MAX1181 [MAXIM]

Dual 10-Bit.80Msps.+3V.Low-Power ADC with Internal Reference and Parallel Outputs ; 双10 Bit.80Msps + 3V.Low功耗ADC,内置电压基准及并行输出\n
MAX1181
型号: MAX1181
厂家: MAXIM INTEGRATED PRODUCTS    MAXIM INTEGRATED PRODUCTS
描述:

Dual 10-Bit.80Msps.+3V.Low-Power ADC with Internal Reference and Parallel Outputs
双10 Bit.80Msps + 3V.Low功耗ADC,内置电压基准及并行输出\n

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19-2093; Rev 0; 7/01  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
General Description  
Features  
The MAX1181 is a +3V, dual 10-bit, analog-to-digital  
converter (ADC) featuring fully-differential wideband  
track-and-hold (T/H) inputs, driving two pipelined, nine-  
stage ADCs. The MAX1181 is optimized for low-power,  
high-dynamic performance applications in imaging,  
instrumentation, and digital communication applica-  
tions. The MAX1181 operates from a single +2.7V to  
+3.6V supply, consuming only 246mW, while delivering  
a typical signal-to-noise ratio (SNR) of 59dB at an input  
frequency of 20MHz and a sampling rate of 80Msps.  
The T/H driven input stages incorporate 400MHz (-3dB)  
input amplifiers. The converters may also be operated  
with single-ended inputs. In addition to low operating  
power, the MAX1181 features a 2.8mA sleep mode, as  
well as a 1µA power-down mode to conserve power  
during idle periods.  
Single +3V Operation  
Excellent Dynamic Performance:  
59dB SNR at f = 20MHz  
IN  
73dB SFDR at f = 20MHz  
IN  
Low Power:  
82mA (Normal Operation)  
2.8mA (Sleep Mode)  
1µA (Shutdown Mode)  
0.02dB Gain and 0.25° Phase Matching (typ)  
Wide 1Vpꢀp Differential Analog Input Voltage  
Range  
400MHz, ꢀ3dB Input Bandwidth  
OnꢀChip +2.048V Precision Bandgap Reference  
UserꢀSelectable Output Format—Two’s  
An internal +2.048V precision bandgap reference sets  
the full-scale range of the ADC. A flexible reference  
structure allows the use of the internal or external  
reference, if desired for applications requiring  
increased accuracy or a different input voltage range.  
Complement or Offset Binary  
48ꢀPin TQFP Package with Exposed Pad for  
Improved Thermal Dissipation  
Evaluation Kit Available  
The MAX1181 features parallel, CMOS-compatible  
three-state outputs. The digital output format is set to  
two’s complement or straight offset binary through a  
single control pin. The device provides for a separate  
output power supply of +1.7V to +3.6V for flexible inter-  
facing. The MAX1181 is available in a 7mm 7mm, 48-  
pin TQFP package, and is specified for the extended  
industrial (-40°C to +85°C) temperature range.  
Ordering Information  
PART  
TEMP. RANGE  
PIN-PACKAGE  
MAX1181ECM  
-40°C to +85°C  
48 TQFP-EP  
Pin Configuration  
Pin-compatible higher and lower speed versions of the  
MAX1181 are also available. Please refer to the  
MAX1180 datasheet for 105Msps, the MAX1182  
datasheet for 65Msps, the MAX1183 datasheet for  
40Msps, and the MAX1184 datasheet for 20Msps. In  
addition to these speed grades, this family includes a  
20Msps multiplexed output version (MAX1185), for  
which digital data is presented time-interleaved on a  
single, parallel 10-bit output port.  
COM  
1
2
36 D1A  
35 D0A  
34 OGND  
V
DD  
GND  
INA+  
INA-  
3
4
33 OV  
32 OV  
DD  
DD  
5
Applications  
V
6
31 OGND  
30 D0B  
29 D1B  
DD  
MAX1181  
GND  
INB-  
INB+  
GND  
7
High Resolution Imaging  
I/Q Channel Digitization  
Multichannel IF Undersampling  
Instrumentation  
8
D2B  
D3B  
D4B  
D5B  
9
28  
27  
26  
25  
10  
11  
12  
V
DD  
CLK  
Video Application  
Functional Diagram appears at end of data sheet.  
48 TQFP-EP  
________________________________________________________________ Maxim Integrated Products  
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at  
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
ABSOLUTE MAXIMUM RATINGS  
V
, OV  
to GND ...............................................-0.3V to +3.6V  
Continuous Power Dissipation (T = +70°C)  
DD  
DD  
A
OGND to GND.......................................................-0.3V to +0.3V  
48-Pin TQFP (derate 12.5mW/°C above +70°C).........1000mW  
Operating Temperature Range ...........................-40°C to +85°C  
Junction Temperature......................................................+150°C  
Storage Temperature Range.............................-60°C to +150°C  
Lead Temperature (soldering, 10s) .................................+300°C  
INA+, INA-, INB+, INB- to GND ...............................-0.3V to V  
REFIN, REFOUT, REFP, REFN, CLK,  
DD  
COM to GND ............................................-0.3V to (V + 0.3V)  
DD  
OE, PD, SLEEP, T/B, D9AD0A,  
D9BD0B to OGND ................................-0.3V to (OV + 0.3V)  
DD  
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional  
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to  
absolute maximum rating conditions for extended periods may affect device reliability.  
ELECTRICAL CHARACTERISTICS  
(V  
= +3V, OV  
= +2.5V; 0.1µF and 1.0µF capacitors from REFP, REFN, and COM to GND; REFOUT connected to REFIN through  
DD  
DD  
a 10kresistor, V = 2V  
(differential w.r.t. COM), C = 10pF at digital outputs (Note 5), f = 83.333MHz (50% duty cycle), T =  
CLK A  
IN  
p-p  
L
T
MIN  
to T  
, unless otherwise noted. Typical values are at T = +25°C.)  
