DESCRIPTIO FEATURES LT1787/LT1787HV Precision, High Side Current Sense Amplifiers APPLICATIO S TYPICAL APPLICATIO

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1 Precision, High Side Current Sense Amplifiers FEATURES Input Offset Voltage: µv (Max) upply Operation (LTHV) -Bit Dynamic Range Operating Current: µa User-Selectable External Sense Resistor Bidirectional High Side Current Sensing Unidirectional or Bidirectional Output Input Noise Filtering C to C Operating Temperature Range Available in -Lead SO and MSOP Packages APPLICATIO S U Battery Monitoring Power Monitoring Portable Phones Cellular Phones Portable Test/Measurement Systems Battery-Operated Systems DESCRIPTIO U The LT is a complete micropower precision high side current sense amplifier. The LT monitors bidirectional currents via the voltage across an external sense resistor. A current or voltage output indicates the direction and magnitude of the sense current. The LT delivers greater than a -bit dynamic range with ultralow µv input offset voltage compared to a typical mv fullscale input voltage. A fixed gain of is set by onboard precision resistors. Input signal filtering is easily implemented with a capacitor between the FIL and FIL pins. The LTHV operates from.v to V total supply voltage and the LT operates from.v to V total supply voltage. Both versions have a PSRR in excess of db. The LT/LTHV draw only µa and are available in -lead SO and MSOP packages., LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO U -Bit Dynamic Resolution Unidirectional Output into LTC ADC Input Offset Voltage vs Supply Voltage TO LOAD I = A R SENSE.Ω FIL FIL LTHV V S V S DNC R OUT k = ( I LOAD R SENSE ) C.µF.V TO V R k C µf V REF V CC CS IN LTC CLK IN D GND OUT LT-. TO µp TA V INPUT OFFSET VOLTAGE (µv) TOTAL SUPPLY VOLTAGE (V) TAb

2 ABSOLUTE MAXIMUM RATINGS W W W Differential Sense Voltage... ±V Total Supply Voltage (LT)... V Total Supply Voltage (LTHV)... V Output Voltage... (.V) to ( V) Output Bias Voltage... (.V) to ( V) Operating Temperature Range (Note ) LTC... C to C LTI... C to C LTH... C to C U (Notes, ) Specified Temperature Range (Note ) LTC... C to C LTI... C to C LTH... C to C Storage Temperature Range... C to C Lead Temperature (Soldering, sec)... C PACKAGE/ORDER INFORMATION FIL DNC* ORDER PART NUMBER LTCMS LTIMS LTHVCMS LTHVIMS TOP VIEW U W U FIL MS PACKAGE -LEAD PLASTIC MSOP * DO NOT CONNECT T JMAX = C, θ JA = C/ W MS PART MARKING LTGM LTGN LTKJ LTKK Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: Consult LTC Marketing for parts specified with wider operating temperature ranges. FIL DNC* ORDER PART NUMBER LTCS LTIS LTHS LTHVCS LTHVIS LTHVHS TOP VIEW S PACKAGE -LEAD PLASTIC SO * DO NOT CONNECT T JMAX = C, θ JA = 9 C/ W FIL S PART MARKING I H HV HVI HVH ELECTRICAL CHARACTERISTICS (Note ) The denotes the specifications which apply over the temperature range C T A C, otherwise specifications are at T A = C. Total supply = (V S ) =.V to V (LTC),.V to V (LTHVC) unless otherwise specified. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V S, V S Sense Amplifier Supply Voltage Single Supply Operation (LT). V Single Supply Operation (LTHV). V ENSE Input Sense Voltage Full Scale ENSE = V S V S, = V, = V, A V = ±% mv V OS Input Offset Voltage (S) I OUT =, Supply = V ± µv C T A C µv I OUT = (LT) µv C T A C µv I OUT = (LTHV) µv C T A C µv

