LT1366/LT1367 LT1368/LT1369 Dual and Quad Precision Rail-to-Rail Input and Output Op Amps. Applications. Typical Application

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1 Features n Input Common Mode Range Incudes Both Rais n Output Swings Rai-to-Rai n Low Input Offset otage: 5 n High Common Mode Rejection Ratio: 9 n High A OL : >/ Driving k Load n Low Input Bias Current: n Wide Suppy Range:.8 to ±5 n Low Suppy Current: 375µA per Ampifier n High Output Drive: 3mA n 4kHz Gain-Bandwidth Product n Sew Rate:.3/µs n Stabe for Capacitive Loads Up to pf Appications n Rai-to-Rai Buffer Ampifiers n Low otage Signa Processing n Suppy Current Sensing at Either Rai n Driving A/D Converters L, LT, LTC, LTM, Over-The-Top, Linear Technoogy and the Linear ogo are registered trademarks and C-Load is a trademark of Linear Technoogy Corporation. A other trademarks are the property of their respective owners. LT366/LT367 Dua and Quad Precision Rai-to-Rai Input and Output Op Amps Description The LT 366/LT367/ are dua and quad bipoar op amps which combine rai-to-rai input and output operation with precision specifications. These op amps maintain their characteristics over a suppy range of.8 to 36. Operation is specified for 3, 5 and ±5 suppies. Input offset votage is typicay 5, with an open-oop gain A OL of miion whie driving a k oad. Common mode rejection is typicay 9 over the fu rai-to-rai input range, and suppy rejection is. The LT366/LT367 have conventiona compensation which assures stabiity for capacitive oads of pf or ess. The have compensation that requires a.µf output capacitor, which improves the ampifier s suppy rejection and reduces output impedance at high frequencies. The output capacitor s fitering action reduces high frequency noise, which is beneficia when driving A/D converters. The LT366/LT368 are avaiabe in pastic 8-pin PDIP and 8-ead SO packages with the standard dua op amp pinout. The LT367/LT369 feature the standard quad pinout, which is avaiabe in a pastic 4-ead SO package. These devices can be used as pug-in repacements for many standard op amps to improve input/output range and precision. Typica Appication Positive Suppy Rai Current Sense Output Saturation otage vs Load Current CC LOAD R 2Ω Rs.2Ω I LOAD /2 LT366 R2 2k Q TP6L /2 LT366 R2 O = I LOAD R S ( R ) = I LOAD 2Ω 366 TA SATURATION OLTAGE (m) OUT S POSITIE RAIL NEGATIE RAIL... LOAD CURRENT (ma) 366 TA2

2 LT366/LT367 Absoute Maximum Ratings (Note ) Tota Suppy otage ( to ) Input Current... ±5mA Output Short-Circuit Duration (Note 2)... Continuous Operating Temperature Range... 4 C to 85 C Specified Temperature Range... C to 7 C Junction Temperature... 5 C Storage Temperature Range C to 5 C Lead Temperature (Sodering, sec)... 3 C Pin Configuration LT366/LT368 LT367/LT369 OUT A IN A IN A A TOP IEW OUT B IN B IN B N8 PACKAGE 8-LEAD PDIP S8 PACKAGE 8-LEAD PLASTIC SO T JMAX = 5 C, θ JA = 3 C/W (N8) T JMAX = 5 C, θ JA = 9 C/W (S8) B OUT A IN A 2 IN A 3 4 IN B 5 IN B 6 OUT B 7 A B TOP IEW D 4 OUT D 3 IN D 2 IN D IN C 9 IN C 8 OUT C S PACKAGE 4-LEAD PLASTIC SO T JMAX = 5 C, θ JA = 5 C/W C AAILABLE OPTIONS MAX OS (25 C) ORDER PART NUMBER PRODUCT NUMBER NUMBER OF OP AMPS LOAD CAPACITANCE AT S = 5, PLASTIC (N) SURFACE MOUNT(S) LT366 2 pf < C L < pf 475 LT366CN8 LT366CS8 LT367 4 pf < C L < pf 8 LT367CS LT368 2 C L =.µf 475 LT368CN8 LT368CS8 LT369 4 C L =.µf 8 LT369CS Order Information LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE LT366CN8#PBF LT366CN8#TRPBF Lead PDIP C to 7 C LT366CS8#PBF LT366CS8#TRPBF Lead Pastic S C to 7 C LT367CS#PBF LT367CS#TRPBF LT367CS 4-Lead Pastic S C to 7 C LT368CN8#PBF LT368CN8#TRPBF Lead PDIP C to 7 C LT368CS8#PBF LT368CS8#TRPBF Lead Pastic S C to 7 C LT369CS#PBF LT369CS#TRPBF LT369CS 4-Lead Pastic S C to 7 C Consut LTC Marketing for parts specified with wider operating temperature ranges. Consut LTC Marketing for information on non-standard ead based finish parts. For more information on ead free part marking, go to: For more information on tape and ree specifications, go to:

