NSC ADC12V170LFEB

ADC12V170
12-Bit, 170 MSPS, 1.1 GHz Bandwidth A/D Converter with
LVDS Outputs
General Description
Features
The ADC12V170 is a high-performance CMOS analog-todigital converter with LVDS outputs. It is capable of converting
analog input signals into 12-Bit digital words at rates up to 170
Mega Samples Per Second (MSPS). Data leaves the chip in
a DDR (Dual Data Rate) format; this allows both edges of the
output clock to be utilized while achieving a smaller package
size. This converter uses a differential, pipelined architecture
with digital error correction and an on-chip sample-and-hold
circuit to minimize power consumption and the external component count, while providing excellent dynamic performance. A unique sample-and-hold stage yields a full-power
bandwidth of 1.1 GHz. The ADC12V170 operates from dual
+3.3V and +1.8V power supplies and consumes 781 mW of
power at 170 MSPS.
The separate +1.8V supply for the digital output interface allows lower power operation with reduced noise. A powerdown feature reduces the power consumption to 15 mW while
still allowing fast wake-up time to full operation. In addition
there is a sleep feature which consumes 50 mW of power and
has a faster wake-up time.
The differential inputs provide a full scale differential input
swing equal to 2 times the reference voltage. A stable 1.0V
internal voltage reference is provided, or the ADC12V170 can
be operated with an external reference.
Clock mode (differential versus single-ended) and output data
format (offset binary versus 2's complement) are pin-selectable. A duty cycle stabilizer maintains performance over
a wide range of input clock duty cycles.
The ADC12V170 is pin-compatible with the ADC14V155. It is
available in a 48-lead LLP package and operates over the
industrial temperature range of −40°C to +85°C.
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1.1 GHz Full Power Bandwidth
Internal sample-and-hold circuit
Internal precision 1.0V reference
Single-ended or Differential clock modes
Clock Duty Cycle Stabilizer
Dual +3.3V and +1.8V supply operation
Power-down and Sleep modes
Offset binary or 2's complement output data format
LVDS outputs
Pin-compatible: ADC14V155
48-pin LLP package, (7x7x0.8mm, 0.5mm pin-pitch)
Key Specifications
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Resolution
Conversion Rate
SNR (fIN = 70 MHz)
SFDR (fIN = 70 MHz)
ENOB (fIN = 70 MHz)
Full Power Bandwidth
Power Consumption
12 Bits
170 MSPS
67.2 dBFS (typ)
85.8 dBFS (typ)
10.9 bits (typ)
1.1 GHz (typ)
781 mW (typ)
Applications
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High IF Sampling Receivers
Wireless Base Station Receivers
Power Amplifier Linearization
Multi-carrier, Multi-mode Receivers
Test and Measurement Equipment
Communications Instrumentation
Radar Systems
Block Diagram
30016802
© 2009 National Semiconductor Corporation
300168
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ADC12V170 12-Bit, 170 MSPS, 1.1 GHz Bandwidth A/D Converter with LVDS Outputs
April 27, 2009
ADC12V170
Connection Diagram
30016801
Ordering Information
Industrial (−40°C ≤ TA ≤ +85°C)
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Package
ADC12V170CISQ
48 Pin LLP
ADC12V170LFEB
Evaluation Board (fIN<150 MHz)
ADC12V170HFEB
Evaluation Board (fIN>150 MHz)
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ADC12V170
Pin Descriptions and Equivalent Circuits
Pin No.
Symbol
Equivalent Circuit
Description
ANALOG I/O
3
VIN−
4
VIN+
43
VRP
45
VRM
44
VRN
46
8
7
Differential analog input pins. The differential full-scale input signal
level is two times the reference voltage with each input pin signal
centered on a common mode voltage, VCM.
These pins should each be bypassed to AGND with a low ESL
(equivalent series inductance) 0.1 µF capacitor placed very close
to the pin to minimize stray inductance. A 0.1 µF capacitor should
be placed between VRP and VRN as close to the pins as possible,
and a 10 µF capacitor should be placed in parallel. The 0.1
µFcapacitor should be as small as possible (preferably 0201).
VRP and VRN should not be loaded. VRM may be loaded to 1mA for
use as a temperature stable 1.5V reference.
It is recommended to use VRM to provide the common mode
voltage, VCM, for the differential analog inputs, VIN+ and VIN−.
VREF
This pin can be used as either the +1.0V internal reference voltage
output (internal reference operation) or as the external reference
voltage input (external reference operation).
To use the internal reference, VREF should be decoupled to AGND
with a 0.1 µF, low equivalent series inductance (ESL) capacitor. In
this mode, VREF defaults as the output for the internal 1.0V
reference.
To use an external reference, overdrive this pin with a low noise
external reference voltage. The input impedance looking into this
pin is 9kΩ. Therefore, to overdrive this pin, the output impedance
of the external reference source should be << 9kΩ.
This pin should not be used to source or sink current.
The full scale differential input voltage range is 2 * VREF.
CLK_SEL/DF
This is a four-state pin controlling the input clock mode and output
data format.
CLK_SEL/DF = VA, CLK+ and CLK− are configured as a
differential clock input. The output data format is 2's complement.
CLK_SEL/DF = (2/3)*VA, CLK+ and CLK− are configured as a
differential clock input. The output data format is offset binary.
CLK_SEL/DF = (1/3)*VA, CLK+ is configured as a single-ended
clock input and CLK− should be tied to AGND. The output data
format is 2's complement.
CLK_SEL/DF = AGND, CLK+ is configured as a single-ended clock
input and CLK− should be tied to AGND. The output data format is
offset binary.
PD/Sleep
This is a three-state input controlling Power Down and Sleep
modes.
PD/Sleep = VA, Power Down is enabled. In the Power Down state
only the reference voltage circuitry remains active and power
dissipation is reduced.
PD/Sleep = VA/2, Sleep mode is enabled. Sleep mode is similar to
Power Down mode - it consumes more power but has a faster
recovery time.
PD/Sleep = AGND, Normal operation.
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ADC12V170
Pin No.
