intersil ISL28288 ISL28488 handbook
Contents
1. intersil 120 80 400 200 80 40 80 150 a PHASE 100 m d 60 S 40 0 w T z lt Z y lt I z 40 E o p 40 2 lt 0 Z B an a GAIN 50 40 80 0 100 80 120 20 150 1 10 100 1k 10k 100k 1M 10M 10 100 1k 10k 100k 1M FREQUENCY Hz FREQUENCY Hz FIGURE 3 Ayo vs FREQUENCY O 100kQ LOAD FIGURE 4 Ayo vs FREQUENCY O 1kQ LOAD 10 SS 10 o LV 5VDC 0 V4 V 2 5VDC V 1V a 40 SOURCE 1Vp p 10 Vsource 1Vp p RL gt 10kQ RL lt 10kQ 20 RL 20 Ay 1 T 30 730 t 40 PSRR S 40 50 E 50 a 60 PSRR O 60 70 70 80 80 90 90 100 100 10 100 1k 10k 100k 1M 10 100 1k 10k 100k 1M FREQUENCY Hz FREQUENCY Hz FIGURE 5 PSRR vs FREQUENCY FIGURE 6 CMRR vs FREQUENCY 4 FN6339 1 June 28 2007 ISL28288 ISL28488 Typical Performance Curves v 5v V 0V Ven 2 5V RL Open Continued VOLTS V 10 00 1 00 0 10 CURRENT NOISE pA NHz 1 10 100 1k 10k 100k FREQUENCY Hz FIGURE 7 CURRENT NOISE vs FREQUENCY VOLTAGE NOISE2. 1000 100 800 80 V4 5V 600 60 RL OPEN dni dn Re 100k Rg 100 7 Ay 1000 S 200 T 20 o 0 n 0 lt gt 200 N 20 400 V4 5V 40 600 RL OPEN 60 RE 100k Rg 100 800 Ay 1000 s 1000 7 0 1 2 3 4 5 6 nic 0 1 2 3 4 5 6 VcM V VcM V FIGURE 13 INPUT OFFSET VOLTAGE vs COMMON MODE FIGURE 14 INPUT BIAS CURRENT vs COMMON MODE INPUT VOLTAGE INPUT VOLTAGE N 1000 MAX 250 MEDIAN CURRENT pA CURRENT uA MIN 40 20 0 20 40 60 80 100 120 40 20 0 20 40 60 80 100 120 TEMPERATURE C TEMPERATURE C FIGURE 15 ISL28488 SUPPLY CURRENT vs TEMPERATURE FIGURE 16 ISL28288 SUPPLY CURRENT vs TEMPERATURE V V 2 5V ENABLED RL INF V4 V 2 5V DISABLED R INF 2 LN 1000 HAX 2 N 1000 15 15 HA 1 1 d s MEDIAN Jh g ON gt 0 5 gt 0 5 MIN a MIN 1 5 gt E 1 5 2 2 Tan 20 0 20 40 60 80 100 120 2540 20 0 20 40 60 80 100 120 TEMPERATURE C TEMPERATURE C FIGURE 17 Vos vs TEMPERATURE VIN OV V4 V 2 5V FIGURE 18 Vos vs TEMPERATURE Vin OV V V 1 2V 6 _intersil F
3. MIN MAX PARAMETER DESCRIPTION CONDITIONS Note 1 TYP Note 1 UNIT DC SPECIFICATIONS Vos Input Offset Voltage 1 5 0 05 1 5 mV 2 2 AVos Long Term Input Offset Voltage Stability ISL28288 1 2 uV Mo ATime AVos Input Offset Voltage vs Temperature 0 9 uv C AT los Input Offset Current 30 15 30 pA 40 C to 85 C 80 80 lg Input Bias Current 30 10 30 pA 40 C to 85 C 80 80 CMIR Common Mode Voltage Range Guaranteed by CMRR 0 5 V CMRR Common Mode Rejection Ratio VGM OV to 5V 80 100 dB 75 PSRR Power Supply Rejection Ratio Vi 2 4V to 5V 85 105 dB 80 AVOL Large Signal Voltage Gain Vo 0 5V to 4 5V R 100kQ 200 300 VimV 190 Vo 0 5V to 4 5V Rp 1kO 60 VimV VOUT Maximum Output Voltage Swing Output low RL 100kQ 3 6 mV 30 Output low RL 1kQ 130 175 mV 225 Output high RL 100kQ 4 990 4 996 V 4 97 Output high Ry 1kQ 4 800 4 880 V 4 750 IS ON Quiescent Supply Current Enabled ISL28288 All channels enabled 120 156 UA 175 ISL28488 All channels enabled 240 315 pA 350 i H FN6339 1 2 Intersil June 28 2007 ISL28288 ISL28488 Electrical Specifications v 5v V OV Veu 2 5V RL Open Ta 25 C unless otherwise specified Boldface limits apply over the operating temperature range 40 C to 125 C Temperature data established by characterization Continued
