LT1505

LT1505_15 LINER | Alldatasheet

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Figure 1. Low Dropout 4A Lithium-Ion Battery Charger

1505 PWM battery charger controller fast charges

series Li-Ion cells with 0.5% accuracy. current drops to 20% of the programmed value. The LT1505 is available in a 28-pin SSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation.

• 2 0.68mF VBAT 12.6V BATTERY * DBODY IS THE BODY DIODE OF M3 CIN: SANYO OS-CON L1: SUMIDA CDRH127-150 (CAN BE FROM 10µH TO 30µH) Si4412 Si4412 MBRS140 MMSD4148T1 MMSD4148T1 500W 100k *BODY DIODE POLARITY MUST BE AS SHOWN R 0.025W Si4435 DBODY* TO SYSTEM POWER VIN (FROM ADAPTER) RS1 0.025W 15mH

1505 F01

3 CELL

V ABSOLUTE MAXIMUM RATINGSW WW U (Note 1) Operating Junction Temperature Range .... 0°C to 125°C ORDER PART NUMBER LT1505CG LT1505CG-1 ORDER PART NUMBER TJMAX = 125°C, qJA = 100°C/ W Consult LTC Marketing for parts specified with wider operating temperature ranges. TOP VIEW G PACKAGE 28-LEAD PLASTIC SSOP BOOST TGATE SW SYNC SHDN AGND UV INFET CLP CLN COMP1 CAP FLAG 4.1V PGND BGATE GBIAS BOOSTC V CC BAT SPIN SENSE BAT2 PROG V C VFB 3CELL 4.2V TJMAX = 125°C, qJA = 100°C/ W TOP VIEW G PACKAGE 28-LEAD PLASTIC SSOP BOOST TGATE SW SYNC SHDN AGND UV INFET NC NC GND CAP FLAG 4.1V PGND BGATE GBIAS BOOSTC V CC BAT SPIN SENSE BAT2 PROG V C VFB 3CELL 4.2V NOTE: LT1505CG-1 DOES NOT HAVE INPUT CURRENT LIMITING FUNCTION.

ELECTRICAL CHARACTERISTICS

PACKAGE/ORDER INFORMATIONW UU The l denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 18V, VBAT = 12.6V, VCLN = VCC (LT1505), no load on any outputs unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Overall Supply Current V CC £ 24V l 12 15 mA Sense Amplifier CA1 Gain and Input Offset Voltage 11V £ VCC £ 24V , 0V £ VBAT £ 20V (With RS2 = 200W , RS3 = 200W )R PROG = 4.93k 95 100 105 mV (Measured across RS1, Figure 1) (Note 2) R PROG = 4.93k l 92 108 mV RPROG = 49.3k 7 10 13 mV BOOST Pin Current V BOOST = VSW + 8V, 0V £ VSW £ 20V TGATE High 2 3 mA TGATE Low 2 3 mA BOOSTC Pin Current V BOOSTC = VCC + 8V 1 mA Reference Reference Voltage (Note 3) R PROG = 4.93k, Measured at VFB with VA 2.453 2.465 2.477 V Supplying IPROG and Switching Off Reference Voltage Tolerance 11V £ VCC £ 24V l 2.441 2.489 V

