www.fairchildsemi.com
TDC1046
Monolithic Video A/D Converter
6-Bit, 25 Msps
Features
•
•
•
•
•
•
•
•
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•
6-bit resolution
1/4 LSB linearity
Sample-and-hold circuit not required
TTL compatible
25 Msps conversion rate
Selectable output format
Available in an 18-pin CERDIP
Low cost
Low analog input capacitance
Available per Standard Military Drawing
Description
The TDC1046 is a 25 Msps (Megasample per second)
full-parallel (flash) analog-to-digital converter, capable of
converting an analog signal with full-power frequency
components up to 12.5 MHz into 6-bit digital words. Use of
a sample-and-hold circuit is not necessary for operation of
the TDC1046. All digital inputs and outputs are TTL
compatible.
The TDC1046 consists of 63 clocked latching comparators,
encoding logic, and an output buffer register. A single
convert signal controls the conversion operation. The unit
can be connected to give either true or inverted outputs in
binary or offset two’s complement coding.
Applications
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Low-cost video digitizing
Medical imaging
Data acquisition
TV special effects
Video simulators
Radar data conversion
Block Diagram
NMINV
NLINV
CONV
V
IN
R
T
R
1
1
R
2
R
63 TO 6
ENCODER
6
LATCH
D
1-6
R
62
R
63
R
2
R
B
DIFFERENTIAL
COMPARATORS
(63)
65-1046-01
Rev. 1.0.0
TDC1046
PRODUCT SPECIFICATION
Functional Description
General Information
The TDC1046 has three functional sections: a comparator
array, encoding logic, and output latches. The comparator
array compares the input signal with 63 reference voltages
to produce an N-of-63 code (sometimes referred to as a
“thermometer” code, as 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). The encoding logic converts the N-of-63 code
into binary or offset 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 latch
holds the output constant between updates.
Controls
Two function control pins, NMINV and NLINV are pro-
vided. These controls are for DC (i.e., steady states use. They
permit the output coding to be either straight binary or offset
two’s complement, in either true or inverted sense, according
to the Output Coding Table. These pins are active LOW as
signified by the prefix “N” in the signal name. They may be
tied to V
CC
for a logic “1” and D
GND
for a logic “0.”
Convert
The TDC1046 requires a CONVert (CONV) signal. A
sample is taken (the comparators are latched) within 5ns
after a rising edge on the CONV pin. This time is t
STO
. Sam-
pling Time Offset. The 63 to 6 encoding is performed on the
falling edge of the CONV signal. The coded result is trans-
ferred to the output latches on the next rising edge. The out-
puts hold the previous data a minimum time (t
HO
) after the
rising edge of the CONV signal.
Power
The TDC1046 operates from two supply voltages, +5.0V
and -5.2V. The return for I
CC
, the current drawn from the
+5.0V supply, is D
GND
. The return for I
EE
, the current
drawn from the -5.2V supply, is A
GND
. All power and
ground pins must be connected.
Analog Input
The TDC1046 uses strobed latching comparators which
cause the input impedance to vary with the signal level, as
comparator input transistors are cut-off or become active.
For optimal performance, the source impedance of the
driving circuit must be less than 50
W
. The input signal will
not damage the TDC1046 if it remains within the range of
V
EE
to +0.5V If the input signal is at a voltage between V
RT
and V
RB
, the output will be a binary number between
0 and 63 inclusive. A signal outside this range will indicate
either full-scale positive or full-scale negative, depending on
whether the signal is off-scale in the positive or negative
direction.
Reference
The TDC1046 converts analog signals in the range
V
RB
£
V
IN
£
V
RT
into digital form. V
RB
(the voltage
applied to R
B
at the bottom of the reference resistor chain)
and V
RT
(the voltage applied to R
T
at the top of the reference
resistor chain) should be between +0.1V and -1.1V. V
RT
should be more positive than V
RB
within that range. The
voltage applied across the reference resistor chain
(V
RT
–V
RB
) must be between 0.8V and 1.2V. The nominal
voltages are V
RT
= 0.00V and V
RG
= -1.00V. These voltages
may be varied dynamically up to 12.5MHz. Due to variation
in the reference currents with clock and input signals, R
T
and
R
B
should be low-impedance-to-ground points. For circuits
in which the reference is not varied, a bypass capacitor to
ground is recommended. If the reference inputs are exercised
dynamically (as in an Automatic Gain Control circuit), a
low-impedance reference source is required.
Outputs
The outputs of the TDC1046 are TTL compatible, and
capable of driving four low-power Schottky TTL (54/74 LS)
unit loads or the equivalent. The outputs hold the previous
data a minimum time (t
HO
) after the rising edge of the
CONV signal. Data is guaranteed to be valid after a
maximum delay time (t
D
) after the rising edge of CONV.
For optimum performance, 2.2 K
W
pull-up resistors are rec-
ommended.
