LT8609AIMSE#TRPBF

Due to market price fluctuations,if you need to purchase or consult the price.You can contact us or emial to us:   sales@allicdata.com

1. DESCRIPTION

The LT8609AIMSE#TRPBF is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 1.7µA of nonswitching quiescent current. The LT8609/LT8609A/LT8609B can deliver 3A of continuous current. Burst Mode operation enables high efficiency down to very low output currents while keeping the output ripple below 10mVP-P. A SYNC pin allows synchronization to an external clock, or spread spectrum modulation for low EMI operation. Internal compensation with peak current mode topology allows the use of small inductors and results in fast transient response and good loop stability. The EN/UV pin has an accurate 1V threshold and can be used to program VIN UVLO or to shut down the part. A capacitor on the TR/SS pin programs the output voltage ramp rate during start-up while the PG flag signals when VOUT is within ±8.5% on the adjustable output parts or ±7.5% on the fixed output parts of the programmed output voltage as well as fault conditions. The LT8609A has slower switch edges for lower EMI emissions. The LT8609B operates in pulse-skipping mode only.

2. FEATURES 

    1. Wide Input Voltage Range: 3.0V to 42V

    2. Ultralow Quiescent Current Burst Mode® Operation:

        - <2.5µA IQ Regulating 12VIN to 3.3VOUT

        - Output Ripple <10mVP-P

    3. High Efficiency 2MHz Synchronous Operation:

        - >93% Efficiency at 1A, 5VOUT from 12VIN

    4. 3A Maximum Continuous Output

    5. Fast Minimum Switch-On Time: 45ns

    6. LT8609A Available in Fixed 3.3V and 5V Output

    8. Adjustable and Synchronizable: 200kHz to 2.2MHz

    9. Spread Spectrum Frequency Modulation for Low EMI

  10. Allows Use of Small Inductors

  11. Low Dropout

  12. Peak Current Mode Operation

  13. Accurate 1V Enable Pin Threshold

  14. Internal Compensation

  15. Output Soft-Start and Tracking

  16. Small 10-Lead MSOP Package, 16-Lead MSOP Package, or 10-Lead 3mm × 3mm DFN Package with Side Wettable Flanks

  17. AEC-Q100 Qualified for Automotive Applications

3. APPLICATIONS

    1. GSM Transceivers

    2. General Purpose Step-Down

    3. Low EMI Step-Down

4. PIN FUNCTIONS

    1. BST: This pin is used to provide a drive voltage, higher than the input voltage, to the topside power switch. Place a 0.1µF boost capacitor as close as possible to the IC. Do not place a resistor in series with this pin.

    2. SW: The SW pin is the output of the internal power switches. Connect this pin to the inductor and boost capacitor. This node should be kept small on the PCB for good performance.

    3. INTVCC: Internal 3.5V Regulator Bypass Pin. The internal power drivers and control circuits are powered from this voltage. INTVCC max output current is 20mA. Voltage on INTVCC will vary between 2.8V and 3.5V. Decouple this pin to power ground with at least a 1μF low ESR ceramic capacitor. Do not load the INTVCC pin with external circuitry.

    4. RT: A resistor is tied between RT and ground to set the switching frequency.

    5. SYNC: External Clock Synchronization Input. Ground this pin for low ripple Burst Mode operation at low output loads. Tie to a clock source for synchronization to an external frequency. Leave floating for pulse-skipping mode with no spread spectrum modulation. Tie to INTVCC or tie to a voltage between 3.2V and 5.0V for pulse-skipping mode with spread spectrum modulation. When in pulse-skipping mode, the IQ will increase to several mA. In the LT8609B, the SYNC pin is replaced with a no connect; the LT8609B operates in pulse-skipping mode without spread spectrum.

    6. FB (LT8609/LT8609A/LT8609B ONLY): The LT8609/LT8609A/LT8609B adjustable output parts regulate the FB pin to 0.782V. Connect the feedback resistor divider tap to this pin.

    7. VOUT (LT8609A-3.3/LT8609-5 ONLY): The LT 8609A-3.3 regulates to VOUT pin to 3.3V. This pin connects a 5.9MΩ internal feedback divider that programs the fixed output. The LT8609A-5 regulates to VOUT pin to 5V. This pin connects a 8.95MΩ internal feedback divider that programs the fixed output.

