LINER LTC2636

LTC2636
Octal 12-/10-/8-Bit SPI VOUT
DACs with10ppm/°C Reference
DESCRIPTION
FEATURES
n
n
n
n
n
n
n
n
n
n
n
Integrated Precision Reference
2.5V Full-Scale 10ppm/°C (LTC2636-L)
4.096V Full-Scale 10ppm/°C (LTC2636-H)
Maximum INL Error: 2.5LSB (LTC2636-12)
Low Noise: 0.75mVP-P 0.1Hz to 200KHz
Guaranteed Monotonic Over –40°C to 125°C
Temperature Range
Selectable Internal or External Reference
2.7V to 5.5V Supply Range (LTC2636-L)
Ultralow Crosstalk Between DACs (<2.4nV•s)
Low Power: 0.9mA at 3V (LTC2636-L)
Power-On-Reset to Zero-Scale/Mid-Scale
Double-Buffered Data Latches
Tiny 14-Lead 4mm × 3mm DFN and 16-Lead MSOP
Packages
APPLICATIONS
n
n
n
n
n
n
Mobile Communications
Process Control and Industrial Automation
Automatic Test Equipment
Portable Equipment
Automotive
Optical Networking
The LTC®2636 is a family of octal 12-, 10-, and 8-bit
voltage-output DACs with an integrated, high-accuracy,
low-drift 10ppm/°C reference in 14-lead DFN and 16-lead
MSOP packages. It has a rail-to-rail output buffer and is
guaranteed monotonic. The LTC2636-L has a full-scale
output of 2.5V, and operates from a single 2.7V to 5.5V
supply. The LTC2636-H has a full-scale output of 4.096V,
and operates from a 4.5V to 5.5V supply. Each DAC can
also operate with an external reference, which sets the DAC
full-scale output to the external reference voltage.
These DACs communicate via an SPI/MICROWIRE™-compatible 3-wire serial interface which operates at clock rates
up to 50MHz. Hardware clear (CLR) and asynchronous
DAC update (LDAC) pins are available in the MSOP package. The LTC2636 incorporates a power-on reset circuit.
Options are available for reset to zero-scale or reset to
mid-scale in internal reference mode, or reset to mid-scale
in external reference mode after power-up.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
SPI/MICROWIRE is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 5396245, 5859606,
6891433, 6937178, 7414561.
BLOCK DIAGRAM
SWITCH
INTERNAL REFERENCE
REF
VREF
GND
REGISTER
REGISTER
DAC A
REGISTER
DAC H
REGISTER
REGISTER
REGISTER
REGISTER
DAC B
2
DAC G
REGISTER
REGISTER
REGISTER
REGISTER
DAC C
DAC F
REGISTER
REGISTER
REGISTER
REGISTER
DAC D
0
VOUTF
–1
VREF
VREF
VOUTD
VCC = 3V
INTERNAL REF.
1
VOUTG
VREF
VREF
VOUTC
VOUTH
VREF
VREF
VOUTB
12-Bit Integral Nonlinearity
(LTC2636-LZ12)
INL (LSB)
VOUTA
REGISTER
VCC
DAC E
VOUTE
CS/LD
–2
0
1024
2048
CODE
3072
4095
2636 TA01
CONTROL LOGIC
SDI
DECODE
SCK
(LDAC)
32-BIT SHIFT REGISTER
(CLR)
POWER-ON RESET
2636 BD
( ) MSOP PACKAGE ONLY
2636f
1
LTC2636
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Supply Voltage (VCC) ................................... –0.3V to 6V
CS/LD, SCK, SDI, LDAC, CLR....................... –0.3V to 6V
VOUT A–VOUT H ..................–0.3V to Min(VCC + 0.3V, 6V)
REF ....................................–0.3V to Min(VCC + 0.3V, 6V)
Operating Temperature Range
LTC2636C ................................................ 0°C to 70°C
LTC2636I.............................................. –40°C to 85°C
LTC2636H (Note 3) ............................ –40°C to 125°C
Maximum Junction Temperature........................... 150°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MS16-Lead Package ......................................... 300°C
PIN CONFIGURATION
TOP VIEW
VCC
1
14 GND
VOUT A
2
VOUT B
3
13 VOUT H
12 VOUT G
VOUT C
4
11 VOUT F
VOUT D
5
10 VOUT E
CS/LD
6
9 REF
SCK
7
8 SDI
DE PACKAGE
14-LEAD (4mm × 3mm) PLASTIC DFN
TOP VIEW
VCC
VOUT A
VOUT B
VOUT C
VOUT D
LDAC
CS/LD
SCK
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
GND
VOUT H
VOUT G
VOUT F
VOUT E
REF
CLR
SDI
MS PACKAGE
16-LEAD (4mm × 5mm) PLASTIC MSOP
TJMAX = 150°C, θJA = 110°C/W
TJMAX = 150°C, θJA = 37°C/W
EXPOSED PAD (PIN 15) IS GND, MUST BE SOLDERED TO PCB
2636f
2
LTC2636
ORDER INFORMATION
LTC2636 C
DE
–L
Z
12
#TR
PBF
LEAD FREE DESIGNATOR
TAPE AND REEL
TR = 2500-Piece Tape and Reel
RESOLUTION
12 = 12-Bit
10 = 10-Bit
8 = 8-Bit
POWER-ON RESET
MI = Reset to Mid-Scale in Internal Reference Mode
MX = Reset to Mid-Scale in External Reference Mode
Z = Reset to Zero-Scale in Internal Reference Mode
FULL-SCALE VOLTAGE, INTERNAL REFERENCE MODE
L = 2.5V
H = 4.096V
PACKAGE TYPE
DE = 14-Lead DFN
MS = 16-Lead MSOP
TEMPERATURE GRADE
C = Commercial Temperature Range (0°C to 70°C)
I = Industrial Temperature Range (–40°C to 85°C)
H = Automotive Temperature Range (–40°C to 125°C)
PRODUCT PART NUMBER
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
2636f
3
LTC2636
PRODUCT SELECTION GUIDE
PART MARKING*
POWER-ON
RESET TO CODE
POWER-ON
REFERENCE
MODE
RESOLUTION
VCC
PART NUMBER
DFN
MSOP
VFS WITH INTERNAL
REFERENCE
MAXIMUM
INL
LTC2636-LMI12
LMI12
6LMI12
2.5V•(4095/4096)
Mid-Scale
Internal
12-Bit
2.7V-5.5V
±2.5LSB
LTC2636-LMI10
LMI10
6LMI10
2.5V•(1023/1024)
Mid-Scale
Internal
10-Bit
2.7V-5.5V
±1LSB
2.5V•(255/256)
LTC2636-LMI8
6LMI8
36LMI8
Mid-Scale
Internal
8-Bit
2.7V-5.5V
±0.5LSB
LTC2636-LMX12
LMX12
6LMX12 2.5V•(4095/4096)
Mid-Scale
External
12-Bit
2.7V-5.5V
±2.5LSB
LTC2636-LMX10
LMX10
6LMX10 2.5V•(1023/1024)
Mid-Scale
External
10-Bit
2.7V-5.5V
±1LSB
LTC2636-LMX8
6LMX8
36LMX8 2.5V•(255/256)
Mid-Scale
External
8-Bit
2.7V-5.5V
±0.5LSB
LTC2636-LZ12
6LZ12
36LZ12
2.5V•(4095/4096)
Zero-Scale
Internal
12-Bit
2.7V-5.5V
±2.5LSB
LTC2636-LZ10
6LZ10
36LZ10
2.5V•(1023/1024)
Zero-Scale
Internal
10-Bit
2.7V-5.5V
±1LSB
LTC2636-LZ8
36LZ8
636LZ8
2.5V•(255/256)
Zero-Scale
Internal
8-Bit
2.7V-5.5V
±0.5LSB
LTC2636-HMI12
HMI12
6HMI12
4.096V•(4095/4096)
Mid-Scale
Internal
12-Bit
4.5V-5.5V
±2.5LSB
LTC2636-HMI10
HMI10
6HMI10
4.096V•(1023/1024)
Mid-Scale
Internal
10-Bit
4.5V-5.5V
±1LSB
LTC2636-HMI8
6HMI8
36HMI8
4.096V•(255/256)
Mid-Scale
Internal
8-Bit
4.5V-5.5V
±0.5LSB
LTC2636-HMX12
HMX12
6HMX12 4.096V•(4095/4096)
Mid-Scale
External
12-Bit
4.5V-5.5V
±2.5LSB
LTC2636-HMX10
HMX10
6HMX10 4.096V•(1023/1024)
Mid-Scale
External
10-Bit
4.5V-5.5V
±1LSB
LTC2636-HMX8
6HMX8
36HMX8 4.096V•(255/256)
Mid-Scale
External
8-Bit
4.5V-5.5V
±0.5LSB
LTC2636-HZ12
6HZ12
36HZ12
4.096V•(4095/4096)
Zero-Scale
Internal
12-Bit
4.5V-5.5V
±2.5LSB
LTC2636-HZ10
6HZ10
36HZ10
4.096V•(1023/1024)
Zero-Scale
Internal
10-Bit
4.5V-5.5V
±1LSB
LTC2636-HZ8
36HZ8
636HZ8
4.096V•(255/256)
Zero-Scale
Internal
8-Bit
4.5V-5.5V
±0.5LSB
*Above options are available in a 14-lead DFN package (LTC2636-DE) or 16-lead MSOP package (LTC2636-MS).
