19-0389; Rev. 2; 9/96 Fault-Protected Analog Multiplexers ____________________________Features The MAX354/MAX355 fault-protected multiplexers (muxes) use a series N-channel, P-channel, N-channel structure that protects the devices from overvoltage up to 40V beyond the supply rails during power-up, powerdown, and fault conditions. The MAX354/MAX355 also protect sensitive circuit components against voltages near or beyond the normal supplies. ♦ 350Ω Max On-Resistance ♦ Improved 2nd Source for MAX358/MAX359 and DG458/DG459 ♦ Pin Compatible with ADG508F/ADG509F ♦ All Switches Off with Supplies Off ♦ On Switch Turns Off with Overvoltage ♦ Output Clamps at 1.5V Below Supply Rails ♦ 0.5nA Max Input Leakage at +25°C (5nA at +85°C) ♦ No Power-Up Sequencing Required ♦ TTL and CMOS-Logic Compatibility The MAX354 single 8-channel mux and the MAX355 dual 4-channel mux protect analog signals while operating from a single 4.5V to 36V supply or ±4.5V to ±18V dual supplies. These muxes have 350Ω on-resistance and can be used for demultiplexing as well as multiplexing. Input leakage current is less than 0.5nA at +25°C and less than 5nA at +85°C. All digital inputs have 0.8V and 2.4V logic thresholds, ensuring both TTL and CMOS logic compatibility without pull-up resistors. Break-before-make operation is guaranteed and power consumption is less than 1.5mW. ______________Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX354CPE 0°C to +70°C 16 Plastic DIP MAX354CWE MAX354C/D MAX354EPE MAX354EWE MAX354MJE 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C -55°C to +125°C 16 Wide SO Dice* 16 Plastic DIP 16 Wide SO 16 CERDIP** Data-Acquisition Systems MAX355CPE 0°C to +70°C 16 Plastic DIP Industrial and Process Control MAX355CWE MAX355C/D MAX355EPE MAX355EWE MAX355MJE 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C -55°C to +125°C 16 Wide SO Dice* 16 Plastic DIP 16 Wide SO 16 CERDIP** ________________________Applications Avionics ATE Equipment Signal Routing Redundant/Backup Systems * Dice are tested at TA = +25°C only. ** Contact factory for availability. __________________________________________________________Pin Configurations TOP VIEW MAX354 A0 1 EN 2 V- 3 LOGIC MAX355 16 A1 A0 1 15 A2 EN 2 14 GND V- 3 16 A1 15 GND LOGIC 14 V+ NO1 4 13 V+ NO1A 4 13 NO1B NO2 5 12 NO5 NO2A 5 12 NO2B NO3 6 11 NO6 NO3A 6 11 NO3B NO4 7 10 NO7 NO4A 7 10 NO4B COM 8 9 NO8 COMA 8 9 DIP/SO COMB DIP/SO ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 MAX354/MAX355 _______________General Description ABSOLUTE MAXIMUM RATINGS (Voltages referenced to GND, unless otherwise noted.) V+ ...........................................................................-0.3V to +44V V- ............................................................................+0.3V to -44V V+ to V-...................................................................-0.3V to +44V Digital Inputs.........................................(V+ + 0.3V) to (V- - 0.3V) Input Overvoltage with Mux Power On V+ = +15V ....................................................................... +25V V- = -15V ............................................................................-25V Input Overvoltage with Mux Power Off V+ = 0V.............................................................................+40V V- = 0V ...............................................................................