The SPT7814 A/D converter is a 10-bit monolithic converter
capable of word rates of a minimum of 40 MSPS. On board
track/hold function assures excellent dynamic performance
without the need for external components. Drive requirement problems are minimized with an input capacitance of
only 5 pF.
Inputs and outputs are ECL to provide a higher level of noise
immunity in high speed system applications. An overrange
output signal is provided to indicate overflow conditions.
APPLICATIONS
• Medical Imaging
• Professional Video
• Radar Receivers
• Instrumentation
• Electronic Warfare
• Digital Communications
Output data format is straight binary. Power dissipation is
very low at only 1.3 watts with power supply voltages of +5.0
and -5.2 volts. The SPT7814 also provides a wide input
voltage swing of ±2.0 volts.
The SPT7814 is available in a 28-lead ceramic sidebrazed
DIP, PDIP, and die form. Commercial and industrial temperature ranges are currently offered. Contact the factory for
availability of military temperature ranges and /833 processed units.
BLOCK DIAGRAM
Analog
Input
Coarse
A/D
Analog
Prescaler
T/H Amplifier
Bank
Successive Interpolation
Stage i
Successive Interpolation
Stage i+1
Successive Interpolation
Stage N
4
Digital
Output
10
Decoding Network
Signal Processing Technologies, Inc.
4755 Forge Road, Colorado Springs, Colorado 80907, USA
Phone: (719) 528-2300 FAX: (719) 528-2370
Page 2
ABSOLUTE MAXIMUM RATINGS (Beyond which damage may occur)1 25 °C
Supply Voltages
VCC............................................................... -0.3 to +6 V
Output
Digital Outputs .......................................... +30 to -30 mA
VEE............................................................... +0.3 to -6 V
Temperature
Input Voltages
Analog Input............................................... VFB≤VIN≤V
Spurious Free Dynamic Range +25 °C,
Differential Phase+25 °C, f
TA=T
TA=T
TA=T
- T
min
max
- T
min
max
- T
min
max
fIN=1 MHzV6767dB
=3.58 & 4.35 MHzV0.20.2Degree
IN
IV4946dB
IV4946dB
IV4340dB
Differential Gain+25 °C, fIN=3.58 & 4.35 MHzV0.50.7%
Digital Inputs
Logic 1 VoltageVI-1.1-1.1V
Logic 0 VoltageVI-1.5-1.5 V
Maximum Input Current LowVI-500±200+750-500±200+750 µA
Maximum Input Current HighVI-500±300+750-500+300+750 µA
Pulse Width Low (CLK)IV1010ns
Pulse Width High (CLK)IV1030010300 ns
Digital Outputs
Logic 1 Voltage50 Ω to -2 VVI-1.1-0.8-1.1-0.8V
Logic 0 Voltage50 Ω to -2 VVI-1.8-1.5-1.8-1.5 V
Power Supply Requirements
VoltagesV
CurrentsI
-V
-I
CC
EE
CC
EE
IV+4.75-5.0+5.25+4.75+5.0+5.25 V
IV-4.95-5.2-5.45-4.95-5.2-5.45 V
VI140170140190 mA
VI115140115160 mA
Power DissipationOutputs OpenVI1.31.61.31.8 W
Power Supply Rejection Ratio (5 V ±0.25 V, -5.2 V ±2.0 V)V1.01.0LSB
SPT
SPT7814
33/11/97
Page 4
TEST LEVEL CODES
TEST LEVEL
TEST PROCEDURE
All electrical characteristics are subject to the
following conditions:
All parameters having min/max specifications
are guaranteed. The Test Level column indicates the specific device testing actually performed during production and Quality Assurance inspection. Any blank section in the data
column indicates that the specification is not
tested at the specified condition.
Figure 1A: Timing Diagram
N
t
pwH
CLK
t
pwL
II
III
IV
V
VI
I
100% production tested at the specified temperature.