3 LT366/LT367 Eectrica Characteristics T A = 25 C; S = 5, ; CM = 2.5; O = 2.5, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS OS Input Offset otage (LT366/LT368) CM = CC 5 CM = EE 5 Input Offset otage (LT367/LT369) CM = CC 5 CM = EE 5 OS Input Offset otage Shift (LT366/LT368) Input Offset otage Match (Channe to Channe) Input Offset otage Shift (LT367/LT369) Input Offset otage Match (Channe to Channe) CM = EE to CC CM = EE, CC (Notes 4, 5) CM = EE to CC CM = EE, CC (Notes 4, 5) I B Input Bias Current CM = CC CM = EE 35 I B Input Bias Current Shift CM = EE to CC 2 7 I OS Input Offset Current CM = CC CM = EE.3 I OS Input Offset Current Shift CM = EE to CC 2 Input Bias Current Match (Channe to Channe) CM = CC (Note 4) CM = EE (Note 4) e n Input Noise otage Density f = khz 29 n/ Hz i n Input Noise Current Density f = khz.7 pa/ Hz C IN Input Capacitance 2 pf A OL Large-Signa otage Gain O = 5m to 4.8, R L = k 25 2 /m CMRR Common Mode Rejection Ratio (LT366/LT368) CMRR Match (Channe to Channe) CM = EE to CC CM = EE to CC (Note 4) PSRR Common Mode Rejection Ratio (LT367/LT369) CMRR Match (Channe to Channe) Power Suppy Rejection Ratio PSRR Match (Channe to Channe) (Note 4) OL Output otage Swing Low No Load I SINK =.5mA I SINK = 2.5mA OH Output otage Swing High No Load I SINK =.5mA I SINK = 2.5mA CM = EE to CC CM = EE to CC (Note 4) S = 2. to 2, CM = O =.5 S = 2. to 2, CM = O = CC.2 CC. CC CC.4 CC.5 CC.5 I SC Short-Circuit Current (Note 2) ±5 ±3 ma I S Suppy Current per Ampifier µa GBW Gain-Bandwidth Product (LT366/LT367) Gain-Bandwidth Product () A = A =.4.6 MHz MHz t S Setting Time (LT366/LT367) A =, STEP = 4 to.% 3 µs m m m

4 LT366/LT367 Eectrica Characteristics The denotes the specifications which appy over the specified temperature range of C < T A < 7 C. S = 5, ; CM = 2.5, O = 2.5, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS OS Input Offset otage (LT366/LT368) CM = CC CM = EE Input Offset otage (LT367/LT369) CM = CC CM = EE OS TC Input Offset otage Drift (Note 3) 2 6 / C OS Input Offset otage Shift (LT366/LT368) CM = EE to CC Input Offset otage Match (Channe to Channe) CM = EE, CC (Notes 4, 5) 25 9 Input Offset otage Shift (LT367/LT369) Input Offset otage Match (Channe to Channe) CM = EE to CC CM = EE, CC (Notes 4, 5) I B Input Bias Current CM = CC CM = EE 45 I B Input Bias Current Shift CM = EE to CC 25 9 I OS Input Offset Current CM = CC 2 5 CM = EE 5 I OS Input Offset Current Shift CM = EE to CC 2 5 Input Bias Current Match (Channe to Channe) CM = CC (Note 4) CM = EE (Note 4) A OL Large-Signa otage Gain O = 5m to 4.8, R L = k 25 2 /m CMRR Common Mode Rejection Ratio (LT366/LT368) CM = EE to CC 8 87 CMRR Match (Channe to Channe) CM = EE to CC (Note 4) PSRR Common Mode Rejection Ratio (LT367/LT369) CMRR Match (Channe to Channe) Power Suppy Rejection Ratio PSRR Match (Channe to Channe) (Note 4) CM = EE to CC CM = EE to CC (Note 4) S = 2.3 to 2, CM = O =.5 S = 2.3 to 2, CM = O =.5 OL Output otage Swing Low No Load I SINK =.5mA I SINK = 2.5mA OH Output otage Swing High No Load I SOURCE =.5mA I SOURCE = 2.5mA CC.4 CC. CC CC.5 CC.55 CC.8 I SC Short-Circuit Current (Note 2) ±2.5 ma I S Suppy Current per Ampifier µa T A = 25 C; S = 3, ; CM =.5; O =.5, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS OS Input Offset otage (LT366/LT368) CM = CC 5 CM = EE 5 Input Offset otage (LT367/LT369) CM = CC 5 CM = EE 5 OS Input Offset otage Shift (LT366/LT368) Input Offset otage Match (Channe to Channe) Input Offset otage Shift (LT367/LT369) Input Offset otage Match (Channe to Channe) CM = EE to CC CM = EE, CC (Notes 4, 5) CM = EE to CC CM = EE, CC (Notes 4, 5) I B Input Bias Current CM = CC CM = EE 35 I B Input Bias Current Shift CM = EE to CC 2 7 I OS Input Offset Current CM = CC. CM = EE m m m

