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LTC1446/LTC1446L Dual 12-Bit Rail-to-Rail Micropower DACs in SO-8
FEATURES
s s s s s s s s s s s
DESCRIPTIO
Dual DACs with 12-Bit Resolution SO-8 Package Rail-to-Rail Output Amplifiers 3V Operation (LTC1446L): ICC = 650A Typ 5V Operation (LTC1446): ICC = 1000A Typ Internal Reference Power-On Reset Clears DACs to 0V 3-Wire Cascadable Serial Interface Maximum DNL Error: 0.5LSB Low Cost Schmitt Trigger On Input Allows Direct Optocoupler Interface
The LTC(R)1446/LTC1446L are dual 12-bit digital-to-analog converters (DACs) available in an SO-8 package. They are complete with a rail-to-rail voltage output amplifier, an internal reference and an easy-to-use 3-wire cascadable serial interface. The LTC1446 has an internal reference and a full-scale output of 4.095V. It operates from a single 4.5V to 5.5V supply. The LTC1446L has an internal reference and a full-scale output of 2.5V. It operates from a single 2.7V to 5.5V supply. The low power supply current makes the LTC1446 family ideal for battery-powered applications. These DACs are available in space saving 8-pin SO and PDIP packages and require no external components for operation.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATI
s s s s
S
Digital Calibration Industrial Process Control Automatic Test Equipment Cellular Telephones
TYPICAL APPLICATI
7 VCC 2 DIN
Functional Block Diagram: Dual 12-Bit Rail-to-Rail DAC
LTC1446: 5V LTC1446L: 3V TO 5V
+
12-BIT DAC B
VOUT B 8
1 CLK 3 CS/LD 24-BIT SHIFT REG AND DAC LATCH 12-BIT DAC A 4 DOUT POWER-ON RESET GND 6
1446/1446L TA01
DNL ERROR (LSB)
P
-
RAIL-TO-RAIL VOLTAGE OUTPUT
-0.1 -0.2 -0.3 -0.4 -0.5 0 512 1024 1536 2048 2560 3072 3584 4095 CODE
1446/46L G13
+ -
VOUT A 5
U
Differential Nonlinearity vs Input Code
0.5 0.4 0.3 0.2 0.1 0
UO
UO
1
LTC1446/LTC1446L ABSOLUTE AXI U RATI GS
VOUT A /VOUT B ................................. -0.5V to VCC + 0.5V Maximum Junction Temperature .......................... 125C Storage Temperature Range ..................-65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C VCC to GND ................................................ -0.5 to 7.5V Logic Inputs to GND ................................... -0.5 to 7.5V Operating Temperature Range LTC1446C/LTC1446LC ............................ 0C to 70C LTC1446I/LTC1446LI ..........................-40C to 85C
PACKAGE/ORDER INFORMATION
TOP VIEW CLK 1 DIN 2 CS/LD 3 DOUT 4 N8 PACKAGE 8-LEAD PDIP
TJMAX = 125C, JA = 100C/W
ORDER PART NUMBER
8 7 6 5 VOUT B VCC GND VOUT A
LTC1446CN8 LTC1446IN8 LTC1446LCN8 LTC1446LIN8
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
VCC = 4.5V to 5.5V (LTC1446), 2.7V to 5.5V (LTC1446L), VOUT A and VOUT B unloaded, TA = TMIN to TMAX, unless otherwise noted.