MAX A  
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
DC ACCURACY  
Resolution  
10  
Bits  
LSB  
Integral Nonlinearity  
Differential Nonlinearity  
Offset Error  
INL  
f
f
= 7.47MHz  
0.6  
0.4  
2.2  
1.0  
1.7  
2
IN  
DNL  
= 7.47MHz, no missing codes guaranteed  
LSB  
IN  
<
1
% FS  
% FS  
Gain Error  
0
ANALOG INPUT  
Differential Input Voltage Range  
V
Differential or single-ended inputs  
Switched capacitor load  
1.0  
/2  
V
V
DIFF  
Common-Mode Input Voltage  
Range  
V
DD  
V
CM  
0.5  
Input Resistance  
R
25  
5
kΩ  
IN  
IN  
Input Capacitance  
C
pF  
CONVERSION RATE  
Maximum Clock Frequency  
f
80  
MHz  
CLK  
Clock  
Cycles  
Data Latency  
5
DYNAMIC CHARACTERISTICS (f  
= 83.333MHz, 4096-point FFT)  
CLK  
f
f
f
f
f
f
f
f
= 7.47MHz, T = +25°C  
56.5  
56  
59.5  
59  
59  
INA or B  
INA or B  
INA or B  
INA or B  
INA or B  
INA or B  
INA or B  
INA or B  
A
Signal-to-Noise Ratio  
SNR  
SINAD  
SFDR  
dB  
dB  
= 20MHz, T = +25°C  
A
= 39.9MHz (Note 1)  
= 7.47MHz, T = +25°C  
56  
55.3  
59  
A
Signal-to-Noise And Distortion  
(up to 5th harmonic)  
= 20MHz, T = +25°C  
58.5  
58.5  
75  
73  
71  
A
= 39.9MHz (Note 1)  
= 7.47MHz, T = +25°C  
65  
64  
A
Spurious-Free Dynamic  
Range  
= 20MHz, T = +25°C  
dBc  
A
= 39.9MHz, (Note 1)  
= 7.47MHz  
fINA or B  
f
f
f
-76  
INA or B  
INA or B  
INA or B  
Third-Harmonic Distortion  
HD3  
dBc  
= 20MHz  
-76  
-75  
= 39.9MHz (Note 1)  
2
_______________________________________________________________________________________  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
ELECTRICAL CHARACTERISTICS (continued)  
(V  
= +3V, OV  
= +2.5V; 0.1µF and 1.0µF capacitors from REFP, REFN, and COM to GND; REFOUT connected to REFIN through  
DD  
DD  
a 10kresistor, V = 2V  
(differential w.r.t. COM), C = 10pF at digital outputs (Note 5), f = 83.333MHz (50% duty cycle), T =  
CLK A  
IN  
p-p  
L
T
MIN  
to T  
, unless otherwise noted. Typical values are at T = +25°C.)  
MAX A  
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
f
f
= 38.1546MHz at -6.5dB FS  
= 41.9532MHz at -6.5dB FS  
INA or B  
INA or B  
Intermodulation Distortion  
(first five odd-order IMDs)  
IMD  
-73.5  
dBc  
(Note 2)  
f
= 7.47MHz, T = +25°C  
-73  
-70  
-70  
500  
400  
1
-64  
-63  
INA or B  
A
Total Harmonic Distortion  
(first five harmonics)  
THD  
f
f
= 20MHz, T = +25°C  
dBc  
INA or B  
INA or B  
A
= 39.9MHz (Note 1)  
Small-Signal Bandwidth  
Full-Power Bandwidth  
Aperture Delay  
Input at -20dB FS, differential inputs  
Input at -0.5dB FS, differential inputs  
MHz  
MHz  
ns  
FPBW  
t
AD  
Aperture Jitter  
t
2
ps  
RMS  
AJ  
Overdrive Recovery Time  
Differential Gain  
For 1.5 x full-scale input  
2
ns  
%
1
Differential Phase  
Output Noise  
0.25  
0.2  
degrees  
INA+ = INA- = INB+ = INB- = COM  
LSB  
RMS  
INTERNAL REFERENCE  
2.048  
3%  
Reference Output Voltage  
REFOUT  
TC  
V
Reference Temperature  
Coefficient  
60  
ppm/°C  
REF  
Load Regulation  
1.25  
mV/mA  
BUFFERED EXTERNAL REFERENCE (V  
=+2.048V)  
REFIN  
REFIN Input Voltage  
V
V
2.048  
2.012  
V
V
REFIN  
Positive Reference Output  
Voltage  
V
REFP  
Negative Reference Output  
Voltage  
0.988  
V
REFN  
Differential Reference Output  
Voltage Range  
V  
V  
= V  
- V  
REFN  
0.98  
1.024  
>50  
>5  
1.07  
V
REF  
REF  
REFP  
REFIN Resistance  
R
MΩ  
mA  
REFIN  
Maximum REFP, COM Source  
Current  
I
I
SOURCE  
Maximum REFP, COM Sink  
Current  
I
250  
µA  
SINK  
Maximum REFN Source Current  
Maximum REFN Sink Current  
250  
>5  
µA  
SOURCE  
I
mA  
SINK  
UNBUFFERED EXTERNAL REFERENCE (V  
= AGND, reference voltage applied to REFP, REFN and COM )  
REFIN  
R
R
Measured between REFP and COM and  
REFN and COM  
REFP,  
REFP, REFN Input Resistance  
4
kΩ  
REFN  
_______________________________________________________________________________________  
3
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
ELECTRICAL CHARACTERISTICS (continued)  
(V  
= +3V, OV  
= +2.5V; 0.1µF and 1.0µF capacitors from REFP, REFN, and COM to GND; REFOUT connected to REFIN through  
DD  
DD  
a 10kresistor, V = 2V  
(differential w.r.t. COM), C = 10pF at digital outputs (Note 5), f = 83.333MHz (50% duty cycle), T =  
CLK A  
IN  
p-p  
L
T
MIN  
to T  
, unless otherwise noted. Typical values are at T = +25°C.)  
MAX A  
PARAMETER  
SYMBOL  
CONDITIONS  
- V  
MIN  
TYP  
MAX UNITS  
Differential Reference Input  
Voltage  
1.024  
10%  
V  
V  
= V  
V
V
V
V
REF  
COM  
REFP  
REFN  
REF  
REFP  
REFN  
V
/2  
DD  
COM Input Voltage  
REFP Input Voltage  
REFN Input Voltage  
V
V
10%  
V
COM  
+ V  
/2  
REF  
V
COM  
V
- V  
/2  
REF  
DIGITAL INPUTS (CLK, PD, OE, SLEEP, T/B)  
0.8 x  
CLK  
V
DD  
Input High Threshold  
V
V
V
IH  
0.8 x  
OV  
PD, OE, SLEEP, T/B  
CLK  
DD  
0.2 x  
V
DD  
Input Low Threshold  
V
IL  
0.2 x  
OV  
PD, OE, SLEEP, T/B  
DD  
Input Hysteresis  
Input Leakage  
V
0.1  
V
HYST  
I
IH  
V
V
= OV or V (CLK)  
5
5
IH  
IL  
DD  
DD  
µA  
pF  
I
= 0  
IL  
Input Capacitance  
C
5
IN  
DIGITAL OUTPUTS (D9AD0A, D9BD0B)  
Output Voltage Low  
V
I
I
= 200µA  
0.2  
10  
V
V
OL  
SINK  
OV  
- 0.2  
DD  
Output Voltage High  
V
= 200µA  
SOURCE  
OH  
Three-State Leakage Current  
Three-State Output Capacitance  
POWER REQUIREMENTS  
Analog Supply Voltage Range  
Output Supply Voltage Range  
I
OE = OV  
OE = OV  
µA  
pF  
LEAK  
DD  
C
5
OUT  
DD  
V
2.7  
1.7  
3.0  
2.5  
82  
2.8  
1
3.6  
3.6  
97  
V
V
DD  
OV  
DD  
Operating, f  
Sleep mode  
= 20MHz at -0.5dB FS  
INA or B  
mA  
µA  
Analog Supply Current  
I
VDD  
Shutdown, clock idle, PD = OE = OV  
15  
DD  
Operating, C = 15pF , f  
L
-0.5dB FS  
= 20MHz at  
INA or B  
13  
mA  
Output Supply Current  
I
OVDD  
Sleep mode  
100  
2
µA  
µA  
Shutdown, clock idle, PD = OE = OV  
10  
DD  
4
_______________________________________________________________________________________  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
ELECTRICAL CHARACTERISTICS (continued)  
(V  
= +3V, OV  
= +2.5V; 0.1µF and 1.0µF capacitors from REFP, REFN, and COM to GND; REFOUT connected to REFIN through  
DD  
DD  
a 10kresistor, V = 2V  
(differential w.r.t. COM), C = 10pF at digital outputs (Note 5), f = 83.333MHz (50% duty cycle), T =  
CLK A  
IN  
p-p  
L
T
MIN  
to T  
, unless otherwise noted. Typical values are at T = +25°C.)  
