3 1/2 Digit Analog-to-Digital Converters with Hold

2002 Microchip Technology Inc.

DS21457B-page 1

TC7116/A/TC7117/A

Features

· Low Temperature Drift Internal Reference

- TC7116/TC7117 80 ppm/°C Typ.

- TC7116A/TC7117A 20 ppm/°C Typ.

· Display Hold Function

· Directly Drives LCD or LED Display

· Zero Reading with Zero Input

· Low Noise for Stable Display

- 2V or 200mV Full Scale Range (FSR)

· Auto-Zero Cycle Eliminates Need for Zero

· Adjustment Potentiometer

· True Polarity Indication for Precision Null

Applications

· Convenient 9V Battery Operation:

(TC7116/TC7116A)

· High Impedance CMOS Differential Inputs: 10

· Low Power Operation: 10mW

Applications

· Thermometry

· Bridge Readouts: Strain Gauges, Load Cells,

Null Detectors

· Digital Meters: Voltage/Current/Ohms/Power, pH

· Digital Scales, Process Monitors

· Portable Instrumentation

Device Selection Table

General Description

The TC7116A/TC7117A are 3-1/2 digit CMOS analog-
to-digital converters (ADCs) containing all the active
components necessary to construct a 0.05% resolution
measurement

system.

Seven-segment

decoders,

polarity and digit drivers, voltage reference, and clock
circuit are integrated on-chip. The TC7116A drives liq-
uid crystal displays (LCDs) and includes a backplane
driver. The TC7117A drives common anode light emit-
ting diode (LED) displays directly with an 8mA drive
current per segment.

These devices incorporate a display hold (HLDR) func-
tion. The displayed reading remains indefinitely, as
long as HLDR is held high. Conversions continue, but
output data display latches are not updated. The refer-
ence low input (V

REF

-) is not available, as it is with the

TC7106/7107. V

REF

- is tied internally to analog com-

mon in the TC7116A/7117A devices.

The TC7116A/7117A 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 10

input imped-

ance. The 15

P-P

noise performance enables a "rock

solid" reading. The auto-zero cycle ensures a zero dis-
play reading with a 0V input.

The TC7116A and TC7117A feature a precision, low
drift internal reference, and are functionally identical to
the TC7116/TC7117. A low drift external reference is
not normally required with the TC7116A/TC7117A.

Package Code

Package

Temperature Range

CPL

40-Pin PDIP

C to +70

IJL

40-Pin CERDIP

-25

C to +85

CKW

44-Pin PQFP

C to +70

CLW

44-Pin PLCC

C to +70

3-1/2 Digit Analog-to-Digital Converters with Hold

TC7116/A/TC7117/A

DS21457B-page 2

2002 Microchip Technology Inc.

Package Type

BP/

GND

COMMON

V+

18 19 20 21

23 24

POL

1 44

OSC1

OSC2

OSC3

TEST

REF

25 26 27 28

BUFF

INT

TC7116CLW

TC7116ACLW

TC7117CLW

TC7117ACLW

TC7116CPL

TC7116ACPL

TC7117CPL

TC7117ACPL

V-

REF

BP/

GND

TC7116CKW

TC7116ACKW

TC7117CKW

TC7117ACKW

12 13 14 15

17 18

44 43 42 41

39 38

REF

COMMON

BUFF

INT

V-

19 20 21 22

OSC3

TEST

HLDR

OSC2

OSC1

V+

REF

POL

40-Pin PDIP

40-Pin CERDIP

44-Pin PLCC

44-Pin PQFP

OSC1

TEST

REF

COMMON

HLDR

(Minus Sign)

10's

100's

1000's

(TC7116/7117)
(TC7116A/TC7117A)

100's

OSC2

OSC3

V+

REF

BUFF

INT

V-

BP/GND

POL

1's

HLDR

TC7116IJL

TC7116AIJL

TC7117IJL

TC7117AIJL

OSC1

TEST

REF

COMMON

HLDR

10's

100's

1000's

100's

OSC2

OSC3

V+

REF

BUFF

INT

V-

BP/GND

POL

1's

Note

1: NC = No internal connection.
2: Pins 9, 25, 40 and 56 are connected to the die substrate. The potential at these pins is approximately V+. No external

connections should be made.

