lt1505 Linear Technology Corporation, lt1505 Datasheet
lt1505
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lt1505 Summary of contents
Page 1
... This allows simultaneous opera- tion of the equipment and fast battery charging without over- loading the AC adapter. The LT1505 can charge batteries ranging from 2.5V to 20V with dropout voltage as low as 0.5V. Synchronous N-channel FETs switching at 200kHz give high efficiency and allow small inductor size. A diode is not required in ...
Page 2
... SENSE BAT2 20 19 PROG 3CELL 16 15 4.2V G PACKAGE NOTE: LT1505CG-1 DOES NOT HAVE INPUT CURRENT = 125 C, = 100 LIMITING FUNCTION (LT1505), no load on any CLN CC MIN TYP MAX 100 105 92 108 2.453 2.465 2.477 A 2 ...
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... SYNC SYNC Measured at (V – BOOST SW Low to High Hysteresis < 0.45V Low (Shutdown) SHDN LT1505 = V (LT1505), no load on any CLN CC MIN TYP MAX 0.5 – – 6.3 6.7 7.25 – – 1 – 4 – 22 – 1 – ...
Page 4
... 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 200kHz to charge up C2. Comparator A2 senses V ...
Page 5
... TEMPERATURE ( C) V Pin Characteristics C –1.2 –1.0 –0.8 –0.6 –0.4 –0.2 0 0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 V (V) C LT1505 V Line Regulation REF 0.003 125 C J 0.002 0.001 ALL TEMPERATURES 0 –0.001 –0.002 –0.003 (V) CC 1505 G02 ...
Page 6
... The gate is off (high) when V UV The body diode of the PFET is used to pull 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 with 200kHz switching noise ...
Page 7
... VA controls the charging current to maintain the voltage on the V pin at the reference voltage (2.465V). Input bias FB 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 pin ...
Page 8
... PROG R S2 BAT – 23 BAT2 + 20 A11 – R4 50.55k 3CELL 16 R5 21k REF – 14 4.1V 2.465V R6 0.33k 4. 12.3k IN 92mV + CLP + CLN – SYSTEM 1505 BD LOAD *LT1505 ONLY. SEE PIN FUNCTIONS FOR LT1505-1 CONNECTIONS VR S1 – 12.6V BATTERY 1505fc ...
Page 9
... I PROG 2k – LT1013 + + 0. PROG 2.465V Test Circuit 3 LT1505 – PROG PROG + + 3. PROG 10k 0.47 F 4.93k 2.465V LT1505 SPIN R S3 200 SENSE + 200 BAT – BAT 1505 TC01 V OR BAT2 FB 2nF 1505 TC02 R S3 200 SENSE + + ...
Page 10
... The INFET pin drives an external P-channel FET for low dropout application. When input voltage is removed, V body diode of the topside MOSFET. The LT1505 goes into a low current typical, sleep mode as V below the battery voltage. To shut down the charger simply pull the V ) ...
Page 11
... If the ESR 0.2 and the battery impedance OUT is raised to 4 with a bead or inductor, only 5% of the ripple current will flow in the battery. Soft Start and Undervoltage Lockout The LT1505 is soft started by the 0.33 F capacitor on the V pin. On start-up, the V pin voltage will rise quickly ...
Page 12
... A12 and turn on BGATE at the wrong time, potentially damaging the bottom power FET. In this case filter of 10 and 10nF should be used across RS1 to filter out the noise (see Figure 4). power S1 LT1505 ) Lithium-Ion Charging C The 4A Lithium Battery Charger (Figure 1) charges lithium- PROG ...
Page 13
... C and 1% over the full temperature range. This leads to the possibility that very accurate (0.1%) resistors might be needed for R3 and R4. Actually, the temperature of the LT1505 will rarely exceed float mode because charging currents have tapered off to a low level, so 0.25% resistors will normally provide the required level of overall accuracy ...
Page 14
... Each TGATE and BGATE pin has a 50k pull-down resistor to keep the external power FETs off when shut down or power is off. Note that maximum operating V transients the LT1505 can be operated as high as 27V. For V higher than 24V it is preferred to use the V CC down. If the SHDN pin has to be used to shut down at V ...
Page 15
... P-channel FET M3 (see Figure 9), otherwise, high reverse surge current might damage M3. M3 can also be replaced by a diode if dropout voltage and heat dissipation are not problems. Note that the LT1505 will operate even when V grounded Figure 1 charger gets shorted to BAT ground very quickly (crowbarred) from a high battery voltage, slow loop response may allow charge current to build up and damage the topside N-channel FET M1 ...
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... Charge Current, Programmable Timer, 10-Pin Thermally Enhanced MSOP Package Inexpensive Constant-Voltage/Constant-Current Li-Ion Charger, 5-Pin SOT-23 Package LT1505 Charger Functionality with SMBus Control Charges Lithium, NiCd and NiMH Batteries, 20-Lead Exposed Pad TSSOP 6A, Fast Charge, Longer Battery Life, Crisis Management CHARGE www ...