19-1900; Rev 1; 5/06
12-Bit, 40Msps, 3.3V, Low-Power ADC
with Internal Reference
General Description
The MAX1421 is a 3.3V, 12-bit analog-to-digital con-
verter (ADC), featuring a fully-differential input,
pipelined, 12-stage ADC architecture with wideband
track-and-hold (T/H) and digital error correction incor-
porating a fully-differential signal path. The MAX1421 is
optimized for low-power, high-dynamic performance
applications in imaging and digital communications.
The converter operates from a single 3.3V supply, con-
suming only 188mW while delivering a typical signal-to-
noise ratio (SNR) of 66dB at an input frequency of
15MHz and a sampling frequency of 40Msps. The fully-
differential input stage has a small signal -3dB band-
width of 400MHz and may be operated with
single-ended inputs.
An internal 2.048V precision bandgap reference sets
the full-scale range of the ADC. A flexible reference
structure accommodates an internal or externally
applied buffered or unbuffered reference for applica-
tions requiring increased accuracy or a different input
voltage range.
In addition to low operating power, the MAX1421 fea-
tures two power-down modes, a reference power-down
and a shutdown mode. In reference power-down, the
internal bandgap reference is deactivated, resulting in
a typical 2mA supply current reduction. For idle peri-
ods, a full shutdown mode is available to maximize
power savings.
The MAX1421 provides parallel, offset binary, CMOS-
compatible three-state outputs.
The MAX1421 is available in a 7mm x 7mm, 48-pin
TQFP package, and is specified over the commercial
(0°C to +70°C) and the extended industrial (-40°C to
+85°C) temperature ranges.
Pin-compatible higher- and lower-speed versions of the
MAX1421 are also available. Please refer to the
MAX1420 data sheet for a frequency of 60Msps and
the MAX1422 data sheet for a frequency of 20Msps.
♦
Single 3.3V Power Supply
♦
67dB SNR at f
IN
= 5MHz
♦
66dB SNR at f
IN
= 15MHz
♦
Internal, 2.048V Precision Bandgap Reference
♦
Differential, Wideband Input T/H Amplifier
♦
Power-Down Modes
180mW (Reference Shutdown Mode)
10µW (Shutdown Mode)
♦
Space-Saving 48-Pin TQFP Package
Features
MAX1421
Ordering Information
PART*
MAX1421CCM
MAX1421ECM
MAX1421ECM+
TEMP RANGE
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
48 TQFP
48 TQFP
48 TQFP
PKG
CODE
C48-2
C48-2
C48-2
+Denotes
lead-free package.
Pin Configuration
AGND
AV
DD
CML
REFN
REFP
REFIN
AV
DD
AGND
PD
OE
D11
43
42
41
40
39
38
48
47
46
45
44
AGND
AV
DD
AV
DD
AGND
AGND
INP
INN
AGND
AGND
AV
DD
AV
DD
AGND
37
D10
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
36
35
34
33
32
31
30
29
28
27
26
25
D9
D8
D7
D6
DV
DD
DV
DD
DGND
DGND
D5
D4
D3
D2
________________________Applications
Medical Ultrasound Imaging
CCD Pixel Processing
Data Acquisition
Radar
IF and Baseband Digitization
MAX1421
AGND
AV
DD
AV
DD
AGND
CLK
CLK
Functional Diagram appears at end of data sheet.
48-TQFP
________________________________________________________________
Maxim Integrated Products
AGND
AV
DD
DV
DD
DGND
D0
D1
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.
