ANALOG DEVICES Quad Audio Switch S0M2404 FEATURES Clickless Bilateral Audio Switching Four SPST Switches in a 20-Pin Package Ultralow THD+N: 0.0008% @ 1 kHz (2 V rms, R, = 100 kQ) Low Charge Injection: 35 pC typ High OFF Isolation: 100 dB typ (R, = 10 k2 @ 1 kHz) Low Crosstalk: 94 dB typ (R, = 10 k2._ @ 1 kHz) Low ON Resistance: 28 2 typ Low Supply Current: 900 A typ Single or Dual Supply Operation: +11 V to +24 V or +5.5 Vto +12 V Guaranteed Break-Before-Make TTL and CMOS Compatible Logic Inputs Low Cost-Per-Switch GENERAL DESCRIPTION The SSM2404 integrates four SPST analog switches in a single 20-pin package. Developed specifically for high performance audio applications, distortion and noise are negligible over the full operating range of 20 Hz to 20 kHz. With very low charge injection of 35 pC, clickless audio switching is possible, even under the most demanding conditions. Switch control is realized by conventional TTL or CMOS logic. Guaranteed break-before-make operation assures that all switches in a large system will open before any switch reaches the ON state. Single or dual supply operation is possible. Additional features include 100 dB OFF isolation, 94 dB crosstalk and 28 Q ON resistance. Optional current-mode switching permits an extended signal-handling range. Although optimized for large load impedances, the SSM2404 maintains good audio performance even under low load impedance conditions. REV. B 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. BLOCK DIAGRAM OF ONE SWITCH CHANNEL HE CONTROLO| LOGIC INTERFACE AND |_| RAMP OsWiA BREAK-BEFORE-MAKE | | GENERATOR boo swie y Hee DIGITAL ' CONTROL V+ PIN CONNECTIONS Epoxy Mini-DIP (P Suffix) and SOIC (S Suffix) 20] SW4A 9] AGND 18] sw4B 17] V+ 16 | Sw4 CONTROL SW1A [4 . AGND [2| sw1B [se DGND [4 SW1 CONTROL | 5 F-4 cE SSM240 SW2 CONTROL [e}-4 15] SW3 CONTROL I eG} ft fay I SwW2B [sho 0-13] SW3 B AGND [9| Sw2 SW3 12] AGND SW2A [19] +4] SW3 A NC = NO CONNECT *CONNECT TO ANALOG GROUND FOR BEST NOISE ISOLATION a 8 a een Bro One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703SOM2404-SPECIFICATIONS (Vg = 12 V, Ty = +25C, unless otherwise noted. Typical specifications apply at Ta = +25C.) Parameter Symbol Conditions Min Typ Max | Units AUDIO PERFORMANCE Total Harmonic Distortion Plus Noise THD+N @ 1 kHz, with 80 kHz Filter, R, = 100 kQ, Vjqy = 2 Vrms 0.0008 % Spectral Noise Density en 20 Hz to 20 kHz 0.8 nVNHz Wideband Noise Density n P-P 20 Hz to 20 kHz 0.6 LV p-p ANALOG SIGNAL SECTION Analog Voltage Range Va Vinu = 2.4 V, I, = +2 mA +12 Vv Analog Current Range I, Ving = 2.4 .V, Va=OV +10 mA ON Resistance Ron I, = +10 mA, Va = +10 V de 28 45 Q Ron Matching Ron Match I, =+10 mA, Va=0V 1 % ON Leakage Current Iscony Va=2t10V 20 0.1 +20 nA OFF Leakage Current Is(oFF) Va=1tl10V 20 0.1 +20 nA Charge Injection Q 35 pc ON-State Input Capacitance Con V,=5 Vrms 31 pF OFF-State Input Capacitance Corr Va=5 Vrms 17 pF OFF Isolation IsocorF) Va, =50 mV rms, f = 1 kHz, Ry, = 10 kQ 100 dB Channel-to-Channel Crosstalk Cr V, = 50 mV rms, f = 1 kHz, Ry = 10 kQ 94 dB CONTROL SECTION Digital Input High Vinu DGND =0 V 2.4 Vs V Digital Input Low Vint DGND =0 V 0 0.8 Vv Turn-On Time! ton See Test Circuit 8 50 ms Turn-Off Time? torr See Test Circuit 5 30 ms Break-Before-Make Time Delay ton-topr 3 20 ms Logic Input Current Logic HI Vinu = 2.4 V 1000 1.3. +1000} nA Logic LO Vint = 0.8 V 1000 1.0 +1000} nA POWER SUPPLY Supply Voltage Range Vs Single Supply +11 +24 V Dual Supply +5.5 +12 V Positive Supply Current Isyz All Channels On 0.9 5 mA Negative Supply Current Isgy_ All Channels On -1.5 -0.6 mA Ground Current All Channels On 2.0 -0.3 mA NOTES 'Turn-on time is measured from the time the logic input reaches the 50% point to the time the output reaches 50% of the final value. ?Turn-off time is measured from the time the logic input reaches the 50% point to the time the output reaches 50% of the initial value. Specifications subject to change without notice. ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE Supply Voltage Single Supply 0.0.00... cee eee ee +27 V Operating Dual Supply .... 0.000.000 cee +13.5V Temperature Package Analog Input Voltage (Va)... 0... ee Vs Model Range Package Option* Logic Input Voltage (VintaNH) .- + ees Vs , , Maximum Current Through Any Switch ........... 20 mA SSM2404P 40C to +85C 20-Pin Plastic DIP | N-20 Operating Temperature Range ............ 40C to +85C SSM24048 | 40C to +85C_| 20-Pin SOIC R20 Storage Temperature Range ............ 65C to +150C Junction Temperature (Tj) .................00. +150C Lead Temperature (Soldering, 60 sec) ............ +300C Thermal Resistance! 20-Pin Plastic DIP (P): 0y,4 = 74, 0@j = 32 ......... C/W 20-Pin SOIC (S): Oy, = 90, @j = 27... ee C/W NOTE 9,, is specified for worst case mounting conditions, i.e., 8,4 is specified for device in socket for P-DIP package. *N = Plastic DIP, R = SOIC. REV. B90M2404 Va un) = 50MV pus f = 20Hz TO 100kHz f Yagen R, = 10kQ2 AND 100kQ Va (iny <7 502 Va cout) OFF ISOLATION = 20 LOG | Va any OFF Isolation Test Circuit HIGH Loaic / \ 1.4V tr<100ns 1.4V INPUT LOW / t;<100ns LOW DC VOLTAGE Va any CLOSED OPEN _7/50% 50%") OPEN Va out) ton torr ton/tore Timing Diagram +12V V+ Ya in) of OV, (ouT) SWITCH | CONROL I GND v- = = -12v Test Circuit for ton/tore Timing Specification, ton/torr Switching Response, and ON/OFF Transition Photos AUDIO PRECISION SSH24R4C THD+N(x) vs FREQC(H:) at 8.838 a 198 ik 18k =. 28k Figure 1. THD+N vs. Frequency (Vs =+12 V, Va =2 Vis, with 80 kHz Filter) REV. B R, = 10ka R= 100k AUDIO PRECISION SSH2404B THD+N(%) ve AMPL(Vras) 8.1 0.618 R, = 10kQ R= 100kQ 8.001 8881 - as 1 18 2 Figure 2. Headroom (Vs =+12 V, f= 1 kHz, with 80 kHz Filter) 1.0 0.1 0.01 THD +N-% 0.001 0.0001 100 1k 10k 100k LOAD RESISTANCE - Figure 3. THD+N vs. Load (Vs =+12 V, V4 =2 Vrms, f= 1 kHz, with 80 kHz Filter) 0.01 0.001 THD +N-% 0.0001 14 +8 +H12 SUPPLY VOLTAGE - V Figure 4. THD+N vs. Supply Voltage (Va = 2 V rms, f= 1 kHz, R, = 100 kQ, with 80 kHz Filter)90M2404 AUDIO PRECISION SSH24Q4E AMPL(4BV) vs FREQ(Hz) 2.0008 1.5888 1.0008 50888 8.8 ~ 5888 ~1.088 1.588 2.008 2 168 ik 16k 108k 206k Figure 5. Frequency Response (Vs =+12 V, Va = 1 Vrms, R,= 100 kQ) fol ME RUT mas) SEOUL hg GSS RN dar a SaEnaRnee tard 25kHz aes 4 BW: 150Hz Figure 6. SSM2404 Spectral Noise Density ep [5 Devices (20 Switches) Chained Together] EAs Sianeeline Input eee output ELAR Figure 7. Square Wave Response (Ta = +25C, Vg =+12 V, R, = 100 kQ, f = 20 kHz) OUTPUT VOLTAGE SWING - Vins OUTPUT VOLTAGE SWING - Vans OFF ISOLATION - dB 8 be a Nd oa Ta = 25 Vg = +12 = 20kHz 2 a 2 n < ~ a =~ a 6.0 100 1k 10k 100k LOAD RESISTANCE - Figure 8. Output Voltage Swing vs. Load Resistance 10 & o Ta = 25C Ri = 100kQ f = 20kHz 0.1% THD + N = np wo a oO o 14 +6 +8 +H10 +H12 SUPPLY VOLTAGE - Volts Figure 9. Output Voltage Swing vs. Supply Voltage | 8 | 8 & \ 8 | 8 I wl So & 4 oS So -110 -120 10 100 1k 10k 100k FREQUENCY Hz Figure 10. OFF-Isolation vs. Frequency REV. B90M2404 0 50 Ty = 25C -15 Vg = 112V < 40 30 Vy = 50MVens < I Vg =112V 2 5 30 Vinc= 0.8V S 3 Fe RL= | _60 40C