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| Semiconductor April 1999 CT T ODU MEN E PR PLACE -7747 ET OL RE -442 OBS ENDED -800 M ns 1 rris.com M io licat ECO ha NO R ntral App entapp@ c e C : Call or email IH401A QUAD Varafet Analog Switch Features * rDS(ON) (Typ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 * ID(OFF) (Typ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10pA * Switching Times (RL = 1k) - tON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25ns - tOFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75ns * Built-In Overvoltage Protection . . . . . . . . . . . . . . 25V * Charge Injection Error (Typ) into 0.01F Capacitor . . 3mV * CISS (Typ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <1pF * Can Be Used for Hybrid Construction Description The IH401A is made up of 4 monolithically constructed combinations of varacitor type diode and a N-Channel JFET. The JFET itself is very similar to the popular 2N4391, and the driver diode is specially designed, such that its capacitance is a strong function of the voltage across it. The driver diode is electrically in series with the gate of the N-Channel FET and simulates a back-to-back diode structure. This structure is needed to prevent forward biasing the source-to-gate or drain-to-gate junctions of the JFET when used in switching applications. Previous applications of JFETs required the addition of diodes, in series with the gate, and then perhaps a gate-tosource referral resistor or a capacitor in parallel with the diode; therefore, at least 3 components were required to perform the switch function. The IH401A does this same job in one component (with a great deal better performance characteristics). Like a standard JFET, the practically perform a solid state switch function translator should be added to drive the diode. This translator takes the TTL levels and converts them to voltages required to drive the diode/FET system (typically a 0V to -15V translation and a 3V to +15V shift). With 15V power supplies, the IH401A will typically switch 22VP-P at any frequency from DC to 20MHz, with less than 50 rDS(ON) . IH401A (CERDIP) TOP VIEW S1 1 D1 2 DR1 3 4 DR2 5 S2 6 D2 7 8 16 D4 15 S4 14 DR4 13 12 DR3 11 S3 10 D3 9 Part Number Information PART NUMBER IH401A TEMP. RANGE (oC) -55 to 125 PACKAGE 16 Ld CERDIP Pinout CAUTION: These devices are sensitive to electrostatic discharge. Users should follow proper IC Handling Procedures. Copyright (c) Harris Corporation 1999 File Number 3128.2 14-1 IH401A Absolute Maximum Ratings Supply Voltage VS to VD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35V VG to VS , VD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35V Thermal Information Maximum Junction Temperature (Ceramic Package) . . . . . . . . . 175oC Storage Temperature Range . . . . . . . . . . . . . . . . . . .-65oC to 150oC Lead Temperature (Soldering, 10s). . . . . . . . . . . . . . . . . . . . . 300oC Operating Conditions Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . .55oC to 125oC CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Electrical Specifications PARAMETER Switch "ON" Resistance At 25oC/125oC SYMBOL rDS(ON) TEST CONDITIONS VDRIVE = 15V, VDRAIN = -10V, ID = 10mA ID = 1nA, VDS = 10V VDRIVE = -15V, VSOURCE = -10V, VDRAIN = +10V VDRIVE = -15V, VSOURCE = -10V, VDRAIN = +10V VDRIVE = -15V, VDRAIN = -10V, VSOURCE = +10V VDRIVE = -15V, VSOURCE = -10V, VDRAIN = +10V VD = VS = -10V, VDRIVE= +15V See Figure 2 See Figure 3 VD = VS = -V, IDRIVE = 1A, DRIVE = 0V VDRIVE = -V, VD = VS = 0V, DRIVE = 1A VDRIVE = 15V, VS = 0V, D = +10V See Figure 1 See Figure 1 MIN TYP 35 MAX 50 UNITS Pinch-Off Voltage Switch "OFF" Current or "OFF" Leakage VP ID(OFF) 2 - 4 10 5 500 V pA Switch "OFF" Leakage at 125oC ID(OFF) - 0.25 50 nA Switch "OFF" Current IS(OFF) - 10 500 pA Switch "OFF" Leakage at 125oC IS(OFF) - 0.3 50 nA Switch Leakage