connected to the power supply ground or to a given - voltage, analog common should be connected to VIN. The analog common pin serves to set the analog section reference or common point. The TC7106A is specifically designed to operate from a battery or in any measurement system where input signals are not referenced (float) with respect to the TC7106A power source. The analog common potential of V+ - 3.0V gives a 6 V end of battery life voltage. The common potential has a 0.001%/% voltage coefficient and a 15 output impedance. With sufficiently high total supply voltage (V+ - V- > 7.0V) analog common is a very stable potential with excellent temperature stability--typically 20ppm/C. This potential can be used to generate the reference voltage. An external voltage reference will be unnecessary in most cases because of the 50ppm/C maximum temperature coefficient. See Internal Voltage Reference discussion.
1
Internal Voltage Reference Stability
The analog common voltage temperature stability has been significantly improved (Figure 10). The "A" version of the industry standard circuits allow users to upgrade old systems and design new systems without external voltage references. External R and C values do not need to be changed. Figure 11 shows analog common supplying the necessary voltage reference for the TC7106A/TC7107A.
2 3
200
TEMPERATURE COEFFICIENT (ppm/C)
180 160 140 120 100 80 60 40 20 0
NO MAXIMUM SPECIFIED
NO MAXIMUM SPECIFIED TYPICAL
MAXIMUM LIMIT
NO MAXIMUM SPECIFIED TYPICAL
4
ICL7136
TYPICAL
TC 7106A
ICL7106
5 6 7
Figure 10. Analog Common Temperature Coefficient
1 V- TC7106A TC7107A + VREF - VREF 36 VREF 35 1k V+ 24k
Test (Pin 37)
The TEST pin potential is 5V less than V+. TEST may be used as the negative power supply connection for external CMOS logic. The TEST pin is tied to the internally generated negative logic supply (Internal Logic Ground) through a 500 resistor in the TC7106A. The TEST pin load should be no more than 1mA . If TEST is pulled to V+ all segments plus the minus sign will be activated. Do not operate in this mode for more than several minutes with the TC7106A. With TEST = V+ the LCD segments are impressed with a DC voltage which will destroy the LCD. The TEST pin will sink about 10mA when pulled to V+.
ANALOG 32 COMMON SET VREF = 1/2 VFULL SCALE
Figure 11. Internal Voltage Reference Connection
8
3-195
TELCOM SEMICONDUCTOR, INC.
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
POWER SUPPLIES
The TC7107A is designed to work from 5V supplies. However, if a negative supply is not available, it can be generated from the clock output with two diodes, two capacitors, and an inexpensive IC. (Figure 12) In selected applications a negative supply is not required. The conditions to use a single +5V supply are: * The input signal can be referenced to the center of the common-mode range of the converter. * The signal is less than 1.5V. * An external reference is used. The TSC7660 DC to DC converter may be used to generate - 5 V from +5 V (Figure 13).
V + CD4009 V+ OSC1 OSC2 OSC3
TC7107 Power Dissipation Reduction
The TC7107A sinks the LED display current and this causes heat to build up in the IC package. If the internal voltage reference is used, the changing chip temperature can cause the display to change reading. By reducing the LED common anode voltage the TC7107A package power dissipation is reduced. Figure 14 is a photograph of a curve-tracer display showing the relationship between output current and output voltage for a typical TC7107CPL. Since a typical LED has 1.8 volts across it at 7mA, and its common anode is connected to +5V, the TC7107A output is at 3.2V (point A on Figure 13). Maximum power dissipation is 8.1mA x 3.2V x 24 segments = 622mW. Notice, however, that once the TC7107A output voltage is above two volts, the LED current is essentially constant as output voltage increases. Reducing the output voltage by 0.7V (point B in Figure 14) results in 7.7mA of LED current, only a 5 percent reduction. Maximum power dissipation is only 7.7mA x 2.5 V x 24 = 462mW, a reduction of 26%. An output voltage reduction of 1 volt (point C) reduces LED current by 10% (7.3mA) but power dissipation by 38%! (7.3mA x 2.2V x 24 = 385mW).