MAX A  
PARAMETER  
SYMBOL  
CONDITIONS  
= 20MHz at -0.5dB FS  
MIN  
TYP  
246  
8.4  
3
MAX UNITS  
Operating, f  
Sleep mode  
291  
mW  
INA or B  
Power Dissipation  
PDISS  
µW  
Shutdown, clock idle, PD = OE = OV  
45  
DD  
Offset  
Gain  
0.2  
0.1  
mV/V  
%/V  
Power Supply Rejection  
PSRR  
TIMING CHARACTERISTICS  
CLK Rise to Output Data Valid  
Output Enable Time  
t
Figure 3 (Note 3)  
5
8
ns  
ns  
ns  
ns  
ns  
DO  
t
Figure 4  
10  
1.5  
ENABLE  
Output Disable Time  
t
Figure 4  
DISABLE  
CLK Pulse Width High  
CLK Pulse Width Low  
t
Figure 3 clock period: 12ns  
Figure 3 clock period: 12ns  
Wakeup from sleep mode (Note 4)  
Wakeup from shutdown (Note 4)  
6
6
1
1
CH  
t
CL  
0.28  
1.5  
Wake-Up Time  
t
µs  
WAKE  
CHANNEL-TO-CHANNEL MATCHING  
Crosstalk  
f
f
f
= 20MHz at -0.5dB FS  
= 20MHz at -0.5dB FS  
= 20MHz at -0.5dB FS  
-70  
dB  
dB  
INA or B  
INA or B  
INA or B  
Gain Matching  
0.02  
0.25  
0.2  
Phase Matching  
degrees  
Note 1: SNR, SINAD, THD, SFDR, and HD3 are based on an analog input voltage of -0.5dB FS, referenced to a +1.024V full-scale  
input voltage range.  
Note 2: Intermodulation distortion is the total power of the intermodulation products relative to the individual carrier. This number is  
6dB or better, if referenced to the two-tone envelope.  
Note 3: Digital outputs settle to V , V . Parameter guaranteed by design.  
IH IL  
Note 4: With REFIN driven externally, REFP, COM, and REFN are left floating while powered down.  
Note 5: Equivalent dynamic performance is obtainable over full OV  
range with reduced C .  
DD  
L
Typical Operating Characteristics  
(V  
= +3V, OV  
= +2.5V, internal reference, differential input at -0.5dB FS, f  
= 80.0005678MHz, C 10pF. T = +25°C,  
DD  
DD  
CLK L A  
unless otherwise noted.)  
FFT PLOT CHA (8192-POINT RECORD,  
DIFFERENTIAL INPUT)  
FFT PLOT CHB (8192-POINT RECORD,  
DIFFERENTIAL INPUT)  
FFT PLOT CHA (8192-POINT RECORD,  
DIFFERENTIAL INPUT)  
0
-10  
-20  
-30  
-40  
-50  
-60  
-70  
-80  
-90  
-100  
0
-10  
-20  
-30  
-40  
-50  
-60  
-70  
-80  
-90  
-100  
0
f
f
f
= 19.9123MHz  
= 24.9123MHz  
= 80.000568MHz  
CHA  
INA  
INB  
CLK  
f
f
f
= 6.0449MHz  
= 7.5099MHz  
= 80.000568MHz  
f
f
f
= 6.0449MHz  
= 7.5099MHz  
= 80.000568MHz  
CHB  
INA  
INB  
CLK  
INA  
INB  
CLK  
-10 CHA  
-20  
AINA = -0.52 dB FS  
AINA = -0.46dB FS  
AINB = -0.52dB FS  
-30  
-40  
-50  
-60  
-70  
-80  
-90  
-100  
0
5
10 15 20 25 30 35 40  
ANALOG INPUT FREQUENCY (MHz)  
0
5
10 15 20 25 30 35 40  
ANALOG INPUT FREQUENCY (MHz)  
0
5
10 15 20 25 30 35 40  
ANALOG INPUT FREQUENCY (MHz)  
_______________________________________________________________________________________  
5
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
Typical Operating Characteristics (continued)  
(V  
= +3V, OV  
= +2.5V, internal reference, differential input at -0.5dB FS, f  
= 80.0005678MHz, C 10pF. T = +25°C,  
DD  
DD  
CLK L A  
unless otherwise noted.)  
FFT PLOT CHB (8192-POINT RECORD,  
FFT PLOT CHA (8192-POINT RECORD,  
DIFFERENTIAL INPUT)  
FFT PLOT CHB (8192-POINT RECORD,  
DIFFERENTIAL INPUT)  
DIFFERENTIAL INPUT)  
0
-10  
-20  
-30  
-40  
-50  
-60  
-70  
-80  
-90  
-100  
0
-10  
-20  
-30  
-40  
-50  
-60  
-70  
-80  
-90  
-100  
0
-10  
-20  
-30  
-40  
-50  
-60  
-70  
-80  
-90  
-100  
CHB  
f
f
f
= 40.4202MHz  
= 47.0413MHz  
= 80.000568MHz  
f
f
f
= 19.9123MHz  
= 24.9123MHz  
= 80.000568MHz  
f
f
f
= 40.4202MHz  
= 47.0413MHz  
= 80.000568MHz  
INA  
INB  
CLK  
INA  
INB  
CLK  
INA  
INB  
CLK  
CHB  
CHA  
AINA = -0.52dB FS  
AINB = -0.53 dB FS  
AINB = -0.53dB FS  
0
5
10 15 20 25 30 35 40  
ANALOG INPUT FREQUENCY (MHz)  
0
5
10 15 20 25 30 35 40  
ANALOG INPUT FREQUENCY (MHz)  
0
5
10 15 20 25 30 35 40  
ANALOG INPUT FREQUENCY (MHz)  
TWO-TONE IMD PLOT (8192-POINT RECORD,  
SIGNAL-TO-NOISE RATIO vs.  
