6 db Differential Line Receiver

Transcription

1 a FEATURES High Common-Mode Rejection DC: 9 db typ Hz: 9 db typ khz: 8 db typ Ultralow THD:.% khz Fast Slew Rate: V/ s typ Wide Bandwidth: 7 MHz typ (G = /) Two Gain Levels Available: G = / or Low Cost FUNCTIONAL BLOCK DIAGRAM kω kω db Differential Line Receiver SSM SSM Ω Ω SENSE V+ V REFERENCE PIN CONNECTIONS GENERAL DESCRIPTION The SSM is an integrated differential amplifier intended to receive balanced line inputs in audio applications requiring a high level of immunity from common-mode noise. The device provides a typical 9 db of common-mode rejection (CMR), which is achieved by laser trimming of resistances to better than.%. Additional features of the device include a slew rate of V/µs and wide bandwidth. Total harmonic distortion (THD) is less than.% over the full audio band, even while driving low impedance loads. The SSM input stage is designed to handle input signals as large as +8 dbu at G = /. Although primarily intended for G = / applications, a gain of can be realized by reversing the / and SENSE/REFERENCE connections. When configured for a gain of /, the SSM and SSM Balanced Line Driver provide a fully integrated, unity gain solution to driving audio signals over long cable runs. For similar performance with G =, see SSM. Epoxy Mini-DIP (P Suffix) and SOIC (S Suffix) REF V SSM 7 V+ TOP VIEW (NOT TO SCALE) VOUT OP-8 SENSE NC = NO CONNECT 8 NC Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9, Norwood, MA -9, U.S.A. Tel: 7/9-7 Fax: 78/-

2 SSM* PRODUCT PAGE QUICK LINKS Last Content Update: //7 COMPARABLE PARTS View a parametric search of comparable parts. DOCUMENTATION Application Notes AN-: The Alexander Current-Feedback Audio Power Amplifier AN-9: Keys to Longer Life for CMOS AN-98: Digital and Analog Measurement Units for Digital CMOS Microphone Preamplifier ASICs Data Sheet SSM: - db Differential Line Receiver Data Sheet REFERENCE MATERIALS Informational Advantiv Advanced TV Solutions DESIGN RESOURCES SSM Material Declaration PCN-PDN Information Quality And Reliability Symbols and Footprints DISCUSSIONS View all SSM EngineerZone Discussions. SAMPLE AND BUY Visit the product page to see pricing options. TECHNICAL SUPPORT Submit a technical question or find your regional support number. DOCUMENT FEEDBACK Submit feedback for this data sheet. This page is dynamically generated by Analog Devices, Inc., and inserted into this data sheet. A dynamic change to the content on this page will not trigger a change to either the revision number or the content of the product data sheet. This dynamic page may be frequently modified.

3 SSM SPECIFICATIONS Parameter Symbol Conditions Min Typ Max Units AUDIO PERFORMANCE Total Harmonic Distortion Plus Noise THD+N V IN = V rms, R L = kω, f = khz. % Signal-to-Noise Ratio SNR dbu =.77 V rms, khz BW, RTI 7. dbu Headroom HR Clip Point = % THD+N +8. dbu DYNAMIC RESPONSE Slew Rate SR R L = kω, C L = pf V/µs Small Signal Bandwidth BW db R L = kω, C L = pf G = / 7 MHz G =. MHz INPUT Input Offset Voltage V IOS V CM = V, RTI, G =.. +. mv Common-Mode Rejection CMR V CM = ± V, RTO f = dc 7 9 db f = Hz 9 db f = khz 8 db f = khz db Power Supply Rejection PSR V S = ± V to ±8 V 9 db Input Voltage Range IVR Common Mode ± V Differential ±8 V OUTPUT Output Voltage Swing V O R L = kω ± ± V Minimum Resistive Load Drive kω Maximum Capacitive Load Drive pf Short Circuit Current Limit I SC +, ma GAIN Gain Accuracy... % REFERENCE INPUT Input Resistance 8 kω Voltage Range ± V POWER SUPPLY Supply Voltage Range V S ± ±8 V Supply Current I SY V CM = V, R L = ±.7 ±. ma Specifications subject to change without notice. (V S = V, C T A +8 C, G = /, unless otherwise noted. Typical specifications apply at T A = + C) ABSOLUTE MAXIMUM RATINGS Supply Voltage ±8 V Common-Mode Input Voltage ± V Differential Input Voltage ± V Output Short Circuit Duration Continuous Operating Temperature Range C to +8 C Storage Temperature Range C to + C Junction Temperature (T J ) C Lead Temperature (Soldering, sec) C Thermal Resistance 8-Pin Plastic DIP (P): θ JA =, θ JC = C/W 8-Pin SOIC (S): θ JA =, θ JC = C/W

