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Synchrononus step down DC-DC integrated with NMOS LDO

The new XCM519 multi chip module from Torex Semiconductor integrates an XC9235/XC9236 synchronous step down DC-DC converter with a high performance XC6601 NMOS LDO (low dropout) voltage regulator.

The module meets the requirements of battery driven applications such as mobile phones, PDAs, gaming devices and Bluetooth equipment, with the DC-DC converter said to provide a step down from the battery. This lower voltage feeds the NMOS LDO to provide a stable, low noise supply for the equipment's on board processor's core.
The DC-DC converter block operates from a supply voltage range between 2.7 and 6V, providing output voltages between 0.8 and 4V and output currents up to 600mA. The switching frequency can be selected from 1.2 or 3MHz as required. The XCM519 is available in two versions to provide PWM control or automatic PWM/PFM switching control, providing fast response, low ripple and high efficiency (92% typ) over the full load range.
The LDO regulator block operates from a bias voltage range of between 2.5 and 6V and an input voltage of between 1 and 3V, providing output voltages between 0.7 and 1.8V to an accuracy of ±20mV. Using an NMOS transistor driver instead of the more usual PMOS means the regulator has a much lower dropout voltage (35mV at 100mA), enabling the device to be used at lower input voltages. Load currents of up to 400mA can be achieved. Over current protection and thermal shutdown circuits are included to protect the regulator against excess current draw or over-temperature.
Each block of the XCM519 includes a built in under voltage lock out function and both blocks feature standby operating modes said to reduce power consumption. The XCM519 is available in a USP-12B01 (2.8 x 2.3 x 0.6mm) package and requires the minimum number of components to build the complete power management circuit.

Author
Chris Shaw

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