Synchronous Buck Converter Circuit

This is a design for synchronous buck converters. A synchronous buck converter consists of a high side and a low-side MOSFET, which is placed in place of the conventional buck converter catch diode to provide a lower loss path for the load current. Shoot-through leads to current spikes at the switching instants and manifests itself as a decrease in the efficiency of the converter. A current probe cannot be used to measure it because the inductance of the probe significantly affects the circuit operation. An alternative way to detect shoot through is by looking for spikes on the gate source voltages of the two FETs. (The gate-source voltage of the top MOSFET can be monitored differentially). This is the figure of the circuit;


One approach is to employ a controller IC with a “fixed dead-time,” which ensures that there is a delay after the top MOSFET is turned-off before the lower MOSFET is turned on. This approach is simple, but has to be implemented carefully. If the dead time is too short, shoot-through may not be averted. If it is too long, the conduction losses increase because during the dead time the body diode of the bottom FET is on. Because of the conduction of this body diode during the dead-time, the efficiency of the system when using this technique depends somewhat on the bottom MOSFET’s body diode characteristics.

[Schematic circuit source: MAXIM Application Notes]

Multiple Output DC-DC Converters and Doubles as High-Voltage DC-DC Controllers

This is a design circuit for converter that is ideal for use as a secondary-side post regulator in the design of multiple output AC-DC or DC-DC power supplies or as a DC-DC controller for use in point-of-load (POL) regulators. This circuit is work with based on LM5115. This is the figure of the circuit;


This IC in the circuit has features provide multiple outputs from main DC-DC or AC-DC converter. This IC has operates directly from secondary-side phase signal or DC input. The LM5115 is leading-edge modulation for SSPR from current-mode primary controller. This IC has integrated gate drivers with 2.5A peak output current. Up to 1 MHz switching frequency reduces component footprint and profile. [Circuit source: MAXIM Application Notes]

Integrates Start-Up Regulator and Precision Reference Using LM5033

This is a design device that is ideal for use in telecommunication bricks, industrial power converters, and automotive systems. This is a start up regulator and precision circuit. This circuit is work based on LM5033. This is the figure of the circuit;


In this circuit has features like isolated step-down converter stage feeds multiple non-isolated point-of-load (POL) converters. Each output is independently regulated. No feedback opto-coupler required. Integrated 15V to 100V start-up regulator. Low primary component count. Integrated 1.5A drivers. Tiny, thermally enhanced LLP packaging.

[Circuit source: MAXIM Application Notes]

Boost Converter Circuit for Digital Camera Motor Using LM2623

This is a design circuit for converter that using for a very practical LM2623A ratio adaptive circuit to drive a digital camera motor. It produces 5 volts from input voltages ranging between 1.8 and 4.5 volts. This is the figure of the circuit;


The duty cycle is not shown, but it varies from about 86% at 1.8 volts in to 71% at 4.5 volts in. Maintaining the 86% duty cycle at 4.5 volts would reduce the efficiency and increase the ripple. Maintaining the 70% duty cycle at 1.8 volts would significantly reduce the output capability. Several camera manufacturers are already requiring 1.8 to 4.5 volt operation from all the power supplies. The 1.8 to 4.5 voltage standard allows a manufacturer to build his product and let the user select disposable Alkalines, Ni-MH or Li-Ion at the point of purchase.

[Schematic circuit source: National Semiconductor Notes]

Auto Retry for MAX1637 Step-Down Controller Circuit

On telecom applications, the MAX1637 is a popular device. This device offer a lot of advantages such as PWM operation, small size, high MOSFET-drive capability, wide VIN and VOUT ranges, and excellent protection against over- and under-voltage faults. An auto-retry controller that attempts to restart the system is often needed in telecom application. This is the figure of the circuit;


When a short circuit is present and the controller cannot regulate the supply voltage, the Vout falls. IC2 latches and turns both device off if the voltage remains below 70% of it’s normal value for 6144 clock cycles. You must either turn off the power supply or toggle the active-low SHDN signal to restart IC2. An internal power-fail comparator and manual-reset circuitry (MR) is included on microprocessor supervisor (IC1). When Vout (1.8V) is above the internal reference voltage (1.25V) will be detected by IC1’s PFI input. The active-low PFO output produces a pulse using the internal 60k pull-up resistor and external 0.1 uF capacitor if Vout falls below 1.25V (due to a short circuit, for instance). The pulse will makes active-low MR low, causing active-low RST to assert and pull active-low SHDN low. Active-low RESET and active-low SHDN go high after a timeout delay of 140ms, re-enabling IC2. The other way to re-enabling IC2 is when the supply voltage is first switched on : the 3.5V rail stabilizes after 140ms will cause active-low RST to go high and activate IC2.