5 LT366/LT367 Eectrica Characteristics T A = 25 C; S = 3, ; CM =.5; O =.5, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I OS Input Offset Current Shift CM = EE to CC 2 Input Bias Current Match (Channe to Channe) CM = CC (Note 4) CM = EE (Note 4) A OL Large-Signa otage Gain O = 5m to 2.8, R L = k 25 5 /m CMRR Common Mode Rejection Ratio (LT366/LT368) CM = EE to CC CMRR Match (Channe to Channe) CM = EE to CC (Note 4) 7 86 Common Mode Rejection Ratio (LT367/LT369) CMRR Match (Channe to Channe) CM = EE to CC CM = EE to CC (Note 4) OL Output otage Swing Low No Load I SINK =.5mA I SINK = 2.5mA OH Output otage Swing High No Load I SINK =.5mA I SINK = 2.5mA CC.2 CC. CC CC.4 CC.5 CC.5 I SC Short-Circuit Current (Note 2) ± ±2 ma I S Suppy Current per Ampifier 33 5 µa The denotes the specifications which appy over the specified temperature range of C < T A < 7 C. S = 3, ; CM =.5, O =.5, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS OS Input Offset otage (LT366/LT368) CM = CC CM = EE Input Offset otage (LT367/LT369) CM = CC CM = EE OS Input Offset otage Shift (LT366/LT368) Input Offset otage Match (Channe to Channe) Input Offset otage Shift (LT367/LT369) Input Offset otage Match (Channe to Channe) CM = EE to CC CM = EE, CC (Notes 4, 5) CM = EE to CC CM = EE, CC (Notes 4, 5) OS TC Input Offset otage Drift (Note 3) 2 6 / C I B Input Bias Current CM = CC CM = EE I B Input Bias Current Shift CM = EE to CC 25 9 I OS Input Offset Current CM = CC CM = EE I OS Input Offset Current Shift CM = EE to CC 2 5 Input Bias Current Match (Channe to Channe) CM = CC (Note 4) CM = EE (Note 4) A OL Large-Signa otage Gain O = 5m to 2.8, R L = k 5 5 /m CMRR Common Mode Rejection Ratio (LT366/LT368) CM = EE to CC CMRR Match (Channe to Channe) CM = EE to CC (Note 4) 7 83 Common Mode Rejection Ratio (LT367/LT369) CMRR Match (Channe to Channe) CM = EE to CC CM = EE to CC (Note 4) OL Output otage Swing Low No Load I SINK =.5mA I SINK = 2.5mA OH Output otage Swing High No Load I SOURCE =.5mA I SOURCE = 2.5mA CC.4 CC. CC CC.5 CC.55 CC.8 I SC Short-Circuit Current (Note 2) ± ma I S Suppy Current per Ampifier µa m m m m m m