3 ELECTRICAL CHARACTERISTICS (Note ) LT/LTHV The denotes the specifications which apply over the temperature range C T A C, otherwise specifications are at T A = C. Total supply = ( ) =.V to V (LTC),.V to V (LTHVC) unless otherwise specified. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Input Offset Voltage (MS) I OUT =, Supply = V ± µv C T A C µv I OUT = (LT) µv C T A C µv I OUT = (LTHV) µv C T A C µv V OS TC Temperature Coefficient of V OS Supply = V (Note ). µv/ C I OUT(O) No-Load Output Current Error ENSE = V na (O) No-Load Output Voltage Error ENSE = V, Supply = V µv (S) C T A C µv No-Load Output Voltage Error ENSE = V, Supply = V µv (MS) C T A C µv g m Tranconductance, I OUT /ENSE ±ENSE = mv, mv, mv, mv, mv, µa/v Supply = Total Supply ENSE A V Gain, /ENSE ±ENSE = mv, Supply = V.. V/V Output Voltage Gain Error ±ENSE = mv, Supply = V % PSRR Supply Rejection Ratio ENSE = V, Supply =.V to V (LT) db ENSE = V, Supply =.V to V (LTHV) db PSRR Negative Supply Rejection Ratio ENSE = V, Supply = V, = V, db = V to V (LT) ENSE = V, Supply = V, = V, db = V to V (LTHV) V OS Change in Input Offset Voltage ENSE = V, Supply = V, =.V to V (LT) db with Change in Voltage ENSE = V, Supply = V, =.V to V (LTHV) db I S (O) Positive Input Sense Current ENSE = V µa I S (O) Negative Input Sense Current ENSE = V µa I EE(O) Negative Supply Current ENSE = V µa I OUT Output Current ENSE = ±mv ± µa Output Voltage ENSE = ±mv,.v ±. V Ripple Rejection = = V, Supply = V, f = khz db V OMIN Minimum Output Voltage ENSE = V, = V mv ENSE = V S V S = mv, = V mv ENSE = V, = V 9 mv ENSE = = mv, = V mv Unipolar Output ENSE = mv, = V mv Saturation Voltage ENSE = mv, = V mv ENSE = mv, = V mv ENSE = mv, = V 9 mv ENSE = mv, = V mv ENSE = mv, = V 9 mv ENSE = mv, = V mv ENSE = mv, = V 9 9 mv V OMAX Maximum Output Voltage. V R GA, R GA Input Gain-Setting Resistor Pin to Pin, Pin to Pin. kω R OUT Output Resistor Pin to Pin kω

4 ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the temperature range C T A C, otherwise specifications are at T A = C. Total supply = ( ) =.V to V (LTI),.V to V (LTHVI) unless otherwise specified. (Note ) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V S, V S Sense Amplifier Supply Voltage Single Supply Operation (LT). V Single Supply Operation (LTHV). V ENSE Input Sense Voltage Full Scale ENSE =, = V, = V, A V = ±% mv V OS Input Offset Voltage (S) I OUT =, Supply = V ± µv C T A C µv I OUT = (LT) µv C T A C µv I OUT = (LTHV) µv C T A C µv Input Offset Voltage (MS) I OUT =, Supply = V ± µv C T A C µv I OUT = (LT) µv C T A C µv I OUT = (LTHV) µv C T A C µv V OS TC Temperature Coefficient of V OS Supply = V (Note ). µv/ C I OUT(O) No-Load Output Current Error ENSE = V na (O) No-Load Output Voltage Error ENSE = V, Supply = V µv (S) C T A C µv No-Load Output Voltage Error ENSE = V, Supply = V µv (MS) C T A C µv g m Tranconductance, I OUT /ENSE ±ENSE = mv, mv, mv, mv, mv, µa/v Supply = Total Supply ENSE A V Gain, /ENSE ±ENSE = mv, Supply = V.. V/V Output Voltage Gain Error ±ENSE = mv, Supply = V % PSRR Supply Rejection Ratio ENSE = V, Supply =.V to V (LT) db ENSE = V, Supply =.V to V (LTHV) db PSRR Negative Supply Rejection Ratio ENSE = V, Supply = V, = V, db = V to V (LT) ENSE = V, Supply = V, = V, db = V to V (LTHV) V OS Change in Input Offset Voltage ENSE = V, Supply = V, =.V to V (LT) db with Change in Voltage ENSE = V, Supply = V, =.V to V (LTHV) db I S (O) Positive Input Sense Current ENSE = V µa I S (O) Negative Input Sense Current ENSE = V µa I EE(O) Negative Supply Current ENSE = V µa I OUT Output Current ENSE = ±mv ± µa Output Voltage ENSE = ±mv,.v ±. V Ripple Rejection = = V, Supply = V, f = khz db V OMIN Minimum Output Voltage ENSE = V, = V mv ENSE = V S V S = mv, = V mv ENSE = V, = V mv ENSE = = mv, = V mv