4. MIN MAX PARAMETER DESCRIPTION CONDITIONS Note 1 TYP Note1 UNIT Is OFF Quiescent Supply Current Disabled All channels disabled 4 7 UA ISL28288 9 lo Short Circuit Sourcing Capability RL 100 29 31 mA 24 lo Short Circuit Sinking Capability RL 100 24 26 mA 20 VSUPPLY Supply Operating Range V to V 2 4 5 0 VERH EN Pin High Level ISL28288 2 VENL EN Pin Low Level ISL28288 0 8 IENH EN Pin Input High Current ISL28288 VEN V 0 8 1 UA 1 5 lENL EN Pin Input Low Current ISL28288 VEN V 0 0 1 UA AC SPECIFICATIONS GBW Gain Bandwidth Product Ay 100 Rf 100kQ RG 1kQ 300 kHz RL 10kQ to NCM en Input Noise Voltage Peak to Peak f 0 1Hz to 10Hz 5 4 HVP P Input Noise Voltage Density fo 1kHz 48 nVINHz in Input Noise Current Density fo 1kHz 0 1 pA VHz CMRR 2 60Hz Input Common Mode Rejection Ratio VcM 1Vp p RL 10kO to VGM 70 dB PSRR Power Supply Rejection Ratio V V V 1 2V and 2 5V 80 dB 120Hz Vsource 1Vp p RL 10kQ to Ven PSRR Power Supply Rejection Ratio V_ V4 V 1 2V and 2 5V 60 dB 120Hz VSOURCE 1Vp p RL 10kQ to NCM TRANSIENT RESPONSE SR Slew Rate 0 12 0 14 0 16 V us 0 09 0 21 tEN Enable to Output Turn on Delay Time VEN 5V to OV Ay 1 2 US 10 EN to 10 Vout ISL28288 Rg Rf R 1k to Von Enable to Output Turn off Delay Time VEN OV to 5V Ay 1 0 1 us 10 EN to 10 Vout ISL28288 Rg Rf R 1k to Von NOTE 1 Parts are 100 tested at
5. 2 5V RL 100k 7 intersil FN6339 1 June 28 2007 ISL28288 ISL28488 Typical Performance Curves v 5v v 0v Ven 2 5V RL Open Continued 90 n 1000 80 MAX 70 MEDIAN 60 AvoL VImV 50 MIN 40 30 40 20 0 20 40 60 80 100 120 TEMPERATURE C FIGURE 25 Ayo_ vs TEMPERATURE V4 V 2 5V RL 1k 120 T Z e 110 MEDIAN o pnm c n 100 40 20 0 20 40 60 80 100 120 TEMPERATURE C FIGURE 27 PSRR vs TEMPERATURE Vy V 1 2V TO 2 75V VOUT V 40 20 0 20 40 60 80 100 120 TEMPERATURE C FIGURE 29 Vour HIGH vs TEMPERATURE V V 2 5V RL 100k 135 n 1000 MAX 125 _ 115 t z 105 MEDIAN O 95 MIN 85 75 40 20 0 20 40 60 80 100 120 TEMPERATURE C FIGURE 26 CMRR vs TEMPERATURE Vcy 2 5V TO 2 5V Vas V 2 5V 4 91 n 1000 MAX 4 90 4 89 gt ass 5 MEDIAN 4 O 487 4 86 MIN 4 85 4 84 40 20 0 20 40 60 TEMPERATURE C FIGURE 28 Vour HIGH vs TEMPERATURE V4 V 2 5V R 1k 170 80 100 120 VOUT mV 40 20 0 20 40 60 TEMPERATURE
6. Data Sheet Dual and Quad Micropower Single Supply Rail to Rail Input and Output RRIO Op Amp The ISL28288 and ISL28488 are dual and quad channel micropower operational amplifiers optimized for single supply operation over the 2 4V to 5V range They can be operated from one lithium cell or two Ni Cd batteries For equivalent performance in a single channel op amp reference EL8188 These devices feature an Input Range Enhancement Circuit IREC which enables them to maintain CMRR performance for input voltages 10 above the positive supply rail and to 100mV below the negative supply The output operation is rail to rail The ISL28288 and ISL28488 draw minimal supply current while meeting excellent DC accuracy AC performance noise and output drive specifications The ISL28288 contains a power down enable pin that reduces the power supply current to typically less than ApA in the disabled state Pinouts ISL28288 10 LD MSOP TOP VIEW ISL28488 16 LD QSOP TOP VIEW ISL28288 ISL28488 June 28 2007 FN6339 1 Features Low power 120A typical supply current 1 5mV max offset voltage 30pA max input bias current 300kHz typical gain bandwidth product s 105GB typical PSRR e 1000B typical CMRR Single supply operation down to 2 4V nput is capable of swinging above V and below V ground sensing Rail to rail input and output RRIO s Enable Pin ISL28288 only Pb free plus anneal av