4 SSM µs 9 9 % % mv V µs Figure. Small-Signal Transient Response (V IN = ± mv, G = /, R L = kω, V S = ± V, ) Figure. Large Signal Transient Response (V IN = + dbu, G = /, R L = kω V S = ± V, ) Figure. THD+N vs. Frequency (V S = ± V, V IN = V rms, with 8 khz Filter) Figure. Headroom (V S = ± V, R L = kω, with 8 khz Filter).. THD+N %... k k LOAD RESISTANCE Ω k Figure. Dynamic Intermodulation Distortion, DIM- (V S = ± V, R L = kω) Figure. THD+N vs. Load (V S = ± V, V IN = V rms, with khz Sine, 8 khz Filter)

5 POWER SUPPLY REJECTION db OUTPUT IMPEDANCE Ω PHASE Degrees COMMON-MODE REJECTION db CLOSED-LOOP GAIN db SSM Figure 7. Closed-Loop Gain vs. Frequency, Hz to khz (Gain of / Normalized to db) k k k Figure 8. Closed-Loop Gain vs. Frequency, Hz to MHz M M 8 R L = kω k k k M M Figure 9. Closed-Loop Phase vs. Frequency k k k M Figure. Common-Mode Rejection vs. Frequency 8 8 PSRR +PSRR k k k M Figure. Power Supply Rejection vs. Frequency k k k M Figure. Closed-Loop Output Impedance vs. Frequency

6 VOLTAGE NOISE DENSITY nv/ Hz OUTPUT VOLTAGE SWING V rms SSM G = / R L = kω OUTPUT VOLTAGE SWING V rms.v.v 7.V.V.V k k k M M Figure. Output Voltage Swing vs. Frequency V k k LOAD RESISTANCE Ω Figure. Output Voltage Swing vs. Load Resistance OUTPUT VOLTAGE SWING V p p T = + C A 8 ± ± ± ± SUPPLY VOLTAGE Figure. Output Voltage Swing vs. Supply Voltage k k Figure. Voltage Noise Density vs. Frequency 9 s 9 ms % mv.µv V.µV Figure 7. Low Frequency Voltage Noise from. Hz to Hz* µv V µv % mv Figure 8. Voltage Noise from khz to khz* *The photographs in Figure 7 through Figure 9 were taken at V S = ± V and, using an external amplifier with a gain of.

7 SUPPLY CURRENT ma SSM ms R L = kω 9 µv V µv SLEW RATE V/µs 8 % mv Figure 9. Voltage Noise from khz to khz* 7 TEMPERATURE C Figure. Slew Rate vs. Temperature. GAIN ERROR %.8... V IN = ±V R S = Ω INPUT OFFSET VOLTAGE µv V = ±V S 7 TEMPERATURE C Figure. Gain Error vs. Temperature 7 TEMPERATURE C Figure. Input Offset Voltage vs. Temperature V = ±V S.. SUPPLY CURRENT ma TEMPERATURE C Figure. Supply Current vs. Temperature. ± ± ± ± SUPPLY VOLTAGE V Figure. Supply Current vs. Supply Voltage *The photographs in Figure 7 through Figure 9 were taken at V S = ± V and, using an external amplifier with a gain of.

8 SSM APPLICATIONS INFORMATION The SSM is designed as a balanced differential line receiver. It uses a high speed, low noise audio amplifier with four precision thin-film resistors to maintain excellent common-mode rejection and ultralow THD. Figure shows the basic differential receiver application where the SSM yields a gain of /. The placement of the input and feedback resistors can be switched to achieve a gain of +, as shown in Figure. For either circuit configuration, the SSM can also be used unbalanced by grounding one of the inputs. In applications requiring a gain of +, use the SSM. +V.µF +V.µF Setting R to Ω results in the CMRR of 7 db, as stated above. To achieve the SSM s CMRR of 9 db, the resistor mismatch can be at most.7 Ω. In other words, to build this circuit discretely, the resistors would have to be matched to better than.%! The following table shows typical resistor accuracies and the resulting CMRR for a differential amplifier. % Mismatch CMRR % db % db.% db.% 9 db k k 7 SSM V +.µf A = V Figure. Standard Configuration for Gain of / 7 7 SSM V k k.µf A = V CMRR The internal thin-film resistors are precisely trimmed to achieve a CMRR of 9 db. Any imbalances introduced by the external circuitry will cause a significant reduction in the overall CMRR performance. For example, a Ω source imbalance will result in a CMRR of 7 db at dc. This is also true for any reactive source impedances that may affect the CMRR over the audio frequency range. These error sources need to be minimized to maintain the excellent CMRR. To quantify the required accuracy of the thin film resistor matching, the source of CMRR error can be analyzed. A resistor mismatch can be modelled as shown in Figure 7. By assuming a tolerance on one of the kω resistors of R, the equation for the common-mode gain becomes: which reduces to: = V IN +k k + R + k + R V IN / R = k + R This gain error leads to a common-mode rejection ratio of: CMRR = A DM A CM 8k R k + R k Figure. Reversing the Resistors Results in a Gain of CMRR = 8k R Figure 7. A Small Mismatch in Resistance Results in a Large Common-Mode Error DC OUTPUT LEVEL ADJUST The reference node of the SSM is normally connected to ground. However, it can be used to null out any dc offsets in the system or to introduce a dc reference level other than ground. As shown in Figure 8, the reference node needs to be k k +V.µF 7 SSM V.µF +V V OP7 REFERENCE Figure 8. A Low Impedance Buffer Is Required to Adjust the Reference Voltage. buffered with an op amp to maintain very low impedance to achieve high CMRR. The same reasoning as above applies such that the kω resistor has to be matched to better than.% or. Ω. The op amp maintains very low output impedance over the entire audio frequency range, as long as its bandwidth is well above khz. The reference input can be adjusted over a ± V range. The gain from the reference to the output is unity so the resulting dc output adjustment range is also ± V. INPUT ERRORS The main dc input offset error specified for the SSM is the Input Offset Voltage. The Input Bias Current and Input Offset Current are not specified as for a normal operational amplifier. Because the SSM has built-in resistors, any bias current related errors are converted into offset voltage errors. Thus, the offset voltage specification is a combination of the amplifier s offset voltage plus its offset current times the input impedance. V IN +8V SSM 8 7 8V ALL CABLE MEASUREMENTS USE BELDEN CABLE ('). +8V.µF 7 SSM 8V.µF Figure 9. SSM/SSM Balanced Line Driver/ Receiver System