PARAMETER CONDITIONS MIN TYP MAX UNITS Preset Battery Voltage (12.3V, 16.4V, 12.6V, 16.8V) All Preset Battery Voltages Measured at BAT2 Pin 0.5 % Preset Battery Voltage Tolerance (V BAT + 0.3V) £ VCC £ 24V l –1 1 % BAT2 Pin Input Current V BAT2 = VPRESET – 1V l 6 mA Voltage Setting Resistors Tolerance (R4, R5, R6, R7) – 40 40 % Shutdown Undervoltage Lockout (TGATE and BGATE “Off”) Measured at UV Pin l 6.3 6.7 7.25 V Threshold (Note 9) UV Pin Input Current 0V £ VUV £ 8V l –1 5 mA Reverse Current from Battery in Micropower V BAT £ 20V, VUV £ 0.4V, 10 50 mA Shutdown (Note 10) V CC = VSW = Battery Voltage Shutdown Threshold at SHDN Pin When VCC l 12 V is Connected SHDN Pin Current 0V £ VSHDN £ 3V 8 mA Supply Current in Shutdown V CC £ 24V 15 20 mA (VSHDN is Low, VCC is Connected) Minimum IPROG for Switching “On” –1 –4 – 22 mA Minimum IPROG for Switching “Off” at VPROG £ 1V l –1 –2.4 mA Current Sense Amplifier CA1 Inputs (SENSE, BAT) Input Bias Current (SENSE, BAT) V SHDN = High l – 50 –120 mA VSHDN = Low (Shutdown) – 10 mA Input Common Mode Low l – 0.25 V Input Common Mode High l VCC – 0.3 V SPIN Input Current V SHDN = High, VSPIN ‡ 2V (Note 8) l 2m A VSHDN = Low (Shutdown) 10 mA Oscillator Switching Frequency (fNOM) 180 200 220 kHz Switching Frequency Tolerance l 170 200 230 kHz SYNC Pin Input Current V SYNC = 0V –0.5 mA VSYNC = 2V – 30 mA Synchronization Pulse Threshold on SYNC Pin 0.9 1.2 2.0 V Synchronization Frequency l 240 280 kHz Maximum Duty Cycle VBOOST Threshold to Turn TGATE Off Measured at (V BOOST – VSW) (Comparator A2) (Note 4) Low to High l 6.8 7.3 7.6 V Hysteresis 0.25 V Maximum Duty Cycle of Natural Frequency 200kHz l 85 90 % (Note 5) Current Amplifier CA2 Transconductance V C = 1V, IVC = –1mA 150 200 300 mmho Maximum VC for Switch Off l 0.6 V IVC Current (Out of Pin) V C ‡ 0.6V l 50 mA VC < 0.45V l 3m A VC at Shutdown V SHDN = Low (Shutdown) l 0.35 V ELECTRICAL CHARACTERISTICSThe l denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 18V, VBAT = 12.6V, VCLN = VCC (LT1505), no load on any outputs unless otherwise noted.

Note 6: See “Lithium-Ion Charging Completion” in the Applications Information Section. Note 7: Tested with Test Circuit 3. Note 8: ISPIN keeps switching on to keep VBAT regulated when battery is not present to avoid high surge current from COUT when battery is inserted. Note 9: Above undervoltage threshold switching is enabled. Note 10: Do not connect VCC directly to VIN (see Figure 1). This connection will cause the internal diode between VBAT and VCC to be forward-biased and may cause high current to flow from VIN. When the adapter is removed, VCC will be held up by the body diode of M1. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Tested with Test Circuit 1. Note 3: Tested with Test Circuit 2. Note 4: When VCC and battery voltage differential is low, high duty factor is required. The LT1505 achieves a duty factor greater than 99% by skipping cycles. Only when VBOOST drops below the comparator A2 threshold will TGATE be turned off. See Applications Information. Note 5: When the system starts, C2 (boost cap) has to be charged up to drive TGATE and to start the system. The LT1505 will keep TGATE off and turn BGATE on for 0.2ms at 200kHz to charge up C2. Comparator A2 senses VBOOST and switches to the normal PWM mode when VBOOST is above the threshold. ELECTRICAL CHARACTERISTICSThe l denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 18V, VBAT = 12.6V, VCLN = VCC (LT1505), no load on any outputs unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Voltage Amplifier VA Transconductance (Note 3) Output Current from 50 mA to 500mA 0.21 0.6 1.0 mho Output Source Current V FB = VPROG = VREF + 10mV 1.1 mA VFB Input Bias Current At 0.5mA VA Output Current, T A < 70°C – 10 25 nA (3 CELL, 4.1V, 4.2V Are Not Connected, VBAT2 = 0V) Current Limit Amplifier CL1 Turn-On Threshold 0.5mA Output Current 87 92 97 mV Transconductance Output Current from 50 mA to 500mA 0.5 1 3 mho CLP Input Current 0.5mA Output Current 1 3 mA CLN Input Current 0.5mA Output Current 0.8 2 mA Input P-Channel FET Driver (INFET) INFET “On” Clamping Voltage (VCC – VINFET)V CC ‡ 11V l 6.5 7.8 9 V INFET “On” Driver Current V INFET = VCC – 6V l 82 0 m A INFET “Off” Clamping Voltage (VCC – VINFET)V CC Not Connected, IINFET < –2 mA 1.4 V INFET “Off” Drive Current V CC Not Connected, (VCC – VINFET) ‡ 2V –2.5 mA Charging Completion Flag (Comparator E6) Charging Completion Threshold (Note 6) Measured at V RS1, VCAP = 2V (Note 7) 14 20 28 mV Threshold On CAP Pin Low to High Threshold l 3.3 4.2 V High to Low Threshold l 0.6 V VCAP at Shutdown V SHDN = Low (Shutdown) l 0.13 0.3 V FLAG (Open Collector) Output Low V CAP = 4V, IFLAG < 1mA l 0.3 V FLAG Pin Leakage Current V CAP = 0.6V l 3 mA Gate Drivers (TGATE, BGATE) VGBIAS 11V < VCC < 24V, IGBIAS £ 15mA l 8.4 9.1 9.6 V VSHDN = Low (Shutdown) l 13 V VTGATE High (VTGATE – VSW)I TGATE £ 20mA, VBOOST = VGBIAS – 0.5V l 5.6 6.6 V VBGATE High I BGATE £ 20mA l 6.2 7.2 V VTGATE Low (VTGATE – VSW)I TGATE £ 50mA l 0.8 V VBGATE Low I BGATE £ 50mA l 0.8 V Peak Gate Drive Current 10nF Load 1 A Gate Drive Rise and Fall Time 1nF Load 25 ns VTGATE, VBGATE at Shutdown V SHDN = Low (Shutdown) l 1V ITGATE = IBGATE = 10mA

