ELECTRICAL CHARACTERISTICSBoldface limits apply over the specified temperature range, T = –5°C to +75°C.AAt T = +25°C, V = ±5V, and R = 10kΩ , unless otherwise noted.A S OUTLOG112, LOG2112PARAMETER CONDITION MIN TYP MAX UNITSCORE LOG FUNCTIONV /V Equation V = (0.5V)LOG (I /I)VIN OUT LOGOUT 1 2(1)LOG CONFORMITY ERRORInitial 1nA to 100µ A (5 decades) 0.01 0.2 %100pA to 3.5mA (7.5 decades) 0.13 %over Temperature 1nA to 100µ A (5 decades) 0.0001 %/°C100pA to 3.5mA (7.5 decades) 0.005 %/°C(2)GAINInitial Value 1nA to 100µ A 0.5 V/decadeGain Error 1nA to 100µ A 0.10 ±1%vs Temperature T to T 0.003 0.01 %/°CMIN MAXINPUT, A and A , A , A1A 1B 2A 2BOffset Voltage ±0.3 ±1.5 mVvs Temperature T to T ±2 µ V/°CMIN MAXvs Power Supply (PSRR) V = ±4.5V to ±18V 5 20 µ V/VSInput Bias Current ±5pAvs Temperature T to T Doubles Every 10°CMIN MAXVoltage Noise f = 10Hz to 10kHz 3 µ Vrmsf = 1kHz 30 nV/√HzCurrent Noise f = 1kHz 4 fA/√HzCommon-Mode Voltage Range (Positive) (V+) – 2 (V+) – 1.5 V(Negative) (V–) + 2 (V–) + 1.2 VCommon-Mode Rejection Ratio (CMRR) 10 µ V/VOUTPUT, (V ) A , ALOG OUT 2A 2BOutput Offset, V , Initial ±3 ±15 mVOSOvs Temperature T to T ±10 µ V/°CMIN MAXFull-Scale Output (FSO) V = ±5V (V–) + 1.2 (V+) – 1.5 VSShort-Circuit Current ±18 mA(3)(4)TOTAL ERROR I or I remains fixed while other varies.1 2Initial Min to MaxI or I = 5mA (V ≥ ±6V) ±150 mV1 2 SI or I = 3.5mA ±75 mV1 2I or I = 1mA ±20 mV1 2I or I = 100µ A ±20 mV1 2I or I = 10µ A ±20 mV1 2I or I = 1µ A ±20 mV1 2I or I = 100nA ±20 mV1 2I or I = 10nA ±20 mV1 2I or I = 1nA ±20 mV1 2I or I = 350pA ±20 mV1 2I or I = 100pA ±20 mV1 2vs Temperature I or I = 3.5mA ±1.2 mV/°C1 2I or I = 1mA ±0.4 mV/°C1 2I or I = 100µ A ±0.1 mV/°C1 2I or I = 10µ A ±0.05 mV/°C1 2I or I = 1µ A ±0.05 mV/°C1 2I or I = 100nA ±0.09 mV/°C1 2I or I = 10nA ±0.2 mV/°C1 2I or I = 1nA ±0.3 mV/°C1 2I or I = 350pA ±0.1 mV/°C1 2I or I = 100pA ±0.3 mV/°C1 2vs Supply I or I = 3.5mA ±3.0 mV/V1 2I or I = 1mA ±0.1 mV/V1 2I or I = 100µ A ±0.1 mV/V1 2I or I = 10µ A ±0.1 mV/V1 2I or I = 1µ A ±0.1 mV/V1 2I or I = 100nA ±0.1 mV/V1 2I or I = 10nA ±0.1 mV/V1 2I or I = 1nA ±0.25 mV/V1 2I or I = 350pA ±0.1 mV/V1 2I or I = 100pA ±0.1 mV/V1 2NOTES: (1) Log Conformity Error is the peak deviation from the best-fit-straight line of V versus LOG (I /I ) curve expressed as a percent of peak-to-peak full-O 1 2scale output. K, scale factor, equals 0.5V output per decade of input current. (2) Scale factor of core log function is trimmed to 0.5V output per decade change ofinput current. (3) Worst-case Total Error for any ratio of I /I , as the largest of the two errors, when I and I are considered separately. (4) Total Error includes offset1 2 1 2voltage, bias current, gain, and log conformity. (5) Bandwidth (3dB) and transient response are a function of both the compensation capacitor and the level of inputcurrent.LOG112, 21123SBOS246Dfeatures a 2.5V voltage refer-7.5 Decades, 100pA to 3.5mAence that may be used to generate a precision current* LOW QUIESCENT CURRENT: 1.75mAreference using an external resistor.* WIDE SUPPLY RANGE: ±4.5V to ±18VLow DC offset voltage and temperature drift allow accurate* PACKAGES: SO-14 (narrow) and SO-16measurement of low-level signals over the specified tem-perature range of –5°C to +75°C.APPLICATIONS* LOG, LOG RATIO:Communication, Analytical, Medical, Industrial,Test, General Instrumentation* PHOTODIODE SIGNAL COMPRESSION AMP* ANALOG SIGNAL COMPRESSION IN FRONTOF ANALOG-TO-DIGITAL (A/D) CONVERTER* ABSORBANCE MEASUREMENT* OPTICAL DENSITY MEASUREMENTR R1 2V = (0.5V)LOG (I /I )LOGOUT 1 2CCV = K (0.5V)LOG (I /I ), K = 1 + R /RO3 1 2 2 1+IN3V+ –IN3VLOGOUTI1LOG112Q Q1 2A A1 2I2RREFAV3O3VREFVREFGNDVV V–REF – GND CMNOTE: Internal resistors are used to compensate gain change over temperature.The V pin is internally connected to GND in the LOG2112.CMPlease be aware that an important notice concerning availability, standard warranty, and use in critical applications ofTexas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.All trademarks are the property of their respective owners..Copyright 2002-2005, Texas Instruments IncorporatedProducts conform to specifications per the terms of Texas Instrumentsstandard warranty. Production processing does not necessarily includetesting of all parameters.ELECTRICAL CHARACTERISTICS (Cont.)Boldface limits apply over the specified temperature range, T = –5°C to +75°C.AAt T = +25°C, V = ±5V, and R = 10kΩ , unless otherwise noted.A S LLOG112, LOG2112PARAMETER CONDITION MIN TYP MAX UNITS(5)FREQUENCY RESPONSE, CORE LOGBW, 3dBI = 10nA C = 4500pF 0.1 kH2 CI = 1µAC = 150pF 38 kH2 CI = 10µAC = 150pF 40 kH2 CI = 1mA C = 50pF 45 kHz2 CStep ResponseIncreasingI = 10nA to 100nA C = 120pF, I = 31.6nA 1.1 ms1 C 2I = 1µ A to 100µAC = 375pF, I = 10µ A 1.6 µ s1 C 2I = 1µ A to 1mA C = 950pF, I = 31.6µ A 1.5 µ s1 C 2DecreasingI = 100nA to 10nA C = 120pF, I = 31.6nA 2.1 ms1 C 2I = 100µ A to 1µAC = 375pF, I = 10µ A 31.2 µ s1 C 2I = 1mA to 1µAC = 950pF, I = 31.6µA39 µ s1 C 2IncreasingI = 10nA to 100nA C = 125pF, I = 31.6nA 2.6 ms2 C 1I = 1µ A to 100µAC = 750pF, I = 10µ A 113 µ s2 C 1I = 1µ A to 1mA C = 10.5nF, I = 31.6µ A 1.2 ms2 C 1DecreasingI = 100nA to 10nA C = 125pF, I = 31.6nA 630 µ s2 C 1I = 100µ A to 1µAC = 750pF, I = 10µ A 6.6 µ s2 C 1I = 1mA to 1µAC = 10.5nF, I = 31.6µ A 13.3 µ s2 C 1OP AMP, A3Input Offset Voltage +250 ±1000 µ Vvs Temperature T to T ±2 µ V/°CMIN MAXvs Supply V = ±4.5V to ±18V 5 50 µ V/VSInput Bias Current –10 nAInput Offset Current ±0.5 nAInput Voltage Range (V–) (V+) – 1.5 VInput Noise, f = 0.1Hz to 10Hz 1 µ VPP√Hz f = 1kHz 28 nV/Open-Loop Voltage Gain 88 dBGain-Bandwidth Product 1.4 MHzSlew Rate 0.5 V/µ sSettling Time, 0.01% G = –1, 3V Step, C = 100pF 16 µ sLRated Output (V–) + 1.5 (V+) – 0.9 VShort-Circuit Current ±4mAVOLTAGE REFERENCEBandgap Voltage 2.5 VError, Initial ±0.05 ±0.5 %vs Temperature T to T ±25 ppm/°CMIN MAXvs Supply V = ±4.5V to ±18V ±10 ppm/VSvs Load I = 10mA ±600 ppm/mALOADShort-Circuit Current 16 mAPOWER SUPPLYOperating Range V ±4.5 ±18 VSQuiescent Current I = 0OLOG112 ±1.25 ±1.75 mALOG2112 ±2.5 ±3.5 mATEMPERATURE RANGESpecified Range, T to T –575 °CMIN MAXOperating Range –40 85 °CStorage Range –55 125 °CThermal Resistance, θ SO-14 110 °C/WJASO-16 80 °C/WNOTES: (1) Log Conformity Error is the peak deviation from the best-fit-straight line of V vs LOG(I /I ) curve expressed as a percent of peak-to-peak full-scaleO 1 2output. K, scale factor, equals 0.5V output per decade of input current. (2) Scale factor of core log function is trimmed to 0.5V output per decade change of inputcurrent. (3) Worst-case Total Error for any ratio of I /I , as the largest of the two errors, when I and I are considered separately. (4) Total Error includes offset1 2 1 2voltage, bias current, gain, and log conformity. (5) Bandwidth (3dB) and transient response are a function of both the compensation capacitor and the level of inputcurrent.LOG112, 21124SBOS246D |