LTC2634
1
2634fc
Block Diagram
Features
applications
Description
Quad 12-/10-/8-Bit
Rail-to-Rail DACs with
10ppm/°C Reference
The LTC
®
2634 is a family of quad 12-, 10- and 8-bit volt-
age output DACs with an integrated, high accuracy, low
drift 10ppm/°C reference in 16-lead QFN and 10-lead
MSOP packages. It has rail-to-rail output buffers and is
guaranteed monotonic. The LTC2634-L has a full-scale
output of 2.5V, and operates from a single 2.7V to 5.5V
supply. The LTC2634-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
full-scale output to the external reference voltage.
These DACs communicate via an SPI/MICROWIRE compat-
ible 3-wire serial interface which operates at clock rates
up to 50MHz. Serial data output (SDO), a hardware clear
(CLR), and an asynchronous DAC update (LDAC) capability
are available in the QFN package. The LTC2634 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.
Integral Nonlinearity
(LTC2634-LZ12)
n Integrated Precision Reference
2.5V Full-Scale 10ppm/°C (LTC2634-L)
4.096V Full-Scale 10ppm/°C (LTC2634-H)
n Maximum INL Error: ±2.5 LSB (LTC2634-12)
n Low Noise: 0.75mVP-P 0.1Hz to 200KHz
n Guaranteed Monotonic over –40°C to 125°C
Temperature Range
n Selectable Internal or External Reference
n 2.7V to 5.5V Supply Range (LTC2634-L)
n Ultralow Crosstalk Between DACs (2.4nV•s)
n Low Power: 0.6mA at 3V
n Power-On Reset to Zero-Scale/Mid-Scale
n Double Buffered Data Latches
n Tiny 16-Lead 3mm × 3mm QFN and 10-Lead
MSOP Packages
n Mobile Communications
n Process Control and Industrial Automation
n Automatic Test Equipment
n Portable Equipment
n Automotive
REGISTER
REGISTER
REGISTER
REGISTER
DAC A
VOUTA
(REFLO)
CS/LD
SCK
( ) QFN PACKAGE ONLY
(LDAC)
GND
VOUTB
VREF
DAC D
REGISTER
REGISTER
REGISTER
REGISTER
DAC B DAC C
VREF
VOUTD
REF
VCC
VREF
VOUTC
SWITCH
INTERNAL
REFERENCE
32-BIT SHIFT REGISTER
DECODE
CONTROL
LOGIC
POWER-ON
RESET
SDI
2634 BD
(SDO)
(CLR)
CODE
0
INL (LSB)
0
1
4095
2634 TA01
–1
–2 1024 2048 3072
2VCC = 3V
INTERNAL REF
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT 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.
LTC2634
2
2634fc
pin conFiguration
aBsolute maximum ratings
Supply Voltage (VCC) ................................... –0.3V to 6V
CS/LD, SCK, SDI, LDAC, CLR, SDO, REFLO.. –0.3V to 6V
VOUTA-VOUTD .................... –0.3V to Min (VCC + 0.3V, 6V)
REF .................................. –0.3V to Min (VCC + 0.3V, 6V)
Operating Temperature Range
LTC2634C ................................................ 0°C to 70°C
LTC2634I.............................................. –40°C to 85°C
LTC2634H (Note 3) ............................ –40°C to 125°C
(Notes 1, 2)
16 15 14 13
5678
TOP VIEW
17
UD PACKAGE
16-LEAD (3mm s 3mm) PLASTIC QFN
9
10
11
12
4
3
2
1VOUTA
VOUTB
LDAC
CS/LD
VOUTD
VOUTC
REF
CLR
VCC
DNC
GND
REFLO
SCK
DNC
SDO
SDI
TJMAX = 125°C, θJA = 68°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
1
2
3
4
5
VCC
VOUTA
VOUTB
CS/LD
SCK
10
9
8
7
6
GND
VOUTD
VOUTC
REF
SDI
TOP VIEW
11
MSE PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 35°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
Maximum Junction Temperature........................... 150°C
Storage Temperature Range ................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSOP ............................................................... 300°C
LTC2634
3
2634fc
orDer inFormation
LTC2634 C UD -L Z 12 #TR PBF
LEAD FREE DESIGNATOR
PBF = Lead Free
TAPE AND REEL
TR = 2,500-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
UD = 16-Lead QFN
MSE = 10-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/
LTC2634
4
2634fc
proDuct selection guiDe
PART NUMBER
PART MARKING* VFS WITH INTERNAL
REFERENCE
POWER-ON
RESET TO CODE
POWER-ON
REFERENCE
MODE RESOLUTION VCC MAXIMUM INLQFN MSOP
LTC2634-LMI12
LTC2634-LMI10
LTC2634-LMI8
LDQX
LDRF
LDRN
LTDRV
LTDSC
LTDSK
2.5V • (4095/4096)
2.5V • (1023/1024)
2.5V • (255/256)
Mid-Scale
Mid-Scale
Mid-Scale
Internal
Internal
Internal
12-Bit
10-Bit
8-Bit
2.7V to 5.5V
2.7V to 5.5V
2.7V to 5.5V
±2.5LSB
±1LSB
±0.5LSB
LTC2634-LMX12
LTC2634-LMX10
LTC2634-LMX8
LDQW
LDRD
LDRM
LTDRT
LTDSB
LTDSJ
2.5V • (4095/4096)
2.5V • (1023/1024)
2.5V • (255/256)
Mid-Scale
Mid-Scale
Mid-Scale
External
External
External
12-Bit
10-Bit
8-Bit
2.7V to 5.5V
2.7V to 5.5V
2.7V to 5.5V
±2.5LSB
±1LSB
±0.5LSB
LTC2634-LZ12
LTC2634-LZ10
LTC2634-LZ8