5 ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the temperature range C T A C, otherwise specifications are at T A = C. Total supply = ( ) =.V to V (LTI),.V to V (LTHVI) unless otherwise specified. (Note ) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Unipolar Output ENSE = mv, = V mv Saturation Voltage ENSE = mv, = V mv ENSE = mv, = V mv ENSE = mv, = V 9 mv ENSE = mv, = V mv ENSE = mv, = V mv ENSE = mv, = V mv ENSE = mv, = V 9 mv V OMAX Maximum Output Voltage. V R GA, R GA Input Gain-Setting Resistor Pin to Pin, Pin to Pin. kω R OUT Output Resistor Pin to Pin kω The denotes the specifications which apply over the temperature range C T A C, otherwise specifications are at T A = C. Total supply = ( ) =.V to V (LTH),.V to V (LTHVH) unless otherwise specified. (Note ) V S, V S Sense Amplifier Supply Voltage Single Supply Operation (LTH). V Single Supply Operation (LTHVH). V ENSE Input Sense Voltage Full Scale ENSE =, = V, = V, A V = ±% mv V OS Input Offset Voltage I OUT =, Supply = V ± µv C T A C µv I OUT = (LTH) µv C T A C µv I OUT = (LTHVH) µv C T A C µv V OS TC Temperature Coefficient of V OS Supply = V (Note ). µv/ C I OUT(O) No-Load Output Current Error ENSE = V na (O) No-Load Output Voltage Error ENSE = V, Supply = V µv C T A C µv g m Tranconductance, I OUT /ENSE ±ENSE = mv, mv, mv, mv, mv, µa/v Supply = Total Supply ENSE A V Gain, /ENSE ±ENSE = mv, Supply = V.. V/V Output Voltage Gain Error ±ENSE = mv, Supply = V % PSRR Supply Rejection Ratio ENSE = V, Supply =.V to V (LTH) db ENSE = V, Supply =.V to V (LTHVH) db PSRR Negative Supply Rejection Ratio ENSE = V, Supply = V, = V, db = V to V (LTH) ENSE = V, Supply = V, = V, db = V to V (LTHVH) V OS Change in Input Offset Voltage ENSE = V, Supply = V, =.V to V (LTH) db with Change in Voltage ENSE = V, Supply = V, =.V to V (LTHVH) db I S (O) Positive Input Sense Current ENSE = V µa I S (O) Negative Input Sense Current ENSE = V µa I EE(O) Negative Supply Current ENSE = V µa I OUT Output Current ENSE = ±mv ± µa Output Voltage ENSE = ±mv,.v ±. V Ripple Rejection = = V, Supply = V, f = khz db