2636f
4
LTC2636
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 2.7V to 5.5V, VOUT unloaded unless otherwise specified.
LTC2636-LMI12/-LMI10/-LMI8/-LMX12/-LMX10/-LMX8/-LZ12/-LZ10/-LZ8 (VFS = 2.5V)
LTC2636-8
SYMBOL PARAMETER
CONDITIONS
MIN TYP
LTC2636-10
LTC2636-12
MAX MIN TYP
MAX MIN TYP
10
12
MAX
UNITS
DC Performance
Resolution
DNL
l
8
8
Monotonicity
VCC = 3V, Internal Reference (Note 4)
l
Differential Nonlinearity
VCC = 3V, Internal Reference (Note 4)
l
10
Bits
12
±0.5
Bits
±0.5
±1
LSB
INL
Integral Nonlinearity
VCC = 3V, Internal Reference (Note 4)
l
±0.05
±0.5
±0.2
±1
±1
±2.5
LSB
ZSE
Zero-Scale Error
VCC = 3V, Internal Reference, Code = 0
l
0.5
5
0.5
5
0.5
5
mV
VOS
Offset Error
VCC = 3V, Internal Reference (Note 5)
l
±0.5
±5
±0.5
±5
±0.5
±5
mV
VOSTC
VOS Temperature
Coefficient
VCC =3V, Internal Reference
GE
Gain Error
VCC = 3V, Internal Reference
GETC
Gain Temperature
Coefficient
VCC = 3V, Internal Reference (Note 10)
C-Grade
I-Grade
H-Grade
Load Regulation
Internal Reference, Mid-Scale,
VCC = 3V±10%,
–5mA ≤ IOUT ≤ 5mA
VCC = 5V±10%, (Note 11)
–10mA ≤ IOUT ≤ 10mA
ROUT
DC Output Impedance
Internal Reference, Mid-Scale,
VCC = 3V±10%,
–5mA ≤ IOUT ≤ 5mA
VCC = 5V±10%, (Note 11)
–10mA ≤ IOUT ≤ 10mA
±10
l
±0.2
±10
±0.8
±0.2
10
10
10
±10
±0.8
μV/°C
±0.2
10
10
10
±0.8
10
10
10
%FSR
ppm/°C
ppm/°C
ppm/°C
l
0.009 0.016
0.035 0.064
0.14 0.256 LSB/mA
l
0.009 0.016
0.035 0.064
0.14 0.256 LSB/mA
l
0.09
0.156
0.09
0.156
0.09 0.156
Ω
l
0.09
0.156
0.09
0.156
0.09 0.156
Ω
SYMBOL
PARAMETER
CONDITIONS
VOUT
DAC Output Span
External Reference
Internal Reference
MIN
PSR
Power Supply Rejection
VCC = 3V±10% or 5V±10%
ISC
Short Circuit Output Current (Note 6)
Sinking
Sourcing
VFS = VCC = 5.5V
Zero-Scale; VOUT shorted to VCC
Full-Scale; VOUT shorted to GND
l
l
TYP
MAX
UNITS
0 to VREF
0 to 2.5
V
V
–80
dB
27
–28
48
–48
mA
mA
5.5
V
Power Supply
VCC
Positive Supply Voltage
For Specified Performance
l
ICC
Supply Current (Note 7)
VCC = 3V, VREF =2.5V, External Reference
VCC = 3V, Internal Reference
VCC = 5V, VREF =2.5V, External Reference
VCC = 5V, Internal Reference
l
l
l
l
0.8
0.9
0.9
1
1.1
1.3
1.3
1.5
mA
mA
mA
mA
ISD
Supply Current in Power-Down Mode
(Note 7)
VCC = 5V, C-Grade, I-Grade
VCC = 5V, H-Grade
l
l
0.5
0.5
1.8
5
μA
μA
2.7
2636f
5
LTC2636
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 2.7V to 5.5V, VOUT unloaded unless otherwise specified.
LTC2636-LMI12/-LMI10/-LMI8/-LMX12/-LMX10/-LMX8/-LZ12/-LZ10/-LZ8 (VFS = 2.5V)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VCC
V
200
kΩ
0.005
0.1
μA
1.25
1.26
V
Reference Input
VREF
Input Voltage Range
l
1
Resistance
l
120
Capacitance
IREF
Reference Current, Power-Down Mode
160
12
DAC Powered Down
l
pF
Reference Output
l
Output Voltage
1.24
Reference Temperature Coefficient
±10
ppm/°C
Output Impedance
0.5
kΩ
Capacitive Load Driving
10
μF
2.5
mA
Short Circuit Current
VCC = 5.5V; REF Shorted to GND
VIH
Digital Input High Voltage
VCC = 3.6V to 5.5V
VCC = 2.7V to 3.6V
l
l
VIL
Digital Input Low Voltage
VCC = 4.5V to 5.5V
VCC = 2.7V to 4.5V
l
l
0.8
0.6
V
V
ILK
Digital Input Leakage
VIN = GND to VCC
l
±1
μA
CIN
Digital Input Capacitance
(Note 8)
l
2.5
pF
Digital I/O
2.4
2.0
V
V
AC Performance
tS
en
Settling Time
VCC = 3V (Note 9)
±0.39% (±1LSB at 8 Bits)
±0.098% (±1LSB at 10 Bits)
±0.024% (±1LSB at 12 Bits)
3.4
4.0
4.4
μs
μs
μs
Voltage Output Slew Rate
1.0
V/μs
Capacitive Load Driving
500
pF
Glitch Impulse
At Mid-Scale Transition
2.1
nV•s
DAC-to-DAC Crosstalk
1 DAC held at FS, 1 DAC Switch 0-FS
2.1
nV•s
Multiplying Bandwidth
External Reference
320
kHz
Output Voltage Noise Density
At f = 1kHz, External Reference
At f = 10kHz, External Reference
At f = 1kHz, Internal Reference
At f = 10kHz, Internal Reference
180
160
200
180
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
Output Voltage Noise
0.1Hz to 10Hz, External Reference
0.1Hz to 10Hz, Internal Reference
0.1Hz to 200kHz, External Reference
0.1Hz to 200kHz, Internal Reference
CREF = 0.1μF
35
40
680
730
μVP-P
μVP-P
μVP-P
μVP-P
2636f
6
LTC2636
TIMING CHARACTERISTICS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VCC = 2.7V to 5.5V, VOUT unloaded unless otherwise specified.