TYPICAL PERFORMANCE CHARACTERISTICS UW IBAT (A) EFFICIENCY (%) 105 100

1505 G01

VIN = 19V VBAT = 12.6V Efficiency of Figure 1 Circuit IVA (mA) ∆VFB (mV) 0.8

1505 G04

125°C 25°C VCC (V) ICC (mA)

1505 G06

0°C 25°C 125°C IGBIAS (mA) 9.2 9.1 9.0 8.9 8.8 8.7 8.6 8.5 8.4 8.3 8.1 VGBIAS (V)

1505 G02

0°C 25°C 125°C VGBIAS vs IGBIAS DVFB vs IVA (Voltage Amplifier) TEMPERATURE (°C) 0 2 55 07 5 1 0 0 THRESHOLD (mV) 125

1505 G05

JUNCTION TEMPERATURE (°C) REFERENCE VOLTAGE (V) 2.470 2.468 2.466 2.464 2.462 2.460 2.458 25 50 75 100

1505 G09

Reference Voltage vs Temperature VPROG (V) 0123 54 IPROG (mA)

1505 G07

125°C CURRENT FEEDBACK AMPLIFIER OPEN LOOP 25°C PROG Pin Characteristics VC (V) –1.2 –1.0 –0.8 –0.6 –0.4 –0.2 0.2 0.4 0.6 0.8 1.0 IVC (mA)