Symbol
11
CLK+
12
CLK−
Equivalent Circuit
Description
The clock input pins can be configured to accept either a singleended or a differential clock input signal.
When the single-ended clock mode is selected through CLK_SEL/
DF (pin 8), connect the clock input signal to the CLK+ pin and
connect the CLK− pin to AGND.
When the differential clock mode is selected through CLK_SEL/DF
(pin 8), connect the positive and negative clock inputs to the
CLK+ and CLK− pins, respectively.
The analog input is sampled on the falling edge of the clock input.
DIGITAL I/O
19
20
21
22
23
24
27
28
29
30
31
32
D1-/D0D1+/D0+
D3-/D2D3+/D2+
D5-/D4D5+/D4+
D7-/D6D7+/D6+
D9-/D8D9+/D8+
D11-/D10D11+/D10+
15
16
OVROVR+
Over-Range Indicator. This LVDS output is set HIGH when the
input amplitude goes outside the expected 12-Bit conversion range
(0 to 4095).
33
34
DRDY+
DRDY-
Data Ready Strobe. This LVDS output is used to clock the output
data. It has the same frequency as the sampling clock. One half of
the data word is output with each edge of this signal - thus
transferring a complete 12-bit word in each cycle of this clock. The
even bits should be captured with the rising edge of DRDY and the
odd bits should be captured with the falling edge of DRDY.
17, 18
DL-/DL+
LVDS low logic level.
LVDS digital data output pins that make up the 12-Bit conversion
result. The data is provided in a 2:1 multiplexed manner
synchronous to DRDY+/-.
The even bits should be captured with the rising edge of DRDY and
the odd bits should be captured with the falling edge of DRDY.
D0 is the LSB.
D11 is the MSB.
ANALOG POWER
1, 6, 9, 37, 40,
41, 48
VA
2, 5, 10, 38,
39, 42, 47,
Exposed Pad
AGND
Positive analog supply pins. These pins should be connected to a
quiet +3.3V source and be bypassed to AGND with 0.01 µF and
0.1 µF capacitors located close to the power pins.
The ground return for the analog supply.
Note: Exposed pad on bottom of package must be soldered to
ground plane to ensure rated performance.
DIGITAL POWER
13
VD
14
DGND
25, 36
26, 35
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Positive digital supply pin. This pin should be connected to a quiet
+3.3V source and be bypassed to DGND with a 0.01 µF and 0.1
µF capacitor located close to the power pin.
The ground return for the digital supply.
VDR
Positive driver supply pin for the output drivers. This pin should be
connected to a quiet voltage source of +1.8V and be bypassed to
DRGND with 0.01 µF and 0.1 µF capacitors located close to the
power pins.
DRGND
The ground return for the digital output driver supply. These pins
should be connected to the system digital ground, but not be
connected in close proximity to the ADC's DGND or AGND pins.
See Section 6.0 (Layout and Grounding) for more details.
4
Operating Ratings
(Notes 1, 2)
(Notes 1, 2)
Operating Temperature
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (VA, VD)
Output Driver Supply (VDR)
Clock Inputs (CLK+, CLK-)
Clock Duty Cycle
Analog Input Pins (VIN+, VIN-)
Analog Input Common Mode (VCM)
|AGND-DGND|
Supply Voltage (VA, VD)
Supply Voltage (VDR)
|VA–VD|
Voltage on Any Input Pin
(Not to exceed 4.2V)
Voltage on Any Output Pin
(Not to exceed 2.35V)
Input Current at Any Pin other
than Supply Pins (Note 3)
Package Input Current (Note 3)
Max Junction Temp (TJ)
−0.3V to 4.2V
−0.3V to 2.35V
≤ 100 mV
−0.3V to (VA +0.3V)
−40°C ≤ TA ≤ +85°C
+3.0V to +3.6V
+1.6V to +2.0V
−0.05V to (VA + 0.05V)
30/70 %
0V to 2.6V
1.4V to 1.6V
≤100mV
-0.3V to (VDR +0.2V)
±5 mA
±50 mA
+150°C
24°C/W
Thermal Resistance (θJA)
Package Dissipation at TA =
5.2W
25°C (Note 4)
ESD Rating
Human Body Model (Note 5)
2000 V
Machine Model (Note 5)
200 V
Charge Device Model
1000 V
Storage Temperature
−65°C to +150°C
Soldering process must comply with National
Semiconductor's Reflow Temperature Profile
specifications. Refer to www.national.com/packaging.
(Note 6)
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ADC12V170
Absolute Maximum Ratings
ADC12V170
Converter Electrical Characteristics
Unless otherwise specified, the following specifications apply: VIN = -1dBFS, AGND = DGND = DRGND = 0V, VA = VD = +3.3V,
VDR = +1.8V, Internal VREF = +1.0V, fCLK = 170 MHz, VCM = VRM, CL = 5 pF/pin, Single-Ended Clock Mode, Offset Binary Format.
Typical values are for TA = 25°C. Boldface limits apply for TMIN ≤ TA ≤ TMAX. All other limits apply for TA = 25°C (Notes 7, 8, 9)
Symbol
Parameter
Conditions
Typical
Limits
(Note 10)
Units
(Limits)
STATIC CONVERTER CHARACTERISTICS
Resolution with No Missing Codes
12
Bits (min)
LSB (max)
LSB (min)
INL
Integral Non Linearity (Note 11)
Full Scale Input
±0.5
1.9
-1.9
DNL
Differential Non Linearity
Full Scale Input
±0.3
1.0
-1.0
LSB (max)
LSB (min)
PGE
Positive Gain Error
+0.74
3.30
-2.10
%FS (max)
%FS (min)
NGE
Negative Gain Error
-0.33
2.10
-2.85
%FS (max)
%FS (min)
TC GE
Gain Error Tempco
VOFF
Offset Error (VIN+ = VIN−)
TC VOFF Offset Error Tempco
−40°C ≤ TA ≤ +85°C
+8.0
−0.11
−40°C ≤ TA ≤ +85°C
ppm/°C
0.75
-0.95
+0.5
%FS (max)
%FS (min)
ppm/°C
Under Range Output Code
0
0
Over Range Output Code
4095
4095
REFERENCE AND ANALOG INPUT CHARACTERISTICS
VCM
Common Mode Input Voltage
VRM
Reference Ladder Midpoint Output
Voltage
CIN
VIN Input Capacitance (each pin to GND) VIN = 1.5 Vdc
± 0.5 V (VCM)
(Note 12)
VREF
1.5
V
1.5
V
(CLK LOW)
6
pF
(CLK HIGH)
9
pF
Reference Voltage (Note 13)
1.00
V
Reference Input Resistance
9
kΩ
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Maximum output load = 1 mA
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Unless otherwise specified, the following specifications apply: VIN = -1dBFS, AGND = DGND = DRGND = 0V, VA = VD = +3.3V,
VDR = +1.8V, Internal VREF = +1.0V, fCLK = 170 MHz, VCM = VRM, CL = 5 pF/pin, Single-Ended Clock Mode, Offset Binary Format.