0.047 F
1N914 10 F 1N914 + -
TC7107A
GND V- V- = -3.3V
Figure 12. Generating Negative Supply From +5 V
+5 V
V
1 +
36 + VREF 35 - VREF 32 COM
LED DRIVE TC7107A
Figure 14. TC7107A Output Current vs Output Voltage
+ 31 VIN VIN - 30 VIN
V 8 + 10F 2 5 4 TC7660 3 + 10F (-5 V)
- 26
GND
21
*3-1/2 DIGIT ADC
Figure 13. Negative Power Supply Generation with TC7660 3-196
Reduced power dissipation is very easy to obtain. Figure 15 shows two ways: either a 5.1 ohm, 1/4 watt resistor or a 1 Amp diode placed in series with the display (but not in series with the TC7107A). The resistor will reduce the TC7107A output voltage, when all 24 segments are "ON," to point "C" of Figure 14. When segments turn off, the output voltage will increase. The diode, on the other hand, will result in a relatively steady output voltage, around point "B." In addition to limiting maximum power dissipation, the resistor reduces the change in power dissipation as the display changes. This effect is caused by the fact that, as TELCOM SEMICONDUCTOR, INC.
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
fewer segments are "ON," each "ON" output drops more voltage and current. For the best case of six segments (a "111" display) to worst case (a "1888" display) the resistor will change about 230mW, while a circuit without the resistor will change about 470mW. Therefore, the resistor will reduce the effect of display dissipation on reference voltage drift by about 50%. The change in LED brightness caused by the resistor is almost unnoticeable as more segments turn off. If display brightness remaining steady is very important to the designer, a diode may be used instead of the resistor.
Figure 15. Diode or Resistor Limits Package Power Dissipation
1
APPLICATIONS INFORMATION Liquid Crystal Display Sources
Several LCD manufacturers supply standard LCD displays to interface with the TC7106A 3-1/2 digit analog-todigital converter. Manufacturer
Crystaloid Electronics AND
2
Part Numbers1
C5335, H5535, T5135, SX440 FE 0201,0701 FE 0203, 2201 FE 0501 LD-B709BZ LD-H7992AZ 3902, 3933, 3903
Address/Phone
5282 Hudson Dr. Hudson, OH 44236 216/655-2429 720 Palomar Ave. Sunnyvale, CA 94086 408/523-8200 3415 Kashikawa St. Torrance, CA 90505 213/534-0360 612 E. Lake St. Lake Mills, WI 53551 414/648-2361
3 4 5 6 7
APPLICATIONS INFORMATION
+5V
+
1 M TP3
IN -
-5V
Epson
150
24k 1k 100 pF TP5 100 k 40 TP2 TP1
Hamlin, Inc.
0.01 F
0.1 F
0.47 F
0.22 F
DISPLAY
Note: 1. Contact LCD manufacturer for full product listing/specifications.
47 k 30 TP 4
Light Emitting Diode Display Sources
21
TC7107A
1 10 20
Several LED manufacturers supply seven segment digits with and without decimal point annunciators for the TC7107A. Manufacturer Address
640 Page Mill Rd. Palo Alto, CA 94304 720 Palomar Ave. Sunnyvale, CA 94086
Display Type
LED LED
DISPLAY
5.1 1/4W 1N4001
Hewlett-Packard Components AND
8
TELCOM SEMICONDUCTOR, INC.
3-197
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
Decimal Point and Annunciator Drive
The TEST pin is connected to the internally-generated digital logic supply ground through a 500 resistor. The TEST pin may be used as the negative supply for external CMOS gate segment drivers. LCD display annunciators for decimal points, low battery indication, or function indication may be added without adding an additional supply. No more than 1mA should be supplied by the TEST pin: its potential is approximately 5V below V+.
V+ V+ 4049
Ratiometric Resistance Measurements
The true differential input and differential reference make ratiometric reading possible. Typically in a ratiometric operation, an unknown resistance is measured with respect to a known standard resistance. No accurately defined reference voltage is needed. The unknown resistance is put in series with a known standard and a current passed through the pair. The voltage developed across the unknown is applied to the input and the voltage across the known resistor is applied to the reference input. If the unknown equals the standard, the display will read 1000. The displayed reading can be determined from the following expression: Displayed Reading = R Unknown R Standard x 1000
TC7106A
BP 21 37 GND TO LCD BACKPLANE TO LCD DECIMAL POINT
The display will overrange for R Unknown 2 x R standard.
TEST
RSTANDARD
V+ V+ BP
+ VREF V- + V IN
V+
REF
LCD DISPLAY TC7106A
RUNKNOWN - V IN
TC7106A
DECIMAL POINT SELECT
TO LCD DECIMAL POINTS
ANALOG COMMON
Figure 17. Low Parts Count Ratiometric Resistance Measurement
TEST
4030 GND
Figure 16. Decimal Point Drive Using TEST as Logic Ground
3-198
TELCOM SEMICONDUCTOR, INC.