100% production tested at TA=25 °C, and sample
tested at the specified temperatures.
QA sample tested only at the specified temperatures.
Parameter is guaranteed (but not tested) by design
and characterization data.
Parameter is a typical value for information purposes
only.
100% production tested at TA = 25 °C. Parameter is
guaranteed over specified temperature range.
N+1
N+2
CLK
Output
Data
t
d
Data Valid
N
Data Valid
N+1
Figure 1B: Single Event Clock
CLK
CLK
t
d
Output
Data
Data Valid
Table I - Timing Parameters
PARAMETERSDESCRIPTIONMINTYPMAXUNITS
t
d
t
pwH
CLK to Data Valid Prop Delay-5ns
CLK High Pulse Width10-300ns
t
pwL
SPT
CLK Low Pulse Width10--ns
SPT7814
43/11/97
Page 5
SPECIFICATION DEFINITIONS
APERTURE DELAY
Aperture delay represents the point in time, relative to the
rising edge of the CLOCK input, that the analog input is
sampled.
APERTURE JITTER
The variations in aperture delay for successive samples.
DIFFERENTIAL GAIN (DG)
A signal consisting of a sine wave superimposed on various
DC levels is applied to the input. Differential gain is the
maximum variation in the sampled sine wave amplitudes at
these DC levels.
DIFFERENTIAL PHASE (DP)
A signal consisting of a sine wave superimposed on various
DC levels that is applied to the input. Differential phase is the
variation in the sampled sine wave phases at these DC levels.
EFFECTIVE NUMBER OF BITS (ENOB)
SINAD = 6.02N + 1.76, where N is equal to the effective
number of bits.
DIFFERENTIAL NONLINEARITY (DNL)
Error in the width of each code from its theoretical value.
(Theoretical = VFS/2N)
INTEGRAL NONLINEARITY (INL)
Linearity error refers to the deviation of each individual code
(normalized) from a straight line drawn from -Fs through +Fs.
The deviation is measured from the edge of each particular
code to the true straight line.
OUTPUT DELAY
Time between the clock's triggering edge and output data
valid.
OVERVOLTAGE RECOVERY TIME
The time required for the ADC to recover to full accuracy after
an analog input signal 125% of full scale is reduced to 50%
of the full-scale value.
SIGNAL-TO-NOISE RATIO (SNR)
The ratio of the fundamental sinusoid power to the total noise
power. Harmonics are excluded.
SINAD - 1.76
N =
6.02
± FULL-SCALE ERROR (GAIN ERROR)
Difference between measured full scale response
[(+Fs) - (-Fs)] and the theoretical response (+4 V -2 LSBs)
where the +FS (full scale) input voltage is defined as the
output transition between 1-10 and 1-11 and the -FS input
voltage is defined as the output transition between 0-00 and
0-01.
INPUT BANDWIDTH
Small signal (50 mV) bandwidth (3 dB) of analog input stage.
SIGNAL-TO-NOISE AND DISTORTION (SINAD)
The ratio of the fundamental sinusoid power to the total noise
and distortion power.
TOTAL HARMONIC DISTORTION (THD)
The ratio of the total power of the first 64 harmonics to the
power of the measured sinusoidal signal.
SPURIOUS FREE DYNAMIC RANGE (SFDR)
The ratio of the fundamental sinusoidal amplitude to the
single largest harmonic or spurious signal.