SYMBOL DAC Resolution DNL INL ZSE VOS VOS TC VFS Differential Nonlinearity Integral Nonlinearity Zero-Scale Error Offset Error Offset Error Tempco Full-Scale Voltage LTC1446, TA = 25C LTC1446 LTC1446L, TA = 25C LTC1446L
q q q
PARAMETER
CONDITIONS
Guaranteed Monotonic (Note 1) TA = 25C
VFS TC VCC ICC VCC ICC
Full-Scale Voltage Tempco Positive Supply Voltage Supply Current Positive Supply Voltage Supply Current For Specified Performance 4.5V VCC 5.5V (Note 4) For Specified Performance 2.7V VCC 5.5V (Note 4)
q q
Power Supply (LTC1446) 4.5 1000 2.7 650 5.5 1500 5.5 1000 V A V A
Power Supply (LTC1446L)
q q
2
U
U
W
WW
U
W
TOP VIEW CLK 1 DIN 2 CS/LD 3 DOUT 4 8 7 6 5 VOUT B VCC GND VOUT A
ORDER PART NUMBER LTC1446CS8 LTC1446IS8 LTC1446LCS8 LTC1446LIS8 S8 PART MARKING 1446C 1446LC 1446I 1446LI
S8 PACKAGE 8-LEAD PLASTIC SO
TJMAX = 125C, JA = 150C/W
MIN 12
TYP
MAX
UNITS Bits
q q q q
0.2 2.0 2.5 0 3 2 15 4.065 4.045 2.470 2.460 4.095 4.095 2.500 2.500 0.1
0.5 4.5 5.0 18 18 4.125 4.145 2.530 2.540
LSB LSB LSB mV mV V/C V V V V LSB/C
LTC1446/LTC1446L
ELECTRICAL CHARACTERISTICS
VCC = 4.5V to 5.5V (LTC1446), 2.7V to 5.5V (LTC1446L), VOUT A and VOUT B unloaded, TA = TMIN to TMAX, unless otherwise noted.
SYMBOL PARAMETER Short-Circuit Current Low Short-Circuit Current High Output Impedance to GND AC Performance Voltage Output Slew Rate Voltage Output Settling Time (Note 2) (Notes 2, 3) to 0.5LSB
q
CONDITIONS VOUT Shorted to GND VOUT Shorted to VCC Input Code = 0
q q q
MIN
TYP 55 70 40
MAX 120 120 120
UNITS mA mA V/s s
Op Amp DC Performance
0.5
1 14
VCC = 5V (LTC1446), VCC = 3V (LTC1446L), TA = TMIN to TMAX, unless otherwise noted.
SYMBOL Digital I/O VIH VIL VOH VOL ILEAK CIN Switching t1 t2 t3 t4 t5 t6 t7 t8 t9 DIN Valid to CLK Setup DIN Valid to CLK Hold CLK High Time CLK Low Time CS/LD Pulse Width LSB CLK to CS/LD CS/LD Low to CLK DOUT Output Delay CLK Low to CS/LD Low CLOAD = 15pF
q q q q q q q q q
PARAMETER Digital Input High Voltage Digital Input Low Voltage Digital Output High Voltage Digital Output Low Voltage Digital Input Leakage Digital Input Capacitance
CONDITIONS
q q
MIN 2.4
LTC1446 TYP MAX
MIN 2
LTC1446L TYP MAX
UNITS V
0.8 VCC - 1.0 0.4 10 10 40 0 40 40 50 40 20 150 20 30 60 0 60 60 80 60 30 VCC - 0.7
0.6 0.4 10 10
V V V A pF ns ns ns ns ns ns ns
IOUT = - 1mA IOUT = 1mA VIN = GND to VCC Guaranteed by Design
q q q q
220
ns ns
The q denotes specifications which apply over the full operating temperature range. Note 1: Nonlinearity is defined from the first code that is greater than or equal to the maximum offset specification to code 4095 (full scale).
Note 2: Load is 5k in parallel with 100pF. Note 3: DAC switched between all 1s and the code corresponding to VOS for the part. Note 4: Digital inputs at 0V or VCC.
