CA3162

A/D Converters for 3-Digit Display

April 2002

Features

Description

Dual Slope A/D Conversion

The CA3162E and CA3162AE are I2L monolithic A/D

converters that provide a 3 digit multiplexed BCD output.
They are used with the CA3161E BCD-to-Seven-Segment
Decoder/Driver and a minimum of external parts to implement a complete 3-digit display. The CA3162AE is identical
to the CA3162E except for an extended operating temperature range.

Multiplexed BCD Display

Ultra Stable Internal Band Gap Voltage Reference
Capable of Reading 99mV Below Ground with Single
Supply
Differential Input

The CA3161E is described in the Display Drivers section of

this data book.

Internal Timing - No External Clock Required

Choice of Low Speed (4Hz) or High Speed (96Hz)
Conversion Rate

Ordering Information

Hold Inhibits Conversion but Maintains Delay

Overrange Indication

PART NUMBER

- EEE for Reading Greater than +999mV, - for

Reading More Negative than -99mV When Used
With CA3161E

TEMP.
RANGE ( oC)

CA3162E

0 to 70

PACKAGE
16 Ld PDIP

PKG.
NO.
E16.3

Pinout
CA3162 (PDIP)
TOP VIEW

21

16 23

20

15 22

NSD

14 V+

MSD

13 GAIN ADJ

LSD

12

HOLD/
BYPASS

11 HIGH INPUT

GND

10 LOW INPUT

ZERO ADJ

BCD
OUTPUTS

DIGIT
SELECT
OUTPUTS

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2002. All Rights Reserved

BCD
OUTPUTS

INTEGRATING
CAP

ZERO ADJ

FN1080.3

CA3162
Functional Block Diagram

V+

V+
BCD OUTPUTS

ZERO
ADJ

INTEGRATING
CAP
8

12

21

20

22

23

V+

15

16

14

3
CONTROL LOGIC
COUNTERS AND MULTIPLEX

DIGIT
DRIVE

DIGIT SELECT
OUTPUTS

HIGH INPUT 11
LOW INPUT 10

THRESHOLD
DET.

V/I
CONVERTER

REFERENCE
CURRENT
GENERATOR

BAND GAP
REFERENCE

13

MSD = MOST SIGNIFICANT DIGIT

NSD = NEXT SIGNIFICANT DIGIT
LSD = LEAST SIGNIFICANT DIGIT

GAIN
ADJ

2048

96

OSC

HOLD/
BYPASS
GATES

GND

= MSD

= LSD

= NSD

CONVERSION
CONTROL

CA3162
Absolute Maximum Ratings

Thermal Information

DC Supply Voltage (Between Pins 7 and 14) . . . . . . . . . . . . . . . +7V

Input Voltage (Pin 10 or 11 to Ground) . . . . . . . . . . . . . . . . . . . 15V

Thermal Resistance (Typical, Note 1)

JA (oC/W)

PDIP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
90
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . 150oC
Maximum Storage Temperature Range . . . . . . . . . . -65oC to 150oC
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300oC

Operating Conditions
Temperature Range
CA3162E. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to 75oC

CAUTION: Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. This is a stress only rating and operation
of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.

NOTE:
1. JA is measured with the component mounted on a low effective thermal conductivity test board in free air. See Tech Brief TB379 for
details..

Electrical Specifications

TA = 25oC, V+ = 5V, Zero Pot Centered, Gain Pot = 2.4k, Unless Otherwise Specified

PARAMETER

TEST CONDITIONS

Operating Supply Voltage Range, V+

Supply Current, I+

100k to V+ on Pins 3, 4, 5

Input Impedance, ZI

MIN

TYP

MAX

UNITS

4.5

5.5

17

mA

100

-80

nA

Input Bias Current, IIB

Pins 10 and 11

Unadjusted Zero Offset

V11-V10 = 0V, Read Decoded Output

-12

+12

mV

Unadjusted Gain

V11-V10 = 900mV, Read Decoded Output

846

954

mV

Linearity

Notes 1 and 2

-1

+1

Count

Slow Mode

Pin 6 = Open or GND

Hz

Fast Mode

Pin 6 = 5V

96

Hz

0.8

1.2

1.6

Conversion Rate

Conversion Control Voltage (Hold Mode)