SPT
SPT7814
53/11/97
Page 6
TYPICAL PERFORMANCE CHARACTERISTICS
80
70
60
50
40
Total Harmonic Distortion (dB)
30
20
0
10
80
70
60
THD vs Input Frequency
1
10
Input Frequency (MHz)
SINAD vs Input Frequency
fs =40 MSPS
fs = 40 MSPS
SNR vs Input Frequency
80
70
fs = 40 MSPS
60
50
40
Signal-to-Noise Ratio (dB)
30
2
10
20
0
10
Input Frequency (MHz)
1
10
2
10
SNR, THD, SINAD vs Sample Rate
80
70
SNR
60
50
40
30
Signal-to-Noise and Distortion (dB)
20
0
10
Spectral Response
0
-30
-60
Amplitude (dB)
-90
1
10
Input Frequency
(MHz)
fs = 40 MSPS
fin = 1 MHz
50
SINAD
THD
f
40
in = 1 MHz
SNR, THD, SINAD (dB)
30
2
10
20
0
10
Sample Rate (MSPS)
1
10
2
10
SNR, THD, SINAD vs Temperature
65
60
55
SINAD
50
SNR, THD, SINAD (dB)
45
fs = 40 MSPS
fin = 1 M H z
SNR
THD
-120
0 123456 78910
Input Frequency (MHz)
SPT
40
-250+25+50+75
Temperature (°C)
SPT7814
63/11/97
Page 7
TYPICAL INTERFACE CIRCUIT
The SPT7814 requires few external components to achieve
the stated operation and performance. Figure 2 shows the
typical interface requirements when using the SPT7814 in
normal circuit operation.
are not tied together internal to the device. The use of ground
planes is recommended to achieve the best performance of
the SPT7814. The AGND and the DGND ground planes
should be separated from each other and only connected
together at the device through an inductance. Doing this will
minimize the ground noise pickup.
The following section provides a description of the pin functions and outlines critical performance criteria to consider for
achieving the optimal device performance.
POWER SUPPLIES AND GROUNDING
The SPT7814 requires the use of two supply voltages, V
EE
and VCC. Both supplies should be treated as analog supply
sources. This means the VEE and VCC ground returns of the
device should both be connected to the analog ground
plane. All other -5.2 V requirements of the external digital
logic circuit should be connected to the digital ground plane.
Each power supply pin should be bypassed as closely as
possible to the device with .01 µF and 10 µF capacitors as
shown in figure 2.
The two grounds available on the SPT7814 are AGND and
DGND. DGND is used only for ECL outputs and is to be
referenced to the output pulldown voltage. These grounds
Figure 2 - Typical Interface Circuit
10 µF
+
+5 V
CLK-IN
CLK-IN
Analog
Input
Analog
Input
IC1
(REF-03)
2
VIN
GND
.01 µF
*R2 and R3
matched to 0.1%
VOUT
Tri m
4
+5 V
R4
10 kΩ
+
6
5
7
10 µF
-
(OP-07)
6
2
R2
30 kΩ
4
+2.5 V
*
-5.2 V
.01 µF
10 µF
R1
10 kΩ
3
+
IC2
1
8
R3
30 kΩ
-2.5 V
CLK
CLK
VIN1
VIN2
.01 µF
VFT
VST
.01 µF
VRM
.01 µF
*
VSB
.01 µF
VFB
.01 µF
+
VEE
2
R
2R
2R
2R
2R
R
VCC
VEE
VOLTAGE REFERENCE
The SPT7814 requires the use of two voltage references: V
and VFB. VFT is the force for the top of the voltage reference
ladder (+2.5 V typ), VFB (-2.5 V typ) is the force for the bottom
of the voltage reference ladder. Both voltages are applied
across an internal reference ladder resistance of 800 ohms.
In addition, there are 3 reference ladder taps (VST,VRM and
VSB). VST is the sense for the top of the reference ladder
(+2.0 V), VRM is the midpoint of the ladder (0.0 V typ) and V
is the sense for the bottom of the reference ladder (-2.0 V).
The voltages seen at VST and VSB are the true full scale input
voltages of the device when VFT and VFB are driven to the
recommended voltages (+2.5 V and -2.5 V typical respectively). These points should be used to monitor the actual full
scale input voltage of the device and should not be driven to
the expected ideal values as is commonly done with standard
flash converters. When not being used, a decoupling capacitor of .01 uF connected to AGND from each tap is recommended to minimize high frequency noise injection.