[Schematic circuit source: MAXIM Application Note]

Low Pass Filter Circuit with Enhanced Step Response

Effect on the system’s time-domain response is a common problem when designing low-pass filters. The system may fail to recognize significant changes in time because pushing the cut-off frequency lower slows the step response. For solving the problem, this is the figure of the circuit.


On this circuit diagram, lower cut-off frequency is allowed without sacrificing the step-response time. The delta (difference) between the filter’s input and output is monitored by window comparator. The filter increases its slew rate by increasing its cut-off frequency an order of magnitude when the delta exceeds 50mV. Low-pass-filtered by R4 and C3 is the original signal which is producing a cut-off frequency (312Hz) that reduces sensitivity to momentary glitches. The window-comparator input is drove by the filtered input. Comparator U2A or U2B will assert its output low if the input is outside the 50mV window. The low output drives Q5 into cutoff, causing its collector to presume a high impedance.

The filter’s cutoff frequency increases by ten times because the Q5 collector no longer grounds capacitor C2. The cutoff frequency throttles back to its quiescent state. When the system output changes to within 50mV of the system input. This circuit diagram is configured for very low cutoff frequency, but changing C1 and C2 can rescale the configuration to higher frequency, where the oscillation frequency fOSC (in kHz) is 30 x 103/COSC (in pF) and the cutoff frequency is fOSC/100. For different window values in which the delta equals the resistance multiplied by 115µA, we can modify R2 and R3. The type of comparator must be an open-drain type.

[Source: maxim-ic.com]

Li-Ion Driver for 6 White LEDs with External PWM Dimming

The TPS61160/1 is a boost converter that drives up to 10 LEDs in series with a 40-V rated integrated switch FET. To reduce output ripple, improve convertion efficiency, and allows for the use of small external component, the boost converter is very usefull. The default white LED current is set with the external sensor resistor Rset, and the feedback voltage is regulated to 200mV. We can controll LED current during the operation using 1-wire digital interface through the CTRL pin or with pulse width modulation (PWM) signal that applied to the CTRL pin through the duty cycle determines the feedback reference voltage. To prevent the output from exceeding the absolute maximum ratings during open LED condition, the device has a feature of integrated open LED protection that disable the TPS1160/1. This is the figure of the circuit.


This device has a lot of features such as has input range between 2.7V to 18V. TPS61160 is used for 26V Open LED Protection for 6 LEDs and TPS61161 is used for 38V Open LED Protection for 10 LEDs. Voltage reference is 200mV with 2% accuracy. It has flexible digital and PWM brightness control. This device built-in soft start and has efficiency up to 90% and the last is 2mmx2mmx0.8mm 6-pin QFN Packacge with Thermal Pad. Cellular Phones, Portable Media Players, Ultra Mobile Devices, GPS Receivers, White LED Backlighting for Media Form Factor Display are kinds of application where this device can be applied.

[Circuit schematic source: Texas Instruments Application Note]

Isolated Temperature Sensor Circuit

In some temperature-sensing applications there are some problems caused by the placement of sensors on location where the potential is very different from that of the data-acquisition-system common. So the operating temperature sensor must be isolated from its data-acquisition system galvanically. And the power’s source for the sensor was isolated. This circuit is designed to solve that problem. It provides power and isolation for a temperature sensor. This is the figure of the circuit.