TC7116/A/TC7117/A

DS21457B-page 4

2002 Microchip Technology Inc.

1.0

ELECTRICAL
CHARACTERISTICS

Absolute Maximum Ratings*

Supply Voltage:

TC7116/TC7116A (V+ to V-) ........................... 15V

TC7117/TC7117A (V+ to GND) .......................+6V

V- to GND.........................................................-9V

Analog Input Voltage (Either Input) (Note 1) ... V+ to V-

Reference Input Voltage (Either Input) ............ V+ to V-

Clock Input:

TC7116/TC7116A............................... TEST to V+

TC7117/TC7117A.................................GND to V+

Package Power Dissipation; T

70°C (Note 2)

40-Pin CDIP ................................................2.29W

40-Pin PDIP ................................................1.23W

44-Pin PLCC ...............................................1.23W

44-Pin PQFP ...............................................1.00W

Operating Temperature:

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

I (Commercial) Device.................... 0°C to +70°C

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

*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 affect device reliability.

TC7116/A AND TC7117/A ELECTRICAL SPECIFICATIONS

Electrical Characteristics: Unless otherwise noted, specifications apply to both the TC7116/A and TC7117/A at T

= 25°C,

CLOCK

= 48kHz. Parts are tested in the circuit of the Typical Operating Circuit.

Symbol

Parameter

Min

Typ

Max

Unit

Test Conditions

Zero Input Reading

±0

Digital

Reading

= 0V

Full Scale = 200mV

Ratiometric Reading

999

999/1000

1000

Digital

Reading

= V

REF

= 100mV

R/O

Rollover Error (Difference in Reading for
Equal Positive and Negative
Readings Near Full Scale)

-1

±0.2

Counts

- = + V

200mV

Linearity (Maximum Deviation from Best
Straight Line Fit)

-1

±0.2

Counts

Full Scale = 200mV or 2V

CMRR

Common Mode Rejection Ratio
(Note 3)

V/V

= ±1V, V

= 0V

Full Scale = 200mV

Noise (Peak to Peak 95% of Time)

= 0V

Full Scale = 200mV

Leakage Current at Input

= 0V

Zero Reading Drift

0.2

V/°C

= 0V

"C" Device = 0°C to +70°C

1.0

V/°C

"I" Device = -25°C to +85°C

Note

Input voltages may exceed the supply voltages provided the input current is limited to ±100

Dissipation rating assumes device is mounted with all leads soldered to printed circuit board.

Refer to "Differential Input" discussion.

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.

The TC7116/TC7116A logic inputs have an internal pull-down resistor connected from HLDR, Pin 1 to TEST, Pin 37. The
TC7117/TC7117A logic inputs have an internal pull-down resistor connected from HLDR, Pin 1 to GND, Pin 21.

2002 Microchip Technology Inc.

DS21457B-page 5

TC7116/A/TC7117/A

Scale Factor Temperature Coefficient

ppm/°C

= 199mV,

"C" Device = 0°C to +70°C
(Ext. Ref = 0ppm°C)

ppm/°C

"I" Device = -25°C to +85°C

Input Resistance, Pin 1

(Note 5)

IL,

Pin 1

Test + 1.5

TC7116/A Only

IL,

Pin 1

GND + 1.5

TC7117/A Only

IH,

Pin 1

- 1.5

Both

Supply Current (Does not Include LED
Current for TC7117/A)

0.8

1.8

= 0V

Analog Common Voltage
(with Respect to Positive Supply)

2.4

3.05

3.35

25k

Between Common

and Positive Supply

CTC

Temperature Coefficient of Analog
Common (with Respect to Positive
Supply)

20
80

--
50
--

ppm/°C
ppm/°C

"C" Device: 0°C to

+70°C

TC7116A/TC7117A
TC7116/TC7117

TC7116/TC7117A ONLY Peak to Peak
Segment Drive Voltage

V+ to V- = 9V
(Note 4)

TC7116A/TC7116A ONLY Peak to Peak
Backplane Drive Voltage

V+ to V- = 9V
(Note 4)

TC7117/TC7117A ONLY
Segment Sinking Current
(Except Pin 19)

V+ = 5.0V
Segment Voltage = 3V

TC7117/TC7117A ONLY
Segment Sinking Current (Pin 19 Only)

V+ = 5.0V
Segment Voltage = 3V

TC7116/A AND TC7117/A ELECTRICAL SPECIFICATIONS (CONTINUED)

Electrical Characteristics: Unless otherwise noted, specifications apply to both the TC7116/A and TC7117/A at T

= 25°C,

CLOCK

= 48kHz. Parts are tested in the circuit of the Typical Operating Circuit.

Symbol

Parameter

Min

Typ

Max

Unit

Test Conditions

Note

Input voltages may exceed the supply voltages provided the input current is limited to ±100

Dissipation rating assumes device is mounted with all leads soldered to printed circuit board.

Refer to "Differential Input" discussion.

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.

TC7116/A/TC7117/A

DS21457B-page 6

2002 Microchip Technology Inc.

2.0

PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 2-1.

TABLE 2-1:

PIN FUNCTION TABLE

Pin Number

(40-Pin PDIP)

(40-Pin CERDIP)

Pin Number

(44-Pin PQFP)

Symbol

Description

HLDR

Hold pin, Logic 1 holds present display reading.

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.

POL

Activates the negative polarity display.

BP/

GND

LCD backplane drive output (TC7116/TC7116A). Digital ground
(TC7117/TC7117A).

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.

V-

Negative power supply voltage.

INT

Integrator output. Connection point for integration capacitor.
See Section 4.3, Integrating Capacitor for more details.

BUFF

Integration resistor connection. Use a 47k

resistor for a 200mV full scale range

and a 470k

resistor for 2V full scale range.

The size of the auto-zero capacitor influences system noise. Use a 0.47

capacitor for 200mV full scale, and a 0.047

F capacitor for 2V full scale.

See Section 4.1, 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.

COMMON 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 Section 3.1.6, Analog Common
for more details.

REF

See Pin 34.

REF

A 0.1

F capacitor is used in most applications. If a large Common mode voltage

exists (for example, the V

- pin is not at analog common), and a 200mV scale is

used, a 1

F capacitor is recommended and will hold the rollover error to

0.5 count.

2002 Microchip Technology Inc.

DS21457B-page 7

TC7116/A/TC7117/A

3.0

DETAILED DESCRIPTION

(All Pin Designations Refer to 40-Pin PDIP.)

3.1

Analog Section

Figure 3-1 shows the block diagram of the analog sec-
tion for the TC7116/TC7116A and TC7117/TC7117A.
Each measurement cycle is divided into three phases:
(1) Auto-Zero (AZ), (2) Signal Integrate (INT), and
(3) Reference Integrate (REF), or De-integrate (DE).

3.1.1

AUTO-ZERO PHASE

High and low inputs are disconnected from the pins and
internally shorted to analog common. The reference
capacitor is charged to the reference voltage. A feed-
back loop is closed around the system to charge the
auto-zero capacitor (C

) to compensate for offset volt-

ages in the buffer amplifier, integrator, and comparator.
Since the comparator is included in the loop, AZ accu-
racy is limited only by system noise. The offset referred
to the input is less than 10

3.1.2

SIGNAL INTEGRATE PHASE

The auto-zero loop is opened, the internal short is
removed, and the internal high and low inputs are con-
nected to the external pins. The converter then inte-
grates the differential voltages between V

+ and V

for a fixed time. This differential voltage can be within a
wide Common mode range: 1V of either supply. How-
ever, if the input signal has no return with respect to the
converter power supply, V

- can be tied to analog

common to establish the correct Common mode volt-
age. At the end of this phase, the polarity of the
integrated signal is determined

V+

Positive Power Supply Voltage.

REF

The analog input required to generate a full scale output (1999 counts). Place
100mV between Pins 32 and 36 for 199.9mV full scale. Place 1V between
Pins 35 and 36 for 2V full scale. See Section 4.6, Reference Voltage.

TEST

Lamp test. When pulled HIGH (to V+), all segments will be turned on and the dis-
play should read -1888. It may also be used as a negative supply for externally
generated decimal points. See Section 3.1.7, TEST for additional information.

OSC3

See Pin 40.

OSC2

See Pin 40.

OSC1

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 capaci-

tor. The 100k

resistor is tied to Pin 39 and the 100pF capacitor is tied to Pin 38.

TABLE 2-1:

PIN FUNCTION TABLE (CONTINUED)

Pin Number

(40-Pin PDIP)

(40-Pin CERDIP)

Pin Number

(44-Pin PQFP)

Symbol

Description

TC7116/A/TC7117/A

DS21457B-page 8

2002 Microchip Technology Inc.

FIGURE 3-1:

ANALOG SECTION OF TC7116/TC7117A AND TC7117/TC7117A

3.1.3

REFERENCE INTEGRATE PHASE

The final phase is reference integrate, or de-integrate.
Input low is internally connected to analog common
and input high 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. The digital
reading displayed is:

EQUATION 3-1:

3.1.4

REFERENCE

The positive reference voltage (V

REF

+) is referred to

analog common.

3.1.5

DIFFERENTIAL INPUT

This input can accept differential voltages anywhere
within the Common mode range of the input amplifier
or, specifically, from 1V below the positive supply to 1V
above the negative supply. In this range, the system
has a CMRR of 86dB, typical. However, since the inte-
grator also swings with the Common mode voltage,
care must be exercised to ensure that the integrator
output does not saturate. A worst case condition would
be a large, positive Common mode voltage with a near
full scale negative differential input voltage. The nega-
tive input signal drives the integrator positive, when
most of its swing has been used up by the positive
Common mode voltage. For these critical applications,
the integrator swing can be reduced to less than the
recommended 2V full scale swing with little loss of
accuracy. The integrator output can swing within 0.3V
of either supply without loss of linearity.

3.1.6

ANALOG COMMON

This pin is included primarily to set the Common mode
voltage for battery operation (TC7116/TC7116A), or for
any system where the input signals are floating, with
respect to the power supply. The analog common pin
sets a voltage approximately 2.8V more negative than
the positive supply. This is selected to give a minimum
end of life battery voltage of about 6V. However, analog
common has some attributes of a reference voltage.
When the total supply voltage is large enough to cause
the zener to regulate (>7V), the analog common volt-
age will have a low voltage coefficient (0.001%), low
output impedance (

), and a temperature coeffi-

cient of less than 20ppm/°C, typically, and 50 ppm max-
imum. The TC7116/TC7117 temperature coefficients
are typically 80ppm/°C.

An external reference may be used, if necessary, as
shown in Figure 3-2.

FIGURE 3-2:

USING AN EXTERNAL
REFERENCE

TC7116

TC7116A

TC7117

TC7117A

REF

INT

V+

Auto-Zero

INT

µA

INT

AZ & DE (±)

INT

Integrator

V+ -3V

Comparator

Digital

Section

DE (+)

()

DE
(+)

DE ()

V+

Analog

Common

BUFF

INT

REF

Low

Temp.

