Torex Semiconductor has introduced the XD9704 and XD9705 series of synchronous step-down DC/DC converters for automotive and industrial power supplies. Rated for inputs up to 36 V and loads up to 600 mA, the new converters are AEC-Q100 Grade 1 compliant and specified for operation from -40°C to +125°C.
The two series share the same basic power architecture, but use different switching control methods. The XD9704 runs in fixed F-PWM mode, while the XD9705 switches automatically between PWM and PFM according to load conditions.
100% Duty Cycle for Automotive Power Rails
One of the more notable details is Torex's choice of an integrated P-channel driver FET. It allows the XD9704 and XD9705 to operate at 100% duty cycle, which matters when there is very little headroom between the input and required output voltage. If the supply falls below the set output voltage during engine cranking, the converter can pass the available input directly to the output. At the other end of the input range, both series accept up to 36 V continuously and tolerate a 46 V peak for as long as 400 ms.
Torex has paired this voltage range with a 2.2 MHz switching frequency. Smaller inductors and capacitors can therefore be used around the converter, with the company's reference layout occupying 48.7 mm².
Light-load consumption has also been kept low. Quiescent current is 11 µA, and Torex reports 90% efficiency with a 12 V input, 5 V output and 1 mA load.
Two Approaches to Switching Control
The choice between XD9704 and XD9705 comes down largely to how the converter behaves across its load range. XD9704 remains in fixed F-PWM operation, keeping the switching behaviour consistent where low output ripple is the priority. XD9705 instead moves automatically between PWM and PFM, using PFM at lighter loads to reduce power consumption before returning to PWM as the load increases.
Both include Power Good and soft-start functions, giving designers control over startup and downstream power sequencing.
Torex is initially offering the converters in the 4.5 × 4.6 × 1.6 mm SOT-89-5 package. A considerably smaller 1.8 × 2.0 × 0.6 mm DFN1820-6J option is under development and will include wettable flanks for visual inspection of the solder joint.
The XD9704 and XD9705 are aimed primarily at automotive sensor and communication systems, with Torex also targeting industrial equipment requiring compact, high-voltage DC/DC conversion.
Learn more and read the original announcement at the Torex Semiconductor website.
Technology Overview
A synchronous step-down DC/DC converter reduces a higher DC input voltage to a regulated lower output voltage using switching MOSFETs rather than the dissipative regulation used by an LDO. The XD9704 and XD9705 add 36 V input capability and 100% duty-cycle operation for automotive and industrial power rails.
Frequently Asked Questions
What is the difference between the Torex XD9704 and XD9705?
The XD9704 uses fixed F-PWM control for consistently low output ripple. The XD9705 automatically switches between PWM and PFM control to improve efficiency under light-load conditions.
What input voltage can the XD9704 and XD9705 handle?
Both series support input voltages up to 36 V and can withstand a peak input voltage of 46 V for up to 400 ms.
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