7. Supply Voltage 5 5V Thermal Resistance 03A C W Supply Turn On Voltage Slew Rate 1V us 10 Ld MSOP Package 115 Differential Input Current 5mA 16 Ld QSOP Package 112 Differential Input Voltage 0 5V Output Short Circuit Duration esses Indefinite Input Voltage ESD Tolerance Human Body Model Machine Model 300V Ambient Operating Temperature Range 40 C to 125 C Storage Temperature Range 65 C to 150 C Operating Junction Temperature Pb free reflow profile http www intersil com pbfree Pb FreeReflow asp CAUTION Do not operate at or near the maximum ratings listed for extended periods of time Exposure to such conditions may adversely impact product reliability and result in failures not covered by warranty IMPORTANT NOTE All parameters having Min Max specifications are guaranteed Typical values are for information purposes only Unless otherwise noted all tests are at the specified temperature and are pulsed tests therefore T Tc TA El ctrical Specifications v4 5v V OV Vey 2 5V RL Open TA 25 C unless otherwise specified Boldface limits apply over the operating temperature range 40 C to 125 C Temperature data established by characterization
8. C FIGURE 30 Vout LOW vs TEMPERATURE V4 V 2 5V RL 1k 80 100 120 8 intersil FN6339 1 June 28 2007 ISL28288 ISL28488 Typical Performance Curves v 5v V 0V Vem 2 5V RL Open Continued 4 3 E 39 T H n 12 n 1000 s 4 1 E 35 4 0 5 S MAX o 3 9 MEDIAN E 33 5 EE 3 38 X 31 j 3 7 o0 MIN C 29 3 6 2 MIN E 27 3 5 gt o 3 4 25 40 20 0 20 40 60 80 100 120 40 20 0 20 40 60 80 100 120 FIGURE 31 Vout LOW vs TEMPERATURE TEMPERATURE C V4 V 2 5V R 100k OUTPUT SHORT CIRCUIT CURRENT TEMPERATURE C FIGURE 32 OUTPUT SHORT CIRCUIT CURRENT vs TEMPERATURE Vin 2 5V RL 10 V4 V 2 5V 20 40 60 80 100 120 TEMPERATURE C FIGURE 33 OUTPUT SHORT CIRCUIT CURRENT vs TEMPERATURE Vy 2 5V RL 10 V4 V 2 5V Pin Descriptions ISL28288 ISL28488 EQUIVALENT 10 LD MSOP 16 LD QSOP PIN NAME CIRCUIT DESCRIPTION 1 3 IN _A Circuit 1 Amplifier A non inverting input 2 EN_A Circuit 2 Amplifier A enable pin internal pull down Logic 1 selects the disabled state Logic O selects the enabled state 3 13 V Circuit 4 Negative power supply 4 EN B Circuit 2 Amplifier B enable pin with internal pull down Logic 1 selects the
9. 25 C Over temperature limits established by characterization and are not production tested FN6339 1 3 intersil June 28 2007 ISL28288 ISL28488 Typical Performance Curves v 5v v ov Vou 2 5V R Open FIGURE 1 FREQUENCY RESPONSE vs SUPPLY VOLTAGE 1 o Il Va V 2 5V YaN m 7 RES Ik LIHI pora V 1 2V RL 5 10k S V V 2 5V En 10k z n az 4 o 5 Vout 50mvp p Ay 1 6 3pF RE 0 Re INF 8 1k 10k 100k 1M 5M FREQUENCY Hz GAIN dB lt il I N 5 Ay 100 L RL 10kQ C 3pF F Re 100kQ 5 RG 1kQ 100 1k 10k FREQUENCY Hz 100k 1M FIGURE 2 FREQUENCY RESPONSE vs SUPPLY VOLTAGE
