LTC4011CFE Linear Technology, LTC4011CFE Datasheet

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FeaTures Complete NiMH/NiCd Charger for Cells n No Microcontroller or Firmware Required n 550kHz Synchronous PWM Current Source Controller n No Audible Noise with Ceramic Capacitors n PowerPath™ Control Support n Programmable Charge Current: 5% Accuracy n Wide Input Voltage Range: 4.5V to 34V n Automatic Trickle Precharge n –∆V Fast Charge Termination n Optional ∆T/∆t Fast Charge Termination n Automatic NiMH Top-Off Charge n Programmable Timer n Automatic Recharge n Multiple Status Outputs n Micropower Shutdown n 20-Lead Thermally Enhanced TSSOP Package n applicaTions Integrated or Standalone Battery Charger n Portable Instruments or Consumer Products n Battery-Powered Diagnostics and Control n ...

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... CHEM GND V TEMP V CELL V CDIV TIMER EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB TO OBTAIN SPECIFIED THERMAL RESISTANCE PART MARKING PACKAGE DESCRIPTION LTC4011CFE 20-Lead Plastic TSSOP PART MARKING PACKAGE DESCRIPTION LTC4011CFE 20-Lead Plastic TSSOP (Note 4) The indicates specifications which apply over the full operating l = 25° 12V, BAT = 4.8V, GND = PGND = 0V, unless otherwise noted ...

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T SYMBOL PARAMETER Thermistor Termination V Output Voltage RT I Short-Circuit Current RT PWM Current Source V BAT – SENSE Full-Scale Regulation FS Voltage (Fast Charge) V BAT – SENSE Precharge Regulation ...

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LTC4011 elecTrical characTerisTics temperature range, otherwise specifications are at T SYMBOL PARAMETER T Maximum Fast Charge Temperature MAXC (Note Disable Threshold Voltage TEMP(D) TEMP V Pause Threshold Voltage TEMP(P) Charger Timing ∆t Internal Time Base Error TIMER ...

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Typical perForMance characTerisTics NiCd Charge Cycle at 1C NiMH Charge Cycle at 0.5C Automatic Recharge Threshold Voltage (per Cell) NiCd Charge Cycle at 2C Battery Present Threshold Voltage (per Cell) Battery Overvoltage Threshold Voltage (per Cell) LTC4011 Minimum Fast Charge Threshold Voltage (per Cell) –∆V Termination Voltage (per Cell) 4011fb  ...

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LTC4011 Typical perForMance characTerisTics Programmable Timer Accuracy Charger Efficiency OUT Fast Charge Current Output Regulation  Charge Current Accuracy Charger Soft-Start INFET Forward Regulation Voltage PWM Switching Frequency Fast Charge Current Line Regulation INFET OFF Delay Time 4011fb ...

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Typical perForMance characTerisTics PowerPath Switching 100µs/DIV Undervoltage Lockout Threshold Voltage Thermistor Disable Threshold Voltage Shutdown Quiescent Current Shutdown Threshold Voltage (DCIN – Pause Threshold Voltage LTC4011 PWM Input Bias Current (OFF) Charge Enable Threshold Voltage (V – BAT) CC 4011fb  ...

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LTC4011 Typical perForMance characTerisTics INTV Voltage DD pin FuncTions DCIN (Pin 1): DC Power Sense Input. The LTC4011 senses voltage on this pin to determine when an external DC power source is present. This input should be isolated from blocking diode or PowerPath FET. Refer to CC the Applications Information section for complete details. Operating voltage range is GND to 34V. FAULT (Pin 2): Active-Low Fault Indicator Output. The LTC4011 indicates various battery and internal fault condi- tions by connecting this pin to GND. Refer to the Operation and Applications Information sections for further details. This output is capable of driving an LED and should be left floating if not used. FAULT is an open-drain output to GND with an operating voltage range of GND to V ...

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FuncTions V (Pin 9): Average Cell Voltage Resistor Divider Termi- CDIV nation. The LTC4011 connects this pin to GND provided the charger is not in shutdown open-drain output CDIV to GND with an operating voltage range of GND to BAT. TIMER (Pin 10): Charge Timer Input. A resistor connected between TIMER and GND programs charge cycle timing limits. Refer to the Applications Information section for complete details. Operating voltage range is GND to 1V. SENSE (Pin 11): Charge Current Sense Input. An external resistor between this input and BAT is used to program charge current. Refer to the Applications Information section for complete details on programming charge current. Operating voltage ranges from (BAT – 50mV) to (BAT + 200mV). BAT (Pin 12): Battery Pack Connection. The LTC4011 uses the voltage on this pin to control current sourced from V to the battery during charging. Allowable operating CC voltage range is GND ...

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LTC4011 block DiagraM DCIN 1 FAULT 2 CHRG 3 CHEM 4 5 GND TEMP 7 V CELL 8 V CDIV 9 TIMER 10 0 THERMISTOR INTERFACE CHARGER STATE A/D CONTROL CONVERTER LOGIC BATTERY DETECTOR CHARGE TIMER ...