LTC2636-LMI12/-LMI10/-LMI8/-LMX12/-LMX10/-LMX8/-LZ12/-LZ10/-LZ8 (VFS = 2.5V)
SYMBOL
PARAMETER
CONDITIONS
t1
SDI Valid to SCK Setup
l
4
ns
t2
SDI Valid to SCK Hold
l
4
ns
t3
SCK High Time
l
9
ns
t4
SCK Low Time
l
9
ns
t5
CS/LD Pulse Width
l
10
ns
t6
LSB SCK High to CS/LD High
l
7
ns
t7
CS/LD Low to SCK High
l
7
ns
t8
CLR Pulse Width
l
20
ns
t9
LDAC Pulse Width
l
15
ns
t10
CS/LD High to SCK Positive Edge
l
7
ns
SCK Frequency
t11
MIN
TYP
MAX
l
50% Duty Cycle
CS/LD High to LDAC High or Low Transition
UNITS
50
l
MHz
200
ns
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 4.5V to 5.5V, VOUT unloaded unless otherwise specified.
LTC2636-HMI12/-HMI10/-HMI8/-HMX12/-HMX10/-HMX8/-HZ12/-HZ10/-HZ8 (VFS = 4.096V)
LTC2636-8
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
LTC2636-10
MAX MIN
TYP
LTC2636-12
MAX MIN TYP
MAX
UNITS
DC Performance
l
8
10
12
Bits
Monotonicity
VCC = 5V, Internal Reference (Note 4)
l
8
10
12
Bits
DNL
Differential
Nonlinearity
VCC = 5V, Internal Reference (Note 4)
l
INL
Integral Nonlinearity
VCC = 5V, Internal Reference (Note 4)
l
Resolution
±0.5
±0.05
±0.5
±0.5
±0.2
±1
±1
±1
LSB
±2.5
LSB
ZSE
Zero-Scale Error
VCC = 5V, Internal Reference, Code = 0
l
0.5
5
0.5
5
0.5
5
mV
VOS
Offset Error
VCC = 5V, Internal Reference (Note 5)
l
±0.5
±5
±0.5
±5
±0.5
±5
mV
VOSTC
VOS Temperature
Coefficient
VCC = 5V, Internal Reference
GE
Gain Error
VCC = 5V, Internal Reference
GETC
Gain Temperature
Coefficient
VCC = 5V, Internal Reference (Note 10)
C-Grade
I-Grade
H-Grade
Load
Regulation
VCC = 5V±10%, (Note 11)
Internal Reference, Mid-Scale,
–10mA ≤ IOUT ≤ 10mA
l
0.006
0.01
0.022
0.04
0.09
DC Output
Impedance
VCC = 5V±10%, (Note 11)
Internal Reference, Mid-Scale,
–10mA ≤ IOUT ≤ 10mA
l
0.09
0.156
0.09
0.156
0.09 0.156
ROUT
±10
l
±0.2
±10
±0.8
10
10
10
±0.2
±10
±0.8
10
10
10
±0.2
μV/°C
±0.8
10
10
10
%FSR
ppm/°C
ppm/°C
ppm/°C
0.16 LSB/mA
Ω
2636f
7
LTC2636
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 4.5V to 5.5V, VOUT unloaded unless otherwise specified.
LTC2636-HMI12/-HMI10/-HMI8/-HMX12/-HMX10/-HMX8/-HZ12/-HZ10/-HZ8 (VFS = 4.096V)
SYMBOL
PARAMETER
CONDITIONS
MIN
VOUT
DAC Output Span
External Reference
Internal Reference
PSR
Power Supply Rejection
VCC = 5V±10%
ISC
Short Circuit Output Current (Note 6)
Sinking
Sourcing
VFS = VCC = 5.5V
Zero-Scale; VOUT Shorted to VCC
Full-Scale; VOUT Shorted to GND
l
l
TYP
MAX
UNITS
0 to VREF
0 to 4.096
V
V
–80
dB
27
–28
48
–48
mA
mA
Power Supply
VCC
Positive Supply Voltage
For Specified Performance
l
5.5
V
ICC
Supply Current (Note 7)
VCC = 5V, VREF = 4.096V, External Reference
VCC = 5V, Internal Reference
l
l
1.0
1.1
1.3
1.5
mA
mA
ISD
Supply Current in Power-Down Mode
(Note 7)
VCC = 5V, C-Grade, I-Grade
VCC = 5V, H-Grade
l
l
0.5
0.5
1.8
5
μA
μA
VCC
V
200
kΩ
4.5
Reference Input
VREF
Input Voltage Range
l
1
Resistance
l
120
Capacitance
IREF
Reference Current, Power-Down Mode
160
12
DAC Powered Down
l
pF
0.005
0.1
μA
2.048
2.064
V
Reference Output
l
Output Voltage
2.032
Reference Temperature Coefficient
±10
ppm/°C
Output Impedance
0.5
kΩ
Capacitive Load Driving
10
μF
4
mA
Short Circuit Current
VCC = 5.5V; REF Shorted to GND
Digital I/O
VIH
Digital Input High Voltage
l
2.4
V
VIL
Digital Input Low Voltage
l
0.8
V
ILK
Digital Input Leakage
VIN = GND to VCC
l
±1
μA
CIN
Digital Input Capacitance
(Note 8)
l
2.5
pF
AC Performance
tS
Settling Time
VCC = 5V (Note 9)
±0.39% (±1LSB at 8 Bits)
±0.098% (±1LSB at 10 Bits)
±0.024% (±1LSB at 12 Bits)
Voltage Output Slew Rate
Capacitive Load Driving
3.8
4.3
4.8
μs
μs
μs
1.0
V/μs
500
pF
Glitch Impulse
At Mid-Scale Transition
3.0
nV•s
DAC-to-DAC Crosstalk
1 DAC held at FS, 1 DAC Switch 0-FS
2.4
nV•s
Multiplying Bandwidth
External Reference
320
kHz
2636f
8
LTC2636
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 4.5V to 5.5V, VOUT unloaded unless otherwise specified.