10. 1pVIDIV TIME 1s DIV FIGURE 9 0 1Hz TO 10Hz INPUT VOLTAGE NOISE 5 0 i V4 5VDC 15 Vour 2Vp p Vout i RL 1kO Ay 2 3 0 2 0 1 0 Vin 0 0 50 100 150 200 250 TIME us FIGURE 11 LARGE SIGNAL TRANSIENT RESPONSE VOLTS V 1VIDIV 0 1VIDIV 1k S I Z Z 100 uy o Oo L L LA LL EEBEL E ELTE CELL CT EET z uy Q 10 5 9 gt 1 1 10 100 1k 10k 100k FREQUENCY Hz FIGURE 8 VOLTAGE NOISE vs FREQUENCY 2 56 VIN 2 54 k 2 52 2 50 2 48 V 5VDC Zap Vout 0 1Vp p RL lt 1kQ 2 44 L Av 1 2 42 E p 0 2 4 6 8 10 12 14 16 TIME us 18 20 FIGURE 10 SMALL SIGNAL TRANSIENT RESPONSE EN T A INPUT Vin 200mVp p VL SRV J V 0V Vout 10us DIV FIGURE 12 ENABLE TO OUTPUT DELAY TIME 5 intersil FN6339 1 June 28 2007 ISL28288 ISL28488 Typical Performance Curves v 5v V 0V Vem 2 5V RL Open Continued
11. W c A B A D N 2 1 N E Lll C E El PIN 1 I D T m B N 2 ATING __ Y PLANE M Ajo 1o c b gt 0 08 MICA N LEADS i y SEE DETAIL X fe 0 25 DETAIL X All Intersil U S products are manufactured assembled and tested utilizing ISO9000 quality systems MDP0043 MINI SO PACKAGE FAMILY MILLIMETERS SYMBOL MSOP8 MSOP10 TOLERANCE NOTES A 1 10 1 10 Max Al 0 10 0 10 0 05 A2 0 86 0 86 0 09 b 0 33 0 23 0 07 0 08 C 0 18 0 18 0 05 D 3 00 3 00 0 10 13 E 4 90 4 90 0 15 E1 3 00 3 00 0 10 2 3 e 0 65 0 50 Basic L 0 55 0 55 0 15 L1 0 95 0 95 Basic N 8 10 Reference Rev D 2 07 NOTES 1 Plastic or metal protrusions of 0 15mm maximum per side are not included 2 Plastic interlead protrusions of 0 25mm maximum per side are not included 3 Dimensions D and E1 are measured at Datum Plane H 4 Dimensioning and tolerancing per ASME Y14 5M 1994 Intersil Corporation s quality certifications can be viewed at www intersil com design quality Intersil products are sold by description only Intersil Corporation reserves the right to make changes in circuit design software and or specifications at any time without notice Accordingly the reader is cautioned to verify that data sheets are current
12. 0X gain The ISL28288 s rail to rail input characteristic allows the thermocouple to be biased at ground and the amplifier to run from a single 5V supply m ma ISL28X83 gt 410pVI C K TYPE THERMOCOUPLE 100kQ FIGURE 36 THERMOCOUPLE AMPLIFIER Current Limiting The ISL28288 has no internal current limiting circuitry If the output is shorted it is possible to exceed the Absolute Maximum Rating for output current or power dissipation potentially resulting in the destruction of the device Power Dissipation It is possible to exceed the 150 C maximum junction temperatures under certain load and power supply conditions It is therefore important to calculate the maximum junction temperature TMAX for all applications to determine if power supply voltages load conditions or package type need to be modified to remain in the safe Operating area These parameters are related in Equation 1 T T JMAX Tmax 63aXPDuaxTOTAL EQ 1 where PpMAXTOTAL is the sum of the maximum power dissipation of each amplifier in the package PDMAx PDmax for each amplifier is calculated in Equation 2 V OUTMAX _ max Vs lsyax Vs Youtmax R PD EQ 2 where Tmax Maximum ambient temperature 03A Thermal resistance of the package PDmax Maximum power dissipation of 1 amplifier Vs Supply voltage Magnitude of V and V Imax Maximum supply current of 1 amplifier VouT
