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| INTEGRATED CIRCUITS LF398 Sample-and-hold amplifier Product data Replaces LF198/LF298/LF398 of 1994 Aug 31 IC11 2001 Aug 03 Philips Semiconductors Philips Semiconductors Product data Sample-and-hold amplifier LF398 DESCRIPTION The LF398 is a monolithic sample-and-hold circuit which utilizes high-voltage ion-implant JFET technology to obtain ultra-high DC accuracy with fast acquisition of signal and low droop rate. Operating as a unity gain follower, DC gain accuracy is 0.002% typical and acquisition time is as low as 6 s to 0.01%. A bipolar input stage is used to achieve low offset voltage and wide bandwidth. Input offset adjust is accomplished with a single pin and does not degrade input offset drift. The wide bandwidth allows the LF398 to be included inside the feedback loop of 1 MHz op amps without having stability problems. Input impedance of 1010 allows high source impedances to be used without degrading accuracy. P-channel junction FETs are combined with bipolar devices in the output amplifier to give droop rates as low as 5 mV/min with a 1 F hold capacitor. The JFETs have much lower noise than MOS devices used in previous designs and do not exhibit high temperature instabilities. The overall design guarantees no feedthrough from input to output in the hold mode even for input signals equal to the supply voltages. Logic inputs are fully differential with low input current, allowing direct connection to TTL, PMOS, and CMOS; differential threshold is 1.4 V. The LF398 will operate from 5 V to 18 V supplies. It is available in 8-pin plastic DIP and 14-pin plastic SO packages. PIN CONFIGURATIONS N Package 1 2 3 4 TOP VIEW 8 7 6 5 V+ OFFSET VOLTAGE INPUT V- LOGIC LOGIC REFERENCE Ch OUTPUT D Package INPUT 1 NC 2 V- 3 NC 4 NC 5 NC 6 OUTPUT 7 TOP VIEW 14 V OS Adj 13 NC 12 V+ 11 LOGIC 10 LOGIC REF 9 8 NC Ch FEATURES * Operates from 5 V to 18 V supplies * Less than 10 s acquisition time * TTL, PMOS, CMOS compatible logic input * 0.5 mV typical hold step at CH = 0.01 F * Low input offset * 0.002% gain accuracy * Low output noise in hold mode * Input characteristics do not change during hold mode * High supply rejection ratio in sample or hold * Wide bandwidth ORDERING INFORMATION DESCRIPTION 14-Pin Plastic Small Outline (SO) Package 8-Pin Plastic Dual In-Line Package (DIP) SL00083 Figure 1. Pin Configurations APPLICATION * The LF398 is ideally suited for a wide variety of sample-and-hold applications, including data acquisition, analog-to-digital conversion, synchronous demodulation, and automatic test setup. TEMPERATURE RANGE 0 to +70C 0 to +70C ORDER CODE LF398D LF398N DWG # SOT108-1 SOT97-1 2001 Aug 03 2 853-0135 26832 Philips Semiconductors Product data Sample-and-hold amplifier LF398 FUNCTIONAL DIAGRAM OFFSET TYPICAL APPLICATIONS V+ 30 k - + 3 INPUT 8 LOGIC LOGIC 7 REFERENCE 6 HOLD CAPACITOR 300 SAMPLE 5 V HOLD 0 V LOGIC INPUT 8 7 ANALOG INPUT 3 S/H 5 OUTPUT 1 4 5 6 Ch OUTPUT V- SL00084 SL00085 Figure 2. Functional Diagram Figure 3. Typical Applications ABSOLUTE MAXIMUM RATINGS SYMBOL VS Supply voltage Maximum power dissipation Tamb = 25 C (still-air)3 N package D package Tamb Tstg VIN Operating ambient temperature range Storage temperature range Input voltage Logic-to-logic reference differential voltage2 Output short-circuit duration Hold capacitor short-circuit duration TSOLD Lead soldering temperature (10 sec max) PARAMETER RATING 18 UNIT V 1160 1040 0 to +70 -65 to +150 Equal to supply voltage +7, -30 Indefinite 10 230 mW mW C C V sec C NOTES: 1. The maximum junction temperature of the LF398 is 150 C. When operating at elevated ambient temperature, the packages must be derated based on the thermal resistance specified. 2. Although the differential voltage may not exceed the limits given, the common-mode voltage on the logic pins must always be at least 2V below the positive supply and 3 V above the negative supply. 