LTC2636-HMI12/-HMI10/-HMI8/-HMX12/-HMX10/-HMX8/-HZ12/-HZ10/-HZ8 (VFS = 4.096V)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
en
Output Voltage Noise Density
At f = 1kHz, External Reference
At f = 10kHz, External Reference
At f = 1kHz, Internal Reference
At f = 10kHz, Internal Reference
180
160
250
230
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
Output Voltage Noise
0.1Hz to 10Hz, External Reference
0.1Hz to 10Hz, Internal Reference
0.1Hz to 200kHz, External Reference
0.1Hz to 200kHz, Internal Reference
CREF = 0.1μF
35
50
680
750
μVP-P
μVP-P
μVP-P
μVP-P
TIMING CHARACTERISTICS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VCC = 4.5V to 5.5V, VOUT unloaded unless otherwise specified.
LTC2636-HMI12/-HMI10/-HMI8/-HMX12/-HMX10/-HMX8/-HZ12/-HZ10/-HZ8 (VFS = 4.096V)
SYMBOL
PARAMETER
t1
SDI Valid to SCK Setup
CONDITIONS
l
MIN
4
TYP
MAX
UNITS
ns
t2
SDI Valid to SCK Hold
l
4
ns
t3
SCK High Time
l
9
ns
t4
SCK Low Time
l
9
ns
t5
CS/LD Pulse Width
l
10
ns
t6
LSB SCK High to CS/LD High
l
7
ns
t7
CS/LD Low to SCK High
l
7
ns
t8
CLR Pulse Width
l
20
ns
t9
LDAC Pulse Width
l
15
ns
t10
CS/LD High to SCK Positive Edge
l
7
ns
t11
CS/LD High to LDAC High or Low Transition
SCK Frequency
50% Duty Cycle
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All voltages are with respect to GND.
Note 3: High temperatures degrade operating lifetimes. Operating lifetime
is derated at temperatures greater than 105°C.
Note 4: Linearity and monotonicity are defined from code kL to code 2N–1,
where N is the resolution and kL is given by kL = 0.016•(2N/ VFS), rounded
to the nearest whole code. For VFS = 2.5V and N = 12, kL = 26 and linearity
is defined from code 26 to code 4,095. For VFS = 4.096V and N = 12, kL =
16 and linearity is defined from code 16 to code 4,095.
l
l
50
200
MHz
ns
Note 5: Inferred from measurement at code 16 (LTC2636-12), code 4
(LTC2636-10) or code 1 (LTC2636-8), and at full-scale.
Note 6: This IC includes current limiting that is intended to protect the
device during momentary overload conditions. Junction temperature can
exceed the rated maximum during current limiting. Continuous operation
above the specified maximum operating junction temperature may impair
device reliability.
Note 7: Digital inputs at 0V or VCC.
Note 8: Guaranteed by design and not production tested.
Note 9: Internal Reference mode. DAC is stepped 1/4 scale to 3/4 scale
and 3/4 scale to 1/4 scale. Load is 2kΩ in parallel with 100pF to GND.
Note 10: Temperature coefficient is calculated by dividing the maximum
change in output voltage by the specified temperature range.
Note 11: Thermal resistance of MSOP package limits IOUT to
–5mA ≤ IOUT ≤ 5mA for H-grade MSOP parts and VCC = 5V ±10%.
2636f
9
LTC2636
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted. LTC2636-L12 (Internal Reference, VFS = 2.5V)
Integral Nonlinearity (INL)
Differential Nonlinearity (DNL)
1.0
1.0
VCC = 3V
VCC = 3V
0.5
DNL (LSB)
INL (LSB)
0.5
0
–0.5
–1.0
0
–0.5
0
1024
2048
CODE
3072
–1.0
4095
0
1024
2048
CODE
3072
2636 G01
INL vs Temperature
Reference Output Voltage
vs Temperature
1.0
VCC = 3V
INL (POS)
VCC = 3V
0.5
INL (NEG)
–0.5
1.255
DNL (POS)
VREF (V)
0
–1.0
–50 –25
1.260
VCC = 3V
DNL (LSB)
0.5
INL (LSB)
2636 G02
DNL vs Temperature
1.0
0
25 50 75 100 125 150
TEMPERATURE (°C)
1.250
DNL (NEG)
–0.5
0
4095
1.245
–1.0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
2636 G03
1.240
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
2636 G04
Settling to ±1LSB Rising
2636 G05
Settling to ±1LSB Falling
CS/LD
5V/DIV
3/4 SCALE TO
1/4 SCALE STEP
VCC = 3V, VFS = 2.5V
RL = 2k, CL = 100pF
AVERAGE OF 256 EVENTS
VOUT
1LSB/DIV
3.6μs
4.4μs
VOUT
1LSB/DIV
1/4 SCALE TO
3/4 SCALE STEP
VCC = 3V, VFS = 2.5V
RL = 2k, CL = 100pF
AVERAGE OF 256 EVENTS
CS/LD
5V/DIV
2μs/DIV
2μs/DIV
2636 G06
2636 G07
2636f
10
LTC2636
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted. LTC2636-H12 (Internal Reference, VFS = 4.096V)
Integral Nonlinearity (INL)
Differential Nonlinearity (DNL)
1.0
1.0
VCC = 5V
VCC = 5V
0.5
DNL (LSB)
INL (LSB)
0.5
0
–0.5
–1.0
0
–0.5
0
1024
2048
CODE
3072
–1.0
4095
1024
0
2048
CODE
3072
2636 G08
INL vs Temperature
Reference Output Voltage
vs Temperature
2.068
1.0
VCC = 5V
INL (POS)
2.058
INL (NEG)
–0.5
DNL (POS)
VREF (V)
DNL (LSB)
0.5
0
–1.0
–50 –25
VCC = 5V
VCC = 5V
0.5
INL (LSB)
2636 G09
DNL vs Temperature
1.0
0
25 50 75 100 125 150
TEMPERATURE (°C)
2.048
DNL (NEG)
2.038
–0.5
0
4095
–1.0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
2636 G10
2.028
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
2636 G12
2636 G11
Settling to ±1LSB Rising
Settling to ±1LSB Falling
CS/LD
5V/DIV
1/4 SCALE TO
3/4 SCALE STEP
VCC = 5V, VFS = 4.095V
RL = 2k, CL = 100pF
AVERAGE OF 256 EVENTS
VOUT
1LSB/DIV
4.0μs
4.8μs
VOUT
1LSB/DIV
1/4 SCALE TO
3/4 SCALE STEP
VCC = 5V, VFS = 4.095V
RL = 2k, CL = 100pF
AVERAGE OF 256 EVENTS
2μs/DIV
CS/LD
5V/DIV
2μs/DIV
2636 G13
2636 G14
2636f
11
LTC2636
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
LTC2636-10
Integral Nonlinearity (INL)
Differential Nonlinearity (DNL)
1.0
1.0
VCC = 3V
VFS = 2.5V
INTERNAL REF.
VCC = 3V
VFS = 2.5V
INTERNAL REF.
0.5
DNL (LSB)
INL (LSB)
0.5
0
–0.5
–1.0
0
–0.5
256
0
768
512
CODE
–1.0
1023
256
0
768
512
CODE
2636 G15
1023
2636 G16
LTC2636-8
Integral Nonlinearity (INL)
Differential Nonlinearity (DNL)
0.50
0.50
VCC = 3V
VFS = 2.5V
INTERNAL REF.
VCC = 3V
VFS = 2.5V
INTERNAL REF.