13. MAX Maximum output voltage swing of the application RL Load resistance 11 intersil FN6339 1 June 28 2007 ISL28288 ISL28488 Quarter Size Outline Plastic Packages Family QSOP A MDP0040 D QUARTER SIZE OUTLINE PLASTIC PACKAGES FAMILY N 2 1 INCHES SYMBOL QSOP16 QSOP24 QSOP28 TOLERANCE NOTES A 0 068 0 068 0 068 Max E El A1 0 006 0 006 0 006 0 002 Y A2 0 056 0 056 0 056 0 004 b 0 010 0 010 0 010 0 002 N 2 C 0 008 0 008 0 008 0 001 B g D 0 193 0 341 0 390 0 004 1 3 40 010 C A B E 0 236 0 236 0 236 0 008 H E1 0 154 0 154 0 154 0 004 2 3 e 0 025 0 025 0 025 Basic 7 L 0 025 0 025 0 025 0 009 x L1 0 041 0 041 0 041 Basic 0 004 c 0 0079 C A B e b N 16 24 28 Reference Rev F 2 07 L1 NOTES 1 Plastic or metal protrusions of 0 006 maximum per side are not L A included Lt A P E 2 Plastic interlead protrusions of 0 010 maximum per side are not included SEE DETAILS Xx 3 Dimensions D and El are measured at Datum Plane H 4 Dimensioning and tolerancing per ASME Y14 5M 1994 DETAIL X 12 intersil FN6339 1 June 28 2007 ISL28288 ISL28488 Mini SO Package Family MSOP lt 0 25
14. N6339 1 June 28 2007 ISL28288 ISL28488 Typical Performance Curves v 5v v 0v Ven 2 5V RL Open Continued 500 200 n 1000 n 1000 0 0 200 go 400 MAX ri MAX dj 1000 600 lt lt m Mm 800 ES MEDIAN MEDIAN 1000 2000 1200 MIN MIN 2500 1400 20 0 20 40 60 80 100 120 40 20 0 20 40 60 80 100 120 TEMPERATURE C TEMPERATURE C FIGURE 19 Ig as vs TEMPERATURE V4 V 2 5V FIGURE 20 IgiAs VS TEMPERATURE V4 V 2 5V 500 T 200 T n 1000 n 1000 0 0 200 _ 500 E MAX 400 MAX 1000 D 5 E 600 1500 MEDIAN 800 MEDIAN 2000 1000 MIN MIN 2500 1200 40 20 0 20 40 60 80 100 120 40 20 0 20 40 60 80 100 120 TEMPERATURE C TEMPERATURE C FIGURE 21 Ig as vs TEMPERATURE V4 V 1 2V FIGURE 22 Igjas vs TEMPERATURE V4 V 1 2V 650 600 n 1000 MAX 550 500 E 450 E Z o 400 9 MEDIAN lt 350 LLLI MEDIAN 300 250 200 L o E tr A MIN 40 20 0 20 40 60 80 100 120 040 20 0 20 40 60 80 100 120 TEMPERATURE C TEMPERATURE C FIGURE 23 los vs TEMPERATURE V4 V 2 5V FIGURE 24 Ayo vs TEMPERATURE V4 V
15. ailable RoHS compliant Applications Battery or solar powered systems 4mA to 25mA current loops Handheld consumer products Medical devices Thermocouple amplifiers Photodiode pre amps pH probe amplifiers Ordering Information PART NUMBER PART PACKAGE PKG DWG Note MARKING Pb Free ISL28288FUZ 8288Z 10 Ld MSOP MDP0043 ISL28288FUZ T7 8288Z 10 Ld MSOP MDP0043 ISL28488FAZ 28488 FAZ 16 Ld QSOP MDP0040 ISL28488FAZ T7 28488 FAZ 16 Ld QSOP MDP0040 T7 suffix is for tape and reel Please refer to TB347 for details on reel specifications NOTE Intersil Pb free plus anneal products employ special Pb free material sets molding compounds die attach materials and 10096 matte tin plate termination finish which are RoHS compliant and compatible with both SnPb and Pb free soldering operations Intersil Pb free products are MSL classified at Pb free peak reflow temperatures that meet or exceed the Pb free requirements of IPC JEDEC J STD 020 1 CAUTION These devices are sensitive to electrostatic discharge follow proper IC Handling Procedures 1 888 INTERSIL or 1 888 468 3774 Intersil and design is a registered trademark of Intersil Americas Inc Copyright Intersil Americas Inc 2006 2007 All Rights Reserved All other trademarks mentioned are the property of their respective owners ISL28288 ISL28488 Absolute Maximum Ratings Ta 25 C Thermal Information