Typical values are for TA = 25°C. Boldface limits apply for TMIN ≤ TA ≤ TMAX. All other limits apply for TA = 25°C (Notes 7, 8, 9)
Symbol
Parameter
Conditions
Typical
(Note
10)
Limits
Units
(Limits)
DYNAMIC CONVERTER CHARACTERISTICS, AIN = -1dBFS
FPBW
SNR
SFDR
ENOB
THD
H2
H3
SINAD
Full Power Bandwidth
Signal-to-Noise Ratio
Spurious Free Dynamic Range
Effective Number of Bits
Total Harmonic Disortion
Second Harmonic Distortion
Third Harmonic Distortion
Signal-to-Noise and Distortion Ratio
-1 dBFS Input, −3 dB Corner
1.1
GHz
fIN = 10 MHz
67.9
dBFS
fIN = 70 MHz
67.2
fIN = 150 MHz
67.1
dBFS
fIN = 250 MHz
66.9
dBFS
fIN = 400 MHz
65.4
dBFS
fIN = 10 MHz
85.0
fIN = 70 MHz
85.8
fIN = 150 MHz
85.0
dBFS
fIN = 250 MHz
83.0
dBFS
fIN = 400 MHz
71.6
dBFS
fIN = 10 MHz
11.0
Bits
66.0
dBFS
dBFS
74.0
dBFS
fIN = 70 MHz
10.9
fIN = 150 MHz
10.8
Bits
fIN = 250 MHz
10.7
Bits
fIN = 400 MHz
10.3
Bits
fIN = 10 MHz
-82.7
fIN = 70 MHz
-82.3
fIN = 150 MHz
-80.7
dBFS
fIN = 250 MHz
-79.6
dBFS
fIN = 400 MHz
-68.8
dBFS
fIN = 10 MHz
-95.0
dBFS
fIN = 70 MHz
-88.4
fIN = 150 MHz
-87.4
dBFS
fIN = 250 MHz
-83.0
dBFS
fIN = 400 MHz
-71.6
dBFS
fIN = 10 MHz
-85.0
fIN = 70 MHz
-86.8
fIN = 150 MHz
-85.0
dBFS
fIN = 250 MHz
-88.1
dBFS
fIN = 400 MHz
-73.7
dBFS
fIN = 10 MHz
67.7
dBFS
fIN = 70 MHz
67.1
fIN = 150 MHz
67.0
dBFS
fIN = 250 MHz
66.7
dBFS
fIN = 400 MHz
63.8
dBFS
7
10.5
Bits
dBFS
-72.0
-77.0
dBFS
dBFS
dBFS
-74.0
65.1
dBFS
dBFS
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ADC12V170
Dynamic Converter Electrical Characteristics
ADC12V170
Logic and Power Supply Electrical Characteristics
Unless otherwise specified, the following specifications apply: VIN = -1 dBFS, AGND = DGND = DRGND = 0V, VA = VD = +3.3V,
VDR = +1.8V, Internal VREF = +1.0V, fCLK = 170 MHz, VCM = VRM, CL = 5 pF/pin, Single-Ended Clock Mode, Offset Binary Format.
Typical values are for TA = 25°C. Boldface limits apply for TMIN ≤ TA ≤ TMAX. All other limits apply for TA = 25°C (Notes 7, 8, 9)
Symbol
Parameter
Conditions
Typical
(Note 10)
Limits
Units
(Limits)
CLK INPUT CHARACTERISTICS
VIN(1)
Logical “1” Input Voltage
VD = 3.6V
2.0
V (min)
VIN(0)
Logical “0” Input Voltage
VD = 3.0V
0.8
V (max)
IIN(1)
Logical “1” Input Current
VIN = 3.3V
10
µA
IIN(0)
Logical “0” Input Current
VIN = 0V
−10
µA
CIN
Input Capacitance
5
pF
DIGITAL OUTPUT CHARACTERISTICS (D0+/- to D11+/-, DRDY+/-, OVR+/-, DL+/-)
VOD
LVDS differential output voltage
(Note 14)
350
VOS
The common-mode voltage of the LVDS
(Note 14)
output
1.22
RL
Intended Load Resistance
100
250
mVP-P (min)
450
mVP-P (max)
1.125
V (min)
1.375
V (max)
Ω
POWER SUPPLY CHARACTERISTICS
IA
Analog Supply Current
Full Operation
221
289
mA (max)
ID
Digital Supply Current
Full Operation
15
16
mA (max)
IDR
Digital Output Supply Current
Full Operation
31.5
mA
Power Consumption
Excludes IDR
781
mW
Power Down Power Consumption
15
mW
Sleep Power Consumption
50
mW
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Unless otherwise specified, the following specifications apply: VIN = -1dBFS, AGND = DGND = DRGND = 0V, VA = VD = +3.3V,
VDR = +1.8V, Internal VREF = +1.0V, fCLK = 170 MHz, VCM = VRM, CL = 5 pF/pin, Single-Ended Clock Mode, Offset Binary Format.