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Figure 1. LTC4011 State Diagram LTC4011 4011fb  ...

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LTC4011 operaTion (Refer to Figure 1) Shutdown State The LTC4011 remains in micropower shutdown until DCIN (Pin 1) is driven above V (Pin 18). In shutdown all status CC and PWM outputs and internally generated terminations or supply voltages are inactive. Current consumption from V and BAT is reduced to a very low level. CC Charge Qualification State Once DCIN is greater than V CC micropower shutdown, enables its own internal supplies, provides V voltage for temperature sensing, and switches GND to allow measurement of the average single- CDIV cell voltage. The IC also verifies that 510mV above BAT and V is between 350mV and CC CELL 1.95V below 350mV, no charging will occur, and CELL above 1.95V, the fault state is entered, which CELL ...

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Top-Off Charge State If NiMH fast charge termination occurs because the ∆T/∆t limit is exceeded after an initial period of t has expired, the LTC4011 enters the top-off charge state. Top-off charge is implemented by sourcing one-tenth the programmed charge current for t MAX that 100% charge has been delivered to the battery. The CHRG and TOC status outputs are active during the top-off state. If NiCd cells have been selected with the CHEM pin, the LTC4011 never enters the top-off state. Automatic Recharge State Once charging is complete, the automatic recharge state is entered to address the self-discharge characteristics of nickel chemistry cells. The charge status outputs are inactive during automatic recharge, but V switched to GND to monitor the average cell voltage. If the V voltage drops below 1.325V without falling below CELL 350mV, the charge timer is reset and a new fast charge cycle is initiated. The internal termination algorithms of the LTC4011 are adjusted when a fast charge cycle is initiated from auto- matic recharge, because the battery should be almost fully charged. Voltage-based termination is enabled immediately and the NiMH ∆T/∆t limit is fixed at a battery temperature rise of 1°C/minute. Fault State As discussed previously, the LTC4011 enters the fault state based on detection of invalid battery voltages during vari- ous charging phases. The IC also monitors the regulation of the PWM control loop and will enter the fault state if this is not within acceptable limits. Once in the fault state, ...

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LTC4011 operaTion PWM Current Source Controller An integral part of the LTC4011 is the PWM current source controller. The charger uses a synchronous step-down architecture to produce high efficiency and limited thermal dissipation. The nominal operating frequency of 550kHz allows use of a smaller external filter components. The TGATE and BGATE outputs have internally clamped volt- age swings. They source peak currents tailored to smaller surface-mount power FETs likely to appear in applications providing an average charge current less. During the various charging states, the LTC4011 uses the PWM controller to regulate an average voltage between SENSE and BAT that ranges from 10mV to 100mV. A conceptual diagram of the LTC4011 PWM control loop is shown in Figure 2. The voltage across the external current programming resistor R is averaged by integrating error amplifier SENSE EA. An internal programming current is also pulled from input resistor R1. The I • R1 product establishes the PROG desired average voltage drop across R the average ...

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External DC Source The external DC power source should be connected to the charging system and the V pin through either a power CC diode or P-channel MOSFET. This prevents catastrophic system damage in the event of an input short to ground or reverse-voltage polarity at the DC input. The LTC4011 auto- matically senses when this input is present. The open-circuit voltage of the DC source should be between 4.5V and 34V, depending on the number of cells being charged. In order to avoid low dropout operation, ensure 100% capacity at charge termination, and allow reliable detection of battery insertion, removal or overvoltage, the following equation can be used to determine the minimum full-load voltage that should be provided by the external DC power source. DCIN(MIN • 2V) + 0.3V where n is the number of series cells in the battery pack. The LTC4011 will properly charge over a wide range of DCIN and BAT voltage ...

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LTC4011 applicaTions inForMaTion Table 2. LTC4011 Charging Parameters CHEM BAT STATE PIN CHEMISTRY PC Both FC Open NiCd GND NiMH TOC GND NiMH AR Both PC: Precharge FC: Fast Charge (Initial –∆V Termination Hold Off of t TOC: Top-Off Charge (Only for NiMH ∆T/∆t FC Termination After Initial t AR: Automatic Recharge (Temperature Limits Apply to State Termination Only) Table 3. LTC4011 Time Limit Programming Examples TYPICAL FAST PRECHARGE LIMIT R CHARGE RATE TIMER 24.9k 2C 33.2k 1.5C 49.9k ...

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Thermistor Network Design The network for proper temperature sensing using a thermistor with a negative temperature coefficient (NTC) is shown in Figure only present for thermistors with an exponential temperature coefficient (β) above 3750. For thermistors with β below 3750, replace R3 with a short. BAT 12 10k 10k ...

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LTC4011 applicaTions inForMaTion operations. However, this practice is not recommended for NiMH cells charged well above or below their 1C rate, because fast charge termination based solely on voltage inflection may not be adequate to protect the battery from a severe overcharge. A resistor between 10k and 20k may be used to connect the pause function is TEMP RT still desired. INTV Regulator Output DD If BGATE is left open, the INTV pin of the LTC4011 can DD be used as an additional source of regulated voltage in the host system any time READY is active. Switching loads on INTV may reduce the accuracy of internal analog DD circuits used to monitor and terminate fast charging. In addition, DC current drawn from the INTV greatly increase internal power dissipation at elevated V voltages. A minimum ceramic bypass capacitor of 0.1µF is recommended. Calculating Average Power Dissipation The user should ensure that the maximum rated IC junction temperature is not exceeded under all operating conditions. ...

