LT1620/LT1621 Rail-to-Rail Current Sense Amplifier U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ Accurate Output Current Programming Usable in Charging Applications Up to 32V Output Programmable Load Current Monitor for End-ofCharging-Cycle Notification (16-Pin Version) Dual Function IC (LT1621) Allows Convenient Integration of Load and Input Current Sensing Level-Shifted Current Sense Output for Current Mode PWM Controllers Can be Used for NiCd, NiMH, Lead-Acid and LithiumIon Battery Charging Greater than 96% Efficiency Possible in Charger Applications High Output Currents Possible: > 10A Easily Obtained UO APPLICATI ■ ■ ■ ■ S High Current Battery Chargers High Output Voltage DC/DC Converters Constant Current Sources Overcurrent Fault Protectors The LT ®1620 simplifies the design of high performance, controlled current battery charging circuits when used in conjunction with a current mode PWM controller IC. The LT1620 regulates average output current independent of input and output voltage variations. Output current can be easily adjusted via a programming voltage applied to the LT1620’s PROG pin. Most current mode PWM controllers have limited output voltage range because of common mode limitations on the current sense inputs. The LT1620 overcomes this restriction by providing a level-shifted current sense signal, allowing a 0V to 32V output voltage range. The 16-pin version of the LT1620 contains a programmable low charging current flag output. This output flag can be used to signal when a Li-Ion battery charging cycle is nearing completion. The LT1621 incorporates two fully independent current control circuits for dual loop applications. , LTC and LT are registered trademarks of Linear Technology Corporation. UO TYPICAL APPLICATI (VBATT + 0.5V) TO 32V VIN LTC1435 SYNCHRONOUS BUCK REGULATOR 0.1µF 6 VCC 1 8 SENSE AVG 2 7 IOUT PROG LT1620MS8 3 GND 4 5 IN – IN + Efficiency 100 VBATT 27µH VIN = 24V IBATT TO 4A SW SENSE – INTVCC VIN 22µF 35V ×2 0.025Ω 1.43M 0.1% FB 0.1µF 110k 0.1% 3k 1% VBATT = 16V 95 VBATT = 12V + 22µF 35V EFFICIENCY (%) ITH + 90 VBATT = 6V 85 80 15.75k 1% 75 LT1620/21 • F01 SIMPLIFIED SCHEMATIC. SEE FIGURE 2 FOR COMPLETE SCHEMATIC Figure 1. Low Dropout, High Current Li-Ion Battery Charger 0 1 3 4 2 BATTERY CHARGE CURRENT (A) 5 1620/21 • TA02 1 LT1620/LT1621 W W W AXI U U ABSOLUTE RATI GS (Referenced to Ground) (Note 1) Power Supply Voltage: VCC ..........................– 0.3V to 7V Programming Voltage: PROG, PROG2 ............ – 0.3V to VCC + 0.3V (7V Max) IOUT, SENSE, AVG, AVG2, MODE Voltage ................ – 0.3V to VCC + 0.3V (7V Max) Sense Amplifier Input Common Mode .......– 0.3V to 36V Operating Ambient Temperature Range Commercial ............................................ 0°C to 70°C Industrial ............................................ – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C W U U PACKAGE/ORDER I FOR ATIO TOP VIEW TOP VIEW TOP VIEW 16 AVG SENSE 1 PROG A 1 16 VCC A AVG A 2 15 IN + A SENSE A 3 14 IN – A SENSE 1 8 AVG IOUT 2 7 PROG GND 3 6 VCC IOUT 3 14 PROG IN – 4 5 IN + NC 4 13 PROG2 IOUT A 4 13 GND A 12 AVG2 GND B 5 12 IOUT B 15 NC NC 2 GND 5 MS8 PACKAGE S8 PACKAGE 8-LEAD PLASTIC MSOP 8-LEAD PLASTIC SO θJA = 250°C/W (MS) θJA = 120°C/W (S) MODE 6 NC 7 IN – ORDER PART NUMBER LT1620CS8 LT1620IS8 LT1620CMS8 11 VCC IN – B 6 11 SENSE B 10 NC IN + B 7 10 AVG B 9 8 9 VCC B 8 IN + PROG B GN PACKAGE 16-LEAD PLASTIC SSOP θJA = 149°C/W GN PACKAGE 16-LEAD PLASTIC SSOP ORDER PART