NSC ADC10D040

ADC10D040
Dual 10-Bit, 40 MSPS, 267 mW A/D Converter
General Description
Features
The ADC10D040 is a dual low power, high performance
CMOS analog-to-digital converter that digitizes signals to 10
bits resolution at sampling rates up to 45 MSPS while consuming a typical 267 mW from a single 3.3V supply. No
missing codes is guaranteed over the full operating temperature range. The unique two stage architecture achieves 9.4
Effective Bits over the entire Nyquist band at 40 MHz sample
rate. An output formatting choice of offset binary or 2’s
complement coding and a choice of two gain settings eases
the interface to many systems. Also allowing great flexibility
of use is a selectable 10-bit multiplexed or 20-bit parallel
output mode. An offset correction feature minimizes the offset error.
To ease interfacing to most low voltage systems, the digital
output power pins of the ADC10D040 can be tied to a
separate supply voltage of 1.5V to 3.6V, making the outputs
compatible with other low voltage systems. When not converting, power consumption can be reduced by pulling the
PD (Power Down) pin high, placing the converter into a low
power state where it typically consumes less than 1 mW and
from which recovery is less than 1 ms. Bringing the STBY
(Standby) pin high places the converter into a standby mode
where power consumption is about 30 mW and from which
recovery is 800 ns.
The ADC10D040’s speed, resolution and single supply operation make it well suited for a variety of applications,
including high speed portable applications.
Operating over the industrial (−40˚ ≤ TA ≤ +85˚C) temperature range, the ADC10D040 is available in a 48-pin TQFP. An
evaluation board is available to ease the design effort.
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© 2005 National Semiconductor Corporation
DS200297
Internal sample-and-hold
Internal Reference Capability
Dual gain settings
Offset correction
Selectable offset binary or 2’s complement output
Multiplexed or parallel output bus
Single +3.0V to 3.6V operation
Power down and standby modes
3V TTL Logic input/output compatible
Key Specifications
Resolution
10 Bits
Conversion Rate
40 MSPS
ENOB
9.4 Bits (typ)
DNL
0.35 LSB (typ)
Conversion Latency Parallel Outputs
2.5 Clock Cycles
— Multiplexed Outputs, I Data Bus
2.5 Clock Cycles
— Multiplexed Outputs, Q Data Bus
3 Clock Cycles
n PSRR
90 dB
n Power Consumption — Normal Operation 267 mW (typ)
< 1 mW (typ)
— Power Down Mode
— Fast Recovery Standby Mode
30 mW (typ)
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Applications
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Digital Video
CCD Imaging
Portable Instrumentation
Communications
Medical Imaging
Ultrasound
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ADC10D040 Dual 10-Bit, 40 MSPS, 267 mW A/D Converter
February 2005
ADC10D040
Connection Diagram
20029701
TOP VIEW
Ordering Information
Device
Temperature Range
NS Package
ADC10D040CIVS
−40˚C to +85˚C
48-Pin TQFP
ADC10D040EVAL
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Evaluation Board
2
ADC10D040
Block Diagram
20029702
Pin Descriptions and Equivalent Circuits
Pin No.
Symbol
48
47
I+
I−
Analog inputs to “I” ADC. With VREF = 1.4V, conversion range
is 1.15V to 1.85V with GAIN pin low, or 0.8V to 2.2V with
GAIN pin high.
37
38
Q+
Q−
Analog inputs to “Q” ADC. With VREF = 1.4V, conversion
range is 1.15V to 1.85V with GAIN pin low, or 0.8V to 2.2V
with GAIN pin high.
1
Equivalent Circuit
Description
Analog Reference Voltage input. The voltage at this pin
should be in the range of 0.6V to 1.6V. With 1.4V at this pin
and the GAIN pin low, the full scale differential inputs are
1.4 VP-P. With 1.4V at this pin and the GAIN pin high, the full
scale differential inputs are 2.8 VP-P. This pin should be
bypassed with a minimum 1 µF capacitor.
VREF
3
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ADC10D040
Pin Descriptions and Equivalent Circuits
Pin No.
Symbol
Equivalent Circuit
(Continued)
Description
This is an analog output which can be used as a reference
source and/or to set the common mode voltage of the input. It
should be bypassed with a minimum of 1 µF low ESR
capacitor in parallel with a 0.1 µF capacitor. This pin has a
nominal output voltage of 1.5V and has a 1 mA output source
capability.
45
VCMO
43
VRP
Top of the reference ladder. Do not drive this pin. Bypass
this pin with a 10 µF low ESR capacitor and a 0.1 µF
capacitor.
44
VRN
Bottom of the reference ladder. Do not drive this pin.
Bypass this pin with a 10 µF low ESR capacitor and a 0.1 µF
capacitor.
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4
Pin No.
33
2
31
32
34
35
36
8 thru 27
28
40, 41
Symbol
Equivalent Circuit
(Continued)
Description
CLK
Digital clock input for both converters. The analog inputs are
sampled on the falling edge of this clock input.
OS
Output Bus Select. With this pin at a logic high, both the “I”
and the “Q” data are present on their respective 10-bit output
buses (Parallel mode of operation). When this pin is at a logic
low, the “I” and “Q” data are multiplexed onto the “I” output
bus and the “Q” output lines all remain at a logic low
(multiplexed mode).
OC
Offset Correct pin. A low-to-high transition on this pin initiates
an independent offset correction sequence for each converter,
which takes 34 clock cycles to complete. During this time 32
conversions are taken and averaged. The result is subtracted
from subsequent conversions. Each input pair should have 0V
differential value during this entire 34 clock period.
OF
Output Format pin. When this pin is LOW the output format is
Offset Binary. When this pin is HIGH the output format is 2’s
complement. This pin may be changed asynchronously, but
this will result in errors for one or two conversions.
STBY
Standby pin. The device operates normally with a logic low on
this and the PD (Power Down) pin. With this pin at a logic
high and the PD pin at a logic low, the device is in the
standby mode where it consumes just 30 mW of power. It
takes just 800 ns to come out of this mode after the STBY pin
is brought low.
PD
Power Down pin that, when high, puts the converter into the
Power Down mode where it consumes just 1 mW of power. It
takes less than 1 ms to recover from this mode after the PD
pin is brought low. If both the STBY and PD pins are high
simultaneously, the PD pin dominates.
GAIN
This pin sets the internal signal gain at the inputs to the
ADCs. With this pin low the full scale differential input
peak-to-peak signal is equal to VREF. With this pin high the
full scale differential input peak-to-peak signal is equal to 2 x
VREF.