TO +85C 5 20 Ss E -75 Q $ 10 Q -90 < 6 a -105 5 0 E -120 = 10 -135 -150 -20 10 100 1k 10k 100k -10 -5 0 5 10 FREQUENCY Hz ANALOG INPUT VOLTAGE - Volts Figure 11. Channel-to-Channel Crosstalk vs. Frequency Figure 14, Leakage Current vs. Analog Voltage (Worst Case Conditions, as Measured Between Switches 7 and 4, or 2 and 3) 50 40 3 E | I Ww g 30 = 7 e % g 2 2 = w 20 0 2 E 6 & 10 0 -10 5 0 5 10 40 -20 0 20 40 60 80 100 ANALOG INPUT VOLTAGE - Volts TEMPERATURE - C Figure 12. ON Resistance vs. Analog Voltage Figure 15. Switching Time vs. Temperature Vg = H2V Va = GND Vinn = 24V SWITCH LEAKAGE CURRENT - mA SUPPLY CURRENT - mA ~15 -~10 +5 0 5 10 15 40 -20 0 20 40 60 80 100 ANALOG INPUT VOLTAGE - Volts TEMPERATURE - C Figure 13. Overvoltage Characteristics Figure 16. Supply Current vs. Temperature REV. B 590M2404 ANALOG OUTPUT Va (ouT) Loaic INPUT VINL/ANH Aly CLOSED (SWITCH ON) Figure 19. Switch ON-to-OFF Transition (R, = 5 kQ) APPLICATIONS INFORMATION The SSM2404 integrates four analog CMOS switches with guaranteed break-before-make operation to provide high quality audio switching. Each switch has complementary N-channel and P-channel MOSFETs to allow the analog input voltage range to include the positive and negative rails and improve linearity. In addition, the topology permits fully bilateral switching. When using the SSM2404 there is full flexibility in configuring the switches. For example, they can be used individually as shown in Figure 20, or as a double-pole, double-throw (DPDT) switch, which is explained later. The SSM2404 can also be configured as a 4:1 multiplexer, or by using additional packages, as 8:1 or 16:1 and up. The break- before-make feature is guaranteed from part to part allowing such multiple-package applications. As Figure 20 shows, the SSM2404 is easy to use, and no ad- ditional devices are needed. The load resistors are recommended for improved OFF-isolation and charge injection. The ON resistance of the switch is only 28 Q typically, which causes very little signal attenuation even with a load resistor. VW e IN4 ft j20 +o IN4 2] swi swa |19 R= = = SR, OUT1 3 Pays 2-18 OUT4 I 1 pano 4 ! | 17 Fo s12v 1 1 SW1 CONTROL o-[s}-2 t116 Lo sW4 CONTROL SSM2404 SW2 CONTROL o{s} r15}-0 SW3 CONTROL | 7| | 1 [aa Lo -12V I I OUT2 8 13 OUT3 Ri RL 9 | swe sw3 |12 SW SWITCH = | s CONTROL] STATE IN2 o-f10] hapo IN3 0 OFF 1 ON R,_ IS OPTIONAL Figure 20. Basic Circuit Configuration OPTIMIZING PERFORMANCE As the performance curves show, the switch is optimized for high impedance loads. The distortion performance is at its best when the switch has a load impedance of 100 kQ or greater as shown in Figure 1. However, even at lower values of load resis- tances, the 1 kHz distortion performance is still excellent, 0.006% for a 10 kQ load. The main trade-off with THD is OFF-isolation and crosstalk. This is shown in Figures 10 and 11, again with two different load conditions. As these graphs show, the 10 kQ load yields approximately a 16 dB improve- ment in both characteristics. Thus, the optimum operating point depends on the most criti- cal parameters. When THD is critical then high load imped- ances should be used; however, when crosstalk and OFF- isolation are critical, lower impedances on the order of 10 kQ should be used. An additional benefit of using the smaller load resistor is that any charge injected onto the output will be shunted to ground through the resistor. If improved OFF- isolation is needed, the SSM2404 dual audio switch should be considered with its excellent 120 dB OFF-isolation at 20 kHz. It is important that all of the AGND pins be connected to the system analog ground. These pins isolate the input and output of each switch. Without connecting these pins, the OFF- isolation will degrade significantly. 