-40V Continuous Current into Any Terminal .............................±30mA Peak Current into Any Terminal ........................................±50mA Continuous Power Dissipation (TA = +70°C) Plastic DIP (derate 10.53mW/°C above +70°C) ...........842mW Wide SO (derate 9.52mW/°C above +70°C)................ 762mW CERDIP (derate 10.00mW/°C above +70°C) ...............800mW Operating Temperature Ranges MAX35_C_ _ ........................................................0°C to +70°C MAX35_E_ _......................................................-40°C to +85°C MAX35_M_ _ ...................................................-55°C to +125°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10sec) ............................ +300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V+ = +15V, V- = -15V, GND = 0V, VAH = VENH = 2.4V, VAL = VENL = 0.8V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS (V+ - 40) (V- + 40) V -12 12 V SWITCH Analog Signal Range Fault-Free Analog Signal Range On-Resistance (Note 2) On-Resistance Matching Between Channels NO-Off Leakage Current (Note 4) (Note 1) VCOM, VNO V+ = +15V, V- = -15V (Note 1) TA = +25°C RON ∆RON INO = 1.0mA, VCOM = ±10V INO = 1.0mA, VCOM = ±10V (Note 3) ± INO(OFF) VCOM = ±10V, VNO = ±10V, VEN = 0V ± COM-Off Leakage Current (Note 4) VCOM = ±10V, VNO = ±10V, VEN = 0V ICOM(OFF) VCOM = ±10V, VNO = ±10V, VEN = 0V ± MAX354/MAX355 Fault-Protected Analog Multiplexers TA = TMIN to TMAX 285 450 M 500 TA = +25°C 7 TA = TMIN to TMAX TA = +25°C TA = TMIN to TMAX -5.0 5.0 -50 50 -0.5 COM-On Leakage Current (Note 4) 2 ICOM(ON) VCOM = ±10V, VNO = ±10V, sequence each switch on -25 25 M -100 100 -0.5 0.02 0.5 C, E -15 15 M -50 50 -0.5 0.02 -30 30 M -200 200 0.02 0.5 C, E -15 15 M -100 100 _______________________________________________________________________________________ nA nA 0.5 C, E -0.5 Ω 0.5 C, E TA = +25°C MAX355 TA = TMIN to TMAX 0.02 Ω 0.5 M TA = +25°C MAX354 TA = TMIN to TMAX 0.01 C, E TA = +25°C MAX355 TA = TMIN to TMAX 12 15 -0.5 TA = +25°C MAX354 TA = TMIN to TMAX 350 C, E nA Fault-Protected Analog Multiplexers (V+ = +15V, V- = -15V, GND = 0V, VAH = VENH = 2.4V, VAL = VENL = 0.8V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP TA = +25°C -5 0.01 TA = TMIN to TMAX -2 MAX UNITS 5 nA 2 µA FAULT Output Leakage Current (with Overvoltage) VD = 0V, analog overvoltage = ±33V Input Leakage Current (with Overvoltage) VIN = ±25V, VO = ±10V Input Leakage Current (with Power Supplies Off) VIN = ±25V, VEN = VO = 0V, VA0 = VA1 = VA2 = 0V or 5V TA = +25°C TA = TMIN to TMAX TA = +25°C -0.1 0.001 -2 -0.1 TA = TMIN to TMAX -2 2.4 0.1 2 0.001 0.1 2 µA µA DIGITAL LOGIC INPUT Logic High Input Voltage VA_H, VENH TA = TMIN to TMAX Logic Low Input Voltage VA_L, VENL TA = TMIN to TMAX Input Current with Input Voltage High IA_H, IENH VA = VEN = 2.4V Input Current with Input Voltage Low IA_L, IENL VA = VEN = 0.8V V 0.8 TA = +25°C -1 1 TA = TMIN to TMAX -5 5 TA = +25°C -1 1 TA = TMIN to TMAX -5 5 V µA µA SUPPLY Power-Supply Range Positive Supply Current I+ VEN = VA = 5V Negative Supply Current I- VEN = VA = 0V ±4.5 ±18 TA = +25°C -300 300 TA = TMIN to TMAX -500 500 -1 1 -100 100 TA = +25°C TA = TMIN to TMAX V µA µA DYNAMIC TA = +25°C Transition Time tTRANS Figure1 Enable Turn-On Time tON(EN) Figure 2 Enable Turn-Off Time tOFF(EN) Figure 2 