LDQV
LDRC
LDRK
LTDRS
LTDRZ
LTDSH
2.5V • (4095/4096)
2.5V • (1023/1024)
2.5V • (255/256)
Zero-Scale
Zero-Scale
Zero-Scale
Internal
Internal
Internal
12-Bit
10-Bit
8-Bit
2.7V to 5.5V
2.7V to 5.5V
2.7V to 5.5V
±2.5LSB
±1LSB
±0.5LSB
LTC2634-HMI12
LTC2634-HMI10
LTC2634-HMI8
LDRB
LDRJ
LDRR
LTDRY
LTDSG
LTDSP
4.096V • (4095/4096)
4.096V • (1023/1024)
4.096V • (255/256)
Mid-Scale
Mid-Scale
Mid-Scale
Internal
Internal
Internal
12-Bit
10-Bit
8-Bit
4.5V to 5.5V
4.5V to 5.5V
4.5V to 5.5V
±2.5LSB
±1LSB
±0.5LSB
LTC2634-HMX12
LTC2634-HMX10
LTC2634-HMX8
LDQZ
LDRH
LDRQ
LTDRX
LTDSF
LTDSN
4.096V • (4095/4096)
4.096V • (1023/1024)
4.096V • (255/256)
Mid-Scale
Mid-Scale
Mid-Scale
External
External
External
12-Bit
10-Bit
8-Bit
4.5V to 5.5V
4.5V to 5.5V
4.5V to 5.5V
±2.5LSB
±1LSB
±0.5LSB
LTC2634-HZ12
LTC2634-HZ10
LTC2634-HZ8
LDQY
LDRG
LDRP
LTDRW
LTDSD
LTDSM
4.096V • (4095/4096)
4.096V • (1023/1024)
4.096V • (255/256)
Zero-Scale
Zero-Scale
Zero-Scale
Internal
Internal
Internal
12-Bit
10-Bit
8-Bit
4.5V to 5.5V
4.5V to 5.5V
4.5V to 5.5V
±2.5LSB
±1LSB
±0.5LSB
*Above options are available in a 16-lead QFN package (LTC2634-UD) or 10-lead MSOP package (LTC2634-MSE).
LTC2634
5
2634fc
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.
LTC2634-LMI12/-LMI10/-LMI8/-LMX12/-LMX10/-LMX8/-LZ12/-LZ10/-LZ8 (VFS = 2.5V)
LTC2634-8 LTC2634-10 LTC2634-12
SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX MIN TYP MAX UNITS
DC Performance
Resolution l8 10 12 Bits
Monotonicity VCC = 3V, Internal Ref. (Note 4) l8 10 12 Bits
DNL Differential Nonlinearity VCC = 3V, Internal Ref. (Note 4) l±0.5 ±0.5 ±1 LSB
INL Integral Nonlinearity VCC = 3V, Internal Ref. (Note 4) l±0.05 ±0.5 ±0.2 ±1 ±1 ±2.5 LSB
ZSE Zero-Scale Error VCC = 3V, Internal Ref., Code = 0 l0.5 5 0.5 5 0.5 5 mV
VOS Offset Error VCC = 3V, Internal Ref. (Note 5) l±0.5 ±5 ±0.5 ±5 ±0.5 ±5 mV
VOSTC VOS Temperature
Coefficient
VCC = 3V, Internal Ref. ±10 ±10 ±10 µV/°C
GE Gain Error VCC = 3V, Internal Ref. l±0.2 ±0.8 ±0.2 ±0.8 ±0.2 ±0.8 %FSR
GETC Gain Temperature
Coefficient
VCC = 3V, Internal Ref. (Note 10)
C-Grade
I-Grade
H-Grade
10
10
10
10
10
10
10
10
10
ppm/°C
ppm/°C
ppm/°C
Load Regulation Internal Ref., Mid-Scale
VCC = 3V ±10%, –5mA ≤ IOUT ≤ 5mA
l
0.009
0.016
0.035
0.064
0.14
0.256
LSB/mA
Internal Ref., Mid-Scale
VCC = 5V ±10%, –10mA ≤ IOUT ≤ 10mA
l
0.009
0.016
0.035
0.064
0.14
0.256
LSB/mA
ROUT DC Output Impedance Internal Ref., Mid-Scale
VCC = 3V ±10%, –5mA ≤ IOUT ≤ 5mA
l
0.09
0.156
0.09
0.156
0.09
0.156
Ω
Internal Ref., Mid-Scale
VCC = 5V ±10%, –10mA ≤ IOUT ≤ 10mA
l
0.09
0.156
0.09
0.156
0.09
0.156
Ω
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VOUT DAC Output Span External Reference
Internal Reference
0 to VREF
0 to 2.5
V
V
PSR Power Supply Rejection VCC = 3V ±10% or 5V ±10% –80 dB
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
27
–27
48
–48
mA
mA
Power Supply
VCC Positive Supply Voltage For Specified Performance l2.7 5.5 V
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
0.5
0.6
0.6
0.7
0.7
0.8
0.8
0.9
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
20
30
µA
µA
LTC2634
6
2634fc
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.
LTC2634-LMI12/-LMI10/-LMI8/-LMX12/-LMX10/-LMX8/-LZ12/-LZ10/-LZ8 (VFS = 2.5V)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Reference Input
VREF Input Voltage Range l1 VCC V
Resistance l120 160 200 kΩ
Capacitance 14 pF
IREF Reference Current, Power-Down Mode DAC Powered Down l0.005 1.5 µA
Reference Output
Output Voltage l1.24 1.25 1.26 V
Reference Temperature Coefficient ±10 ppm/°C
Output Impedance 0.5 kΩ
Capacitive Load Driving 10 µF
Short-Circuit Current VCC = 5.5V, REF Shorted to GND 2.5 mA
Digital I/O
VIH Digital Input High Voltage VCC = 3.6V to 5.5V
VCC = 2.7V to 3.6V
l
l
2.4
2.0
V
V
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
VOH Digital Output High Voltage Load Current = –100µA lVCC – 0.4 V
VOL Digital Output Low Voltage Load Current = 100µA l0.4 V
ILK Digital Input Leakage VIN = GND to VCC l±1 µA
CIN Digital Input Capacitance (Note 8) l2.5 pF
AC Performance
tSSettling Time VCC = 3V (Note 9)
±0.39% (±1LSB at 8 Bits)
±0.098% (±1LSB at 10 Bits)
±0.024% (±1LSB at 12 Bits)
3.3
3.8
4.2
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
enOutput 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
LTC2634
7
2634fc
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.