Typical values are for TA = 25°C. Timing measurements are taken at 50% of the signal amplitude. Boldface limits apply for
TMIN ≤ TA ≤ TMAX. All other limits apply for TA = 25°C (Notes 7, 8, 9)
Symbol
Limits
Units
(Limits)
Maximum Clock Frequency
170
MHz (max)
Minimum Clock Frequency
5
MHz (min)
Parameter
Conditions
Typical
(Note 10)
Clock High Time
2.7
Clock Low Time
2.7
Conversion Latency
tOD
ns
ns
7.5
Clock Cycles
Output Delay of CLK to DATA
Relative to falling edge of CLK
3.8
tDV
Data Output Valid Time
Time output data is valid before the
output edge of DRDY (Note 14)
ns
1.3
0.9
ns (min)
tDNV
Data Output Not Valid Time
Time till output data is not valid after
the output edge of DRDY (Note
14)
1.3
0.9
ns (min)
tAD
Aperture Delay
0.5
ns
Aperture Jitter
0.08
ps rms
Power Down Recovery Time
0.1 µF to GND on pins 43, 44; 10 µF
and 0.1 µF between pins 43, 44; 0.1
µF and 10 µF to GND on pins 45, 46
3.0
ms
Sleep Recovery Time
0.1 µF to GND on pins 43, 44; 10 µF
and 0.1 µF between pins 43, 44; 0.1
µF and 10 µF to GND on pins 45, 46
100
µs
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
guaranteed to be 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. Operation of the device beyond the maximum Operating Ratings is not recommended.
Note 2: All voltages are measured with respect to GND = AGND = DGND = DRGND = 0V, unless otherwise specified.
Note 3: When the input voltage at any pin exceeds the power supplies (that is, VIN < AGND, or VIN > VA), the current at that pin should be limited to ±5 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 ±5 mA to 10.
Note 4: The maximum allowable power dissipation is dictated by TJ,max, the junction-to-ambient thermal resistance, (θJA), and the ambient temperature, (TA), and
can be calculated using the formula PD,max = (TJ,max - TA )/θJA. The values for maximum power dissipation listed above will be reached only when the device 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). Such
conditions should always be avoided.
Note 5: Human Body Model is 100 pF discharged through a 1.5 kΩ resistor. Machine Model is 220 pF discharged through 0 Ω
Note 6: Reflow temperature profiles are different for lead-free and non-lead-free packages.
Note 7: The inputs are protected as shown below. Input voltage magnitudes above VA or below GND will not damage this device, provided current is limited per
(Note 3). However, errors in the A/D conversion can occur if the input goes above 2.6V or below GND as described in the Operating Ratings section.
30016811
Note 8: To guarantee accuracy, it is required that |VA–VD| ≤ 100 mV and separate bypass capacitors are used at each power supply pin.
Note 9: With the test condition for VREF = +1.0V (2VP-P differential input), the 12-Bit LSB is 488.3 µV.
Note 10: Typical figures are at TA = 25°C and represent most likely parametric norms at the time of product characterization. The typical specifications are not
guaranteed.
Note 11: Integral Non Linearity is defined as the deviation of the analog value, expressed in LSBs, from the straight line that passes through positive and negative
full-scale.
Note 12: The input capacitance is the sum of the package/pin capacitance and the sample and hold circuit capacitance.
Note 13: Optimum performance will be obtained by keeping the reference input in the 0.9V to 1.1V range. The LM4051CIM3-ADJ (SOT-23 package) is
recommended for external reference applications.
Note 14: This test parameter is guaranteed by design and characterization.
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ADC12V170
Timing and AC Characteristics
ADC12V170
MISSING CODES are those output codes that will never appear at the ADC outputs. The ADC12V170 is guaranteed not
to have any missing codes.
MSB (MOST SIGNIFICANT BIT) is the bit that has the largest
value or weight. Its value is one half of full scale.
NEGATIVE FULL SCALE ERROR is the difference between
the actual first code transition and its ideal value of ½ LSB
above negative full scale.
OFFSET ERROR is the difference between the two input
voltages [(VIN+) – (VIN-)] required to cause a transition from
code 2047 to 2048.
OUTPUT DELAY is the time delay after the falling edge of the
clock before the data update is presented at the output pins.
PIPELINE DELAY (LATENCY) See CONVERSION LATENCY.
POSITIVE FULL SCALE ERROR is the difference between
the actual last code transition and its ideal value of 1½ LSB
below positive full scale.
POWER SUPPLY REJECTION RATIO (PSRR) is a measure
of how well the ADC rejects a change in the power supply
voltage. PSRR is the ratio of the Full-Scale output of the ADC
with the supply at the minimum DC supply limit to the FullScale output of the ADC with the supply at the maximum DC
supply limit, expressed in dB.
SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in
dB, of the rms value of the input signal to the rms value of the
sum of all other spectral components below one-half the sampling frequency, not including harmonics or DC.
SIGNAL TO NOISE PLUS DISTORTION (S/N+D or
SINAD) Is the ratio, expressed in dB, of the rms value of the
input signal 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 input
signal 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 rms total of the first nine harmonic levels
at the output to the level of the fundamental at the output. THD
is calculated as
Specification Definitions
APERTURE DELAY is the time after the falling edge of the
clock to when the input signal is acquired or held for conversion.
APERTURE JITTER (APERTURE UNCERTAINTY) is the
variation in aperture delay from sample to sample. Aperture
jitter manifests itself as noise in the output.
CLOCK DUTY CYCLE is the ratio of the time during one cycle
that a repetitive digital waveform is high to the total time of
one period. The specification here refers to the ADC clock
input signal.
COMMON MODE VOLTAGE (VCM) is the common DC voltage applied to both input terminals of the ADC.
CONVERSION LATENCY is the number of clock cycles between initiation of conversion and when that data is presented
to the output driver stage. Data for any given sample is available at the output pins the Pipeline Delay plus the Output
Delay after the sample is taken. New data is available at every
clock cycle, but the data lags the conversion by the pipeline
delay.
DIFFERENTIAL NON-LINEARITY (DNL) is the measure of
the maximum deviation from the ideal step size of 1 LSB.
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.
FULL POWER BANDWIDTH is a measure of the frequency
at which the reconstructed output fundamental drops 3 dB
below its low frequency value for a full scale input.