NUMBER ORDER PART NUMBER LT1620CGN LT1620IGN LT1621CGN LT1621IGN MS8 PART MARKING BC θJA = 149°C/W Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS VIN+ = 16.8V, VCC = 5V, VIOUT = 2V, TA = 25°C unless otherwise noted. SYMBOL PARAMETER Supply VCC 5V Supply Voltage ICC DC Active Supply Current LT1620GN DC Active Supply Current LT1620S8, LT1620MS8, 1/2 LT1621GN DC Active Supply Current LT1620S8, LT1620MS8, 1/2 LT1621GN Current Sense Amplifier VCM Input Common Mode Range Differential Input Voltage Range VID (IN+ – IN –) VOSSENSE Input Offset - Measured at ×1 Output (VSENSE) 2 CONDITIONS ● SENSE = AVG = PROG = PROG2 = VCC 4.5V ≤ VCC ≤ 5.5V, IN+ – IN – = 100mV SENSE = AVG = PROG = VCC 4.5V ≤ VCC ≤ 5.5V, IN+ – IN – = 100mV SENSE = AVG = PROG = VCC 4.5V ≤ VCC ≤ 5.5V, IN+ – IN – = 0mV MIN TYP MAX 4.5 5.0 2.8 5.5 3.8 4.0 3.3 3.7 1.9 2.1 V mA mA mA mA mA mA ● 2.3 ● 1.3 ● UNITS 0V ≤ VCM ≤ 32V ● 0 0 32 125 V mV VCC ≤ VCM ≤ 32V VID = 80mV ● –5 –6 5 6 mV mV ● LT1620/LT1621 ELECTRICAL CHARACTERISTICS IN+ = 16.8V, VCC = 5V, VIOUT = 2V, TA = 25°C unless otherwise noted. SYMBOL PARAMETER Current Sense Amplifier Input Offset - Measured at ×10 Output VOSAVG (VAVG) Input Offset - Measured at × 20 Output (VAVG2) VSENSE No-Load Output Offset + – IB(IN , IN ) Input Bias Current (Sink) VOSAVG2 CONDITIONS MIN VCC ≤ VCM ≤ 32V 35mV ≤ VID ≤ 125mV VCM = 0V, VID = 80mV VCC ≤ VCM ≤ 32V 0V ≤ VID ≤ 35mV 0V ≤ VCM ≤ 32V, VID = 0V, Referenced to VCC VCC ≤ VCM ≤ 32V (Note 2) ● ● ● ● ● Input Bias Current (Source) –3 –4 – 10 –3 –4 – 0.1 200 185 VCM = 0V (Note 2) TYP 3 4 15 3 4 –3 270 4.0 ● Transconductance Amplifier Amplifier Transconductance gm ● AV VOLIOUT Amplifier Voltage Gain IOUT Saturation Limit (Sink) VPROG IBPROG VOSPROG PROG Input Range Input Bias Current Input Offset Voltage (VAVG – VPROG) End-of-Cycle Comparator VPROG2 PROG2 Input Range VHYST Input Hysteresis IBPROG2 Input Bias Current VOLMODE Output Logic Low Output (Sink) 1V ≤ VIOUT ≤ 3V IIOUT = 50µA IIOUT = 200µA IIOUT = 1mA ● ● ● ● VCC – 1.25 ● –7 –8 ● VCC – 2.5 Measured at PROG Pin IIOUT = 130µA Measured at AVG2 Pin Measured at PROG2 Pin IMODE = 0.5mA IMODE = 10mA The ● denotes specifications which apply over the full operating temperature range. 3000 2200 60 MAX 3500 80 0.05 0.10 0.35 400 430 5.25 5.50 4000 4800 0.15 0.30 0.65 VCC 20 ● ● 7 8 VCC – 0.15 15 20 0.1 0.5 0.5 1.2 UNITS mV mV mV mV mV mV µA µA mA mA µmho µmho dB V V V V nA mV mV V mV nA V V Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Input bias currents are disabled when VCC is removed, even with common mode voltage present at IN+, IN–. U U U PI FU CTIO S VCC: 5V ±10% Power Supply Input. IN+ : Sense Amplifier Positive Input. Typically connected to inductor side of current sense resistor. Common mode voltage range is 0V to 32V. IN–: Sense Amplifier Negative Input. Typically connected to load side of current sense resistor. Common mode voltage range is 0V to 32V. SENSE: Sense Amplifier AV = – 1 Output. Used as levelshifted output for PWM controller current sense input. The sense output is designed to have an inherent offset to ensure continuity around zero inductor current. Typical output is –3mV with differential input voltage (IN+ – IN–) = 0. AVG: Sense Amplifier A V = –10 Output and Transconductance Amplifier Positive Input. Used as integration node for average current control. Integration time constant is calculated using 2.5kΩ typical output impedance. PROG: Transconductance Amplifier Negative Input. Program node