Datasheet TC826CBU Datasheet (Microchip Technology)

TC826

Analog-to-Digital Converter with Bar Graph Display Output

Features

• Bipolar A/D Conversion

• 2.5% Resolution

• Direct LCD Display Drive

• ‘Thermometer’ BAR or DOT Display

• 40 Data Segments Plus Zero

• Over Range Plus Polarity Indication

• PrecisionOn-Chip Reference: 35ppm/°C

• Differential Analog Input

• Low Input Leakage: 10pA

• Display Flashes on Over Range

• Display HOLD Mode

• Auto-Zero Cycle Eliminates Zero Adjust
Potentiometer

• 9V Battery Operation

• Low Power Consumption: 1.1mW

• 20mV to 2.0V Full Scale Operation

• Non-Multiplexed LCD Drive for Maximum
Viewing Angle

Device Selection Table

Part Number Package Temperature Range

TC826CBU 64-Pin PQFP 0°Cto+70°C

General Description

In many applications, a graphical display is preferred
over a digital display. Knowing a process or system
operates,forexample,within design limitsismorevalu­able than a direct system variable read out. A bar or
moving dot display supplies informationprecisely with­out requiringfurther 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 extendsfrom 20mV to2V.TheTC826 sensitivity
is 500µV. A low drift35ppm/°C internal reference,LCD
backplane oscillator and driver, input polarity LCD
driver, and over rangeLCD driver make designs simple
and low cost. The CMOS design required only 125µA
from a 9V battery.In +5V systems, a TC7660DC 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 allbelow it are on. The
DOT mode activates only the segment equal to the
input. In either mode, t he polarity signal is active for
negative input signals. An over range input signal
causesthedisplayt o flashandactivates the over range
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 5µV/°C. Conversion rate is typically
5 per second and is adjustable by a single external
resistor.

A compact, 0.5" s quare, flat package minimizes PC
board area. The high pin count LSI package makes
multiplexed LCD displays unnecessary. Low cost,
directdriveLCD displays offer the widest viewing angle
and are readily available. A standard display is avail­able now for TC826 prototypingwork.



2002 Microchip TechnologyInc. DS21477B-page 1

TC826

Package Type

64-Pin PQFP

ANALOG

COMMON

REF IN

C

C

OSC2

BAR 0

Typical Application

NC

+IN

REF

REF

V

V

BUF

C

V

INT

V

OSC1

NC

1

2

3

-IN

4

5

+

6

-

7

DD

8

9

AZ

10

11

SS

12

13

14

BP

15

16

NC

BAR/DOT

HOLD

TEST

61

626364 49

19

BAR 3

BAR 2

BAR 1

OR

POL-

5818591760

TC826CBU

BAR 5

BAR 4

BAR 40

BAR 6

BAR 39

BAR 7

BAR 38

26

BAR 8

BAR 37

27

BAR 9

BAR 36

BAR 10

BAR 34

BAR 35

BAR 12

BAR 11

BAR 33

302928

BAR 13

BAR 32

5051255224532354225521562057

31

BAR 14

BAR 31

32

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

1MΩ

1MΩ

1MΩ

Component

R

INT

C

INT

C

REF

C

AZ

C

INT

C

AZ

V

61

62

BAR/DOT

HOLD

R

INT

V

BUFCAZ

TC826

63

TEST

12

V

SS

V

DD

9V

2V

Full Scale

2MΩ 20kΩ 20kΩ

0.033mf 0.033mf 0.033mf

1mf 1mf 1mf

0.068mf 0.068mf 0.014mf R1 + R2 = 250kΩ

R

1

200mV

Full Scale

REFINANALOG

COMMON -IN +IN

58 2 43 60

R

2

-IN +IN

20mV

Full Scale

11109

INT

BAR 0-

BAR 40 POL-

6

C

+

REF

7

C

-

REF

13

OSC1

14

OSC2

15

BP

59

OR

Segment Drive

–OR

C

REF

1.0mf

R

OSC

430kΩ

Backplane

41 Segment LCD
Bar Graph

DS21477B-page 2



2002 Microchip TechnologyInc.

TC826

1.0 ELECTRICAL

CHARACTERISTICS

Absolute Maximum Ratings*

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

*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
operation sections of the specifications is not implied.
Exposure to Absolute Maximum Rating conditions for
extended periods may affectdevice reliability.