LTC2634-LMI12/-LMI10/-LMI8/-LMX12/-LMX10/-LMX8/-LZ12/-LZ10/-LZ8 (VFS = 2.5V)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
t1SDI Valid to SCK Setup l4 ns
t2SDI Valid to SCK Hold l4 ns
t3SCK High Time l9 ns
t4SCK Low Time l9 ns
t5CS/LD Pulse Width l10 ns
t6LSB SCK High to CS/LD High l7 ns
t7CS/LD Low to SCK High l7 ns
t8CLR Pulse Width l20 ns
t9LDAC Pulse Width l15 ns
t10 CS/LD High to SCK Positive Edge l7 ns
SCK Frequency 50% Duty Cycle l50 MHz
t11 CS/LD High to LDAC High or Low Transition l200 ns
t12 SDO Propagation Delay from SCK Falling Edge CLOAD = 10pF
VCC = 4.5V to 5.5V
VCC = 2.7V to 5.5V
l
l
20
45
ns
ns
LTC2634
8
2634fc
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.
LTC2634-HMI12/-HMI10/-HMI8/-HMX12/-HMX10/-HMX8/-HZ12/-HZ10/-HZ8 (VFS = 4.096V)
LTC2634-8 LTC2634-10 LTC2634-12
SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX MIN TYP MAX UNITS
DC Performance
Resolution l8 10 12 Bits
Monotonicity VCC = 5V, Internal Ref. (Note 4) l8 10 12 Bits
DNL Differential Nonlinearity VCC = 5V, Internal Ref. (Note 4) l±0.5 ±0.5 ±1 LSB
INL Integral Nonlinearity VCC = 5V, Internal Ref. (Note 4) l±0.05 ±0.5 ±0.2 ±1 ±1 ±2.5 LSB
ZSE Zero-Scale Error VCC = 5V, Internal Ref., Code = 0 l0.5 5 0.5 5 0.5 5 mV
VOS Offset Error VCC = 5V, Internal Ref. (Note 5) l±0.5 ±5 ±0.5 ±5 ±0.5 ±5 mV
VOSTC VOS Temperature
Coefficient
VCC = 5V, Internal Ref. ±10 ±10 ±10 µV/°C
GE Gain Error VCC = 5V, Internal Ref. l±0.2 ±0.8 ±0.2 ±0.8 ±0.2 ±0.8 %FSR
GETC Gain Temperature
Coefficient
VCC = 5V, Internal Ref. (Note 10)
C-Grade
I-Grade
H-Grade
10
10
10
10
10
10
10
10
10
ppm/°C
ppm/°C
ppm/°C
Load Regulation VCC = 5V ±10%, Internal Ref., Mid-Scale,
–10mA ≤ IOUT ≤ 10mA
l
0.006
0.01
0.022
0.04
0.09
0.16
LSB/mA
ROUT DC Output Impedance VCC = 5V ±10%, Internal Ref., Mid-Scale,
–10mA ≤ IOUT ≤ 10mA
l
0.09
0.156
0.09
0.156
0.09
0.156
Ω
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VOUT DAC Output Span External Reference
Internal Reference
0 to VREF
0 to 4.096
V
V
PSR Power Supply Rejection VCC = 5V ±10% –80 dB
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
27
–27
48
–48
mA
mA
Power Supply
VCC Positive Supply Voltage For Specified Performance l4.5 5.5 V
ICC Supply Current (Note 7) VCC = 5V, VREF = 4.096V, External Reference
VCC = 5V, Internal Reference
l
l
0.6
0.7
0.8
0.9
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
20
30
µA
µA
LTC2634
9
2634fc
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.
LTC2634-HMI12/-HMI10/-HMI8/-HMX12/-HMX10/-HMX8/-HZ12/-HZ10/-HZ8 (VFS = 4.096V)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Reference Input
VREF Input Voltage Range l1 VCC V
Resistance l120 160 200 kΩ
Capacitance 14 pF
IREF Reference Current, Power-Down Mode DAC Powered Down l0.005 1.5 µA
Reference Output
Output Voltage l2.032 2.048 2.064 V
Reference Temperature Coefficient ±10 ppm/°C
Output Impedance 0.5 kΩ
Capacitive Load Driving 10 µF
Short-Circuit Current VCC = 5.5V, REF Shorted to GND 4 mA
Digital I/O
VIH Digital Input High Voltage l2.4 V
VIL Digital Input Low Voltage l0.8 V
VOH Digital Output High Voltage Load Current = –100µA lVCC – 0.4 V
VOL Digital Output Low Voltage Load Current = 100µA l0.4 V
ILK Digital Input Leakage VIN = GND to VCC l±1 µA
CIN Digital Input Capacitance (Note 8) l2.5 pF
AC Performance
tSSettling Time VCC = 5V (Note 9)
±0.39% (±1LSB at 8 Bits)
±0.098% (±1LSB at 10 Bits)
±0.024% (±1LSB at 12 Bits)
3.8
4.2
4.8
µs
µs
µs
Voltage Output Slew Rate 1.0 V/µs
Capacitive Load Driving 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
enOutput 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
LTC2634
10
2634fc
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.
LTC2634-HMI12/-HMI10/-HMI8/-HMX12/-HMX10/-HMX8/-HZ12/-HZ10/-HZ8 (VFS = 4.096V)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
t1SDI Valid to SCK Setup l4 ns
t2SDI Valid to SCK Hold l4 ns
t3SCK High Time l9 ns
t4SCK Low Time l9 ns
t5CS/LD Pulse Width l10 ns
t6LSB SCK High to CS/LD High l7 ns
t7CS/LD Low to SCK High l7 ns
t8CLR Pulse Width l20 ns
t9LDAC Pulse Width l15 ns
t10 CS/LD High to SCK Positive Edge l7 ns
SCK Frequency 50% Duty Cycle l50 MHz
t11 CS/LD High to LDAC High or Low Transition l200 ns
t12 SDO Propagation Delay from SCK Falling Edge CLOAD = 10pF
VCC = 4.5V to 5.5V
l
20
ns
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. Operating at temperatures
above 90°C and with VCC > 4V requires VCC slew rates to be no greater
than 73mV/ms.
