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Power manager features USB on-the-go

Posted: 15 Sep 2008     Print Version  Bookmark and Share

Keywords:power management ICs  switching regulator  over-voltage protection  USB on-the-go 

Linear Technology Corp. has released the LTC3576, the newest member in a family of multi-function power management ICs for Li-Ion/Polymer battery-based applications including HDD-based media players, digital cameras, personal navigation devices, PDAs, smart phones and automotive-compatible portable electronics. The LTC3576 features a bi-directional switching power manager with input over-voltage protection and USB on-the-go (OTG) functionality, a stand-alone battery charger, three high efficiency synchronous buck regulators, an ideal diode, I2C control, an always-on LDO, all in a compact, low-profile 4mm x 6mm QFN package.

The LTC3576's USB-compatible bi-directional switching regulator features programmable input current limits of 100mA and 500mA, as well as a 1A wall adapter input current limit. For fast charging, the LTC3576 converts nearly all of the 2.5W available from the USB port to charging current, enabling up to 700mA from a 500mA limited USB supply and up to 1.5A from a wall adapter. The bidirectional switching regulator can also take power from the battery to generate 5V and deliver up to 500mA for USB OTG applications without any additional components. The IC provides an over-voltage protection (OVP) control circuit that prevents damage to its input from the accidental application of voltages as high as 66V. The OVP circuit can protect the USB port even when the IC is providing power for USB OTG.

The LTC3576's PowerPath control with automatic load prioritisation seamlessly manages power flow between a variety of input power sources such as a wall adapter or USB port and the Li-Ion/Polymer battery while preferentially providing power to the system load. The IC's "instant-ON" operation ensures system load power even with a discharged battery. An internal 180mOhm ideal diode plus optional external ideal diode controller provide a low loss power path from the battery to the load when input power is limited or unavailable..

The new product provides Bat-Track control of a companion Linear Technology switching regulator for efficient charging from high voltage inputs while minimising heat dissipation and providing a seamless transition between USB and the higher voltage power source. The LTC3576's stand-alone battery charger features autonomous operation that simplifies design and eliminates the need for an external microprocessor for charge termination. To preserve battery energy, the LTC3576 draws <30uA from the battery in suspend mode.

The device's three integrated synchronous buck regulators feature 100 per cent duty cycle operation and are capable of delivering output currents of 1A/400mA/400mA, respectively, with adjustable output voltages down to 0.8V. The internal low RDS(ON) switches enable efficiency as high as 94 per cent, maximising battery run time. In addition, Burst Mode operation optimises efficiency at light loads with a quiescent current of only 20uA per regulator (<1uA in shutdown). The high 2.25MHz switching frequency allows the use of tiny low cost capacitors and inductors less than 1mm in height. Furthermore, the regulators are stable with ceramic output capacitors, achieving very low output voltage ripple.

The LTC3576 is available from stock in a compact, low-profile (0.75mm) 4mm x 6mm 38-lead QFN package. Pricing starts at Rs.205.72 ($4.80) each for 1,000-piece quantities.

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