6 REV. B90M2404 DETAILED SWITCH OPERATION A simplified circuit schematic with the functional sections is shown in Figure 21. The TTL interface has an internally regulated 5 V to ensure TTL logic levels regardless of the supply voltage. The logic threshold is with respect to the DGND pin, which can be offset. For example, if DGND is connected to the negative supply, then the SSM2404 will operate with negative rail logic. The interface shifts the control logic down to the negative supply and inverts it to drive N1. 100nA VW LY VW 2 3 > [rer SWI1A C1 "T 15pF SW CONTROL TTL penn o-| INTERFACE R BREAK-BEFORE-MAKE RAMP GENERATOR Figure 21. Simplified Schematic N1 in combination with C1 and the 100 nA current source provides the break-before-make operation of the switch. When the switch is on, N1 is off and C1 is charged up to the positive rail. However, when the SW CONTROL is turned off, then the gate of N1 is pulled high. This turns N1 on, providing a low impedance path to quickly discharge C1 to the negative rail, which quickly breaks the switch. On the other hand, when the SW CONTROL goes high again, the gate of N1 is pulled low, turning it off. This leaves C1 to be slowly charged up to the positive rail by the 100 nA current source. The difference in the discharge and charging times ensures break-before-make operation, even from device to device. The voltage on C1 is inverted by P1 to drive the ramp generator differential pair, consisting of P2, P3 and N2, N3. This dif- ferential pair steers the 100 nA of tail current to either charge or discharge C2. As discussed above, when the switch is on, C1 is charged up to the positive rail. Pl inverts this, putting a low voltage equivalent to the negative supply on the gate of P2. The BIAS voltage is approximately equal to the midpoint of the two supply voltages. Thus, when P2 is pulled down, it is turned on and P3 is off. All of the 100 nA flows through N2 and is mir- rored by N3. Thus, the 100 nA discharges C2 through N3. When C2 is pulled low, the inverter turns N4 on by pulling its gate high, and the second inverter turns P4 on. To turn the switch off the gate of P2 is pulled above the BIAS so that all 100 nA charges C2 through P3. This is then inverted to turn off N4 and P4. The internal ramp has rise and fall times on the order of a few milliseconds which is sped up by the inverters. As the gate REV. B voltages of N4 and P4 are changing, the ON resistance of each switch is ramping from its OFF state to 28 Q and vice versa. The actual rise and fall times are shown in Figures 18 and 19 fora 5 kQ load. These times are significantly slower than typical switches, minimizing the SSM2404s charge injection and giving it clickless performance. DOUBLE-POLE DOUBLE-THROW SWITCH The SSM2404 is ideal as a one-chip solution for a stereo switch. The schematic in Figure 22 shows the typical configura- tion. This circuit will select one of two stereo sources, channel Aor B. The switch controls for the left and right input of each channel are tied together so that both will be turned on or off simultaneously. An inverter is inserted between the channel A and B controls so that only one logic signal is needed. The out- puts can be configured many different ways, such as an invert- ing or noninverting amplifier stage, and the 10 kQ load resistors are added to improve the OFF-isolation. The performance of this stereo switch is equivalent to each individual switch, yield- ing a high quality audio switch that is virtually transparent to the signal. 