Coarse
A/D
ANALOG
PRESCALER
T/H AMPLIFIER
BANK
SUCCESSIVE
INTERPOLATION
STAGE # i
SUCCESSIVE
INTERPOLATION
STAGE # N
VCC
4
Decoding Network
DG
AG
AG
D10 (OVERRANGE)
D9 (MSB)
D8
D7
D6
D5
D4
D3
D2
D1
D0 (LSB)
DG
Digital Outputs
11 x 50 Ω
FT
SB
SPT
10 µF
+
.01 µF
-5.2 V+5 V
D1
NOTE: D1=D2=1N5817 or equivalent. (Used to prevent damage caused by power sequencing.)
D2
+
10 µF
.01 µF
AGND
( 5 V RTN &
-5.2 V RTN )
10 µH
L
DGND
( -2 V RTN )
10 µF
+
.01 µF
-2 V-5.2 V+5 V
73/11/97
SPT7814
Page 8
30354045505560657075
Duty
Cycle
Duty Cycle of Positive Clock Pulse (%)
Signal-to-Noise Ratio (dB)
43
45
47
49
51
53
55
57
59
tpwLtpwH
=
t
pwH
t
pwL
SNR vs Clock Duty Cycle
An example of a reference driver circuit recommended is
shown in figure 2. IC1 is REF-03, the +2.5 V reference with a
tolerance of 0.6% or ± 0.015 V. The potentiometer R1 is
10 kΩ and supports a minimum adjustable range of up to
150 mV. IC2 is recommended to be an OP-07 or equivalent
device. R2 and R3 must be matched to within 0.1% with good
TC tracking to maintain a 0.3 LSB matching between VFT and
VFB. If 0.1% matching is not met, then potentiometer R4 can
be used to adjust the VFB voltage to the desired level. R1 and
R4 should be adjusted such that VST and VSB are exactly
+2.0 V and -2.0 V respectively.
The analog input range will scale proportionally with respect
to the reference voltage if a different input range is required.
The maximum scaling factor for device operation is ± 20% of
the recommended reference voltages of VFT and VFB. However, because the device is laser trimmed to optimize performance with ± 2.5 V references, the accuracy of the device will
degrade if operated beyond a ± 2% range.
The following errors are defined:
+FS error = top of ladder offset voltage = ∆(+FS -VST+1 LSB)
-FS error=bottom of ladder offset voltage=∆(-FS -V
SB
-1 LSB)
where the +FS (full scale) input voltage is defined as the
output transition between 1-10 and 1-11 and the -FS input
voltage is defined as the output transition between 0-00 and
0-01.
ANALOG INPUT
V
IN1
and V
are the analog inputs. Both inputs are tied to
IN2
the same point internally. Either one may be used as an
analog input sense and the other for an input force. The inputs
can also be tied together and driven from the same source.
The full scale input range will be 80% of the reference voltage
or ±2 volts with VFB=-2.5 V and VFT=+2.5 V.
The drive requirements for the analog inputs are minimal
when compared to conventional Flash converters due the
SPT7814’s extremely low input capacitance of only 5 pF and
very high input resistance of 300 kΩ. For example, for an input
signal of ± 2 V p-p with an input frequency of 10 MHz, the peak
output current required for the driving circuit is only 628 µA.
The CLK pulse width (tpwH) must be kept between 10 ns and
300 ns to ensure proper operation of the internal track-andhold amplifier. (See timing diagram.) When operating the
SPT7814 at sampling rates above 3 MSPS, it is recommended that the clock input duty cycle be kept at 50% to
optimize performance. (See graph.) The analog input signal
is latched on the rising edge of the CLK.
DIGITAL OUTPUTS
The format of the output data (D0-D9) is straight binary.