for average current delivered to load during current mode operation. Average current delivered to load imposes voltage differential at current sense amplifier 3 LT1620/LT1621 U U U PI FU CTIO S input (across external sense resistor) equal to (VCC – VPROG)/10. Input voltage range is VCC to (VCC – 1.25V). equals (VCC – VPROG2)/20. Input voltage range is (VCC – 0.15V) to (VCC – 2.5V). AVG2: Sense Amplifier AV = – 20 Output and Comparator Positive Input. Used as integration node for end-of-cycle determination flag. Integration time constant is calculated using 5kΩ typical output impedance. GND: Ground Reference. PROG2: Comparator Negative Input. Program node for end-of-cycle determination typically used during voltage mode operation. The comparator threshold is reached when the current sense amplifier differential input voltage IOUT: Transconductance Amplifier Output. In typical application, IOUT sinks current from current-setting node on companion PWM controller IC, facilitating current mode loop control. MODE: Comparator Open Collector Output. Output is logic low when magnitude of current sense amplifier differential input voltage is less than (VCC – VPROG2)/20. W FUNCTIONAL BLOCK DIAGRA U U 5V VCC 500Ω + – + – (×1 GAIN) SENSE 2.5k (×10 GAIN) 5k IN+ CURRENT SENSE RESISTOR VID IN– + SENSE AMPLIFIER PROG IOUT ITH – + PROG2* MODE* END-OF-CYCLE (ACTIVE LOW) – GND LT1620/21 • FBD (Refer to the Functional Block Diagram) Current Sense Amplifier The current sense amplifier is a multiple output voltage amplifier with an operational input common mode range from 0V to 32V. The amplifier generates scaled output voltages at the SENSE, AVG and AVG2 (available in LT1620GN) pins. These output signal voltages are referenced to the VCC supply by pulling signal current through internal VCC referred resistors. 4 PWM CONTROLLER + – *AVAILABLE IN THE LT1620GN ONLY AVG (×20 GAIN) AVG2* gm U OPERATION INTVCC SENSE + SENSE – The first output (SENSE) is a unity gain, level-shifted representation of the input signal (IN+ – IN–). In typical PWM/ charger type applications, this output is used to drive the current sense amplifier of the mated PWM controller IC. The other two outputs (AVG and AVG2) are internally connected to a transconductance amplifier and comparator, respectively. The AVG output yields a gain of 10, and the AVG2 output provides a gain of 20. These pins are LT1620/LT1621 U OPERATION (Refer to the Functional Block Diagram) used as integration nodes to facilitate averaging of the current sense amplifier signal. (Note: filter capacitors on these pins should bypass to the VCC supply.) Integration of these signals enables direct sensing and control of DC load current, eliminating the inclusion of ripple current in load determination. Transconductance Amplifier The transconductance amplifier converts the difference between the current programming input voltage (VPROG) and the average current sense output (VAVG) into a current at the amplifier output pin (IOUT). The amplifier output is unidirectional and only sinks current. The amplifier is designed to operate at a typical output current of 130µA with VAVG = VPROG. In typical PWM/charger type applications, the IOUT current is used to servo the current control loop on the mated PWM controller IC to maintain a programmed load current. Comparator The comparator circuit (available only in the LT1620GN) may be used as an end-of-cycle sensor in a Li-Ion battery charging system. The comparator