1505 G08

VCC (V) ∆VREF (V) 0.003 0.002 0.001 –0.001 –0.002 –0.003 5 10 15 20

1505 G03

0°C ≤ TJ ≤ 125°C

BOOST (Pin 1): This pin is used to bootstrap and supply power for the topside power switch gate drive and control circuity. In normal operation, VBOOST is powered from an internally generated 8.6V regulator VGBIAS, VBOOST » VCC + 9.1V when TGATE is high. Do not force an external voltage on BOOST pin. TGATE (Pin 2): This pin provides gate drive to the topside power FET. When TGATE is driven on, the gate voltage will be approximately equal to VSW + 6.6V. A series resistor of 5W to 10W should be used from this pin to the gate of the topside FET. SW (Pin 3): This pin is the reference point for the floating topside gate drive circuitry. It is the common connection for the top and bottom side switches and the output inductor. This pin switches between ground and V CC with very high dv/dt rates. Care needs to be taken in the PC layout to keep this node from coupling to other sensitive nodes. A 1A Schottky clamp diode should be placed from this pin to the ground pin, using very short traces to prevent the chip substrate diode from turning on. See Applications Information for more details. SYNC (Pin 4): Synchronization Input. The LT1505 can be synchronized to an external clock with pulses that have duty cycles between 10% and 95%. An internal one shot that is triggered on the rising edge of the sync pulse makes this input insensitive to the duty cycle of the sync pulse. The input voltage range on this pin is 0V to 20V. This pin can float if not used. SHDN (Pin 5): Shutdown. When this pin is pulled below 1V, switching will stop, GBIAS will go low and the input cur- rents of CA1 will be off. Note that input current of about 4mA keeps the device in shutdown unless an external pull-up signal is applied. The voltage range on this pin is 0V to V CC. AGND (Pin 6): Low Current Analog Ground. UV (Pin 7): Undervoltage Lockout Input. The rising thresh- old is 6.7V with a hysteresis of 0.5V. Switching stops in undervoltage lockout. When the input supply (normally the wall adapter output) to the chip is removed, the UV pin must be pulled down to below 0.7V (a 5k resistor from adapter output to GND is required), otherwise the reverse- battery current will be approximately 200 mA instead of 10mA. Do not leave the UV pin floating. If it is connected to V IN with no resistor divider, the built-in 6.7V undervoltage lockout will be effective. Maximum voltage allowed on this pin is V CC. INFET (Pin 8): For very low dropout applications, an external P-channel MOSFET can be used to connect the input supply to V CC. This pin provides the gate drive for the PFET. The gate drive is clamped to 8V below VCC. The gate is driven on (low) when V CC >( V BAT + 0.2V) and VUV > 6.7V. The gate is off (high) when VCC < (VBAT + 0.2V). The body diode of the PFET is used to pull up VCC to turn on the LT1505. CLP (Pin 9): LT1505: Positive Input to the Input Current Limit Amplifier CL1. The threshold is set at 92mV. When used to limit input current, a filter is needed to filter out the 200kHz switching noise. (LT1505-1: No Connection.) CLN (Pin 10): LT1505: Negative Input to the Input Current Limit Amplifier CL1. When used, both CLP and CLN should be connected to a voltage higher than 6V and normally V CC (to the VCC bypass capacitor for less noise). Maximum voltage allowed on both CLP and CLN is V CC + 1V. (LT1505-1: No Connection.) COMP1 (Pin 11): LT1505: Compensation Node for the Input Current Limit Amplifier CL1. At input adapter current limit, this pin rises to 1V. By forcing COMP1 low with an external transistor, amplifier CL1 will be disabled (no adapter current limit). Output current is less than 0.2mA. See the Figure 1 circuit for the required resistor and capacitor values. (LT1505-1: connect to GND.) CAP (Pin 12): A 0.1mF capacitor from CAP to ground is needed to filter the sampled charging current signal. This filtered signal is used to set the FLAG pin when the charging current drops below 20% of the programmed maximum charging current. FLAG (Pin 13): This pin is an open-collector output that is used to indicate the end of charge. The FLAG pin is driven low when the charge current drops below 20% of the programmed charge current. A pull-up resistor is required if this function is used. This pin is capable of sinking at least 1mA. Maximum voltage on this pin is V CC. 4.1V (Pin 14), 4.2V (Pin 15), 3CELL (Pin 16), V FB (Pin 17): These four pins are used to select the battery voltage using the preset internal resistor network. The VFB pin is