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
+
IN4148 200mV 10k 9M 2V 0.02 F 1M 1M 47k 1W 10% - 6.8F + + 1F -
1
9V
26 V-
VIN
1 2 3 4 5 6 AD636
14 13 12 11 10 9
1M 10% 1k 24k
1
V+
27
2 3 4
TC7106A
36 35 32 31 0.01 F V+ REF V- REF ANALOG COMMON V+ IN V- IN V-
29
900k
20 V
90k
28
200 V
10k 20kW 10% C1 = 3-10pF VARIABLE, C2 = 132pF VARIABLE
7
8
2.2F
40
COM
30 26
38 39
SEG DRIVE
BP
LCD DISPLAY
Figure 18. 3 1/2 Digit True RMS AC DMM
+
9V
+ 5.6k 160k V+ - VIN + VIN 0.7%/C PTC R3 R2 20k + VREF - VREF COMMON
9V
5
V-
160k
300k
300k
V+ - VIN + VIN + VREF - VREF COMMON
V-
1N914
TC7106A VFS = 2V
R1 20k
1N4148 SENSOR R2 50k
R1 50k
TC7106A
6 7
Figure 19. Temperature Sensor
Figure 20. Positive Temperature Coefficient Resistor Temperature Sensor
8
TELCOM SEMICONDUCTOR, INC.
3-199
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
9V
2 V+
CONSTANT 5 V V+ REF 6 51k R4 ADJ TEMP 5 3 NC 5.1k R5
1 V+
REF02
VOUT
TC911
R2 8 1 4 VOUT = 1.86V @ 25C R1
50k
TC7106A
V- REF VFS = 2.00V V- IN V+ IN
TEMPERATURE DEPENDENT OUTPUT GND 4
1.3k
Figure 21. Integrated Circuit Temperature Sensor
TO PIN 1 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 SET VREF = 100mV
100k 100pF
0.1F
1 k
22k 1M
+ IN + - 9V -
TC7106A
0.01F
0.47F 47k 0.22F
TO DISPLAY TO BACKPLANE
Figure 22. TC7106A Using the Internal Reference: 200mV FullScale, 3 Readings-per-second (RPS).
3-200
+
3
-
2
50k COMMON
V- 26
TO PIN 1 40 39 38 37 36 35 34 33 32 31 TC7107A 30 29 28 27 26 25 24 23 22 21 SET VREF = 100mV
100k 100pF
+5V
0.1F
1k
22k 1M
+ IN -
0.01F
0.47F 47k 0.22F
-5V
TO DISPLAY
Figure 23. TC7107A Internal Reference (200mV Full-Scale, - 3RPS, VIN Tied to GND for Single Ended Inputs).
TELCOM SEMICONDUCTOR, INC.
3-1/2 DIGIT A/D CONVERTERS TC7106 TC7106A TC7107 TC7107A
1
V+
1
40
TO PIN 1
2
SET VREF = 1V 100k 100pF
25k 24k
TO LOGIC VCC
TO LOGIC GND
TC7106A TC7106A TC7107A
O/R
V-
U/R
20 21
CD4023 OR 74C10 CD4077 O/R = OVERRANGE U/R = UNDERRANGE
40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21
V+ + IN -
0.1F
1M 0.01F
3 4 5
0.047F 470k
0.22F
V-
TO DISPLAY
Figure 24. Circuit for Developing Underrange and Overrange Signals from TC7106A Outputs.
Figure 25. TC7106A/TC7107A: Recommended Component Values for 2.00V Full-Scale
TO PIN 1
TO PIN 1
100k
100pF
TC7107A
40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21
SET VREF = 100mV 10k 10k V
TC04 1.2V
+
0.1F
1k
+ 1M - IN
0.01F
0.47F 47k 0.22F
TC7107A
V
-
TO DISPLAY
40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21
100k 100pF
SET VREF = 100mV 10k 10k V
TC04 1.2V
+
0.1F
1 k
+ 1M - IN
0.01F 0.47F 47k 0.22F
6 7
TO DISPLAY
Figure 26. TC7107A With a 1.2V External Band-Gap Reference. - (VIN Tied to Common.)
Figure 27. TC7107A Operated from Single +5V Supply. An External Reference Must Be Used in This Application.
8
TELCOM SEMICONDUCTOR, INC.
3-201

▲Up To Search▲

Price & Availability of TC7106

	To Download TC7106 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .