LT1621CGN

LT1620 LINER | Alldatasheet

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n Accurate Output Current Programming n Usable in Charging Applications Up to 32V Output n Programmable Load Current Monitor for End-of- Charging-Cycle Notification (16-Pin Version) n Dual Function IC (LT1621) Allows Convenient Integration of Load and Input Current Sensing n Level-Shifted Current Sense Output for Current Mode PWM Controllers n Can be Used for NiCd, NiMH, Lead-Acid and Lithium- Ion Battery Charging n Greater than 96% Efficiency Possible in Charger

Applications

n High Output Currents Possible: > 10A Easily Obtained D UESCRIPTIO 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 restric- tion 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 program- mable 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. UA OPPLICATITYPICAL , LTC and LT are registered trademarks of Linear Technology Corporation. BATTERY CHARGE CURRENT (A) EFFICIENCY (%) 100 1620/21 • TA02 1 2 3 5 VIN = 24V VBATT = 16V VBATT = 12V VBATT = 6V Efficiency Figure 1. Low Dropout, High Current Li-Ion Battery Charger

A UGWA WU WARBSOLUTEX I T I S Programming Voltage: IOUT, SENSE, AVG, AVG2, (Referenced to Ground) (Note 1) Operating Ambient Temperature Range WU UPACKAGE/ORDER I FOR ATIO ORDER PART NUMBER ORDER PART NUMBER θJA = 149°C/W TOP VIEW GN PACKAGE 16-LEAD PLASTIC SSOP SENSE NC IOUT NC GND MODE NC IN– AVG NC PROG PROG2 AVG2 V CC NC IN+ θJA = 149°C/W TOP VIEW GN PACKAGE 16-LEAD PLASTIC SSOP PROG A AVG A SENSE A IOUT A GND B IN– B IN+ B VCC B VCC A IN+ A IN– A GND A I OUT B SENSE B AVG B PROG B LT1620CGN LT1620IGN LT1621CGN LT1621IGN TOP VIEW AVG PROG V CC IN+ SENSE IOUT GND IN– MS8 PACKAGE 8-LEAD PLASTIC MSOP S8 PACKAGE 8-LEAD PLASTIC SO ORDER PART NUMBER MS8 PART MARKING BC Consult factory for Military grade parts. VIN+ = 16.8V, VCC = 5V, VIOUT = 2V, TA = 25°C unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Supply VCC 5V Supply Voltage l 4.5 5.0 5.5 V ICC DC Active Supply Current SENSE = AVG = PROG = PROG2 = V CC 2.8 3.8 mA LT1620GN 4.5V ≤ VCC ≤ 5.5V, IN+ – IN– = 100mV l 4.0 mA DC Active Supply Current SENSE = AVG = PROG = V CC 2.3 3.3 mA LT1620S8, LT1620MS8, 1/2 LT1621GN 4.5V ≤ VCC ≤ 5.5V, IN+ – IN– = 100mV l 3.7 mA DC Active Supply Current SENSE = AVG = PROG = V CC 1.3 1.9 mA LT1620S8, LT1620MS8, 1/2 LT1621GN 4.5V ≤ VCC ≤ 5.5V, IN+ – IN– = 0mV l 2.1 mA Current Sense Amplifier VCM Input Common Mode Range l 03 2 V VID Differential Input Voltage Range 0V ≤ VCM ≤ 32V l 0 125 mV (IN+ – IN–) VOSSENSE Input Offset - Measured at ×1 Output V CC ≤ VCM ≤ 32V –5 5 mV (VSENSE)V ID = 80mV l –6 6 mV ELECTRICAL C CHARA TERISTICS LT1620CS8 LT1620IS8 LT1620CMS8 θJA = 250°C/W (MS) θJA = 120°C/W (S)

ELECTRICAL C CHARA TERISTICS IN+ = 16.8V, VCC = 5V, VIOUT = 2V, TA = 25°C unless otherwise noted. The l denotes specifications which apply over the full operating temperature range. 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 V CC is removed, even with common mode voltage present at IN +, IN–. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Current Sense Amplifier VOSAVG Input Offset - Measured at ×10 Output V CC ≤ VCM ≤ 32V –3 3 mV (VAVG) 35mV ≤ VID ≤ 125mV l –4 4 mV VCM = 0V, VID = 80mV l –10 15 mV VOSAVG2 Input Offset - Measured at × 20 Output V CC ≤ VCM ≤ 32V – 3 3 mV (VAVG2) 0V ≤ VID ≤ 35mV l –4 4 mV VSENSE No-Load Output Offset 0V ≤ VCM ≤ 32V, VID = 0V, Referenced to VCC l –0.1 –3 mV IB(IN+, IN–) Input Bias Current (Sink) V CC ≤ VCM ≤ 32V (Note 2) 200 270 400 µA l 185 430 µA Input Bias Current (Source) V CM = 0V (Note 2) 4.0 5.25 mA l 5.50 mA Transconductance Amplifier g m Amplifier Transconductance 3000 3500 4000 µmho l 2200 4800 µmho AV Amplifier Voltage Gain 1V ≤ VIOUT ≤ 3V 60 80 dB VOLIOUT IOUT Saturation Limit (Sink) I IOUT = 50µA l 0.05 0.15 V IIOUT = 200µA l 0.10 0.30 V IIOUT = 1mA l 0.35 0.65 V VPROG PROG Input Range l VCC – 1.25 V CC V IBPROG Input Bias Current Measured at PROG Pin 20 nA VOSPROG Input Offset Voltage I IOUT = 130µA– 7 7 m V (VAVG – VPROG) l –8 8 mV End-of-Cycle Comparator VPROG2 PROG2 Input Range l VCC – 2.5 V CC – 0.15 V VHYST Input Hysteresis Measured at AVG2 Pin 15 mV IBPROG2 Input Bias Current Measured at PROG2 Pin 20 nA VOLMODE Output Logic Low Output (Sink) I MODE = 0.5mA l 0.1 0.5 V IMODE = 10mA l 0.5 1.2 V PI FU CTIO S U UU ensure continuity around zero inductor current. Typical out- put is –3mV with differential input voltage (IN+ – IN–) = 0. AVG: Sense Amplifier A V = –10 Output and Transconductance Amplifier Positive Input. Used as inte- gration node for average current control. Integration time constant is calculated using 2.5kΩ typical output imped- ance. PROG: Transconductance Amplifier Negative Input. Pro- gram node for average current delivered to load during current mode operation. Average current delivered to load imposes voltage differential at current sense amplifier 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 A V = –1 Output. Used as level- shifted output for PWM controller current sense input. The sense output is designed to have an inherent offset to

input (across external sense resistor) equal to (V CC – VPROG)/10. Input voltage range is VCC to (VCC – 1.25V). 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. 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 equals (V CC – VPROG2)/20. Input voltage range is (VCC – 0.15V) to (VCC – 2.5V). GND: Ground Reference. MODE: Comparator Open Collector Output. Output is logic low when magnitude of current sense amplifier differential input voltage is less than (VCC – VPROG2)/20. IOUT: Transconductance Amplifier Output. In typical appli- cation, IOUT sinks current from current-setting node on companion PWM controller IC, facilitating current mode loop control. FUNCTIONAL BLOCK DIAGRA UU W SENSE AMPLIFIER VCC IN+ IN– PROG PROG2* 500Ω 2.5k SENSE AVG AVG2* IOUT MODE* LT1620/21 • FBD gm *AVAILABLE IN THE LT1620GN ONLY +– +– SENSE– SENSE+ INTVCC ITH PWM CONTROLLER END-OF-CYCLE (ACTIVE LOW) (×1 GAIN) (×10 GAIN) (×20 GAIN) CURRENT SENSE RESISTOR VID GND OPERATIONU 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 refer- enced to the V CC supply by pulling signal current through internal VCC referred resistors. (Refer to the Functional Block Diagram) The first output (SENSE) is a unity gain, level-shifted repre- sentation 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 compara- tor, respectively. The AVG output yields a gain of 10, and the AVG2 output provides a gain of 20. These pins are

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 (V PROG) 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 130 µA (Refer to the Functional Block Diagram) with VAVG = VPROG. In typical PWM/charger type applica- tions, 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 charg- ing 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 V AVG2 voltage is more positive than VPROG2 (output current below the programmed threshold). APPLICATIONS INFORMATIONWU UU In Figure 2, an LT1620MS8 is coupled with an LTC1435 switching regulator in a high performance lithium-ion battery charger application. The LTC1435 switching regu- lator 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 func- tionality, 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 V IN 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 pro- grammed 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. R SENSE Selection The LT1620 will operate throughout a current program- ming 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 R SENSE 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 resis- tor 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.

Figure 2. LT1620/LTC1435 Battery Charger should be decoupled to the VCC supply. ate value as described above.

ICs, and each IC should have a dedicated capacitor. LT1620GN, including the end-of-cycle (EOC) flag feature. usually a given percentage of maximum load. current sense voltage has fallen to 0.5V/20 or 0.025V. system functions simultaneously require high currents. Figure 3. End-of-Cycle Flag Implementation with LT1620GN Figure 4. Input Current Sensing Application

7 VIN

6 S/S 2

4 GND

APPLICATIONS INFORMATIONWU UU 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 (V CC – V PROG) 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 con- trols 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 gen- erate its necessary output current translates to input offset error. The LT1620 is designed for a typical I OUT sink current of 130µA to help reduce this term. Knowing the current source capability of the associated PWM control- ler in a given application will enable adjustment of the required programming voltage to accommodate the de- sired charge current. A plot of typical V PROG 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 closed- loop 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 voltage VPROG. A plot of typical V PROG 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 addi- tional 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 V PROG2 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 tol- erance 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 V CC – 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 V CC, 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 V CC is shown in Figure 5e.

High Efficiency Buck Constant Current Source Programmable Constant Current Source AVG PROG VCC +IN SENSE LT1620MS8 7IOUT GND –IN 0.1µF 10k RPROG 18k 0.1µF 1µF IPROG 2N3904 22Ω VN2222LM OUTIN GNDSHDN SHUTDOWN 0.1µF TO 28V 470Ω 0.1Ω LT1121CS8-5 0.1µF IOUT 0A TO 1A IOUT = (IPROG)(10,000) RPROG = 40k FOR 1A OUTPUT LT1620/21 • TA01 D45VH10 AVG PROG PROG2 +IN SENSE LT1620GN 14IOUT GND AVG26 MODE VCC8 –IN 47k 0.047µF IOUT 0A TO 1A LT1620/21 • TA04 MBRS130T3 20k 0.1µF 10k IPROG RPROG 10k820Ω 4.7k 1µF 33k 2N7002 2N7002 2N4403 2N4401 10k 4.7k Si9405 22µF 25V TPS 22µF 25V TPS 0.1µF 6V TO 15V 50µH CTX50-4 0.05Ω IOUT = (IPROG)(20,000) RPROG = 90k FOR 1A OUTPUT

Dimensions in inches (millimeters) unless otherwise noted. 16-Lead Plastic SSOP (Narrow 0.150) (LTC DWG # 05-08-1641) GN16 (SSOP) 0895 * 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 12 3 4 5 6 7 8 0.229 – 0.244 (5.817 – 6.198) 0.150 – 0.157 (3.810 – 3.988) 16 15 14 13 0.189 – 0.196* (4.801 – 4.978) 12 11 10 9 0.016 – 0.050 (0.406 – 1.270) 0.015 – 0.004 (0.38 – 0.10) × 45° 0° – 8° TYP0.0075 – 0.0098 (0.191 – 0.249) 0.053 – 0.069 (1.351 – 1.748) 0.008 – 0.012 (0.203 – 0.305) 0.004 – 0.009 (0.102 – 0.249) 0.025 (0.635) BSC 1 2 3 4 0.150 – 0.157** (3.810 – 3.988) 8 7 6 5 0.189 – 0.197* (4.801 – 5.004) 0.228 – 0.244 (5.791 – 6.197) 0.016 – 0.050 0.406 – 1.270 0.010 – 0.020 0°– 8° TYP 0.008 – 0.010 (0.203 – 0.254) SO8 0996 0.053 – 0.069 (1.346 – 1.752) 0.014 – 0.019 (0.355 – 0.483) 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) TYPDIMENSION 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-Lead MSOP (LTC DWG # 05-08-1660) 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) MSOP08 0596 * 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 12 3 4 0.192 – 0.004 (4.88 – 0.10) 8 7 6 5 0.118 – 0.004* (3.00 – 0.10) 0.118 – 0.004** (3.00 – 0.10) 0.021 – 0.004 (0.53 – 0.01) 0° – 6° TYP SEATING PLANE 0.007 (0.18) 0.040 – 0.006 (1.02 – 0.15) 0.012 (0.30) 0.006 – 0.004 (0.15 – 0.10) 0.025 (0.65) TYP 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.

 LINEAR TECHNOLOGY CORPORA TION 1996 16201f LT/GP 0197 7K • PRINTED IN USA TYPICAL APPLICATIONU Electronic Circuit Breaker AVG PROG VCC +IN SENSE LT1620MS8 7IOUT GND –IN 4.7k 33k 100k 33k CDELAY 0.1µF 0.033Ω 5V AT 1A PROTECTED FAULT LT1620/21 • TA03 1N4148 2N3904 2N3904 Si9434DY 100Ω TYPICAL DC TRIP AT 1.6A 3A FAULT TRIPS IN 2ms WITH C DELAY = 1.0µF RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC®1435 High Efficiency Low Noise Synchronous Step-Down 16-Pin Narrow SO and SSOP, V IN ≤ 36V, Programmable Switching Regulator Constant Frequency LTC1436/LTC1436-PPL/ High Efficiency Low Noise Synchronous Step-Down Full-Featured Single Controller, V IN ≤ 36V, Programmable LTC1437 Switching Regulator Controllers Constant Frequency LTC1438/LTC1439 Dual High Efficiency Low Noise Synchronous Step-Down Full-Featured Dual Controllers, V IN ≤ 36V, Programmable Switching Regulators 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 Step-Down Charger that Allows Charging During Computer with Input Current Limiting 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 5V Standby in Shutdown, V IN ≤ 36V, Programmable Switching Regulator Constant Frequency LTC1539 Dual High Efficiency Low Noise Synchronous Step-Down 5V Standby in Shutdown, V IN ≤ 36V, Programmable Switching Regulator Constant Frequency Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 l (408) 432-1900 FAX: (408) 434-0507 l TELEX: 499-3977 l www.linear-tech.com