I0–I9 and Q0–Q9
3V TTL/CMOS-compatible Digital Output pins that provide the
conversion results of the I and Q inputs. I0 and Q0 are the
LSBs, I9 and Q9 are the MSBs. Valid data is present just
after the rising edge of the CLK input in the Parallel mode. In
the multiplex mode, I-channel data is valid on I0 through I9
when the I/Q output is high and the Q-channel data is valid
on I0 through I9 when the I/Q output is low.
I/Q
Output data valid signal. In the multiplexed mode, this pin
transitions from low to high when the data bus transitions
from Q-data to I-data, and from high to low when the data bus
transitions from I-data to Q-data. In the Parallel mode, this pin
transitions from low to high as the output data changes.
VA
Positive analog supply pin. This pin should be connected to a
quiet voltage source of +3.0V to +3.6V. VA and VD should
have a common supply and be separately bypassed with
10 µF to 50 µF capacitors in parallel with 0.1 µF capacitors.
5
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ADC10D040
Pin Descriptions and Equivalent Circuits
ADC10D040
Pin Descriptions and Equivalent Circuits
Pin No.
Symbol
Equivalent Circuit
(Continued)
Description
VD
Digital supply pin. This pin should be connected to a quiet
voltage source of +3.0V to +3.6V. VA and VD should have a
common supply and be separately bypassed with 10 µF to 50
µF capacitors in parallel with 0.1 µF capacitors.
6, 30
VDR
Digital output driver supply pins. These pins should be
connected to a voltage source of +1.5V to VD and be
bypassed with 10 µF to 50 µF capacitors in parallel with 0.1
µF capacitors.
3, 39, 42,
46
AGND
The ground return for the analog supply. AGND and DGND
should be connected together close to the ADC10D040
package.
5
DGND
The ground return for the digital supply. AGND and DGND
should be connected together close to the ADC10D040
package.
7, 29
DR GND
4
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The ground return of the digital output drivers.
6
Operating Ratings (Notes 1, 2)
(Notes 1, 2)
Operating Temperature Range
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
VA, VD Supply Voltage
Positive Supply Voltages
Voltage on Any Pin
VCM Input Common Mode Range
See (Note 4)
ESD Susceptibility (Note 5)
Human Body Model
Storage Temperature
VREF/4 to (VA–VREF/4)
VREF/2 to (VA–VREF/2)
0.6V to 1.8V
Digital Input Pins Voltage
Range
250V
Soldering Temperature,
Infrared, 10 sec. (Note 6)
GAIN = Low
GAIN = High
VREF Voltage Range
2500V
Machine Model
± VREF/2
± VREF
GAIN = Low
GAIN = High
± 25 mA
± 50 mA
Package Dissipation at TA = 25˚C
+1.5V to VD
VIN Differential Voltage Range
−0.3V to (VA or VD +0.3V)
Package Input Current (Note 3)
+3.0V to +3.6V
VDR Supply Voltage
3.8V
Input Current at Any Pin (Note 3)
−40˚C ≤ TA ≤ +85˚C
−0.3V to (VA +0.3V)
235˚C
−65˚C to +150˚C
Converter Electrical Characteristics
The following specifications apply for VA = VD = +3.3 VDC, VDR = +2.5 VDC, VREF = 1.4 VDC, GAIN = OF = 0V, OS = 3.3V, VIN
(a.c. coupled) = FSR = 1.4 VP-P, CL = 15 pF, fCLK = 40 MHz, 50% Duty Cycle, RS = 50Ω, trc = tfc < 4 ns, NOT offset corrected. Boldface limits apply for TA = TMIN to TMAX: all other limits TA = 25˚C (Note 7).
Symbol
Parameter
Conditions
Typical
(Note 8)
Limits
(Note 9)
Units
(Limits)
STATIC CONVERTER CHARACTERISTICS
INL
Integral Non-Linearity
± 0.65
± 1.9
LSB (max)
DNL
Differential Non-Linearity
± 0.35
+1.2
−1.0
LSB (max)
LSB (min)
10
Bits
Without Offset Correction
−3.3
+7
−12
LSB (max)
LSB (min)
With Offset Correction
+0.4
+1.5
−0.5
LSB (max)
LSB (min)
−4
+5
−12
%FS (max)
%FS (min)
Resolution with No Missing Codes
VOFF
GE
Offset Error
Gain Error
DYNAMIC CONVERTER CHARACTERISTICS
fIN = 4.43 MHz, VIN = FSR −0.1 dB
ENOB
SINAD
SNR
THD
HS2
HS3
Effective Number of Bits
Signal-to-Noise Plus Distortion
Ratio
Signal-to-Noise Ratio
Total Harmonic Distortion
Second Harmonic
Third Harmonic
9.5
fIN = 10.4 MHz, VIN = FSR −0.1 dB, TA = 25˚C
9.5
fIN = 19.7 MHz, VIN = FSR −0.1 dB
9.4
fIN = 4.43 MHz, VIN = FSR −0.1 dB
59
fIN = 10.4 MHz, VIN = FSR −0.1 dB, TA = 25˚C
59
fIN = 19.7 MHz, VIN = FSR −0.1 dB
58
fIN = 4.43 MHz, VIN = FSR −0.1 dB
60
fIN = 10.4 MHz, VIN = FSR −0.1 dB, TA = 25˚C
60
Bits
9.1
Bits (min)
Bits
dB
56.3
dB (min)
dB
dB
57.3
dB (min)
fIN = 19.7 MHz, VIN = FSR −0.1 dB
59
dB
fIN = 4.43 MHz, VIN = FSR −0.1 dB
−70
dB
fIN = 10.4 MHz, VIN = FSR −0.1 dB, TA = 25˚C
−69
fIN = 19.7 MHz, VIN = FSR −0.1 dB
−67
dB
fIN = 4.43 MHz, VIN = FSR −0.1 dB
−86
dB
fIN = 10.4 MHz, VIN = FSR −0.1 dB
−83
dB
fIN = 19.7 MHz, VIN = FSR −0.1 dB
−81
dB
−61
dB (min)
fIN = 4.43 MHz, VIN = FSR −0.1 dB
−73
dB
fIN = 10.4 MHz, VIN = FSR −0.1 dB
−73
dB
fIN = 19.7 MHz, VIN = FSR −0.1 dB
−72
dB
7
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ADC10D040
Absolute Maximum Ratings
ADC10D040
Converter Electrical Characteristics
(Continued)
The following specifications apply for VA = VD = +3.3 VDC, VDR = +2.5 VDC, VREF = 1.4 VDC, GAIN = OF = 0V, OS = 3.3V, VIN
(a.c. coupled) = FSR = 1.4 VP-P, CL = 15 pF, fCLK = 40 MHz, 50% Duty Cycle, RS = 50Ω, trc = tfc < 4 ns, NOT offset corrected. Boldface limits apply for TA = TMIN to TMAX: all other limits TA = 25˚C (Note 7).
