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SG new PWM IC suits motor driving apps

Posted: 03 Sep 2004 ?? ?Print Version ?Bookmark and Share

Keywords:system general? sg? pwm ic? sg6846?

System General Corp. (SG) announced a new addition to its Green Mode PWM IC seriesthe SG6846. This new chip comes with an ac input brownout protection, a two-level overcurrent protection (OCP), latch circuits for protection functions such as OCP, overtemperature protection (OTP), and overvoltage protection (OVP).

According to the company, the product's features make it an ideal solution for motor driving applications that need switching mode power supplies with surge-current output.

Incorporated with a two-level OCP function, the SG6846 provides excellent protection from over current. On level one, the device provides cycle-by-cycle current limiting with line compensation to ensure a constant output current. On level two, when the switching current becomes higher than two thirds of the peak-current threshold for longer than 96ms, the overcurrent protection activates causing the SG6846 to shut down.

Additionally, the AC input brownout protection with hysteresis ensures safe operation during line disturbances. PWM output is disabled as long as VDD voltage exceeds 23.6V, and the gate output is clamped at 18V to protect the power MOS from overvoltage damage.

An external NTC thermistor can be applied to sense the ambient temperature for overtemperature protection. When OTP, OCP or VDD over voltage faults are detected, an internal latch circuit is used to latch-off the controller. The latch resets only when the ac plug is removed.

Manufactured using the BiCMOS process, the SG6846's start-up current can be reduced to 8?A, and the operating current can be reduced to 3.7mA. A higher start-up resistance can be used to improve power saving. And to further minimize standby power consumption, a patented off-time modulation technology continuously decreases the switching frequency under light-load conditions. Under zero-load conditions, the power supply enters burst-mode. This green-mode function enables the power supply to easily meet international power conservation requirements, said SG.

The SG6846 is housed in two 8-pin DIP-8 and SOP-8 packages. Lead-free packages are also available.

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