at Pin 6
Common Mode Input Voltage Range, VICR

Notes 3, 4

-0.2

+0.2

BCD Sink Current at Pins 1, 2, 15, 16

VBCD 0.5V, at Logic Zero State

0.4

1.6

mA

Digit Select Sink Current at Pins 3, 4, 5

VDIGIT Select = 4V at Logic Zero State

1.6

2.5

mA

Zero Temperature Coefficient

VI = 0V, Zero Pot Centered

10

V/oV

Gain Temperature Coefficient

VI = 900mV, Gain Pot = 2.4k

0.005

%/oC

NOTES:
1. Apply 0V across V11 to V10 . Adjust zero potentiometer to give 000mV reading. Apply 900mV to input and adjust gain potentiometer to
give 900mV reading.
2. Linearity is measured as a difference from a straight line drawn through zero and positive full scale. Limits do not include 0.5 count bit
digitizing error.
3. For applications where low input pin 10 is not operated at pin 7 potential, a return path of not more than 100k resistance must be provided
for input bias currents.
4. The common mode input voltage above ground cannot exceed +0.2V if the full input signal range of 999mV is required at pin 11. That is,
pin 11 may not operate higher than 1.2V positive with respect to ground or 0.2V negative with respect to ground. If the maximum input
signal is less than 999mV, the common mode input voltage may be raised accordingly.

CA3162
Timing Diagram
200mV

12
5 (LSD)
PIN NUMBER

reference constant current source of opposite polarity is

connected. The number of clock counts that elapse before the
charge is restored to its original value is a direct measure of
the signal induced current. The restoration is sensed by the
comparator, which in turn latches the counter. The count is
then multiplexed to the BCD outputs.

500mV

4 (MSD)

The timing for the CA3162E is supplied by a 786Hz ring

oscillator, and the input at pin 6 determines the sampling rate.
A 5V input provides a high speed sampling rate (96Hz), and
grounding or floating pin 6 provides a low speed (4Hz) sampling rate. When pin 6 is fixed at +1.2V (by placing a 12K
resistor between pin 6 and the +5V supply) a hold feature is
available. While the CA3162E is in the hold mode, sampling
continues at 4Hz but the display data are latched to the last
reading prior to the application of the 1.2V. Removal of the
1.2V restores continuous display changes. Note, however,
that the sampling rate remains at 4Hz.

500mV

3 (NSD)

500mV

2ms/DIV.

FIGURE 1. HIGH SPEED MODE

Detailed Description

Figure 1 shows the timing of sampling and digit select pulses

for the high speed mode. Note that the basic A/D conversion
process requires approximately 5ms in both modes.

The Functional Block Diagram of the CA3162E shows the V/I

converter and reference current generator, which is the heart
of the system. The V/I converter converts the input voltage
applied between pins 10 and 11 to a current that charges the
integrating capacitor on pin 12 for a predetermined time interval. At the end of the charging interval, the V/I converter is disconnected from the integrating capacitor, and a band gap
NOTE 2

NOTE 1

+5V

0.1
F

0.27F

NORMAL
8
LOW SPEED MODE:
V6 = GROUND OR
OPEN

The EEE or --- displays indicate that the range of the system
has been exceeded in the positive or negative direction,
respectively. Negative voltages to -99mV are displayed with the
minus sign in the MSD. The BCD code is 1010 for a negative
overrange (---) and 1011 for a positive overrange (EEE).

12

14

MSD

16

HOLD:
V6 = 1.2V

NSD

a
5

f
e

HIGH SPEED MODE:

V6 = 5V

b
g

c
d

c
d

13
CA3161E

BCD
OUTPUTS
11

a
f

b
g

DIGIT
DRIVERS

CA3162E

a
f

b
g

POWER
2N2907, 2N3906
OR EQUIV.

COMMON
ANODE LED
DISPLAYS
LSD

12
11

16

10

15

15

14

HIGH
INPUTS
LOW
10
13
GAIN
ADJ

R1
150

3
CA3162E
PINS
3, 4, 5

10
k

NOTES:
1. The capacitor used here must be a low dielectric absorption type
such as a polyester or polystyrene type.
2. This capacitor should be placed as close as possible to the power
and ground Pins of the CA3161E.

R2
150

CA3162E
PINS
1, 2, 15, 16

1k

75

DIGIT
DRIVER

BCD SEGMENT
DRIVERS

FIGURE 2. BASIC DIGITAL READOUT SYSTEM USING THE CA3162E AND THE CA3161E

R3
150

CA3162
capacitors and pull-up resistors connected to the MSD, NSD
and LSD outputs are there to shorten the digit drive signal
thereby providing proper timing for the CD4056B latches.