12-Bit, 40Msps, 3.3V, Low-Power ADC
with Internal Reference
MAX1421
ABSOLUTE MAXIMUM RATINGS
AV
DD
, DV
DD
to AGND ..............................................-0.3V to +4V
DV
DD
, AV
DD
to DGND..............................................-0.3V to +4V
DGND to AGND.....................................................-0.3V to +0.3V
INP, INN, REFP, REFN, REFIN,
CML, CLK,
CLK,....................(AGND
- 0.3V) to (AV
DD
+ 0.3V)
D0–D11,
OE,
PD .......................(DGND - 0.3V) to (DV
DD
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
48-Pin TQFP (derate 12.5mW/°C above +70°C)........1000mW
Maximum Junction Temperature .....................................+150°C
Operating Temperature Ranges
MAX1421CCM ...................................................0°C to +70°C
MAX1421ECM ................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
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
AVDD
= V
DVDD
= 3.3V, AGND = DGND = 0, V
IN
= ±1.024V, differential input voltage at -0.5dB FS, internal reference,
f
CLK
= 40MHz (50% duty cycle), digital output load C
L
≈
10pF, T
A
≥
+25°C guaranteed by production test, T
A
< +25°C guarnateed
by design and characterization. Typical values are at T
A
= +25°C.)
PARAMETER
DC ACCURACY
Resolution
Differential Nonlinearity
Integral Nonlinearity
Midscale Offset
Midscale Offset Temperature
Coefficient
RES
DNL
INL
MSO
MSOTC
Internal reference (Note 1)
Gain Error
GE
External reference applied to REFIN (Note 2)
External reference applied to REFP, CML,
and REFN (Note 3)
Gain-Error Temperature
Coefficient
GETC
External reference applied to REFP, CML,
and REFN (Note 3)
f
IN
= 5MHz
f
IN
= 15MHz, T
A
= +25°C
f
IN
= 5MHz
f
IN
= 15MHz, T
A
= +25°C
f
IN
= 5MHz
f
IN
= 15MHz, T
A
= +25°C
f
IN
= 5MHz
f
IN
= 15MHz, T
A
= +25°C
f
IN
= 5MHz
f
IN
= 15MHz, T
A
= +25°C
f
IN1
= 11.569MHz, f
IN2
= 13.445MHz
(Note 4)
60
60
64
62
-5
-5
-1.5
T
A
= +25°C, no missing codes
T
A
= T
MIN
to T
MAX
T
A
= T
MIN
to T
MAX
-3
-1
±0.5
±2
±.75
3
✕
10
-4
+0.1
±3
±0.5
15
✕
10
-6
+5
+5
+1.5
%/°C
%FSR
+3
12
+1
Bits
LSB
LSB
%FSR
%/°C
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DYNAMIC PERFORMANCE (f
CLK
= 40MHz, 4096-point FFT)
Signal-to-Noise Ratio
Spurious-Free Dynamic Range
Total Harmonic Distortion
Signal-To-Noise Plus Distortion
Effective Number of Bits
Two-Tone Intermodulation
Distortion
SNR
SFDR
THD
SINAD
ENOB
IMD
TT
67
66
73
70
-74
-69
66
63.5
10.7
10.3
-80
-62
dB
dBc
dBc
dB
Bits
dBc
2
_______________________________________________________________________________________
12-Bit, 40Msps, 3.3V, Low-Power ADC
with Internal Reference
ELECTRICAL CHARACTERISTICS (continued)
(V
AVDD
= V
DVDD
= 3.3V, AGND = DGND = 0, V
IN
= ±1.024V, differential input voltage at -0.5dB FS, internal reference,
f
CLK
= 40MHz (50% duty cycle), digital output load C
L
≈
10pF, T
A
≥
+25°C guaranteed by production test, T
A
< +25°C guarnateed
by design and characterization. Typical values are at T
A
= +25°C.)