0.25
DNL (LSB)
INL (LSB)
0.25
0
–0.25
–0.50
0
–0.25
64
0
192
128
CODE
–0.50
255
64
0
192
128
CODE
2636 G17
255
2636 G18
LTC2636
Load Regulation
Current Limiting
10
6
VCC = 5V (LTC2636-H)
VCC = 5V (LTC2636-L)
VCC = 3V (LTC2636-L)
0.15
2
ΔVOUT (V)
ΔVOUT (mV)
VCC = 5V (LTC2636-H)
VCC = 5V (LTC2636-L)
VCC = 3V (LTC2636-L)
2
0.10
4
0
–2
–4
0.05
0
–0.05
1
0
–1
–0.01
–6
INTERNAL REF.
CODE = MIDSCALE
–8
–10
–30
3
OFFSET ERROR (mV)
8
Offset Error vs Temperature
0.20
–20
–10
0
10
IOUT (mA)
20
30
2636 G19
–2
–0.15
–0.20
–30
INTERNAL REF.
CODE = MIDSCALE
–20
–10
0
10
IOUT (mA)
20
30
2636 G20
–3
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
2636 G21
2636f
12
LTC2636
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
LTC2636
Large-Signal Response
Mid-Scale Glitch Impulse
Power-On Reset Glitch
LTC2636-L
CS/LD
5V/DIV
VOUT
0.5V/DIV
VCC
2V/DIV
LTC2636-H12, VCC = 5V
3.0nV•s TYP
VOUT
5mV/DIV
LTC2636-L12, VCC = 3V
2.1nV•s TYP
VFS = VCC = 5V
1/4 SCALE to 3/4 SCALE
2μs/DIV
2μs/DIV
2636 G22
200μs/DIV
2636 G23
Headroom at Rails
vs Output Current
LTC2636-H
5V SOURCING
VCC = 5V
INTERNAL REF.
4.0
VOUT (V)
3.5
Power-On Reset to Mid-Scale
VCC
2V/DIV
CS/LD
2V/DIV
3V (LTC2636-L) SOURCING
3.0
2636 G24
Exiting Power-Down to Mid-Scale
5.0
4.5
ZERO-SCALE
VOUT
5mV/DIV
LTC2636-H
2.5
2.0
1.5
DACs A-G IN
VOUT POWER-DOWN MODE
0.5V/DIV
5V SINKING
VOUT
0.5V/DIV
LTC2636-L
1.0
3V (LTC2636-L) SINKING
0.5
0
0
1
2
3
4 5 6
IOUT (mA)
7
8
9
200μs/DIV
5μs/DIV
10
2636 G27
2636 G26
2636 G25
Hardware CLR
Supply Current vs Logic Voltage
1.5
SWEEP SCK, SDI, CS/LD
BETWEEN 0V AND VCC
Hardware CLR to Mid-Scale
VCC = 5V
VREF = 4.096V
CODE = FULL-SCALE
1.4
ICC (mA)
VOUT
1V/DIV
VOUT
1V/DIV
VCC = 5V
VREF = 4.096V
CODE = FULL-SCALE
1.2
VCC = 5V
1.0
VCC = 3V
(LTC2636-L)
0.8
0.6
0
1
2
3
LOGIC VOLTAGE (V)
CLR
5V/DIV
CLR
5V/DIV
4
5
1μs/DIV
1μs/DIV
2636 G29
2636 G30
2636 G28
2636f
13
LTC2636
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
LTC2636
Multiplying Bandwidth
Noise Voltage vs Frequency
2
500
0
NOISE VOLTAGE (nV/√Hz)
–2
–4
dB
–6
–8
–10
–12
VCC = 5V
VREF(DC) = 2V
VREF(AC) = 0.2VP-P
CODE = FULL-SCALE
–14
–16
–18
1k
400
VCC = 5V
CODE = MID-SCALE
INTERNAL REF.
300
LTC2636-H
200
LTC2636-L
100
10k
100k
FREQUENCY (Hz)
0
100
1M
1k
100k
10k
FREQUENCY (Hz)
2636 G31
2636 G32
0.1Hz to 10Hz Voltage Noise
Gain Error vs Reference Input
1.0
VCC = 5V, VFS = 2.5V
CODE = MIDSCALE
INTERNAL REF.
VCC = 5.5V
0.8 GAIN ERROR OF 8 CHANNELS
0.6
GAIN ERROR (%FSR)
1M
0.4
0.2
10μV/DIV
0
–0.2
–0.4
–0.6
–0.8
–1.0
1
1.5
2 2.5 3 3.5 4 4.5
REFERENCE VOLTAGE (V)
5
1s/DIV
5.5
2636 G34
2636 G33
DAC to DAC Crosstalk (Dynamic)
Gain Error vs Temperature
1.0
GAIN ERROR (%FSR)
CS/LD
5V/DIV
1 DAC
SWITCH 0-FS
2V/DIV
VOUT
1mV/DIV
0.5
0
–0.5
LTC2636-H12, VCC = 5V
2.4nV•s TYP
CREF = 0.1μF
2μs/DIV
2636 G35
–1.0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
2636 G36
2636f
14
LTC2636
PIN FUNCTIONS
(DFN/MSOP)
VCC (Pin 1/1): Supply Voltage Input. 2.7V ≤ VCC ≤ 5.5V
(LTC2636-L) or 4.5V ≤ VCC ≤ 5.5V (LTC2636-H). Bypass
to GND with a 0.1μF capacitor.
VOUT A to VOUT H (Pins 2-5, 10-13/2-5, 12-15): DAC
Analog Voltage Outputs.
CS/LD (Pin 6/7): Serial Interface Chip Select/Load Input.
When CS/LD is low, SCK is enabled for shifting data on
SDI into the register. When CS/LD is taken high, SCK
is disabled and the specified command (see Table 1) is
executed.
SCK (Pin 7/8): Serial Interface Clock Input. CMOS and
TTL compatible.
SDI (Pin 8/9): Serial Interface Data Input. Data on SDI is
clocked into the DAC on the rising edge of SCK. The LTC2636
accepts input word lengths of either 24 or 32 bits.
REF (Pin 9/11): Reference Voltage Input or Output. When
External Reference mode is selected, REF is an input
(1V ≤ VREF ≤ VCC) where the voltage supplied sets the
full-scale DAC output voltage. When Internal Reference
is selected, the 10ppm/°C 1.25V (LTC2636-L) or 2.048V
(LTC2636-H) internal reference (half full-scale) is available at REF. This output may be bypassed to GND with
up to 10μF, and must be buffered when driving external
DC load current.
GND (Pin 14/16): Ground.
LDAC (Pin 6, MSOP only): Asynchronous DAC Update
Pin. If CS/LD is high, a falling edge on LDAC immediately
updates the DAC registers with the contents of the input
registers (similar to a software update). If CS/LD is low
when LDAC goes low, the DAC registers are updated after
CS/LD returns high. A low on the LDAC pin powers up
the DACs. A software power down command is ignored if
LDAC is low. If the LDAC functionality is not being used,
the LDAC pin should be tied high.
CLR (Pin 10, MSOP only): Asynchronous Clear Input.
A logic low at this level-triggered input clears all registers and causes the DAC voltage output to reset to Zero
(LTC2636-Z) or Mid-scale (LTC2636-MI/-MX). CMOS and
TTL compatible.
Exposed Pad (Pin 15, DFN Only): Ground. Must be soldered to PCB Ground.