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FROM ADAPTER 12V FROM ADAPTER 12V Figure 7. 3A NiMH Charger with Full PowerPath Control A full-featured 2A LTC4011 application is shown in Figure 8. FET-based PowerPath allows for maximum input voltage range from the DC adapter. The inherent voltage ratings of the SENSE and BAT pins allow charging CELL CDIV of one to sixteen series nickel cells in this application, governed only by the V overhead limits previously dis- CC cussed. The application includes all average cell voltage INFET FAULT CHRG TOC READY 10µH 10µF 0.1µF Figure 6. Minimum 1A LTC4011 Application ...

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LTC4011 applicaTions inForMaTion While the LTC4011 is a complete, standalone solution, Figure 9 shows that it can also be interfaced to a host microprocessor. The host MCU can control the charger directly with an open-drain I/O port connected to the V pin, if that port is low leakage and can tolerate at least FROM ADAPTER 12V FROM ADAPTER 24V PAUSE FROM MCU 0 2V. The charger state is monitored on the four LTC4011 status outputs. Charging of NiMH batteries is selected in this example. However, NiCd (CHEM → V could be chosen as well. TEMP INFET FAULT D4 CHRG TOC READY ...

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Unlike all of the other applications discussed so far, the battery continues to power the system during charging. The MCU could be powered directly from the battery or from any type of post regulator operating from the battery. In this configuration, the LTC4011 relies expressly on the ability of the host MCU to know when load transients will be encountered. The MCU should then pause charging (and thus –∆V processing) during those events to avoid premature fast charge termination. If the MPU cannot reli- ably perform this function, full PowerPath control should be implemented. In most applications, there should not be an external load on the battery during charge. Excessive battery load current variations, such as those generated by a post-regulating PWM, can generate sufficient voltage noise to cause the LTC4011 to prematurely terminate a charge cycle and/or prematurely restart a fast charge. In this case, it may be necessary to inhibit the LTC4011 after charging is complete until external gas gauge circuitry indicates that recharging is necessary. Shutdown power is applied to the LTC4011 through the body diode this application. Waveforms Sample waveforms for a standalone application during a typical charge cycle are shown in Figure 10. Note that these waveforms are not to scale and do not represent the ...

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LTC4011 applicaTions inForMaTion READY (PAUSE) CHRG TOC V TIMER CHEM TEMP + 10k 66.5k NTC – Figure 11. NiCd Battery Pack with Time Limit Control A second possibility is to configure an LTC4011-based charger to accept battery packs with varying numbers of cells. By including R2 of the average cell voltage divider network shown in Figure 3, battery-based programming of the number of series-stacked cells could be realized without defeating LTC4011 detection of battery insertion or removal. Figure 12 shows a 2-cell NiMH battery pack that programs the correct number of series cells when it is connected to the charger, along with indicating chemistry and providing temperature information. Any of these battery pack charge control concepts could be combined in a variety of ways to service custom application ...

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Vias should not be used to make these connections. 2. Place the LTC4011 close to the switching FET gate terminals, keeping the connecting traces short to produce clean drive signals. This rule also applies to IC supply and ground pins that connect to the switching FET source pins. The IC can be placed on the opposite side of the PCB from the switching FETs. 3. Place the inductor input as close as possible to the drain of the switching FETs. Minimize the surface area of the switch node. Make the trace width the minimum needed to support the programmed charge current. Use no copper fills or pours. Avoid running the con- nection on multiple copper layers in parallel. Minimize ...

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LTC4011 package DescripTion 6.60 ±0.10 4.50 ±0.10 SEE NOTE 4 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 0.50 – 0.75 (.0035 – .0079) (.020 – .030) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE ...

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... REV DATE DESCRIPTION B 01/10 Changes to Typical Application Updated Order Information Section Changes to Electrical Characteristics Changes to Operation Section Changes to Applications Information Changes to Figures 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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. LTC4011 PAGE NUMBER 12, 13, 14 15, 16, 19, 21, 22 19, 20 ...

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... Level 2 Charger Operates with or without MCU Host, SMBus Rev. 1.1 Compliant High Side Sense of Charge Quantity and Polarity in a 10-Pin MSOP No External MOSFET, Automatic Switching Between DC Sources, Simplified, 140mΩ On Resistance, ThinSOT™ Package Very Low Loss Replacement for Power Supply ORing Diodes Using Minimal External Components, 3V ≤ V Low Loss Replacement for ORing Diodes, 100mΩ On Resistance www.linear.com ● ≤ 28V, (3V ≤ V ≤ 36V for HV 4011fb LT 0110 REV B • PRINTED IN USA  LINEAR TECHNOLOGY CORPORATION 2005 ...