detects when the charging current has fallen to a small value (typically 20% of the maximum charging current). The comparator drives an open collector output (MODE) that pulls low when the VAVG2 voltage is more positive than VPROG2 (output current below the programmed threshold). U W U U APPLICATIONS INFORMATION In Figure 2, an LT1620MS8 is coupled with an LTC1435 switching regulator in a high performance lithium-ion battery charger application. The LTC1435 switching regulator delivers extremely low dropout as it is capable of approximately 99% duty cycle operation. No additional power supply voltage is required for the LT1620 in this application; it is powered directly from a 5V local supply generated by the LTC1435. The DC charge current control and high common mode current sense range of the LT1620 combine with the low dropout capabilities of the LTC1435 to make a 4-cell Li-Ion battery charger with over 96% efficiency, and only 0.5V input-to-output drop at 3A charging current. Refer to the LTC1435 data sheet (available from the LTC factory) for additional information on IC functionality, performance and associated component selection. This LT1620/LTC1435 battery charger is designed to yield a 16.8V float voltage with a battery charge current of 3.2A. The VIN supply can range from 17.3V to 28V (limited by the switch MOSFETs). The charger provides a constant 3.2A charge current until the battery voltage reaches the programmed float voltage. Once the float voltage is achieved, a precision voltage regulation loop takes control, allowing the charge current to fall as required to complete the battery charge cycle. RSENSE Selection The LT1620 will operate throughout a current programming voltage (VPROG) range of 0V to – 1.25V (relative to VCC), however, optimum accuracy will be obtained with a current setting program voltage of – 0.8V, corresponding to 80mV differential voltage across the current sense amplifier inputs. Given the desired current requirement, selection of the load current sense resistor RSENSE is possible. For the desired 3.2A charge current; RSENSE = 80mV/3.2A or 0.025Ω At the programmed 3.2A charge current, the sense resistor will dissipate (0.08V)(3.20A) = 0.256W, and must be rated accordingly. Current Sense The current sense inputs are connected on either side of the sense resistor with IN+ at the more positive potential, given average charging current flow. The sense resistor to IN+, IN– input paths should be connected using twisted pair or minimum PC trace spacing for noise immunity. Keep lead lengths short and away from noise sources for best performance. 5 LT1620/LT1621 U U W U APPLICATIONS INFORMATION + R2 1.5M C4 0.1µF RUN C11, 56pF C13 0.033µF X7R C12, 0.1µF COSC TG RUN/SS BOOST R1 1k SFB C9, 100pF 5 6 C18 0.1µF 7 8 RP1 3k 1% C16 0.1µF IN+ IN– VCC GND LT1620MS8 IOUT PROG AVG SENSE 4 C2 22µF 35V VIN 17.3V TO 28V RSENSE 0.025Ω VBATT 16.8V SW LTC1435 SGND C17, 0.01µF + Si4412DY L1 27µH D1* ITH C14 1nF C5, 0.1µF C1 22µF 35V VIN + D2* C6 0.1µF INTVCC VOSENSE BG SENSE – PGND SENSE + EXTVCC C3 22µF 35V Li-ION Si4412DY + C7 4.7µF C10 100pF * D1, D2: CENTRAL SEMICONDUCTOR CMDSH-3 3 2 1 C15 0.1µF C8, 100pF RP2 15.75k 1% RF2 110k 0.1% RF1 1.44M 0.1% LT1620/21 • F02 Figure 2. LT1620/LTC1435 Battery Charger Charge Current Programming Output Float Voltage Output current delivered during current mode operation is determined through programming the voltage at the PROG pin (VPROG). As mentioned above, optimum performance