GAIN ERROR is the deviation from the ideal slope of the
transfer function. It can be calculated as:
Gain Error = Positive Full Scale Error − Negative Full Scale
Error
It can also be expressed as Positive Gain Error and Negative
Gain Error, which are calculated as:
PGE = Positive Full Scale Error - Offset Error
NGE = Offset Error - Negative Full Scale Error
INTEGRAL NON LINEARITY (INL) is a measure of the deviation of each individual code from a line drawn from negative
full scale (½ LSB below the first code transition) through positive full scale (½ 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.
INTERMODULATION DISTORTION (IMD) is the creation of
additional spectral components 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 intermodulation
products to the total power in the original frequencies. IMD is
usually expressed in dBFS.
LSB (LEAST SIGNIFICANT BIT) is the bit that has the smallest value or weight of all bits. This value is VFS/2n, where
“VFS” is the full scale input voltage and “n” is the ADC resolution in bits.
LVDS DIFFERENTIAL OUTPUT VOLTAGE (VOD) is the absolute value of the differnece between VDX+ and VDX- outputs;
each measured with respect to Ground.
LVDS OUTPUT OFFSET VOLTAGE (VOS) is the midpoint
between the DX+ and DX- pins' output voltages; i.e., [VDx+ +
VDX-]/2.
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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.
SECOND HARMONIC DISTORTION (2ND HARM) is the difference expressed in dB, between the RMS power in the input
frequency at the output and the power in its 2nd harmonic
level at the output.
THIRD HARMONIC DISTORTION (3RD HARM) is the difference, expressed in dB, between the RMS power in the
input frequency at the output and the power in its 3rd harmonic
level at the output.
10
ADC12V170
Timing Diagram
30016820
Output Timing
Transfer Characteristic
30016810
FIGURE 1. Transfer Characteristic (Offset Binary Format)
11
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ADC12V170
Typical Performance Characteristics, DNL, INL
Unless otherwise specified, the following specifications apply: VIN = -1dBFS, AGND = DGND = DRGND = 0V, VA = VD = +3.3V,
VDR = +1.8V, Internal VREF = +1.0V, fCLK = 170 MHz, VCM = VRM, CL = 5 pF/pin, Single-Ended Clock Mode, Offset Binary Format.
Typical values are for TA = 25°C. (Notes 7, 8, 9)
DNL
INL
30016861
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30016862
12
Unless otherwise specified, the following specifications apply: VIN = -1dBFS, AGND = DGND = DRGND = 0V, VA = VD = +3.3V,
VDR = +1.8V, Internal VREF = +1.0V, fCLK = 170 MHz, fIN = 70 MHz, VCM = VRM, CL = 5 pF/pin, Single-Ended Clock Mode, Offset
Binary Format. Typical values are for TA = 25°C.
SNR, SINAD, SFDR vs. fIN
DISTORTION vs. fIN
30016895
30016883
SNR, SINAD, SFDR vs. VA
DISTORTION vs. VA
30016873
30016874
SNR, SINAD, SFDR vs. VDR
DISTORTION vs. VDR
30016875
30016876
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ADC12V170
Typical Performance Characteristics, Dynamic Performance
ADC12V170
Typical Performance Characteristics, Dynamic Performance
Unless otherwise specified, the following specifications apply: VIN = -1dBFS, AGND = DGND = DRGND = 0V, VA = VD = +3.3V,
VDR = +1.8V, Internal VREF = +1.0V, fCLK = 170 MHz, fIN = 70 MHz, VCM = VRM, CL = 5 pF/pin, Single-Ended Clock Mode, Offset
Binary Format. Typical values are for TA = 25°C.
SNR, SINAD, SFDR vs. VREF
DISTORTION vs. VREF
30016877
30016878
SNR, SINAD, SFDR vs. Temperature
DISTORTION vs. Temperature
30016881
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30016882
14
Unless otherwise specified, the following specifications apply: VIN = -1dBFS, AGND = DGND = DRGND = 0V, VA = VD = +3.3V,
VDR = +1.8V, Internal VREF = +1.0V, fCLK = 170 MHz, fIN = 70 MHz, VCM = VRM, CL = 5 pF/pin, Single-Ended Clock Mode, Offset
Binary Format. Typical values are for TA = 25°C.
Spectral Response @ 70 MHz Input
Spectral Response @ 150 MHz Input
30016892
30016893
Spectral Response @ 220 MHz Input
Spectral Response @ 250 MHz Input
30016894
30016896
Spectral Response @ 350 MHz Input
Spectral Response @ 400 MHz Input
30016897
30016898
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ADC12V170
Typical Performance Characteristics, Dynamic Performance
ADC12V170
Functional Description
2.0 ANALOG INPUTS
Operating on dual +3.3V and +1.8V supplies, the ADC12V170 digitizes a differential analog input signal to 12 bits,
using a differential pipelined architecture with error correction
circuitry and an on-chip sample-and-hold circuit to ensure
maximum performance.
The user has the choice of using an internal 1.0V stable reference, or using an external reference. The ADC12V170 will
accept an external reference between 0.9V and 1.1V (1.0V
recommended) which is buffered on-chip to ease the task of
driving that pin. The +1.8V output driver supply reduces power consumption and decreases the noise at the output of the
converter.
The quad state function pin CLK_SEL/DF (pin 8) allows the
user to choose between using a single-ended or a differential
clock input and between offset binary or 2's complement output data format. The digital outputs are LVDS compatible
signals that are clocked by a synchronous data ready output
signal (DRDY pins 33, 34) at the same rate as the clock input.
For the ADC12V170 the clock frequency can be between 5
MSPS and 170 MSPS (typical) with fully specified performance at 170 MSPS. The analog input is acquired at the
falling edge of the clock and the digital data for a given sample
is output on the falling edge of the DRDY signal and is delayed
by the pipeline for 7.5 clock cycles. The odd data bits should
be captured with the rising edge of DRDY and the even data
bits should be captured with the falling edge of DRDY.