2636f
15
LTC2636
BLOCK DIAGRAM
SWITCH
INTERNAL REFERENCE
REF
VREF
GND
REGISTER
REGISTER
DAC A
REGISTER
VOUTA
REGISTER
VCC
DAC H
VREF
REGISTER
REGISTER
DAC B
REGISTER
REGISTER
VREF
VOUTB
DAC G
REGISTER
REGISTER
REGISTER
REGISTER
DAC C
DAC F
VOUTF
VREF
REGISTER
REGISTER
DAC D
REGISTER
REGISTER
VREF
VOUTD
VOUTG
VREF
VREF
VOUTC
VOUTH
DAC E
VOUTE
CS/LD
CONTROL LOGIC
SDI
DECODE
SCK
(LDAC)
32-BIT SHIFT REGISTER
(CLR)
POWER-ON RESET
2636 BD
( ) MSOP PACKAGE ONLY
TIMING DIAGRAMS
t1
t2
SCK
t3
1
t6
t4
2
3
23
24
t10
SDI
t5
t7
CS/LD
t11
t9
LDAC
2636 F01a
Figure 1a
CS/LD
t11
LDAC
2636 F01b
Figure 1b
2636f
16
LTC2636
OPERATION
The LTC2636 is a family of octal voltage output DACs
in 14-lead DFN and 16-lead MSOP packages. Each DAC
can operate rail-to-rail using an external reference, or
with its full-scale voltage set by an integrated reference.
Eighteen combinations of accuracy (12-, 10-, and 8-bit),
power-on reset value (zero-scale, mid-scale in internal
reference mode, or mid-scale in external reference mode),
and full-scale voltage (2.5V or 4.096V) are available. The
LTC2636 is controlled using a 3-wire SPI/MICROWIRE
compatible interface.
Power-On Reset
The LTC2636-HZ/-LZ clear the output to zero-scale when
power is first applied, making system initialization consistent and repeatable.
For some applications, downstream circuits are active
during DAC power-up, and may be sensitive to nonzero
outputs from the DAC during this time. The LTC2636
contains circuitry to reduce the power-on glitch: the
analog output typically rises less than 5mV above zeroscale during power on. In general, the glitch amplitude
decreases as the power supply ramp time is increased.
See “Power-On Reset Glitch” in the Typical Performance
Characteristics section.
The LTC2636-HMI/-HMX/-LMI/-LMX provide an alternative reset, setting the output to mid-scale when power is
first applied. The LTC2636-LMI and LTC2636-HMI power
up in internal reference mode, with the output set to a
mid-scale voltage of 1.25V and 2.048V respectively. The
LTC2636-LMX and LTC2636-HMX power-up in external
reference mode, with the output set to mid-scale of the
external reference. Default reference mode selection is
described in the Reference Modes section.
Power Supply Sequencing
The voltage at REF (Pin 9-DFN, Pin 11-MSOP) must be
kept within the range –0.3V ≤ VREF ≤ VCC + 0.3V (see
Absolute Maximum Ratings). Particular care should be
taken to observe these limits during power supply turnon and turn-off sequences, when the voltage at VCC is in
transition.
Transfer Function
The digital-to-analog transfer function is
⎛ k⎞
VOUT(IDEAL) = ⎜ n ⎟ VREF
⎝2 ⎠
where k is the decimal equivalent of the binary DAC input
code, n is the resolution, and VREF is either 2.5V (LTC2636LMI/-LMX/-LZ) or 4.096V (LTC2636-HMI/-HMX/-HZ) when
in Internal Reference mode, and the voltage at REF when
in External Reference mode.
Table 1. Command Codes
COMMAND*
C3
C2
C1
C0
0
0
0
0
Write to Input Register n
0
0
0
1
Update (Power-Up) DAC Register n
0
0
1
0
Write to Input Register n, Update (Power-Up) All
0
0
1
1
Write to and Update (Power-Up) DAC Register n
0
1
0
0
Power-Down DAC n
0
1
0
1
Power-Down Chip (All DAC’s and Reference)
0
1
1
0
Select Internal Reference (Power-Up Reference)
0
1
1
1
Select External Reference (Power-Down Internal
Reference)
1
1
1
1
No Operation
*Command codes not shown are reserved and should not be used.
Table 2. Address Codes
ADDRESS (n)*
A3
A2
A1
A0
0
0
0
0
DAC A
0
0
0
1
DAC B
0
0
1
0
DAC C
0
0
1
1
DAC D
0
1
0
0
DAC E
0
1
0
1
DAC F
0
1
1
0
DAC G
0
1
1
1
DAC H
1
1
1
1
All DACs
* Address codes not shown are reserved and should not be used.
2636f
17
LTC2636
OPERATION
INPUT WORD (LTC2636-12)
COMMAND
C3
C2
C1
ADDRESS
C0
A3
A2
A1
DATA (12 BITS + 4 DON'T-CARE BITS)
A0
D11 D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
MSB
D0
X
X
X
X
X
X
X
X
X
X
X
X
X
LSB
INPUT WORD (LTC2636-10)
COMMAND
C3
C2
C1
ADDRESS
C0
A3
A2
A1
DATA (10 BITS + 6 DON'T-CARE BITS)
A0
D9
D8
D7
D6
D5
D4
D3
D2
D1
MSB
D0
X
LSB
INPUT WORD (LTC2636-8)
COMMAND
C3
C2
C1
ADDRESS
C0
A3
A2
A1
DATA (8 BITS + 8 DON'T-CARE BITS)
A0
D7
D6
D5
MSB
D4
D3
D2
D1
D0
X
LSB
X
X
X
2636 F02
Figure 2. Command and Data Input Format
Serial Interface
The CS/LD input is level triggered. When this input is taken
low, it acts as a chip-select signal, enabling the SDI and
SCK buffers and the input shift register. Data (SDI input)
is transferred into the LTC2636 on the next 24 rising SCK
edges. The 4-bit command, C3-C0, is loaded first; then
the 4-bit DAC address, A3-A0; and finally the 16-bit data
word. The data word comprises the 12-, 10- or 8-bit
input code, ordered MSB-to-LSB, followed by 4, 6 or
8 don’t-care bits (LTC2636-12, -10 and -8 respectively;
see Figure 2). Data can only be transferred to the device
when the CS/LD signal is low, beginning on the first rising
edge of SCK. SCK may be high or low at the falling edge
of CS/LD. The rising edge of CS/LD ends the data transfer
and causes the device to execute the command specified
in the 24-bit input sequence. The complete sequence is
shown in Figure 3a.
The command (C3-C0) and address (A3-A0) assignments
are shown in Tables 1 and 2. The first four commands in
Table 1 consist of write and update operations. A Write
operation loads a 16-bit data word from the 24-bit shift
register into the input register of the selected DAC, n. An
Update operation copies the data word from the input
register to the DAC register. Once copied into the DAC
register, the data word becomes the active 12-, 10-, or
8-bit input code, and is converted to an analog voltage at
the DAC output. Write to and Update combines the first
two commands. The Update operation also powers up the
DAC if it had been in power-down mode. The data path
and registers are shown in the Block Diagram.
While the minimum input sequence is 24 bits, it may
optionally be extended to 32 bits to accommodate microprocessors that have a minimum word width of 16 bits
(2 bytes). To use the 32-bit width, 8 don’t-care bits
must be transferred to the device first, followed by the
24-bit sequence described. Figure 3b shows the 32-bit
sequence.
The 16-bit data word is ignored for all commands that do
not include a Write operation.
Reference Modes
For applications where an accurate external reference is
either not available, or not desirable due to limited space,
the LTC2636 has a user-selectable, integrated reference.