16. before placing orders Information furnished by Intersil is believed to be accurate and reliable However no responsibility is assumed by Intersil or its subsidiaries 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 Intersil or its subsidiaries For information regarding Intersil Corporation and its products see www intersil com 13 intersil FN6339 1 June 28 2007
17. disabled state Logic O selects the enabled state 5 5 INT B Circuit 1 Amplifier B non inverting input 6 6 IN B Circuit 1 Amplifier B inverting input 7 7 OUT B Circuit 3 Amplifier B output 8 4 V Circuit 4 Positive power supply 9 1 OUT_A Circuit 3 Amplifier A output 10 2 IN _A Circuit 1 Amplifier A inverting input 9 intersil FN6339 1 June 28 2007 ISL28288 ISL28488 Pin Descriptions continued ISL28288 ISL28488 EQUIVALENT 10 LD MSOP 16 LD QSOP PIN NAME CIRCUIT DESCRIPTION 10 OUT C Circuit 3 Amplifier C output 11 IN C Circuit 1 Amplifier C inverting input 12 IN C Circuit 1 Amplifier C non inverting input 14 IN D Circuit 1 Amplifier D non inverting input 15 IN D Circuit 1 Amplifier D inverting input 16 OUT D Circuit 3 Amplifier D output 8 9 NC No internal connection V V V 7 CAPACITIVELY IN IN Lodig OUT COUPLED ESD CLAMP v V V CIRCUIT 1 CIRCUIT 2 CIRCUIT 3 CIRCUIT 4 Applications Information Introduction The ISL28288 and ISL28488 are dual and quad CMOS rail to rail input output RRIO micropower operational amplifiers These devices are designed to operate from a single supply 2 4V to 5 0V or dual supplies 1 2V to 2 5V while drawing only 120uA of supply current This combination of low power and precision performance makes these devices suitable for solar and battery power applications Rail to Rail Input Ma
18. e input as shown in Figure 34 V FIGURE 34 PREVENTING OSCILLATIONS IN UNUSED CHANNELS Proper Layout Maximizes Performance To achieve the maximum performance of the high input impedance and low offset voltage of the ISL28288 care should be taken in the circuit board layout The PC board surface must remain clean and free of moisture to avoid leakage currents between adjacent traces Surface coating of the circuit board will reduce surface moisture and provide a humidity barrier reducing parasitic resistance on the board When input leakage current is a concern the use of guard rings around the amplifier inputs will further reduce leakage currents Figure 35 shows a guard ring example for a unity gain amplifier that uses the low impedance amplifier output at the same voltage as the high impedance input to eliminate surface leakage The guard ring does not need to be a specific width but it should form a continuous loop around both inputs For further reduction of leakage currents components can be mounted to the PC board using Teflon standoff insulators HIGH IMPEDANCE INPUT FIGURE 35 GUARD RING EXAMPLE FOR UNITY GAIN AMPLIFIER Example Application Thermocouples are the most popular temperature sensing device because of their low cost interchangeability and ability to measure a wide range of temperatures The ISL28288 Figure 36 is used to convert the differential thermocouple voltage into single ended signal with 1