Power-down is selectable using the PD/Sleep pin (pin 7). A
logic high on the PD/Sleep pin disables everything except the
voltage reference circuitry and reduces the converter power
consumption to 15 mW. When PD/Sleep is biased to VA/2 the
the chip enters sleep mode. In sleep mode everything except
the voltage reference circuitry and its accompanying on chip
buffer is disabled; power consumption is reduced to 50 mW.
The ADC12V170's wake-up time is quicker from sleep mode
than from power down mode. For normal operation, the PD/
Sleep pin should be connected to the analog ground (AGND).
A duty cycle stabilizer maintains performance over a wide
range of clock duty cycles.
2.1 Signal Inputs
2.1.1 Differential Analog Input Pins
The ADC12V170 has one pair of analog signal input pins,
VIN+ and VIN−, which form a differential input pair. The input
signal, VIN, is defined as
VIN = (VIN+) – (VIN−)
Figure 2 shows the expected input signal range. Note that the
common mode input voltage, VCM, should be 1.5V. Using
VRM (pin 45) for VCM will ensure the proper input common
mode level for the analog input signal. The peaks of the individual input signals should each never exceed 2.6V. Each
analog input pin of the differential pair should have a peak-topeak voltage equal to the reference voltage, VREF, be 180°
out of phase with each other and be centered around
VCM.The peak-to-peak voltage swing at each analog input pin
should not exceed the value of the reference voltage or the
output data will be clipped.
30016814
FIGURE 2. Expected Input Signal Range
For single frequency sine waves the full scale error in LSB
can be described as approximately
EFS = 4096 ( 1 - sin (90° + dev))
Where dev is the angular difference in degrees between the
two signals having a 180° relative phase relationship to each
other (see Figure 3). For single frequency inputs, angular errors result in a reduction of the effective full scale input. For
complex waveforms, however, angular errors will result in
distortion.
Applications Information
1.0 OPERATING CONDITIONS
We recommend that the following conditions be observed for
operation of the ADC12V170:
3.0V ≤ VA ≤ 3.6V
VD = VA
VDR = 1.8V
5 MHz ≤ fCLK ≤ 170 MHz
1.0V internal reference
0.9V ≤ VREF ≤ 1.1V (for an external reference)
VCM = 1.5V (from VRM)
Single Ended Clock Mode
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30016816
FIGURE 3. Angular Errors Between the Two Input Signals
Will Reduce the Output Level or Cause Distortion
It is recommended to drive the analog inputs with a source
impedance less than 100Ω. Matching the source impedance
for the differential inputs will improve even ordered harmonic
performance (particularly second harmonic).
Table 1 indicates the input to output relationship of the
ADC12V170.
16
VIN+
VIN−
Binary Output
2’s Complement Output
VCM − VREF/2
VCM + VREF/2
0000 0000 0000
1000 0000 0000
VCM − VREF/4
VCM + VREF/4
0100 0000 0000
1100 0000 0000
VCM
VCM
1000 0000 0000
0000 0000 0000
VCM + VREF/4
VCM − VREF/4
1100 0000 0000
0100 0000 0000
VCM + VREF/2
VCM − VREF/2
1111 1111 1111
0111 1111 1111
Negative Full-Scale
Mid-Scale
Positive Full-Scale
placed close to the ADC inputs because the analog input of
the ADC is the most sensitive part of the system, and this is
the last opportunity to filter that input. For Nyquist applications
the RC pole should be at the ADC sample rate. The ADC input
capacitance in the sample mode should be considered when
setting the RC pole. For wideband undersampling applications, the RC pole should be set at about 1.5 to 2 times the
maximum input frequency to maintain a linear delay response.
2.1.2 Driving the Analog Inputs
The VIN+ and the VIN− inputs of the ADC12V170 have an internal sample-and-hold circuit which consists of an analog
switch followed by a switched-capacitor amplifier. The analog
inputs are connected to the sampling capacitors through
NMOS switches, and each analog input has parasitic capacitances associated with it.
When the clock is high, the converter is in the sample phase.
The analog inputs are connected to the sampling capacitor
through the NMOS switches, which causes the capacitance
at the analog input pins to appear as the pin capacitance plus
the internal sample and hold circuit capacitance (approximately 9 pF). While the clock level remains high, the sampling
capacitor will track the changing analog input voltage. When
the clock transitions from high to low, the converter enters the
hold phase, during which the analog inputs are disconnected
from the sampling capacitor. The last voltage that appeared
at the analog input before the clock transition will be held on
the sampling capacitor and will be sent to the ADC core. The
capacitance seen at the analog input during the hold phase
appears as the sum of the pin capacitance and the parasitic
capacitances associated with the sample and hold circuit of
each analog input (approximately 6 pF). Once the clock signal
transitions from low to high, the analog inputs will be reconnected to the sampling capacitor to capture the next sample.
Usually, there will be a difference between the held voltage
on the sampling capacitor and the new voltage at the analog
input. This will cause a charging glitch that is proportional to
the voltage difference between the two samples to appear at
the analog input pin. The input circuitry must be fast enough
to allow the sampling capacitor to settle before the clock signal goes low again, as incomplete settling can degrade the
SFDR performance.
A single-ended to differential conversion circuit is shown in
Figure 4. A transformer is preferred for high frequency input
signals. Terminating the transformer on the secondary side
provides two advantages. First, it presents a real broadband
impedance to the ADC inputs and second, it provides a common path for the charging glitches from each side of the
differential sample-and-hold circuit.
One short-coming of using a transformer to achieve the single-ended to differential conversion is that most RF transformers have poor low frequency performance. A differential
amplifier can be used to drive the analog inputs for low frequency applications. The amplifier must be fast enough to
settle from the charging glitches on the analog input resulting
from the sample-and-hold operation before the clock goes
high and the sample is passed to the ADC core.
The SFDR performance of the converter depends on the external signal conditioning circuity used, as this affects how
quickly the sample-and-hold charging glitch will settle. An external resistor and capacitor network as shown in Figure 4
should be used to isolate the charging glitches at the ADC
input from the external driving circuit and to filter the wideband
noise at the converter input. These components should be
2.1.3 Input Common Mode Voltage
The input common mode voltage, VCM, should be in the range
of 1.4V to 1.6V and be a value such that the peak excursions
of the analog signal do not go more negative than ground or
more positive than 2.6V. It is recommended to use VRM (pin
45) as the input common mode voltage.