Drift

Zener

REF

V-

1000 =

REF

V+

1.2V REF

COMMON

TC7116

TC7116A

TC7117

TC7117A

6.8k

REF

20k

2002 Microchip Technology Inc.

DS21457B-page 9

TC7116/A/TC7117/A

Analog common is also used as V

- return during

auto-zero and de-integrate. If V

- is different from ana-

log common, a Common mode voltage exists in the
system and is taken care of by the excellent CMRR of
the converter. However, in some applications, V

- will

be set at a fixed, known voltage (power supply common
for instance). In this application, analog common
should be tied to the same point, thus removing the
Common mode voltage from the converter. The same
holds true for the reference voltage; if it can be conve-
niently referenced to analog common, it should be.
This removes the Common mode voltage from the
reference system.

Within the IC, analog common is tied to an N-channel
FET, that can sink 30mA or more of current to hold the
voltage 3V below the positive supply (when a load is
trying to pull the analog common line positive). How-
ever, there is only 10

A of source current, so analog

common may easily be tied to a more negative voltage,
thus overriding the internal reference.

3.1.7

TEST

The TEST pin serves two functions. On the TC7117/
TC7117A, it is coupled to the internally generated digi-
tal supply through a 500

resistor. Thus, it can be used

as a negative supply for externally generated segment
drivers, such as decimal points, or any other presenta-
tion the user may want to include on the LCD.
(Figure 3-3 and Figure 3-4 show such an application.)
No more than a 1mA load should be applied.

The second function is a "lamp test." When TEST is
pulled HIGH (to V+), all segments will be turned ON
and the display should read -1888. The TEST pin will
sink about 10mA under these conditions.

FIGURE 3-3:

SIMPLE INVERTER FOR
FIXED DECIMAL POINT

FIGURE 3-4:

EXCLUSIVE "OR" GATE
FOR DECIMAL POINT
DRIVE

3.2

Digital Section

Figure 3-5 and Figure 3-6 show the digital section for
TC7116/TC7116A and TC7117/TC7117A, respectively.
For the TC7116/TC7116A (Figure 3-5), an internal dig-
ital ground is generated from a 6V zener diode and a
large P-channel source follower. This supply is made
stiff to absorb the relative large capacitive currents
when the backplane (BP) voltage is switched. The BP
frequency is the clock frequency 4800. For 3 readings
per second, this is a 60Hz square wave with a nominal
amplitude of 5V. The segments are driven at the same
frequency and amplitude, and are in phase with BP
when OFF, but out of phase when ON. In all cases,
negligible DC voltage exists across the segments.

Figure 3-6 is the digital section of the TC7117/
TC7117A. It is identical to the TC7116/TC7116A,
except that the regulated supply and BP 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. The
TC7117/TC7117A are designed to drive common
anode LED displays.

In both devices, the polarity indication is ON for analog
inputs. If V

- and V

+ are reversed, this indication can

be reversed also, if desired.

TC7116

TC7116A

TEST

V+

GND

To LCD

Decimal

Point

To LCD

Backplane

4049

TC7116

TC7116A

Decimal

Point

Select

V+

TEST

GND

4030

To LCD
Decimal
Point

TC7116/A/TC7117/A

DS21457B-page 10

2002 Microchip Technology Inc.

FIGURE 3-5:

TC7116/TC7116A DIGITAL SECTION

3.2.1

SYSTEM TIMING

The clocking method used for the TC7116/TC7116A
and TC7117/TC7117A is shown in Figure 3-6. Three
clocking methods may be used:

An external oscillator connected to Pin 40.

A crystal between Pins 39 and 40.

An RC network using all three pins.

The oscillator frequency is

4 before it clocks the

decade counters. It is then further divided to form the
three convert cycle phases: Signal Integrate (1000
counts), Reference De-integrate (0 to 2000 counts),
and Auto-Zero (1000 to 3000 counts). For signals less
than full scale, auto-zero gets the unused portion of ref-
erence de-integrate. This makes a complete measure
cycle of 4000 (16,000 clock pulses), independent of
input voltage. For 3 readings per second, an oscillator
frequency of 48kHz would be used.