3
LTC1446/LTC1446L TYPICAL PERFORMANCE CHARACTERISTICS
LTC1446 Differential Nonlinearity (DNL)
0.5 0.4 0.3
DNL ERROR (LSB)
1 0 -1 -2 -3 0
0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 0 512 1024 1536 2048 2560 3072 3584 4095 CODE
1446/46L G01
DNL ERROR (LSB)
INL ERROR (LSB)
0.2
LTC1446L Integral Nonlinearity
3 2
0.6 0.8
INL ERROR (LSB)
VCC - VOUT (V)
1 0 -1 -2 -3 0
0.4
VCC - VOUT
512 1024 1536 2048 2560 3072 3584 4095 CODE
1446/46L G04
LTC1446 Min Output Voltage vs Output Sink Current
600 CODE: ALL 0'S 4.11
OUTPUT PULL-DOWN VOLTAGE (mV)
500
FULL-SCALE VOLTAGE (V)
400 125C 300 -55C 200 100 0 25C
SUPPLY CURRENT (mA)
0
5 10 OUTPUT SINK CURRENT (mA)
LTC1446/46L * TPC07
4
UW
LTC1446 Integral Nonlinearity (INL)
3 2
0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4
LTC1446L Differential Nonlinearity
512 1024 1536 2048 2560 3072 3584 4095 CODE
1446/46L G02
-0.5 0 512 1024 1536 2048 2560 3072 3584 4095 CODE
1446/46L G03
LTC1446 Min Supply Headroom for Full Output Swing vs Load Current
VOUT < 1LSB CODE: ALL 1's VOUT = 4.095V
LTC1446L Min Supply Headroom for Full Output Swing vs Load Current
1.2 1.0 0.8 0.6 0.4 VOUT < 1LSB CODE: ALL 1's VOUT = 2.5V
0.2
0.2
0
0
10 5 LOAD CURRENT (mA)
15
0 0 5 10 LOAD CURRENT (mA) 15
LTC1446/46L * TPC05
LTC1446/46L * TPC06
LTC1446 Full-Scale Voltage vs Temperature
3.0 2.6
LTC1446 Supply Current vs Logic Input Voltage
4.10
2.2 1.8 1.4 1.0
4.09
4.08
15
4.07 -55
-25
5 35 65 TEMPERATURE (C)
95
125
0.6 0 1 2 3 4 LOGIC INPUT VOLTAGE (V) 5
1446/46L G09
1446/46L G09
LTC1446/LTC1446L TYPICAL PERFORMANCE CHARACTERISTICS
LTC1446L Supply Current vs Logic Input Voltage
1.2 1.1
970 960
SUPPLY CURRENT (A)
SUPPLY CURRENT (A)
SUPPLY CURRENT (mA)
1.0 0.9 0.8 0.7 0.6 0.5 0.5
1.0
1.5
2.0
LOGIC INPUT VOLTAGE (V)
1446/46L G10
PIN FUNCTIONS
CLK: The Serial Interface Clock. DIN: The Serial Interface Data. CS/LD: The Serial Interface Enable and Load Control. When CS/LD is low the CLK signal is enabled, so the data can be clocked in. When CS/LD is pulled high data is loaded from the shift register into the DAC registers, updating the DAC outputs. DOUT: The output of the shift register which becomes valid on the rising edge of the serial clock. GND: Ground. VOUT A,VOUT B: Buffered DAC Outputs. VCC: Positive Supply Input. 4.5V VCC 5.5V (LTC1446), 2.7V VCC 5.5V (LTC1446L). Requires a bypass capacitor to ground.
UW
2.5
LTC1446 Supply Current vs Temperature
700 690 680 670 660 650 640 630
LTC1446L Supply Current vs Temperature
950 940 930 920 910
VCC = 5.5V
VCC = 3.3V
VCC = 3V
VCC = 5V
VCC = 2.7V
VCC = 4.5V 5 25 45 65 85 105 125 TEMPERATURE (C)
1446/46L G11
3.0
900 -55 -35 -15
620 - 55 - 35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1446/46L G12
U
U
U
5
LTC1446/LTC1446L
BLOCK DIAGRAM
CLK 1
DIN 2
CS/LD 3
DOUT 4
TI I G DIAGRA
CLK
t9 B0-B PREVIOUS WORD B11-A MSB B0-A LSB B11-B MSB B0-B LSB t5
DIN
CS/LD
DOUT
B11-A PREVIOUS WORD
6
W
W
REFERENCE LD DAC B REGISTER 12-BIT DAC B
+
8 VOUT B
-
24-BIT SHIFT REGISTER LD DAC A REGISTER
7
VCC
6 12-BIT DAC A
GND
+
5 VOUT A
-
POWER-ON RESET
1446BD
UW
t4
t3
t1 t2 t6 t7
t8
B10-A PREVIOUS WORD
B0-A PREVIOUS WORD
B11-B PREV WORD
B10-B PREV WORD
B0-B PREV WORD
B11-A CURRENT WORD
1446 TD
LTC1446/LTC1446L
DEFI ITIO S
Resolution (n) Resolution is defined as the number of digital input bits, n. It defines the number of DAC output states (2n) that divide the full-scale range. The resolution does not imply linearity. Full-Scale Voltage (VFS) This is the output of the DAC when all bits are set to one. Voltage Offset Error (VOS) The theoretical voltage at the output when the DAC is loaded with all zeros. The output amplifier can have a true negative offset, but because the part is operated from a single supply, the output cannot go below zero. If the offset is negative, the output will remain near 0V resulting in the transfer curve shown in Figure 1.