Break-Before-Make Interval tOPEN Figure 3 TA = +25°C Charge Injection VCTE CL = 10nF, VS = 0V, RS = 0Ω, Figure 4 Off Isolation 180 TA = TMIN to TMAX 250 400 TA = +25°C 160 TA = TMIN to TMAX 250 400 TA = +25°C 80 TA = TMIN to TMAX 200 300 ns ns 100 ns TA = +25°C 80 pC VISO VEN = 0V, RL = 1kΩ, f = 100kHz, TA = +25°C Figure 5 100 dB Crosstalk Between Channels VCT VEN = 2.4V, f = 100kHz, VGEN = 1Vp-p, RL = 1kΩ, Figure 6 TA = +25°C 92 dB Logic Input Capacitance CIN f = 1MHz, Figure 7 TA = +25°C 2.5 pF f = 1MHz, VEN = VD = 0V TA = +25°C 1.6 pF NO-Off Capacitance CNO(OFF) 50 ns pF _______________________________________________________________________________________ 3 MAX354/MAX355 ELECTRICAL CHARACTERISTICS (continued) ELECTRICAL CHARACTERISTICS (continued) (V+ = +15V, V- = -15V, GND = 0V, VAH = VENH = 2.4V, VAL = VENL = 0.8V, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DYNAMIC (cont’d) COM-Off Capacitance CCOM(OFF) f = 1MHz, Figure 7, MAX354 TA = +25°C VEN = VD = 0V MAX355 11 COM-On Capacitance CCOM(ON) f = 1MHz, Figure 7, MAX354 TA = +25°C VEN = VD = 0V MAX355 28 Setting Time (Note 5) tSETT 0.1% pF 14 1 TA = +25°C 0.01% pF 5 µs 2.5 Note 1: When the analog signal exceeds +13.5V or -13.5V, the blocking action of Maxim’s gate structure goes into operation. Only leakage currents flow, and the channel on-resistance rises to infinity (see Typical Operating Characteristics). Note 2: Electrical characteristics such as on-resistance will change when power supplies other than ±15V are used. Note 3: ∆RON = RON(MAX) - RON(MIN) Note 4: Leakage parameters are 100% tested at maximum rated hot operating temperature, and guaranteed by correlation at +25°C. Note 5: Guaranteed by design. __________________________________________Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) 600 RON (Ω) RON (Ω) 0.1 +125°C +85°C +70°C +25°C 500 V+ = +10V V- = -10V 1200 A: B: C: D: V+ = +15V V- = -15V 1400 1 1000 A 400 B 300 C 800 0.01 600 V+ = +15V V- = -15V 200 200 0 0.0001 -15 -10 -5 0 5 10 -15 15 -10 10 100 -10 15 -5 INO(OFF) V+ = +15V V- = -15V VCOM_ = ±10V 0 5 10 VCOM (V) CHARGE INJECTION vs. VCOM 200 V+ = +15V V- = -15V 150 100 Qj (pC) 1 ON LEAKAGE (nA) 10 ICOM(OFF) 0.1 5 100 MAX354-3 V+ = +15V V- = -15V VNO_ = ±10V VCOM_ = 10V 0 ON LEAKAGE vs. TEMPERATURE OFF LEAKAGE vs. TEMPERATURE 100 -5 ANALOG VOLTAGE (V) ANALOG VOLTAGE (V) 10 D 400 MAX354-5 0.001 V+ = +15V V- = -15V MAX354-4 RON (MΩ) V+ = +5V V- = -5V 1600 700 MAX354/5-2 1800 MAX354/5-1b V+ = +5V V- = -5V 10 2000 MAX354/5-1a 100 ON-RESISTANCE vs. VCOM AND TEMPERATURE ON-RESISTANCE vs. ANALOG VOLTAGE ON-RESISTANCE vs. ANALOG VOLTAGE OFF LEAKAGE (nA) MAX354/MAX355 Fault-Protected Analog Multiplexers 1 50 0 -50 -100 0.1 -150 -75 -50 -25 0 25 50 75 100 125 TEMPERATURE (°C) 4 -200 0.01 0.01 -75 -50 -25 0 25 50 75 100 125 TEMPERATURE (°C) -10 -5 0 VCOM (V) _______________________________________________________________________________________ 5 10 Fault-Protected Analog Multiplexers FAULT CURRENT vs. FAULT VOLTAGE SUPPLY CURRENT vs. TEMPERATURE I+ (VA_ = 5V) 1m FAULT CURRENT (A) I+, I- (µA) 100 V+ = +15V V- = -15V VEN = +5V 10m MAX354-6 1000 I+ (VA_ = 0V) 10 1 V+ = V- = 0V 100µ 10µ 1µ V+ = +15V V- = -15V 100m 10n 1n 100p I0.1 -75 -50 -25 0 25 50 75 100 125 10p -70 -50 -30 -10 10 30 50 70 FAULT VOLTAGE (V) TEMPERATURE (°C) ______________________________________________________________Pin Description PIN NAME FUNCTION MAX354 MAX355 1, 15, 16 — A0, A2, A1 Address Logic Inputs — 1, 16 A0, A1 Address Logic Inputs 2 2 EN Enable Logic Input. See truth tables. 