LM12458 National Semiconductor, LM12458 Datasheet

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LM12458

Manufacturer Part Number
LM12458
Description
12-Bit + Sign Data Acquisition System with Self-Calibration
Manufacturer
National Semiconductor
Datasheet

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© 1999 National Semiconductor Corporation
LM12454/LM12458/LM12H458
12-Bit + Sign Data Acquisition System with
Self-Calibration
General Description
The LM12454, LM12458, and LM12H458 are highly inte-
grated Data Acquisition Systems. Operating on just 5V, they
combine a fully-differential self-calibrating (correcting linear-
ity and zero errors) 13-bit (12-bit + sign) analog-to-digital
converter (ADC) and sample-and-hold (S/H) with extensive
analog functions and digital functionality. Up to 32 consecu-
tive conversions, using two’s complement format, can be
stored in an internal 32-word (16-bit wide) FIFO data buffer.
An internal 8-word RAM can store the conversion sequence
for up to eight acquisitions through the LM12(H)458’s
eight-input multiplexer. The LM12454 has a four-channel
multiplexer, a differential multiplexer output, and a differential
S/H input. The LM12454 and LM12(H)458 can also operate
with 8-bit + sign resolution and in a supervisory “watchdog”
mode that compares an input signal against two program-
mable limits.
Programmable acquisition times and conversion rates are
possible through the use of internal clock-driven timers. The
reference voltage input can be externally generated for ab-
solute or ratiometric operation or can be derived using the in-
ternal 2.5V bandgap reference.
All registers, RAM, and FIFO are directly addressable
through the high speed microprocessor interface to either an
8-bit or 16-bit databus. The LM12454 and LM12(H)458 in-
clude a direct memory access (DMA) interface for
high-speed conversion data transfer.
An evaluation/interface board is available. Order num-
ber LM12458EVAL.
Additional applications information can be found in applica-
tions notes AN-906, AN-947 and AN-949.
TRI-STATE
AT
®
is a registered trademark of International Business Machines Corporation.
®
is a registered trademark of National Semiconductor Corporation.
DS011264
Key Specifications
(f
Features
n Three operating modes: 12-bit + sign, 8-bit + sign, and
n Single-ended or differential inputs
n Built-in Sample-and-Hold and 2.5V bandgap reference
n Instruction RAM and event sequencer
n 8-channel (LM12(H)458), 4-channel (LM12454)
n 32-word conversion FIFO
n Programmable acquisition times and conversion rates
n Self-calibration and diagnostic mode
n 8- or 16-bit wide databus dmicroprocessor or DSP
Applications
n Data Logging
n Instrumentation
n Process Control
n Energy Management
n Inertial Guidance
j
j
j
j
j
j
j
j
j
j
CLK
“watchdog”
multiplexer
interface
Resolution
13-bit conversion time
9-bit conversion time
13-bit Through-put rate
Comparison time
ILE
V
Power dissipation
Stand-by mode
Single supply
= 5 MHz; 8 MHz, H)
(“watchdog” mode)
IN
range
12-bit + sign or 8-bit + sign
30 mW, 34 mW (H) (max)
140k samples/s (H) (min)
8.8 µs, 5.5 µs (H) (max)
4.2 µs, 2.6 µs (H) (max)
88k samples/s (min),
1.4 µs (H) (max)
±
2.2 µs (max),
1 LSB (max)
www.national.com
GND to V
50 µW (typ)
3V to 5.5V
July 1999
A
+

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LM12458 Summary of contents

Page 1

... LM12454/LM12458/LM12H458 12-Bit + Sign Data Acquisition System with Self-Calibration General Description The LM12454, LM12458, and LM12H458 are highly inte- grated Data Acquisition Systems. Operating on just 5V, they combine a fully-differential self-calibrating (correcting linear- ity and zero errors) 13-bit (12-bit + sign) analog-to-digital converter (ADC) and sample-and-hold (S/H) with extensive analog functions and digital functionality consecu- tive conversions, using two’ ...

Page 2

... See NS Package Number EL44A www.national.com Guaranteed Order Part Number ± 1.0 LSB LM12H458CIV LM12H458CIVF LM12H458MEL/883 or 5962-9319502MYA ± 1.0 LSB LM12454CIV LM12458CIV LM12458CIVF Order Number LM12458CIVF or LM12H458CIVF See NS Package Number VGZ44A DS011264-2 2 See NS Package Number V44A VGZ44A EL44A V44A V44A VGZ44A DS011264-34 ...

Page 3

Functional Diagrams LM12454 LM12(H)458 3 DS011264-1 DS011264-21 www.national.com ...

Page 4

... V Package, Infrared, 15 sec. EL and W Packages, Solder, 10 sec. ESD Susceptibility (Note 5) LM12458MEL/883 Converter Characteristics The following specifications apply to the LM12454, LM12458, and LM12H458 for V = 8.0 MHz (LM12H458 12-bit + sign conversion mode, f CLK V and fully-differential input with fixed 2.5V common-mode voltage, and minimum acquisition time unless REF+ REF− ...

