LTC1733EMSE FOR IC

The LTC1733-EMSE is a member of the highly efficient, cost-effective and battery-friendly Linear Voltage Regulator™ (LVR) family. The LTC1733 has a fixed switching frequency of 360 kHz and is capable of reducing excess noise with enhanced digital filtering. The LTC1733-EMSE is designed for use in applications such as sensors, remote monitoring and control systems, battery management systems and other applications where low noise and small size are important. It offers excellent line regulation, as well as CV discharge termination. In addition, the device also has an integrated soft start function to reduce output voltage ramp up time which extends battery life. These features combined make the LTC1733-EMSE ideally suited for energy harvesting or solar applications.

Voltage Regulator Features

The LTC1733-EMSE is a fixed frequency, voltage mode, current limited, synchronous switching regulator with shutdown. It steps down an input voltage to a fixed output voltage (1.5 V, 2 V, 2.85 V, 3.3 V). The device has a short circuit current (Isc) of up to 50 A, and is capable of delivering a continuous load current up to 16 A while maintaining excellent line regulation. The regulator also has an excellent load regulation of less than 1%. The regulator has a typical efficiency of greater than 90%. A key feature of the LTC1733-EMSE is that it can be shutdown from the chip enable (EN) pin by pulling it below the shutdown threshold of 0.4 V.

Integrated Soft Start Function

The LTC1733-EMSE has an integrated soft start circuit that reduces output voltage ramp up time to less than 100 ms, which extends battery life by reducing the charge/discharge cycle. The integrated soft start circuit is controlled through a logic signal applied to the soft start enable (SS EN) pin. It charges a 10 nF capacitor inside the device through a 2 kΩ resistance until the voltage on the capacitor reaches 3.5 V. Once the voltage on the capacitor reaches 3.5 V, the soft start circuit is activated and the voltage on the SS pin goes low. The voltage on the capacitor is then discharged through a 10 kΩ resistance. The voltage on the SS pin goes high when the capacitor voltage reaches 2 V. The start capacitor discharge time is about 1.3 s. The soft start circuit is disabled when the SS EN pin is connected to GND.

Excellent Line Regulation

The LTC1733-EMSE has excellent line regulation. Perfect line regulation is achieved when the output voltage is constant at its set point even when the input voltage varies. It achieves this line regulation by sensing the input voltage and correcting the output voltage to compensate for changes in the input voltage. The table below shows the output voltage variation as a percentage of the set point voltage at various line voltages while maintaining an output current of 1 A.

Very Low Noise Operation – 106 dB

The LTC1733-EMSE has an integrated low noise oscillator (LNO) and an R-C network that generates a constant switching frequency of 360 kHz. This low noise operation results in an output ripple voltage of less than 1% of the output voltage with a CV discharge termination load. The LNO has two operating modes—a high noise mode and a low noise mode. The noise mode is selected by connecting resistor R1 between pins 6 and 7, as shown in the figure below. The high noise mode is selected when R1 is open. The low noise mode is selected when R1 is connected. The typical gain of the R-C network is 106 dB at low noise mode.

Battery Discharge Termination (BDT) with Auto Re-start

The LTC1733-EMSE has a battery discharge termination (BDT) function which terminates the CV discharge when the voltage across the battery is below the BDT set point. This is controlled by a 12-bit DAC inside the device. The BDT (OFF) set point is programmed by connecting the VREF pin to GND or to VOUT. The VOUT pin is internally connected to the VREF pin. This means that when VOUT is set to a given voltage (i.e., 2 V, 2.85 V, 3.3 V or 5 V), the VREF pin is also set to the same voltage. When VREF is connected to GND, the VOUT pin is internally set to VREF/2, and when VREF is connected to VOUT, the VOUT pin is internally set to VREF/2.

Good Robustness for Shocks and Drops, as well as Humidity

The LTC1733-EMSE has a small footprint and is available in a 10-pin, 3 x 3 mm, DFN package. It can withstand a minimum of 40 G of acceleration (i.e., 40 g shock and vibration) and is rated to withstand an operating temperature range of -40 °C to +125 °C. In addition, the device has built-in protection to withstand humidity and electrostatic discharges (ESD). The device is rated to withstand a Human Body Model (HBM) ESD rating of > 16 kV.

Conclusion

The LTC1733-EMSE is a member of the highly efficient, cost-effective and battery-friendly Linear Voltage Regulator™ (LVR) family. The LTC1733 has a fixed switching frequency of 360 kHz and is capable of reducing excess noise with enhanced digital filtering. The LTC1733-EMSE is designed for use in applications such as sensors, remote monitoring and control systems, battery management systems and other applications where low noise and small size are important. It offers excellent line regulation, as well as CV discharge termination. In addition, the device also has an integrated soft start function to reduce output voltage ramp up time which extends battery life. These features combined make the LTC1733-EMSE ideally suited for energy harvesting or solar applications.