6 LT366/LT367 Eectrica Characteristics T A = 25 C, S = ±5, CM =, O =, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS OS Input Offset otage (LT366/LT368) CM = CC 2 CM = EE 2 Input Offset otage (LT367/LT369) CM = CC 2 CM = EE 2 OS Input Offset otage Shift (LT366/LT368) Input Offset otage Match (Channe to Channe) Input Offset otage Shift (LT367/LT369) Input Offset otage Match (Channe to Channe) CM = EE to CC CM = EE, CC (Notes 4, 5) CM = EE to CC CM = EE, CC (Notes 4, 5) I B Input Bias Current CM = CC CM = EE 35 I B Input Bias Current Shift CM = EE to CC 2 7 I OS Input Offset Current CM = CC. CM = EE.3 I OS Input Offset Current Shift CM = EE to CC 2 Input Bias Current Match (Channe to Channe) CM = CC (Note 4) CM = EE (Note 4) C IN Input Capacitance 7. pf A OL Large-Signa otage Gain O = 4.7 to 4.7, R L = k O = to, R L = 2k Channe Separation O = to, R L = 2k 2 35 SR Sew Rate (LT366/LT367) A =, R L = Open, O = ±,.3 /µs Measured at O = ±5 Sew Rate () A =, R L = Open, O = ±,.65 /µs Measured at O = ±5 CMRR Common Mode Rejection Ratio (LT366/LT368) CMRR Match (Channe to Channe) CM = EE to CC CM = EE to CC (Note 4) PSRR Common Mode Rejection Ratio (LT367/LT369) CMRR Match (Channe to Channe) Power Suppy Rejection Ratio PSRR Match (Channe to Channe) CM = EE to CC CM = EE to CC (Note 4) S = ±5 to ±5 S = ±5 to ±5 (Note 4) OL Output otage Swing Low No Load I SINK =.5mA I SINK = ma OH Output otage Swing High No Load I SINK =.5mA I SINK = 2.5mA CC.2 CC. CC EE.6 EE.4 EE.24 CC.4 CC.5 CC EE.2 EE.7 EE.5 I SC Short-Circuit Current (Note 2) ±3 ±75 ma I S Suppy Current per Ampifier µa /m /m

7 LT366/LT367 Eec

8 LT366/LT367 Typica Performance Characteristics (The data presented here appies to the LT366/LT367/ uness otherwise noted.) 3 PNP Stage OS Distribution (LT366/LT368) NPN Stage OS Distribution (LT366/LT368) OS -Shift Between PNP and NPN Stages (LT366/LT368) INPUT OFFSET OLTAGE () LT366 TPC3 Suppy Current vs Temperature Suppy Current vs Suppy otage Input Bias Current vs Common Mode otage Input Bias Current vs Temperature Output Saturation otage vs Load Current (Output High) Output Saturation otage vs Load Current (Output Low)

9 LT366/LT367 Typica Performance Characteristics (The data presented here appies to the LT366/LT367/ uness otherwise noted.) CHANGE IN OFFSET OLTAGE () Minimum Suppy otage 2 5 T A = 7 C T A = 85 C 5 T A = 25 C T A = 55 C NONFUNCTIONAL OUTPUT OLTAGE (2n/DI).Hz to Hz Output otage Noise S = ±2.5 CM = NOISE OLTAGE n/ Hz Noise otage Spectrum S = 5, CM = 4 CM = TOTAL SUPPLY OLTAGE () 5 TIME (s/di) FREQUENCY (Hz) LT366 TPC LT366 TPC LT366 TPC2 CURRENT NOISE (pa/ Hz) Noise Current Spectrum S = 5, CM = 2.5 CM = 4 FREQUENCY (Hz) LT366 TPC3 OLTAGE GAIN () Gain and Phase Shift vs Frequency (LT366/LT367) S = ±2.5 GAIN PHASE 3 6 k k k M M FREQUENCY (Hz) LT366 TPC PHASE SHIFT (DEG) OLTAGE GAIN () Gain and Phase Shift vs Frequency () PHASE GAIN S = ±2.5 C L =.µf 5 6 k k k M M FREQUENCY (Hz) LT366 TPC PHASE SHIFT (DEG) COMMON MODE REJECTION RATIO () CMRR vs Frequency (LT366 and LT367) S = ±2.5 2 k k k M FREQUENCY (Hz) LT366 TPC6 POWER SUPPLY REJECTION RATIO () PSRR vs Frequency (LT366/LT367) S = ±2.5 NEGATIE SUPPLY POSITIE SUPPLY k k k M FREQUENCY (Hz) LT366 TPC7 POWER SUPPLY REJECTION RATIO () 8 PSRR vs Frequency () 2 S = ± POSITIE SUPPLY 2 NEGATIE SUPPLY k k k M FREQUENCY (Hz) LT366 TPC8