To achieve maximum rejection of 60Hz pickup, the sig-
nal integrate cycle should be a multiple of 60Hz. Oscil-
lator frequencies of 240kHz, 120kHz, 80kHz, 60kHz,
48kHz, 40kHz, etc. should be selected. For 50Hz rejec-
tion,

oscillator

frequencies

200kHz,

100kHz,

66-2/3kHz, 50kHz, 40kHz, etc. would be suitable. Note
that 40kHz (2.5 readings per second) will reject both
50Hz and 60Hz.

3.2.2

HOLD READING INPUT

When HLDR is at a logic HIGH, the latch will not be
updated. Analog-to-digital conversions will continue,
but will not be updated until HLDR is returned to LOW.
To continuously update the display, connect to TEST
(TC7116/TC7116A) or GROUND (TC7117/TC7117A),
or disconnect. This input is CMOS compatible with
70k

typical resistance to TEST (TC7116/TC7116A) or

GROUND (TC7117/TC7117A).

TC7116

TC7116A

LCD Phase Driver

Thousands

Hundreds

Tens

Units

Backplane

OSC2

Internal Digital Ground

V+

V-

TEST

6.2V

500

To Switch Drivers

From Comparator Output

Clock

= 1V

7-Segment

Decode

7-Segment

Decode

7-Segment

Decode

200

Typical Segment Output

Internal Digital Ground

Segment

Output

V+

0.5mA

2mA

Latch

OSC3

OSC1

HLDR

~70k

Logic Control

TC7116/A/TC7117/A

DS21457B-page 12

2002 Microchip Technology Inc.

4.0

COMPONENT VALUE
SELECTION

4.1

Auto-Zero Capacitor

The size of the auto-zero capacitor has some influence
on system noise. For 200mV full scale, where noise is
very important, a 0.47

F capacitor is recommended.

On the 2V scale, a 0.047

F capacitor increases the

speed of recovery from overload and is adequate for
noise on this scale.

4.2

Reference Capacitor

A 0.1

F capacitor is acceptable in most applications.

However, where a large Common mode voltage exists
(i.e., the V

- pin is not at analog common), and a

200mV scale is used, a larger value is required to pre-
vent rollover error. Generally, 1

F will hold the rollover

error to 0.5 count in this instance.

4.3

Integrating Capacitor

The integrating capacitor should be selected to give the
maximum voltage swing that ensures tolerance buildup
will not saturate the integrator swing (approximately
0.3V from either supply). In the TC7116/TC7116A or
the TC7117/TC7117A, when the analog common is
used as a reference, a nominal ±2V full scale integrator
swing is acceptable. For the TC7117/TC7117A, with
±5V supplies and analog common tied to supply
ground, a ±3.5V to ±4V swing is nominal. For 3 read-
ings per second (48kHz clock), nominal values for C

INT

are 0.22

1F and 0.10

F, respectively. If different oscil-

lator frequencies are used, these values should be
changed in inverse proportion to maintain the output
swing. The integrating capacitor must have low dielec-
tric absorption to prevent rollover errors. Polypropylene
capacitors are recommended for this application.

4.4

Integrating Resistor

Both the buffer amplifier and the integrator have a class
A output stage with 100

A of quiescent current. They

can supply 20

A of drive current with negligible non-

linearity. The integrating resistor should be large
enough to remain in this very linear region over the
input voltage range, but small enough that undue leak-
age requirements are not placed on the PC board. For
2V full scale, 470k

is near optimum and, similarly,

47k

for 200mV full scale.

4.5

Oscillator Components

For all frequency ranges, a 100k

resistor is recom-

mended; the capacitor is selected from the equation:

EQUATION 4-1:

For a 48kHz clock (3 readings per second), C = 100pF.