3 3 V- Negative Supply Voltage Input. Connect to GND for single-supply operation. 4–7 — NO1–NO4 — 4–7 NO1A–NO4A 8 — COM Analog Output—bidirectional — 8, 9 COMA, COMB Analog Outputs—bidirectional 9–12 — NO8–NO5 — 10–13 NO4B–NO1B 13 14 V+ 14 15 GND Analog Inputs—bidirectional Analog Inputs—bidirectional “A” switch Analog Inputs—bidirectional Analog Inputs—bidirectional “B” switch Positive Supply Voltage Input Ground Note: Analog inputs and outputs are electrically identical and completely interchangeable. _______________________________________________________________________________________ 5 MAX354/MAX355 ____________________________Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) MAX354/MAX355 Fault-Protected Analog Multiplexers ______________________________________________Test Circuits/Timing Diagrams +15V V+ NO1 A2 A1 +10V NO2-NO7 A0 MAX354 VEN NO8 EN -10V COM GND VOUT V- 35pF 50Ω LOGIC INPUT VEN 300Ω -15V 50% 0V VNO1 +15V SWITCH OUTPUT VOUT V+ NO1B A1 +10V 90% 0V 90% A0 VNO8 NO1A-NO4A VEN tR < 20ns tF < 20ns +3V NO4B MAX355 EN -10V GND ON VOUT 50Ω tTRANS tTRANS COMB V35pF 300Ω -15V Figure 1. Transition Time +15V VEN V+ EN NO1 +10V NO2–NO8 A0 A1 MAX354 A2 COM GND 50Ω VOUT V- 35pF 1k LOGIC INPUT VEN -15V V+ EN A1 50Ω 0V tON(EN) tOFF(EN) NO1B 10% SWITCH OUTPUT VOUT +10V NO1A–NO4A NO2B–NO4B, COMA A0 50% 0V +15V VEN tR < 20ns tF < 20ns +3V 90% MAX355 GND COMB V- VOUT 1k 35pF -15V Figure 2. Enable Switching Time 6 _______________________________________________________________________________________ Fault-Protected Analog Multiplexers +15V VEN +2.4V V+ EN NO1–NO8 A0 +10V 50% 0V MAX354 +5V A1 VA tR < 20ns tF < 20ns +3V LOGIC INPUT VA 80% A2 COM GND SWITCH OUTPUT VOUT VOUT V- 35pF tOPEN 0V 300Ω 50Ω -15V Figure 3. Break-Before-Make Interval +15V RS V+ NO VEN VS CHANNEL SELECT LOGIC INPUT VEN EN A0 MAX354 COM A1 +3V OFF ON OFF 0V VOUT A2 CL = 1000nF GND V- ∆VOUT VOUT ∆VOUT IS THE MEASURED VOLTAGE DUE TO CHARGE TRANSFER ERROR VCTE WHEN THE CHANNEL TURNS OFF. -15V VCTE = ∆VOUT x CL Figure 4. Charge Injection _______________________________________________________________________________________ 7 MAX354/MAX355 _________________________________Test Circuits/Timing Diagrams (continued) MAX354/MAX355 Fault-Protected Analog Multiplexers _________________________________Test Circuits/Timing Diagrams (continued) +15V NO1 VIN RS = 50Ω +15V 10nF NO1 V+ NO8 R = 1kΩ VIN COM A0 A1 A2 GND EN V- VOUT V+ NO2 NO8 MAX354 MAX354 A0 RG = 50Ω RL 1k 10nF COM A1 A2 GND EN V- VOUT RL 1k 10nF 10nF -15V -15V OFF ISOLATION = 20log VOUT CROSSTALK = 20log VIN Figure 5. Off Isolation VOUT VIN Figure 6. Crosstalk +15V V+ A2 CHANNEL SELECT A1 NO1 NO8 MAX354 A0 GND EN V- 1MHz CAPACITANCE ANALYZER COM f = 1MHz -15V Figure 7. NO/COM Capacitance _______________Detailed Description Fault-Protection Circuitry Maxim’s MAX354/MAX355 are fully fault protected for continuous input voltages up to ±40V, whether or not the V+ and V- power supplies are present. These devices use a “series FET” protection scheme that not only protects the multiplexer output from overvoltage, but also limits the input current to sub-microamp levels. When signal