ANALOG INPUT FREQUENCY  
SIGNAL-TO-NOISE + DISTORTION  
vs. ANALOG INPUT FREQUENCY  
COHERENT SAMPLING)  
0
61  
60  
59  
58  
57  
56  
55  
61  
60  
59  
58  
57  
f
f
f
f
= 38.1545676MHz  
= 41.9631884MHz  
= 80.0005678MHz  
IN1  
IN1  
IN2  
CLK  
-10  
-20  
-30  
-40  
-50  
-60  
-70  
-80  
-90  
-100  
CHA  
AIN = 6.5dB FS  
f
IN2  
TWO-TONE ENVELOPE =  
-0.52dB FS  
CHB  
CHA  
CHB  
2nd ORDER IMD  
100  
100  
10  
10  
0
5
10 15 20 25 30 35 40  
ANALOG INPUT FREQUENCY (MHz)  
ANALOG INPUT FREQUENCY (MHz)  
ANALOG INPUT FREQUENCY (MHz)  
FULL-POWER INPUT BANDWIDTH vs.  
ANALOG INPUT FREQUENCY  
(SINGLE-ENDED)  
TOTAL HARMONIC DISTORTION vs.  
ANALOG INPUT FREQUENCY  
SPURIOUS-FREE DYNAMIC RANGE vs.  
ANALOG INPUT FREQUENCY  
-65  
-68  
-71  
-74  
-77  
6
4
87  
83  
79  
75  
71  
67  
63  
CHB  
2
0
CHA  
CHB  
-2  
CHA  
-4  
-6  
-8  
-80  
100  
100  
1
10  
100  
1000  
10  
10  
ANALOG INPUT FREQUENCY (MHz)  
ANALOG INPUT FREQUENCY (MHz)  
ANALOG INPUT FREQUENCY (MHz)  
6
_______________________________________________________________________________________  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
Typical Operating Characteristics (continued)  
(V  
= +3V, OV  
= +2.5V, internal reference, differential input at -0.5dB FS, f  
= 80.0005678MHz, C 10pF. T = +25°C,  
DD  
DD  
CLK L A  
unless otherwise noted.)  
SMALL-SIGNAL INPUT BANDWIDTH vs.  
SIGNAL-TO-NOISE RATIO vs.  
ANALOG INPUT FREQUENCY  
(SINGLE-ENDED)  
SIGNAL-TO-NOISE + DISTORTION vs.  
INPUT POWER (f = 20MHz)  
IN  
INPUT POWER (f = 20MHz)  
IN  
6
4
65  
60  
55  
50  
45  
60  
58  
56  
54  
52  
50  
V
= 100mVp-p  
IN  
2
0
-2  
-4  
-6  
-8  
-9 -8 -7 -6 -5 -4 -3 -2 -1  
INPUT POWER (dB FS)  
0
-9 -8 -7 -6 -5 -4 -3 -2 -1  
INPUT POWER (dB FS)  
0
1
10  
100  
1000  
ANALOG INPUT FREQUENCY (MHz)  
TOTAL HARMONIC DISTORTION  
SPURIOUS-FREE DYNAMIC RANGE  
INTEGRAL NONLINEARITY  
(BEST-STRAIGHT-LINE FIT)  
vs. INPUT POWER (f = 20MHz)  
vs. INPUT POWER (f = 20MHz)  
IN  
IN  
1.0  
0.8  
80  
76  
72  
68  
64  
60  
-60  
-64  
-68  
-72  
-76  
-80  
0.6  
0.4  
0.2  
0
-0.2  
-0.4  
-0.6  
-0.8  
-1.0  
-9 -8 -7 -6 -5 -4 -3 -2 -1  
INPUT POWER (dB FS)  
0
-9 -8 -7 -6 -5 -4 -3 -2 -1  
INPUT POWER (dB FS)  
0
0
128 256 384 512 640 768 896 1024  
DIGITAL OUTPUT CODE  
GAIN ERROR vs. TEMPERATURE,  
OFFSET ERROR vs. TEMPERATURE,  
EXTERNAL REFERENCE (V  
= +2.048V)  
EXTERNAL REFERENCE (V  
= +2.048V)  
DIFFERENTIAL NONLINEARITY  
REFIN  
REFIN  
1.0  
0.8  
4
5
3
CHB  
3
2
0.6  
CHB  
0.4  
0.2  
1
0
1
-0.2  
-0.4  
-0.6  
-0.8  
-1.0  
-1  
-3  
-5  
CHA  
0
CHA  
-1  
-2  
0
128 256 384 512 640 768 896 1024  
DIGITAL OUTPUT CODE  
-40  
-15  
10  
35  
60  
85  
-40  
-15  
10  
35  
60  
85  
TEMPERATURE (°C)  
TEMPERATURE (°C)  
_______________________________________________________________________________________  
7
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
Typical Operating Characteristics (continued)  
(V  
= +3V, OV  
= +2.5V, internal reference, differential input at -0.5dB FS, f  
= 80.0005678MHz, C 10pF. T = +25°C,  
DD  
DD  
CLK L A  
unless otherwise noted.)  
ANALOG POWER-DOWN CURRENT  
vs. ANALOG POWER SUPPLY  
ANALOG SUPPLY CURRENT  
vs. ANALOG SUPPLY VOLTAGE  
ANALOG SUPPLY CURRENT vs. TEMPERATURE  
2.0  
1.6  
1.2  
0.8  
0.4  
0
100  
100  
90  
80  
70  
60  
50  
OE = PD = OV  
DD  
90  
80  
70  
60  
50  
2.70 2.85 3.00 3.15 3.30 3.45 3.60  
(V)  
-40  
-15  
10  
35  
60  
85  
2.70 2.85 3.00 3.15 3.30 3.45 3.60  
V
DD  
TEMPERATURE (°C)  
V
DD  
(V)  
SFDR, SNR, THD, SINAD  
vs. CLOCK DUTY CYCLE  
INTERNAL REFERENCE VOLTAGE  
vs. ANALOG SUPPLY VOLTAGE  
80  
2.075  
f
f
= 24.9123MHz  
= 19.9123MHz  
INA  
INB  
SFDR  
75  
70  
65  
60  
55  
50  
2.065  
2.055  
2.045  
2.035  
2.025  
THD  
SNR  
SINAD  
30 35 40 45 50 55 60 65 70  
CLOCK DUTY CYCLE (%)  
2.70 2.85 3.00 3.15 3.30 3.45 3.60  
V
DD  
(V)  
INTERNAL REFERENCE VOLTAGE  
vs. TEMPERATURE  
OUTPUT NOISE HISTOGRAM (DC INPUT)  
140000  
120000  
100000  
80000  
60000  
40000  
20000  
0
2.10  
2.08  
2.06  
2.04  
2.02  
2.00  
129377  
0
965  
N-1  
730  
N+1  
0
N-2  
N
N+2  
-40  
-15  
10  
35  
60  
85  
DIGITAL OUTPUT NOISE  
TEMPERATURE (°C)  
8
_______________________________________________________________________________________  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
Pin Description  
PIN  
NAME  
FUNCTION  
1
COM  
Common-Mode Voltage Input/Output. Bypass to GND with a 0.1µF capacitor.  
