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LM12454 Datasheet(PDF) 8 Page - Texas Instruments |
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LM12454 Datasheet(HTML) 8 Page - Texas Instruments |
8 / 45 page ![]() LM12454, LM12458, LM12H458 SNAS079A – MAY 2004 – REVISED FEBRUARY 2006 www.ti.com Converter AC Characteristics (1) (2) (3) (4) The following specifications apply to the LM12454, LM12458, and LM12H458 for VA+ = VD+ = 5V, VREF+ = 5V, VREF− = 0V, 12- bit + sign conversion mode, fCLK = 8.0 MHz (LM12H458) or fCLK = 5.0 MHz (LM12454/8), RS = 25Ω, source impedance for VREF+ and VREF− ≤ 25Ω, fully-differential input with fixed 2.5V common-mode voltage, and minimum acquisition time unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25°C. Symbol Parameter Conditions Typical (5) Limits (6) Units % Clock Duty Cycle 50 40 % (min) 60 % (max) 13-Bit Resolution, Sequencer State 44 (tCLK) 44 (tCLK) + 50 ns (max) S5 (Figure 14) tC Conversion Time 9-Bit Resolution, Sequencer State S5 21 (tCLK) 21 (tCLK) + 50 ns (max) (Figure 14) Sequencer State S7 (Figure 14) Built- 9 (tCLK) 9 (tCLK) + 50 ns (max) in minimum for 13-Bits tA Acquisition Time Built-in minimum for 9-Bits and 2 (tCLK) 2 (tCLK) + 50 ns (max) “Watchdog” mode tZ Auto-Zero Time Sequencer State S2 (Figure 14) 76 (tCLK) 76 (tCLK) + 50 ns (max) tCAL 4944 (tCLK) + 50 Full Calibration Time Sequencer State S2 (Figure 14) 4944 (tCLK) (max) ns 89 88 kHz (min) Throughput Rate (7) LM12H458 142 140 kHz (min) “Watchdog” Mode Comparison Time Sequencer States S6, S4, and S5 tWD 11 (tCLK) 11 (tCLK) + 50 ns (max) (Figure 14) VIN = ±5V fIN = 1 kHz 77.5 dB DSNR Differential Signal-to-Noise Ratio fIN = 20 kHz 75.2 dB fIN = 40 kHz 74.7 dB VIN = 5 Vp-p fIN = 1 kHz 69.8 dB SESNR Single-Ended Signal-to-Noise Ratio fIN = 20 kHz 69.2 dB fIN = 40 kHz 66.6 dB VIN = ±5V fIN = 1 kHz 76.9 dB Differential Signal-to-Noise + DSINAD Distortion Ratio fIN = 20 kHz 73.9 dB fIN = 40 kHz 70.7 dB VIN = 5 Vp-p fIN = 1 kHz 69.4 dB Single-Ended Signal-to-Noise + SESINAD Distortion Ratio fIN = 20 kHz 68.3 dB fIN = 40 kHz 65.7 dB (1) Two on-chip diodes are tied to each analog input through a series resistor, as shown below. Input voltage magnitude up to 5V above VA+ or 5V below GND will not damage the LM12454 or the LM12(H)458. However, errors in the A/D conversion can occur if these diodes are forward biased by more than 100 mV. As an example, if VA+ is 4.5 VDC, full-scale input voltage must be ≤4.6 VDC to ensure accurate conversions. (2) VA+ and VD+ must be connected together to the same power supply voltage and bypassed with separate capacitors at each V + pin to assure conversion/comparison accuracy. (3) Accuracy is guaranteed when operating at fCLK = 5 MHz for the LM12454/8 and fCLK = 8 MHz for the LM12H458. (4) With the test condition for VREF (VREF+ − VREF−) given as +5V, the 12-bit LSB is 1.22 mV and the 8-bit/“Watchdog” LSB is 19.53 mV. (5) Typical figures are at TA = 25°C and represent most likely parametric norm. (6) Limits are to AOQL (Average Output Quality Level). (7) The Throughput Rate is for a single instruction repeated continuously. Sequencer states 0 (1 clock cycle), 1 (1 clock cycle), 7 (9 clock cycles) and 5 (44 clock cycles) are used (see Figure 14). One additional clock cycle is used to read the conversion result stored in the FIFO, for a total of 56 clock cycles per conversion. The Throughput Rate is fCLK (MHz)/N, where N is the number of clock cycles/conversion. 8 Submit Documentation Feedback Copyright © 2004–2006, Texas Instruments Incorporated Product Folder Links: LM12454 LM12458 LM12H458 |
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