TelCom Semiconductor Inc TC826CBU Datasheet

A/D CONVERTER WITH BAR GRAPH DISPLAY OUTPUT

1

TC826

2

FEATURES

■ Bipolar A/D Conversion

■ 2.5% Resolution

■ Direct LCD Display Drive

■ ‘Thermometer’ Bar or Dot Display

■ 40 Data Segments Plus Zero

■ Overrange Plus Polarity Indication

■ Precision On–Chip Reference ................ 35ppm/°C

■ Differential Analog Input

■ Low Input Leakage .......................................... 10pA

■ Display Flashes on Overrange

■ Display Hold Mode

■ Auto–Zero Cycle Eliminates Zero Adjust

Potentiometer

■ 9V Battery Operation

■ Low Power Consumption ............................ 1.1mW

■ 20mV to 2.0 V Full–Scale Operation

■ Non–Multiplexed LCD Drive for Maximum

Viewing Angle

PIN CONFIGURATION

BAR 35

BAR 36

BAR 37

BAR 38

BAR 39

BAR 40

OR

POL –

BAR/DOT

HOLD

ANALOG

COMMON

– IN

REF IN

+

C

REF
–

C

REF

V

V

BUF
C

V

V

OSC1
OSC2

BAR 0

TEST

NC

626364 49

61

NC

1
2

+IN

3
4

5
6
7
8

DD

9

10

AZ

11

INT

SS

12
13
14

BP

15
16

NC

BAR 1

BAR 2

BAR 3

BAR 4

TC826CBU

BAR 6

BAR 5

BAR 7

BAR 8

26

BAR 9

27

BAR 10

BAR 11

BAR 34

302928

BAR 12

BAR 33

5051255224532354225521562057195818591760

31

BAR 13

BAR 32

32

BAR 14

BAR 31

BAR 15

48

NC

47

BAR 30

46

BAR 29

45

BAR 28

44

BAR 27

43

BAR 26

42

BAR 25

41

BAR 24

40

BAR 23

39

BAR 22

38

BAR 21

37

BAR 20

36

BAR 19

35

BAR 18

34

BAR 17

33

BAR 16

GENERAL DESCRIPTION

In many applications a graphical display is preferred
over a digital display. Knowing a process or system oper­ates, 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 inter­pretation 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 multi­plexed 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.

ORDERING INFORMATION

Part No. Package Temperature

TC826CBU 64–Pin PFP 0°C to +70°C

3

4

5

6

7

TELCOM SEMICONDUCTOR, INC.

8

TC826-6 11/6/96

3-171

TC826

A/D CONVERTER WITH

BAR GRAPH DISPLAY OUTPUT

ABSOLUTE MAXIMUM RATINGS*

Supply Voltage (V+ to V–)............................................15V

Analog Input Voltage (either input)
Power Dissipation (TA ≤ 70°C)

64-Pin Flat Package .........................................1.14W

Operating Temperature

(1)

................... V+ to V

*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.

‘C’ Devices.............................................0°C to +70°C

Storage Temperature ............................– 65°C to +150°C

Lead Temperature (Soldering, 10 sec) .................+300°C

ELECTRICAL CHARACTERISTICS:

unless otherwise stated VS = 9V; R

= 430 kΩ; TA = 25°C; Full–Scale = 20 mV.

OSC

No. Symbol Parameter Test Conditions Min Typ Max Unit

1 — Zero Input VIN = 0.0V – 0 ±0 +0 Display
2 — Zero Reading Drift VIN = 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 –VIN = +V

IN

5 EN Noise VIN = 0V — 60 — µV
6 ILK Input Leakage Current VIN = 0V — 10 20 pA
7 CMRR Common–Mode VCM = ±1V — 50 — µV/V

Rejection Ratio VIN = 0V

8 — Scale Factor 0 ≤ T

≤ +70°C — 1 — ppm/°C

A

Temperature Coefficient External Ref. Temperature

Coefficient = 0 ppm/°C

9 VCTC Analog Common 250kΩ Between — 35 100 ppm/°C

Temperature Coefficient Common and V

+

0°C ≤ TA ≤ +70°C

10 V

COM

Analog Common 250kΩ Between 2.7 2.9 3.35 V
Voltage Common and V

DD

11 VSD LCD Segment 4 5 6 V

Drive Voltage

12 VBD LCD Backplane 4 5 6 V

Drive Voltage

13 I

NOTES: 1. Input voltages may exceed the supply voltages when

DD

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.

Power Supply Current — 125 175 µA

– 1 0 +1 Count

P–P

P–P

P–P

3-172

TELCOM SEMICONDUCTOR, INC.

A/D CONVERTER WITH
BAR GRAPH DISPLAY OUTPUT

PIN DESCRIPTION

1

TC826

Pin No.
(64-Plastic
Quad Flat
Package) Symbol Description

1NC
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 V

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.

BUF

AZ

INT

SS

+

Reference capacitor connection.

–

Reference capacitor connection.

Buffer output. Integration resistor connection.

Negative comparator input. Auto-zero capacitor connection.

Integrator output. Integration capacitor connection.

Negative supply terminal.

6 CREF
7 CREF
8VDDPositive supply terminal.
9V

10 C
11 V
12 V
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
17 NC
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

and analog-common can be

DD

2

3

4

5

6

7

8

TELCOM SEMICONDUCTOR, INC.

3-173

A/D CONVERTER WITH

BAR GRAPH DISPLAY OUTPUT

TC826

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
48 NC
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 V

1MΩ 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

through

SS

3-174

TELCOM SEMICONDUCTOR, INC.