Analog Supply Voltage. Bypass to GND with a capacitor combination of 2.2µF in parallel with  
0.1µF.  
2, 6, 11, 14, 15  
V
DD  
3, 7, 10, 13, 16  
GND  
INA+  
INA-  
INB-  
INB+  
CLK  
Analog Ground  
4
5
Channel APositive Analog Input. For single-ended operation, connect signal source to INA+.  
Channel ANegative Analog Input. For single-ended operation, connect INA- to COM.  
Channel BNegative Analog Input. For single-ended operation, connect INB- to COM.  
Channel BPositive Analog Input. For single-ended operation, connect signal source to INB+.  
Converter Clock Input  
8
9
12  
T/B selects the ADC digital output format.  
High: Twos complement.  
Low: Straight offset binary.  
17  
18  
19  
20  
T/B  
SLEEP  
PD  
Sleep Mode Input.  
High: Deactivates the two ADCs, but leaves the reference bias circuit active.  
Low: Normal operation.  
Power-Down Input.  
High: Power-down mode.  
Low: Normal operation.  
Output Enable Input.  
High: Digital outputs disabled.  
Low: Digital outputs enabled.  
OE  
21  
22  
D9B  
D8B  
D7B  
D6B  
D5B  
D4B  
D3B  
D2B  
D1B  
D0B  
OGND  
Three-State Digital Output, Bit 9 (MSB), Channel B  
Three-State Digital Output, Bit 8, Channel B  
Three-State Digital Output, Bit 7, Channel B  
Three-State Digital Output, Bit 6, Channel B  
Three-State Digital Output, Bit 5, Channel B  
Three-State Digital Output, Bit 4, Channel B  
Three-State Digital Output, Bit 3, Channel B  
Three-State Digital Output, Bit 2, Channel B  
Three-State Digital Output, Bit 1, Channel B  
Three-State Digital Output, Bit 0 (LSB), Channel B  
Output Driver Ground  
23  
24  
25  
26  
27  
28  
29  
30  
31, 34  
Output Driver Supply Voltage. Bypass to OGND with a capacitor combination of 2.2µF in parallel  
with 0.1µF.  
32, 33  
OV  
DD  
35  
36  
37  
38  
39  
D0A  
D1A  
D2A  
D3A  
D4A  
Three-State Digital Output, Bit 0 (LSB), Channel A  
Three-State Digital Output, Bit 1, Channel A  
Three-State Digital Output, Bit 2, Channel A  
Three-State Digital Output, Bit 3, Channel A  
Three-State Digital Output, Bit 4, Channel A  
_______________________________________________________________________________________  
9
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
Pin Description (continued)  
PIN  
40  
41  
42  
43  
44  
NAME  
D5A  
D6A  
D7A  
D8A  
D9A  
FUNCTION  
Three-State Digital Output, Bit 5, Channel A  
Three-State Digital Output, Bit 6, Channel A  
Three-State Digital Output, Bit 7, Channel A  
Three-State Digital Output, Bit 8, Channel A  
Three-State Digital Output, Bit 9 (MSB), Channel A  
Internal Reference Voltage Output. May be connected to REFIN through a resistor or a resistor  
divider.  
45  
46  
47  
REFOUT  
REFIN  
REFP  
Reference Input. V  
= 2 x (V  
- V  
REFN  
). Bypass to GND with a >1nF capacitor.  
REFIN  
REFP  
Positive Reference Input/Output. Conversion range is (V  
with a > 0.1µF capacitor.  
- V  
REFN  
). Bypass to GND  
REFP  
Negative Reference Input/Output. Conversion range is (V  
with a > 0.1µF capacitor.  
- V  
REFN  
). Bypass to GND  
REFP  
48  
REFN  
capacitors C2a and C2b. The amplifiers are used to  
charge capacitors C1a and C1b to the same values  
originally held on C2a and C2b. These values are then  
presented to the first-stage quantizers and isolate the  
pipelines from the fast-changing inputs. The wide input  
bandwidth T/H amplifiers allow the MAX1181 to track  
and sample/hold analog inputs of high frequencies  
(> Nyquist). Both ADC inputs (INA+, INB+, INA-, and  
INB-) can be driven either differentially or single-ended.  
Match the impedance of INA+ and INA-, as well as  
INB+ and INB-, and set the common-mode voltage to  
Detailed Description  
The MAX1181 uses a nine-stage, fully-differential  
pipelined architecture (Figure 1), that allows for high-  
speed conversion while minimizing power consump-  
tion. Samples taken at the inputs move progressively  
through the pipeline stages every half clock cycle.  
Counting the delay through the output latch, the clock-  
cycle latency is five clock cycles.  
1.5-bit (two-comparator) flash ADCs convert the held-  
input voltages into a digital code. The digital-to-analog  
converters (DACs) convert the digitized results back  
into analog voltages, which are then subtracted from  
the original held-input signals. The resulting error sig-  
nals are then multiplied by two, and the residues are  
passed along to the next pipeline stages where the  
process is repeated until the signals have been  
processed by all nine stages. Digital error correction  
compensates for ADC comparator offsets in each of  
these pipeline stages and ensures no missing codes.  
midsupply (V /2) for optimum performance.  
DD  
Analog Inputs and Reference  
Configurations  
The full-scale range of the MAX1181 is determined by  
the internally generated voltage difference between  
REFP (V /2 + V  
REFIN  
/4) and REFN (V /2 -  
DD  
DD  
REFIN  
V
/4). The full-scale range for both on-chip ADCs is  
adjustable through the REFIN pin, which is provided for  
this purpose.  