Symbol
SFDR
IMD
Parameter
Spurious Free Dynamic Range
Intermodulation Distortion
Conditions
Typical
(Note 8)
Limits
(Note 9)
Units
(Limits)
fIN = 4.43 MHz, VIN = FSR −0.1 dB
72
dB
fIN = 10.4 MHz, VIN = FSR −0.1 dB
72
dB
fIN = 19.7 MHz, VIN = FSR −0.1 dB
70
dB
fIN1 < 8.5 MHz, VIN = FSR −6.1 dB
fIN2 < 9.5 MHz, VIN = FSR −6.1 dB
71
dB
Overrange Output Code
(VIN+−VIN−) > 1.5V
1023
Underrange Output Code
(VIN+−VIN−) < −1.5V
0
FPBW Full Power Bandwidth
140
MHz
INTER-CHANNEL CHARACTERISTICS
Crosstalk
1 MHz input to tested channel, 10.3 MHz input
to other channel
−72
dB
Channel - Channel Aperture Delay
Match
fIN = 8 MHz
8.5
ps
0.1
%FS
Gain Pin = AGND
1.4
VP-P
Gain Pin = VA
Channel - Channel Gain Matching
REFERENCE AND ANALOG CHARACTERISTICS
VIN
Analog Differential Input Range
CIN
Analog Input Capacitance (each
input)
RIN
2.8
VP-P
Clock High
6
pF
Clock Low
3
pF
Analog Differential Input
Resistance
13.5
kΩ
VREF
Reference Voltage
1.4
IREF
Reference Input Current
<1
VCMO
Common Mode Voltage Output
TC
VCMO
Common Mode Voltage
Temperature Coefficient
1 mA load to ground (sourcing current)
1.5
0.6
V (min)
1.6
V (max)
1.35
V (min)
1.6
V (max)
µA
30
ppm/˚C
DIGITAL INPUT CHARACTERISTICS
VIH
Logical “1” Input Voltage
VD = +3.0V
2.0
V (min)
VIL
Logical “0” Input Voltage
VD = +3.6V
0.5
V (max)
IIH
Logical “1” Input Current
VIH = VD
IIL
Logical “0” Input Current
VIL = DGND
<1
> −1
µA
µA
DIGITAL OUTPUT CHARACTERISTICS
VOH
Logical “1” Output Voltage
VDR = +2.5V, IOUT = −0.5 mA
VOL
Logical “0” Output Voltage
VDR = +2.5V, IOUT = 1.6 mA
+ISC
Output Short Circuit Source
Current
VOUT = 0V
−ISC
Output Short Circuit Sink Current
VOUT = VDR
Parallel Mode
VDR
−0.2V
V (min)
0.4
V (max)
−4.7
mA
Multiplexed Mode
−9
mA
Parallel Mode
4.7
mA
9
mA
Multiplexed Mode
POWER SUPPLY CHARACTERISTICS
PD = LOW, STBY = LOW, d.c. input
IA
Analog Supply Current
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70
80
mA (max)
PD = LOW, STBY = HIGH
10
mA
PD = HIGH, STBY = LOW or HIGH
0.1
mA
8
(Continued)
The following specifications apply for VA = VD = +3.3 VDC, VDR = +2.5 VDC, VREF = 1.4 VDC, GAIN = OF = 0V, OS = 3.3V, VIN
(a.c. coupled) = FSR = 1.4 VP-P, CL = 15 pF, fCLK = 40 MHz, 50% Duty Cycle, RS = 50Ω, trc = tfc < 4 ns, NOT offset corrected. Boldface limits apply for TA = TMIN to TMAX: all other limits TA = 25˚C (Note 7).
Symbol
Parameter
Conditions
Typical
(Note 8)
Limits
(Note 9)
Units
(Limits)
9
10
mA (max)
PD = LOW, STBY = LOW, d.c. input
ID
Digital Supply Current
IDR
Digital Output Driver Supply
Current (Note 10)
PD
Power Consumption
PD = LOW, STBY = HIGH
0.1
mA
PD = HIGH, STBY = LOW or HIGH
0.1
mA
PD = STBY = LOW, dc input
1.9
2.5
mA (max)
PD = LOW, STBY = LOW, d.c. input
267
305
mW (max)
PD = LOW, STBY = LOW, 1 MHz Input
270
mW
PD = LOW, STBY = HIGH
30
mW
PD = HIGH, STBY = LOW or HIGH
0.6
mW
PSRR1 Power Supply Rejection Ratio
Change in Full Scale with 3.0V to 3.6V Supply
Change
90
dB
PSRR2 Power Supply Rejection Ratio
Rejection at output with 10.3 MHz, 250 mVP-P
Riding on VA and VD
52
dB
AC Electrical Characteristics
OS = Low (Multiplexed Mode)
The following specifications apply for VA = VD = +3.3 VDC, VDR = +2.5VDC, VREF = 1.4 VDC, GAIN = OF = 0V, OS = 0V, VIN
(a.c. coupled) = FSR = 1.4 VP-P, CL = 15 pF, fCLK = 40 MHz, 50% Duty Cycle, RS = 50Ω, trc = tfc < 4 ns, NOT offset corrected. Boldface limits apply for TA = TMIN to TMAX: all other limits TA = 25˚C (Note 7)
Symbol
Parameter
Conditions
Typical
(Note 8)
Limits
(Note 9)
Units
(Limits)
40
MHz (min)
fCLK1
Maximum Clock Frequency
45
fCLK2
Minimum Clock Frequency
20
Duty Cycle
50
MHz
45
55
% (min)
% (max)
I Data
2.5
Clock Cycles
Q Data
3.0
Clock Cycles
10
ns (min)
19
ns (max)
Pipeline Delay (Latency)
tr, tf
Output Rise and Fall Times
tOC
Offset Correction Pulse Width
tOD
Output Delay from CLK Edge to
Data Valid
tDIQ
I/Q Output Delay
13
tSKEW
I/Q to Data Skew
± 200
ps
tAD
Sampling (Aperture) Delay
2.2
ns
tAJ
Aperture Jitter
< 10
ps (rms)
tVALID
Data Valid Time
7.5
ns
50
ns
Overrange Recovery Time
5
13
Differential VIN step from 1.5V to
0V
ns
ns
tWUPD
PD Low to 1/2 LSB Accurate
Conversion (Wake-Up Time)
<1
ms
tWUSB
STBY Low to 1/2 LSB Accurate
Conversion (Wake-Up Time)
800
ns
9
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ADC10D040
Converter Electrical Characteristics
ADC10D040
AC Electrical Characteristics
OS = High (Parallel Mode)
The following specifications apply for VA = VD = +3.3 VDC, VDR = +2.5VDC, VREF = 1.4 VDC, GAIN = OF = 0V, OS = +3.3V,
VIN (a.c. coupled) = FSR = 1.0 VP-P, CL = 15 pF, fCLK = 40 MHz, 50% Duty Cycle, RS = 50Ω, trc = tfc < 4 ns, NOT offset corrected. Boldface limits apply for TA = TMIN to TMAX: all other limits TA = 25˚C (Note 7)
Symbol
Parameter
Conditions
Typical
(Note 8)
Limits
(Note 9)
Units
(Limits)
40
MHz (min)
45
55
% (min)
% (max)
2.5
Clock
Cycles
fCLK1
Maximum Clock Frequency
45
fCLK2
Minimum Clock Frequency
20
Duty Cycle
50
Pipeline Delay (Latency)
MHz
tr, tf
Output Rise and Fall Times
tOC
OC Pulse Width
tOD
Output Delay from CLK Edge to
Data Valid
16
tDIQ
I/Q Output Delay
13
tAD
Sampling (Aperture) Delay
2.2
ns
tAJ
Aperture Jitter
< 10
ps (rms)
tVALID
Data Valid Time
16
ns
50
ns
Overrange Recovery Time
9
Differential VIN step from 1.5V to
0V
ns
10
ns
22
ns (max)
ns
tWUPD
PD Low to 1/2 LSB Accurate
Conversion (Wake-Up Time)
<1
ms
tWUSB
STBY Low to 1/2 LSB Accurate
Conversion (Wake-Up Time)
800
ns
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed
specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test
conditions.