OUTPUT VOLTAGE
NEGATIVE OFFSET
Figure 1. Effect of Negative Offset
The offset of the part is measured at the code that corresponds to the maximum offset specification: VOS = VOUT - [(Code)(VFS)/(2n - 1)] Least Significant Bit (LSB) One LSB is the ideal voltage difference between two successive codes. LSB = (VFS - VOS)/(2n - 1) = (VFS - VOS)/4095
U
U
Nominal LSBs: LTC1446 LSB = 4.095V/4095 = 1mV LTC1446L LSB = 2.5V/4095 = 0.610mV Zero Scale Error (ZSE) The output voltage when the DAC is loaded with all zeros. Since this is a single supply part this value cannot be less than 0V. Integral Nonlinearity (INL) End-point INL is the maximum deviation from a straight line passing through the end points of the DAC transfer curve. Because the part operates from a single supply and the output cannot go below 0, the linearity is measured between full scale and the code corresponding to the maximum offset specification. The INL error at a given input code is calculated as follows : INL = [VOUT - VOS - (VFS - VOS)(Code/4095)]/LSB
DAC CODE
1446/46L F01
0V
VOUT = the output voltage of the DAC measured at the given input code Differential Nonlinearity (DNL) DNL is the difference between the measured change and the ideal 1LSB change between any two adjacent codes. The DNL error between any two codes is calculated as follows: DNL = (VOUT - LSB)/LSB VOUT = The measured voltage difference between two adjacent codes
7
LTC1446/LTC1446L
OPERATIO
Serial Interface The data on the DIN input is loaded into the shift register on the rising edge of the clock. Data is loaded as one 24bit word where the first 12 bits are for DAC A and the second 12 are for DAC B. For each 12-bit segment the MSB is loaded first. Data from the shift register is loaded into the DAC register when CS/LD is pulled high. The clock is disabled internally when CS/LD is high. Note: CLK must be low before CS/LD is pulled low to avoid an extra internal clock pulse. The buffered output of the 24-bit shift register is available on the DOUT pin which swings from GND to VCC. Multiple LTC1446/LTC1446L's may be daisy-chained together by connecting the DOUT pin to the DIN pin of the next chip, while the clock and CS/LD signals remain common to all chips in the daisy chain. The serial data is clocked to all of the chips, then the CS/LD signal is pulled high to update all of them simultaneously.
8
U
Voltage Output The LTC1446/LTC1446L include an internal voltage reference which is connected to each DAC. The LTC1446 has a full scale of 4.095V making 1LSB equal to 1mV. The LTC1446L has a full scale of 2.5V making 1LSB equal to 0.61mV. The LTC1446/LTC1446L rail-to-rail buffered outputs can source or sink 5mA when operating with a 5V supply while pulling to within 300mV of the positive supply voltage or ground. The outputs swing to within a few millivolts of either supply rail when unloaded and have an equivalent output resistance of 40 when driving a load to the rails. The buffer amplifiers can drive 1000pF without going into oscillation.
LTC1446/LTC1446L
TYPICAL APPLICATIONS N
This circuit shows how to use an LTC1446 and an LT (R)1077 to make a wide bipolar output swing 12-bit DAC with an offset that can be digitally programmed. VOUT A, which can be set by loading the appropriate digital code for DAC A, sets the offset. As this value changes, the transfer curve for the output moves up and down as illustrated in the graph below.