Input Track-and-Hold (T/H) Circuits  
Figure 2 displays a simplified functional diagram of the  
input track-and-hold (T/H) circuits in both track-and-  
hold mode. In track mode, switches S1, S2a, S2b, S4a,  
S4b, S5a and S5b are closed. The fully-differential cir-  
cuits sample the input signals onto the two capacitors  
(C2a and C2b) through switches S4a and S4b. S2a and  
S2b set the common mode for the amplifier input, and  
open simultaneously with S1, sampling the input wave-  
form. Switches S4a and S4b are then opened before  
switches S3a and S3b connect capacitors C1a and  
C1b to the output of the amplifier and switch S4c is  
closed. The resulting differential voltages are held on  
REFOUT, REFP, COM (V /2) and REFN are internally  
DD  
buffered low-impedance outputs.  
The MAX1181 provides three modes of reference opera-  
tion:  
Internal reference mode  
Buffered external reference mode  
Unbuffered external reference mode  
In the internal reference mode, connect the internal ref-  
erence output REFOUT to REFIN through a resistor  
(e.g., 10k) or resistor divider, if an application  
requires a reduced full-scale range. For stability and  
10 ______________________________________________________________________________________  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
V
IN  
V
IN  
V
OUT  
V
OUT  
x2  
x2  
Σ
Σ
T/H  
T/H  
FLASH  
ADC  
FLASH  
ADC  
DAC  
DAC  
1.5 BITS  
1.5 BITS  
2-BIT FLASH  
ADC  
2-BIT FLASH  
ADC  
STAGE 1  
STAGE 2  
STAGE 8  
STAGE 9  
STAGE 1  
STAGE 2  
STAGE 8  
STAGE 9  
DIGITAL CORRECTION LOGIC  
10  
DIGITAL CORRECTION LOGIC  
10  
T/H  
T/H  
D9A–D0A  
D9B–D0B  
V
INA  
V
INB  
V
INA  
V
INB  
= INPUT VOLTAGE BETWEEN INA+ AND INA- (DIFFERENTIAL OR SINGLE-ENDED)  
= INPUT VOLTAGE BETWEEN INB+ AND INB- (DIFFERENTIAL OR SINGLE-ENDED)  
Figure 1. Pipelined Architecture––Stage Blocks  
noise filtering purposes, bypass REFIN with a >10nF  
capacitor to GND. In internal reference mode, REFOUT,  
COM, REFP, and REFN become low-impedance out-  
puts.  
SNR = 20 log (1 / [2π x f  
t ]),  
AJ  
dB  
10  
IN  
where f represents the analog input frequency and  
IN  
t
AJ  
is the time of the aperture jitter.  
Clock jitter is especially critical for undersampling  
applications. The clock input should always be consid-  
ered as an analog input and routed away from any ana-  
log input or other digital signal lines.  
In the buffered external reference mode, adjust the ref-  
erence voltage levels externally by applying a stable  
and accurate voltage at REFIN. In this mode, COM,  
REFP, and REFN become outputs. REFOUT may be left  
open or connected to REFIN through a >10kresistor.  
In the unbuffered external reference mode, connect  
REFIN to GND. This deactivates the on-chip reference  
buffers for REFP, COM, and REFN. With their buffers  
shut down, these nodes become high impedance and  
may be driven through separate external reference  
sources.  
The MAX1181 clock input operates with a voltage thresh-  
old set to V /2. Clock inputs with a duty cycle other  
DD  
than 50% must meet the specifications for high and low  
periods as stated in the Electrical Characteristics.  
System Timing Requirements  
Figure 3 depicts the relationship between the clock  
input, analog input, and data output. The MAX1181  
samples at the rising edge of the input clock. Output  
data for channels A and B is valid on the next rising  
edge of the input clock. The output data has an internal  
latency of five clock cycles. Figure 4 also determines  
the relationship between the input clock parameters  
and the valid output data on channels A and B.  
Clock Input (CLK)  
The MAX1181s CLK input accepts CMOS-compatible  
clock signals. Since the interstage conversion of the  
device depends on the repeatability of the rising and  
falling edges of the external clock, use a clock with low  
jitter and fast rise and fall times (< 2ns). In particular,  
sampling occurs on the rising edge of the clock signal,  
requiring this edge to provide lowest possible jitter. Any  
significant aperture jitter would limit the SNR perfor-  
mance of the on-chip ADCs as follows:  
Digital Output Data, Output Data Format  
Selection (T/B), Output Enable (OE)  
All digital outputs, D0AD9A (Channel A) and D0BD9B  
(Channel B), are TTL/CMOS logic-compatible. There is a  
______________________________________________________________________________________ 11  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
INTERNAL  
COM  
S5a  
BIAS  
S2a  
C1a  
S3a  
S4a  
S4b  
INA+  
INA-  
OUT  
OUT  
C2a  
C2b  
S4c  
S1  
C1b  
S3b  
S5b  
COM  
S2b  
INTERNAL  
BIAS  
CLK  
INTERNAL  
NONOVERLAPPING  
CLOCK SIGNALS  
HOLD  
HOLD  
INTERNAL  
BIAS  
TRACK  
TRACK  
COM  
S5a  
S2a  
C1a  
S3a  
S4a  
S4b  
INB+  
INB-  
OUT  
OUT  
C2a  
C2b  
S4c  
S1  
MAX1181  
C1b  
S3b  
S5b  
COM  
S2b  
INTERNAL  
BIAS  
Figure 2. MAX1181 T/H Amplifiers  
five clock cycle latency between any particular sample  
and its corresponding output data. The output coding  
can be chosen to be either straight offset binary or twos  
complement (Table 1) controlled by a single pin (T/B).  
Pull T/B low to select offset binary and high to activate  
twos complement output coding. The capacitive load  
on the digital outputs D0AD9A and D0BD9B should  
be kept as low as possible (<15pF), to avoid large digi-  
tal currents that could feed back into the analog portion  
of the MAX1181, thereby degrading its dynamic perfor-  
mance. Using buffers on the digital outputs of the ADCs  
can further isolate the digital outputs from heavy capaci-  
tive loads. To further improve the dynamic performance  
12 ______________________________________________________________________________________  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
5 CLOCK-CYCLE LATENCY  
N
N + 1  
N + 2  
N + 3  
N + 4  
N + 5  
N + 6  
ANALOG INPUT  
CLOCK INPUT  
t
D0  
t
CH  
t
CL  
DATA OUTPUT  
N - 6  
N - 6  
N - 5  
N - 5  
N - 4  
N - 4  
N - 3  
N - 3  
N - 2  
N - 1  
N - 1  
N
N
N + 1  
D9AD0A  
DATA OUTPUT  
N - 2  
N + 1  
D9BD0B  
Figure 3. System Timing Diagram  
Table 1. MAX1181 Output Codes For Differential Inputs  
STRAIGHT OFFSET  
BINARY  
DIFFERENTIAL INPUT  
VOLTAGE*  
TWOS COMPLEMENT  
DIFFERENTIAL INPUT  
T/B = 1  
T/B = 0  
V
511/512  
+FULL SCALE - 1LSB  
+ 1 LSB  
11 1111 1111  
10 0000 0001  
10 0000 0000  
01 1111 1111  
00 0000 0001  
00 0000 0000  
01 1111 1111  
00 0000 0001  
00 0000 0000  
11 1111 1111  
10 0000 0001  
10 0000 0000  
REF  
V
1/512  
REF  
0
Bipolar Zero  
-V  
1/512  
- 1 LSB  
REF  
-V  
511/512  
512/512  
- FULL SCALE + 1 LSB  
- FULL SCALE  
REF  
REF  
-V  
*V  
REF  
= V  
- V  
REFP REFN  
of the MAX1181 small-series resistors (e.g., 100), add  
to the digital output paths, close to the MAX1181.  
value prior to the power-down. Pulling OE high, forces  
the digital outputs into a high-impedance state.  