10 LT366/LT367 Typica Performance Characteristics (The data presented here appies to the LT366/LT367/ uness otherwise noted.) FREQUENCY (khz) Gain-Bandwidth and Phase Margin vs Suppy otage (LT366/LT367) Channe Separation vs Frequency Open-Loop Gain PHASE MARGIN GBW SUPPLY OLTAGE () PHASE MARGIN (DEG) CHANNEL SEPARATION () S = ±5 OUT = ± P-P R L = 2k LT366/LT367 5 k k FREQUENCY (Hz) INPUT OLTAGE () R L = 2k R L = k S = ± OUTPUT OLTAGE () 2 LT366 TPC9 LT366 TPC2 LT366 TPC2 OERSHOOT (%) Capacitive Load Handing (LT366/LT367) S = 5, A = A = 5 A = OERSHOOT (%) Overshoot vs Load Current () S = ±2.5 A = C L =.47µF C L =.22µF C L =.µf OERSHOOT (%) Overshoot vs Load Current () S = ±5 A = C L =.47µF C L =.22µF C L =.µf k k k CAPACITIE LOAD (pf) 5 5 LOAD CURRENT (ma) 5 5 LOAD CURRENT (ma) LT366 TPC22 LT366 TPC23 LT366 TPC24 SLEW RATE (/µs) Sew Rate vs Suppy otage.2 A = TOTAL SUPPLY OLTAGE () LT366 TPC25 CHANGE IN OFFSET OLTAGE () Warm-Up Drift vs Time S8 PACKAGE S = ±5 N8 PACKAGE S = ±5 S8 PACKAGE S = ±2.5 N8 PACKAGE S = ± TIME AFTER POWER-UP (SEC) LT366 TPC26 THD NOISE (%).. THD Noise vs Peak-to-Peak otage f = khz R L = k (ALL CURES) S = ±.5 A = S = ±2.5 A = S = ±.5 A = S = ±2.5 A = IN(P-P) () LT366 TPC27

11 LT366/LT367 Typica Performance Characteristics (The data presented here appies to the LT366/LT367/ uness otherwise noted.) THD Noise vs Frequency S = ±.5 IN = 2 P-P R L = k Large-Signa Response (LT366/LT367) Sma-Signa Response (LT366/LT367) THD NOISE (%).. A = A = 5/DI 5m/DI S = ±5 UNITY GAIN µs/di LT366 TPC29 S = ±5 UNITY GAIN 2µs/DI LT366 TPC3... FREQUENCY (khz) LT366 TPC28 Appications information Rai-to-Rai Operation The LT366 famiy differs from conventiona op amps in the design of both the input and output stages. Figure shows a simpified schematic of the ampifier. The input stage consists of two differentia ampifiers, a PNP stage Q/Q2 and an NPN stage Q3/Q4, which are active over different portions of the input common mode range. Latera devices are used in both input stages, eiminating the need for camps across the input pins. Each input stage is trimmed for offset votage. A compementary output configuration (Q23 through Q26) is empoyed to create an output stage with rai-to-rai swing. The ampifier is fabricated on Linear I Q D4 D5 Q7 D6 Q2 D7 Q24 Q Q23 Q5 Q6 C OUT IN IN 3m Q2 Q6 Q3 Q4 D Q D3 Q2 D2 Q7 Q8 Q9 Q3 C C Q4 Q5 D7 Q8 Q9 Q2 Q22 C2 Q25 Q26 D8 LT366 FO Figure. LT366 Simpified Schematic Diagram

12 LT366/LT367 Appications information Technoogy s proprietary compementary bipoar process, which ensures very simiar DC and AC characteristics for the output devices Q24 and Q26. A simpe comparator Q5 steers current from current source I between the two input stages. When the input common mode votage CM is near the negative suppy, Q5 is reverse biased, and I becomes the tai current for the PNP differentia pair Q/Q2. At the other extreme, when CM is within about.3 from the positive suppy, Q5 diverts I to the current mirror D3/Q6, which furnishes the tai current for the NPN differentia pair Q3/Q4. The coector currents of the two input pairs are combined in the second stage, consisting of Q7 through Q. Most of the votage gain in the ampifier is contained in this stage. Differentia ampifier Q4/Q5 buffers the output of the second stage, converting the output votage to differentia currents. The differentia currents pass through current mirrors D4/Q7 and D5/Q6, and are converted to differentia votages by Q8 and Q9. These votages are aso buffered and appied to the output Darington pairs Q23/Q24 and Q25/Q26. Capacitors C and C2 form oca feedback oops around the output devices, owering the output impedance at high frequencies. Input Offset otage Since the ampifier has two input stages, the input offset votage changes depending upon which stage is active. The input offsets are random, but bounded votages. When the ampifier switches between stages, offset votages may go up, down, or remain fat; but wi not exceed the guaranteed imits. This behavior is iustrated in three distribution pots of input offset votage in the Typica Performance Characteristics section. Overdrive Protection Two circuits prevent the output from reversing poarity when the input votage exceeds the common mode range. When the noninverting input exceeds the positive suppy by approximatey 3m, the camp transistor Q2 (Figure ) turns on, puing the output of the second stage ow, which forces the output high. For inputs beow the negative suppy, diodes D and D2 turn on, overcoming the saturation of the input pair Q/Q2. 2 When overdriven, the ampifier draws input current that exceeds the norma input bias current. Figures 2 and 3 show some typica overdrive currents as a function of input votage. The input current must be ess than ma of positive overdrive or ess than 7mA of negative overdrive, for the phase reversa protection to work propery. When the ampifier is severey overdriven, an externa resistor shoud be used to imit the overdrive current. In addition to overdrive protection, the ampifier is protected against ESD strokes up to 4k on a pins. INPUT BIAS CURRENT () 9 MEASURED AS A FOLLOWER 8 7 T = 25 C T = 85 C T = 55 C 3 T = 7 C S 3 5 COMMON MODE OLTAGE RELATIE TO POSITIE SUPPLY (m) LT366 F2 Figure 2. Input Bias Current vs Common Mode otage INPUT BIAS CURRENT () MEASURED AS A FOLLOWER T = 55 C T = 25 C T = 7 C 6 T = 85 C S 2 COMMON MODE OLTAGE RELATIE TO NEGATIE SUPPLY (m) LT366 F3 Figure 3. Input Bias Current vs Common Mode otage