2.2 Reference Pins
The ADC12V170 is designed to operate with an internal 1.0V
reference, or an external 1.0V reference, but performs well
with external reference voltages in the range of 0.9V to 1.1V.
The internal 1.0 Volt reference is the default condition when
no external reference input is applied to the VREF pin. If a voltage in the range of 0.9V to 1.1V is applied to the VREF pin,
then that voltage is used for the reference. The VREF pin
should always be bypassed to ground with a 0.1 µF capacitor
close to the reference input pin. Lower reference voltages will
decrease the signal-to-noise ratio (SNR) of the ADC12V170.
Increasing the reference voltage (and the input signal swing)
beyond 1.1V may degrade THD for a full-scale input, especially at higher input frequencies.
It is important that all grounds associated with the reference
voltage and the analog input signal make connection to the
ground plane at a single, quiet point to minimize the effects of
noise currents in the ground path.
The Reference Bypass Pins (VRP, VRM, and VRN) are made
available for bypass purposes. All these pins should each be
bypassed to ground with a 0.1 µF capacitor. A 0.1 µF and a
10 µF capacitor should be placed between the VRP and VRN
pins, as shown in Figure 4. This configuration is necessary to
avoid reference oscillation, which could result in reduced SFDR and/or SNR. VRM may be loaded to 1mA for use as a
temperature stable 1.5V reference. The remaining pins
should not be loaded.
Smaller capacitor values than those specified will allow faster
recovery from the power down and sleep modes, but may result in degraded noise performance. Loading any of these
pins, other than VRM, may result in performance degradation.
The nominal voltages for the reference bypass pins are as
follows:
VRM = 1.5 V
VRP = VRM + VREF / 2
VRN = VRM − VREF / 2
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ADC12V170
TABLE 1. Input to Output Relationship
ADC12V170
figure the ADC for either differential or single-ended clock
mode (see Section 2.3.2). In differential clock mode, the two
clock signals should be exactly 180° out of phase from each
other and of the same amplitude. In the single-ended clock
mode, the clock signal should be routed to the CLK+ input and
the CLK− input should be tied to AGND in combination with
the correct setting from Table 3.
To achieve the optimum noise performance, the clock inputs
should be driven with a stable, low jitter clock signal in the
range indicated in the Electrical Table. The clock input signal
should also have a short transition region. This can be
achieved by passing a low-jitter sinusoidal clock source
through a high speed buffer gate. This configuration is shown
in Figure 4. The trace carrying the clock signal should be as
short as possible and should not cross any other signal line,
analog or digital, not even at 90°. Figure 4 shows the recommended clock input circuit.
The clock signal also drives an internal state machine. If the
clock is interrupted, or its frequency is too low, the charge on
the internal capacitors can dissipate to the point where the
accuracy of the output data will degrade. This is what limits
the minimum sample rate.
The clock line should be terminated at its source in the characteristic impedance of that line. Take care to maintain a
constant clock line impedance throughout the length of the
line. Refer to Application Note AN-905 for information on setting characteristic impedance.
It is highly desirable that the the source driving the ADC clock
pins only drive that pin. However, if that source is used to drive
other devices, then each driven pin should be AC terminated
with a series RC to ground, such that the resistor value is
equal to the characteristic impedance of the clock line and the
capacitor value is
2.3 Control Inputs
2.3.1 Power-Down & Sleep (PD/Sleep)
The power-down and sleep modes can be enabled through
this three-state input pin. Table 2 shows how to utilize these
options.
TABLE 2. Power Down/Sleep Selection Table
PD Input Voltage
Power State
VA
Power-down
VA/2
Sleep
AGND
On
The power-down and sleep modes allows the user to conserve power when the converter is not being used. In the
power-down state all bias currents of the analog circuitry, excluding the reference are shut down which reduces the power
consumption to 15 mW. In sleep mode some additional buffer
circuitry is left on to allow an even faster wake time; power
consumption in the sleep mode is 50 mW. In both of these
modes the output data pins are undefined and the data in the
pipeline is corrupted.
The Exit Cycle time for both the sleep and power-down mode
is determined by the value of the capacitors on the VRP, VRM
and VRN reference bypass pins (pins 43, 44 and 45). These
capacitors lose their charge when the ADC is not operating
and must be recharged by on-chip circuitry before conversions can be accurate. For power-down mode the Exit Cycle
time is about 3 ms with the recommended component values.
The Exit Cycle time is faster for sleep mode. Smaller capacitor
values allow slightly faster recovery from the power down and
sleep mode, but can result in reduced performance.
2.3.2 Clock Mode Select/Data Format (CLK_SEL/DF)
Single-ended versus differential clock mode and output data
format are selectable using this quad-state function pin. Table
3 shows how to select between the clock modes and the output data formats.
where tPD is the signal propagation rate down the clock line,
"L" is the line length and ZO is the characteristic impedance
of the clock line. This termination should be as close as possible to the ADC clock pin but beyond it as seen from the clock
source. Typical tPD is about 150 ps/inch (60 ps/cm) on FR-4
board material. The units of "L" and tPD should be the same
(inches or centimeters).
The duty cycle of the clock signal can affect the performance
of the A/D Converter. Because achieving a precise duty cycle
is difficult, the ADC12V170 has a Duty Cycle Stabilizer. It is
designed to maintain performance over a clock duty cycle
range of 30% to 70%.
TABLE 3. Clock Mode and Data Format Selection Table
CLK_SEL/DF
Input Voltage
Clock Mode
Output Data
Format
VA
Differential
2's Complement
(2/3) * VA
Differential
Offset Binary
(1/3) * VA
Single-Ended
2's Complement
AGND
Single-Ended
Offset Binary
3.0 CLOCK INPUTS
The CLK+ and CLK− signals control the timing of the sampling
process. The CLK_SEL/DF pin (pin 8) allows the user to con-
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ADC12V170
through VDR and DRGND. These large charging current
spikes can cause on-chip ground noise and couple into the
analog circuitry, degrading dynamic performance. Adequate
bypassing, limiting output capacitance and careful attention
to the ground plane will reduce this problem. Additionally, bus
capacitance beyond the specified 5 pF/pin will cause tOD to
increase, reducing the setup and hold time of the ADC output
data. The result could be an apparent reduction in dynamic
performance.