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.
Note 5: Inferred from measurement at code 16 (LTC2634-12), code 4
(LTC2634-10) or code 1 (LTC2634-8), 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.
LTC2634
11
2634fc
typical perFormance characteristics
Integral Nonlinearity (INL) Differential Nonlinearity (DNL)
INL vs Temperature DNL vs Temperature
Reference Output Voltage
vs Temperature
Settling to ±1LSB Rising Settling to ±1LSB Falling
TA = 25°C, unless otherwise noted. LTC2634-L12 (Internal Reference, VFS = 2.5V)
CODE
0
INL (LSB)
1.0
0.5
0
–0.5
–1.0 1024 3072
2634 G01
40952048
VCC = 3V
CODE
0
DNL (LSB)
1.0
0.5
0
–0.5
–1.0 1024 3072
2634 G02
40952048
VCC = 3V
TEMPERATURE (°C)
–50
INL (LSB)
1.0
0.5
0
–0.5
–1.0 –25 125100755025
2634 G03
1500
VCC = 3V
INL (POS)
INL (NEG)
TEMPERATURE (°C)
–50
DNL (LSB)
1.0
0.5
0
–0.5
–1.0 –25 125100755025
2634 G04
1500
VCC = 3V
DNL (POS)
DNL (NEG)
TEMPERATURE (°C)
–50
VREF (V)
1.260
1.255
1.250
1.245
1.240 –25 125100755025
2634 G05
1500
VCC = 3V
2µs/DIV
CS/LD
5V/DIV
VOUT
1LSB/DIV
2634 G06
1/4 SCALE TO
3/4 SCALE STEP
VCC = 3V, VFS = 2.5V
RL = 2k, CL = 100pF
AVERAGE OF 256
EVENTS
3.1µs
LTC2634
12
2634fc
typical perFormance characteristics
Integral Nonlinearity (INL) Differential Nonlinearity (DNL)
INL vs Temperature DNL vs Temperature
Reference Output Voltage
vs Temperature
Settling to ±1LSB Rising Settling to ±1LSB Falling
TA = 25°C, unless otherwise noted. LTC2634-H12 (Internal Reference, VFS = 4.096V)
CODE
0
INL (LSB)
1.0
0.5
0
–0.5
–1.0 1024 3072
2634 G08
40952048
VCC = 5V
CODE
0
DNL (LSB)
1.0
0.5
0
–0.5
–1.0 1024 3072
2634 G09
40952048
VCC = 5V
TEMPERATURE (°C)
–50
INL (LSB)
1.0
0.5
0
–0.5
–1.0 –25 125100755025
2634 G10
1500
VCC = 5V
INL (POS)
INL (NEG)
TEMPERATURE (°C)
–50
DNL (LSB)
1.0
0.5
0
–0.5
–1.0 –25 125100755025
2634 G11
1500
VCC = 5V
DNL (POS)
DNL (NEG)
TEMPERATURE (°C)
–50
VREF (V)
2.068
2.058
2.048
2.038
2.028 –25 125100755025
2634 G12
1500
VCC = 5V
2µs/DIV
CS/LD
5V/DIV
VOUT
1LSB/DIV
2634 G13
1/4 SCALE TO
3/4 SCALE STEP
VCC = 5V, VFS = 4.095V
RL = 2k, CL = 100pF
AVERAGE OF 256
EVENTS
3.8µs
2µs/DIV
CS/LD
5V/DIV
VOUT
1LSB/DIV
2634 G14
1/4 SCALE TO
3/4 SCALE STEP
VCC = 5V, VFS = 4.095V
RL = 2k, CL = 100pF
AVERAGE OF 256
EVENTS
4.8µs
LTC2634
13
2634fc
typical perFormance characteristics
Integral Nonlinearity (INL) Differential Nonlinearity (DNL)
LTC2634-10
Integral Nonlinearity (INL) Differential Nonlinearity (DNL)
LTC2634-8
Load Regulation Current Limiting
LTC2634
Offset Error vs Temperature
TA = 25°C, unless otherwise noted
CODE
0
INL (LSB)
1.0
0.5
0
–0.5
–1.0 256 768
2634 G15
1023512
VCC = 3V
VFS = 2.5V
INTERNAL REF
CODE
0
DNL (LSB)
1.0
0.5
0
–0.5
–1.0 256 768
2634 G16
1023512
VCC = 3V
VFS = 2.5V
INTERNAL REF
CODE
0
INL (LSB)
0.50
0.25
0
–0.25
–0.50 64 192
2634 G17
255128
VCC = 3V
VFS = 2.5V
INTERNAL REF
CODE
0
DNL (LSB)
0.50
0.25
0
–0.25
–0.50 64 192
2634 G18
255128
VCC = 3V
VFS = 2.5V
INTERNAL REF
IOUT (mA)
–30
$VOUT (mV)
10
8
6
4
2
–6
–4
–2
0
–8
–10 –20 20100
2634 G19
30–10
VCC = 5V (LTC2634-H)
VCC = 5V (LTC2634-L)
VCC = 3V (LTC2634-L)
INTERNAL REF.
CODE = MID-SCALE
IOUT (mA)
–30
$VOUT (V)
0.20
0.15
0.10
0.05
–0.15
–0.01
–0.05
0
–0.20 –20 20100
2634 G20
30–10
VCC = 5V (LTC2634-H)
VCC = 5V (LTC2634-L)
VCC = 3V (LTC2634-L)
INTERNAL REF.