13 LT366/LT367 Appications information Improved Suppy Rejection in the The are variations of the LT366/LT367 offering greater suppy rejection and ower high frequency output impedance. The require a.µf oad capacitance for compensation. The output capacitance forms a fiter, which reduces pickup from the suppy and owers the output impedance. This additiona fitering is hepfu in mixed anaog/digita systems with common suppies, or systems empoying switching suppies. Fitering aso reduces high frequency noise, which may be beneficia when driving A/D converters. Figure 4 shows the outputs of the LT366/LT368 perturbed by a 2m P-P 5kHz square wave added to the positive suppy. The LT368 s power suppy rejection is about ten times greater than that of the LT366 at 5kHz. Note the 5-to- scae change in the output votage traces. The toerance of the externa compensation capacitor is not critica. The pots of Overshoot vs Load Current in the Typica Performance Characteristics section iustrate the effect of a capacitive oad. (AC) m/di (AC) m/di OUT m/di OUT 2m/DI 2µs/DI LT366 F4a 2µs/DI LT366 F4b Figure 4a. LT366 Power Suppy Rejection Test Figure 4b. LT368 Power Suppy Rejection Test Typica Appications Buffering A/D Converters CC Figure 5 shows the LT368 driving an LTC channe micropower A/D converter (ADC). The LTC288 can accommodate votage references and input signas equa to the suppy rais. The samping nature of this ADC eiminates the need for an externa sampe-and-hod, but may ca for a drive ampifier because of the ADC s 2µs setting requirement. The LT368 s rai-to-rai operation and ow input offset votage make it we-suited for ow power, ow frequency A/D appications. Either the LT366 or LT368 coud be used for this appication. However, for ow frequencies (f < khz) the LT368 provides better suppy rejection. /2 LT368 /2 LT368.µF.µF.µF µf CS/SHDN CC (REF) CH CLK LTC288 CH D OUT GND D IN LT366 FO5 TO µp Figure 5. 2-Channe Low Power A/D Converter 3

14 LT366/LT367 TYPICAL APPLICATIONS Precision Low Dropout Reguator Microprocessors and compex digita circuits frequenty specify tight contro of power suppy characteristics. The circuit shown in Figure 6 provides a precise 3.6, A output from a minimum 3.8 input votage. The circuit s nomina operating votage is 4.75 ±5%. The votage reference and resistor ratios determine output votage accuracy, whie the LT366 s high gain enforces.2% ine and oad reguation. Quiescent current is about ma and does not change appreciaby with suppy or oad. A components are avaiabe in surface mount packages. The reguator s main oop consists of A and a ogic-eve FET, Q. The output is fed back to the op amp s positive input because of the phase inversion through Q. The reguator s frequency response is imited by Q s ro-off and the phase ead introduced by the output capacitor s effective series resistance (ESR). Two poe-zero networks compensate for these effects. The poe formed with R5 and C2 ros off the gain set with the feedback network, whie the poe formed with R7 and C3 ros off A s gain directy, which is the dominant infuence on setting time. The zeros formed with R6 and C2, and R8 and C3 provide phase boost near the unity-gain crossover, which increases the reguator s phase margin. Athough not directy part of the compensation, R9 decoupes the op amp s output from Q s arge gate capacitance. A second oop provides a fodback current imit. A2 compares the sense votage across R with 5m referenced to the positive rai. When the sense votage exceeds the reference, A2 s output drives Q s gate positive via A. In current imit, the output votage coapses and the current imit LED (D) turns on causing about 3m to drop across R3. A2 reguates Q s drain current so that the deficit between the 5m reference and the votage across R3 is made up across the sense resistor. The reduced sense votage is 2m, which sets the current imit to about 4mA. As the suppy votage increases, the votage across R3 increases, and the current imit fods back to a ower eve. The current imit oop deactivates when the oad current drops beow the reguated output current. When the suppy turns on rapidy, C bypasses the fod back circuit aowing the reguator to start-up into a heavy oad. Q does not require a heat sink. When mounted on a type FR4 PC board, Q has a therma resistance of 5 C/W. At.4W worst-case dissipation, Q can operate up to 8 C. IN = 4.75 ±5% k R7 3k R8 2k A /2 LT366 C3 6.8nF R9 Ω R.5Ω R3 2Ω Q Si9433DY.5k C µf R4 k D 5m R2 2k C5 47µF A2 /2 LT366 D2 N448 5k.µF C4 µf LT4-.2 R5* 2k 38.5k* C2 6.8nF R6 6.2k R MIN ** k C LOAD µf OUT 3.6 A Q2 2N k 4.75 TO 3.6 LDO AT A * % METAL FILM ** SET R MIN BASED ON LOAD CHARACTERISTICS LT366 F6 Figure 6. Precision 3.6, A Low Dropout Reguator 4

15 LT366/LT367 TYPICAL APPLICATIONS High Side Current Source The wide compiance current source shown in Figure 7 takes advantage of the LT366 s abiity to measure sma signas near the positive suppy rai. The LT366 adjusts Q s gate votage to force the votage across the sense resistor (R SENSE ) to equa the votage from the suppy to the potentiometer s wiper. A rai-to-rai op amp is needed because the votage across the sense resistor must drop to zero when the divided reference votage is set to zero. Q2 acts as a constant current sink to minimize error in the reference votage when the suppy votage varies. The circuit can operate over a wide suppy range (5 < CC < 3). At ow input votage, circuit operation is imited by the MOSFET s gate drive requirements. At LT4-.2 R P k CC 4k Q2 2N434 /2 LT366 R SENSE.2Ω k.33µf Ω I LOAD Q MTP23P6 5 < CC < 3 A < I LOAD < A AT CC = 5 ma < I LOAD < 6mA AT CC = 3 Figure 7. High Side Current Source LT366 F7 high input votage, circuit operation is imited by the LT366 s absoute maximum ratings and the output power requirements. The circuit deivers A at 2m of sense votage. With a 5 input suppy, the power dissipation is 5W. For operation at 7 C ambient temperature, the MOSFET s heat sink must have a therma resistance of: θ HS = θ JA(SYSTEM) θ JC(FET) = (25 C 7 C)/5W.25 C/W = C/W.25 C/W = 9.75 C/W which is easiy achievabe with a sma heat sink. Input votages greater than 5 require the use of a arger heat sink or a reduction of the output current. The circuit s suppy reguation is about.3%/. The output impedance is equa to the MOSFET s output impedance mutipied by the op amp s open-oop gain. Degradations in current-source compiance occur when the votage across the MOSFET s on-resistance and the sense resistor drops beow the votage required to maintain the desired output current. This condition occurs when: [ CC OUT ] < [I LOAD (R SENSE R ON )] Singe Suppy, khz, 4th Order Butterworth Fiter An LT367 is used in Figure 8 to form a 4th order Butterworth fiter. The fiter is a simpified state variabe architecture consisting of two cascaded 2nd order sections. Each section uses the 36 degree phase shift around IN 3.3 R* 29.5k C,pF A /4 LT367 k R2* 8.6k 29.5k* k µf C2,pF A2 /4 LT367.8k*,pF A3 /4 LT k*.8k*,pF A4 /4 LT367 OUT *% RESISTORS LT366 F8 Figure 8. 4-Poe khz, 3.3 Singe Suppy, State ariabe Fiter Using the LT367 5

16 LT366/LT367 TYPICAL APPLICATIONS the 2 op amp oop to create a negative summing junction at A s positive input. The circuit has ow sensitivities for center frequency and Q, which are set with the foowing equations: ω 2 = /(R C R2 C2) where: R = /(ω Q C) and R2 = Q/(ω C2). The DC bias appied to A2 and A4, haf suppy, is not needed when spit suppies are avaiabe. The circuit swings raito-rai in the passband making it an exceent anti-aiasing fiter for ADCs. The ampitude response is fat to khz then ros off at 8/decade. James Hahn, State ariabe Fiter Trims Predecessor s Component Count, Eectronics, Apri 2, 982. GAIN () GAIN k FREQUENCY (Hz) PHASE k PHASE (DEG) IN M pF M k /2 LT366 /2 LT SIGNAL AMP OUT CANCELLATION AMP 366 F Figure. Input Bias Current Canceation R P k CC /2 LT F R L 366 F9 Figure 9. Frequency Response of 4th Order Butterworth Fiter Figure. Rai-to-Rai Potentiometer Buffer 6

17 LT366/LT367 package description N8 Package 8-Lead PDIP (Narrow.3 Inch) (Reference LTC DWG # 5-8-5) ( ) (.43.65).3.5 ( ).4* (.6) MAX (.23.38) (.65) TYP. (2.54) BSC.2 (3.48) MIN.8.3 ( ).2 (.58) MIN.255.5* ( ) N8 2 NOTE: INCHES. DIMENSIONS ARE MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED. INCH (.254mm) S8 Package 8-Lead Pastic Sma Outine (Narrow.5 Inch) (Reference LTC DWG # 5-8-6).5 BSC ( ) NOTE MIN ( ).5.57 ( ) NOTE TYP RECOMMENDED SOLDER PAD LAYOUT ( ) ( ) 8 TYP ( ).4. (..254).6.5 (.46.27) NOTE: INCHES. DIMENSIONS IN (MILLIMETERS).4.9 ( ) TYP 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED.6" (.5mm).5 (.27) BSC SO8 33 7

18 LT366/LT367 package description S Package 4-Lead Pastic Sma Outine (Narrow.5 Inch) (Reference LTC DWG # 5-8-6).5 BSC ( ) NOTE 3 N MIN 2 3 N/ ( ) N N/ ( ) NOTE TYP RECOMMENDED SOLDER PAD LAYOUT ( ) ( ) 8 TYP ( ).4. (..254).6.5 (.46.27) NOTE: INCHES. DIMENSIONS IN (MILLIMETERS).4.9 ( ) TYP 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED.6" (.5mm).5 (.27) BSC S4 52 8

19 LT366/LT367 Revision History (Revision history begins at Rev B) RE DATE DESCRIPTION PAGE NUMBER B 3/ Change to Absoute Maximum Ratings Updated Format of Order Information Section Change to Eectrica Characteristics Note 2 2 3, 4, 5, 6, 7 Information furnished by Linear Technoogy Corporation is beieved to be accurate and reiabe. However, no responsibiity is assumed for its use. Linear Technoogy Corporation makes no representation that the interconnection of its circuits as described herein wi not infringe on existing patent rights. 9

20 LT366/LT367 Typica Appication Instrumentation Ampifier.µF GUARD M /4 LT367 AA k R F 2k k R G.3k INPUTS 2Ω /4 LT367 AB M /4 LT367 AC OUTPUT GUARD M 22pF R G.3k R GAIN = F = ( R G ) BW = 3kHz /4 LT367 AD R F 2k k k 366 TA3 Reated Parts PART DESCRIPTION COMMENTS LT78/LT79 Dua/Quad 55µA Max, Singe Suppy, Precision Op Amps Input/Output Common Mode Incudes Ground, 7 OS(MAX) and 2.5/ C Drift (Max), 2kHz GBW,.7/µs Sew Rate LTC52 Rai-to-Rai Input, Rai-to-Rai Output, Zero-Drift Ampifier High DC Accuracy, OS(MAX), n/ C Drift, MHz GBW, /µs Sew Rate, Suppy Current 2.2mA (Max), Singe Suppy, Can Be Configured for C-Load Operation LT78/LT79 Dua/Quad 7µA Max, Singe Suppy, Precision Op Amps Input/Output Common Mode Incudes Ground, 7 OS(MAX) and 4/ C Drift (Max), 85kHz GBW,.4/µs Sew Rate LT2/LT22 Dua/Quad 4MHz, 7/µs, Singe Suppy, Precision Op Amps Input Common Mode Incudes Ground, 275 OS(MAX) and 6/ C Drift (Max), Suppy Current.8mA per Op Amp (Max) LT495/LT496.5µA, Rai-to-Rai Input/Output Dua/Quad 375 OS(MAX), 2/ C Drift (Max), Over-The-Top Input 2 LT 3 RE B PRINTED IN USA Linear Technoogy Corporation 63 McCarthy Bvd., Mipitas, CA (48) FAX: (48) LINEAR TECHNOLOGY CORPORATION 995