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LTC1516 Datasheet(PDF) 4 Page - Linear Technology |
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LTC1516 Datasheet(HTML) 4 Page - Linear Technology |
4 / 8 page 4 LTC1516 BLOCK DIAGRAM COMP1 COMP2 COMP3 VREF CLOCK 1 CLOCK 2 CONTROL LOGIC VOS S3 S2A S2B S2C S1A S1B S1C S1D 0.22 µF 10 µF 0.22 µF C1+ C1– C2+ C2– 10 µF VOUT SHDN LTC1516 • BD CHARGE PUMP SHOWN IN TRIPLER MODE, DISCHARGE CYCLE VIN CHARGE PUMP + + APPLICATIONS INFORMATION Operation The LTC1516 uses a switched capacitor charge pump to boost VIN from 2V to 5V to a regulated 5V ±4% output voltage. Regulation is achieved by sensing the output voltage through an internal resistor divider and enabling the charge pump when the output voltage droops below the lower trip point of COMP2. When the charge pump is enabled, a 2-phase, nonoverlapping clock controls the charge pump switches. Clock 1 closes the S1 switches which enable the flying capacitors, C1 and C2, to charge up to the VIN voltage. Clock 2 closes the S2 switches which stack C1 and C2 in series with VIN and connect the top plate of C2 to the output capacitor at VOUT. This sequence of charging and discharging continues at a free-running frequency of 600kHz (typ) until the output has risen to the upper trip point of COMP2 and the charge pump is disabled. When the charge pump is disabled, the LTC1516 draws only 8 µA (typ) from VIN which provides high efficiency at low load conditions. To achieve the highest efficiency over the entire VIN range, the LTC1516 operates as either a doubler or a tripler depending on VIN and output load conditions. COMP1 and COMP2 determine whether the charge pump is in doubler mode or tripler mode. COMP1 forces the part into tripler mode if VIN is <2.55V, regardless of output load. When VIN is > 2.55V, the part will be in doubler mode using only C2 as a flying capacitor. In doubler mode, if the output droops by 50mV under heavy loads, COMP3 will force the charge pump into tripler mode until VOUT climbs above the upper trip point of COMP3. Under these VIN and load conditions, the nominal VOUT will be approximately 50mV lower than the no load nominal VOUT. This method of sensing VIN and output load results in efficiency greater than 80% with VIN between 2.5V and 3V. In shutdown mode, all circuitry is turned off and the part draws only leakage current (< 1 µA) from the VIN supply. VOUT is also disconnected from VIN. The SHDN pin is a CMOS input with a threshold of approximately VIN/2; however, the SHDN pin can be driven by logic levels that exceed the VIN voltage. The part enters shutdown mode when a logic high is applied to the SHDN pin. The SHDN pin cannot float; it must be driven with a logic high or low. |
Similar Part No. - LTC1516_15 |
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Similar Description - LTC1516_15 |
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