3 Description. The UCA/A series of pulse width modulator integrated circuits are designed to offer improved performance and lowered external parts. SG – SG Regulating Pulse Width Modulator IC Datasheet – Buy SG Technical Information – STMicroelectronics SG Datasheet. IC. Collector Leakage. VC = 35 V. µA tr*. Rise Time. CL = 1 nF, Tj = 25 ° C. ns tf*. Fall Time. CL = 1 nF, Tj = 25 °C.

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The discharge resistor, Rd is discussed later. Who We Are Management.

Product is in volume production Evaluation: These functions are also controlled by an undervoltage lockout which keeps the outputs off and the soft-start capacitor discharged for sub-normal input voltages.

The extra conductance causes the capacitor to discharge faster than it rises, prematurely ending the pulse a little before the opposite pulse begins. The SGA series of pulse width modulator integrated circuits are designed to offer improved performance and lowered external parts count when used in designing all types of switching power supplies. Product is in volume production only to support customers ongoing production.

The output voltage comes from a supply separate from the internal chip logic, so you can interface the PWM sections with low-voltage logic while switching a much higher voltage. Computers and Peripherals Datasheeet Center. You can operate the UC logic from a high voltage input, 35 volts for example, while switching a lower voltage more appropriate for the FETs.

The output stages are totem-pole designs capable of sourcing or sinking in excess of mA. Some have a small section detailing how the “Shutdown” pin can be used to skip a pulse when needed, but others don’t even have that.


If you don’t need to synchronize multiple units, just leave the nSync and OscOut pins unconnected.

Using the UC pulse width modulator | Details |

For example, a 12V power supply might have an error voltage proportional to the difference between 12 volts and the actual output. Programmable Dead time A “totem pole” output can have problem with synchronous control pulses. As far as I can tell, no one has ever used this feature. The Sg35225 chip is basically a triangle wave generator and comparator, with some extras thrown in for convenience.

The UC supplies a precision 5.

Using the UC3525 pulse width modulator

No availability reported, please contact our Sales office. This makes it easy to convert error signals – the positive input can level shift, while the inverting input and feedback can amplify the error to bring it into range.

Soft start and low voltage The UC has a couple of other features which are straightforward to use. if

No commitment taken to produce Proposal: Putting it all together With all these features there’s a lot going on in this one chip, but it’s mostly passives programming the individual sections.

Pulse width modulators are common. Tahmid’s blog has a pin-by-pin functional description with a demonstration circuit, and the SGx App Note describes a related chip, but with important differences. The oscillator has a pulse output that datawheet be used to measure the generated frequency, and an input for synchronizing multiple devices.

For other circuits, simply generate 5. Triangle wave oscillator So a natural question to ask is: The power transistors don’t turn off instantly when their controlling pulse goes low, so if the falling and sg355 edges of the control pulses are close enough, there’s a brief time when both transistors are conducting. The rise time of the oscillator is determined by Rt, but the fall time is determined by the sum of Rt and Rd.


Once a PWM pulses has been terminated for any reason,the outputs will remain off for the duration of the period. Communications Equipment, Computers and Peripherals.

datashheet Adjusting the reference adjusts the pulse width. Clock pulses on a slave nSync prematurely cycle the oscillator flip-flop – causing the peaks and troughs to synchronize with the master. Buy Direct Add to cart. A single resistor between the C T and the discharge terminals provide a wide range of dead time ad- justment.

The output will be high when the triangle is higher than the reference and low everywhere else. Distributor Name Region Stock Min.

ST Microelectronics

Output drivers The UC output is itself a totem-pole: Yes, delete it Cancel. If you don’t need dead time, short the “Discharge” pin directly to Ct, making Rd effectively zero. Where to get chips Pulse width modulators are common. Any properly-scaled voltage proportional to output error can be used as a reference voltage to the comparator. If you want a 50Hz output, configure the oscillator to run at Hz. Support Center Video Center. The UC logic operates anywhere from 8 to 35 volts.

In the circuit below, the PWM error adjustment is delayed by the RC constant of the amplifier feedback. Sign up Already a member? To run a DC motor at a specific speed, simply feed back a voltage proportional to the difference between the requested speed and the actual speed: Usually this ends up burning out your vary-expensive output transistors. Product is in design feasibility stage.