6 ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the temperature range C T A C, otherwise specifications are at T A = C. Total supply = ( ) =.V to V (LTH),.V to V (LTHVH) unless otherwise specified. (Note ) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V OMIN Minimum Output Voltage ENSE = V, = V mv ENSE = V S V S = mv, = V mv ENSE = V, = V mv ENSE = V S V S = mv, = V mv Unipolar Output ENSE = mv, = V mv Saturation Voltage ENSE = mv, = V mv ENSE = mv, = V mv ENSE = mv, = V 9 mv ENSE = mv, = V mv ENSE = mv, = V mv ENSE = mv, = V mv ENSE = mv, = V 9 mv V OMAX Maximum Output Voltage V S. V R GA, R GA Input Gain-Setting Resistor Pin to Pin, Pin to Pin. kω R OUT Output Resistor Pin to Pin kω Note : Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note : ESD (Electrostatic Discharge) sensitive devices. Extensive use of ESD protection devices are used internal to the LT/LTHV, however, high electrostatic discharge can damage or degrade the device. Use proper ESD handling precautions. Note : The LTC/LTI are guaranteed functional over the operating temperature range of C to C. The LTH is guaranteed functional over the operating temperature range of C to C. Note : The LTC is guaranteed to meet specified performance from C to C. The LTC is designed, characterized and expected to meet specified performance from C to C but is not tested or QA sampled at these temperatures. The LTI is guaranteed to meet specified performance from C to C. The LTH is guaranteed to meet specified performance from C to C. Note : Testing done at =.V, = V unless otherwise specified. Note : This parameter is not % tested. TYPICAL PERFORMANCE CHARACTERISTICS U W INPUT OFFSET VOLTAGE (µv) Input Offset Voltage vs Supply Voltage = VS = V =.V T A = C T A = C T A = C TOTAL SUPPLY VOLTAGE (V) OUTPUT VOLTAGE (µv) No Load Output Voltage vs Supply Voltage = VS = V =.V T A = C T A = C T A = C TOTAL SUPPLY VOLTAGE (V) OUTPUT CURRENT (na) No Load Output Current vs Supply Voltage = V = V = VS T A = C T A = C T A = C TOTAL SUPPLY VOLTAGE (V) G G G

7 TYPICAL PERFORMANCE CHARACTERISTICS U W INPUT OFFSET VOLTAGE (µv) Input Offset Voltage vs Negative Supply Voltage = VS =.V = V T A = C T A = C T A = C NEGATIVE SUPPLY VOLTAGE (V) INPUT OFFSET VOLTAGE (µv) Input Offset Voltage vs Temperature = VS = V =.V TEMPERATURE ( C) OUTPUT VOLTAGE (V) Output Voltage vs Sense Voltage (Bidirectional Mode) =.V TO V =.V = V SENSE VOLTAGE ( VS ) (mv) G G G OUPUT VOLTAGE (V) Output Voltage vs Sense Voltage (Unidirectional Mode) =.V TO V T A = C TO C = GAIN (V/V) Gain vs Temperature = (.V ENSE )TO V V S > VS V S < VS GAIN (db) Gain vs Frequency ENSE = mv 9 SENSE VOLTAGE ( VS ) (mv). TEMPERATURE ( C).k k k k M M M FREQUENCY (Hz) G G G9 SUPPLY CURRENT (µa) Supply Current vs Supply Voltage T A = C T A = C T A = C V S = VS TOTAL SUPPLY VOLTAGE (V) NEGATIVE INPUT SENSE CURRENT (µa) Negative Input Sense Current vs Sense Voltage = (.V ENSE ) TO V 9 T A = C T A = C T A = C 9 9 SENSE VOLTAGE ( VS ) (mv) POSITIVE INPUT SENSE CURRENT (µa) Positive Input Sense Current vs Sense Voltage = (.V ENSE ) TO V T A = C T A = C T A = C 9 9 SENSE VOLTAGE ( VS ) (mv) G G G

8 TYPICAL PERFORMANCE CHARACTERISTICS U W Step Response at ENSE = V to mv Step Response at ENSE = V to mv Step Response at ENSE = V to mv mv V mv V mv V V mv V mv V V mv V C OUT = pf G C OUT = pf G C OUT = pf G Step Response at ENSE = V to mv Step Response at ENSE = V to mv Step Response at ENSE = mv to mv V mv V mv mv V mv V mv V V mv V V V V C OUT = G9 C OUT = pf G C OUT = G Step Response at ENSE = mv to mv Error vs Supply Ripple Voltage (ENSE = ±mv) Output Voltage vs Sense Voltage mv mv V V V C OUT = pf G SUPPLY RIPPLE VOLTAGE (mv) 9.% % % % ERROR LESS THAN.% k k k M FREQUENCY (Hz) OUTPUT VOLTAGE (V) V S = V V BIAS = V = V SENSE VOLTAGE (V S VS ) (V) G G

