SA4828

The SA4828 PWM engine has been designed to provide waveforms for the control of variable speed AC induction motors, static and uninterruptible power supplies and other forms of electronic equipment which require precise power waveform generation.The six digital PWM outputs control the six power semiconductors in a three phase inverter bridge, usually via an external isolated gate driver stage.

Features of the SA4828N are:(1)fully digital operation; (2)configurable microprocessor interface; (3)power frequency range up to 4kHz; (4)16-bit speed control resolution; (5)carrier frequency selectable up to 24kHz; (6)three selectable power waveforms held in internal ROM; (7)selectable minimum pulse width and underlap time; (8)separate amplitude registers for unbalanced load compensation; (9)deadbanding technique to reduce losses in power semiconductors; (10)watchdog timer; (11)boot-strapped driver precharge.Information contained within the PWM sequences controls the wave shape, frequency, direction and amplitude of the output waveform and also the phase relationship between each of the outputs. Parameters such as the carrier (switching) frequency, pulse underlap and pulse deletion times may be defined during initialisation of the device to allow the SA4828 to be used with all power semiconductors, irrespective of switching times. The carrier frequency may be selected up to 24kHz to allow silent ultrasonic operation.

The absolute maximum ratings of the SA4828 can be summarized as:(1)supply voltage:7V;(2)storage temperature:-55 to +150;(3)operating temperature(industrail):-40 to +85 ;(4)voltage on any pin:Vss-0.5V to Vdd+0.5V.Stresses above those listed in the Absolute Maximum Ratings may cause permanent damage to the device.These are stress ratings only and functional operation of the devices at these conditions, or at any other condition above those indicated in the operations section of this specification, is not implied.Exposure to Absolute Maximum Ratings conditions for extended periods may affect device reliability. In general, a pulse width modulation signal is derived by comparing a signal waveform (in this case the power waveform)with a saw-tooth or triangular carrier waveform of significantly higher frequency. The intersections between the two waveforms in the time domain define the location of transitions in the digital output train and hence the width of the output pulses.The width of the pulses are directly proportional to the magnitude of the power waveform, thus the larger the magnitude, the longer the'ON' pulse.