To minimize noise due to output switching, the load currents
at the digital outputs should be minimized. This can be
achieved by keeping the PCB traces less than 2 inches long;
longer traces are more susceptible to noise. Try to place the
100 ohm termination resistor as close to the receiving circuit
as possible. See Figure 4.
4.0 DIGITAL OUTPUTS
Digital outputs consist of the LVDS signals D0-D11, DL,
DRDY and OVR.
The ADC12V170 has 16 LVDS compatible data output pins:
12 data output bits corresponding to the converted input value, 2 output pins that are always set to LVDS low, a data ready
(DRDY) signal that should be used to capture the output data
and an over-range indicator (OVR) which is set high when the
sample amplitude exceeds the 12-Bit conversion range. Valid
data is present at these outputs while the PD/Sleep pin is low.
The odd data bits should be captured with the falling edge of
DRDY and the even data bits should be captured with the
rising edge of DRDY.
Be very careful when driving a high capacitance bus. The
more capacitance the output drivers must charge for each
conversion, the more instantaneous digital current flows
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20
FIGURE 4. Application Circuit using Transformer Drive Circuit (If 14-bit compatibility is not required do not connect pin 17 and 18)
30016813
ADC12V170
6.0 LAYOUT AND GROUNDING
Proper grounding and proper routing of all signals are essential to ensure accurate conversion. Maintaining separate analog and digital areas of the board, with the ADC12V170
between these areas, is required to achieve specified performance.
The ground return for the data outputs (DRGND) carries the
ground current for the output drivers. The output current can
exhibit high transients that could add noise to the conversion
process. To prevent this from happening, the DRGND pins
should NOT be connected to system ground in close proximity
to any of the ADC12V170's other ground pins.
Capacitive coupling between the typically noisy digital circuitry and the sensitive analog circuitry can lead to poor performance. The solution is to keep the analog circuitry separated
from the digital circuitry, and to keep the clock line as short as
possible.
Since digital switching transients are composed largely of
high frequency components, total ground plane copper
weight will have little effect upon the logic-generated noise.
This is because of the skin effect. Total surface area is more
important than is total ground plane area.
Generally, analog and digital lines should cross each other at
90° to avoid crosstalk. To maximize accuracy in high speed,
high resolution systems, however, avoid crossing analog and
digital lines altogether. It is important to keep clock lines as
short as possible and isolated from ALL other lines, including
other digital lines. Even the generally accepted 90° crossing
should be avoided with the clock line as even a little coupling
can cause problems at high frequencies. This is because other lines can introduce jitter into the clock line, which can lead
to degradation of SNR. Also, the high speed clock can introduce noise into the analog chain.
Best performance at high frequencies and at high resolution
is obtained with a straight signal path. That is, the signal path
through all components should form a straight line wherever
possible.
Be especially careful with the layout of inductors and transformers. Mutual inductance can change the characteristics of
7.0 DYNAMIC PERFORMANCE
To achieve the best dynamic performance, the clock source
driving the CLK input must have a sharp transition region and
be free of jitter. Isolate the ADC clock from any digital circuitry
with buffers, as with the clock tree shown in Figure 5 . The
gates used in the clock tree must be capable of operating at
frequencies much higher than those used if added jitter is to
be prevented. Best performance will be obtained with a single-ended drive input drive, compared with a differential clock.
As mentioned in Section 6.0, it is good practice to keep the
ADC clock line as short as possible and to keep it well away
from any other signals. Other signals can introduce jitter into
the clock signal, which can lead to reduced SNR performance, and the clock can introduce noise into other lines.
Even lines with 90° crossings have capacitive coupling, so try
to avoid even these 90° crossings of the clock line.
30016817
FIGURE 5. Isolating the ADC Clock from other Circuitry
with a Clock Tree
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ADC12V170
the circuit in which they are used. Inductors and transformers
should not be placed side by side, even with just a small part
of their bodies beside each other. For instance, place transformers for the analog input and the clock input at 90° to one
another to avoid magnetic coupling.
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 pins and ground or to the reference input
pin and ground should be connected to a very clean point in
the ground plane.
All analog circuitry (input amplifiers, filters, reference components, etc.) should be placed in the analog area of the board.
All digital circuitry and dynamic I/O lines should be placed in
the digital area of the board. The ADC12V170 should be between these two areas. Furthermore, all components in the
reference circuitry and the input signal chain that are connected to ground should be connected together with short
traces and enter the ground plane at a single, quiet point. All
ground connections should have a low inductance path to
ground.
5.0 POWER SUPPLY CONSIDERATIONS
The power supply pins should be bypassed with a 0.1 µF capacitor and with a 0.01 µF ceramic chip capacitor close to
each power pin. Leadless chip capacitors are preferred because they have low series inductance.
As is the case with all high-speed converters, the ADC12V170
is sensitive to power supply noise. Accordingly, the noise on
the analog supply pin should be kept below 100 mVP-P.
No pin should ever have a voltage on it that is in excess of the
supply voltages, not even on a transient basis. Be especially
careful of this during power turn on and turn off.
The VDR pin provides power for the output drivers and may be
operated from a supply in the range of 1.6V to 2.0V. This enables lower power operation, reduces the noise coupling
effects from the digital outputs to the analog circuitry and simplifies interfacing to lower voltage devices and systems. Note,
however, that tOD increases with reduced VDR.
ADC12V170
Physical Dimensions inches (millimeters) unless otherwise noted
48-Lead LLP Package
Ordering Number ADC12V170CISQ
NS Package Number SQA48A
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ADC12V170
Notes
23
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ADC12V170 12-Bit, 170 MSPS, 1.1 GHz Bandwidth A/D Converter with LVDS Outputs
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