Figure 4 displays the timing relationship between out-  
put enable and data output valid, as well as power-  
down/wake-up and data output valid.  
Applications Information  
Figure 5 depicts a typical application circuit containing  
two single-ended to differential converters. The internal  
Power-Down (PD) and Sleep  
(SLEEP) Modes  
The MAX1181 offers two power-save modes; sleep and  
full power-down mode. In sleep mode (SLEEP = 1),  
only the reference bias circuit is active (both ADCs are  
disabled) and current consumption is reduced to  
2.8mA.  
reference provides a V /2 output voltage for level-  
DD  
shifting purposes. The input is buffered and then split  
to a voltage follower and inverter. One lowpass filter per  
ADC suppresses some of the wideband noise associat-  
ed with high-speed operational amplifiers. The user  
may select the R  
and C values to optimize the fil-  
IN  
ISO  
ter performance to suit a particular application. For the  
application in Figure 5, a R of 50is placed before  
ISO  
To enter full power-down mode, pull PD high. With OE  
simultaneously low, all outputs are latched at the last  
the capacitive load to prevent ringing and oscillation.  
______________________________________________________________________________________________________ 13  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
The 22pF C capacitor acts as a small bypassing  
IN  
capacitor.  
OE  
Using Transformer Coupling  
An RF transformer (Figure 6) provides an excellent  
solution to convert a single-ended source signal to a  
fully-differential signal, required by the MAX1181 for  
optimum performance. Connecting the center tap of the  
t
t
DISABLE  
ENABLE  
OUTPUT  
HIGH-Z  
HIGH-Z  
HIGH-Z  
VALID DATA  
VALID DATA  
D9AD0A  
transformer to COM provides a V /2 DC level shift to  
DD  
OUTPUT  
D9BD0B  
HIGH-Z  
the input. Although a 1:1 transformer is shown, a step-  
up transformer may be selected to reduce the drive  
requirements. A reduced signal swing from the input  
driver, such as an op amp, may also improve the over-  
all distortion.  
Figure 4. Output Timing Diagram  
Grounding, Bypassing,  
and Board Layout  
In general, the MAX1181 provides better SFDR and  
THD with fully-differential input signals, than a single-  
ended drive, especially for high input frequencies. In  
differential input mode, even-order harmonics are lower  
as both inputs (INA+, INA- and/or INB+, INB-) are bal-  
anced, and each of the ADC inputs only require half the  
signal swing compared to single-ended mode.  
The MAX1181 requires high-speed board layout design  
techniques. Locate all bypass capacitors as close to  
the device as possible, preferably on the same side as  
the ADC, using surface-mount devices for minimum  
inductance. Bypass V , REFP, REFN, and COM with  
DD  
two parallel 0.1µF ceramic capacitors and a 2.2µF  
bipolar capacitor to GND. Follow the same rules to  
Single-Ended AC-Coupled Input Signal  
Figure 7 shows an AC-coupled, single-ended applica-  
tion. Amplifiers, like the MAX4108, provide high-speed,  
high bandwidth, low-noise, and low distortion to main-  
tain the integrity of the input signal.  
bypass the digital supply (OV ) to OGND. Multilayer  
DD  
boards with separate ground and power planes, pro-  
duce the highest level of signal integrity. Consider the  
use of a split ground plane arranged to match the phys-  
ical location of the analog ground (GND) and the digital  
output driver ground (OGND) on the ADCs package.  
The two ground planes should be joined at a single  
point, such that the noisy digital ground currents do not  
interfere with the analog ground plane. The ideal loca-  
tion of this connection can be determined experimental-  
ly at a point along the gap between the two ground  
planes, which produces optimum results. Make this  
connection with a low-value, surface-mount resistor (1Ω  
to 5), a ferrite bead, or a direct short. Alternatively, all  
ground pins could share the same ground plane, if the  
ground plane is sufficiently isolated from any noisy, dig-  
ital systems ground plane (e.g., downstream output  
buffer or DSP ground plane). Route high-speed digital  
signal traces away from the sensitive analog traces of  
either channel. Make sure to isolate the analog input  
lines to each respective converter to minimize channel-  
to-channel crosstalk. Keep all signal lines short and  
free of 90 degree turns.  
Typical QAM Demodulation Application  
The most frequently used modulation technique for dig-  
ital communications application is the Quadrature  
Amplitude Modulation (QAM). QAMs are typically found  
in spread-spectrum based systems. A QAM signal rep-  
resents a carrier frequency modulated in both ampli-  
tude and phase. At the transmitter, modulating the  
baseband signal with quadrature outputs, a local oscil-  
lator followed by subsequent up-conversion can gener-  
ate the QAM signal. The result is an in-phase (I) and a  
quadrature (Q) carrier component, where the Q compo-  
nent is 90 degrees phase-shifted with respect to the in-  
phase component. At the receiver, the QAM signal is  
divided down into its I and Q components, essentially  
representing the modulation process reversed. Figure 8  
displays the demodulation process performed in the  
analog domain, using the dual-matched, +3V, 10-bit  
ADCs, MAX1181 and the MAX2451 quadrature demod-  
ulators, to recover and digitize the I and Q baseband  
signals. Before being digitized by the MAX1181, the  
mixed-down signal components may be filtered by  
matched analog filters, such as Nyquist or pulse-shap-  
ing filters which remove any unwanted images from the  
mixing process, enhances the overall signal-to-noise  
(SNR) performance, and minimizes intersymbol interfer-  
ence.  