is obtained with (VCC – VPROG) = 0.8V. The LT1620 is biased with a precision 5V supply produced by the LTC1435, enabling use of a simple resistor divider from VCC to ground for a VPROG reference. Using the desired 2.5kΩ Thevenin impedance at the PROG pin, values of RP1 = 3k and RP2 = 15.75k are readily calculated. The PROG pin should be decoupled to the VCC supply. The 3.2A charger circuit is designed for a 4-cell Li-Ion battery, or a battery float voltage of 16.8V. This voltage is programmed through a resistor divider feedback to the LTC1435 VOSENSE pin, referencing its 1.19V bandgap voltage. Resistor values are determined through the relation: RF1 = (VBATT – 1.19)/(1.19/RF2). Setting RF2 = 110k yields RF1 = 1.44M. Different values of charging current can be obtained by changing the values of the resistors in the VPROG setting divider to raise or lower the value of the programming voltage, or by changing the sense resistor to an appropriate value as described above. 6 Other Decoupling Concerns The application schematic shown in Figure 2 employs several additional decoupling capacitors. Due to the inherently noisy environment created in switching applications, decoupling of sensitive nodes is prudent. As noted in the schematic, decoupling capacitors are included on the current programming pin (PROG) to the VCC rail and LT1620/LT1621 U W U U APPLICATIONS INFORMATION between the IN+ and IN– inputs. Effective decoupling of supply rails is also imperative in these types of circuits, as large current transients are the norm. Power supply decoupling should be placed as close as possible to the ICs, and each IC should have a dedicated capacitor. Design Equations Sense resistor: RSENSE = VID /IMAX Current limit programming voltage: VPROG = VCC – [(10)(VID)] As mentioned in the previous circuit discussion, the charging current level is set to correspond to a sense voltage of 80mV. The circuit in Figure 3 uses a resistor divider to create a programming voltage (VCC –VPROG2)of 0.5V. The MODE flag will therefore trip when the charging current sense voltage has fallen to 0.5V/20 or 0.025V. Thus, the end-of-cycle flag will trip when the charging current has been reduced to about 30% of the maximum value. Input Current Sensing Application Voltage feedback resistors: RF1/RF2 = (VBATT(FLOAT) – 1.19)/1.19 End-of-Cycle Flag Application Figure 3 illustrates additional connections using the LT1620GN, including the end-of-cycle (EOC) flag feature. The EOC threshold is used to notify the user when the required load current has fallen to a programmed value, usually a given percentage of maximum load. The end-of-cycle output (MODE) is an open-collector pulldown; the circuit in Figure 3 uses a 10k pull-up resistor on the MODE pin, connected to VCC. Monitoring the load placed on the VIN supply of a charging system is achieved by placing a second current sense resistor in front of the charger VIN input. This function is useful for systems that will overstress the input supply (wall adapter, etc.) if both battery charging and other system functions simultaneously require high currents. This allows use of input supply systems that are capable of driving full-load battery charging and full-load system requirements, but not simultaneously. If the input supply current exceeds a predetermined value due to a combination of high battery charge current and external system demand, the input current sense function automatically 5V The EOC flag threshold