voltages exceed or are within approximately 1.5V of the supply rails, on-resistance increases. This greater on-resistance limits fault currents and output voltage, protecting sensitive circuits and components. The protected output clamps at approximately 8 1.5V below the supply rails and maintains the correct polarity. There are no glitches or polarity reversals going into or coming out of a fault condition. Figures 8 and 9 show how the series FET circuit protects against overvoltage conditions. When power is off, the gates of all three FETs are at ground. With a -25V input, N-channel FET Q1 is turned on by the +25V gate-tosource voltage. The P-channel device (Q2), however, has +25V VGS and is turned off, thereby preventing the input signal from reaching the output. If the input voltage is +25V, Q1 has a negative VGS, which turns it off. Similarly, only sub-microamp leakage currents can flow from the output back to the input, since any voltage will turn off either Q1 or Q2. _______________________________________________________________________________________ Fault-Protected Analog Multiplexers Q1 -25V OVERVOLTAGE S -25V Q2 D N-CHANNEL MOSFET IS TURNED ON BECAUSE VGS = +25V S S D G G P-CHANNEL MOSFET IS OFF Figure 8. -25V Overvoltage with Multiplexer Power Off -15V -25V OVERVOLTAGE N-CHANNEL MOSFET IS TURNED ON BECAUSE VGS = +10V Q1 -15V FROM DRIVERS +15V Q2 +15V FROM DRIVERS Table 1 shows typical charge injection levels versus power-supply voltages and analog input voltage. The charge injection that occurs during switching creates a voltage transient whose magnitude is inversely proportional to the capacitance on the multiplexer output. Table 1. MAX354 Charge Injection Supply Voltage Analog Input Level Injected Charge ±5V +2V 0V -2V 52pC 35pC 16pC ±10V +5V 0V -5V 105pC 65pC 25pC ±15V +10V 0V -10V 180pC 80pC 15pC Test Conditions: CL, = 1000pF on mux output; the tabulated analog input level is applied to channel 1; channels 2–8 inputs are open circuited. EN = +5V, VA1 = VA2 = 0V, VO is toggled at a 2kHz rate between 0V and 3V. +100pC of charge creates a +100mV step when injected into a 1000pF load capacitance. Q3 D G Switching Characteristics and Charge Injection Q2 D N-CHANNEL MOSFET IS TURNED OFF BECAUSE VGS = -25V S G S D G -15V +25V FORCED ON COMMON OUTPUT LINE BY EXTERNAL CIRCUITRY N-CHANNEL MOSFET IS OFF Q3 D G Figure 9. +25V Overvoltage with Multiplexer Power Off -15V Q3 Q1 +25V OVERVOLTAGE S +25V OVERVOLTAGE N-CHANNEL MOSFET IS TURNED OFF BECAUSE VGS = -10V Q1 +15V 13.5V Q2 -15V Q3 13.5V OUTPUT VTN = 1.5V +15V FROM DRIVERS -15V FROM DRIVERS N-CHANNEL MOSFET IS ON P-CHANNEL MOSFET IS OFF Figure 10. -25V Overvoltage on an Off Channel with Multiplexer Power Supply On Figure 11. +25V Overvoltage Input to the On Channel _______________________________________________________________________________________ 9 MAX354/MAX355 Figure 10 shows the condition of an off channel with V+ and V- present. As with Figures 8 and 9, either an Nchannel or a P-channel device will be off for any input voltage from -40V to +40V. The leakage current with negative overvoltages will immediately drop to a few nanoamps at +25°C. For positive overvoltages, that fault current will initially be 10µA or 20µA, decaying over a few seconds to the nanoamp level. The time constant of this decay is caused by the discharge of