Page 5

... REF+ REF− C Selected Multiplexer Channel Input IN Capacitance Converter AC Characteristics The following specifications apply to the LM12454, LM12458, and LM12H458 for V = 8.0 MHz (LM12H458 12-bit + sign conversion mode, f CLK V and fully-differential input with fixed 2.5V common-mode voltage, and minimum acquisition time unless REF+ REF− ...

Page 6

... Converter AC Characteristics The following specifications apply to the LM12454, LM12458, and LM12H458 for V = 8.0 MHz (LM12H458 12-bit + sign conversion mode, f CLK V and fully-differential input with fixed 2.5V common-mode voltage, and minimum acquisition time unless REF+ REF− otherwise specified. Boldface limits apply for T ...

Page 7

... Multiplexer ON-Channel Leakage Current Multiplexer OFF-Channel Leakage Current R Multiplexer ON-Resistance ON Multiplexer Channel-to-Channel R matching ON Internal Reference Characteristics The following specifications apply to the LM12454, LM12458, and LM12H458 for Boldface limits apply for MIN Symbol Parameter V Internal Reference Output Voltage REFOUT Internal Reference Temperature ...

Page 8

... Logical “0” Output Voltage OUT(0) I TRI-STATE ® Output Leakage Current OUT Digital Timing Characteristics The following specifications apply to the LM12454, LM12458, and LM12H458 for V 100 pF on data I/O, INT and DMARQ lines unless otherwise specified. Boldface limits apply for 25˚C. other limits Symbol ...

Page 9

... Digital Timing Characteristics The following specifications apply to the LM12454, LM12458, and LM12H458 for V 100 pF on data I/O, INT and DMARQ lines unless otherwise specified. Boldface limits apply for 25˚C. other limits Symbol Parameter (See Figures High to TRI-STATE 18 RD Low to Data Valid (Access Time) ...

Page 10

Digital Timing Characteristics Note 17: The LM12(H)454/8’s self-calibration technique ensures linearity and offset errors as specified, but noise inherent in the self-calibration process will result ± repeatability uncertainty of 0.10 LSB. Note 18: The Throughput Rate is for ...

Page 11

Electrical Characteristics = 4.096V V − V REF+ REF− − IN+ IN− GND IN+ A GND IN− A FIGURE 2. Specific Case of Output Digital Code vs the Operating ...

Page 12

Electrical Characteristics = V V − V REF REF+ REF− FIGURE 3. The General Case of the V www.national.com (Continued) Operating Range REF 12 DS011264-24 ...

Page 13

Electrical Characteristics = V V − V REF REF+ REF− FIGURE 4. The Specific Case of the V (Continued) Operating Range for V REF FIGURE 5. Transfer Characteristic 13 DS011264- DS011264-4 ...

Page 14

Electrical Characteristics FIGURE 6. Simplified Error Curve vs Output Code without Auto-Calibration or Auto-Zero Cycles FIGURE 7. Simplified Error Curve vs Output Code after Auto-Calibration Cycle www.national.com (Continued) FIGURE 8. Offset or Zero Error Voltage 14 DS011264-5 DS011264-6 DS011264-7 ...

Page 15

Typical Performance Characteristics auto-calibration unless otherwise specified. The performance for 8-bit + sign and “watchdog” modes is equal to or better than shown. Linearity Error Change vs Clock Frequency DS011264-37 Linearity Error Change vs Supply Voltage DS011264-40 Full-Scale Error Change ...

Page 16

Typical Performance Characteristics auto-calibration unless otherwise specified. The performance for 8-bit + sign and “watchdog” modes is equal to or better than shown. (Continued) Zero Error Change vs Temperature DS011264-46 Analog Supply Current vs Temperature DS011264-49 V Load Regulation REFOUT ...

Page 17

Typical Dynamic Performance Characteristics mode after auto-calibration unless otherwise specified. Bipolar Signal-to-Noise Ratio vs Input Frequency DS011264-54 Bipolar Spectral Response with 1.028 kHz Sine Wave Input DS011264-57 Bipolar Spectral Response with 40 kHz Sine Wave Input DS011264-60 The following curves ...

Page 18

Typical Dynamic Performance Characteristics mode after auto-calibration unless otherwise specified. (Continued) Unipolar Signal-to-Noise + Distortion Ratio vs Input Frequency DS011264-63 Unipolar Spectral Response with 10 kHz Sine Wave Input DS011264-66 Test Circuits and Waveforms FIGURE 9. TRI-STATE Test Circuits and ...

Page 19

Timing Diagrams + = +5V Address valid to ALE low set-up time Address valid to ALE low hold time. 5: ALE pulse width 6: RD ...

Page 20

Timing Diagrams + = +5V outputs. (Continued) FIGURE 11. Non-Multiplexed Data Bus (ALE = pulse width 9: RD high to next low 11: WR pulse width 13: ...

Page 21

Pin Description Analog and digital supply voltage pins. The A D LM12(H)454/8’s supply voltage operating range is +3.0V to +5.5V. Accuracy is guaranteed only and V + are connected to the same power ...

