Fairchild Semiconductor TDC1044AR4C, TDC1044AN9C, TDC1044AB9C Datasheet

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TDC1044A

Monolithic Video A/D Converter

4-Bit, 25 Msps

Features

• 4-bit resolution

• 1/4 LSB non-linearity

• Sample-and-hold circuit not required

• 25 Msps conversion rate

• Selectable output format

• 16-lead DIP and 20-lead PLCC packages

Applications

• Digital communications

• Video special effects

• Radar data conversion

• Medical imaging

Block Diagram

NMINV

NLINV
CONV

V

IN

R

T

R

1

Description

The TDC1044A is a 25 Msps (Megasample per second) full­parallel analog-to-digital converter, capable of conv erting an
analog signal with full-power frequency components up to

12.5 MHz into 4-bit digital words. Use of a sample-and-hold
circuit is not necessary for operation of the TDC1044A. All
digital inputs and outputs are TTL compatible.

The TDC1044A consists of 15 latching comparators, encod­ing logic, and an output register. A single convert signal
controls the conversion operation. Output formats are
true/inverted binary or true/in verted of fset two’s complement
codes.

1

R

M

R

B

R

R

R

R

R

R

R/2

REFERENCE
RESISTOR
CHAIN

2

8

14

15

DIFFERENTIAL
COMPARATORS
(15)

15 TO 4

DECODER

LATCH

4

65-1044A-01

D1–D

4

Rev. 1.1.2

TDC1044A PRODUCT SPECIFICATION

Functional Description

General Information

The TDC1044A has three functional sections: a comparator
array, encoding logic, and an output re gister . The comparator
array compares the input signal with 15 reference voltages to
produce an N-of-15 thermometer code. All the comparators
referred to voltages more positive than the input signal will
be off, and those referred to voltages more negative than the
input signal will be on. Encoding logic converts the N-of-15
code into binary or two’s complement coding and can invert
either output code. This coding function is controlled by DC
signals on pins NMINV and NLINV. The output register
holds the output constant between updates.

Power

The TDC1044A operates from two power supply voltages,
+5.0V and -5.2V. The return for I
the +5.0V supply) is D

. The return for I

GND

drawn from the -5.2V supply) is A
ground pins must be connected.

Reference

The TDC1044A converts analog signals in the range
V

£

V

RB

IN

applied to R
and V

(the voltage applied to R

RT

ence resistor chain) should be between +0.1V and -1.1V.
V

should be more positive than V

RT

The voltage applied across the reference resistor chain
(V

– V

RT

RB

into digital form. V

£

V

RB

at the bottom of the reference resistor chain)

B

) must be between 0.4V and 1.3V.

(the current drawn from

CC

(the current

EE

. All power and

GND

(the voltage

RB

at the top of the refer-

B

within that range.

RB

Controls

Two function control pins, NMINV and NLINV, set the out­put format to be either straight binary or offset two’ s comple­ment, in either true or inverted sense, according to Table 1.
These pins are active LOW as signified by the prefix "N" in
the signal name. They may be tied to VCC for a logic "1" and
DGND for a logic "0."

NMINV controls the MSB, D
LSBs: D

, D

and D

2

3

.

4

; NLINV controls the three

1

Convert

The TDC1044A requires a CONVert (CONV) signal. A sam­ple is taken (the comparators are latched) within t

STO

after a
rising edge of CONV. The coded result is translated to the
output latches on the next rising edge. The outputs hold the
previous data a minimum time (t

) after the rising edge of

HO

the CONV signal. New data becomes valid after a maximum
delay time, t

.

D

Analog Input

The TDC1044A uses latching comparators which cause the
input impedance to vary slightly with the signal level. For
optimal performance, the source impedance of the driving
circuit must less than 25 Ohms. Within the range of V
+0.5V, the input signal will not damage the device. If the
input signal is at a voltage between V

RT

and V

RB

will be a binary code between 0 and 15 inclusive. A signal
outside this range will indicate either full-scale positive or
full-scale negative, depending on whether the signal is off­scale in the positive or negative direction.

to

EE

, the output

Nominal voltages are V

= 0.00V and V

RT

= -1.00V. These

RB

voltages may be varied dynamically up to 10MHz. Due to
slight variation in the reference currents with clock and input
signals, R

and R

T

should be low-impedance points. For cir-

B

cuits in which the reference is not varied, a bypass capacitor
to ground is recommended. If the reference inputs are varied
dynamically (as in an Automatic Gain Control circuit), a
low-impedance reference source is required.

A reference middle, R

, is also provided; this may be used

M

as an input to adjust the mid-scale point in order to improve
integral linearity . This point may also be used as a tap to sup­ply a mid-scale voltage to offset the analog input. If V

RM

is
used as an output, it must be connected to a high input
impedance device which has small input current. Noise at
this point may adversely affect the performance of this
device.

Outputs

TDC1044A outputs are TTL compatible, and capable of
driving four low-po wer Schottk y TTL (54/74 LS) unit loads.
The outputs hold the previous data a minimum time (t

HO

)
after the rising edge of the CONV signal. Data becomes
valid after a maximum delay time (t

) after the rising edge

D

of CONV. For optimum performance, 2.2 kOhm pull-up
resistors are recommended.

No Connects

Pin 3 of the TDC1044A is labeled No Connect (NC), and has
no connection to the chip. Connect this pin to A
noise performance.

GND

for best

2

PRODUCT SPECIFICATION TDC1044A

Table 1. Output Coding

1

Binary Offset Tw o’s Complement

Range

T rue Inverted T rue In verted

-1.00V FS NMINV = 1 0 0 1
NLINV = 1 0 1 0

0.000V 0000 1111 1000 0111

-0.067V 0001 1110 1001 0110

-0.133V 0010 1101 1010 0101

-0.200V 0011 1100 1011 0100

-0.267V 0100 1011 1100 0011

-0.333V 0101 1010 1101 0010

-0.400V 0110 1001 1110 0001

-0.467V 0111 1000 1111 0000

-0.533V 1000 0111 0000 1111

-0.600V 1001 0110 0001 1110

-0.667V 1010 0101 0010 1101

-0.733V 1011 0100 0011 1100

-0.800V 1100 0011 0100 1011

-0.867V 1101 0010 0101 1010

-0.933V 1110 0001 0110 1001

-1.000V 1111 0000 0111 1000

Note:

1. Input voltages are at code centers.

Pin Assignments

(LSB)

4

3D2D1

D

D

18

17

NC

CONV

A

GND

V

NC

19
20
1
2

IN

3

20 Lead PLCC 16 Lead DIP

16

4

5

6

T

R

NC

NC

(MSB)

D

15

14
13

12
11
10

7

8

B

R

V

GND

9

EE

V

CC

NMINV
R

M

NLINV
NC

65-1044A-02

A

GND

V

NC

R
R

V

EE

NLINV

R

1

IN

2
3

T

4

B

5
6
7
8

M

65-1044A-03

CONV

16

D

(LSB)

4

15

D

3

14

D

2

13

D

(MSB)

1

12

D

11

GND

V

10

CC

NMINV

9

3

TDC1044A PRODUCT SPECIFICATION

Pin Descriptions

Pin Number
Pin Name
Power

V

CC

V

EE

D

GND

A

GND

Reference

R

T

R

M

R

B

Control

NMINV 9 12 TTL Not MSB Invert
NLINV 7 10 TTL Not LSB Invert

Convert

CONV 16 20 TTL Convert

Analog Input

V

IN

Output

D

1

D

2

D

3

D

4

NC 3 3, 5, 6, 9, 19 A

10 13 +5.0V Positive Supply Voltage

6 8 -5.2V Negative Supply Voltage

11 14 0.0V Digital Ground

1 1 0.0V Analog Ground

4 4 0.0V Reference Resistor, Top
8 11 -0.5V Reference Resistor, Middle
5 7 -1.0V Reference Resistor, Bottom

2 2 0V to -1V Analog Input Signal

12 15 TTL MSB Output
13 16 TTL
14 17 TTL
15 18 TTL LSB Output

Value DescriptionDIP PLCC

GND

No Connect

4

PRODUCT SPECIFICATION TDC1044A

C

Absolute Maximum Ratings

(beyond which the device may be damaged)

Type Parameter Min Max Unit

Supply Voltages V

(measured to D

CC

V

(measured to A

EE

A

(measured to D

GND

Input Voltages CONV, NMINV, NLINV (measured to D

V

, V

, V

IN

RT

V

(measured to V

RT

(measured to A

RB

Output Applied voltage (measured to D

Applied current, externally forced
Short circuit duration (single output in high state to ground) 1 sec

Temperature Operating, ambient -55 +125

Operating, junction +150
Lead, soldering (10 seconds) +300
Storage -65 +150

Notes:

1. Absolute maximum ratings are limiting values applied individually while all other parameters are within specified operating
conditions. Functional operation under any of these conditions is NOT implied.

2. Applied voltage must be current limited to specified range.

3. Forcing voltage must be limited to specified range.

4. Current is specified as positive when flowing into the device.

1

) -0.5 7.0 V

GND

) +0.5 -7.0 V

GND

) -0.5 +0.5 V

GND

) -0.5 +5.5 V

GND

) +0.5 V

GND

) -2.2 +2.2 V

RB

2

GND

3,4

)

-0.5 +5.5 V

-1.0 +6.0 mA

EE

V

°

C

°

C

°

C

°

Operating Conditions

Parameter Min. Nom. Max. Units

V

CC

V

EE

V

AGND

t

PWL

t

PWH

V

IL

V

IH

I

OL

I

OH

V

RT

V

RB

VRT – V
V

IN

T

A

Positive Supply Voltage (measured to D
Negative Supply Voltage (measured to A
Analog Ground Voltage (measured to D
CONV Pulse Width, LOW 17 ns
CONV Pulse Width, HIGH 17 ns
Input Voltage, Logic LOW 0.8 V
Input Voltage, Logic HIGH 2.0 V
Output Current, Logic LOW 4.0 mA
Output Current, Logic HIGH -400 mA
Most Positive Reference -1.9 0.0 0.1 V
Most Negative Reference -2.1 -1.0 -0.1 V
Reference Differential 0.2 1.0 2.0 V

RB

Input Voltage V
Ambient Temperature, Still Air 0 70 °C

) 4.75 5.0 5.25 V

GND

) -4.9 -5.2 -5.5 V

GND

) -0.1 0.0 0.1 V

GND

RB

V

RT

V

5