the noninverting input to the amplifier, VA in the Block Diagram, that controls the charging current when the device operates in constant voltage mode. The amplifier VA controls the charging current to maintain the voltage on the V FB pin at the reference voltage (2.465V). Input bias current for VA is approximately 3nA. The LT1505 incorpo- rates a resistor divider that can be used to select the correct voltage for either three or four 4.1V or 4.2V lithium-ion cells. For three cells the 3CELL pin is shorted to the V FB pin. For four cells the 3CELL pin is not con- nected. For 4.1V cells the 4.1V pin is connected to the VFB pin and the 4.2V pin is not connected. For 4.2V cells the 4.2V pin is connected to V FB and the 4.1V pin is not connected. See the table below. PRESET BATTERY VOLTAGE PIN SELECTION 12.3V (3 · 4.1V Cell) 4.1V, V FB, 3CELL Short Together 16.4V (4 · 4.1V Cell) 4.1V, V FB, Short Together, 3CELL Floats 12.6V (3 · 4.2V Cell) 4.2V, V FB, 3CELL Short Together 16.8V (4 · 4.2V Cell) 4.2V, V FB, Short Together, 3CELL Floats For battery voltages other than the preset values, an external resistor divider can be used. If an external divider is used then the 4.1V, 4.2V and 3CELL pins should not be connected and BAT2 pin should be grounded. To maintain the tight voltage tolerance, the external resistors should have better than 0.25% tolerance. Note that the V FB pin will float high and inhibit switching if it is left open. VC (Pin 18): This is the control signal of the inner loop of the current mode PWM. Switching starts at 0.9V, higher VC corresponds to higher charging current in normal operation and reaches 1.1V at full charging current. A capacitor of at least 0.33mF to GND filters out noise and controls the rate of soft start. Pulling this pin low will stop switching. Typical output current is 60mA. PROG (Pin 19): This pin is for programming the charge current and for system loop compensation. During normal operation, V PROG stays at 2.465V. If it is shorted to GND or more than 1mA is drawn out of the pin, switching will stop. When a microprocessor controlled DAC is used to pro- gram charging current, it must be capable of sinking current at a compliance up to 2.465V. PIN FUNCTIONSUU U BAT2 (Pin 20): This pin is used to connect the battery to the internal preset voltage setting resistor. An internal switch disconnects the internal divider from the battery when the device is in shutdown or when power is discon- nected. This disconnect function eliminates the current drain due to the resistor divider. This pin should be connected to the positive node of the battery if the internal preset divider is used. This pin should be grounded if an external divider is used. Maximum input voltage on this pin is 20V. SENSE (Pin 21): This pin is the noninverting input to the current amplifier CA1 in the Block Diagram. Typical bias current is – 50mA. SPIN (Pin 22): This pin is for the internal amplifier CA1 bias. It must be connected as shown in the application circuit. BAT (Pin 23): Current Amplifier CA1 Inverting Input. Typical bias current is – 50mA. V CC (Pin 24): Input Supply. For good bypass, a low ESR capacitor of 10 mF or higher is required. Keep the lead length to a minimum. VCC should be between 11V and 24V. Do not force V CC below VBAT by more than 1V with the battery present. BOOSTC (Pin 25): This pin is used to bootstrap and supply the current sense amplifier CA1 for very low dropout condition. V CC can be as low as only 0.4V above the battery voltage. A diode and a capacitor are needed to get the voltage from VBOOST. If low dropout is not needed and VCC is always 3V or higher than V BAT, this pin can be left floating or tied to VCC. Do not force this pin to a voltage lower than VCC. Typical input current is 1mA. GBIAS (Pin 26): This is the output of the internal 9.1V regulator to power the drivers and control circuits. This pin must be bypassed to a ground plane with a minimum of 2.2mF ceramic capacitor. Switching will stop when V GBIAS drops below 7V. BGATE (Pin 27): Low Side Power MOSFET Drive. PGND (Pin 28): MOSFET Driver Power Ground. A solid system ground plane is very important. See the LT1505 Demo Manual for further information.

4.7mF 10mH RS1 VRS1 TGATE VCC 3 SW

1 BOOST

2.5V BGATE 9.1V 12.6V BATTERY + + SW A12 0.02V PWM SLOPE COMP Q1 CA1 +– + – A11 IPROG VRS1 1.3V 50k

26 GBIAS

27 BGATE

28 PGND

22 SPIN

21 SENSE

23 BAT

20 BAT2

14 4.1V 50.55k 21k 15 4.2V 0.33k 12.3k RPROGCPROG VREF 2.465V VIN VCC 75k

25 BOOSTC

CL1* *LT1505 ONLY. SEE PIN FUNCTIONS FOR LT1505-1 CONNECTIONS COMP1 1505 BDPROGVC CLP 92mV 111918 CLN SYSTEM LOADAGND VA OSC 200k ONE SHOTSYNC 4 FLAG 13 SHDN GBIAS BAT 3.3V IPROG SHUTDOWN VCC VIN UV VCC 6.7V 6.7V 0.2V A13 Q4 7.8V VCC INFET VCCVIN CAP 12 RS IVA (LT1505)

4.93k IPROGIPROG SENSE BAT PROG LT1505

1505 TC03

0.047mF 0.47mF 0.033mF 3.3V 2.465V LT1013 FLAG VBAT VRS1 2V 1k VFB CAP 20k RS2 200W 10W LT1013 IVA Test Circuit 1 Test Circuit 3 Test Circuit 2 VREF 2.465V VA 2k 2nF VFB OR BAT2

