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LT1511 Datasheet(PDF) 8 Page - Linear Technology |
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LT1511 Datasheet(HTML) 8 Page - Linear Technology |
8 / 16 page 8 LT1511 TEST CIRCUITS Test Circuit 1 VREF ≈ 0.65V VBAT VC CA2 – + – + CA1 + 300 Ω 20k 1k 1k RS1 10 Ω BAT SENSE SPIN 1511 • TC01 PROG RPROG 0.047 µF LT1511 1 µF 60k LT1006 + RS2 200 Ω RS3 200 Ω VREF 2.465V – + VA + 10k 10k OVP 1511 • TC02 IPROG RPROG LT1511 PROG LT1013 0.47 µF OPERATION The LT1511 is a current mode PWM step-down (buck) switcher. The battery DC charging current is programmed by a resistor RPROG (or a DAC output current) at the PROG pin (see Block Diagram). Amplifier CA1 converts the charging current through RS1 to a much lower current IPROG fed into the PROG pin. Amplifier CA2 compares 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 CPROG. 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 drives the switch NPN QSW into saturation and reduces power loss. For batteries like lithium-ion that require both constant-current and constant-voltage charg- ing, the 0.5%, 2.465V reference and the amplifier VA reduce the charging current when battery voltage reaches the preset level. For NiMH and NiCd, VA can be used for overvoltage protection. When input voltage is not present, the charger goes into low current (3 µA typically) sleep mode as input drops down to 0.7V below battery voltage. To shut down the charger, simply pull the VC pin low with a transistor. Test Circuit 2 |
Similar Part No. - LT1511_15 |
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Similar Description - LT1511_15 |
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