CODE = MID-SCALE
TEMPERATURE (°C)
–50
OFFSET ERROR (mV)
3
2
1
0
–1
–2
–3 –25 125100755025
2634 G21
1500
LTC2634
14
2634fc
typical perFormance characteristics
Large-Signal Response Mid-Scale Glitch Impulse Power-On Reset Glitch
Headroom at Rails
vs Output Current Exiting Power-Down to Mid-Scale Power-On Reset to Mid-Scale
Supply Current vs Logic Voltage Hardware CLR Hardware CLR to Mid-Scale
LTC2634
TA = 25°C, unless otherwise noted
2µs/DIV
VOUT
0.5V/DIV
2634 G22
VFS = VCC = 5V
1/4 SCALE to 3/4 SCALE
2µs/DIV
VOUT
5mV/DIV
CS/LD
5V/DIV
2634 G23
LTC2634-H12, VCC = 5V
3.0nV•s TYP
LTC2634-L12, VCC = 3V
2.1nV•s TYP
200µs/DIV
VOUT
5mV/DIV
VCC
2V/DIV
2636 G24
LTC2634-L
ZERO SCALE
IOUT (mA)
0
VOUT (V)
5.0
4.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0.5
01 7 8 96543
2634 G25
102
5V SOURCING
3V (LTC2634-L) SOURCING
3V (LTC2634-L) SINKING
5V SINKING
5µs/DIV
VOUT
0.5V/DIV
CS/LD
2V/DIV
2634 G26
LTC2634-H
VCC = 5V
INTERNAL REF
DACs A-C IN
POWER-DOWN
MODE
200µs/DIV
VCC
2V/DIV
VOUT
0.5V/DIV
2634 G27
LTC2634-H
LTC2634-L
1µs/DIV
CLR
5V/DIV
VOUT
1V/DIV
2634 G29
VCC = 5V
VREF = 4.096V
CODE = FULL-SCALE
1µs/DIV
VOUT
1V/DIV
CLR
5V/DIV
2634 G30
VCC = 5V
VREF = 4.096V
CODE = FULL-SCALE
LOGIC VOLTAGE (V)
0
ICC (mA)
1.0
1.2
1.4
4
2634 G28
0.8
0.6
0.4 1235
VCC = 5V
VCC = 3V
(LTC2634-L)
SWEEP SCK, SDI, CS/LD
BETWEEN 0V AND VCC
LTC2634
15
2634fc
typical perFormance characteristics
Mulitplying Bandwidth Noise Voltage vs Frequency Gain Error vs Reference Input
0.1Hz to 10Hz Voltage Noise DAC-to-DAC Crosstalk (Dynamic) Gain Error vs Temperature
LTC2634
TA = 25°C, unless otherwise noted
FREQUENCY (Hz)
100
NOISE VOLTAGE (nV/√Hz)
500
400
300
200
100
01k 100k
2636 G32
1M10k
VCC = 5V
CODE = MID-SCALE
INTERNAL REF
LTC2634-H
LTC2634-L
1s/DIV
10µV/DIV
2634 G34
VCC = 5V, VFS = 2.5V
CODE = MID-SCALE
INTERNAL REF
2µs/DIV
VOUT
1mV/DIV
1 DAC
SWITCH 0-FS
2V/DIV
CS/LD
5V/DIV
2634 G35
LTC2634-H12, VCC = 5V
2.4nV•s TYP
CREF = 0.1µF
TEMPERATURE (°C)
–50
GAIN ERROR (%FSR)
1.0
0.5
0
–0.5
–1.0 –25 125100755025
2634 G36
1500
REFERENCE VOLTAGE (V)
1
GAIN ERROR (%FSR)
1.0
0.8
0.6
0.4
–0.6
–0.8
–0.4
–0.2
0.2
0
–1.0 1.5 54.54
2634 G33
5.52 2.5 3 3.5
VCC = 5.5V
GAIN ERROR OF 4 CHANNELS
LTC2634
16
2634fc
pin Functions
(QFN/MSOP)
VOUTA to VOUTD (Pins 1-2, 11-12/Pins 2-3, 8-9): DAC
Analog Voltage Outputs.
LDAC (Pin 3, QFN 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.
CS/LD (Pin 4/Pin 4): Serial Interface Chip Select/Load
Input. When CS/LD is low, SCK is enabled for shifting
data on SDI into the 32-bit shift register. When CS/LD is
taken high, SCK is disabled and the specified command
(see Table 1) is executed.
SCK (Pin 5/Pin 5): Serial Interface Clock Input. CMOS
and TTL compatible.
DNC (Pins 6, 15, QFN Only): Do not connect these
pins.
SDO (Pin 7, QFN Only): Serial Interface Data Output. The
serial output of the 32-bit shift register appears at the SDO
pin. The data transferred to the device via the SDI pin is
delayed 32 SCK rising edges before being output at the
next falling edge. This pin is used for daisy-chain opera-
tion, it is always driven and never goes high impedance,
even when CS/LD is high. See the Daisy-Chain Operation
section.
SDI (Pin 8/Pin 6): Serial Interface Data Input. Data on
SDI is clocked into the DAC on the rising edge of SCK.
The LTC2634 accepts input word lengths of either 24 or
32 bits.
CLR (Pin 9, QFN 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
(LTC2634-Z) or mid-scale (LTC2634-MI/-MX). CMOS and
TTL compatible.
REF (Pin 10/Pin 7): 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 (LTC2634-L) or 2.048V
(LTC2634-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.
REFLO (Pin 13, QFN only): Reference Low Pin. The voltage
at this pin sets the zero-scale voltage of all DACs. This pin
must be tied to GND.
GND (Pin 14/Pin 10): Ground.
VCC (Pin 16/Pin 1): Supply Voltage Input. 2.7V ≤ VCC ≤
5.5V (LTC2634-L) or 4.5V ≤ VCC ≤ 5.5V (LTC2634-H).
Bypass to GND with a 0.1µF capacitor.
Exposed Pad (Pin 17/Pin 11): Ground. Must be soldered
to PCB ground.
