LTC1666/LTC1667/LTC1668
FEATURES
s
s
s
s
s
s
s
s
s
12-Bit, 14-Bit, 16-Bit,
50Msps DACs
DESCRIPTIO
The LTC
®
1666/LTC1667/LTC1668 are 12-/14-/16-bit,
50Msps differential current output DACs implemented on
a high performance BiCMOS process with laser trimmed,
thin-film resistors. The combination of a novel current-
steering architecture and a high performance process
produces DACs with exceptional AC and DC performance.
The LTC1668 is the first 16-bit DAC in the marketplace to
exhibit an SFDR (spurious free dynamic range) of 87dB
for an output signal frequency of 1MHz.
Operating from
±5V
supplies, the LTC1666/LTC1667/
LTC1668 can be configured to provide full-scale output
currents up to 10mA. The differential current outputs of
the DACs allow single-ended or true differential operation.
The – 1V to 1V output compliance of the LTC1666/
LTC1667/LTC1668 allows the outputs to be connected
directly to external resistors to produce a differential out-
put voltage without degrading the converter’s linearity. Al-
ternatively, the outputs can be connected to the summing
junction of a high speed operational amplifier, or to a
transformer.
The LTC1666/LTC1667/LTC1668 are pin compatible and
are available in a 28-pin SSOP and are fully specified over
the industrial temperature range.
, LTC and LT are registered trademarks of Linear Technology Corporation.
50Msps Update Rate
Pin Compatible 12-Bit, 14-Bit and 16-Bit Devices
High Spectral Purity: 87dB SFDR at 1MHz f
OUT
5pV-s Glitch Impulse
Differential Current Outputs
20ns Settling Time
Low Power: 180mW from
±5V
Supplies
TTL/CMOS (3.3V or 5V) Inputs
Small Package: 28-Pin SSOP
APPLICATIO S
s
s
s
s
s
s
s
s
Cellular Base Stations
Multicarrier Base Stations
Wireless Communication
Direct Digital Synthesis (DDS)
xDSL Modems
Arbitrary Waveform Generation
Automated Test Equipment
Instrumentation
TYPICAL APPLICATION
LTC1668, 16-Bit, 50Msps DAC
5V
0.1µF
V
DD
LTC1668
REFOUT
0.1µF
R
SET
2k
I
REFIN
2.5V
REFERENCE
52.3Ω
+
–
COMP1
C1
0.1µF
COMP2
C2
0.1µF
V
SS
AGND DGND
CLK
16-BIT
HIGH SPEED
DAC
52.3Ω
I
OUT B
V
OUT
1V
P-P
DIFFERENTIAL
SFDR (dB)
I
OUT A
+
–
LADCOM
DB15
DB0
1666/7/8 TA01
0.1µF
– 5V
CLOCK 16-BIT DATA
INPUT
INPUT
U
U
U
LTC1668 SFDR vs f
OUT
and f
CLOCK
100
5MSPS
90
25MSPS
80
50MSPS
70
60
DIGITAL AMPLITUDE = 0dBFS
0.1
1.0
f
OUT
(MHz)
1666/7/8
G05
50
10
100
1
LTC1666/LTC1667/LTC1668
ABSOLUTE
AXI U
RATI GS
Supply Voltage (V
DD
) ................................................ 6V
Negative Supply Voltage (V
SS
) ............................... – 6V
Total Supply Voltage (V
DD
to V
SS
) .......................... 12V
Digital Input Voltage .................... – 0.3V to (V
DD
+ 0.3V)
Analog Output Voltage
(I
OUT A
and I
OUT B
) ........ (V
SS
– 0.3V) to (V
DD
+ 0.3V)
PACKAGE/ORDER I FOR ATIO
DB9
DB8
DB7
DB6
DB5
DB4
DB3
DB2
DB1
1
2
3
4
5
6
7
8
9
DB0 (LSB) 10
NC 11
NC 12
NC 13
NC 14
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 110°C,
θ
JA
= 100°C/W
TOP VIEW
DB11
DB10
DB9
DB8
DB7
DB6
DB5
DB4
DB3
1
2
3
4
5
6
7
8
9
28 DB12
27 DB13 (MSB)
26 CLK
25 V
DD
24 DGND
23 V
SS
22 COMP2
21 COMP1
20 I
OUT A
19 I
OUT B
18 LADCOM
17 AGND
16 I
REFIN
15 REFOUT
ORDER PART
NUMBER
LTC1667CG
LTC1667IG
DB2 10
DB1 11
DB0 (LSB) 12
NC 13
NC 14
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 110°C,
θ
JA
= 100°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
2
U
U
W
W W
U
W
(Note 1)
Power Dissipation ............................................. 500mW
Operating Temperature Range
LTC1666C/LTC1667C/LTC1668C ........... 0°C to 70°C
LTC1666I/LTC1667I/LTC1668I .......... – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
28 DB10
27 DB11 (MSB)
26 CLK
25 V
DD
24 DGND
23 V
SS
22 COMP2
21 COMP1
20 I
OUT A
19 I
OUT B
18 LADCOM
17 AGND
16 I
REFIN
15 REFOUT
ORDER PART
NUMBER
LTC1666CG
LTC1666IG
TOP VIEW
DB13
DB12
DB11
DB10
DB9
DB8
DB7
DB6
DB5
1
2
3
4
5
6
7
8
9
28 DB14
27 DB15 (MSB)
26 CLK
25 V
DD
24 DGND
23 V
SS
22 COMP2
21 COMP1
20 I
OUT A
19 I
OUT B
18 LADCOM
17 AGND
16 I
REFIN
15 REFOUT
ORDER PART
NUMBER
LTC1668CG
LTC1668IG
DB4 10
DB3 11
DB2 12
DB1 13
DB0 (LSB) 14
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 110°C,
θ
JA
= 100°C/W
LTC1666/LTC1667/LTC1668
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
DD
= 5V, V
SS
= – 5V, LADCOM = AGND = DGND = 0V, I
OUTFS
= 10mA.
SYMBOL PARAMETER
Resolution
Monotonicity
INL
DNL
Integral Nonlinearity
Differential Nonlinearity
Offset Error
Offset Error Drift
GE
Gain Error
Internal Reference, R
IREFIN
= 2k
External Reference,
V
REF
= 2.5V, R
IREFIN
= 2k
Internal Reference
External Reference
V
DD
= 5V
±5%
V
SS
= – 5V
±5%
f
CLK
= 25Msps, f
OUT
= 1MHz
0dB FS Output
– 6dB FS Output
–12dB FS Output
f
CLK
= 50Msps, f
OUT
= 1MHz
f
CLK
= 50Msps, f
OUT
= 2.5MHz
f
CLK
= 50Msps, f
OUT
= 5MHz
f
CLK
= 50Msps, f
OUT
= 20MHz
Spurious Free Dynamic
Range Within a Window
f
CLK
= 25Msps,
f
OUT
= 1MHz, 2MHz Span
f
CLK
= 50Msps,
f
OUT
= 5MHz, 4MHz Span
THD
Total Harmonic Distortion f
CLK
= 25Msps, f
OUT
= 1MHz
f
CLK
= 50Msps, f
OUT
= 5MHz
–75
–77
85
86
86
50
30
±0.1
±0.2
(Note 2)
(Note 2)
0.1
5
2
1
50
30
±0.1
±0.2
CONDITIONS
q
ELECTRICAL CHARACTERISTICS
MIN
12
12
LTC1666
TYP MAX
MIN
14
14
LTC1667
TYP MAX
MIN
16
14
LTC1668
TYP MAX
UNITS
Bits
Bits
DC Accuracy (Measured at I
OUT A
, Driving a Virtual Ground)
±1
±1
±0.2
0.1
5
±2
±1
±0.2
2
1
50
30
±1
0.1
5
±8
±4
±0.2
2
1
LSB
LSB
% FSR
ppm/°C
% FSR
% FSR
ppm/°C
ppm/°C
Gain Error Drift
PSRR
Power Supply
Rejection Ratio
Spurious Free Dynamic
Range to Nyquist
±0.1
% FSR/V
±0.2
% FSR/V
AC Linearity
SFDR
76
78
78
87
87
83
85
81
79
70
96
88
– 84
– 78
– 77
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
3
LTC1666/LTC1667/LTC1668
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
DD
= 5V, V
SS
= – 5V, LADCOM = AGND = DGND = 0V, I
OUTFS
= 10mA.
SYMBOL
I
OUTFS
PARAMETER
Full-Scale Output Current
Output Compliance Range
Output Resistance; R
IOUT A
, R
IOUT B
Output Capacitance
Reference Output
Reference Voltage
Reference Output Drift
Reference Output Load Regulation
Reference Input
Reference Small-Signal Bandwidth
Power Supply
V
DD
V
SS
I
DD
I
SS
P
DIS
Positive Supply Voltage
Negative Supply Voltage
Positive Supply Current
Negative Supply Current
Power Dissipation
I
FS
= 10mA, f
CLK
= 25Msps, f
OUT
= 1MHz
I
FS
= 10mA, f
CLK
= 25Msps, f
OUT
= 1MHz
I
FS
= 10mA, f
CLK
= 25Msps, f
OUT
= 1MHz
I
FS
= 1mA, f
CLK
= 25Msps, f
OUT
= 1MHz
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
q
LTC1666/LTC1667/LTC1668
MIN
TYP
MAX
1
–1
0.7
1.1
5
10
1
1.5
UNITS
mA
V
kΩ
pF
Analog Output
I
FS
= 10mA
I
OUT A, B
to LADCOM
q
q
REFOUT Tied to I
REFIN
Through 2kΩ
I
LOAD
= 0mA to 5mA
2.475
2.5
25
6
2.525
V
ppm/°C
mV/mA
I
FS
= 10mA, C
COMP1
= 0.1µF
4.75
–4.75
20
5
–5
3
33
180
85
50
75
20
8
15
5
4
4
50
q
q
q
kHz
5.25
–5.25
5
40
V
V
mA
mA
mW
mW
Msps
ns
ns
pV-s
pV-s
ns
ns
pA/√Hz
V
0.8
±10
V
µA
pF
ns
ns
ns
ns
Dynamic Performance (Differential Transformer Coupled Output, 50Ω Double Terminated, Unless Otherwise Noted)
f
CLOCK
t
S
t
PD
Maximum Update Rate
Output Settling Time
Output Propagation Delay
Glitch Impulse
t
r
t
f
i
NO
Digital Inputs
V
IH
V
IL
I
IN
C
IN
t
DS
t
DH
t
CLKH
t
CLKL
Digital High Input Voltage
Digital Low Input Voltage
Digital Input Current
Digital Input Capacitance
Input Setup Time
Input Hold Time
Clock High Time
Clock Low Time
q
q
q
q
To 0.1% FSR
Single Ended
Differential
Output Rise Time
Output Fall Time
Output Noise
2.4
5
8
4
5
8
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
For the LTC1666,
±1LSB
=
±0.024%
of full scale;
for the LTC1667,
±1LSB
=
±0.006%
of full scale =
±61ppm
of full scale;
for the LTC1668,
±1LSB
=
±0.0015%
of full scale =
±15.3ppm
of full scale.
4
LTC1666/LTC1667/LTC1668
TYPICAL PERFOR A CE CHARACTERISTICS
Single Tone SFDR at 50MSPS
0
–10
SFDR = 87dB
f
CLOCK
= 50MSPS
f
OUT
= 1.002MHz
AMPL = 0dBFS
= –8.25dBm
SIGNAL AMPLITUDE (dBFS)
SIGNAL AMPLITUDE (dBFS)
SIGNAL AMPLITUDE (dBFS)
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
5
15
FREQUENCY (MHz)
10
4-Tone SFDR, f
CLOCK
= 5MSPS
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
0.1
50
0.46
0.82
1.18
1.54
FREQUENCY (MHz)
1.9
60
100
SIGNAL AMPLITUDE (dBFS)
SFDR (dB)
SFDR (dB)
SFDR > 82dB
f
CLOCK
= 5MSPS
f
OUT1
= 0.5MHz
f
OUT2
= 0.65MHz
f
OUT3
= 1.10MHz
f
OUT4
= 1.25MHz
AMPL = 0dBFS
SFDR vs f
OUT
and Digital Amplitude
(dBFS) at f
CLOCK
= 25MSPS
95
90
85
80
SFDR (dB)
SFDR (dB)
0dBFS
85
–6dBFS
–12dBFS
80
SFDR (dB)
75
70
65
60
55
50
0
2
6
f
OUT
(MHz)
4
8
10
1666/7/8 G07
U W
20
1666/7/8 G04
(LTC1668)
4-Tone SFDR, f
CLOCK
= 50MSPS
2-Tone SFDR
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
25
SFDR > 86dB
f
CLOCK
= 50MSPS
f
OUT1
= 4.9MHz
f
OUT2
= 5.09MHz
AMPL = 0dBFS
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
SFDR > 74dB
f
CLOCK
= 50MSPS
f
OUT1
= 5.02MHz
f
OUT2
= 6.51MHz
f
OUT3
= 11.02MHz
f
OUT4
= 12.51MHz
AMPL = 0dBFS
–100
4.5
5.0
FREQUENCY (MHz)
5.5
1666/7/8 G02
1
4.6
8.2
11.8
15.4
FREQUENCY (MHz)
19
1666/7/8 G01
1666/7/8 G03
SFDR vs f
OUT
and f
CLOCK
100
SFDR vs f
OUT
and Digital Amplitude
(dBFS) at f
CLOCK
= 5MSPS
95
90
0dBFS
–6dBFS
–12dBFS
5MSPS
90
25MSPS
80
50MSPS
85
80
75
70
65
60
55
70
DIGITAL AMPLITUDE = 0dBFS
0.1
1.0
f
OUT
(MHz)
1666/7/8
G05
50
0
0.4
0.8
1.2
f
OUT
(MHz)
1.6
2.0
10
100
1666/7/8 G06
SFDR vs f
OUT
and Digital Amplitude
(dBFS) at f
CLOCK
= 50MSPS
90
0dBFS
85
80
75
70
65
60
55
50
95
90
SFDR vs f
OUT
and I
OUTFS
at
f
CLOCK
= 25MSPS
DIGITAL AMPLITUDE = 0dBFS
I
OUTFS
= 10mA
75
70
65
60
55
50
0
5
10
f
OUT
(MHz)
15
20
1666/7/8 G08
–12dBFS
–6dBFS
I
OUTFS
= 5mA
I
OUTFS
= 2.5mA
0
2.5
5
f
OUT
(MHz)
7.5
10
1666/7/8 G09
5
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