Analog Input Voltage(Either Input) (Note 1)... V+ to V­Power Dissipation (T

≤ 70°C)

A

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

Operating Temperature Range:

Commercial Package (C)........................ 0°C to +70°C

StorageTemperature Range..............-65°C to +150°C

TC826 ELECTRICAL SP EC IFICATIONS

Electrical Characteristics: V

Symbol Parameter Min Typ Max Unit Test Conditions

Zero Input -0 ±0 +0 Display V
Zero Reading Dri ft — 0.2 1 µV/°C V

NL Linearity Error -1 0.5 +1 Count Max Deviation from Best Straight Line
R/O Rollover Error -1 0 +1 Count -V
EN Noise — 60 — µV
ILK InputLeakage Current — 10 20 pA V
CMRR Comm on Mode Rejection Ratio — 5 0 — µV/V VCM = ±1V

Scale Factor Temperature Coefficient — 1 — ppm/°C 0 ≤ T

V

CTC

V

COM

VSD LCD Segment Drive Voltage 4 5 6 V
VBD LCD Backplane DriveVoltage 4 5 6 V
I

DD

Note 1: Input voltagesmay exceedthe supplyvoltages when the input currentis limited to 100µA.

Analog Common Temperature
Coefficient

Analog Common Voltage 2.7 2.9 3.35 V 250kΩ betweenCommonand V

Power Supply Current — 125 175 µA

2: Static sensitivedevice. Unused devicesshould be stored in conductive material to protect devices from staticdischarge

and static fields.

3: Backplane drive is in phase with segmentdrive 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 V

=9V;R

S

=430kΩ;TA= 25°C; Full Scale = 20mV, unless otherwise stated.

OSC

=0.0V

IN

=0.0V

IN

0°C ≤ T

=+V

IN

P-PVIN

— 35 100 ppm/°C 250kΩ between Common and

P-P
P-P

=0V
=0V

IN

=0V

V

IN

A

External Ref. Temperature
Coefficient = 0ppm/°C

V+, 0°C ≤ T

SS

≤ +70°C

A

IN

≤ 7+0°C

≤ +70°C

A

for logic 0.

DD



2002 Microchip TechnologyInc. DS21477B-page 3

TC826

2.0 PIN DESCRIPTION

ThedescriptionsofthepinsarelistedinTable2-1.

TABLE 2-1: PIN FUNCTION TABLE

Pin Number

(64-Pin PQFP)

1 NC Positive analog signal input.
2ANALOG

3 +IN Positive analog signal input.
4 -IN Negative analog signal input.
5 REF IN Reference voltage positiveinput. Measured relative to analog common.

6C
7C
8V

9V
10 C
11 V
12 V
13 OSC1 Oscillator resistor (R
14 OSC2 Oscillator resistor (R
15 BP LCDBackplane driver.
16 BAR 0 LCD Segment driver: Bar 0.
17 NC No connection.
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 BAR10 LCD Segment driver: Bar 10.
28 BAR 11 LCD Segment driver: Bar 11.
29 BAR12 LCD Segment driver: Bar 12.
30 BAR13 LCD Segment driver: Bar 13.
31 BAR14 LCD Segment driver: Bar 14.
32 BAR15 LCD Segment driver: Bar 15.
33 BAR16 LCD Segment driver: Bar 16.
34 BAR17 LCD Segment driver: Bar 17.
35 BAR18 LCD Segment driver: Bar 18.
36 BAR19 LCD Segment driver: Bar 19.
37 BAR20 LCD Segment driver: Bar 20.
38 BAR21 LCD Segment driver: Bar 21.
39 BAR22 LCD Segment driver: Bar 22.
40 BAR23 LCD Segment driver: Bar 23.

Symbol Description

COMMON

+ Reference capacitor connection.

REF

- Reference capacitor connection.

REF

DD

BUF

AZ
INT
SS

Establishesthe internal analog ground point.A nalog common is set to 2.9V belowthe
positivesupply COMMON by an internalzener reference circuit. The voltage difference
betweenV
inputatREFIN(Pin5).

REF IN ≈ Full Scale/2.

Positive supply terminal.
Buffer output. Integration resistor connection.
Negative comparator input. Auto-zero capacitor connection.
Integrator output.Integrationcapacitorconnection.
Negative supply terminal.

DD

and analogcommoncan be used to supply the TC826 voltagereference

) connection.

OSC

) connection.

OSC

DS21477B-page 4



2002 Microchip TechnologyInc.

TABLE 2-1: PIN FUNCTION TABLE (CONTINUED)

Pin Number

(64-Pin PQFP)

41 BAR24 LCD Segment driver: Bar 24.
42 BAR25 LCD Segment driver: Bar 25.
43 BAR26 LCD Segment driver: Bar 26.
44 BAR27 LCD Segment driver: Bar 27.
45 BAR28 LCD Segment driver: Bar 28.
46 BAR29 LCD Segment driver: Bar 29.
47 BAR30 LCD Segment driver: Bar 30.
48 NC No connection.
49 BAR31 LCD Segment driver: Bar 31.
50 BAR32 LCD Segment driver: Bar 32.
51 BAR33 LCD Segment driver: Bar 33.
52 BAR34 LCD Segment driver: Bar 34.
53 BAR35 LCD Segment driver: Bar 35.
54 BAR36 LCD Segment driver: Bar 36.
55 BAR37 LCD Segment driver: Bar 37.
56 BAR38 LCD Segment driver: Bar 38.
57 BAR39 LCD Segment driver: Bar 39.
58 BAR40 LCD Segment driver: Bar 40.
59 OR LCDsegment driver thatindicated input out-of-rangecondition.
60 POL- LCD segment driver that indicates input signal is negative.
61 BAR/DOT

62 HOLD

63 TEST

64 NC No connection.

Symbol Description

Inputlogic signalthatselectsBARorDOTdisplay format.Normally in BAR mode.Connect
to V

through 1MΩ resistorforDOT format.

SS

Inputlogicsignal that preventsdisplay from changing.P ulled high internally to inactive
state.Connect to V

Input logic signal. Sets TC826 to BAR Display mode. BAR 0 to 40, plus OR flash on and
off.ThePOL-LCDdriver is on. Pulled high internally to inactivestate. Connectto V
1MΩ series resistor to activate.

through 1MΩ series resistor for HOLD mode operation.

SS

TC826

with

SS



2002 Microchip TechnologyInc. DS21477B-page 5

TC826

3.0 DETAILED DESCRIPTION

3.1 Dual Slope Conversion Principles

The TC826 is a dualslope,integratinganalog-to-digital
converter. The conventionaldual slope converter mea­surement cycle has two distinct phases:

• Input Signal Integration

• Reference VoltageIntegration (De-integration)
The input signal being converted is integrated for a

fixed time period (T
clock pulses. An opposite polarity constant reference
voltage is then i ntegrated until the integrator output
voltage returns to zero. The reference integration time
is directly proportional to the input signal (T
(Figure3-1).

In a simple dual slope converter, a complete conver­sion requires the integrator output to ‘ramp-up’ and
‘ramp-down’.

FIGURE 3-1: BASIC DUAL SLOPE CONVERTER

). Time is measured by counting

SI

)

RI

C

A simple mathematicalequation relates the input signal
reference voltage and integration time:

EQUATION 3-1:

t

1

INT

V

IN

∫

0

RC

Where:

= Ref erence Voltage

V

R

= Si gnal Integration Time (Fixed)

V

SI

= Ref erence Voltage I ntegration Time

T

RI

(Variable)

(t)dt =

V

RTRI

RC

Analog Input

Signal

Output

Integrator

+/–

REF

Voltage

Fixed Signal

Integrate

Time

R

Switch Driver

Polarity Control

Variable

Reference

Integrate

Time

Integrator

–

+

VIN ≈ 1/2 V

VIN ≈ 1/4 V

Comparator

–

+

Phase Control

FULL SCALE

FULL SCALE

Control

Logic

Clock

Counter

Display

DS21477B-page 6



2002 Microchip TechnologyInc.

TC826

T

y

For a constant VIN:

EQUATION 3-2:

T

VIN=V

The dual slope converter accuracy is unrelated t o 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.IntegratingADCs areimmunetothe largecon­version errors that plague successive approximation
converters in high noise environments. Interfering sig­nals with frequency components at multiples of the
averaging period will be attenuated (Figure 3-2).

The TC826 converter i mproves the conventional dual
slope conversion technique by incorporating an auto­zero phase. This phase eliminates zero scale offset
errors and drift. A potentiometer is not required to
obtain a zero output for zero input.

RI

R

T

SI

FIGURE 3-2: NORMAL MODE

REJECTION OF DUAL
SLOPE CONVERTER

30

T = Measurement
Period

20

10

Normal Mode Rejection (dB)

0

0.1/T 1/T 10/
Input Frequenc



2002 Microchip TechnologyInc. DS21477B-page 7

TC826

4.0 THEORY OF OPERATION

4.1 Analog Section

In addition to the basic signal integrate and de­integrate cycles discussed above, the TC826 incorpo­rates an auto-zero cycle.This cycle removes buffer
amplifier, integrator, and comparator offset voltage
error terms from the conversion. A t rue digital zero
reading results without external adjusting potentiome­ters. A complete conversion consists of three cycles:
an auto-zero, signal integrate and reference cycle
(Figure 4-1 and Figure 4-2).

4.1.1 AUTO-ZERO CYCLE

During the auto-zero cycle, the differential input signal
is disconnected from the circuit by opening internal
analog gates. The internalnodesare shorted to analog
common (internal analog ground) to establish a zero
input condition. Additional analog gates close a feed­backlooparoundtheoffsetvoltageerrorcompensation.
The voltage level established on C
device offset voltages.

FIGURE 4-1: TC826 ANALOG SECTION

compensates for

AZ

The auto-zero cycle length is 19 counts minimum.
Unused time in the de-integrate cycle is added to the
auto-zero cycle.

4.1.2 SIGNAL INTEGRATION CYCLE

The auto-zero loop is opened and the internal differen­tial inputs connect to +IN and -IN. The differentialinput
signal is integrated for a fixed time period. The TC826
signal integration period is 20 clock periods or counts.
The externally set clock frequency is divided by 32
before clocking the internal counters. The integration
time period is:

EQUATION 4-1:

Where:

T

= External Clock Frequency

F

OSC

32

=

SI

F

OSC

x20

+Input

Analog

Common

-INPUT

R

INT

INT

C

AZ

Integrator

–

+

V

DD

1µA

C

INT

11

+

–

Comparator

AZ

–

+

V

DD

8

CMPTR

V

DD

To Digital Section

≈ 6.3V

REF IN

56 7 910

AZ

3

INT

AZ

2

4

From
Digital
Control
Center

Analog Switch

C

REF

TC826

DE- DE+

DE+ DE-

AZ
INT
DE+
DE-

≈ VDD – 2.9V

AZ

–

+

Buffer

INT

DS21477B-page 8

≈ V

DD

12



2002 Microchip TechnologyInc.

TC826

The differential input voltage must be within the device
Common mode range 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 s upply common, -IN should be
tiedto analog common. This is the usual connectionfor
batteryoperated systems. Polarity isdetermined at the
end of signal integrate signal phase. The sign bit is a
true polarity i ndication, in that signals less than 1LSB
are correctly determined. This allows precision null
detection limited only by device noise and system

4.1.3 REF ERENCE INTEGRATE CYCLE

The final phase is reference i ntegrate or de-integrate.

-IN is internally connected to analog common and +IN
is connected with the correct polarity to cause the inte­gratoroutputto return to zero. The timerequiredforthe
output to return to zero is proportional to the input sig­nal and is between0 and 40 counts. The digitalreading
displayed is:

EQUATION 4-2:

noise.

FIGURE 4-2: CONVERSION HAS THREE PHASES

Auto-Zero Phase (AZ) Signal Integrate

Integrator
Output

Analog Common
Potential

Internal
System
Clock (FSYS)

Phase (SI)

V

20 =

Reference Integrate Phase (RI)

True Zero
Crossing

(De-integrate)

Sign Bit Determined

Zero Crossing
Detected

IN

V

REF

Internal Data
Latch Update
Signal

T

I

19 Counts

Minimum

One Conversion Cycle = 80 Counts (T

20

Counts

TD ≈ V

IN

CONV

Number of Counts
Proportional to
VIN

41 Counts

Maximum

= 80 X

FSYS

1

)



2002 Microchip TechnologyInc. DS21477B-page 9

TC826

4.2 System Timing

The oscillator frequency is divided by 32 prior to clock­ing the internal counters. The three-phase measure­ment cycle takes a total of 80 clock pulses. The 80
count cycle is independent of input signal magnitude.

Each phase of the measurement cycle has the follow­ing length:

• Auto-Zero Phase: 19 to 59 Counts
For signals less than full scale, the auto-zero is
assignedtheunusedreference integrate time period.

• Signal Integrate: 20 Counts
This time period is fixed. The integration period is:

EQUATION 4-3:





TSI=20

WhereF

is the externally set clock frequency.

OSC

• Reference Integrate: 0 to 41 Counts

32

F





OSC

4.3 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).

TABLE 4-1:

Required Full Scale Voltage V

20mV 10mV

2V 1V

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.Inapplicationswhereanexternally generatedrefer­ence voltage is desired, refer to Figure 4-3.

The reference voltageis adjustedwith a near full scale
input signal. Adjust for proper LCD display read out.

FIGURE 4-3: EXTERNAL REF ERENCE

V+

REF

4.4 Components Value Selection

4.4.1 I NTE GRATING RESISTOR (R

The desired full scale i nput voltage and output current
capabilityofthe input buffer and integratoramplifierset
the integration resistor v alue. The internal class A out­put stage amplifiers will supply a 1µA drive current with
minimal linearity error. R

is easily calculated for a

INT

1µA full scale current:

EQUATION 4-4:

R

Full Scale Voltage(V)

=

INT

1x10–6

Where VFS= Full Scale Analog Input

V

=

1x10–6

4.4.2 INTEGRATING CAPACITOR (C

The integrating capacitor should be selected to maxi­mize integratoroutput swing. The integrator output will
swingtowithin0.4VofV

+orVS- without saturating.

S

The integrating capacitor is easily calculated:

EQUATION 4-5:

V

Where: V

INT

= IntegratorSwing

INT

= Oscillator Fr equency

F

OSC



R

INT



FS

=

C

640

F

OSCxVINT




The integrating capacitor should be selected for low
dielectricabsorption to prevent rollover errors.Polypro­pylene capacitors are suggested.

4.4.3 AUTO-ZERO CAPACITOR (CAZ)

CAZshould be 2-3 times larger than the integration
capacitor.Apolypropylene capacitorissuggested. Typ­ical values from 0.14µF to 0.068µFaresatisfactory.

4.4.4 REFERENCE CAPACITOR (C

A1µF capacitoris suggested. Low leakage capacitors,
such as polypropylene, are recommended.

Several capacitor/resistor combinations for common
full scale input conditionsare given in Table 4-2.

FS

INT

INT

REF

)

)

)

8

V+

TC826

REF IN

ANALOG

COMMON

(b)

DS21477B-page 10

MCP1525

5

2

1µF

2.50V
Reference



2002 Microchip TechnologyInc.

TC826

TABLE 4-2: SUGGESTED COMPONENT

VALUES

2mV

Comp.2VFull Scale

R

INT

C

INT

C

REF

C

AZ

R

OSC

Note: Approximately 5 conversions/second.

V

≈ 1V

REF

2MΩ 200kΩ 20kΩ

0.033µF0.033µF0.033µF
1µF1µF1µF

0.068µF0.068µF1.14µF

430kΩ 430kΩ 430kΩ

Full Scale

V

≈ 100V

REF

20mV

Full Scale

V

≈ 10V

REF

4.5 Differential Signal Inputs

The TC826 is designed with t rue differential inputs and
accepts input signals within the input stage Common
mode voltage range (V

). The typical range is V+ -1

CM

to V- +1V. Common mode voltages are removed from
the system when the TC826 operates from a battery or
floating power source (isolated from measured sys­tem) and -IN is connectedto analog common (V

COM

).

In systems where Common mode rejection ratio mini­mizes error. Common mode voltages do, however,
affect the integrator output level. Integrator output sat­uration must be prevented. A worse case condition
exists if a l arge positive V

exists in conjunction with

CM

a full scale negative differential signal. The negative
signal drives the integrator output positive along with
V

. For suchapplications,theintegratoroutput swing

CM

can be reduced below the recommended 2V f ull scale
swing. The integrator output will swing within 0.3V of
V

or VSSwithout increased linearity error.

DD

4.6 Digital Section

The TC826 containsall the segment drivers necessary
to drive a liquid crystal display (LCD). An LCD back­plane driver is included. The backplane frequency is
the external clock frequency divided by 256. A 430kΩ
OSC gets the backplane frequency to approximately
55Hz, 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 drive, -POL, is ‘ON’ for negative
analoginputs.If+INand -IN are reversed,this indicator
would reverse.TheTC826 transferfunctionisshownin
Figure 4-4.

FIGURE 4-4: TRANSFER FUNCTION

Over Range

40

39

2

Digital Display

1

-0.5

0

-1-2

0.5

Indication

1 2 3 39 39.5 40 40.5

Analog Input

V

FS

)

(X

40

4.7 BAR/DOT Input (Pin 6 1)

The BAR/DOT input allows the user to select the dis­play format. The TC826 powers up in the BAR mode.
SelecttheDOTdisplayf ormat by connecting BAR/DOT
to the negative supply (Pin 12) through a 1MΩ resistor.

4.8 HOLD Input (Pin 62)

The TC826 data output latches are not updated at the
end of each conversion if HOLD

is tied to the negative
supply (Pin 12) through a 1MΩ resistor. The LCD dis­play continuously displays the previous conversion
results.

The HOLD

pin is normally pulled high by an internal

pull-up.

4.9 TEST Input (Pin 63)

The TC826 enters a Test mode with the TEST input
connectedtothenegativesupply(Pin12).The connec­tion must be made through a 1MΩ resistor. The TEST
input is normally internally pulled high. A low input sets
the output data latch to al l ones. The BAR Display
mode is set. The 41 LCD output segments (zero plus
40 datasegments)andoverr ange annunciator flashon
and off at 1/4 the conversion rate. The polarity annun­ciator (POL-) segment will be on, but not flashing.

4.10 Over Range 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 segmentsand the
overrangeannunciator,OR,willf lash ON and OFF.The
flashrateisonfourththeconversionrate(F

IntheDOTDisplaymode,ORflashesandallotherdata
segment drivers are off.

OSC

/2560).



2002 Microchip TechnologyInc. DS21477B-page 11

TC826

4.11 Polarity Indication (POL-, Pin 60)

The TC826 converts and displaysdata for positive and
negative input signals. The POL LCD segment driver
(Pin 60) is active for negative signals.

4.12 Oscillator Operation

The TC826 external oscillator f requency, F
by resistor R

connected between pins 13 and 14.

OSC

The oscillator frequency versus resistance curve is
shown in Figure 4-5.

FIGURE 4-5: OSCILLATOR

FREQUENCY VS. R

20

50

R

OSC

TA = 25°C

to VSS = 9V

V

DD

(X 100kΩ)

18

16

40

14

12

30

(kHz)

10

8

20

OSC

F

6

CONV (CONV/SEC)

4

10

2

0

0

0

2468101214161820

OSC

,isset

OSC

FIGURE 4-6: EXTERNAL OSCILLATOR

CONNECTION

8

9V

A. Single 9V Supply

V

DD

8

TC826

V

SS

B. Dual Supply

13

12

TC826

12 13

0.1µf

OSC114OSC2

0.1µf

External

Oscillator

Oscillator

VDD = 5V

Power
Supply

= 5V

V

SS

F

is divided by 32 to provide an internal system

OSC

clock, FYSY. Each conversion requires 80 internal
clock cycles. The internal system clock is di vided by 8
to provide the LCD backplanedrivefrequency.The dis­play flash rate duringan input out-of-range signal is set
by dividing FSYS by 320.

The internal oscillator may be bypassed by driving
OSC1 (Pin 13) with an externalsignalgenerator.OSC2
(Pin 14) should be leftunconnected.

The oscillator should swing from V

to VSSin single

DD

supplyoperation(Figure 4-6). In dualsupply operation,
the signal should swing from power supply ground to
V

.

DD

4.13 LCD Display Format

The input signal can be displayed i n two formats
(Figure4-7). The BAR/DOT
format. The TC826 measurement cycle operates
identically for either mode.

FIGURE 4-7: DISPLAY OPTION

A. BAR Mode

1. Input = 0

Bar 4 Off Off
Bar 3
Bar 2
Bar 1
Bar 0

B. DOT Mode

1. Input = 0

Bar 4
Bar 3
Bar 2
Bar 1
Bar 0

input (Pin 61) selects the

FORMATS

2. Input = 5%
of Full Scale

Off Off
Off On
Off On
On

2. Input = 5%
of Full Scale

Off
Off
Off
Off
On

On

Off
Off
On
Off
Off

DS21477B-page 12



2002 Microchip TechnologyInc.

TC826

4.14 BAR Format

The TC826 powers up in the BAR mode. BAR/DOT is
pulled high internally. This displayformat is similar to a
thermometer display. All bars/LCD segments including
zero, below the bar/LCD segment equaling the input
signal level, are on. A half scale input signal,for exam­ple, would be displayed with BAR 0 to BAR 20 on.

4.15 DOT Format

By connecting BAR/DOT to VSSthrough a 1MΩ resis­tor,the DOT mode is selected. Only the BAR LCD seg­ment equaling the input signal is on. The zero segment
is on for zero input.

This mode is useful for moving cursor or ‘needle’ appli­cations.

4.16 LCD Displays

Most end products will use a custom LCD display for
finalproduction.Custom LCD displays are low cost and
availablefromallmanufacturers. The TC826 interfaces
to non-multiplexed LCD displays.A backplane driver is
included on-chip.

To speed initial evaluation and prototype work, a stan­dard TC826 LCD display is available from Varitronix.

Varitronix Ltd. LCDs
4/F Liven House
61-63 King Yip Street
Kwun Tong, Kowloon
Hong Kong
Tel: [phone]
Fax: [phone]

USA Office:
VL El ectronics / Varitronix
3250 Wilshire Blvd., Suite 901
Los Angeles, CA 90010
Tel: [phone]
Fax: [phone]

• Part No.: VBG-413-DP
Other standard LCD displays suitable for development

work are available in both l inear and circular formats.
One m anufacturer is:

UCE Inc.
24 Fi tch Street
Norwalk, CT 06855
Tel: [phone]

• Part No. 5040: 50 segment circular display with
3-digit numeric scale.

• Part No. 5020: 50 segment linear display.

4.17 LCD Backplane Driver (BP, Pin 15)

Additionaldriveelectronicsare not requiredtointerface
the TC826 to an LCD display. The TC826 has an on­chip backplane generator and driver. The backplane
frequency is:

FBP = F

Figure 4-8 gives typical backplane driver rise/fall time
versus backplane capacitance.

OSC

/256

FIGURE 4-8: BACKPLANE DRIVE RISE/

FALL TIME VS.
CAPACITANCE

10

TA = 25°C

9

V

= 9V

S

8

7

6

5

4

3

2

Rise/Fall Time (X 100ns)

1

0 12345678010

Backplane Capacitance (X 100pf)

4.18 Flat Package Socket

Sockets suitable for prototype work are available. A
USA source is:

Nepenthe Distribution
2471 East Bayshore, Suite 520
Palo Alto, CA 94303
Tel: [phone]
T elex: 910/373-2060

• ‘BQ’ Socket Part No.: IC51-064-042 BQ



2002 Microchip TechnologyInc. DS21477B-page 13

TC826

)

5.0 PACKAGING INFORMATION

5.1 Package Marking Information

Package marking data not available at this time.

5.2 Taping Form

Component Taping Orientation for 64-Pin PQFP Devices

User Direction of Feed

PIN 1

W

Carrier Tape, Number of Components Per Reel and Reel Size

Package Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size

64-Pin PQFP 32 mm 24 mm 250 13 in

Note: Drawing does not represent total number of pins.

5.3 Package Dimensions

64-Pin PQFP

PIN 1

.018 (0.45)
.012 (0.30)

.031 (0.80) TYP.

P

Standard Reel Component Orientation
for TR Suffix Device

.009 (0.23)
.005 (0.13)

.555 (14.10)
.547 (13.90)

.687 (17.45)
.667 (16.95)

7° MAX.

.041 (1.03)
.031 (0.78)

DS21477B-page 14

.555 (14.10)
.547 (13.90)

.687 (17.45)
.667 (16.95)

.010 (0.25) TYP.