1505 TC02

0.47mF VREF » 0.65V VBAT VC CA2 CA1 300W 20k RS1 10ΩBAT SENSE SPIN

1505 TC01

0.047mF LT1505 1mF 75k LT1006 RS2 200Ω RS3 200Ω

The LT1505 is a synchronous current mode PWM step- down (buck) switcher. The battery DC charge current is pro- grammed by a resistor R PROG (or a DAC output current) at the PROG pin and the ratio of sense resistors RS2 over RS1 (see Block Diagram). Amplifier CA1 converts the charge cur- rent through RS1 to a much lower current IPROG (IPROG = IBAT • RS1/RS2) fed into the PROG pin. Amplifier CA2 com- pares the output of CA1 with the programmed current and drives the PWM loop to force them to be equal. High DC accuracy is achieved with averaging capacitor C PROG. Note that IPROG has both AC and DC components. IPROG goes through R1 and generates a ramp signal that is fed to the PWM control comparator C1 through buffer B1 and level shift resistors R2 and R3, forming the current mode inner loop. The BOOST pin supplies the topside power switch gate drive. The LT1505 generates an 9.1V V GBIAS to power drives and VBOOSTC. BOOSTC pin supplies the current amplifier CA1 with a voltage higher than VCC for low dropout appli- cation. For batteries like lithium that require both constant- current and constant-voltage charging, the 0.5% 2.465V reference and the amplifier VA reduce the charge current when battery voltage reaches the preset level. For NiMH and NiCd, VA can be used for overvoltage protection. The amplifier CL1 monitors and limits the input current, normally from the AC adapter, to a preset level (92mV/R S). At input current limit, CL1 will supply the programming current IPROG, thus reducing battery charging current. To prevent current shoot-through between topside and lowside switches, comparators A3 and A4 assure that one switch turns off before the other is allowed to turn on. Comparator A12 monitors charge current level and turns lowside switch off if it drops below 20% of the programmed value (20mV across R S1) to allow for inductor discontinu- ous mode operation. Therefore sometimes even in con- tinuous mode operation with light current level the lowside switch stays off. Comparator E6 monitors the charge current and signals through the FLAG pin when the charger is in voltage mode and the charge current level is reduced to 20%. This charge complete signal can be used to start a timer for charge termination. The INFET pin drives an external P-channel FET for low dropout application. When input voltage is removed, V CC will be held up by the body diode of the topside MOSFET. The LT1505 goes into a low current, 10 mA typical, sleep mode as V CC drops below the battery voltage. To shut down the charger simply pull the V C pin or SHDN pin low with a transistor. OPERATIONU APPLICATIONS INFORMATIONWU UU Input and Output Capacitors In the 4A Lithium Battery Charger (Figure 1), the input capacitor (CIN) is assumed to absorb all input switching ripple current in the converter, so it must have adequate ripple current rating. Worst-case RMS ripple current will be equal to one half of output charging current. Actual capacitance value is not critical. Solid tantalum capacitors such as the AVX TPS and Sprague 593D series have high ripple current rating in a relatively small surface mount package, but caution must be used when tantalum capaci- tors are used for input bypass. High input surge currents can be created when the adapter is hot-plugged to the charger and solid tantalum capacitors have a known failure mechanism when subjected to very high turn-on surge currents. Highest possible voltage rating on the capacitor will minimize problems. Consult the manufac- turer before use. Alternatives include new high capacity ceramic (at least 20mF) from Tokin or United Chemi-Con/ Marcon, et al. The output capacitor (C OUT) is also assumed to absorb output switching current ripple. The general formula for capacitor current is: IRMS = (L1)(f) VBAT VCC()0.29 (VBAT) 1 – For example, V CC = 19V, V BAT = 12.6V, L1 = 15 mH, and f = 200kHz, IRMS = 0.4A.

ripple current will flow in the battery. minimum adapter voltage where full power can be achieved. Figure 2. Adapter Current Limiting

1505 F02

possible rate of which the adapter is capable.

and both CLP and CLN pins should be connected to VCC. where RPROG is the total resistance from PROG pin to ground. to filter out the noise (see Figure 4).

1505 F03

Figure 3. PWM Current Programming Figure 4. Reducing Current Sensing Noise

1505 F04

near zero over time as the battery reaches full charge.

is 3nA and the error can be neglected.

