LT1511 Linear Technology, LT1511 Datasheet
LT1511
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LT1511 Summary of contents
Page 1
... Charging current is reduced to keep the adapter current within specified levels. The LT1511 can charge batteries ranging from 1V to 20V. Ground sensing of current is not required and the battery’s negative terminal can be tied directly to ground. A saturat- ing switch running at 200kHz gives high charging effi- ciency and small inductor size ...
Page 2
... UVOUT V 20V, V 0.4V BAT INFORMATION TOP VIEW ORDER PART NUMBER 24 GND** 23 GND** LT1511CSW CC1 LT1511ISW CC2 *ALL V PINS SHOULD CC3 BE CONNECTED 19 PROG TOGETHER CLOSE TO THE PINS ALL GND PINS ARE FUSED TO INTERNAL DIE 17 UV OUT ...
Page 3
... All Conditions > < (Note 4) J All Conditions > & < 0.45V C LT1511 (maximum operating 28V, MAX CC MIN TYP MAX 0 0.15 0. 100 4 200 2.4 V – ...
Page 4
... LT1511 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are load on any outputs unless otherwise noted. PARAMETER Voltage Amplifier VA Transconductance (Note 3) Output Source Current OVP Input Bias Current Current Limit Amplifier CL1, 8V Input Common Mode Turn-On Threshold Transconductance CLP Input Current CLN Input Current Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired ...
Page 5
... V (V) C 1511 • TPC08 Reference Voltage vs Temperature 2.470 2.468 2.466 2.464 2.462 2.460 2.458 1.8 2 TEMPERATURE 1511 • TPC11 LT1511 1511 • TPC06 1.4 1.6 1.8 2.0 1511 • TPC09 100 125 150 LT1511 • TPC12 5 ...
Page 6
... LT1511 PIN FUNCTIONS GND (Pins 16, 23, 24): Ground Pin. SW (Pin 2): Switch Output. The Schottky catch diode must be placed with very short lead length in close proximity to SW pin and GND. BOOST (Pin 3): This pin is used to bootstrap and drive the switch power NPN transistor to a low on-voltage for low power dissipation ...
Page 7
... GND – 75k 200kHz OSCILLATOR SHUTDOWN SLOPE COMPENSATION – – CA2 + V REF PROG I PROG C PROG R PROG LT1511 UV OUT V CC BOOST SPIN R S3 SENSE + CA1 R S2 BAT – I PROG + 0VP VA V REF – 2.465V g = 0.64 m 100mV ...
Page 8
... 0.65V U OPERATION The LT1511 is a current mode PWM step-down (buck) switcher. The battery DC charging current is programmed by a resistor R (or a DAC output current) at the PROG PROG pin (see Block Diagram). Amplifier CA1 converts the charging current through much lower current ...
Page 9
... W U Soft-Start The LT1511 is soft started by the 0.33 F capacitor on the V pin. On start-up then ramp at a rate set by the internal 45 A pull-up current and the external capacitor. Battery charging current starts ...
Page 10
... S4 ADAPTER CURRENT LIMIT Figure 2. Adapter Current Limiting Adapter Limiting An important feature of the LT1511 is the ability to automatically adjust charging current to a level which avoids overloading the wall adapter. This allows the product to operate at the same time that batteries are ...
Page 11
... R3 2.465 390k Li-Ion batteries typically require float voltage accuracy 2%. Accuracy of the LT1511 OVP voltage is 0. and 1% over full temperature. This leads to the possibility that very accurate (0.1%) resistors might be needed for R3 and R4. Actually, the temperature of the LT1511 will rarely exceed float mode because charging currents have tapered off to a low level ...
Page 12
... PROG pin. 1511 • F05 Thermal Calculations If the LT1511 is used for charging currents above 1.5A, a thermal calculation should be done to ensure that junction ) should temperature will not exceed 125 C. Power dissipation in ...
Page 13
... SW 15 0.81 0.09 0.9W Total Power in the IC is: 0.27 + 0.33 + 0.9 = 1.5W Temperature rise will be (1.5W)(30 C/ This assumes that the LT1511 is properly heat sunk by con- necting the seven fused ground pins to expanded traces and that the PC board has a backside or internal plane for heat spreading. The P term can be reduced by connecting the boost ...
Page 14
... restricting boost voltage to 5V instead of using V is normally done. This lower boost voltage also reduces power dissipation in the LT1511 win-win deci- sion. Connect an external source Figure 10 with Even Lower Dropout For even lower dropout and/or reducing heat on the board, the input diode D3 should be replaced with a FET (see Figure 11) ...
Page 15
... The other paths contain only DC and/or POWER 200kHz tri-wave and are less critical. Figure 13 indicates the high speed, high current switching path. Figure 14 shows critical path layout. Contact Linear Technology for 1511 F12a an actual LT1511 circuit PCB layout or Gerber file. ADAPTER ...
Page 16
... Up to 1.5A Charge Current for Lithium-Ion, NiCd and NiMH Batteries V Can Be Higher or Lower Than Battery Voltage Charge Current for Lithium-Ion, NiCd and NiMH Batteries GND OUT LT1511 • F14 0.598 – 0.614* (15.190 – 15.600 ...