is determined through programming VPROG2. The magnitude of this threshold corresponds to 20 times the voltage across the sense amplifier inputs. + C1 1µF 22µF 1 2 SENSE AVG 7 PROG LT1620MS8 6 3 VCC GND 4 IOUT IN+ IN– 22µF L1B 10µH AVG MBRS340 7 PROG 4.7µF + RUN + IN+ R3 10k 6 4 C2 3.3µF R1 5.5k R2 50k END-OF-CYCLE (ACTIVE LOW) LT1620/21 • F03 Figure 3. End-of-Cycle Flag Implementation with LT1620GN S/S VFB GND GND TAB IFB 8 VBATT = 12.3V 5 LT1513 C1, 3.3µF AVG2 VCC VSW VIN PROG2 IN– TO SYSTEM LOAD + IOUT MODE RP2 12k 1% R1 0.033Ω LT1620GN VEE C2 1µF 5 CONNECTED AS IN FIGURE 2 SENSE RP1 3k 1% 8 L1A 10µH 57k + 2 3 22µF ×2 Li-ION 24Ω 6.4k VC 0.22µF 1 RSENSE 0.1Ω 0.1µF X7R 1620/21 • F04 Figure 4. Input Current Sensing Application 7 LT1620/LT1621 U W U U APPLICATIONS INFORMATION reduces battery charging current until the external load subsides. In Figure 4 the LT1620 is coupled with an LT1513 SEPIC battery charger IC to create an input overcurrent protected charger circuit. The programming voltage (VCC – VPROG) is set to 1.0V through a resistor divider (RP1 and RP2) from the 5V input supply to ground. In this configuration, if the input current drawn by the battery charger combined with the system load requirements exceeds a current limit threshold of 3A, the battery charger current will be reduced by the LT1620 such that the total input supply current is limited to 3A. Refer to the LT1513 data sheet for additional information. PROGRAMMING ACCURACY CONSIDERATIONS PWM Controller Error Amp Maximum Source Current In a typical battery charger application, the LT1620 controls charge current by servoing the error amplifier output pin of the associated PWM controller IC. Current mode control is achieved when the LT1620 sinks all of the current available from the error amplifier. Since the LT1620 has finite transconductance, the voltage required to generate its necessary output current translates to input offset error. The LT1620 is designed for a typical IOUT sink current of 130µA to help reduce this term. Knowing the current source capability of the associated PWM controller in a given application will enable adjustment of the required programming voltage to accommodate the desired charge current. A plot of typical VPROG voltage offset vs PWM source capability is shown in Figure 5a. For example, the LTC1435 has a current source capability of about 75µA. This translates to about –15mV of induced programming offset at VPROG (the absolute voltage at the PROG pin must be 15mV lower). VCC – VPROG Programmed Voltage ≠ 0.8V The LT1620 sense amplifier circuit has an inherent input referred 3mV offset when IN+ – IN– = 0V to insure closedloop operation during light load conditions. This offset vs input voltage has a linear characteristic, crossing 0V as IN+ – IN– = 80mV. The offset is translated to the AVG output (times a factor of 10), and thus to the programming 8 voltage VPROG. A plot of typical VPROG offset voltage vs IN+ – IN– is pictured in Figure 5b. For example, if the desired load current corresponds to 100mV across the sense resistor, the typical offset, at VPROG is 7.5mV (the absolute voltage at the PROG pin must be 7.5mV higher). This error term should be taken into consideration when using VID values significantly away from 80mV. VCC – VPROG2 Programmed Voltage ≠ 1.6V (LT1620GN Only) The offset term described above for VPROG also affects the VPROG2 programming voltage proportionally (times an additional factor of 2). However, VPROG2 