9 PIN FUNCTIONS U U U FIL, FIL (Pins, ): Negative and Positive Filter Terminals. Differential mode noise can be filtered by connecting a capacitor across FIL and FIL. Pole frequency f db = /(πrc), R =.kω. V S (Pin ): Negative Input Sense Terminal. Negative sense voltage will result in an output sinking current proportional to the sense current. V S is connected to an internal gain-setting resistor R GA and supplies bias current to the internal amplifier. DNC (Pin ): Do Not Connect. Connected internally. Do not connect external circuitry to this pin. (Pin ): Negative Supply or Ground for Single Supply Operation. (Pin ): Voltage Output or Current Output proportional to the magnitude of the sense current flowing through R SENSE. For bidirectional current sensing operation, = A V ENSE (O), where: > for > < for < (O) is the no load output voltage at ENSE = V. (Pin ): Output Bias Pin. For single supply, bidirectional current sensing operation, is connected to an external bias voltage, so that at ENSE = V, = (O). For dual supply, bidirectional current sensing operation, is connected to ground. Thus, = (O) at ENSE = V. (Pin ): Positive Input Sense Terminal. Positive sense voltage will result in an output sourcing current proportional to the sense current. is connected to an internal gain-setting resistor R GA. Connecting a supply to and a load to will allow the LT to measure its own supply current. BLOCK DIAGRAM W R SENSE I SENSE FIL R GA.k R GA.k FIL R GB.k R GB.k A I OUT Q Q R OUT k CURRENT MIRROR F Figure. LT Functional Diagram 9

10 APPLICATIONS INFORMATION The LT high side current sense amplifier (Figure ) provides accurate bidirectional monitoring of current through a user-selected sense resistor. The sense voltage is amplified by a fixed gain of and level shifted from the positive power supply to the ground referenced outputs. The output signal may be used in a variety of ways to interface with subsequent signal processing circuitry. Input and output filtering are easily implemented to eliminate aliasing errors. Theory of Operation Inputs V S and V S apply the sense voltage to matched resistors R G and R G. The opposite ends of resistors R G and R G are forced to be at equal potentials by the voltage gain of amplifier A. The currents through R G and R G are forced to flow through transistors Q and Q and are summed at node by the : current mirror. The net current from R G and R G flowing through resistor R OUT gives a voltage gain of eight. Positive sense voltages result in being positive with respect to pin. Pins, and may be connected in a variety of ways to interface with subsequent circuitry. Split supply and single supply output configurations are shown in the following sections. Supply current for amplifier A is drawn from the V S pin. The user may choose to include this current in the monitored current through R SENSE by careful choice of connection polarity. Selection of External Current Sense Resistor External R SENSE resistor selection is a delicate trade-off between power dissipation in the resistor and current measurement accuracy. The LT makes this decision less difficult than with competitors products. The maximum sense voltage may be as large as ±mv to get maximum resolution, however, high current applications will not want to suffer this much power dissipation in the sense resistor. The LT s input offset voltage of µv gives high resolution for low sense voltages. This wide operating dynamic range gives the user wide latitude in tailoring the range and resolution of his supply monitoring function. U W U U Kelvin connection of the LT s and inputs to the sense resistor should be used in all but the lowest power applications. Solder connections and PC board interconnect resistance (approximately.mω per square) can be a large error in high current systems. A -Amp application might choose a mω sense resistor to give a mv full-scale input to the LT. Input offset voltage will limit resolution to ma. Neglecting contact resistance at solder joints, even one square of PC board copper at each resistor end will cause an error of %. This error will grow proportionately higher as monitored current levels rise to tens or hundreds of amperes. Input Noise Filtering The LT provides input signal filtering pins FIL and FIL that are internally connected to the midpoint taps of resistors R G and R G. These pins may be used to filter the input signal entering the LT s internal amplifier, and should be used when fast current ripple or transients may flow through the sense resistor. High frequency signals above the khz bandwidth of the LT s internal amplifier will cause errors. A capacitor connected between FIL and FIL creates a single pole low pass filter with corner frequency: f db = /(πrc) where R =.k. A.µF capacitor creates a pole at.khz, a good choice for many applications. Common mode filtering from the FIL and FIL pins should not be attempted, as mismatch in the capacitors from FIL and FIL will create AC common mode errors. Common mode filtering must be done at the power supply output. Output Signal Range The LT s output signal is developed by summing the net currents through R G and R G into output resistor R OUT. The pins and may be connected in numerous configurations to interface with following circuitry in either single supply or split supply applications. Care must be used in connecting the output pins to preserve signal accuracy. Limitations on the signal swing at are imposed by the negative supply,, and the input voltage V S. In the negative direction, internal circuit saturation with loss of accuracy occurs for < mv