LTC2634
17
2634fc
Block Diagram
REGISTER
REGISTER
REGISTER
REGISTER
DAC A
VOUTA
(REFLO)
CS/LD
SCK
( ) QFN PACKAGE ONLY
(LDAC)
GND
VOUTB
VREF
DAC D
REGISTER
REGISTER
REGISTER
REGISTER
DAC B DAC C
VREF
VOUTD
REF
VCC
VREF
VOUTC
SWITCH
INTERNAL
REFERENCE
32-BIT SHIFT REGISTER
DECODE
CONTROL
LOGIC
POWER-ON
RESET
SDI
2634 BD
(SDO)
(CLR)
LTC2634
18
2634fc
timing Diagrams
SDI
SDO
CS/LD
SCK
2634 F01a
t2
t12
t10
t5t7
t6
t1
LDAC
t3t4
1 2 3 23 24
t11 t9
CS/LD
2634 F01b
t11
LDAC
Figure 1a
Figure 1b
LTC2634
19
2634fc
operation
The LTC2634 is a family of quad voltage output DACs in
16-lead QFN and 10-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 LTC2634
is controlled using a 3-wire SPI/MICROWIRE compatible
interface.
Power-On Reset
The LTC2634-HZ/LTC2634-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 LTC2634
contains circuitry to reduce the power-on glitch: the
analog output typically rises less than 5mV above zero-
scale 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 LTC2634-HMI/LTC2634-HMX/LTC2634-LMI/
LTC2634-LMX provide an alternative reset, setting the
output to mid-scale when power is first applied. The
LTC2634-LMI and LTC2634-HMI power up in internal
reference mode, with the output set to a mid-scale volt-
age of 1.25V and 2.048V, respectively. The LTC2634-LMX
and LTC2634-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 Refer-
ence Modes section.
Power Supply Sequencing
The voltage at REF (Pin 10, QFN/Pin 7, 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 turn-
on and turn-off sequences, when the voltage at VCC is in
transition.
Transfer Function
The digital-to-analog transfer function is:
VkV V V
OUT IDEAL NREF REFLO REFLO( ) –=
( )
+
2
where k is the decimal equivalent of the binary DAC
input code, N is the resolution, and VREF is either 2.5V
(LTC2634-LMI/LTC2634-LMX/LTC2634-LZ) or 4.096V
(LTC2634-HMI/LTC2634-HMX/LTC2634-HZ) when in
internal reference mode, and the voltage at REF when in
external reference mode. The resulting DAC output span
is 0V to VREF
, as it is necessary to tie REFLO to GND.
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 at 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 (LTC2634-12/LTC2634-10/LTC2634-8 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
LTC2634
20
2634fc
operation
C3
COMMAND
Input Word (LTC2634-12)
ADDRESS DATA (12 BITS + 4 DON’T CARE BITS)
C2 C1 C0 A3 A2 A1 A0 D9D10D11 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X X
MSB LSB
C3
COMMAND
Input Word (LTC2634-10)
ADDRESS DATA (10 BITS + 6 DON’T CARE BITS)
C2 C1 C0 A3 A2 A1 A0 D7D8D9 D6 D5 D4 D3 D2 D1 D0 X X X X X X
MSB LSB
C3
COMMAND
Input Word (LTC2634-8)
ADDRESS DATA (8 BITS + 8 DON’T CARE BITS)
C2 C1 C0 A3 A2 A1 A0 D5D6D7 D4 D3 D2 D1 D0 XXX X X X X X
MSB LSB 2634 F02
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 DACs 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
1 1 1 1 All DACs
* Address codes not shown are reserved and should not be used.
Figure 2. Command and Data Input Format
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 operation. 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.
LTC2634
21
2634fc
operation
While the minimum input sequence is 24 bits, it may
optionally be extended to 32 bits to accommodate micro-
processors 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.
Daisy-Chain Operation (QFN Package)
The serial output of the shift register appears at the SDO
pin on the QFN package. Data transferred to the device
from the SDI input is delayed 32 SCK rising edges before
being output at the next SCK falling edge, therefore, daisy
chaining multiple LTC2634 DACs requires 32-bit data
write cycles.
The SDO output can be used to facilitate control of multiple
serial devices from a single 3-wire serial port (i.e., SCK,
SDI and CS/LD). Such a “daisy-chain” series is configured
by connecting SDO of each upstream device to SDI of the
next device in the chain. The shift registers of the devices
are thus connected in series, effectively forming a single
input shift register which extends through the entire chain.
Because of this, the devices can be addressed and controlled
individually by simply concatenating their input words;
the first instruction addresses the last device in the chain
and so forth. The SCK and CS/LD signals are common to
all devices in the series. Figure 5 shows a block diagram
for daisy-chain operation.
In use, CS/LD is first taken low. Then the concatenated
input data is transferred to the chain, using SDI of the
first device as the data input. When the data transfer is
complete, CS/LD is taken high, completing the instruction
sequence for all devices simultaneously. A single device
can be controlled by using the no-operation command
(1111) for the other devices in the chain.
Reference Modes
For applications where an accurate external reference is
either not available, or not desirable due to limited space,
the LTC2634 has a low noise, user-selectable, integrated
reference. The integrated reference voltage is internally
amplified by 2x to provide the full-scale DAC output volt-
age range. The LTC2634-LMI/LTC2634-LMX/LTC2634-LZ
provides a full-scale DAC output of 2.5V. The LTC2634-
HMI/LTC2634-HMX/LTC2634-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
LTC2634-HZ/LTC2634-LZ, as well as for LTC2634-HMI/
LTC2634-LMI.
The 10ppm/°C, 1.25V (LTC2634-LMI/LTC2634-LMX/
LTC2634-LZ) or 2.048V (LTC2634-HMI/LTC2634-HMX/
LTC2634-HZ) internal reference is available at the REF pin.
Adding bypass capacitance to the REF pin will improve
noise performance; 0.1µF is recommended, 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 LTC2634-HMX/LTC2634-LMX.