voltage is typically set well below the zero offset point of 1.6V, so adjustment for this term is usually required. A plot of typical VPROG2 offset voltage vs IN+ – IN– is pictured in Figure 5c. For example, setting the VPROG2 voltage to correspond to IN+ – IN– = 15mV typically requires an additional –50mV offset (the absolute voltage at the PROG2 pin must be 50mV lower). Sense Amplifier Input Common Mode < (VCC – 0.5V) The LT1620 sense amplifier has additional input offset tolerance when the inputs are pulled significantly below the VCC supply. The amplifier can induce additional input referred offset of up to 11mV when the inputs are at 0V common-mode. This additional offset term reduces roughly linearly to zero when VCM is about VCC – 0.5V. In typical applications, this offset increases the charge current tolerance for “cold start” conditions until VBAT moves away from ground. The resulting output current shift is generally negative; however, this offset is not precisely controlled. Precision operation should not be attempted with sense amplifier common mode inputs below VCC – 0.5V. Input referred offset tolerance vs VCM is shown in Figure 5d. VCC ≠ 5V The LT1620 sense amplifier induces a small additional offset when VCC moves away from 5V. This offset follows a linear characteristic and amounts to about ±0.33mV (input-referred) over the recommended operating range of VCC, centered at 5V. This offset is translated to the AVG and AVG2 outputs (times factors of 10 and 20), and thus to the programming voltages. A plot of programming offsets vs VCC is shown in Figure 5e. LT1620/LT1621 U W U U APPLICATIONS INFORMATION 40 20 VCC = 5V VID = 80mV VCM = 16.8V 20 VCC = 5V VCM = 16.8V IOUT = 130µA 10 VPROG OFFSET (mV) VPROG OFFSET (mV) 30 10 0 –10 0 –10 –20 –20 –30 –30 –40 50 0 100 200 150 IOUT SINK CURRENT (µA) –40 250 0 20 80 100 120 60 40 IN+ – IN– (VID) INPUT (mV) LT1620/21 • F05a LT1620/21 • F05b Figure 5a. Typical Setpoint Voltage (VPROG) Changes Slightly Depending Upon the Amount of Current Sinked by the IOUT Pin Figure 5b. Typical Setpoint Voltage (VPROG) Changes Slightly Depending Upon the Programmed Differential Input Voltage (VID) VPROG2 OFFSET (mV) ADDITIONAL INPUT REFERRED OFFSET (mV) 40 VCC = 5V VCM = 16.8V IOUT = 130µA 20 0 –20 –40 –60 –80 0 20 80 100 120 60 40 IN+ – IN– (VID) INPUT (mV) 140 ±14 VCC = 5V VID = 80mV IOUT = 130µA ±12 ±10 ±8 ±6 ±4 ±2 0 0 140 4 36 3 5 1 2 IN+, IN– COMMON MODE VOLTAGE (VCM) (V) LT1620/21 • F05d LT1620/21 • F05c Figure 5c. Typical Comparator Threshold Voltage (VPROG2) Changes Slightly Depending Upon the Programmed Differential Input Voltage (VID) Figure 5d. Sense Amplifier Input Offset Tolerence Degrades for Input Common Mode Voltage (VCM) Below (VCC – 0.5V). This Affects the SENSE, AVG and AVG2 Amplifier Outputs PROGRAMMING OFFSET (mV) 10 VID = 80mV VCM = 16.8mV IOUT = 130µA 5 VPROG2 0 VPROG –5 –10 4.50 4.75 5.00 5.25 5.50 VCC (V) LT1620/21 • F05e Figure 5e. Typical Setpoint Voltages for VPROG and VPROG2 Change Slightly Depending Upon the Supply Voltage (VCC) 9 LT1620/LT1621 U TYPICAL APPLICATIONS Programmable Constant Current Source D45VH10 6V TO 28V 0.1Ω IOUT 0A TO 1A 0.1µF 470Ω LT1121CS8-5 8 IN 0.1µF OUT SHDN 5 1 GND 3 SHUTDOWN + 0.1µF 1µF 18k 1 SENSE AVG 7 PROG LT1620MS8 3 6 VCC GND 2 VN2222LM 2N3904 22Ω 4 10k 1% 0.1µF 8 IOUT +IN –IN IPROG RPROG 5 IOUT = (IPROG)(10,000) RPROG = 40k FOR 1A OUTPUT LT1620/21 • TA01 High Efficiency Buck Constant Current Source 6V TO 15V 50µH