19. ny rail to rail input stages use two differential input pairs a long tail PNP or PFET and an NPN or NFET Severe penalties have to be paid for this circuit topology As the input signal moves from one supply rail to another the operational amplifier switches from one input pair to the other causing drastic changes in input offset voltage and an undesired change in magnitude and polarity of input offset current The ISL28288 achieves input rail to rail without sacrificing important precision specifications and degrading distortion performance The devices input offset voltage exhibits a smooth behavior throughout the entire common mode input range The input bias current versus the common mode voltage range gives us an undistorted behavior from typically 100mV below the negative rail and 10 higher than the V rail 0 5V higher than V when V equals 5V Input Protection All input terminals have internal ESD protection diodes to both positive and negative supply rails limiting the input voltage to within one diode beyond the supply rails There is an additional pair of back to back diodes across the input terminals For applications where the input differential voltage is expected to exceed 0 5V external series resistors must be used to ensure the input currents never exceed 5mA Rail to Rail Output A pair of complementary MOSFET devices are used to achieve the rail to rail output swing The NMOS sinks current to swing the outp
20. ut in the negative direction The PMOS sources current to swing the output in the positive direction The ISL28288 with a 100kQ load will swing to within 4mV of the positive supply rail and within 3mV of the negative supply rail Enable Disable Feature The ISL28288 offers an EN pin that disables the device when pulled up to at least 2 0V In the disabled state output in a high impedance state the part consumes typically 4A By disabling the part multiple ISL28288 parts can be connected together as a MUX In this configuration the outputs are tied together in parallel and a channel can be selected by the EN pin The loading effects of the feedback resistors of the disabled amplifier must be considered when multiple amplifier outputs are connected together The EN pin also has an internal pull down If left open the EN pin will pull to the negative rail and the device will be enabled by default Using Only One Channel The ISL28288 is a dual op amp If the application only requires one channel the user must configure the unused channel to prevent it from oscillating The unused channel will oscillate if the input and output pins are floating This will result in higher than expected supply currents and possible 10 intersil FN6339 1 June 28 2007 ISL28288 ISL28488 noise injection into the channel being used The proper way to prevent this oscillation is to short the output to the negative input and ground the positiv
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intersil ISL28288 ISL28488 handbook