PARAMETER
Differential Gain
Differential Phase
ANALOG INPUTS (INP, INN, CML)
Input Resistance
Input Capacitance
Common-Mode Input Level
(Note 5)
Common-Mode Input Voltage
Range (Note 5)
Differential Input Range
Small-Signal Bandwidth
Large-Signal Bandwidth
Overvoltage Recovery
R
IN
C
IN
V
CML
V
CMVR
V
IN
BW
-3dB
FPBW
-3dB
OVR
V
INP
- V
INN
(Note 6)
(Note 7)
(Note 7)
1.5
✕
FS input
Either input to ground
Either input to ground
32.5
4
V
AVDD
×
0.5
V
CML
±5%
±V
DIFF
400
150
1
kΩ
pF
V
V
V
MHz
MHz
Clock
Cycle
SYMBOL
DG
DP
CONDITIONS
MIN
TYP
±1
±0.25
MAX
UNITS
%
degrees
MAX1421
INTERNAL REFERENCE (REFIN bypassed with 0.22µF in parallel with 1nF)
Common-Mode Reference Input
Voltage
Positive Reference Voltage
Range
Negative Reference Voltage
Range
Differential Reference Voltage
Range
Differential Reference
Temperature Coefficient
REFIN Input Resistance
REFIN Input Capacitance
REFIN Reference Input Voltage
V
CML
V
REFP
V
REFN
V
DIFF
REFTC
At CML
At REFP
At REFN
(Note 6)
V
AVDD
✕
0.5
V
CML
+ 0.512
V
CML
- 0.512
1.024
±5%
±100
V
V
V
V
ppm/°C
EXTERNAL REFERENCE (V
REFIN
= 2.048V)
R
IN
C
IN
V
REFIN
(Note 8)
5
10
2.048
±10%
(Note 6)
1.08
✕
0.92
✕
V
REFIN
/
V
REFIN
/
V
REFIN
/
2
2
2
-200
15
+200
kΩ
pF
V
Differential Reference Voltage
V
DIFF
V
EXTERNAL REFERENCE (V
REFIN
= AGND, reference voltage applied to REFP, REFN, and CML)
REFP, REFN, CML Input Current
REFP, REFN, CML Input
Capacitance
I
IN
C
IN
µA
pF
_______________________________________________________________________________________
3
12-Bit, 40Msps, 3.3V, Low-Power ADC
with Internal Reference
MAX1421
ELECTRICAL CHARACTERISTICS (continued)
(V
AVDD
= V
DVDD
= 3.3V, AGND = DGND = 0, V
IN
= ±1.024V, differential input voltage at -0.5dB FS, internal reference,
f
CLK
= 40MHz (50% duty cycle), digital output load C
L
≈
10pF, T
A
≥
+25°C guaranteed by production test, T
A
< +25°C guarnateed
by design and characterization. Typical values are at T
A
= +25°C.)
PARAMETER
Differential Reference Voltage
Range
CML Input Voltage Range
REFP Input Voltage Range
REFN Input Voltage Range
SYMBOL
V
DIFF
V
CML
V
REFP
V
REFN
(Note 6)
CONDITIONS
MIN
TYP
1.024
±10%
1.65
±10%
V
CML
+
V
DIFF
/ 2
V
CML
-
V
DIFF
/ 2
0.7
✕
V
DVDD
0.3
✕
V
DVDD
CLK,
CLK
Input Current
Input Capacitance
DIGITAL OUTPUTS (D0–D11)
Output Logic-High
Output Logic-Low
Three-State Leakage
Three-State Capacitance
POWER REQUIREMENTS
Analog Supply Voltage
Digital Supply Voltage
Analog Supply Current
Analog Supply Current with
Internal Reference in Shutdown
Analog Shutdown Current
Digital Supply Current
Digital Shutdown Current
Power Dissipation
Power-Supply Rejection Ratio
TIMING CHARACTERISTICS
Clock Frequency
Clock High
Clock Low
f
CLK
t
CH
t
CL
Figure 5
Figure 5, clock period 25ns
Figure 5, clock period 25ns
0.1
12.5
12.5
40.0
MHz
ns
ns
P
DISS
PSRR
I
DVDD
PD = DV
DD
Analog power
(Note 9)
188
±1
V
AVDD
V
DVDD
I
AVDD
REFIN = AGND
PD = DV
DD
5.5
20
214
3.135
2.7
3.3
3.3
52
50
3.465
3.6
65
63
20
V
V
mA
mA
µA
mA
µA
mW
mV/V
V
OH
V
OL
I
OH
= 200µA
I
OL
= -200µA
V
DVDD
- 0.5
0
-10
2
V
DVDD
0.5
+10
V
V
µA
pF
PD
OE
-20
-20
10
±330
+20
+20
pF
µA
MAX
UNITS
V
V
V
V
DIGITAL INPUTS (CLK,
CLK, OE,
PD)
Input Logic-High
Input Logic-Low
V
IH
V
IL
V
V
4
_______________________________________________________________________________________
12-Bit, 40Msps, 3.3V, Low-Power ADC
with Internal Reference
ELECTRICAL CHARACTERISTICS (continued)
(V
AVDD
= V
DVDD
= 3.3V, AGND = DGND = 0, V
IN
= ±1.024V, differential input voltage at -0.5dB FS, internal reference,
f
CLK
= 40MHz (50% duty cycle), digital output load C
L
≈
10pF, T
A
≥
+25°C guaranteed by production test, T
A
< +25°C guarnateed
by design and characterization. Typical values are at T
A
= +25°C.)
PARAMETER
Pipeline Delay (Latency)
Aperture Delay
Aperture Jitter
Data Output Delay
Bus Enable Time
Bus Disable Time
t
AD
t
AJ
t
OD
t
BE
t
BD
SYMBOL
Figure 5
Figure 9
Figure 9
Figure 5
Figure 4
Figure 4
5
CONDITIONS
MIN
TYP
7
2
2
10
5
5
14
MAX
UNITS
f
CLK
cycles
ns
ps
ns
ns
ns
MAX1421
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Internal reference, REFIN bypassed to AGND with a combination of 0.22µF in parallel with 1nF capacitor.
External 2.048V reference applied to REFIN.
Internal reference disabled. V
REFIN
= 0, V
REFP
= 2.162V, V
CML
= 1.65V, and V
REFN
= 1.138V.
IMD is measured with respect to either of the fundamental tones.
Specifies the common-mode range of the differential input signal supplied to the MAX1421.
V
DIFF
= V
REFP
- V
REFN
.
Input bandwidth is measured at a 3dB level.
V
REFIN
is internally biased to 2.048V through a 10kΩ resistor.
Measured as the ratio of the change in mid-scale offset voltage for a ± 5% change in V
AVDD
using the internal reference.
Typical Operating Characteristics
(V
AVDD
= V
DVDD
= 3.3V, AGND = DGND = 0, V
IN
= ±1.024V, differential input voltage, f
CLK
= 40MHz (50% duty cycle), digital output
load C
L
= 10pF, T
A
= T
MIN
to T
MAX,
unless otherwise noted. Typical values are at T
A
= +25°C.)
FFT PLOT, 4096-POINT RECORD,
DIFFERENTIAL INPUT
MAX1421 toc01
FFT PLOT, 4096-POINT RECORD,
DIFFERENTIAL INPUT
MAX1421 toc02
FFT PLOT, 4096-POINT RECORD,
DIFFERENTIAL INPUT
f
IN
= 38.54MHz
A
IN
= -0.49dB FS
MAX1421 toc03
0
-20
AMPLITUDE (dB)
-40
-60
-80
-100
-120
0
5
f
IN
= 7.54MHz
A
IN
= -0.45dB FS
0
-20
AMPLITUDE (dB)
-40
HD2
-60
-80
-100
-120
HD3
f
IN
= 19.90MHz
A
IN
= -0.50dB FS
f
IN
0
-20
AMPLITUDE (dB)
-40
HD2
-60
-80
-100
-120
HD3
HD2
HD3
10
15
20
0
5
10
15
20
0
5
10
15
20
ANALOG INPUT FREQUENCY (MHz)
ANALOG INPUT FREQUENCY (MHz)
ANALOG INPUT FREQUENCY (MHz)
_______________________________________________________________________________________
5
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