stored charge from internal nodes and does not compromise the fault-protection scheme. Figure 11 shows the condition of the on channel with V+ and V- present. With input voltages less than ±10V, all three FETs are on and the input signal appears at the output. If the input voltage exceeds V+ minus the N-channel threshold voltage (VTN), the N-channel FET will turn off. For voltages more negative than V- minus the P-channel threshold (VTP), the P-channel device will turn off. Since VTN is typically 1.5V and VTP is typically 3V, the multiplexer’s output swing is limited to about -12V to +13.5V with ±15V supplies. MAX354/MAX355 Fault-Protected Analog Multiplexers The channel-to-channel switching time is typically 180ns, with about 100ns of break-before-make delay. This 100ns break-before-make delay prevents the input-to-input short that would occur if two input channels were simultaneously connected to the output. In a typical data acquisition system, the dominant delay is not the switching time of the multiplexer, but is the settling time of the amplifiers and S/H. Another limiting factor is the RC time constant of the multiplexer RON plus the signal source impedance multiplied by the load capacitance on the output of the multiplexer. Even with low signal source impedances, 100pF of capacitance on the multiplexer output will approximately double the settling time to 0.01% accuracy. Operation with Supply Voltages Other than ±15V The main effect of supply voltages other than ±15V is the reduction in output signal range. The MAX354 limits the output voltage to about 1.5V below V+ and about 3V above V-. In other words, the output swing is limited to +3.5V to -2V when operating from ±5V. The Typical Operating Characteristics show RON for +15V and ±5V power supplies. Maxim tests and guarantees the MAX354/MAX355 for operation from ±4.5V to ±18V supplies. The switching delays are increased by about a factor of 2 at ±5V, but break-before-make action is preserved. The MAX354/MAX355 can operate with a single +4.5V to +30V supply, as well as asymmetrical power supplies such as +15V and -5V. The digital threshold remains approximately 1.6V above the GND pin, and the analog characteristics, such as R ON, are determined by the total voltage difference between V+ and V-. Connect V- to 0V when operating with a +4.5V to +30V single supply. The MAX354 digital threshold is relatively independent of the power-supply voltages, going from 1.6V typical when V+ is 15V to 1.5V typical when V+ is 5V. This means that the MAX354/MAX355 operate with standard TTL-logic levels, even with ±5V power supplies. In all cases, the threshold of the enable (EN) pin is the same as the other logic inputs. 10 Digital Interface Levels The typical digital threshold of both the address lines and the enable pin is 1.6V, with a temperature coefficient of about -3mV/°C. This ensures compatibility with 0.8V to 2.4V TTL-logic swings over the entire temperature range. The digital threshold is relatively independent of the supply voltages, moving from 1.6V typical to 1.5V typical as the power supplies are reduced from ±15V to ±5V. In all cases, the digital threshold is referenced to the GND pin. The digital inputs can also be driven with CMOS-logic levels swinging from either V+ to V- or from V+ to ground. The digital input current is just a few