CA3162E Liquid Crystal Display (LCD) Application

Figure 3 shows the CA3162E in a typical LCD application.
LCDs may be used in favor of LED displays in applications
requiring lower power dissipation, such as battery-operated
equipment, or when visibility in high-ambient-light conditions
is desired.

Inverters G1 and G2 are used as an astable multivibrator to

provide the AC drive to the LCD backplane. Inverters G3, G4
and G5 are the digit-select inverters and require pull-up
resistors to interface the open-collector outputs of the
CA3162E to CMOS logic. The BCD outputs of the CA3162E
may be connected directly to the corresponding CD4056B
inputs (using pull-up resistors). In this arrangement, the
CD4056B decodes the negative sign (-) as an L and the
positive overload indicator (E) as an H.

Multiplexing of LCD digits is not practical, since LCDs must

be driven by an AC signal and the average voltage across
each segment is zero. Three CD4056B liquid-crystal
decoder/drivers are therefore used. Each CD4056B contains
an input latch so that the BCD data for each digit may be
latched into the decoder using the inverted digit-select outputs of the CA3162E as strobes.

The circuit as shown in Figure 3 using G7, G8 and G9 will

decode the negative sign (-) as a negative sign (-), and the
positive overload indicator (E) as H.

The capacitors on the outputs of inverters G3 and G4 filter

out the decode spikes on the MSD and NSD signals. The

+5V
0.047F

16

G3
0.047F

6
4

+5V

TO MSD
OF LCD

CD4056B

3
5 7

6x
10k
0.27F
ZERO
50k

8 14

12 4
3

9
CA3162E
HOLD

5
16
15
1

+5V
0.047
F

MSD
NSD

16

G4

LSD

0.047F

0.047
F

23
22

6
4
2

21

TO NSD
OF LCD

CD4056B

20

VIN+

11

VIN-

10 13

4x
7
100k

5 7

+5V

GAIN
10k

G5
16

1
+5V

6
4
G9

G7

TO LSD
OF LCD

CD4056B

G1 - G6: CD4049UB
HEX INVERTER
G7, G8, G9: CD4023B
TRIPLE 3 INPUT NAND GATE

5 7

8
TO LCD
BACKPLANE

G8

15k

100k

FIGURE 3. TYPICAL LCD APPLICATION

0.63F

CA3162
The additional logic shown within the dotted area of Figure 4
restores the negative sign (-), allowing the display of
negative numbers as low as -99mV. Negative overrange is
indicated by a negative sign (-) in the MSD position. The rest
of the display is blanked. During a positive overrange, only
segment b of the MSD is displayed. One inverter from the
CD4049B is used to operate the decimal points. By connecting the inverter input to either the MSD or NSD line either
DP1 or DP2 will be displayed.

CA3162E Common-Cathode, LED Display Application

Figure 4 shows the CA3162E connected to a CD4511B
decode/driver to operate a common-cathode LED display.
Unlike the CA3161E, the CD4511B remains blank for all
BCD codes greater than nine. After 999mV the display
blanks rather than displaying EEE, as with the CA3161E.
When displaying negative voltage, the first digit remains
blank, instead of (-), and during a negative or positive overrange the display blanks.

V+
DP1

100k

22k
1/

DP2

1/ CD4049UB
6

CD4049UB
CD4012B

1/
3

CD4049UB

1/ CD4049UB
6

V+
1 B

V+ 16
CD4511B

100k

100k

V+

2 C

f 15

3 LT

g 14

4 BL

a 13

1.8k

HP5082-7433
OR EQUIVALENT

1.2k
1.8k
1.2k

5 LE/STROBE b 12
1.8k

100k

100k

6 D

c 11

7 A

d 10

12

11 10

1.8k

c3

1.8k
8 GND

e 9

V+
DP1
1 B
100
k

100
k

100
k

CA3162E

2 A

c1

D 16

C 15

3 NSD

V+ 14

4 MSD

GAIN 13

5 LSD

INT 12
HIGH 11

7 GND

LOW 10

8 ZERO

DP2

c2
4

c
5

dP
6

10k
GAIN

6 BUFFERS
(1 CD4050B)

ZERO 9
V+

V+
0.27F

6 HOLD

INPUT

50k

FIGURE 4. TYPICAL COMMON-CATHODE LED APPLICATION