4.6

Reference Voltage

To generate full scale output (2000 counts), the analog
input requirement is V

= 2V

REF

. Thus, for the 200mV

and 2V scale, V

REF

should equal 100mV and 1V,

respectively. In many applications, where the ADC is
connected to a transducer, a scale factor exists
between the input voltage and the digital reading. For
instance, in a measuring system, the designer might like
to have a full scale reading when the voltage from the
transducer is 700mV. Instead of dividing the input down
to 200mV, the designer should use the input voltage
directly and select V

REF

= 350mV. Suitable values for

integrating resistor and capacitor would be 120kW and
0.22

F. This makes the system slightly quieter and also

avoids a divider network on the input. The TC7117/
TC7117A, with ±5V supplies, can accept input signals
up to ±4V. Another advantage of this system is when a
digital reading of zero is desired for V

0. Tempera-

ture and weighing systems with a variable tare are
examples. This offset reading can be conveniently gen-
erated by connecting the voltage transducer between
V

+ and analog common, and the variable (or fixed)

offset voltage between analog common and V

5.0

TC7117/TC7117A POWER
SUPPLIES

The TC7117/TC7117A are designed to operate from
±5V supplies. However, if a negative supply is not avail-
able, it can be generated with a TC7660 DC-to-DC con-
verter and two capacitors. Figure 5-1 shows this
application.

In selected applications, a negative supply is not
required. The conditions for using 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.

FIGURE 5-1:

NEGATIVE POWER
SUPPLY GENERATION
WITH TC7660

0.45

-----------

REF

V+

TC7117

TC7117A

µF

COM

GND

µF

V-

(-5V)

+5V

TC7660

LED
Drive

2002 Microchip Technology Inc.

DS21457B-page 13

TC7116/A/TC7117/A

6.0

TYPICAL APPLICATIONS

The TC7117/TC7117A sink the LED display current,
causing heat to build up in the IC package. If the inter-
nal voltage reference is used, the changing chip tem-
perature can cause the display to change reading. By
reducing the LED common anode voltage, the TC7117/
TC7117A package power dissipation is reduced.

Figure 6-1 is a curve tracer display showing the rela-
tionship between output current and output voltage for
typical TC7117CPL/TC7117ACPL devices. Since a
typical LED has 1.8V across it at 8mA and its common
anode is connected to +5V, the TC7117/TC7117A out-
put is at 3.2V (Point A, Figure 6-1). Maximum power
dissipation is 8.1mA x 3.2V x 24 segments = 622mW.

However, notice that once the TC7117/TC7117A's out-
put voltage is above 2V, the LED current is essentially
constant as output voltage increases. Reducing the
output voltage by 0.7V (Point B Figure 6-1) results in
7.7mA of LED current, only a 5% reduction. Maximum
power dissipation is now only 7.7mA x 2.5V x 24 =
462mW, a reduction of 26%. An output voltage reduc-
tion of 1V (Point C) reduces LED current by 10%
(7.3mA), but power dissipation by 38% (7.3mA x 2.2V
x 24 = 385mW).

FIGURE 6-1:

TC7117/TC7117A OUTPUT
VS. OUTPUT VOLTAGE

Reduced power dissipation is very easy to obtain.
Figure 6-2 shows two ways: either a 5.1

, 1/4W resis-

tor, or a 1A diode placed in series with the display (but
not in series with the TC7117/TC7117A). The resistor
reduces the TC7117/TC7117A's output voltage (when
all 24 segments are ON) to Point C of Figure 6-1. When
segments turn off, the output voltage will increase. The
diode, however, will result in a relatively steady output
voltage, around Point B.

In addition to limiting maximum power dissipation, the
resistor reduces change in power dissipation as the
display changes. The effect is caused by the fact that,
as fewer segments are ON, each ON output drops
more voltage and current. For the best case of six seg-
ments (a "111" display) to worst case (a "1888" display),
the resistor circuit 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 dis-
play brightness remaining steady is very important to
the designer, a diode may be used instead of the
resistor.