11 APPLICATIONS INFORMATION U W U U with absolute minimum swing at mv above. may swing positive to within.v of or a maximum of V, a limit set by internal junction breakdown. Within these contraints, an amplified, level shifted representation of the R SENSE voltage is developed across R OUT. Split Supply Bipolar Output Swing Figure shows the LT used with split power supplies. The pin is connected to ground, and the output signal appears at the pin. Bidirectional input currents can be monitored with the output swinging positive for current flow from V S and V S. Input currents in the opposite direction cause to swing below ground. Figure shows an optional output capacitor connected from to ground. This capacitor may be used to filter the output signal before it is processed by other circuitry.figure shows the voltage transfer function of the LT used in this configuration. Single Supply with Shifted Figure shows the LT used in a single supply mode with the pin shifted positive using an external LT voltage reference. The output signal can swing above and below to allow monitoring of positive or negative currents through the sense resistor, as shown in Figure. The choice of reference voltage is not critical except for the precaution that adequate headroom must be provided for to swing without saturating the internal circuitry. The component values shown in Figure allow operation with supplies as low as.v. TO CHARGER/ LOAD V C µf FIL DNC R SENSE LT FIL R OUT C* pf C µf OUTPUT F V TO CHARGER/ LOAD OUTPUT VOLTAGE (V) *OPTIONAL OUTPUT VOLTAGE OUTPUT BIAS VOLTAGE (V)..... Figure. Split Supply Output Voltage R SENSE.V C TO µf V FIL FIL.V LTHV k % DNC R OUT C µf LT-. C* pf Figure. Charge/Discharge Current Monitor on Single Supply with =.V..... =.V TO V T A = C TO C. 9 9 SENSE VOLTAGE (V S VS ) (mv) =.V TO V T A = C TO C OUTPUT F. 9 9 SENSE VOLTAGE ( VS ) (mv) F F *OPTIONAL Figure. Split Supply Operation Figure. Single Supply Output Voltage with =.V

12 APPLICATIONS INFORMATION U W U U Operation with A/D Converter Figure shows the LT operating with the LTC A/D converter. This low cost circuit is capable of -bit resolution of unipolar currents. The IN pin of the A/D converter is biased at V by the resistor divider R and R. This voltage increases as sense current increases, with the amplified sense voltage appearing between the A/D converters IN and IN terminals. The front page of the data sheet shows a similar circuit which uses a voltage reference for improved accuracy and signal range. The LTC converter uses sequential sampling of its IN and IN inputs. Accuracy is degraded if the inputs move between sampling intervals. A filter capacitor from FIL to FIL as well as a filter capacitor from to may be necessary if the sensed current changes more than LSB within a conversion cycle. Buffered Output Operation Figure shows the LT s outputs buffered by an operational amplifier configured as an I/V converter. This configuration is ideal for monitoring very low voltage supplies. The LT s pin is held equal to the reference voltage appearing at the op amp s noninverting input. This allows monitoring supplies as low as.v. The op amp s output may swing from ground to its positive supply voltage. The low impedance output of the op amp may drive following circuitry more effectively than the high output impedance of the LT. The I/V converter configuration also works well with split supply voltages. Single Supply Unidirectional Operation Figure shows the simplest connection in which the LT may be used. The pin is connected to ground, and the pin swings positive with increasing sense current. The LT s outputs can swing as low as mv as shown in Figure 9. Accuracy is sacrificed at small output levels, but this is not a limitation in protection circuit applications or where sensed currents do not vary greatly. Increased low level accuracy can be obtained by level shifting above ground. The level shifting may be done with resistor dividers, voltage references or a simple diode. Accuracy is ensured if the output signal is sensed differentially between and. TO CHARGER/ LOAD FIL DNC TO LOAD R SENSE LT FIL DNC FIL R OUT R SENSE Figure. Single Supply.V Bidirectional Operation with External Voltage Reference and I/V Converter LT FIL DNC I OUT Figure. Unidirectional Output into A/D with Fixed Supply at FIL R OUT R SENSE C.µF R k % I SENSE FIL LTHV V S R OUT F IN V CC LTC CS CLK IN V REF GND D OUT.V TO V Figure. Unidirectional Current Sensing Mode V R k % C µf C pf.v A.V M % LT9-. C µf.v ENSE(MAX) LT9 F V TO µp F A