The reference mode of LTC2634-HZ/LTC2634-LZ/
LTC2634-HMI/LTC2634-LMI (internal reference power-on
default), can be changed by software command after power
up. The same is true for LTC2634-HMX/-LMX (external
reference power-on default).
The LTC2634’s QFN package offers a REFLO pin for the
negative reference. REFLO must be connected to GND.
LTC2634
22
2634fc
operation
Power-Down Mode
For power-constrained applications, power-down mode can
be used to reduce the supply current whenever less than
four 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 200k 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 20% 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 power-
down 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 imped-
ance (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 pull-
ing the asynchronous LDAC pin low. The selected DAC
is powered 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 four
DACs are in a powered-down state prior to the update
command, the power-up delay time is 10µs. However, if
all four 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 com-
mand (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 Output
The LTC2634’s integrated rail-to-rail amplifier has guaran-
teed 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 Character-
istics section.
The amplifier is stable driving capacitive loads of up to
500pF.
LTC2634
23
2634fc
operation
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 LTC2634 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 LTC2634 is no more susceptible to
this effect than any other parts of this type; on the con-
trary, 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 sepa-
rate 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 LTC2634 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.
LTC2634
24
2634fc
operation
12345678910 11 12 13 14 15 16 17 18 19 20 21 22 23 24
C2 C1 C0 A3 A2 A1 A0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X XC3
CS/LD
SCK
SDI
COMMAND WORD ADDRESS DATA WORD
24-BIT INPUT WORD
2634 F03a
Figure 3a. LTC2634-12 24-Bit Load Sequence (Minimum Input Word)
LTC2634-10 SDI Data Word: 10-Bit Input Code + 6 Don’t Care Bits
LTC2634-8 SDI Data Word: 8-Bit Input Code + 8 Don’t Care Bits
Figure 3b. LTC2634-12 32-Bit Load Sequence (Required for Daisy-Chain Operation)
LTC2634-10 SDI Data Word: 10-Bit Input Code + 6 Don’t Care Bits
LTC2634-8 SDI Data Word: 8-Bit Input Code + 8 Don’t Care Bits
12345678910 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
C2 C1 C0 A3 A2 A1 A0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X XC3XXXXXXXX
CS/LD
SCK
SDI
COMMAND WORD ADDRESS WORD DATA WORD
DON’T CARE
C2 C1 C0 A3 A2 A1 A0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X XC3XXXXXXXX
SDO
CURRENT
32-BIT
INPUT WORD
2634 F03b
PREVIOUS 32-BIT INPUT WORD
t2
t3t4
t1
t12
D11
17
SCK
SDI
SDO PREVIOUS D10PREVIOUS D11
18
D10
LTC2634
25
2634fc
operation
2634 F04
INPUT CODE
(4b)
(4a)
(4c)
OUTPUT
VOLTAGE
NEGATIVE
OFFSET
0V
2,0480
0V 4,095
INPUT CODE
OUTPUT
VOLTAGE
VREF = VCC
VREF = VCC
INPUT CODE
OUTPUT
VOLTAGE
POSITIVE
FSE
Figure 4. Effects of Rail-to-Rail Operation on a DAC Transfer Curve (Shown in 12 Bits)
(4a) Overall Transfer Function
(4b) Effect of Negative Offset for Codes Near Zero
(4c) Effect of Postitive Full-Scale Error for Codes Near Full-Scale
SDI SDO
LTC2634UD
SCK
5
6 7 6 7 6 7 DATA OUTPUT
4CS/LD
SDI SDO
SCK
5
4CS/LD
SDI SDO
2634 F05
SCK
5
4CS/LD
CS/LD
SCK
SDI
LTC2634UD LTC2634UD
• • •
Figure 5. Daisy-Chain Operation (QFN Only)
LTC2634
26
2634fc
typical application
–
+
DAC A
DAC D
LTC2755
RCOM1
RIN1 60 0.1µF
0.1µF 0.1µF
2
3
4
5
6
OUTA
2
3
59 1
4
8
2
58
19
5
6
7
4
–15V
15V
8
ROFSA RFBA
RVOSA
GND
IOUT1A
IOUT2A
VDD
15
5V
61
0.1µF
0.1µF
OUTC
–15V
30k
LT1634-1.25
OUTB
0.1µF
64
63
62 REFA
–
+
1/2 LT1469
1/2 LT1469
–
+
LTC6240
15V
–15V
DAC C
+
–
+
–
DAC B
–15V
30k
–15V
30k SERIAL
BUS
DAC A
DAC B
CS/LD
SCK 10
2634 TA02
8
9
0.1µF
1
GND
7REF LTC2634MSE-LMI12 VCC
SDI
DAC C
DAC D
M9
M3
M1 OUT VOUT
±5V
LT1991
REF
VEE
VCC
8
9
10
P1
P3
P9
1
2
3
5V 0.1µF
0.1µF
4
7
5
6
15V
–15V
LT1634-1.25
LT1634-1.25
LTC2634 DACs Adjusts LTC2755-16 Offsets, Amplified with LT
®
1991 PGA to ±5V
LTC2634
27
2634fc
package Description
UD Package
16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691)
3.00 p 0.10
(4 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1.45 p 0.05
(4 SIDES)
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)
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
PIN 1
TOP MARK
(NOTE 6)
0.40 p 0.10
BOTTOM VIEW—EXPOSED PAD
1.45 p 0.10
(4-SIDES)
0.75 p 0.05 R = 0.115
TYP
0.25 p 0.05
1
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 s 45o CHAMFER
15 16
2
0.50 BSC
0.200 REF
2.10 p 0.05
3.50 p 0.05
0.70 p0.05
0.00 – 0.05
(UD16) QFN 0904
0.25 p0.05
0.50 BSC
PACKAGE OUTLINE
LTC2634
28
2634fc
package Description
MSE Package
10-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1664 Rev D)
MSOP (MSE) 0210 REV D
0.53 p 0.152
(.021 p .006)
SEATING
PLANE
0.18
(.007)
1.10
(.043)
MAX
0.17 – 0.27
(.007 – .011)
TYP
0.86
(.034)
REF
0.50
(.0197)
BSC
1 2 34 5
4.90 p 0.152
(.193 p .006)
0.497 p 0.076
(.0196 p .003)
REF
8910
10
1
76
3.00 p 0.102
(.118 p .004)
(NOTE 3)
3.00 p 0.102
(.118 p .004)
(NOTE 4)
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
6. EXPOSED PAD DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD
SHALL NOT EXCEED 0.254mm (.010") PER SIDE.