FIGURE 6-2:

DIODE OR RESISTOR
LIMITS PACKAGE POWER
DISSIPATION

6.000

7.000

8.000

9.000

10.000

2.00

2.50

3.00

3.50

4.00

Output Voltage (V)

t
put

r
r
ent

(
m

TP2

TP5

100

TP1

24k

0.1

µF

TP3

0.01

µF

0.22

µF

Display

100

+5V

-5V

150k

0.47

µF

TC7117

TC7117A

1N4001

1.5W, 1/4

2002 Microchip Technology Inc.

DS21457B-page 17

TC7116/A/TC7117/A

7.0

PACKAGING INFORMATION

7.1

Package Marking Information

Package marking data not available at this time.

7.2

Taping Form

PIN 1

Component Taping Orientation for 44-Pin PLCC Devices

User Direction of Feed

Standard Reel Component Orientation
for TR Suffix Device

Note: Drawing does not represent total number of pins.

Package

Carrier Width (W)

Pitch (P)

Part Per Full Reel

Reel Size

44-Pin PLCC

32 mm

24 mm

500

13 in

Carrier Tape, Number of Components Per Reel and Reel Size

Component Taping Orientation for 44-Pin PQFP Devices

User Direction of Feed

PIN 1

Standard Reel Component Orientation
for TR Suffix Device

Package

Carrier Width (W)

Pitch (P)

Part Per Full Reel

Reel Size

44-Pin PQFP

24 mm

16 mm

500

13 in

Carrier Tape, Number of Components Per Reel and Reel Size

Note: Drawing does not represent total number of pins.

TC7116/A/TC7117/A

DS21457B-page 20

2002 Microchip Technology Inc.

PRODUCT IDENTIFICATION SYSTEM

To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.

SALES AND SUPPORT

Data Sheets
Products supported by a preliminary Data Sheet may have an errata sheet describing minor operational differences and recom-
mended workarounds. To determine if an errata sheet exists for a particular device, please contact one of the following:

Your local Microchip sales office

The Microchip Corporate Literature Center U.S. FAX: (480) 792-7277

The Microchip Worldwide Site (www.microchip.com)

Please specify which device, revision of silicon and Data Sheet (include Literature #) you are using.

New Customer Notification System
Register on our web site (www.microchip.com/cn) to receive the most current information on our products.

PART CODE

TC711X 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 Device Selection Table)

}

2002 Microchip Technology Inc.

DS21457B-page 21

TC7116/ATC7117/A

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 com-
ponents in life support systems is not authorized except with
express written approval by Microchip. No licenses are con-
veyed, implicitly or otherwise, under any intellectual property
rights.

Trademarks

The Microchip name and logo, the Microchip logo, FilterLab,
K

, microID,

MPLAB, PIC, PICmicro, PICMASTER,

PICSTART, PRO MATE, SEEVAL and The Embedded Control
Solutions Company are registered trademarks of Microchip Tech-
nology Incorporated in the U.S.A. and other countries.

dsPIC, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB,
In-Circuit Serial Programming, ICSP, ICEPIC, microPort,
Migratable Memory, MPASM, MPLIB, MPLINK, MPSIM,
MXDEV, PICC, PICDEM, PICDEM.net, rfPIC, Select Mode
and Total Endurance are trademarks of Microchip Technology
Incorporated in the U.S.A.

Serialized Quick Turn Programming (SQTP) is a service mark
of Microchip Technology Incorporated in the U.S.A.

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

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

8-bit MCUs, K

code hopping

devices, Serial EEPROMs, microperipherals,
non-volatile memory and analog products. In
addition, Microchip's quality system for the
design and manufacture of development
systems is ISO 9001 certified.

DS21457B-page 22

2002 Microchip Technology Inc.

AMERICAS

Corporate Office

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03/01/02

*DS21457B*

ORLDWIDE

ALES

AND

ERVICE

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: TC7117ARCPL

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: TC7117ARCPL