14 ______________________________________________________________________________________  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
+5V  
0.1µF  
LOWPASS FILTER  
INA+  
MAX4108  
R
ISO  
50Ω  
0.1µF  
300Ω  
C
IN  
22pF  
0.1µF  
-5V  
600Ω  
600Ω  
300Ω  
COM  
0.1µF  
+5V  
+5V  
0.1µF  
0.1µF  
600Ω  
INPUT  
0.1µF  
0.1µF  
LOWPASS FILTER  
MAX4108  
300Ω  
300Ω  
INA-  
MAX4108  
R
ISO  
C
IN  
22pF  
50Ω  
-5V  
-5V  
+5V  
300Ω  
300Ω  
600Ω  
MAX1181  
0.1µF  
0.1µF  
LOWPASS FILTER  
INB+  
MAX4108  
R
ISO  
0.1µF  
300Ω  
C
IN  
22pF  
50Ω  
-5V  
600Ω  
600Ω  
300Ω  
0.1µF  
+5V  
+5V  
0.1µF  
0.1µF  
600Ω  
INPUT  
0.1µF  
0.1µF  
LOWPASS FILTER  
MAX4108  
300Ω  
300Ω  
INB-  
MAX4108  
R
ISO  
50Ω  
C
IN  
22pF  
-5V  
-5V  
300Ω  
300Ω  
600Ω  
Figure 5. Typical Application for Single-Ended to Differential Conversion  
______________________________________________________________________________________ 15  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
Dynamic Parameter Definitions  
25Ω  
INA+  
Aperture Jitter  
22pF  
Figure 9 depicts the aperture jitter (t ), which is the  
AJ  
sample-to-sample variation in the aperture delay.  
0.1µF  
1
2
6
5
4
T1  
V
IN  
Aperture Delay  
Aperture delay (t ) is the time defined between the  
AD  
COM  
N.C.  
falling edge of the sampling clock and the instant when  
an actual sample is taken (Figure 9).  
2.2µF  
0.1µF  
3
MINICIRCUITS  
Signal-to-Noise Ratio (SNR)  
For a waveform perfectly reconstructed from digital  
samples, the theoretical maximum SNR is the ratio of  
the full-scale analog input (RMS value) to the RMS  
quantization error (residual error).  
TT16  
25Ω  
INA-  
INB+  
22pF  
22pF  
MAX1181  
25Ω  
The ideal, theoretical minimum analog-to-digital noise is  
caused by quantization error only and results directly  
from the ADCs resolution (N-Bits):  
0.1µF  
SNR  
= 6.02  
N + 1.76  
dB  
dB[max]  
dB  
1
2
6
5
4
T1  
V
IN  
In reality, there are other noise sources besides quanti-  
zation noise; thermal noise, reference noise, clock jitter,  
etc. SNR is computed by taking the ratio of the RMS  
signal to the RMS noise, which includes all spectral  
components minus the fundamental, the first five har-  
monics, and the DC offset.  
N.C.  
2.2µF  
0.1µF  
3
MINICIRCUITS  
TT16  
25Ω  
INB-  
Signal-to-Noise Plus Distortion (SINAD)  
SINAD is computed by taking the ratio of the RMS sig-  
nal to all spectral components minus the fundamental  
and the DC offset.  
22pF  
Figure 6. Transformer-Coupled Input Drive  
Effective Number of Bits (ENOB)  
ENOB specifies the dynamic performance of an ADC at  
a specific input frequency and sampling rate. An ideal  
ADCs error consists of quantization noise only. ENOB  
is computed from:  
Static Parameter Definitions  
Integral Nonlinearity (INL)  
Integral nonlinearity is the deviation of the values on an  
actual transfer function from a straight line. This straight  
line can be either a best straight-line fit or a line drawn  
between the endpoints of the transfer function, once  
offset and gain errors have been nullified. The static lin-  
earity parameters for the MAX1181 are measured using  
the best straight-line fit method.  
SINAD 1.76  
dB  
dB  
ENOB =  
6.02  
dB  
Total Harmonic Distortion (THD)  
THD is typically the ratio of the RMS sum of the first four  
harmonics of the input signal to the fundamental itself.  
This is expressed as:  
Differential Nonlinearity (DNL)  
Differential nonlinearity is the difference between an  
actual step-width and the ideal value of 1LSB. A DNL  
error specification of less than 1LSB guarantees no  
missing codes and a monotonic transfer function.  
2
2
2
2
V2 + V3 + V4 + V5  
THD = 20 × log  
10  
V
1
16 ______________________________________________________________________________________  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
REFP  
1kΩ  
1kΩ  
R
V
IN  
ISO  
50Ω  
0.1µF  
INA+  
COM  
INA-  
MAX4108  
C
IN  
22pF  
100Ω  
100Ω  
REFN  
0.1µF  
R
50Ω  
ISO  
C
22pF  
IN  
REFP  
MAX1181  
1kΩ  
R
ISO  
50Ω  
V
IN  
0.1µF  
INB+  
MAX4108  
C
IN  
22pF  
100Ω  
100Ω  
1kΩ  
REFN  
0.1µF  
R
50Ω  
ISO  
INB-  
C
22pF  
IN  
Figure 7. Using an Op Amp for Single-Ended, AC-Coupled Input Drive  
MAX2451  
INA+  
INA-  
0°  
90°  
DSP POST  
PROCESSING  
MAX1181  
INB+  
INB-  
DOWNCONVERTER  
÷
8
Figure 8. Typical QAM Application, Using the MAX1181  
______________________________________________________________________________________ 17  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
where V is the fundamental amplitude, and V through  
1
2
V
are the amplitudes of the 2nd- through 5th-order  
harmonics.  
5
CLK  
Spurious-Free Dynamic Range (SFDR)  
SFDR is the ratio expressed in decibels of the RMS  
amplitude of the fundamental (maximum signal compo-  
nent) to the RMS value of the next largest spurious  
component, excluding DC offset.  
ANALOG  
INPUT  
t
AD  
t
AJ  
SAMPLED  
Intermodulation Distortion (IMD)  
The two-tone IMD is the ratio expressed in decibels of  
either input tone to the worst 3rd-order (or higher) inter-  
modulation products. The individual input tone levels  
are at -6.5dB full scale and their envelope is at -0.5dB  
full scale.  
DATA (T/H)  
HOLD  
TRACK  
TRACK  
T/H  
Figure 9. T/H Aperture Timing  
Chip Information  
TRANSISTOR COUNT: 10,811  
PROCESS: CMOS  
Functional Diagram  
V
DD  
OGND  
OV  
GND  
DD  
INA+  
10  
10  
OUTPUT  
DRIVERS  
PIPELINE  
ADC  
D9AD0A  
DEC  
T/H  
INA-  
CLK  
CONTROL  
OE  
INB+  
INB-  
10  
10  
PIPELINE  
ADC  
OUTPUT  
DRIVERS  
DEC  
T/H  
D9BD0B  
T/B  
PD  
SLEEP  
REFERENCE  
MAX1181  
REFOUT  
REFN COM REFP  
REFIN  
18 ______________________________________________________________________________________  
Dual 10-Bit, 80Msps, +3V, Low-Power ADC with  
Internal Reference and Parallel Outputs  
Package Information  
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are  
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.  
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19  
© 2001 Maxim Integrated Products  
Printed USA  
is a registered trademark of Maxim Integrated Products.  

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