CTX50-4 Si9405 + 22µF 25V TPS 0.05Ω + 4.7k MBRS130T3 2N4401 IOUT 0A TO 1A 22µF 25V TPS 10k 2N4403 5V 0.1µF 820Ω 10k 2N7002 0.047 µF 1 3 4.7k SENSE IOUT 1µF 5 6 8 AVG 20k 0.1µF 10k 1% 14 PROG LT1620GN 13 PROG2 GND AVG2 MODE –IN 16 VCC +IN 12 IPROG 11 9 RPROG 47k 2N7002 33k IOUT = (IPROG)(20,000) RPROG = 90k FOR 1A OUTPUT LT1620/21 • TA04 10 LT1620/LT1621 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. GN Package 16-Lead Plastic SSOP (Narrow 0.150) 0.189 – 0.196* (4.801 – 4.978) (LTC DWG # 05-08-1641) 16 15 14 13 12 11 10 9 0.015 ± 0.004 × 45° (0.38 ± 0.10) 0.0075 – 0.0098 (0.191 – 0.249) 0.229 – 0.244 (5.817 – 6.198) 0.053 – 0.069 (1.351 – 1.748) 0.150 – 0.157** (3.810 – 3.988) 0.004 – 0.009 (0.102 – 0.249) 0° – 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.025 (0.635) BSC 0.008 – 0.012 (0.203 – 0.305) 1 2 3 5 6 4 7 * DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 8 GN16 (SSOP) 0895 MS8 Package 8-Lead MSOP (LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.10) 8 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 0° – 6° TYP SEATING PLANE 0.021 ± 0.004 (0.53 ± 0.01) 7 6 5 0.006 ± 0.004 (0.15 ± 0.10) 0.118 ± 0.004** (3.00 ± 0.10) 0.192 ± 0.004 (4.88 ± 0.10) 0.012 (0.30) 0.025 (0.65) TYP * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE 1 2 3 4 MSOP08 0596 S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 7 6 5 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157** (3.810 – 3.988) 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) TYP 1 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 2 3 4 SO8 0996 11 LT1620/LT1621 U TYPICAL APPLICATION Electronic Circuit Breaker Si9434DY 0.033Ω 5V AT 1A PROTECTED 5V 0.1µF 1k FAULT CDELAY 100Ω 33k 2N3904 1 2 SENSE AVG 1N4148 8 7 PROG LT1620MS8 6 3 VCC GND 4 100k IOUT –IN +IN 4.7k 33k 5 TYPICAL DC TRIP AT 1.6A 3A FAULT TRIPS IN 2ms WITH CDELAY = 1.0µF 2N3904 LT1620/21 • TA03 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC®1435 High Efficiency Low Noise Synchronous Step-Down Switching Regulator 16-Pin Narrow SO and SSOP, VIN ≤ 36V, Programmable Constant Frequency LTC1436/LTC1436-PPL/ High Efficiency Low Noise Synchronous Step-Down LTC1437 Switching Regulator Controllers Full-Featured Single Controller, VIN ≤ 36V, Programmable Constant Frequency LTC1438/LTC1439 Dual High Efficiency Low Noise Synchronous Step-Down Switching Regulators Full-Featured Dual Controllers, VIN ≤ 36V, Programmable Constant Frequency LT1510 1.5A Constant-Current/Constant-Voltage Battery Charger Step-Down Charger for Li-Ion, NiCd and NiMH LT1511 3.0A Constant-Current/Constant-Voltage Battery Charger with Input Current Limiting Step-Down Charger that Allows Charging During Computer Operation and Prevents Wall-Adapter Overload LT1512 SEPIC Constant-Current/Constant-Voltage Battery Charger Step-Up/Step-Down Charger for up to 1A Charging Current LT1513 SEPIC Constant-Current/Constant-Voltage Battery Charger Step-Up/Step-Down Charger for up to 2A Charging Current LTC1538-AUX Dual High Efficiency Low Noise Synchronous Step-Down Switching Regulator 5V Standby in Shutdown, VIN ≤ 36V, Programmable Constant Frequency LTC1539 Dual High Efficiency Low Noise Synchronous Step-Down Switching Regulator 5V Standby in Shutdown, VIN ≤ 36V, Programmable Constant Frequency 12 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● (408) 432-1900 FAX: (408) 434-0507● TELEX: 499-3977 ● www.linear-tech.com 16201f LT/GP 0197 7K • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 1996