Pin Assignments
Ceramic DIP
V
IN
R
T
D
GND
NMINV
(MSB) D
1
D
2
D
3
V
CC
V
EE
1
2
3
4
5
6
7
8
9
18
17
16
15
14
13
12
11
10
R
B
A
GND
D
GND
CONV
D
6
(LSB)
D
5
D
4
NLINV
V
CC
65-1046-02
2
TDC1046
PRODUCT SPECIFICATION
Absolute Maximum Ratings
1
(beyond which the device will be damaged)
Parameter
Supply Voltages
V
CC
(measured to D
GND
)
V
EE
(measured to A
GND
)
A
GND
(measured to D
GND
)
Input Voltages
CONV, NMINV, NLINV (measured to D
GND
)
V
IN
, V
RT
, V
RB
(measured to A
GND
)
V
RT
(measured to V
RB
)
Output
Applied voltage (measured to D
GND
)
2
Applied current, externally forced
3, 4
Short circuit duration (single output in high state to ground)
Temperature
Operating
Case
Junction
Lead, soldering (10 seconds)
Storage
-65
-55
+125
+175
+300
+150
°
C
°
C
°
C
°
C
-0.5
-1.0
5.5
6.0
1
V
mA
sec
0.5
+0.5
+1.2
+5.5
V
EE
-1.2
V
V
V
-0.5
-7.0
-0.5
+7.0
+0.5
+0.5
V
V
V
Min.
Max.
Unit
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.
Operating Conditions
Temperature Range
Standard
Parameters
V
CC
V
EE
V
AGND
t
PWL
t
PWH
V
IL
V
IH
l
OL
I
OH
V
RT
V
RB
V
RT-
V
RB
V
IN
Positive Supply Voltage (measured to D
GND
)
Negative Supply Voltage (measured to A
GND
)
Analog Ground Voltage (measured to D
GND
)
CONV Pulse Width (LOW)
CONV Pulse Width (HIGH)
Input Voltage, Logic LOW
Input Voltage, Logic HIGH
Output Current, Logic LOW
Output Current, Logic HIGH
Most Positive Reference Input
1
Most Negative Reference Inputs
1
Voltage Reference Differential
Input Voltage
-0.1
-0.9
0.8
V
RB
0.0
-1.0
2.0
4.0
-0.4
0.1
-1.1
1.2
-0.1
-0.9
0.8
0.0
-1.0
4.75
-4.9
-0.1
15
17
0.8
2.0
2.0
-0.4
0.1
-1.1
1.2
V
RT
5.0
-5.2
0.0
5.25
-5.5
0.1
4.5
-4.9
-0.1
15
17
0.8
Extended
5.0
-5.2
0.0
5.5
-5.5
0.1
V
V
V
ns
ns
V
V
mA
mA
V
V
V
V
Min. Nom. Max. Min. Nom. Max. Units
V
RT
V
RB
4
PRODUCT SPECIFICATION
TDC1046
Operating Conditions
(continued)
Temperature Range
Standard
Parameters
T
A
T
C
Ambient Temperature, Still Air
Case Temperature
0
70
-55
125
Extended
°C
°C
Min. Nom. Max. Min. Nom. Max. Units
Note:
1. V
RT
must be more positive than VRB, and voltage reference differential must be within specfied range.
DC Electrical Characteristics
Temperature Range
Standard
Parameter
I
CC
I
EE
Positive Supply Current
Negative Supply Current
Test Conditions
V
CC
= MAX, static
1
V
EE
= MAX, static
1
T
A
= 0°C to 70°C
T
A
= 70°C
T
C
= -55°C to 125°C
T
C
= 125°C
I
REF
R
REF
R
IN
C
IN
I
CB
I
IL
Reference Current
Total Reference Resistance
Input Equivalent Resistance
Input Capacitance
Input Constant Bias Current
Input Current, Logic LOW
V
EE
= MAX
V
CC
= MAX, V
I
= 0.5V
CONV
NMINV, NLINV
I
IH
I
I
V
OL
V
OH
l
OS
C
l
Input Current, Logic HIGH
Input Current, Max Input Voltage
Output Voltage, Logic LOW
Output Voltage, Logic HIGH
Short Circuit Output Current
Digital Input Capacitance
V
CC
= MAX, V
l
= 2.4V
V
CC
= MAX, V
l
= 5.5V
V
CC
= MIN, l
OL
= 2 mA
V
CC
= MIN, I
OH
= MAX
V
CC
= MAX, One pin to ground,
one second duration, output HIGH
TA = 25°C, F = 1MHz
2.4
-30
15
-0.4
-0.6
50
1.0
0.5
2.4
-30
15
-0.6
-0.8
50
1.0
0.5
mA
mA
pA
mA
V
V
mA
pF
V
RT
, V
RB
= NOM
V
RT
– V
RB
= MAX
V
RT
, V
RG
= NOM, V
IN
= V
RB
100
40
30
105
10
66
40
30
180
-95
-75
-150
- 75
15
mA
mA
mA
mA
mA
W
KW
pF
mA
20
Extended
25
mA
Min. Max. Min. Max. Units
Note:
1. Worst case, all digital inputs and outputs LOW.
5
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