When Turned "ON" ID(ON) = IS(ON) VANALOG VINJECT BVDIODE - 0.02 2 nA AC Input Voltage Range without Distortion Charge Injection Amplitude Diode Reverse Breakdown Voltage. This Correlates to Overvoltage Protection 20 -30 22 3 -45 - VP-P mVP-P V Gate to Source or Gate to Drain Reverse Breakdown Voltage BVGSS 30 41 - V Maximum Current Switch can Deliver (Pulsed) IDSS 35 55 - mA Switch "ON" Time (Note 1) Switch "OFF" Time (Note 1) NOTE: tON tOFF - 50 150 - ns ns 1. Driving waveform must be >100ns rise and fall time. 14-2 IH401A Test Circuits SIGNAL +5V +15V -15V STROBE INPUT 1k tON -15V VOUT tON 90% -5V +15V 0V -15V 90% STROBE INPUT +5V 90% 10% tOFF 0V 0V 10% tOFF +5V SIGNAL -5V SIGNAL 10% FIGURE 1. SWITCHING TIME TEST CIRCUIT AND WAVEFORMS VIN f = 1kH +15V VOUT 1k 0V -15V C = 0.01F VOUT FIGURE 2. ANALOG INPUT VOLTAGE RANGE TEST CIRCUIT FIGURE 3. CHARGE INJECTION TEST CIRCUIT Applications IH401A Family In general, the IH401A family can be used in any application formally using a JFET/isolation diode combination (2N4391 or similar). Like standard FET circuits, the IH401A requires a translator for normal analog switch function. The translator is used to boost the TTL input signals to the 15V analog supply levels which allow the IH401A to handle 10V analog signals. A typical simple PNP translator is shown in Figure 4. -15V 10k 1/4 OF IH401A +15V 0V FROM TTL OPEN COLLECTOR LOGIC 10k ANALOG OUT RL +15V ANALOG SIGNALS IN A translator which overcomes the problems of the simple PNP stage is the Harris IH6201 (See Note). This translator driving an IH401A varafet produces the following typical features: * tON time of approx. 200ns * tOFF time of approx. 80ns * TTL compatible strobing levels of break before make switch 2.4V 0.4V * ID(ON) + IS(ON) typically 20pA up to 10V analog signals * ID(OFF) or IS(OFF) typically 20pA * Quiescent current drain of approx. 100nA in either "ON" or "OFF" case NOTE: The IH6201 is a dual translator (two independent translators per package) constructed from monolithic CMOS technology. The schematic of one-half IH6201, driving one-fourth of an IH401A, is shown in Figure 5. FIGURE 4. TYPICAL SIMPLE PNP TRANSLATOR Although this simple PNP circuit represents a minimum of components, it requires open collector TTL input and t(OFF) is limited by the collector load resistor (approximately 1.5s for 10k). Improved switching speed can be obtained by increasing the complexity of the translator stage. A very useful feature of this system is that one-half of an IH6201 and one-half of an IH401A can combine to make a SPDT switch, or an IH6201 plus an IH401A can make a dual SPDT analog switch. (See Figure 8) 14-3 IH401A Typical Application Schematic (1/2 of IH401A, Driving 1/4 of an IH401A) +15V V+ 2.4V 0.4V TTL OR CMOS INPUT STROBE 10k 4k D S VARAFET +15V GND +15V VL +5V V1 20k 2k 1k -15V -15V V1k +15V -15V -15V TRANSLATOR (IH6201) NOTE: Each transistor output has a and output. is just the inverse of , i.e., ( output is 180 degrees out of phase with respect to output). FIGURE 5. IH6201 DRIVING AN IH401A Switching Information 1 2 3 4 5 6 7 8 IH401A 16 15 14 13 12 11 10 9 2 1 1 2 3 4 5 6 7 8 IH6201 16 15 14 -15V 13 12 +5V 11 +15V 10 9 0V 3V T2L2 0V 3V T2L1 NOTE: Either switch is turned on when strobe input goes high. FIGURE 6. DUAL SPST ANALOG SWITCH 1 2 3 4 5 6 7 8 IH401A 16 15 14 13 12 11 10 9 1 1 2 16 15 14 -15V IH6201 13 12 +5V 11 +15V 10 9 0V 3V T2L1 1 3 4 5 6 7 8 FIGURE 7. DPDT ANALOG SWITCH 14-4 IH401A Switching Information (Continued) 1 2 3 4 5 6 7 8 IH401A 16 15 14 13 12 11 10 9 2 1 2 1 1 2 3 4 5 6 7 8 IH6201 16 15 14 -15V 13 12 +5V 11 +15V 10 9 T2L INPUT 2 T2L INPUT 1 FIGURE 8. DUAL SPDT ANALOG SWITCH 1 2 3 4 5 6 7 8 IH401A 16 15 14 13 12 11 10 9 1 1 2 3 4 5 6 IH6201 16 15 14 -15V 13 12 +5V 11 +15V 10 9 T2L INPUT T2L INPUT 2 7 8 FIGURE 9. DUAL DPST ANALOG SWITCH 14-5 |
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