    8. TR/SS: Output Tracking and Soft-Start Pin. This pin allows user control of output voltage ramp rate during start-up. A TR/SS voltage below 0.782V forces the LT8609/LT8609A/LT8609B to regulate the FB pin to equal the TR/SS pin voltage. In the LT8609A-3.3 and LT8609A-5 fixed output voltage options the output voltage will track the TR/SS pin voltage based on a factor set by the internal feedback resistor divider. The 3.3V output options will track to a voltage 4.2 times that of the TR/SS pin, while the 5V output options will track to a voltage 6.39 times that of the TR/SS pin. When TR/SS is above 0.782V, the tracking function is disabled and the internal reference resumes control of the error amplifier. An internal 2μA pull-up current from INTVCC on this pin allows a capacitor to program output voltage slew rate. This pin is pulled to ground with a 300Ω MOSFET during shutdown and fault conditions; use a series resistor if driving from a low impedance output.

    9. PG: The PG pin is the open-drain output of an internal comparator. On the LT8609/LT8609A/LT8609B adjustable output parts, PG remains low until the FB pin is within ±8.5% of the final regulation voltage, and there are no fault conditions. On the LT8609A-3.3/LT8609A-5 fixed output parts, PG remains low until the VOUT pin is within ±7.5% of the final regulation voltage, and there are no fault conditions. PG is valid when VIN is above 3.2V, regardless of EN/UV pin state.

  10. VIN: The VIN pin supplies current to the LT8609/LT8609A/LT8609B internal circuitry and to the internal topside power switch. This pin must be locally bypassed. Be sure to place the positive terminal of the input capacitor as close as possible to the VIN pins, and the negative capacitor terminal as close as possible to the GND pins.

  11. EN/UV: The LT8609/LT8609A/LT8609B is shut down when this pin is low and active when this pin is high. The hysteretic threshold voltage is 1.05V going up and 1.00V going down. Tie to VIN if the shutdown feature is not used. An external resistor divider from VIN can be used to program a VIN threshold below which the LT8609/LT8609A/LT8609B will shut down.

  12. GND: Exposed Pad Pin. The exposed pad must be connected to the negative terminal of the input capacitor and soldered to the PCB in order to lower the thermal resistance.

5. Application information

In order to improve the efficiency at light load, LT8609AIMSE#TRPBF Enter low-ripple burst mode operation, keep The output capacitor is charged to the required output voltage At the same time minimize the input quiescent current and minimize the output voltage ripple. In burst mode operation LT8609/LT8609A provides a single small current pulse To the output capacitor, and then the sleep period, where The output power is provided by the output capacitor. although In sleep mode, the LT8609/LT8609A consumes 1.7μA. As the output load decreases, the frequency of a single current pulse decreases and the percentage The time that the LT8609/LT8609A is in sleep mode increases, This results in much higher light load efficiency than typical converters. By maximizing the time between pulses, Converter quiescent current is close to 2.5µA Typical application when there is no output load. so, Optimize quiescent current performance under light Load, the current in the feedback resistor divider must Minimized because it appears as load current in the output. In burst mode operation, the current limit The top switch is about 600mA. Increase output The capacitor will reduce the output ripple proportionally. As the load rises from zero, the switching frequency Will increase, but only to the switching frequency set by the resistor on the RT pin. LT8609/LT8609A Achieved output load The programming frequency changes according to the input voltage, Output voltage and inductance selection. For some applications, LT8609/ LT8609A works in pulse skipping mode, which is The only mode available for LT8609B. Pulse skipping mode Provides two main differences from burst mode operation. The first is that the clock always remains awake, and all switching cycles are aligned with the clock. In this mode more The internal circuit is always awake, increasing The quiescent current can reach hundreds of µA. Followed by Reach full switching frequency under lower output load Than in burst mode operation. arrive Enable pulse skip mode SYNC pin is left floating. arrive Spread spectrum modulation through pulse skipping In mode, the SYNC pin is pulled high. When applying the clock To the SYNC pin, the LT8609/LT8609A will also be Pulse skipping mode.