3. Derate above 25 C, at the following rates: N package at 9.3 mW/C D package at 8.3 mW/C 2001 Aug 03 3 Philips Semiconductors Product data Sample-and-hold amplifier LF398 DC ELECTRICAL CHARACTERISTICS Unless otherwise specified, the following conditions apply: unit is in "sample" mode; VS = 15 V; Tj = 25 C; -11.5 V3 VIN +11.5 V; CH = 0.01 F; and RL = 10 k. Logic reference voltage = 0 V and logic voltage = 2.5 V. SYMBOL VOS IBIAS PARAMETER In ut Input offset voltage4 In ut Input bias current4 Input impedance Gain error Feedthrough attenuation ratio at 1 kHz Output im edance Out ut impedance "HOLD" step2 ICC Supply current4 Logic and logic reference input current Leakage current into hold capacitor4 tAC Acquisition time to 0.1% 0 1% Hold capacitor charging current Supply voltage rejection ratio Differential logic threshold TEST CONDITIONS Tj = 25 C Full temperature range Tj = 25 C Full temperature range Tj = 25 C Tj = 25 C, RL=10 k Full temperature range Tj = 25 C, Ch = 0.01 F Tj = 25 C, "HOLD" mode Full temperature range Tj = 25 C, Ch = 0.01 F, VOUT = 0 V Tj 25 C Tj = 25 C Tj = 25 C, "HOLD" mode VOUT = 10 V, Ch = 1000 pF Ch = 0.01 F VIN-VOUT = 2 V VOUT = 0 V Tj = 25 C 80 0.8 1.0 4.5 2 30 4 20 5 110 1.4 2.4 80 90 0.5 4 6 2.5 6.5 10 200 Min Typ 2 10 1010 0.004 0.01 0.02 % dB mV mA A pA s mA dB V Max 7 10 50 100 UNIT mV nA NOTES: 1. Unless otherwise specified, the following conditions apply. Unit is in "sample" mode, VS = 15 V, Tj = 25 C, -11.5 V VIN +11.5 V, Ch = 0.01 F, and RL = 10 k. Logic reference voltage = 0 V and logic voltage = 2.5 V. 2. Hold step is sensitive to stray capacitive coupling between input logic signals and the hold capacitor. 1 pF, for instance, will create an additional 0.5 mV step with a 5 V logic swing and a 0.01 F hold capacitor. Magnitude of the hold step is inversely proportional to hold capacitor value. 3. Leakage current is measured at a junction temperature of 25 C. The effects of junction temperature rise due to power dissipation or elevated ambient can be calculated by doubling the 25 C value for each 11 C increase in chip temperature. Leakage is guaranteed over full input signal range. 4. The parameters are guaranteed over a supply voltage of 5 to 18 V. 2001 Aug 03 4 Philips Semiconductors Product data Sample-and-hold amplifier LF398 TYPICAL DC PERFORMANCE CHARACTERISTICS Input Bias Current 25 20 15 CURRENT (mA) 10 5 0 -5 -10 -15 -50 -25 0 25 50 75 100 125 150 CURRENT (mA) 20 18 16 14 12 10 8 6 4 2 0 -50 -25 0 25 50 75 100 125 150 SINKING SOURCING Output Short Circuit Current INPUT VOLTAGE -- OUTPUT VOLTAGE (mV) 1 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1 -15 -10 Gain Error Tj = 25 C RL = 10 k SAMPLE MODE -5 0 5 10 15 JUNCTION TEMPERATURE (C) JUNCTION TEMPERATURE (C) INPUT VOLTAGE (V) Hold Step 100 V+ = V- = 15 V Tj = 25 C 10 HOLD STEP (mV) CURRENT (nA) 10 100 Leakage Current Into Hold Capacitor 2 VS = 15 V VOUT = 0 V HOLD MODE NORMALIZED HOLD STEP AMPLITUDE 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 -25 0 25 50 75 100 125 150 -15 Hold Step Input Voltage Tj = 100 C 1 1 Tj = 25 C 0.1 10-1 Tj = 55 C 0.01 100 pF 1000 pF 0.01 F 0.1 F 1 F 10-2 -50 -10 -5 0 5 10 15 HOLD CAPACITOR JUNCTION TEMPERATURE (C) INPUT VOLTAGE (V) SL00086 Figure 4. Typical DC Performance Characteristics TYPICAL AC PERFORMANCE CHARACTERISTICS Acquisition Time 1 VIN = 0 V to 10 V 1% 10 TIME ( s) Tj = 25 C 250 V+ = V- = 15 V 225 200 TIME (ns) 0.1% 175 150 125 100 75 50 25 1000 0.001 0.01 HOLD CAPACITOR (F) 0.1 0 -50 -25 0 25 50 POSITIVE INPUT STEP 0.1 75 100 125 150 0.1 1 10 100 1 MYLAR TIME CONSTANT POLYPROPYLENE AND POLYSTYRENE HYSTERESIS Aperture Time 100 Capacitor Hysteresis MYLAR HYSTERESIS POLYPROPYLENE AND POLYSTYRENE TIME CONSTANT VOUT 1 mV VIN = 10 V NEGATIVE INPUT STEP 10 0.01% 100 JUNCTION TEMPERATURE (C) SAMPLE TIME (ms) SL00087 Figure 5. Typical AC Performance Characteristics 2001 Aug 03 5 Philips Semiconductors Product data Sample-and-hold amplifier LF398 TYPICAL AC PERFORMANCE CHARACTERISTICS (Continued) Dynamic Sampling Error 100 10 0 Output Droop Rate 2 1.8 `Hold' Sampling Time 330 pF V+ = V- = 15 V SETTLING TIME 10 V/ T (V/SEC) ERROR (mV) 330 pF 1 10-1 TIME ( s) 1 F Tj = 85 C 10-2 Tj = 25 C 10-3 1000 pF 10-4 0.1 1 10 100 1000 100 pF 1000 pF 0.01 F 0.1 F INPUT SLEW RATE (V/ms) HOLD CAPACITOR 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 -10 -100 0 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (C) Phase And Gain (Input to Output, Small-Signal) 5 Ch = 0 GAIN -- INPUT TO OUTPUT (dB) 0 -5 -10 Ch = 1000 pF Ch 0.01 F Ch = 1000 pF Ch = 0.01 F 80 70 60 50 40 30 20 10 Ch = 0 0 1k 10k 100k 1M 10M 160 140 REJECTION RATIO (dB) 120 100 80 60 40 20 INPUT TO OUTPUT PHASE DELAY ( o ) Power Supply Rejection 160 Tj = 25 C V+ = V- = 15 V VOUT = 0 C NOISE (nV/ Hz) 140 120 100 Output Noise POSITIVE MODE NEGATIVE MODE `HOLD' MODE 80 60 40 20 0 SAMPLE MODE Ch 0.01 F 0 100 1k 10k 100k 1M 10 100 1k 10k 100k FREQUENCY (Hz) FREQUENCY (Hz) FREQUENCY (Hz) Feedthrough Rejection Ratio (Hold Mode) -130 V+ = V- = 15 V -120 -110 RATIO (dB) -100 -90 -80 Ch = 1000 pF -70 -60 -50 10 100 100 1k 10k 100k 1M FREQUENCY (Hz) Ch = 0.01 F Ch = 0.1 F Tj =25 C VIN = 10 Vp-p V7.8 = 0 SL00088 Figure 6. Typical AC Performance Characteristics (cont.) 2001 Aug 03 6 Philips Semiconductors Product data Sample-and-hold amplifier LF398 SO14: plastic small outline package; 14 leads; body width 3.9 mm SOT108-1 2001 Aug 03 7 Philips Semiconductors Product data Sample-and-hold amplifier LF398 DIP8: plastic dual in-line package; 8 leads (300 mil) SOT97-1 2001 Aug 03 8 Philips Semiconductors Product data Sample-and-hold amplifier LF398 NOTES 2001 Aug 03 9 Philips Semiconductors Product data Sample-and-hold amplifier LF398 Data sheet status Data sheet status [1] Objective data Preliminary data Product status [2] Development Qualification Definitions This data sheet contains data from the objective specification for product development. Philips Semiconductors reserves the right to change the specification in any manner without notice. This data sheet contains data from the preliminary specification. Supplementary data will be published at a later date. Philips Semiconductors reserves the right to change the specification without notice, in order to improve the design and supply the best possible product. This data sheet contains data from the product specification. Philips Semiconductors reserves the right to make changes at any time in order to improve the design, manufacturing and supply. Changes will be communicated according to the Customer Product/Process Change Notification (CPCN) procedure SNW-SQ-650A. Product data Production [1] Please consult the most recently issued data sheet before initiating or completing a design. [2] The product status of the device(s) described in this data sheet may have changed since this data sheet was published. The latest information is available on the Internet at URL http://www.semiconductors.philips.com. Definitions Short-form specification -- The data in a short-form specification is extracted from a full data sheet with the same type number and title. For detailed information see the relevant data sheet or data handbook. Limiting values definition -- Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 60134). Stress above one or more of the limiting values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or at any other conditions above those given in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended periods may affect device reliability. Application information -- Applications that are described herein for any of these products are for illustrative purposes only. Philips Semiconductors make no representation or warranty that such applications will be suitable for the specified use without further testing or modification. Disclaimers Life support -- These products are not designed for use in life support appliances, devices or systems where malfunction of these products can reasonably be expected to result in personal injury. Philips Semiconductors customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify Philips Semiconductors for any damages resulting from such application. Right to make changes -- Philips Semiconductors reserves the right to make changes, without notice, in the products, including circuits, standard cells, and/or software, described or contained herein in order to improve design and/or performance. Philips Semiconductors assumes no responsibility or liability for the use of any of these products, conveys no license or title under any patent, copyright, or mask work right to these products, and makes no representations or warranties that these products are free from patent, copyright, or mask work right infringement, unless otherwise specified. Contact information For additional information please visit http://www.semiconductors.philips.com. Fax: +31 40 27 24825 (c) Koninklijke Philips Electronics N.V. 2001 All rights reserved. Printed in U.S.A. Date of release: 10-01 For sales offices addresses send e-mail to: sales.addresses@www.semiconductors.philips.com. Document order number: 9397 750 08921 Philips Semiconductors 2001 Aug 03 10 |
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