.120 (3.05)
.100 (2.55)

.130 (3.30) MAX.

Dimensions: mm (inches



2002 Microchip TechnologyInc.

NOTES:

TC826



2002 Microchip TechnologyInc. DS21477B-page 15

TC826

SALES AND SUPPORT

Data Sheets

Products supportedby a preliminaryData Sheet may have an errata sheet describing minor operational differences and recom­mendedworkarounds.To determine if an erratasheetexists for a particular device,please contact one of the following:

1. Your local Microchip sales office

2. The Microchip Corporate LiteratureCenter U.S. FAX:[phone]

3. The Microchip Worldwide Site (www.microchip.com)
Pleasespecify which device, revision of silicon and Data Sheet (includeLiterature#) you are using.

New Customer Notification System

Register on our web site (www.microchip.com/cn) to r eceive the most current information on our products.

DS21477B-page 16



2002 Microchip TechnologyInc.

TC826

Information contained in this publication regarding device
applications and the like is intended through suggestion only
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
No representation or warranty is given and no liability is
assumed by Microchip Technology Incorporated with respect
to the accuracy or use of such information,or infringement of
patents or other intellectual property rights arising from such
use or otherwise. Use of Microchip’s products as critical com­ponents in life support systems is not authorized except with
express written approval by Microchip. No licenses are con­veyed, implicitly or otherwise, under any intellectual property
rights.

Trademarks

The Microchip name and logo, the Microchip logo, FilterLa b,
K

EELOQ,microID,MPLAB,PIC,PICmicro,PICMASTER,

PICSTART, PRO MATE, SEEVAL and The Embedded Control
SolutionsCompany areregiste red trademarksof MicrochipTech­nologyIncorp or ated in the U.S.A. and other countries .

dsPIC, ECONOMONITOR, Fa nSense, FlexROM, fuzzyLAB,
In-Circuit Serial Programming, ICSP, ICEPIC, microPort,
Migratable Memory, MPASM, MPLIB, MPLINK, MPSIM,
MXDEV, PICC, PICDEM, PICDE M.net, rfPIC, Select M ode
and TotalEndurancearetrademarksofMicrochipTechnology
Incorporated in the U.S.A.

Serialized Quick Turn Programming (SQTP) is a service mark
of Microchip TechnologyIncorporated in t he U.S.A.

All other trademarks mentioned herein are property of their
respective companies.

© 2002, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.

Printed on recycled paper.

Microchip received QS-9000 quality system
certification for its worldwide headquarters,
design and wafer fabrication facilities in
Chandler and Tempe, Arizona in July 1999
and Mountain View, California in March 2002.
The Company’s quality system processes and
procedures are QS-9000 compliant for its

®

PICmicro
devices, Serial EEPROMs, microperipherals,
non-volatile memory and analog products. In
addition, Microchip’s quality system for the
design and manufacture of development
systemsisISO 9001certified.



2002 Microchip TechnologyInc. DS21477B-page 17

8-bit MCUs, KEELOQ®code hopping

WORLDWIDE SALES AND SERVICE

AMERICAS

Corporate Office

2355 West Chandler Blvd.
Chandler, AZ 85224-6199
Tel: [phone] Fax: [phone]
Technical Support: 480-792-7627
Web Address: http://www.microchip.com

Rocky Mountain

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Tel: [phone] Fax: [phone]

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Detroit

Tri-Atria Office Building
32255 Northwestern Highway, Suite 190
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Los Angeles

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New York

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San Jose

Microchip Technology Inc.
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6285 Northam Drive, Suite 108
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ASIA/PACIFIC

Australia

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Tel: [phone] Fax: [phone]

China - Beijing

Microchip Technology Consulting (Shanghai)
Co., Ltd., Beijing Liaison Office
Unit 915
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Tel: [phone] Fax: [phone]

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Rm. 2401, 24th Floor,
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China - Shanghai

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Korea

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Singapore

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Taiwan

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Denmark

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Germany

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Italy

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Tel: [phone] Fax: [phone]

United Kingdom

Arizona Microchip Technology Ltd.
505 Eskdale Road
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Wokingham
Berkshire, EnglandRG41 5TU
Tel: [phone] Fax: [phone]

03/01/02

DS21477B-page 18

*DS21477B*



2002 Microchip Technology Inc.