Note 2: All voltages are measured with respect to GND = AGND = DGND = 0V, unless otherwise specified.
Note 3: When the input voltage at any pin exceeds the power supplies (VIN < GND or VIN > VA or VD), the current at that pin should be limited to 25 mA. The 50 mA
maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 25 mA to two.
Note 4: The absolute maximum junction temperature (TJmax) for this device is 150˚C. The maximum allowable power dissipation is dictated by TJmax, the
junction-to-ambient thermal resistance (θJA), and the ambient temperature (TA), and can be calculated using the formula PDMAX = (TJmax - TA )/θJA. In the 48-pin
TQFP, θJA is 76˚C/W, so PDMAX = 1,645 mW at 25˚C and 855 mW at the maximum operating ambient temperature of 85˚C. Note that the power dissipation of this
device under normal operation will typically be about 307 mW (267 mW quiescent power + 40 mW due to 1 LVTTL load on each digital output). The values for
maximum power dissipation listed above will be reached only when the ADC10D040 is operated in a severe fault condition (e.g. when input or output pins are driven
beyond the power supply voltages, or the power supply polarity is reversed). Obviously, such conditions should always be avoided.
Note 5: Human body model is 100 pF capacitor discharged through a 1.5 kΩ resistor. Machine model is 220 pF discharged through 0Ω.
Note 6: See AN450, “Surface Mounting Methods and Their Effect on Product Reliability”, or the section entitled “Surface Mount” found in any post 1986 National
Semiconductor Linear Data Book, for other methods of soldering surface mount devices.
Note 7: The inputs are protected as shown below. Input voltage magnitude up to 300 mV beyond the supply rails will not damage this device. However, errors in
the A/D conversion can occur if the input goes beyond the limits given in these tables.
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10
OS = High (Parallel Mode)
ADC10D040
AC Electrical Characteristics
(Continued)
20029706
Note 8: Typical figures are at TJ = 25˚C, and represent most likely parametric norms.
Note 9: Test limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Performance is guaranteed only at VREF = 1.4V and a clock duty cycle
of 50%. The limits for VREF and clock duty cycle specify the range over which reasonable performance is expected. Tests are performed and limits guaranteed with
clock low and high levels of 0.3V and VD−0.3V, respectively.
Note 10: IDR is the current consumed by the switching of the output drivers and is primarily determined by the load capacitance on the output pins, the supply
voltage, VDR, and the rate at which the outputs are switching (which is signal dependent). IDR = VDR (CO x fO + C1 x f1 + ... + C9 x f9) where VDR is the output driver
power supply voltage, Cn is the total capacitance on the output pin, and fn is the average frequency at which that pin is toggling.
11
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ADC10D040
Timing Diagrams
20029708
ADC10D040 Timing Diagram for Multiplexed Mode
20029707
ADC10D040 Timing Diagram for Parallel Mode
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12
ADC10D040
Timing Diagrams
(Continued)
20029709
FIGURE 1. AC Test Circuit
13
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ADC10D040
MSB (MOST SIGNIFICANT BIT) is the bit that has the
largest value or weight. Its value is one half of full scale.
OFFSET ERROR is a measure of how far the mid-scale
transition point is from the ideal zero voltage input.
OUTPUT DELAY is the time delay after the rising edge of
the input clock before the data update is present at the
output pins.
Specification Definitions
APERTURE (SAMPLING) DELAY is that time required after
the fall of the clock input for the sampling switch to open. The
Sample/Hold circuit effectively stops capturing the input signal and goes into the “hold” mode tAD after the clock goes
low.
APERTURE JITTER is the variation in aperture delay from
sample to sample. Aperture jitter shows up as input noise.
CLOCK DUTY CYCLE is the ratio of the time that the clock
waveform is high to the total time of one clock period.
CROSSTALK is coupling of energy from one channel into
the other channel.
DIFFERENTIAL NON-LINEARITY (DNL) is the measure of
the maximum deviation from the ideal step size of 1 LSB.
Measured at 40 MSPS with a ramp input.
OVERRANGE RECOVERY TIME is the time required after
the differential input voltages goes from 1.5V to 0V for the
converter to recover and make a conversion with its rated
accuracy.
PIPELINE DELAY (LATENCY) is the number of clock cycles
between initiation of conversion and when that data is presented to the output driver stage. New data is available at
every clock cycle, but the data output lags the input by the
Pipeline Delay plus the Output Delay.
EFFECTIVE NUMBER OF BITS (ENOB, or EFFECTIVE
BITS) is another method of specifying Signal-to-Noise and
Distortion Ratio, or SINAD. ENOB is defined as (SINAD −
1.76)/6.02 and says that the converter is equivalent to a
perfect ADC of this (ENOB) number of bits.
POWER SUPPLY REJECTION RATIO (PSRR) can be one
of two specifications. PSRR1 (DC PSRR) is the ratio of the
change in full scale gain error that results from a power
supply voltage change from 3.0V to 3.6V. PSRR2 (AC
PSRR) is measured with a 10 MHz, 250 mVP-P signal riding
upon the power supply and is the ratio of the signal amplitude on the power supply pins to the amplitude of that
frequency at the output. PSRR is expressed in dB.
SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in
dB, of the rms value of the fundamental signal at the output
to the rms value of the sum of all other spectral components
below one-half the sampling frequency, not including harmonics or d.c.
SIGNAL TO NOISE PLUS DISTORTION (S/(N+D) or SINAD) is the ratio, expressed in dB, of the rms value of the
fundamental signal at the output to the rms value of all of the
other spectral components below half the clock frequency,
including harmonics but excluding d.c.
SPURIOUS FREE DYNAMIC RANGE (SFDR) is the difference, expressed in dB, between the rms values of the fundamental signal at the output and the peak spurious signal,
where a spurious signal is any signal present in the output
spectrum that is not present at the input.
TOTAL HARMONIC DISTORTION (THD) is the ratio, expressed in dB, of the total of the first nine harmonic levels at
the output to the level of the fundamental at the output. THD
is calculated as
FULL POWER BANDWIDTH (FPBW) is the frequency at
which the magnitude of the reconstructed output fundamental drops 3 dB below its 1 MHz value.
GAIN ERROR is the difference between the ideal and actual
differences between the input levels at which the first and
last code transitions occur. That is, how far this difference is
from Full Scale.
INTEGRAL NON LINEARITY (INL) is a measure of the
maximum deviation of each individual code from a line
drawn from negative full scale (1⁄2 LSB below the first code
transition) through positive full scale (1⁄2 LSB above the last
code transition). The deviation of any given code from this
straight line is measured from the center of that code value.
The end point test method is used. Measured at 40 MSPS
with a ramp input.
INTERMODULATION DISTORTION (IMD) is the creation of
spectral components that are not present in the input as a
result of two sinusoidal frequencies being applied to the ADC
input at the same time. It is defined as the ratio of the power
in the second and third order intermodulation products to the
total power in one of the original frequencies. IMD is usually
expressed in dB.
LSB (LEAST SIGNIFICANT BIT) is the bit that has the
smallest value of weight of all bits. This value is
m * VREF/2n
where “m” is the reference scale factor and “n” is the ADC
resolution, which is 10 in the case of the ADC10D040. The
value of “m” is determined by the logic level at the gain pin
and has a value of 1 when the gain pin is at a logic low and
a value of 2 when the gain pin is at a logic high.
MISSING CODES are those output codes that are skipped
and will never appear at the ADC outputs. These codes
cannot be reached with any input value.
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where f1 is the RMS power of the fundamental (output)
frequency and f2 through f10 are the RMS power of the first
9 harmonic frequencies in the output spectrum.
14
VA = VD = 3.3V, VDR = 2.5V, fCLK = 40 MHz, fIN = 10.4 MHz,
Typical INL
INL vs. VA
20029782
20029783
INL vs. VREF
INL vs. fCLK
20029784
20029785
INL vs. Clock Duty Cycle
INL vs. Temperature
20029787
20029786
15
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ADC10D040
Typical Performance Characteristics
unless otherwise specified
ADC10D040
Typical Performance Characteristics VA = VD = 3.3V, VDR = 2.5V, fCLK = 40 MHz, fIN = 10.4 MHz,
unless otherwise specified (Continued)
Typical DNL
DNL vs. VA
20029788
20029789
DNL vs. VREF
DNL vs. fCLK
20029790
20029791
SNR, SINAD & SFDR vs. VA
DISTORTION vs. VA
20029795
20029794
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DNL vs. Clock Duty Cycle
DNL vs. Temperature
20029792
20029793
SNR, SINAD & SFDR vs. VREF
DISTORTION vs. VREF
20029797
20029796
SNR, SINAD & SFDR vs. fCLK
DISTORTION vs. fCLK
20029799
20029798
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ADC10D040
Typical Performance Characteristics VA = VD = 3.3V, VDR = 2.5V, fCLK = 40 MHz, fIN = 10.4 MHz,
unless otherwise specified (Continued)
ADC10D040
Typical Performance Characteristics VA = VD = 3.3V, VDR = 2.5V, fCLK = 40 MHz, fIN = 10.4 MHz,
unless otherwise specified (Continued)
SNR, SINAD & SFDR vs. fIN
DISTORTION vs. fIN
200297A1
200297A0
SNR, SINAD & SFDR vs. Temperature
DISTORTION vs. Temperature
200297A4
200297A3
CROSSTALK vs. fIN
CROSSTALK vs. Temperature
200297A6
200297A5
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18
Total Power vs. TEMP
Spectral Response at fIN = 10.4 MHz
200297A7
200297A8
IMD Response fIN = 8.5 MHz, 9.5 MHz
200297A9
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ADC10D040
Typical Performance Characteristics VA = VD = 3.3V, VDR = 2.5V, fCLK = 40 MHz, fIN = 10.4 MHz,
unless otherwise specified (Continued)
ADC10D040
are not sensitive to the common-mode voltage and can be
anywhere within the supply rails (ground to VA) with little or
no performance degradation, as long as the signal swing at
the individual input pins is no more than 300 mV beyond the
supply rails.
Single-ended drive is not recommended as it can result in
degraded dynamic performance and faulty operation. If
single-ended input drive is absolutely required, it is recommended that a sample rate above 30 MSPS be used. If the
desired sample rate is lower than this, operate the
ADC10D040 at a multiple of the desired rate and decimate
the output (use every "nth" sample).
Functional Description
Using a subranging architecture, the ADC10D040 achieves
9.4 effective bits over the entire Nyquist band at 40 MSPS
while consuming just 267 mW. The use of an internal
sample-and-hold amplifier (SHA) not only enables this sustained dynamic performance, but also lowers the converter’s
input capacitance and reduces the number of external components required.
Analog signals at the “I” and “Q” inputs that are within the
voltage range set by VREF and the GAIN pin are digitized to
ten bits at up to 45 MSPS. VREF has a range of 0.6V to 1.6V,
providing a differential peak-to-peak input range of 0.6 VP-P
to 1.6 VP-P with the GAIN pin at a logic low, or a differential
input range of 1.2 VP-P to 3.2 VP-P with the GAIN pin at a
logic high. Differential input voltages less than −VREF/2 with
the GAIN pin low, or less than −VREF with the GAIN pin high
will cause the output word to indicate a negative full scale.
Differential input voltages greater than VREF/2 with the GAIN
pin low, or greater than VREF with the GAIN pin high, will
cause the output word to indicate a positive full scale.