nanoamps of leakage at all input voltage levels, with a guaranteed maximum of 1µA. Operation as a Demultiplexer The MAX354/MAX355 function as demultiplexers where the input is applied to the output pin, and the input pins are used as outputs. The MAX354/MAX355 provide both break-before-make action and full fault protection when operated as demultiplexers, unlike earlier generations of fault-protected muxes. Channel-to-Channel Crosstalk, Off-Isolation, and Digital Feedthrough At DC and low frequencies the channel-to-channel crosstalk is caused by variations in output leakage currents as the off-channel input voltages are varied. The MAX354 output leakage varies only a few picoamps as all seven off inputs are toggled from -10V to +10V. The output voltage change depends on the impedance level at the MAX354 output, which is RON plus the input signal source resistance in most cases, since the load driven by the MAX354 is usually high impedance. For a signal source impedance of 10kΩ or lower, the DC crosstalk exceeds 120dB. Tables 2a and 2b show typical AC crosstalk and offisolation performance. Digital feedthrough is masked by the analog charge injection when the output is enabled. When the output is disabled, the digital feedthrough is virtually unmeasureable, since the digital pins are physically isolated from the analog section by the GND and V- pins. The ground plane formed by these lines is continued onto the MAX354/MAX355 die to provide over 100dB isolation between the digital and analog sections. ______________________________________________________________________________________ Fault-Protected Analog Multiplexers Frequency 100kHz 1MHz One Channel Driven 100dB 80dB Table 2b. Typical Crosstalk Rejection Ratio Test Conditions: V IN = 20Vp-p at the tabulated frequency, RL = 1.5kΩ between OUT and ground, EN = 0V. 20Vp-p VISO = 20log ————— VOUT (p-p) Frequency 100kHz 1MHz RL = 1.5kΩ 92dB 72dB RL = 10kΩ 76dB 56dB Test Conditions: Specified RL connected from OUT to ground, EN = +5V, A0 = A1 = A2 = +5V (Channel 1 selected). 20Vp-p at the tabulated frequency is applied to Channel 2. All other channels are open circuited. Similar crosstalk rejection can be observed between any two channels. __________________________________________Functional Diagrams/Truth Tables MAX354 V+ V- GND MAX354 NO1 A2 A1 A0 EN ON SWITCH NO2 NO3 X X X 0 NONE NO4 0 0 0 1 1 0 0 1 1 2 0 1 0 1 3 0 1 1 1 4 1 0 0 1 5 1 0 1 1 6 1 1 0 1 7 1 1 1 1 8 COM NO5 NO6 NO7 NO8 DECODERS / DRIVERS A0 MAX355 A1 V+ A2 V- EN LOGIC "O" VAL ≤ +0.8V, LOGIC "1" VAH ≥ +2.4V GND NO1A NO2A NO3A MAX355 COMA NO4A NO1B COMB NO2B NO3B NO4B A1 A0 EN ON SWITCH X X 0 NONE 0 0 1 1 0 1 1 2 1 0 1 3 1 1 1 4 DECODERS / DRIVERS LOGIC "O" VAL ≤ +0.8V, LOGIC "1" VAH ≥ +2.4V A0 A1 EN ______________________________________________________________________________________ 11 MAX354/MAX355 Table 2a. Typical Off-Isolation Rejection Ratio MAX354/MAX355 Fault-Protected Analog Multiplexers __________________________________________________________Chip Topographies MAX354 EN A0 A1 A2 MAX355 EN GND A0 A1 GND V- V- V+ N.C. V+ N01 N01A N05 N01B 0.130" (3.30mm) 0.130" (3.30mm) N02 N06 N03 N.C. N04 COM N08 N02A N02B N03A N03B N04A N07 COMA COMB N04B 0.115" (2.92mm) 0.115" (2.92mm) TRANSISTOR COUNT: 256 SUBSTRATE CONNECTED TO V+ Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.