Page 22

Application Information 1.0 Functional Description The LM12454 and LM12(H)458 are multi-functional Data Ac- quisition Systems that include a 12-bit-plus-sign self-calibrating analog-to-digital converter (ADC) with a two’s-complement output format, an 8-channel (LM12(H)458 4-channel (LM12454) analog multiplexer, an internal 2.5V ...

Page 23

Internal User-Programmable Registers (Continued) Any Instruction RAM READ or WRITE can affect the se- quencer’s operation: The Sequencer should be stopped by setting the RESET bit to a “1” resetting the START bit in the Configura- tion ...

Page 24

Internal User-Programmable Registers www.national.com (Continued) 24 ...

Page 25

Internal User-Programmable Registers Purpose Instruction RAM (RAM Pointer = 00 ...

Page 26

Internal User-Programmable Registers (Continued) Bits 12–15 are used to store the user-programmable acqui- sition time. The Sequencer keeps the internal S/H in the ac- quisition mode for a fixed number of clock cycles (nine clock cycles, for 12-bit + ...

Page 27

Internal User-Programmable Registers (Continued) mand (“1”) disconnects the external clock from the internal circuitry, decreases the LM12(H)454/8’s internal analog cir- cuitry power supply current, and preserves all internal RAM contents. After writing a “0” to the Standby bit, the ...

Page 28

Internal User-Programmable Registers (Continued) The completion of a full auto-zero self-calibration generates Interrupt 4. Interrupt 5 is generated when the Sequencer encounters an instruction that has its Pause bit (Bit 1 in Instruction RAM “00”) set to “1”. The ...

Page 29

Internal User-Programmable Registers (Continued) Bits 8–15 show the Limit # 2 status. Each bit will be set high (“1”) when the corresponding instruction’s input voltage ex- ceeds the threshold stored in the instruction’s Limit # 2 regis- ter. When, ...

Page 30

Sequencer The Sequencer uses a 3-bit counter (Instruction Pointer, or IP, in Figure retrieve the programmable conversion in- structions stored in the Instruction RAM. The 3-bit counter is reset to 000 during chip reset or if ...

Page 31

Sequencer (Continued) FIGURE 15. Sequencer Logic Flow Chart (IP = Instruction Pointer) DS011264-19 31 www.national.com ...

Page 32

Analog Considerations 5.1 REFERENCE VOLTAGE The difference in the voltages applied to the V V defines the analog input voltage span (the difference REF− between the voltages applied between two multiplexer inputs or the voltage applied to one of ...

Page 33

Application Circuits (Continued) velop both software and hardware. The board hardwires the BW (Bus Width) pin to a logic high, selecting an 8-bit wide databus. Therefore designed for an 8-bit expansion slot on the computer’s motherboard. The ...

Page 34

... Note: The layout utilizes a split ground plane. The analog ground plane is placed under all analog signals and U5 pins 1, 34–44. The remaining signals and pins are placed over the digital ground. The single point ground connection is at U6, pin 2, and this is connected to the motherboard pin B1. FIGURE 16. Schematic for the LM12(H)454/8 Evaluation Interface Board for XT and AT Style Computers, Order Number LM12458EVAL www.national.com (Continued) ...

Page 35

... C15, C17 100 µF, 50V, ceramic disk U1 MM74HCT244N U2 GAL16V8-20LNC U3 MM74HCT245N U4 MM74HCU04N U5 LM12(H)458CIV or LM12454CIV U6 LM340AT-5.0 SK1 44-pin PLCC socket A1 LM12(H)458/4 Rev Board FIGURE 17. Parts List for the LM12(H)454/8 Evaluation Interface Board for XT and AT Style Computers, Order Number LM12458EVAL 35 www.national.com ...

Page 36

Application Circuits FIGURE 18. Logic Equations Used to Program the GAL16V8 www.national.com (Continued) 36 DS011264-32 ...

Page 37

Application Circuits (Continued) FIGURE 19. GAL Functional Block Diagram FIGURE 20. Silk-Screen Layout Showing Parts Placement on the LM12(H)454/8 Evaluation/Interface Board DS011264-27 37 DS011264-31 www.national.com ...

Page 38

Application Circuits FIGURE 21. LM12(H)454/8 Evaluation/Interface Board Component-Side Layout Positive www.national.com (Continued) 38 DS011264-28 ...

Page 39

Application Circuits (Continued) FIGURE 22. LM12(H)454/8 Evaluation/Interface Board Ground-Plane Layout Negative 39 DS011264-29 www.national.com ...

Page 40

Application Circuits FIGURE 23. LM12(H)454/8 Evaluation/Interface Circuit-Side Layout Positive www.national.com (Continued) 40 DS011264-30 ...

Page 41

... Physical Dimensions inches (millimeters) unless otherwise noted Order Number LM12458MEL/883 or 5962-9319501MYA, LM12H458MEL/883 or 5962-9319502MYA NS Package Number EL44A 41 www.national.com ...

Page 42

... Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Order Number LM12454CIV, LM12458CIV or LM12H458CIV Order Number LM12H458CIVF or LM12458CIVF www.national.com NS Package Number V44A NS Package Number VGZ44A 42 ...

Page 43

... NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant ...

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