The integrated reference voltage is internally amplified
by 2x to provide the full-scale DAC output voltage range.
The LTC2636-LMI/-LMX/-LZ provides a full-scale DAC
output of 2.5V. The LTC2636-HMI/-HMX/-HZ provides a
full-scale DAC output of 4.096V. The internal reference
can be useful in applications where the supply voltage is
poorly regulated. Internal Reference mode can be selected
by using command 0110b, and is the power-on default for
LTC2636-HZ/-LZ, as well as for LTC2636-HMI/-LMI.
The 10ppm/°C, 1.25V (LTC2636-LMI/-LMX/-LZ) or 2.048V
(LTC2636-HMI/-HMX/-HZ) internal reference is available
2636f
18
SDI
SCK
CS/LD
X
1
X
2
X
X
4
X
5
X
8 DON’T-CARE BITS
3
6
C3
SDI
C2
2
C1
3
X
7
X
8
4
7
A1
ADDRESS
A2
6
A0
8
D11
9
D10
10
D9
D8
12
D7
13
D6
14
24-BIT INPUT WORD
11
D5
15
D3
17
DATA WORD
D4
16
D2
18
D1
19
C2
10
C1
11
A1
15
ADDRESS
A2
14
A0
16
32-BIT INPUT WORD
A3
13
D11
17
D10
18
D9
19
D8
20
D7
21
D6
22
D5
23
D3
25
D0
20
DATA WORD
D4
24
Figure 3b. LTC2636-12 32-Bit Load Sequence.
LTC2636-10 SDI Data Word: 10-Bit Input Code + 6 Don’t-Care Bits;
LTC2636-8 SDI Data Word: 8-Bit Input Code + 8 Don’t-Care Bits
C0
12
Figure 3a. LTC2636-12 24-Bit Load Sequence (Minimum Input Word).
LTC2636-10 SDI Data Word: 10-Bit Input Code + 6 Don’t-Care Bits;
LTC2636-8 SDI Data Word: 8-Bit Input Code + 8 Don’t-Care Bits
A3
5
COMMAND WORD
9
C0
C3
COMMAND WORD
1
SCK
CS/LD
D2
26
X
21
D1
27
X
22
D0
28
X
23
X
29
X
24
X
30
31
X
2636 F03a
X
32
2636 F03b
LTC2636
OPERATION
2636f
19
LTC2636
OPERATION
at the REF pin. Adding bypass capacitance to the REF pin
will improve noise performance; and up to 10μF can be
driven without oscillation. The REF output must be buffered
when driving an external DC load current.
Alternatively, the DAC can operate in External Reference
mode using command 0111b. In this mode, an input voltage
supplied externally to the REF pin provides the reference
(1V ≤ VREF ≤ VCC) and the supply current is reduced. The
external reference voltage supplied sets the full-scale DAC
output voltage. External Reference mode is the power-on
default for LTC2636-HMX/-LMX.
The reference mode of LTC2636-HZ/-LZ/-HMI/-LMI
(Internal Reference power-on default), can be changed
by software command after power-up. The same is true
for LTC2636-HMX/-LMX (External Reference power-on
default).
Power-Down Mode
For power-constrained applications, power-down mode can
be used to reduce the supply current whenever less than
eight DAC outputs are needed. When in power-down, the
buffer amplifiers, bias circuits, and integrated reference
circuits are disabled, and draw essentially zero current. The
DAC outputs are put into a high-impedance state, and the
output pins are passively pulled to ground through individual 200kΩ resistors. Input- and DAC-register contents
are not disturbed during power-down.
Any DAC channel or combination of channels can be put
into power-down mode by using command 0100b in
combination with the appropriate DAC address, (n). The
supply current is reduced approximately 10% for each DAC
powered down. The integrated reference is automatically
powered down when external reference is selected using
command 0111b. In addition, all the DAC channels and
the integrated reference together can be put into powerdown mode using Power Down Chip command 0101b.
When the integrated reference and all DAC channels are
in power-down mode, the REF pin becomes high impedance (typically > 1GΩ). For all power-down commands
the 16-bit data word is ignored.
Normal operation resumes after executing any command
that includes a DAC update, (as shown in Table 1) or using
the asynchronous LDAC pin. The selected DAC is powered
20
up as its voltage output is updated. When a DAC which
is in a powered-down state is powered up and updated,
normal settling is delayed. If less than eight DACs are in
a powered-down state prior to the update command, the
power-up delay time is 10μs. However, if all eight DACs
and the integrated reference are powered down, then the
main bias generation circuit block has been automatically
shut down in addition to the DAC amplifiers and reference
buffers. In this case, the power up delay time is 12μs.
The power-up of the integrated reference depends on
the command that powered it down. If the reference is
powered down using the Select External Reference Command (0111b), then it can only be powered back up using
Select Internal Reference Command (0110b). However, if
the reference was powered down using Power Down Chip
Command (0101b), then in addition to Select Internal
Reference Command (0110b), any command (in software
or using the LDAC pin) that powers up the DACs will also
power up the integrated reference.
Voltage Outputs
The LTC2636’s integrated rail-to-rail amplifiers have guaranteed load regulation when sourcing or sinking up to
10mA at 5V, and 5mA at 3V.
Load regulation is a measure of the amplifier’s ability to
maintain the rated voltage accuracy over a wide range of
load current. The measured change in output voltage per
change in forced load current is expressed in LSB/mA.
DC output impedance is equivalent to load regulation, and
may be derived from it by simply calculating a change in
units from LSB/mA to ohms. The amplifier’s DC output
impedance is 0.1Ω when driving a load well away from
the rails.
When drawing a load current from either rail, the output
voltage headroom with respect to that rail is limited by
the 50Ω typical channel resistance of the output devices
(e.g., when sinking 1mA, the minimum output voltage is
50Ω • 1mA, or 50mV). See the graph “Headroom at Rails
vs. Output Current” in the Typical Performance Characteristics section.
The amplifier is stable driving capacitive loads of up to
500pF.
2636f
LTC2636
OPERATION
VREF = VCC
POSITIVE
FSE
VREF = VCC
OUTPUT
VOLTAGE
OUTPUT
VOLTAGE
INPUT CODE
(c)
OUTPUT
VOLTAGE
2636 F04
0V
0
2,048
INPUT CODE
(a)
0V
NEGATIVE
OFFSET
4,095
INPUT CODE
(b)
Figure 4. Effects of Rail-to-Rail Operation On a DAC Transfer Curve (Shown for 12 Bits).
(a) Overall Transfer Function
(b) Effect of Negative Offset for Codes Near Zero
(c) Effect of Positive Full-Scale Error for Codes Near Full-Scale
Rail-to-Rail Output Considerations
In any rail-to-rail voltage output device, the output is limited to voltages within the supply range.
Since the analog output of the DAC cannot go below ground,
it may limit for the lowest codes as shown in Figure 4b.
Similarly, limiting can occur near full-scale when the REF
pin is tied to VCC. If VREF = VCC and the DAC full-scale error
(FSE) is positive, the output for the highest codes limits
at VCC, as shown in Figure 4c. No full-scale limiting can
occur if VREF is less than VCC –FSE.
Offset and linearity are defined and tested over the region
of the DAC transfer function where no output limiting can
occur.