For single-ended drive, operate the ADC10D040 with the
GAIN pin at a logic low, connect one pin of the input pair to
1.5V (VCM) through a resistor of 1k to 10 k Ohms, bypassing
this input pin to ground with a 1 µF capacitor. Drive the other
input pin of the input pair with 1.0 VP-P centered around 1.5V.
Because of the larger signal swing at one input for singleended operation, distortion performance will not be as good
as with a differential input signal. Alternatively, single-ended
to differential conversion with a transformer provides a quick,
easy solution for those applications not requiring response to
d.c. and low frequencies. See Figure 3. The 36Ω resistors
and 56 pF capacitor values are chosen to provide a cutoff
frequency near the clock frequency to compensate for the
effects of input sampling. A lower time constant should be
used for undersampling applications.
Both “I” and “Q” channels are sampled simultaneously on the
falling edge of the clock input, while the timing of the data
output depends upon the mode of operation.
In the parallel mode, the “I” and “Q” output busses contain
the conversion result for their respective inputs. The “I” and
“Q” channel data are present and valid at the data output
pins tOD after the rising edge of the input clock. In the
multiplexed mode, “I” channel data is available at the digital
outputs tOD after the rise of the clock edge, while the “Q”
channel data is available at the I0 through I9 digital outputs
tOD after the fall of the clock. However, a delayed I/Q output
signal should be used to latch the output for best, most
consistent results.
Data latency in the parallel mode is 2.5 clock cycles. In the
multiplexed mode data latency is 2.5 clock cycles for the “I”
channel and 3.0 clock cycles for the “Q” channel. The
ADC10D040 will convert as long as the clock signal is
present and the PD and STBY pins are low.
Throughout this discussion,VCM refers to the Common Mode
input voltage of the ADC10D040 while VCMO refers to its
Common Mode output voltage.
Applications Information
20029769
FIGURE 2. The ADC10D040 is designed for use with
differential signals of 1.4 VP-P with a common mode
voltage of 1.5V. The signal swing should not cause any
pin to experience a swing more than 300 mV beyond
the supply rails.
1.0 THE ANALOG SIGNAL INPUTS
Each of the analog inputs of the ADC10D040 consists of a
switch (transmission gate) followed by a switched capacitor
amplifier. The capacitance seen at each input pin changes
with the clock level, appearing as about 2 pF when the clock
is low, and about 5 pF when the clock is high. This switching
action causes analog input current spikes that work with the
input source impedance to produce voltage spikes.
The LMH6702 and the CLC428 dual op-amp have been
found to be a good amplifiers to drive the ADC10D040
because of their wide bandwidth and low distortion. They
also have good Differential Gain and Differential Phase performance.
Care should be taken to avoid driving the input beyond the
supply rails, even momentarily, as during power-up.
The ADC10D040 is designed for differential input signals for
best performance. With a 1.4V reference and the GAIN pin
at a logic low, differential input signals up to 1.4 VP-P are
digitized. See Figure 2. For differential signals, the input
common mode is expected to be about 1.5V, but the inputs
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2.0 REFERENCE INPUTS
The VRP and VRN pins should each be bypassed with a 5 µF
(or larger) tantalum or electrolytic capacitor and a 0.1 µF
ceramic capacitor. Use these pins only for bypassing. DO
NOT connect anything else to these pins.
Figure 4 shows a simple reference biasing scheme with
minimal components. While this circuit will suffice for many
applications, the value of the reference voltage will depend
upon the supply voltage.
The circuit of Figure 5 is an improvement over the circuit of
Figure 4 because the reference voltage is independent of
supply voltage. This reduces problems of reference voltage
20
The circuit of Figure 6 may be used if it is desired to obtain
a precise reference voltage not available with a fixed reference source. The 604Ω and 1.40k resistors can be replaced
with a potentiometer, if desired.
(Continued)
variability. The reference voltage at the VREF pin should be
bypassed to AGND with a 5 µF (or larger) tantalum or
electrolytic capacitor and a 0.1 µF ceramic capacitor.
20029770
FIGURE 3. Use of an input transformer for single-ended to differential conversion can simplify circuit design for
single-ended signals.
20029771
FIGURE 4. Simple Reference Biasing
21
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ADC10D040
Applications Information
ADC10D040
Applications Information
(Continued)
20029772
FIGURE 5. Improved Low Component Count Reference Biasing
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22
ADC10D040
Applications Information
(Continued)
20029773
FIGURE 6. Setting An Accurate Reference Voltage
23
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ADC10D040
Applications Information
(Continued)
20029774
FIGURE 7. The VCMO output pin may be used as an internal reference source if its output is not loaded excessively.
2.1 Reference Voltage
The reference voltage should be within the range specified in
the Operating Ratings table (0.6V to 1.6V). A reference
voltage that is too low could result in a noise performance
that is less than desired because the quantization level falls
below other noise sources. On the other hand, a reference
voltage that is too high means that an input signal that
produces a full scale output uses such a large input range
that the input stage is less linear, resulting in a degradation
of distortion performance. Also, for large reference voltages,
the internal ladder buffer runs out of head-room, leading to a
reduction of gain in that buffer and causing gain error degradation.
The Reference bypass pins VRP and VRN are output compensated and should each be bypassed with a parallel combination of a 5 µF (minimum) and 0.1 µF capacitors.
The VCMO output can be used as the ADC reference source
as long as care is taken to prevent excessive loading of this
pin. However, the VCMO output was not designed to be a
precision reference and has move variability than does a
precision reference. Refer to VCMO, Common Mode Voltage
Output, in the Electrical Characteristics table. Since the reference input of the ADC10D040 is buffered, there is virtually
no loading on the VCMO output by the VREF pin. While the
ADC10D040 will work with a 1.5V reference voltage, it is fully
specified for a 1.4V reference. To use the VCMO for a reference voltage at 1.4V, the 1.5V VCMO output needs to be
divided down. The divider resistor values need to be carefully chosen to prevent excessive VCMO loading. See Figure
7. While the average temperature coefficient of VCMO is 30
ppm/˚C, that temperature coefficient can be broken down to
a typical 70 ppm/˚C between −40˚C and +25˚C and a typical
−11 ppm/˚C between +25˚C and +85˚C.
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24
3.3 Offset Correct (OC) Pin
(Continued)
The Offset Correct (OC) pin is used to initiate an offset
correction sequence. This procedure should be done after
power up and need not be performed again unless power to
the ADC10D040 is interrupted. An independent offset correction sequence for each converter is initiated when there is
a low-to-high transition at the OC pin. This sequence takes
34 clock cycles to complete, during which time 32 conversions are taken and averaged. The result is subtracted from
subsequent conversions. Because the offset correction is
performed digitally at the output of the ADC, the output range
of the ADC is reduced by the offset amount.