9 SSM LINE DRIVER/RECEIVER SYSTEM The SSM and SSM provide a fully integrated line driver/ receiver system. The SSM is a high performance balanced line driver IC that converts an unbalanced input into a balanced output signal. It can drive large capacitive loads on long cables making it ideal for transmitting balanced audio signals. When combined with an SSM on the receiving end of the cable, the system maintains high common-mode rejection and ultralow THD. The SSM is designed with a gain of + and the SSM with a gain of /, providing an overall system gain of unity. The following data demonstrates the typical performance of the two parts together, measured on an Audio Precision at the SSM s output. This configuration was tested with feet of cable between the ICs as well as no cable. The combination of the two parts results in excellent THD+N and SNR and a noise floor of typically db over a Hz to khz bandwidth. A comment on SSM/SSM system headroom is necessary. Figure shows a maximum signal handling of approximately ± dbu, but it must be kept in mind that this is measured between the SSM s input and SSM s output, which has been attenuated by one half. Normally, the system would be shown as actually used in a piece of equipment, whereby the SSM is at the input and SSM at the output. In this case, the system could handle differential signals in excess of + dbu at the input and output, which is consistent with headroom requirements of most professional audio equipment. ' CABLE NO CABLE Figure. THD+N vs. Frequency of SSM/SSM System (V S = ±8 V, V IN = V rms, with 8 khz Filter) Figure. SSM/SSM System Frequency Response (V S = ±8 V, V IN = dbv, ' Cable) V 9 Figure. SSM/SSM System Headroom See Text (V S = ±8 V, R L = kω, ' Cable) ' CABLE % µs Figure. SSM/SSM System Large Signal Pulse Response (V S = ±8 V, R L = kω, No Cable) PRINTED IN U.S.A. NO CABLE Figure. SSM/SSM System DIM- Dynamic Intermodulation Distortion (V S = ±8 V, R L = kω) 8

10 SSM OUTLINE DIMENSIONS. (.). (9.7). (9.). (.) MAX. (.8). (.). (.9). (.).8 (.). (.) 8. (.) BSC.8 (7.). (.). (.). (.8) MIN SEATING PLANE. (.) MIN. (.) MAX. (.8) GAUGE PLANE. (8.). (7.87). (7.). (.9) MAX.9 (.9). (.). (.9). (.). (.).8 (.).7 (.78). (.). (.) COMPLIANT TO JEDEC STANDARDS MS- CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS. Figure. 8-Lead Plastic Dual In-Line Package [PDIP] Narrow Body (N-8) Dimensions shown in inches and (millimeters) 7-A. (.98).8 (.89). (.7).8 (.97) 8. (.).8 (.8). (.98). (.) COPLANARITY. SEATING PLANE.7 (.) BSC.7 (.88). (.). (.). (.) 8. (.98).7 (.7). (.9). (.99).7 (.). (.7) COMPLIANT TO JEDEC STANDARDS MS--AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) 7-A 9

11 SSM ORDERING GUIDE Model Temperature Range Package Description Package Option SSMPZ C to +8 C 8-Lead PDIP N-8 SSMSZ C to +8 C 8-Lead SOIC_N R-8 SSMSZ-REEL C to +8 C 8-Lead SOIC_N R-8 Z = RoHS Compliant Part REVISION HISTORY / Rev. to Rev. A Updated Outline Dimensions... 9 Changes to Ordering Guide... /9 Revision : Initial Version 99 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D--/(A)