0.254
(.010) 0o – 6o TYP
DETAIL “A”
DETAIL “A”
GAUGE PLANE
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
0.889 p 0.127
(.035 p .005)
RECOMMENDED SOLDER PAD LAYOUT
0.305 p 0.038
(.0120 p .0015)
TYP
1.68 p 0.102
(.066 p .004)
1.88 p 0.102
(.074 p .004)
0.50
(.0197)
BSC
BOTTOM VIEW OF
EXPOSED PAD OPTION
1.68
(.066)
1.88
(.074)
0.1016 p 0.0508
(.004 p .002)
DETAIL “B”
DETAIL “B”
CORNER TAIL IS PART OF
THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
NO MEASUREMENT PURPOSE
0.05 REF
0.29
REF
LTC2634
29
2634fc
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
revision history
REV DATE DESCRIPTION PAGE NUMBER
A 10/09 Changes to Electrical Characteristics maximum limits 5, 6, 8, 9
B 12/09 Change pin name to DNC 2, 16
C 06/10 Revised Note 3 in the Electrical Characteristics section
Added Typical Application and replaced Related Parts list
10
30
LTC2634
30
2634fc
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
LINEAR TECHNOLOGY CORPORATION 2009
LT 0610 REV C • PRINTED IN USA
relateD parts
typical application
–
+
DAC A
DAC D
LTC2755
RCOM1
RIN1 60 0.1µF
0.1µF 0.1µF
2
3
4
5
6
OUTA
2
3
59 1
4
8
2
58
19
5
6
7
4
–15V
15V
8
ROFSA RFBA
RVOSA
GND
IOUT1A
IOUT2A
VDD
15
5V
61
0.1µF
0.1µF
OUTC
–15V
30k
LT1634-1.25
OUTB
0.1µF
64
63
62 REFA
–
+
1/2 LT1469
1/2 LT1469
–
+
LTC6240
15V
–15V
DAC C
+
–
+
–
DAC B
–15V
30k
–15V
30k SERIAL
BUS
DAC A
DAC B
CS/LD
SCK 10
2634 TA02
8
9
0.1µF
1
GND
7REF LTC2634MSE-LMI12 VCC
SDI
DAC C
DAC D
M9
M3
M1 OUT VOUT
±5V
LT1991
REF
VEE
VCC
8
9
10
P1
P3
P9
1
2
3
5V 0.1µF
0.1µF
4
7
5
6
15V
–15V
LT1634-1.25
LT1634-1.25
LTC2634 DACs Adjusts LTC2755-16 Offsets, Amplified with LT1991 PGA to ±5V
PART NUMBER DESCRIPTION COMMENTS
LTC2654/LTC2655 Quad 16-/12 Bit, SPI/I2C VOUT DACs with 10ppm/°C
Maximum Reference
±4LSB INL Maximum at 16 Bits and ±2mV Offset Error, Rail-to-Rail Output,
20-Lead 4mm × 4mm QFN and 16-Lead Narrow SSOP Packages
LTC2604/LTC2614/
LTC2624
Quad 16-/14-/12-Bit, SPI VOUT DACs with External
Reference
250µA per DAC, 2.5V to 5.5V Supply Range, Rail-to-Rail Output, 16-Lead
SSOP Package
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
LTC2635 Quad 12-/10-/8-Bit I2C VOUT DACs with 10ppm/°C
Reference
±2.5LSB INL, 2.7V to 5.5V Supply Range, 10ppm/°C Reference, External
REF Mode, 16-Pin 3mm × 3mm QFN and 10-Lead MSOP Packages
LTC2656/LTC2657 Octal 16-/12 Bit, SPI/I2C VOUT DACs with 10ppm/°C
Maximum Reference
±4LSB INL Maximum at 16 Bits and ±2mV Offset Error, Rail-to-Rail Output,
20-Lead 4mm × 5mm QFN and 16-Lead TSSOP Packages
LTC2636/LTC2637 Octal 12-/10-/8-Bit, SPI/I2C VOUT DACs with 10ppm/°C
Reference
125µA per DAC, 2.7V to 5.5V Supply Range, 10ppm/°C Reference, External
REF Mode, Rail-to-Rail Output, 14-Lead 4mm × 3mm DFN and 16-Lead
MSOP Packages
LTC2630/LTC2631 Single 12-/10-/8-Bit, SPI/ I2C VOUT DACs with
10ppm/°C Reference
180µA per DAC, 2.7V to 5.5V Supply Range, 10ppm/°C Reference, Rail-to-
Rail Output, SC70 (LTC2630)/ThinSOT™ (LTC2631) Packages
LTC2640 Single 12-/10-/8-Bit, SPI VOUT DACs with 10ppm/°C
Reference
180µA per DAC, 2.7V to 5.5V Supply Range, 10ppm/°C Reference, External
REF Mode, Rail-to-Rail Output, ThinSOT Package
LTC1664 Quad 10-Bit, Serial VOUT DAC VCC = 2.7V to 5.5V, Micropower, Rail-to-Rail Output in 16-Pin Narrow SSOP
Amplifiers
LT1991 Precision, 100µA Gain Selectable Amplifier Gain Accuracy of 0.04%, Gains from –13 to 14, 100µA precision Op Amp
LT1469 Dual 90MHz, 22V/µs 16-Bit Accurate Operational
Amplifier
90MHz Gain Bandwidth, 125µV Offset, 900ns, 22V/µs Slew Rate Precision
Op Amp