2.2 VCMO Output
The VCMO output pin is intended to provide a common mode
bias for the differential input pins of the ADC10D040. It can
also be used as a voltage reference source. Care should be
taken, however, to avoid loading this pin with more than 1
mA. A load greater than this could result in degraded long
term and temperature stability of this voltage. The VCMO pin
is output compensated and should be bypassed with a
1 µF/0.1 µF combination, minimum. See Section 2.0 REFERENCE INPUTS for more information on using the VCMO
output as a reference source.
Each input pair should have a 0V differential voltage value
during this entire 34 clock period, but the “I” and “Q” input
common mode voltages do not have to be equal to each
other. Because of the uncertainty as to exactly when the
correction sequence starts, it is best to allow 35 clock periods for this sequence.
3.0 DIGITAL INPUT PINS
The seven digital input pins are used to control the function
of the ADC10D040.
3.1 The ADC Clock (CLK) Input
The clock (CLK) input is common to both A/D converters.
This pin is CMOS/LVTTL compatible with a threshold of
about VA/2. Although the ADC10D040 is tested and its performance is guaranteed with a 40 MHz clock, it typically will
function well with low-jitter clock frequencies from 20 MHz to
45 MHz. The analog inputs I = (I+) – (I−) and Q = (Q+) –
(Q−) are simultaneously sampled on the falling edge of this
input to ensure the best possible aperture delay match between the two channels.
3.4 Output Format (OF) Pin
The Output Format (OF) pin provides a choice of offset
binary or 2’s complement output formatting. With this pin at a
logic low, the output format is offset binary. With this pin at a
logic high, the output format is 2’s complement.
3.5 Standby (STBY) Pin
The Standby (STBY) pin may be used to put the
ADC10D040 into a low power mode where it consumes just
30 mW and can quickly be brought to full operation. The
device operates normally with a logic low on this and the PD
pins.
While in the Standby mode the data outputs contain the
results of the last conversion before going into this Mode.
3.1.1 Low Sample Rate Considerations
While the ADC10D040 will typically function well with sample
rates below 20 MSPS, it is important to note that it is possible
for some production lots not to perform well below 20 MSPS.
To ensure adequate performance over lot to lot and over
temperature extremes, we recommend not operating the
ADC10D040 at sample rates below 20 MSPS.
3.6 Power Down (PD) Pin
The Power Down (PD) pin puts the device into a low-power
“sleep” state where it consumes less than 1 mW when the
PD pin is at a logic high. Power consumption is reduced
more when the PD pin is high than when the STBY pin is
high, but recovery to full operation is much quicker from the
standby state than it is from the power down state. When the
STBY and PD pins are both high, the ADC10D040 is in the
power down mode.
While in the Power Down mode the data outputs contain the
results of the last conversion before going into this mode.
The output pins are always in the active state. That is, the
output pins do not have a high impedance state.
3.1.2 Clock Termination
The clock source should be series terminated to match the
clock source impedance with the characteristic impedance of
the clock line, ZO. It may also be necessary to a.c. terminate
the ADC clock pin with a series RC to ground. This series
network should be located near the ADC10D040 clock pin
but on the far side of that pin as seen from the clock source.
The resistor value should equal the characteristic impedance, ZO, of the clock line and the capacitor should have a
value such that C x ZO ≥ 4 x tPD, where tPD is the time of
propagation of the clock signal from its source to the ADC
clock pin. The typical propagation rate on a board of FR4
material is about 150 ps/inch. The rise and fall times of the
clock supplied to the ADC clock pin should be no more than
4 ns.
3.7 GAIN Pin
The GAIN pin sets the internal signal gain of the “I” and “Q”
inputs. With this pin at a logic low, the full scale differential
peak-to-peak input signal is equal to VREF. With the GAIN
pin at a logic high, the full scale differential peak-to-peak
input signal is equal to 2 times VREF.
3.2 Output Bus Select (OS) Pin
The Output Bus Select (OS) pin determines whether the
ADC10D040 is in the parallel or multiplexed mode of operation. A logic high at this pin puts the device into the parallel
mode of operation where “I” and “Q” data appear at their
respective output buses. A logic low at this pin puts the
device into the multiplexed mode of operation where the “I”
and “Q” data are multiplexed onto the “I” output bus and the
“Q” output lines all remain at a logic low.
4.0 INPUT/OUTPUT RELATIONSHIP ALTERNATIVES
The GAIN pin of the ADC10D040 offers input range selection, while the OF pin offers a choice of offset binary or 2’s
complement output formatting.
The relationship between the GAIN, OF, analog inputs and
the output code are as defined in Table 1. Keep in mind that
the input signals must not exceed the power supply rails.
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ADC10D040
Applications Information
ADC10D040
Applications Information
(Continued)
TABLE 1. ADC10D040 Input/Output Relationships
GAIN
OF
I+ / Q+
I− / Q−
0
0
VCM + 0.25*VREF
VCM − 0.25*VREF
Output Code
11 1111 1111
0
0
VCM
VCM
10 0000 0000
0
0
VCM − 0.25*VREF
VCM + 0.25*VREF
00 0000 0000
0
1
VCM + 0.25*VREF
VCM − 0.25*VREF
01 1111 1111
0
1
VCM
VCM
00 0000 0000
0
1
VCM − 0.25*VREF
VCM + 0.25*VREF
10 0000 0000
1
0
VCM + 0.5*VREF
VCM − 0.5*VREF
11 1111 1111
1
0
VCM
VCM
10 0000 0000
1
0
VCM − 0.5*VREF
VCM + 0.5*VREF
00 0000 0000
1
1
VCM + 0.5*VREF
VCM − 0.5*VREF
01 1111 1111
1
1
VCM
VCM
00 0000 0000
1
1
VCM − 0.5*VREF
VCM + 0.5*VREF
10 0000 0000
5.0 POWER SUPPLY CONSIDERATIONS
6.0 LAYOUT AND GROUNDING
A/D converters draw sufficient transient current to corrupt
their own power supplies if not adequately bypassed. A
10 µF to 50 µF tantalum or aluminum electrolytic capacitor
should be placed within half an inch (1.2 centimeters) of the
A/D power pins, with a 0.1 µF ceramic chip capacitor placed
as close as possible to each of the converter’s power supply
pins. Leadless chip capacitors are preferred because they
have low lead inductance.
While a single voltage source should be used for the analog
and digital supplies of the ADC10D040, these supply pins
should be well isolated from each other to prevent any digital
noise from being coupled to the analog power pins. A choke
is recommended between the VA and VD supply lines. VDR
should have a separate supply from VA and VD to avoid
noise coupling into the input. Be sure to bypass VDR.