These outputs are ECL with the output circuit shown in
figure 4. The outputs are latched on the rising edge of CLK
with a propagation delay of 4 ns. There is a one clock cycle
latency between CLK and the valid output data (see timing
diagram). These digital outputs can drive 50 ohms to ECL
levels when pulled down to -2 V. The total specified power
dissipation of the device does not include the power used by
these loads. The additional power used by these loads can
vary between 10 and 300 mW typically (including the overrange
load) depending on the output codes. If lower power levels
are desired, the output loads can be reduced, but careful
consideration to the capacitive loads in relation to the operating frequency must be considered.
CLOCK INPUT
The clock inputs (CLK,
) are designed to be driven differ-
CLK
entially with ECL levels. The clock may be driven single
ended since
left open, but a .01 µF bypass capacitor to AGND is recom-
is internally biased to -1.3 V.
CLK
mended. As with all high speed circuits, proper terminations
are required to avoid signal reflections and possible ringing
that can cause the device to trigger at an unwanted time.
SPT
CLK
Table II - Output Data Information
ANALOG INPUTOVERRANGEOUTPUT CODE
D1OD9-DO
>+2.0 V + 1/2 LSB111 1111 1111
may be
+2.0 V -1 LSBO11 1111 111Ø
0.0 VOØ Ø ØØØØ ØØØØ
-2.0 V +1 LSBOOO OOOO OOOØ
<-2.0 VOOO OOOO OOOO
(Ø indicates the flickering bit between logic 0 and 1).
SPT7814
83/11/97
Page 9
Figure 3 - Output Circuit
EVALUATION BOARD
AGND
OVERRANGE OUTPUT
The OVERRANGE OUTPUT (D10) is an indication that the
analog input signal has exceeded the positive full scale input
voltage by 1 LSB. When this condition occurs, D10 will switch
to logic 1. All other data outputs (D0 to D9) will remain at logic 1
as long as D10 remains at logic 1. This feature makes it
possible to include the SPT7814 into higher resolution
systems.
DGND
Data Out
The EB7814 evaluation board is available to aid designers in
demonstrating the full performance of the SPT7814. This
board includes a reference circuit, clock driver circuit, output
data latches and an on-board reconstruction of the digital
data. An application note describing the operation of this
board as well as information on the testing of the SPT7814 is
also available. Contact the factory for price and availability.
+5.0 V supply
Inputs (tied together at the die)
Force for Top of Reference Ladder
Sense for Top of Reference Ladder
Force for Bottom of Reference Ladder
Sense for Bottom of Reference Ladder
Middle of Reference Ladder
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
DGND
CLK
1
2
3
4
5
6
7
Sidebrazed
PDIP
8
9
10
11
12
13
14
ORDERING INFORMATION
PART NUMBERTEMPERATURE RANGEPACKAGE TYPE
SPT7814AIJ-25 to +85 °C28L Sidebrazed DIP
SPT7814BIJ-25 to +85 °C28L Sidebrazed DIP
SPT7814ACN0 to 70 °C28L Plastic DIP
SPT7814BCN0 to 70 °C28L Plastic DIP
SPT7814BCU+25 °CDie*
*Please see the die specification for guaranteed electrical performance.
Signal Processing Technologies, Inc. reserves the right to change products and specifications without notice. Permission is hereby expressly
granted to copy this literature for informational purposes only. Copying this material for any other use is strictly prohibited.
WARNING - LIFE SUPPORT APPLICATIONS POLICY - SPT products should not be used within Life Support Systems without the specific
written consent of SPT. A Life Support System is a product or system intended to support or sustain life which, if it fails, can be reasonably
expected to result in significant personal injury or death.
Signal Processing Technologies believes that ultrasonic cleaning of its products may damage the wire bonding, leading to device
failure. It is therefore not recommended, and exposure of a device to such a process will void the product warranty.
SPT
SPT7814
113/11/97
Loading...
+ hidden pages
You need points to download manuals.
1 point = 1 manual.
You can buy points or you can get point for every manual you upload.