1 SSM2404 I 101 I = Lina ! swe I I Le Si = Lins ' 6! SW2 CONTROL SWA/SWB SW3 CONTROL 4l vis DGND 5! SW1 CONTROL CHANNEL ' SELECTED SW4 CONTROL I wt 8 o A Figure 22. Double-Pole, Double-Throw Stereo Switch VIRTUAL GROUND SWITCHING The SSM2404 was built on a CMOS process with a 24 V operating limit for the total supply voltage across the part. This leads to a corresponding limit on the analog voltage range. How- ever, to achieve larger signal swings, the SSM2404 should be configured in the virtual ground mode. As shown in Figure 23, the output of the SSM2404 is connected to the inverting input of an amplifier. Since the noninverting input is grounded, the SSM2404 will also be biased at ground, and large voltage swings on the circuits input will not significantly change the voltage on the switch. The only limitation is that the current through the switch needs to be less than + 10 mA, and the voltage range is limited only by the op amp and its supply voltages.90M2404 The circuit was tested with an SSM2131 high slew rate audio amplifier and the results are shown in Figures 24 and 25. This configuration yields excellent THD performance that is primarily determined by the amplifier. Also, the headroom is now +24 dBu (0 dBu = 0.775 V rms), which is due to the amplifiers output voltage swing. Thus, even though the SSM2404 has a 12 V limitation on its supplies, it can be used in systems with much higher voltage ranges. For example, the double-pole double-throw switch from Figure 22 can be reconfigured in the virtual ground mode to allow higher voltage swings, as shown in Figure 26. This application realizes the excellent performance of Figures 24 and 25 while providing a low cost switching solution. +12V R2 5kQ. poesstag | SSM2404 | I I -18V Figure 23. Virtual Ground Switching GUDIO PRECISION S8H2404 THD+N(x) ve FREQ (He) a1 6.618 8.001 08S a in@ ik 16k 26k Figure 24. Virtual Ground Switch THD+N vs. Frequency (Vs =+12 V, Va =2 Vis, with 80 kHz Filter) AUDIO PRECISION SSH2404A THDN(:) ve AMPL(4Bu) 6.1 8.818 @.081 ones 5 : @.6 2.008 4.008 6.000 6.000 18.00 12.08 14.06 16.08 18.08 28.68 22.88 24.68 Figure 25, Virtual Ground Switch Headroom (Vs =+12 V for SSM2404; Vs =+18 V for Op Amp, f = 1 kHz, with 80 kHz Filter) Perr. "a - I I Pp! SSM2404 ' 5kQ 101 18 LinshO-WM\ 7 So T 5kQ ' sw2 1 I I 1 13 Lins o 1 Lout I 1 = $SM2131 , owe CONTROL Io SWA/SWB AGN 1 SW3 CONTROL F DGND ;oW1 CONTROL 161 1 SW4 CONTROL 5kQ. Rout = SSM2131 Figure 26. Double-Pole, Double-Throw Stereo Switch Using Virtual Ground Operation OUTLINE DIMENSIONS Dimensions shown in inches and (mm). Mini-DIP (P Suffix) 0.280 (7.11) 0.240 10) 7 Yo 0.325 (8.25) 1.060 (26.90) 0.300 (7.62) 0.925 (23.50) 0.060 (1.52) 0.210 0,015 (0.38) 0.195 (4.95) (6.33) 0.115 (2.93) MAX 0.150 0.200 (5.05) (3.81) # 0.015 (0.381) 0.125 (3.18) MIN ff 0.008 (0.204) = > \ 0.022 (0.558) 0.100 (2.54) 0.070 (1.77) \ SEATING 0.074 (0.356) BSC 0.045 (1.15) PLANE SOIC (S Suffix) 0.5118 (13.00) 0.4961 (12.60) AAAAAAAE 0.2992 (7.60) 0.2914 (7.40) PIN1 [> \ 0.4193 (10.65) 0.3937 ae" 00) Doegaeeoos | 0.1043 (2.65 0. os00 a2 27) 3.0026 me = 0.0201 (0.74) BSC *| ~ 0.0098 (0.25) * 0- 8 aaa, 4 i 0.0118 (0.30) 0.0192 (0.49) 0.0125 (0.32) 0.0500 (1.27) | IC 0.0040 (0.10) 0.0138 (0.35) 9.0091 (0.23) 0.0157 (0.40) REV. B C162620-1/92 PRINTED IN U.S.A.