A Wide Swing, Bipolar Output DAC with Digitally Controlled Offset
5V
P CS/LD
VOUT 4.094
U
0.1F CLK VOUT B 50k DIN LTC1446 GND 100k VCC 15V
+
LT1077 VOUT = 2 (VOUT B - VOUT A)
-
-15V 50k 100k
DOUT
VOUT A
8.190 A
B 0 C -4.096 A: VOUT A 0V B: VOUT A 2.048V C: VOUT A 4.095V DIN
-8.190
1446/46L F02
9
LTC1446/LTC1446L
TYPICAL APPLICATIONS N
This circuit shows how to use one LTC1446 to make an autoranging ADC. The microprocessor sets the reference span and the Common pin for the analog input by loading the appropriate digital code into the LTC1446. VOUT A controls the Common pin for the analog inputs to the LTC1296 and VOUT B controls the reference span by setting the REF + pin on the LTC1296. The LTC1296 has a Shutdown pin that goes low in shutdown mode. This will turn off the PNP transistor supplying power to the LTC1446. The resistor and capacitor on the LTC1446 outputs act as a lowpass filter for noise.
P
10
U
An Autoranging 8-Channel ADC with Shutdown
22F
+
5V VCC CS DOUT CLK DIN LTC1296 CH7 COM SSO REF + REF - CH0 8 ANALOG INPUT CHANNELS 74HC04 50k 50k 5V 0.1F 100 0.1F DIN CS/LD VCC LTC1446 GND 100 DOUT VOUT A
1446/46L F03
CLK
VOUT B
0.1F
LTC1446/LTC1446L
PACKAGE DESCRIPTION
0.300 - 0.325 (7.620 - 8.255)
0.009 - 0.015 (0.229 - 0.381)
(
+0.025 0.325 -0.015 +0.635 8.255 -0.381
)
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP
0.016 - 0.050 0.406 - 1.270 *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
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.
U
Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead PDIP (Narrow 0.300) (LTC DWG# 05-08-1510)
0.400* (10.160) MAX 8 7 6 5
0.255 0.015* (6.477 0.381)
1
2
3
4 0.130 0.005 (3.302 0.127)
0.045 - 0.065 (1.143 - 1.651)
0.065 (1.651) TYP 0.005 (0.127) MIN 0.100 0.010 (2.540 0.254) 0.125 (3.175) MIN 0.018 0.003 (0.457 0.076) 0.015 (0.380) MIN
N8 0695
S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610)
0.189 - 0.197* (4.801 - 5.004) 8 7 6 5
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
1
2
3
4
0.053 - 0.069 (1.346 - 1.752)
0.004 - 0.010 (0.101 - 0.254)
0.014 - 0.019 (0.355 - 0.483)
0.050 (1.270) BSC
SO8 0695
11
LTC1446/LTC1446L
RELATED PARTS
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LTC1452 LTC1453
Single Rail-to-Rail 12-Bit VOUT Mulitplying DAC, VCC: 2.7V to 5.5V Low Power, Mulitplying VOUT DAC with Rail-to-Rail Buffer Amplifier in SO-8 Package Single Rail-to-Rail 12-Bit VOUT DAC, Full Scale: 2.5V, VCC: 2.7V to 5.5V 3V, Low Power, Complete VOUT DAC in SO-8 Package LTC1454: VCC = 4.5V to 5.5V, VOUT = 0V to 4.095V LTC1454L: VCC = 2.7V to 5.5V, VOUT = 0V to 2.5V Low Power, Complete VOUT DAC in SO-8 Package with Clear Pin LTC1458: VCC = 4.5V to 5.5V, VOUT = 0V to 4.095V LTC1458L: VCC = 2.7V to 5.5V, VOUT = 0V to 2.5V
LTC1454/LTC1454L Dual 12-Bit VOUT DACs in a 16-Lead SO Package with Added Functionality LTC1456 Single Rail-to-Rail Output 12-Bit DAC with Clear Pin Full Scale: 4.095V, VCC: 4.5V to 5.5V
LTC1458/LTC1458L Quad 12-Bit VOUT DACs in 28-Lead SW and SSOP Packages
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
LT/GP 1096 7K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1996

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