This circuit is use the MAX845 (IC1) as a power transformer driver. The power of the temperature sensor is generated by the secondary winding from transformer that feeds a Graetz bridge rectifier. This circuit uses the MAX6576 (IC2) as temperature sensor that is provides a digital output whose period encodes the temperature (10µs/°K to 640µs/°K) and isolated by transformer. The MAX6576 was chosen because it combines the temperature sensor, signal-processing electronics, and easy-to-use digital I/O interface in a single low-cost package. It draws very little current from a single supply voltage. The MAX6576 is operated in the range +3V to +5V but it can maintain its accuracy specs.

[Circuit schematic source: maxim-ic.com]

Versatile Boost Converter with TPS6108x

This is design circuit for converter. There are two types of highly integrated boost converters, the TPS61081 and TPS61080. Both of them require low input voltage of 2.5V and the output is adjustable up to 27 V. The TPS61080’s current limit rating of the integrated power switches is 0.5 A and 1.3 A for TPS61081. This is the figure of the circuit;


It is useful for industrial application such as a 12- or 24-V industrial power rail from a 3.3- or 5-V bus. It also can be used to boost the 3.6-V Li-ion battery voltage used in most portable applications. Besides that, it can be used for higher voltages required applications such as OLED displays, powering thin film-transistor (TFT) LCDs, camera flashlights or WLED backlights.

For light-load efficiency, we can configure the switching frequency about 600kHz and 1.2 MHz for smaller external components . An extremely small boost converter is enabled by the 3 × 3-mm QFN package for a wide variety of applications because it has, fast PWM switching and internal power switches, and integrated feedback compensation. [Source: Texas Instruments Application Note]

Signal Conditioning Amplifier for Piezofilm Sensor

The signal can be converted by piezoelectric films in many ways such as thermal to electrical (temperature sensor), mechanical to electrical (microphone), and electrical to mechanical ( a loudspeaker). The circuit is signal conditioning amplifier for piezofilm sensor which use three op amps and has a high-input-impedance differential charge. This is the figure of the circuit;


This circuit use a voltage source with a capacitor in series as the electrical analog of a piezofilm sensor. The differential charge amplifier is endowed by a dual op amp (IC1) with low supply current and single-supply operation . The input common-mode voltage is set by a small bypass capacitor (C3), R2, R1 at the mid-supply level. The C1 and C2 are used to set AC gain for the differential stage. A gain of C1/CEQ is 96.

The differential amplifier also is used to act as a first-order high-pass filter. The resistors R9, R8, R6, and R5 with IC2 perform differential-to-single-ended conversion. Using the values shown, the different gain is 20. [Circuit Schematic Source: maxim-ic.com]

High Impedance Low Capacitance Buffer/Amplifier Circuit

This is a design circuit for circuits of high impedance low capacitance buffer and high impedance low capacitance amplifier. First figure is a high impedance low capacitance buffer circuits, it uses the 2N446 JFET that features low input capacitance. The feedback buffer a wide-band unity gain amplifier is made from this 2N446 JFET. This is the figure of the circuit;


The second figure is high impedance low capacitance amplifier. This circuit provides high input impedance and stable. This circuit has wide-band gain that is used for general purpose video amplifier applications. The gain of the amplifier is equal to R2/R1. [Source: National Semiconductor Application Note]

FM Tracking Transmitter Circuit Using a 555 Timer

This circuit is designed for tracking transmitter audio tone in FM frequency band. Circuits that can be used the signal transmitter or remote control transmitter. In circuits that use only components that are available. Transmitter’s range is 100 m in the distance using the 9V power supply and matching the antenna. Circuit diagram is built by IC timer 555 to produce audio and tone based on the JFET in the circuit as the core. JFET circuit operation is the first (Q1) is the cable as a Hartley oscillator frequency modulated by the audio tone. The second (Q2) JFET is wired as a buffer to isolate the oscillator from the antenna based on the Q1. Diode D1 is used as varactors. This is the figure of the circuit.


The diode is reverse bias voltage generated by slim on pin 2 & 6 of IC1 results. This change in capacitance of the junction diode reverse bias, which in turn change the frequency of the oscillator to achieve frequency modulation. For inductor L1 can be made by winding 5 turns of 18 SWG enameled copper wire on 3 / 8 inches long, 3 / 16 inch diameter plastic tube. The coil must be tapped in the center. The antenna can be a 20cm long wire.