13 APPLICATIONS INFORMATION OUTPUT VOLTAGE (V) U W U U IDEAL.... V S VS (V).. F9 Figure 9. Expanded Scale of Unidirectional Output Adjusting Gain Setting The LT may be used in all operating modes with an external resistor used in place of the internal k R OUT resistor. When an external resistor is used, leave the pin floating or connected to the pin. This will remove the internal R OUT from the circuit. The voltage gain will be gm R OUT where gm is the LT s transconductance, µa/v typical. A nominal gain of may be obtained with an external k resistor used in place of the internal k R OUT : A V = gm R OUT = µa/v k = The transconductance gm is set by on-chip resistors on the LT. These resistors match well but have loose absolute tolerance. This will normally require that the external gain setting resistor be trimmed for initial accuracy. After trimming, the temperature stability of the gm and therefore gain will be ppm/ C. The only limitations placed upon the resistor choice is care must be taken not to saturate the internal circuitry by violating the V OMAX specification of.v.

14 PACKAGE DESCRIPTION U MS Package -Lead Plastic MSOP (LTC DWG # --).9 ±. (. ±.). (.) MIN.. (..). ±. (. ±.) TYP. (.) BSC. ±. (. ±.) (NOTE ). (.) REF RECOMMENDED SOLDER PAD LAYOUT GAUGE PLANE. (.). (.) DETAIL A NOTE:. DIMENSIONS IN MILLIMETER/(INCH). DRAWING NOT TO SCALE TYP. ±. (. ±.) DETAIL A SEATING PLANE.9 ±. (.9 ±.). (.) MAX.. (.9.) TYP. (.) BSC. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED.mm (.") PER SIDE. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED.mm (.") PER SIDE. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE.mm (.") MAX. ±. (. ±.) (NOTE ). (.) REF. ±. (. ±.) MSOP (MS)

15 PACKAGE DESCRIPTION U S Package -Lead Plastic Small Outline (Narrow.) (LTC DWG # --). BSC. ±..9.9 (..) NOTE. MIN. ±... (.9.9).. (..9) NOTE. ±. TYP RECOMMENDED SOLDER PAD LAYOUT.. (..).. (..) TYP..9 (..).. (..).. (..) NOTE: INCHES. DIMENSIONS IN (MILLIMETERS)..9 (..) TYP. DRAWING NOT TO SCALE. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED." (.mm). (.) BSC SO Information furnished by Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

16 TYPICAL APPLICATION U Split or Single Supply Operation, Bidirectional Output into A/D I S = ±ma RCE.V V FIL V S DNC Ω % LT FIL k (±V) OPTIONAL SINGLE SUPPLY OPERATION: DISCONNECT FROM GROUND AND CONNECT IT TO V REF. REPLACE UPPLY WITH GROUND. OUTPUT CODE FOR ZERO CURRENT WILL BE ~ µf V V CC V CONV A IN LTC CLK V REF DOUT GND V µf V µf V CLOCKING CIRCUITRY D OUT TA RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC Dual Precision Instrumentation Switched Capacitor Building Block db CMRR, V to V Operation LT9/LT9 Dual and Quad Micropower Rail-to-Rail Input and Output Op Amps µa Amplifier,.V to V Operation, Over-The-Top TM Inputs LT/LT Rail-to-Rail Current Sense Amplifiers Accurate Output Current Programming, Battery Charging to V Over-The-Top is a trademark of Linear Technology Corporation. Linear Technology Corporation McCarthy Blvd., Milpitas, CA 9- () -9 FAX: () - LT REV C PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 999