The VDR pin is completely isolated from the other supply
pins. Because of this isolation, a separate supply can be
used for these pins. This VDR supply can be significantly
lower than the three volts used for the other supplies, easing
the interface to lower voltage digital systems. Using a lower
voltage for this supply can also reduce the power consumption and noise associated with the output drivers.
The converter digital supply should not be the supply that is
used for other digital circuitry on the board. It should be the
same supply used for the ADC10D040 analog supply.
As is the case with all high speed converters, the
ADC10D040 should be assumed to have little high frequency power supply rejection. A clean analog power source
should be used.
No pin should ever have a voltage on it that is more than
300 mV in excess of the supply voltages or below ground,
not even on a transient basis. This can be a problem upon
application of power to a circuit and upon turn off of the
power source. Be sure that the supplies to circuits driving the
CLK, or any other digital or analog inputs do not come up
any faster than does the voltage at the ADC10D040 power
pins.
Proper routing of all signals and proper ground techniques
are essential to ensure accurate conversion. Separate analog and digital ground planes may be used if adequate care
is taken with signal routing, but may result in EMI/RFI. A
single ground plane with proper component placement will
yield good results while minimizing EMI/RFI.
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Analog and digital ground current paths should not coincide
with each other as the common impedance will cause digital
noise to be added to analog signals. Accordingly, traces
carrying digital signals should be kept as far away from
traces carrying analog signals as is possible. Power should
be routed with traces rather than the use of a power plane.
The analog and digital power traces should be kept well
away from each other. All power to the ADC10D040, except
VDR, should be considered analog. The DR GND pin should
be considered a digital ground and not be connected to the
ground plane in close proximity with the other ground pins of
the ADC10D040.
Each bypass capacitor should be located as close to the
appropriate converter pin as possible and connected to the
pin and the appropriate ground plane with short traces. The
analog input should be isolated from noisy signal traces to
avoid coupling of spurious signals into the input. Any external component (e.g., a filter capacitor) connected between
the converter’s input and ground should be connected to a
very clean point in the ground return.
The clock line should be properly terminated, as discussed
in Section 3.1, and be as short as possible.
Figure 8 gives an example of a suitable layout and bypass
capacitor placement. All analog circuitry (input amplifiers,
filters, reference components, etc.) and interconnections
should be placed in an area reserved for analog circuitry. All
digital circuitry and I/O lines should be placed in an area
reserved for digital circuitry. Violating these rules can result
in digital noise getting into the analog circuitry, which will
degrade accuracy and dynamic performance (THD, SNR,
SINAD).
26
ADC10D040
Applications Information
(Continued)
20029775
FIGURE 8. An Acceptable Layout Pattern
7.0 DYNAMIC PERFORMANCE
The ADC10D040 is a.c. tested and its dynamic performance
is guaranteed. To meet the published specifications, the
clock source driving the CLK input must be free of jitter. For
best dynamic performance, isolating the ADC clock from any
digital circuitry should be done with adequate buffers, as with
a clock tree. See Figure 9.
74F and 74AC devices) to exhibit overshoot and undershoot
that goes a few hundred millivolts beyond the supply rails. A
resistor of 50Ω to 100Ω in series with the offending digital
input, close to the source, will usually eliminate the problem.
Care should be taken not to overdrive the inputs of the
ADC10D040 (or any device) with a device that is powered
from supplies outside the range of the ADC10D040 supply.
Such practice may lead to conversion inaccuracies and even
to device damage.
Attempting to drive a high capacitance digital data bus.
The more capacitance the output drivers have to charge for
each conversion, the more instantaneous digital current is
required from VDR and DR GND. These large charging current spikes can couple into the analog section, degrading
dynamic performance. Adequate bypassing and attention to
board layout will reduce this problem. Buffering the digital
data outputs (with a 74ACTQ841, for example) may be
necessary if the data bus to be driven is heavily loaded.
Dynamic performance can also be improved by adding series resistors of 47Ω to 56Ω at each digital output, close to
the ADC output pins.
Using a clock source with excessive jitter. This will cause
the sampling interval to vary, causing excessive output noise
and a reduction in SNR and SINAD performance. The use of
simple gates with RC timing as a clock source is generally
inadequate.
Using the same voltage source for VD and external digital logic. As mentioned in Section 5.0, VD should use the
same power source used by VA and other analog components, but should be decoupled from VA.
20029776
FIGURE 9. Isolating the ADC Clock from Digital
Circuitry
8.0 COMMON APPLICATION PITFALLS
Driving the inputs (analog or digital) beyond the power
supply rails. For proper operation, no input should go more
than 300 mV beyond the supply pins, Exceeding these limits
on even a transient basis can cause faulty or erratic operation. It is not uncommon for high speed digital circuits (e.g.,
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ADC10D040 Dual 10-Bit, 40 MSPS, 267 mW A/D Converter
Physical Dimensions
inches (millimeters) unless otherwise noted
NOTES UNLESS OTHERWISE SPECIFIED
1. STANDARD LEAD FINISH
7.62 MICROMETERS MINIMUM SOLDER PLATING (85/15)
THICKNESS ON ALLOY 42/COPPER.
2. DIMENSION DOES NOT INCLUDE MOLD PROTRUSION.
MAXIMUM ALLOWABLE MOLD PROTRUSION 0.15 mm PER SIDE.
3. REFERENCE JEDEC REGISTRATION MS-026, VARIATION ABC,
DATED FEBRUARY 1999.
48-Lead TQFP Package
Ordering Number ADC10D040CIVS
NS Package Number VBA48A
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS
WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body, or
(b) support or sustain life, and whose failure to perform when
properly used in accordance with instructions for use
provided in the labeling, can be reasonably expected to result
in a significant injury to the user.
2. A critical component is any component of a life support
device or system whose failure to perform can be reasonably
expected to cause the failure of the life support device or
system, or to affect its safety or effectiveness.
BANNED SUBSTANCE COMPLIANCE
National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products
Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain
no ‘‘Banned Substances’’ as defined in CSP-9-111S2.
National Semiconductor
Americas Customer
Support Center
Email: [email protected]
Tel: 1-800-272-9959
www.national.com
National Semiconductor
Europe Customer Support Center
Fax: +49 (0) 180-530 85 86
Email: [email protected]
Deutsch Tel: +49 (0) 69 9508 6208
English Tel: +44 (0) 870 24 0 2171
Français Tel: +33 (0) 1 41 91 8790
National Semiconductor
Asia Pacific Customer
Support Center
Email: [email protected]
National Semiconductor
Japan Customer Support Center
Fax: 81-3-5639-7507
Email: [email protected]
Tel: 81-3-5639-7560