Board Layout
The PC board should have separate areas for the analog and
digital sections of the circuit. A single, solid ground plane
should be used, with analog and digital signals carefully
routed over separate areas of the plane. This keeps digital
signals away from sensitive analog signals and minimizes
the interaction between digital ground currents and the
analog section of the ground plane. The resistance from
the LTC2636 GND pin to the ground plane should be as
low as possible. Resistance here will add directly to the
effective DC output impedance of the device (typically
0.1Ω). Note that the LTC2636 is no more susceptible to
this effect than any other parts of this type; on the contrary, it allows layout-based performance improvements
to shine rather than limiting attainable performance with
excessive internal resistance.
Another technique for minimizing errors is to use a separate power ground return trace on another board layer.
The trace should run between the point where the power
supply is connected to the board and the DAC ground pin.
Thus the DAC ground pin becomes the common point for
analog ground, digital ground, and power ground. When
the LTC2636 is sinking large currents, this current flows
out the ground pin and directly to the power ground trace
without affecting the analog ground plane voltage.
It is sometimes necessary to interrupt the ground plane
to confine digital ground currents to the digital portion of
the plane. When doing this, make the gap in the plane only
as long as it needs to be to serve its purpose and ensure
that no traces cross over the gap.
2636f
21
LTC2636
PACKAGE DESCRIPTION
DE Package
14-Lead (4mm × 3mm) Plastic DFN
(Reference LTC DWG # 05-08-1708 Rev B)
0.70 ±0.05
3.30 ±0.05
3.60 ±0.05
2.20 ±0.05
1.70 ± 0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
3.00 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
R = 0.115
TYP
4.00 ±0.10
(2 SIDES)
R = 0.05
TYP
3.00 ±0.10
(2 SIDES)
8
0.40 ± 0.10
14
3.30 ±0.10
1.70 ± 0.10
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER
PIN 1
TOP MARK
(SEE NOTE 6)
(DE14) DFN 0806 REV B
7
0.200 REF
1
0.25 ± 0.05
0.50 BSC
0.75 ±0.05
3.00 REF
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WGED-3) IN JEDEC
PACKAGE OUTLINE MO-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
2636f
22
LTC2636
PACKAGE DESCRIPTION
MS Package
16-Lead (4mm × 5mm) Plastic MSOP
(Reference LTC DWG # 05-08-1669 Rev Ø)
0.889 ± 0.127
(.035 ± .005)
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
4.039 ± 0.102
(.159 ± .004)
(NOTE 3)
0.50
(.0197)
BSC
0.305 ± 0.038
(.0120 ± .0015)
TYP
0.280 ± 0.076
(.011 ± .003)
REF
16151413121110 9
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
DETAIL “A”
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
4.90 ± 0.152
(.193 ± .006)
0° – 6° TYP
GAUGE PLANE
0.53 ± 0.152
(.021 ± .006)
DETAIL “A”
0.18
(.007)
SEATING
PLANE
1234567 8
1.10
(.043)
MAX
0.17 – 0.27
(.007 – .011)
TYP
0.50
(.0197)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.86
(.034)
REF
0.1016 ± 0.0508
(.004 ± .002)
MSOP (MS16) 1107 REV Ø
2636f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTC2636
TYPICAL APPLICATION
LTC2636 DACs Adjust LTC2755-16 Offsets, Amplified with LT1991 PGA to ±5V
5V
15
15V
0.1μF
VDD
LTC2755-16
0.1μF
8
7
+
IOUT1A 59
5
–
5V
2
0.1μF
–
DAC A
IOUT2A 2
6
0.1μF
1/2 LT1469
3
+
OUTA
4
9
0.1μF
VCC
REF
0.1μF
–15V
–15V
+
–
OUTD
0.1μF
15V
1
1k
RVOSA 58
62 REFA
2k
8
63 RCOM1
1/2 LT1469
4
15V
RFBA 60
61 ROFSA
64 RIN1
2
1
0.1μF
LTC2636DE-LMI12
DAC A
DAC H
DAC B
DAC G
13
DAC D
3
30k
8 M9
9 M3
10 M1
1 P1
2 P3
3 P9
0.1μF
7
VCC
LT1991
12
30k
OUT
6
VOUT = ±5V
REF
VEE
5
4
0.1μF
–15V
–15V
+
–
–15V
OUTC
–
+
DAC C
DAC B
30k
OUTB
4
GND
DAC F
DAC D
DAC E
11
–15V
5
30k
DAC C
19
SERIAL
BUS
–15V
6
CS/LD
7
SCK
8
SDI
10
GND
14
2636 TA02
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1660/LTC1665
Octal 10/8-Bit VOUT DACs in 16-Pin Narrow SSOP
VCC = 2.7V to 5.5V, Micropower, Rail-to-Rail Output
LTC1664
Quad 10-Bit VOUT DAC in 16-Pin Narrow SSOP
VCC = 2.7V to 5.5V, Micropower, Rail-to-Rail Output
LTC2600/LTC2610/
LTC2620
Octal 16-/14-/12-Bit VOUT DACs in 16-Lead Narrow SSOP
250μA per DAC, 2.5V to 5.5V Supply Range, Rail-to-Rail Output,
SPI Serial Interface
LTC2601/LTC2611/
LTC2621
Single 16-/14-/12-Bit VOUT DACs in 10-Lead DFN
300μA per DAC, 2.5V to 5.5V Supply Range, Rail-to-Rail Output,
SPI Serial Interface
LTC2602/LTC2612/
LTC2622
Dual 16-/14-/12-Bit VOUT DACs in 8-Lead MSOP
300μA per DAC, 2.5V to 5.5V Supply Range, Rail-to-Rail Output,
SPI Serial Interface
LTC2604/LTC2614/
LTC2624
Quad 16-/14-/12-Bit VOUT DACs in 16-Lead SSOP
250μA per DAC, 2.5V to 5.5V Supply Range, Rail-to-Rail Output,
SPI Serial Interface
LTC2605/LTC2615/
LTC2625
Octal 16-/14-/12-Bit VOUT DACs with I2C Interface
250μA per DAC, 2.7V to 5.5V Supply Range, Rail-to-Rail Output,
I2C Interface
LTC2606/LTC2616/
LTC2626
Single 16-/14-/12-Bit VOUT DACs with I2C Interface
270μA per DAC, 2.7V to 5.5V Supply Range, Rail-to-Rail Output,
I2C Interface
LTC2609/LTC2619/
LTC2629
Quad 16-/14-/12-Bit VOUT DACs with I2C Interface
250μA per DAC, 2.7V to 5.5V Supply Range, Rail-to-Rail Output
with Separate VREF Pins for Each DAC
LTC2630
Single 12-/10-/8-Bit VOUT DACs with 10ppm/°C
Reference in SC70
180μA per DAC, 2.7V to 5.5V Supply Range, 10ppm/°C Reference,
Rail-to-Rail Output, SPI Interface
LTC2631
Single 12-/10-/8-Bit I2C VOUT DACs with 10ppm/°C
Reference in ThinSOT
180μA per DAC, 2.7V to 5.5V Supply Range, 10ppm/°C Reference,
Selectable External Ref. Mode, Rail-to-Rail Output, I2C Interface
LTC2640
Single 12-/10-/8-Bit VOUT DACs with 10ppm/°C
Reference in ThinSOT
180μA per DAC, 2.7V to 5.5V Supply Range, 10ppm/°C Reference,
Selectable External Ref. Mode, Rail-to-Rail Output, SPI Interface
2636f
24 Linear Technology Corporation
LT 1108 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2008