0.25 IVA and the open-collector output VFLAG will go low

on and there is no initial VBOOST. VBOOST up for a sufficient amount of time. Figure 5. External Resistor Divider

and 200mA when Q1 is off (Figure 8). Figure 6. High Input Voltage Shudown Figure 7. Synchronizing with External Clock

1505 F07

1505 F06

Figure 8. 2-Level Charging

1505 F05

replaced with a diode if VIN is at least 3V higher than VBAT. VIN is removed, INFET will clamp M3 VSG to 0.2V. go into sleep mode drawing only 10mA from the battery. VC pin low will only stop switching and VGBIAS stays high. at SHDN pin to VIN for pull-up. pulse width. Sync pulse threshold is about 1.2V (Figure 7).

system can be potentially crowbarred. Figure 10. VBAT Crowbar Protection

1505 F09

1505 F08

Figure 9. VIN Crowbar Protection decrease is detected as an indication of near full charge. stant trickle charge may not be recommended. about charge termination circuits. will shut down switching and protect the charger. Information furnished by Linear Technology Corporation is believed to be accurate and reliable. tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. interplane coupling and to act as a thermal spreading path. DC219 should be used for layout reference.

28-Lead Plastic SSOP (5.3mm) (Reference LTC DWG # 05-08-1640) LT/TP 1101 1.5K REV C • PRINTED IN USA Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 l FAX: (408) 434-0507 l www.linear.com PACKAGE DESCRIPTIONU PART NUMBER DESCRIPTION COMMENTS LT1372/LT1377 1.5A, 500kHz/1MHz Step-Up Switching Regulators High Frequency, Small Inductor, High Efficiency Switchers, SO-8 LT1376 1.5A, 500kHz Step-Down Switching Regulator High Frequency, Small Inductor, High Efficiency Switcher, SO-8 LT1510 Constant-Voltage/Constant-Current Battery Charger Up to 1.5A Charge Current, Small SO-8 Footprint LT1511 3A Constant-Voltage/Constant-Current Battery Charger Charges Lithium, NiCd and NiMH Batteries, 28-Lead SO Package LT1512 SEPIC CC/CV Battery Charger V IN Can Be Higher or Lower Than Battery Voltage, 2A Internal Switch LT1513 SEPIC CC/CV Battery Charger V IN Can Be Higher or Lower Than Battery Voltage, 3A Internal Switch LT1571 Constant-Voltage/Constant-Current Battery Charger 1.5A Charge Current, Preset Voltage for 1 or 2 Li-Ion Cells, C/10 Flag LTC1731 Linear Charger Controller Programmable Timer; 8-Pin MSOP; C/10 Flag LTC1732 Linear Charger Controller AC Adapter Present Flag; Programmable Timer; 10-Pin MSOP; C/10 Flag LTC1733 Linear Charger with Integrated FET 1.5A Charge Current, Programmable Timer, 10-Pin Thermally Enhanced MSOP Package LTC1734 Linear Charger Controller Inexpensive Constant-Voltage/Constant-Current Li-Ion Charger, 5-Pin SOT-23 Package LTC1759 SMBus Controlled Smart Battery Charger LT1505 Charger Functionality with SMBus Control LT1769 2A Constant-Voltage/Constant-Current Battery Charger Charges Lithium, NiCd and NiMH Batteries, 20-Lead Exposed Pad TSSOP LTC1960 Dual Battery Charger and Selector with SPI Interface I CHARGE up to 6A, Fast Charge, Longer Battery Life, Crisis Management RELATED PARTS ª LINEAR TECHNOLOGY CORPORATION 1 999 G28 SSOP 0501 .13 – .22 (.005 – .009) 0° – 8° .55 – .95 (.022 – .037) 5.20 – 5.38** (.205 – .212) 7.65 – 7.90 (.301 – .311) 1234 5 6 7 8 9 10 11 12 14 13 10.07 – 10.33* (.397 – .407) 2526 22 21 20 19 18 17 16 1523242728 1.73 – 1.99 (.068 – .078) .05 – .21 (.002 – .008) .65 (.0256) BSC .25 – .38 (.010 – .015) MILLIMETERS (INCHES) DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .152mm (.006") PER SIDE DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE